Fiona pinnata
Encyclopedia
Fiona pinnata, common name Fiona, is a species
of small pelagic sea slug
, specifically a nudibranch
, a marine
gastropod mollusk in the superfamily Fionoidea
. This nudibranch species lives worldwide on floating objects on seas, and feeds mainly on barnacle
s, specifically goose barnacles in the genus Lepas
.
The anatomy of this species is very unusual; it does not appear to have any living close relatives. It is the only member of the genus
Fiona (the genus is thus monotypic
), and the genus Fiona is in turn the only genus in the family
Fionidae (a monotypic family). Features that are unique to the family Fionidae, including Fiona pinnata, include:
The type locality is the island location of Sitka, Alaska (Baranof Island
), on the extreme northwestern coast of North America.
from 1775 was preoccupied by one created by Johan Ernst Gunnerus
in 1770. Harold John Finlay
proposed a new genus Dolicheolis for one of those synonyms Eolidia longicauda in 1927.
The cerata
are numerous, elongated, with a membranous fringe on the inner sides. Cerata may seem to be without apparent order but they are set in oblique rows containing from four to six cerata. There are also small cerata near the margins of the body. Cerata on the sides of the back are dark brown, each margined with white. The cerata have no cnidosacs. They are particularly compressed towards the base.
Fiona pinnata has no eyes.
The rhinophore
s are simple and resemble the oral tentacles. They are distant, subulate, tapering and they project outward. They are not retractile, and are without pockets.
The oral tentacles are shorter, thickened at the base, tapering, projecting laterally and horizontally and curved backward. The mouth is situated on the inferior surface of the head. The mouth is small and the external lip is divided behind on the median line.
The anus is between the cerata on the right side of the body, and its opening is directing dorsally. The genital opening is separate.
Joshua Alder
and Albany Hancock
(1851) described the tissues of Fiona pinnata as being very tough and firm.
: The channel leading from mouth to the buccal mass is very short and constricted; and, just before it opens into the buccal mass, it receives on either side below, a very slender duct from a large, much folliculated, salivary gland
. These glands lie beneath the stomach and extend almost half-way down the body. That on the right side is considerably less than the other, and is somewhat tubular, — distinctly so towards its termination; the one on the left side is much complicated in form, being irregularly and extensively sacculated. The position of these glands is unusual, but there are also other species like Doto fragilis, that open into the channel of the mouth in advance of the buccal mass.
The buccal mass is small, rather long, slender, and irregularly elliptical. There are two corneous plates or jaws. at the sides of the buccal mass. It is slightly prolonged behind for the reception of the posterior portion of the radula
, and there are muscles are arranged around. Muscles are from dorsal view extensively developed, forming a dense mass, the fibres passing transversely and have their extremities inserted into the dorsal margins of the jaws. These muscles assist in the motion of the jaws. Muscles for moving the whole buccal mass forward are composed of flattened and isolated bands with their extremities attached to the posterior margin of the jaws and to the muscles forming the walls of the channel of the mouth.
Fiona pinnata has two corneous jaws (mandibles), with a denticulate cutting-edge. The posterior portion is flattened. The corneous plates are little short of the size of the buccal mass, and much elongated, well arched and ovate. (When they are entirely isolated, they strongly resemble the shape the valves of a small bivalve of the genus Mytilus
). They are smooth, glossy, and of a brownish amber colour, darkest towards the anterior extremity, which gives support to the cutting blade. This is a winglike appendage of no great size, terminating below in a free point, and having the cutting margin arched forward, plain, and nearly at right angles to the general direction of the plate. Above is a small process or fulcrum — the point at which the two plates are articulated. Immediately behind this point there is the dorsal margin of the plates is reflected and expanded into an arched lobe for muscular attachment. The length of the jaw is 2.8 mm. The maximum width and maximum height of the jaw is 1.3 mm.
The radula
is supported on a fleshy ridge that rises up from the floor of the buccal cavity, and extends in the antero-posterior direction from the oesophagus towards the anterior opening. The radula is long, linear, and strap-formed, and is composed of semicircular and crescent-shaped denticles (tiny teeth) of an orange colour. There are 40 rows of teeth in radula: 15 oldest denticles in the anterior end, then there are 22 denticles after the angle and three incomplete denticles in the sheath in the posterior end of the radula. The radula formula is 0+1+0, which means that there is only a single central denticle in each row. There is a pointed spine in the centre, and 6 or 6-7 smaller spines on each side of the denticle. There are also sometimes minute spines at the base of denticle's outer margin. All the spines are a little bent, and have their points directed backwards towards the oesophageal opening. The whole length of the radula is 2.6 mm.
The oesophagus is a short and rather slender tube. It leads from the upper part of the buccal mass towards, and opens into, the anterior margin of a distinct pyriform stomach
. The stomach has the broad end forward, is placed above the reproductive system, and lies quite in the anterior portion of the visceral cavity. The internal surface of the stomach is not lamellated. The intestine
leads from posterior end of the stomach, and is inclining slightly to the right side and passes backwards to the tubular anus
. The anus is placed a little to the right of the median line of the back, immediately behind the heart. The intestinal tube is rather short, of equal diameter throughout, and internally plicated longitudinally.
The hepatic apparatus is very peculiar in this animal. The caudal end of the stomach receives two biliary ducts, one on each side of the intestine. These ducts or hepatic canals are nearly as wide as the intestine, and they are diverging as they leave the stomach, very shortly pass into the skin at
the sides of the back, where each opens into a wide channel that extends nearly the whole length of the body. The channels receive numerous branches, which communicate with the glands of the cerata, and as they approach the lateral expansion at the side of the body. These channels are subdivided several times and are irregularly disposed. The anterior portions of the great hepatic channels are connected with two folliculated glandular bodies
much and irregularly sacculated. These glands are united to the skin, one on each side near the region of the stomach, and probably form the inner walls of those portions of the channels. Hepatic canals are almost entirely within the skin. The hepatic glands are large, nearly filling the cerata. They are slightly and irregularly sacculated, with the inner surface of the investing membrane lined with a dark granular substance; above, this substance is very abundant, forming a dense mass; below, the membrane in some of the cerata is entirely devoid of it.
In the central part of the caudal end of the body, behind the ovary, there is likewise a glandular substance, of a reddish colour, folliculated and apparently branched, in connexion with the branches of the hepatic canals within the skin. These branches at the posterior portion of the body probably form a sort of network of tubes across the dorsal aspect. Such perhaps may be inferred from the appearance the branches present when the skin of the back is divided down the median line. See also MacFarland (1966, page 357).
: There are two genital openings on the right side of the head behind the oral tentacle: the opening for the penis and for the (hermaphroditic) genital pore. The reproductive system and the mucous gland is the same as in the genus Aeolidia
. The only difference is that there is a distinct vas deferens in Fiona pinnata.
On laying open the dorsal skin, the reproductive organs are found, as usual, to occupy much of the visceral cavity, having the stomach and intestine lying above, and the buccal mass in front. The penis is placed in advance of the other parts, and, in its retracted state, is long, rather slender,
and linear. The penis has a conical form during mating. The outer extremity of the penis leads through the wall of the visceral cavity to the external opening, and on its way the sheath or external covering of the penis becomes firmly attached to the muscles of the skin.
The ovotestis
(hermaphordite gland) is yellow with white dots. The ovotestis fills the posterior portion of the visceral cavity, and is composed of large irregular lobules made up almost entirely of eggs, and packed into a dense mass, tapering a little behind and truncated in front.
The testis is a stout flesh-coloured tube, two or three times convoluted. It tapers at one extremity into a long slender duct or vas deferens, which is united to the inner extremity of the penis. The other extremity of the testis suddenly contracts into an equally slender duct, but very much shorter, and is joined by this duct to the oviduct.
The spermoviduct leaves the anterior border of the ovary as a slender tube, but, almost immediately dilating, equals the diameter of the testis. This dilated portion of the spermoviduct rests between the lobes of the mucus- gland, and is at first somewhat sacculated and convoluted. Spermoviduct then passes forward and suddenly contracts to its original diameter, and then advances to the anterior border of the mucus-gland and receives the duct from the testis as before described. It then bends a little backward and is shortly joined by a duct from the spermatheca. Spermatheca is a small oval membranous sac, lying between the lobes and at the front margin of the mucus-gland. The duct, which is short and slender, passes from one end of the sac, and, at the point where the duct is united to the oviduct, it is joined by a tube which comes from the external orifice immediately within the female opening. This tube is the vagina or copulatory channel, and is cemented to the upper wall of the female channel. Just before the vagina reaches the duct of the spermatheca and oviduct, it gives off a branch which sinks into the female channel, and so far may be looked upon as a portion of the oviduct, for it is by this branch that the eggs find their way to the female outlet.
The mucus-gland for the secretion of the mucus-like envelope of the eggs, is composed of two lateral lobes separated on the upper surface by a deep fissure. These lobes are semipellucid and are formed of a coarsely convoluted tube, that is on its right side anterior portion opake and flesh-
coloured. The two lobes open into the female channel, which is wide and quite long.
and respiratory system
is unique in this animal, because nearly the whole of these vessels are distinctly visible on the skin of the back, rising above the general surface. The heart
is situated about in the middle of the back, where it forms a large oval swelling immediately below the skin, having the generative organs beneath. From the posterior end of the heart there a broad elevated but rounded ridge passes down the median line of the back to the caudal end of the body. This ridge is joined on either side by numerous similarly elevated branches, which divide and subdivide as they approach the pallial-like expansion on the sides of the body. The whole of these branches and their subdivisions, standing boldly up from the general surface of the skin, have the branchial cerata set along them, and they give off twigs, which pass up the margin of the broad, flounced, membranous expansion of the cerata.
On opening the heart from above, the ventricle
and auricle are found to occupy a well-defined oval pericardium
. The ventricle is large and muscular, of an irregular elliptical form, giving off the aorta in front, which in the usual manner supplies branches to the various organs. The auricle is united to it behind, a little on the left side. The auricle is delicate in comparison with the ventricle, but is nevertheless abundantly supplied with muscular fibres; it lies diagonally in the pericardium, having the left side advanced almost to the front of that organ where it receives a trunk-vein from the skin. The right side of the auricle stretches backward, and receives a similar trunk-vein from the skin of this side almost at the posterior extremity of the pericardium.
On laying the dorsal wall of the auricle open, its cavity is found to be continuous with that of the great posterior elevated median ridge or trunk vein before alluded to, and on opening this trunk-vein the various lateral branches are observed debouching into it on either side. It is therefore evident that this trunk-vein, which lies entirely within the skin, is the great posterior afferent or branchio-cardiac vein, and that all the elevated
branches coming to it from the cerata are also afferent vessels. This way are cerata used for breathing as a specialized breathing organ.
The oxygenated blood from the heart leads to the aorta, to sinuses where it oxygenates tissues. Deoxygenated blood goes to efferent branchial vessels in cerata. These efferent vessels can be seen in a transverse section of the cerata as widish canal to pass up the opposite margin. From efferent vessels the blood goes into afferent vessel, where is gets an oxygen. Dorsal skin also partly serves as a breathing organ.
: The renal pore is between heart and anus.
: The cerebral ganglia are placed at the commencement of the oesophagus. There are as usual four pairs of supra-oesophageal ganglia, though at first sight only three are apparent. The cerebroid and branchial are completely fused. Branchial ganglia form two oval central masses, resting upon the upper surface of the oesophagus, one on each side of the median line, across which they are united at the anterior extremity by a short but distinct commissure. Their posterior extremities diverge and are slightly bilobed, marking the boundaries of the two ganglia of which each mass is composed, — the anterior lobe indicating the cerebroid, the posterior the branchial. (Branchial ganglia are also fused in Onchidoris bilamellata
and in Lamellidoris aspera.) The pedial ganglions are irregularly rounded, being equal in bulk to the cerebroid and branchial together. They lie against the sides of the oesophagus, and are united to the under surface of the central masses. The fourth pair of ganglions
are the olfactory: they are well developed, though very much smaller than those just described, and are joined by a short commissure to the upper surface of the anterior margins of the cerebroid ganglions.
The infra-oesophageal ganglions are placed in the usual situation on the buccal mass, below the oesophagus. The buccal ganglions are scarcely larger than the olfactory, and are of an oval form, their inner extremities being connected across the median line by a short commissure; their outer extremities receive a cord of communication from each of the cerebroid ganglions. Two minute elliptical ganglions are almost sessile on the anterior
border of the buccal ganglions; these are the gastro-cesophageal ganglions. Thus in all there are six pairs of ganglions; four above the gullet, and two below it.
The first pair of nerves come from the olfactory ganglions, and are large, but of no great length; they divide into several filaments as they enter the base of the dorsal tentacles. The second pair pass from the under surface of the anterior border of the cerebroid ganglions, not far from their union with the olfactory ganglions; these nerves go to supply the upper surface of the channel of the mouth. The third and fourth pairs of nerves issue from the same ganglions, but considerably behind the second pair; these also go to the channel of the mouth; the third probably sending a branch to the oral tentacles. A strong cord passes off close to the root of the fourth pair: these cords curve round the oesophagus and are united to the outer extremities of the buccal ganglions, forming the anterior collar. The fifth pair of nerves issue apparently from the outer border of the branchial ganglia, and go to the skin by the side of the head. The sixth pair are small, and come from the upper surface of the branchial ganglions; these nerves go to the skin of the sides of the back. The seventh, much larger than the sixth, emerge from the posterior margin of the same ganglions, and supply the dorsal skin, and apparently likewise the cerata. These are the branchial nerves. The eighth and ninth pairs are large nerves; they issue from the outer border of the pedial ganglions and go to the foot. The posterior margins of these ganglions are united by a stout, shortish commissure, composed of two or three cords, which, passing below the gullet, form the great oesophageal collar. The tenth pair of nerves are given off from the posterior margin of the buccal ganglions; these pass into the buccal mass and go to supply the tongue. The eleventh pair, issuing from the outer extremities of the buccal ganglions, are distributed to the muscles of the buccal mass. The twelfth pair come from the apex of the gastro-oesophageal ganglions, and
being applied to the gullet, each divides into two branches, one of which supplies the upper portion of that tube, the other, passing down it, goes to the stomach as in the other nudibranch
s. The thirteenth pair are large; these are the hepatic nerves; they issue from the buccal mass and probably (as in genus Aeolidia
) are connected at their origin with ganglions, which must be looked upon as belonging to the sympathetic system. Immediately on emerging from the buccal mass, they are connected to the buccal ganglions at their point of union with the gastrooesophageal, and then, arching outwards and upwards, pass from within the anterior oesophageal collar, and go to supply the glands of the cerata.
Other nerve include the "genital nerve" a single nerve given off from a delicate collar, the ends of which are united to the under-surface of the central masses, just where they are connected to the pedial ganglions. Another nerve, which was apparently also distributed to the genitalia; this seemed to come from the right branchial ganglion, at its union with the pedial. These two nerves are poobably leading from visceral ganglia.
. Unlike some other pelagic animals, this species cannot swim or even float in water by itself, thus although it is pelagic, it is not considered to be planktonic.
Fiona pinnata has even been found on both adult and juvenile Loggerhead Sea Turtle
s from the Canary Islands.
s of the genus Lepas
: gooseneck barnacle
Lepas anatifera, Lepas anserifera
, Lepas fascicularis, Lepas hilli, and Lepas testudinata, which grow on floating debris. It can attack other barnacles, but only damaged ones: Pollicipes polymerus and Balanus glandula
. It can also eat barnacles on the genus Alepas (see also Beeman & Williams 1980) and cnidarians Velella velella and Porpita porpita
. Some authors have noted that Fiona pinnata does not feed on the siphonophore Physalia physalis (see also Bayer 1963), but some authors mention Physalia
as its prey.
larva of Fiona pinnata lasts five days. Then it undergoes a metamorphosis
into a slug. The New Zealand malacologist Richard Cardeu Willan (1979) published a theory that the veliger can delay its metamorphosis if it does not find suitable floating habitat to attach itself to.
Fiona pinnata grows very rapidly. It has one of the highest growth rates among all nudibranchs (that is compared with benthic nudibranchs, the only ones for which the growth rates are known). The only species known to grow faster than this is Doridella obscura.
Fiona pinnata can grow from 8 mm to 20 mm in 4 days.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of small pelagic sea slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
, specifically a nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
, a marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod mollusk in the superfamily Fionoidea
Fionoidea
Fionoidea is a superfamily of small sea slugs, aeolid nudibranchs. They are gastropod mollusks within the clade Aeolidida.-Families:Families within the superfamily Fionoidea are as follows:* Family Fionidae Gray, 1857...
. This nudibranch species lives worldwide on floating objects on seas, and feeds mainly on barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s, specifically goose barnacles in the genus Lepas
Lepas
Lepas is a genus of goose barnacles in the family Lepadidae.-Species:Species in the genus include:* Lepas anatifera Linnaeus, 1758* Lepas anserifera Linnaeus, 1767* Lepas australis Darwin, 1851* Lepas hilli Leach, 1818...
.
The anatomy of this species is very unusual; it does not appear to have any living close relatives. It is the only member of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Fiona (the genus is thus monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
), and the genus Fiona is in turn the only genus in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Fionidae (a monotypic family). Features that are unique to the family Fionidae, including Fiona pinnata, include:
- the oral tentacles and rhinophoreRhinophoreA rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...
s look the same - the cerataCerataCerata are anatomical structures found in nudibranch sea slugs, marine opisthobranch gastropod mollusks.They are dorsal and lateral outgrowths on the upper surfaces of the body....
have a membrane, and have no cnidosac - the opening of the anus is directed dorsally
- there are two genital openings of the reproductive systemReproductive system of gastropodsThe reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
- there are two jaws with a cutting-edge
- the radulaRadulaThe radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
looks like a column of single teeth: in each row there is only one central denticle. That one denticle has a central cusp and a few surrounding cusps.
Distribution
Fiona pinnata is found in all seas worldwide, on many different kinds of floating objects.The type locality is the island location of Sitka, Alaska (Baranof Island
Baranof Island
Baranof Island, also sometimes called Baranov Island, Shee or Sitka Island, is an island in the northern Alexander Archipelago in the Alaska Panhandle, in Alaska. The name Baranof was given in 1805 by Imperial Russian Navy captain U. F. Lisianski to honor Alexander Andreyevich Baranov...
), on the extreme northwestern coast of North America.
Taxonomy
Various names have been created for this species. A name by Peter ForsskålPeter Forsskål
Peter Forsskål, sometimes spelled Pehr Forsskål, Peter Forskaol, Petrus Forskål or Pehr Forsskåhl, was a Swedish explorer, orientalist, naturalist and an apostle of Carl Linnaeus.-Early life:...
from 1775 was preoccupied by one created by Johan Ernst Gunnerus
Johan Ernst Gunnerus
Johan Ernst Gunnerus was a Norwegian bishop and botanist. Gunnerus was born at Christiania. He was bishop of the Diocese of Nidaros from 1758 until his death and also a professor of theology at the University of Copenhagen....
in 1770. Harold John Finlay
Harold John Finlay
Harold John Finlay was a New Zealand palaeontologist and conchologist. He was born in Comilla, India , on 22 March 1901....
proposed a new genus Dolicheolis for one of those synonyms Eolidia longicauda in 1927.
Description
The body is elongated and oblong-elliptical. The length of the body is usually about 20 mm, but the largest reported size of the body is 50 mm. Lengths of a species with a total lengthth of 31.7 mm are as follows: 17.7 mm is the body to the tip of cerata, the length of the foot is 14.4 mm, the tail at the end of the foot is 14 mm. The head and body ranges from white to brown or purple depending on its food. The foot is long and lanceolate, rounded in front and produced into a fine point behind. The margin of the foot is thin, fringed and crumpled, except near the head, where it is simple. It is divided in front, but not produced.The cerata
Cerata
Cerata are anatomical structures found in nudibranch sea slugs, marine opisthobranch gastropod mollusks.They are dorsal and lateral outgrowths on the upper surfaces of the body....
are numerous, elongated, with a membranous fringe on the inner sides. Cerata may seem to be without apparent order but they are set in oblique rows containing from four to six cerata. There are also small cerata near the margins of the body. Cerata on the sides of the back are dark brown, each margined with white. The cerata have no cnidosacs. They are particularly compressed towards the base.
Fiona pinnata has no eyes.
The rhinophore
Rhinophore
A rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...
s are simple and resemble the oral tentacles. They are distant, subulate, tapering and they project outward. They are not retractile, and are without pockets.
The oral tentacles are shorter, thickened at the base, tapering, projecting laterally and horizontally and curved backward. The mouth is situated on the inferior surface of the head. The mouth is small and the external lip is divided behind on the median line.
The anus is between the cerata on the right side of the body, and its opening is directing dorsally. The genital opening is separate.
Joshua Alder
Joshua Alder
Joshua Alder , was a British zoologist and a malacologist. He specialized in the Tunicata, and in gastropods.- Bibliography :* Alder J. . "Supplement to a catalogue of the land and fresh-water testaceous Mollusca, found in the vicinity of Newcastle". Transactions of the Natural History Society of...
and Albany Hancock
Albany Hancock
Albany Hancock , naturalist, biologist and supporter of Charles Darwin, was born on Christmas Eve in Newcastle upon Tyne. He is best-known for his works on marine animals and coal-measure fossils....
(1851) described the tissues of Fiona pinnata as being very tough and firm.
Digestive system
Digestive systemDigestive system of gastropods
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods as the largest taxonomic class of the mollusca are very diverse indeed: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.In particular, the...
: The channel leading from mouth to the buccal mass is very short and constricted; and, just before it opens into the buccal mass, it receives on either side below, a very slender duct from a large, much folliculated, salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
. These glands lie beneath the stomach and extend almost half-way down the body. That on the right side is considerably less than the other, and is somewhat tubular, — distinctly so towards its termination; the one on the left side is much complicated in form, being irregularly and extensively sacculated. The position of these glands is unusual, but there are also other species like Doto fragilis, that open into the channel of the mouth in advance of the buccal mass.
The buccal mass is small, rather long, slender, and irregularly elliptical. There are two corneous plates or jaws. at the sides of the buccal mass. It is slightly prolonged behind for the reception of the posterior portion of the radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
, and there are muscles are arranged around. Muscles are from dorsal view extensively developed, forming a dense mass, the fibres passing transversely and have their extremities inserted into the dorsal margins of the jaws. These muscles assist in the motion of the jaws. Muscles for moving the whole buccal mass forward are composed of flattened and isolated bands with their extremities attached to the posterior margin of the jaws and to the muscles forming the walls of the channel of the mouth.
Fiona pinnata has two corneous jaws (mandibles), with a denticulate cutting-edge. The posterior portion is flattened. The corneous plates are little short of the size of the buccal mass, and much elongated, well arched and ovate. (When they are entirely isolated, they strongly resemble the shape the valves of a small bivalve of the genus Mytilus
Mytilus
Mytilus was an Illyrian king of the Dardanian Kingdom. Mytilus is probably the son of Monunius.Mytilus is the second Illyrian monarch to have struck in 270 BC coins bearing his name after Monunius...
). They are smooth, glossy, and of a brownish amber colour, darkest towards the anterior extremity, which gives support to the cutting blade. This is a winglike appendage of no great size, terminating below in a free point, and having the cutting margin arched forward, plain, and nearly at right angles to the general direction of the plate. Above is a small process or fulcrum — the point at which the two plates are articulated. Immediately behind this point there is the dorsal margin of the plates is reflected and expanded into an arched lobe for muscular attachment. The length of the jaw is 2.8 mm. The maximum width and maximum height of the jaw is 1.3 mm.
The radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
is supported on a fleshy ridge that rises up from the floor of the buccal cavity, and extends in the antero-posterior direction from the oesophagus towards the anterior opening. The radula is long, linear, and strap-formed, and is composed of semicircular and crescent-shaped denticles (tiny teeth) of an orange colour. There are 40 rows of teeth in radula: 15 oldest denticles in the anterior end, then there are 22 denticles after the angle and three incomplete denticles in the sheath in the posterior end of the radula. The radula formula is 0+1+0, which means that there is only a single central denticle in each row. There is a pointed spine in the centre, and 6 or 6-7 smaller spines on each side of the denticle. There are also sometimes minute spines at the base of denticle's outer margin. All the spines are a little bent, and have their points directed backwards towards the oesophageal opening. The whole length of the radula is 2.6 mm.
The oesophagus is a short and rather slender tube. It leads from the upper part of the buccal mass towards, and opens into, the anterior margin of a distinct pyriform stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. The stomach has the broad end forward, is placed above the reproductive system, and lies quite in the anterior portion of the visceral cavity. The internal surface of the stomach is not lamellated. The intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
leads from posterior end of the stomach, and is inclining slightly to the right side and passes backwards to the tubular anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
. The anus is placed a little to the right of the median line of the back, immediately behind the heart. The intestinal tube is rather short, of equal diameter throughout, and internally plicated longitudinally.
The hepatic apparatus is very peculiar in this animal. The caudal end of the stomach receives two biliary ducts, one on each side of the intestine. These ducts or hepatic canals are nearly as wide as the intestine, and they are diverging as they leave the stomach, very shortly pass into the skin at
the sides of the back, where each opens into a wide channel that extends nearly the whole length of the body. The channels receive numerous branches, which communicate with the glands of the cerata, and as they approach the lateral expansion at the side of the body. These channels are subdivided several times and are irregularly disposed. The anterior portions of the great hepatic channels are connected with two folliculated glandular bodies
much and irregularly sacculated. These glands are united to the skin, one on each side near the region of the stomach, and probably form the inner walls of those portions of the channels. Hepatic canals are almost entirely within the skin. The hepatic glands are large, nearly filling the cerata. They are slightly and irregularly sacculated, with the inner surface of the investing membrane lined with a dark granular substance; above, this substance is very abundant, forming a dense mass; below, the membrane in some of the cerata is entirely devoid of it.
In the central part of the caudal end of the body, behind the ovary, there is likewise a glandular substance, of a reddish colour, folliculated and apparently branched, in connexion with the branches of the hepatic canals within the skin. These branches at the posterior portion of the body probably form a sort of network of tubes across the dorsal aspect. Such perhaps may be inferred from the appearance the branches present when the skin of the back is divided down the median line. See also MacFarland (1966, page 357).
Reproductive system
Reproductive systemReproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
: There are two genital openings on the right side of the head behind the oral tentacle: the opening for the penis and for the (hermaphroditic) genital pore. The reproductive system and the mucous gland is the same as in the genus Aeolidia
Aeolidia
Aeolidia is a genus of sea slugs, aeolid nudibranchs, marine gastropod mollusks in the family Aeolidiidae.-Species:Species within the genus Aeolidia include:* Aeolidia collaris Odhner, 1921* Aeolidia papillosa...
. The only difference is that there is a distinct vas deferens in Fiona pinnata.
On laying open the dorsal skin, the reproductive organs are found, as usual, to occupy much of the visceral cavity, having the stomach and intestine lying above, and the buccal mass in front. The penis is placed in advance of the other parts, and, in its retracted state, is long, rather slender,
and linear. The penis has a conical form during mating. The outer extremity of the penis leads through the wall of the visceral cavity to the external opening, and on its way the sheath or external covering of the penis becomes firmly attached to the muscles of the skin.
The ovotestis
Ovotestis
An ovotestis is a gonad with both testicular and ovarian aspects. In humans, ovotestes are an anatomical abnormality associated with gonadal dysgenesis.- In gastropods :...
(hermaphordite gland) is yellow with white dots. The ovotestis fills the posterior portion of the visceral cavity, and is composed of large irregular lobules made up almost entirely of eggs, and packed into a dense mass, tapering a little behind and truncated in front.
The testis is a stout flesh-coloured tube, two or three times convoluted. It tapers at one extremity into a long slender duct or vas deferens, which is united to the inner extremity of the penis. The other extremity of the testis suddenly contracts into an equally slender duct, but very much shorter, and is joined by this duct to the oviduct.
The spermoviduct leaves the anterior border of the ovary as a slender tube, but, almost immediately dilating, equals the diameter of the testis. This dilated portion of the spermoviduct rests between the lobes of the mucus- gland, and is at first somewhat sacculated and convoluted. Spermoviduct then passes forward and suddenly contracts to its original diameter, and then advances to the anterior border of the mucus-gland and receives the duct from the testis as before described. It then bends a little backward and is shortly joined by a duct from the spermatheca. Spermatheca is a small oval membranous sac, lying between the lobes and at the front margin of the mucus-gland. The duct, which is short and slender, passes from one end of the sac, and, at the point where the duct is united to the oviduct, it is joined by a tube which comes from the external orifice immediately within the female opening. This tube is the vagina or copulatory channel, and is cemented to the upper wall of the female channel. Just before the vagina reaches the duct of the spermatheca and oviduct, it gives off a branch which sinks into the female channel, and so far may be looked upon as a portion of the oviduct, for it is by this branch that the eggs find their way to the female outlet.
The mucus-gland for the secretion of the mucus-like envelope of the eggs, is composed of two lateral lobes separated on the upper surface by a deep fissure. These lobes are semipellucid and are formed of a coarsely convoluted tube, that is on its right side anterior portion opake and flesh-
coloured. The two lobes open into the female channel, which is wide and quite long.
Circulatory and respiratory system
The circulatory systemCirculatory system of gastropods
As in other molluscs, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in colour.-Circulation:...
and respiratory system
Respiratory system of gastropods
The respiratory system of gastropods varies greatly in form. These variations were once used as a basis for dividing the group into subclasses. The majority of marine gastropods breathe through a single gill, supplied with oxygen by a current of water through the mantle cavity...
is unique in this animal, because nearly the whole of these vessels are distinctly visible on the skin of the back, rising above the general surface. The heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
is situated about in the middle of the back, where it forms a large oval swelling immediately below the skin, having the generative organs beneath. From the posterior end of the heart there a broad elevated but rounded ridge passes down the median line of the back to the caudal end of the body. This ridge is joined on either side by numerous similarly elevated branches, which divide and subdivide as they approach the pallial-like expansion on the sides of the body. The whole of these branches and their subdivisions, standing boldly up from the general surface of the skin, have the branchial cerata set along them, and they give off twigs, which pass up the margin of the broad, flounced, membranous expansion of the cerata.
On opening the heart from above, the ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
and auricle are found to occupy a well-defined oval pericardium
Pericardium
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...
. The ventricle is large and muscular, of an irregular elliptical form, giving off the aorta in front, which in the usual manner supplies branches to the various organs. The auricle is united to it behind, a little on the left side. The auricle is delicate in comparison with the ventricle, but is nevertheless abundantly supplied with muscular fibres; it lies diagonally in the pericardium, having the left side advanced almost to the front of that organ where it receives a trunk-vein from the skin. The right side of the auricle stretches backward, and receives a similar trunk-vein from the skin of this side almost at the posterior extremity of the pericardium.
On laying the dorsal wall of the auricle open, its cavity is found to be continuous with that of the great posterior elevated median ridge or trunk vein before alluded to, and on opening this trunk-vein the various lateral branches are observed debouching into it on either side. It is therefore evident that this trunk-vein, which lies entirely within the skin, is the great posterior afferent or branchio-cardiac vein, and that all the elevated
branches coming to it from the cerata are also afferent vessels. This way are cerata used for breathing as a specialized breathing organ.
The oxygenated blood from the heart leads to the aorta, to sinuses where it oxygenates tissues. Deoxygenated blood goes to efferent branchial vessels in cerata. These efferent vessels can be seen in a transverse section of the cerata as widish canal to pass up the opposite margin. From efferent vessels the blood goes into afferent vessel, where is gets an oxygen. Dorsal skin also partly serves as a breathing organ.
Excretory system
Excretory systemExcretory system of gastropods
The excretory system of gastropods removes nitrogenous waste and maintains the internal water balance of these creatures, commonly referred to as snails and slugs...
: The renal pore is between heart and anus.
Nervous system
Nervous systemNervous system of gastropods
The nervous system of gastropods consists of a series of paired ganglia connected by major nerve cords, and a number of smaller branching peripheral nerves.The brain of a gastropod consists of three pairs of ganglia, all located close to the oesophagus...
: The cerebral ganglia are placed at the commencement of the oesophagus. There are as usual four pairs of supra-oesophageal ganglia, though at first sight only three are apparent. The cerebroid and branchial are completely fused. Branchial ganglia form two oval central masses, resting upon the upper surface of the oesophagus, one on each side of the median line, across which they are united at the anterior extremity by a short but distinct commissure. Their posterior extremities diverge and are slightly bilobed, marking the boundaries of the two ganglia of which each mass is composed, — the anterior lobe indicating the cerebroid, the posterior the branchial. (Branchial ganglia are also fused in Onchidoris bilamellata
Onchidoris bilamellata
Onchidoris bilamellata, common name the rough-mantled doris, is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Onchidorididae. - Distribution :...
and in Lamellidoris aspera.) The pedial ganglions are irregularly rounded, being equal in bulk to the cerebroid and branchial together. They lie against the sides of the oesophagus, and are united to the under surface of the central masses. The fourth pair of ganglions
are the olfactory: they are well developed, though very much smaller than those just described, and are joined by a short commissure to the upper surface of the anterior margins of the cerebroid ganglions.
The infra-oesophageal ganglions are placed in the usual situation on the buccal mass, below the oesophagus. The buccal ganglions are scarcely larger than the olfactory, and are of an oval form, their inner extremities being connected across the median line by a short commissure; their outer extremities receive a cord of communication from each of the cerebroid ganglions. Two minute elliptical ganglions are almost sessile on the anterior
border of the buccal ganglions; these are the gastro-cesophageal ganglions. Thus in all there are six pairs of ganglions; four above the gullet, and two below it.
The first pair of nerves come from the olfactory ganglions, and are large, but of no great length; they divide into several filaments as they enter the base of the dorsal tentacles. The second pair pass from the under surface of the anterior border of the cerebroid ganglions, not far from their union with the olfactory ganglions; these nerves go to supply the upper surface of the channel of the mouth. The third and fourth pairs of nerves issue from the same ganglions, but considerably behind the second pair; these also go to the channel of the mouth; the third probably sending a branch to the oral tentacles. A strong cord passes off close to the root of the fourth pair: these cords curve round the oesophagus and are united to the outer extremities of the buccal ganglions, forming the anterior collar. The fifth pair of nerves issue apparently from the outer border of the branchial ganglia, and go to the skin by the side of the head. The sixth pair are small, and come from the upper surface of the branchial ganglions; these nerves go to the skin of the sides of the back. The seventh, much larger than the sixth, emerge from the posterior margin of the same ganglions, and supply the dorsal skin, and apparently likewise the cerata. These are the branchial nerves. The eighth and ninth pairs are large nerves; they issue from the outer border of the pedial ganglions and go to the foot. The posterior margins of these ganglions are united by a stout, shortish commissure, composed of two or three cords, which, passing below the gullet, form the great oesophageal collar. The tenth pair of nerves are given off from the posterior margin of the buccal ganglions; these pass into the buccal mass and go to supply the tongue. The eleventh pair, issuing from the outer extremities of the buccal ganglions, are distributed to the muscles of the buccal mass. The twelfth pair come from the apex of the gastro-oesophageal ganglions, and
being applied to the gullet, each divides into two branches, one of which supplies the upper portion of that tube, the other, passing down it, goes to the stomach as in the other nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
s. The thirteenth pair are large; these are the hepatic nerves; they issue from the buccal mass and probably (as in genus Aeolidia
Aeolidia
Aeolidia is a genus of sea slugs, aeolid nudibranchs, marine gastropod mollusks in the family Aeolidiidae.-Species:Species within the genus Aeolidia include:* Aeolidia collaris Odhner, 1921* Aeolidia papillosa...
) are connected at their origin with ganglions, which must be looked upon as belonging to the sympathetic system. Immediately on emerging from the buccal mass, they are connected to the buccal ganglions at their point of union with the gastrooesophageal, and then, arching outwards and upwards, pass from within the anterior oesophageal collar, and go to supply the glands of the cerata.
Other nerve include the "genital nerve" a single nerve given off from a delicate collar, the ends of which are united to the under-surface of the central masses, just where they are connected to the pedial ganglions. Another nerve, which was apparently also distributed to the genitalia; this seemed to come from the right branchial ganglion, at its union with the pedial. These two nerves are poobably leading from visceral ganglia.
Ecology
This nudibranch is pelagic in a similar way to the nudibranch Glaucus atlanticusGlaucus atlanticus
Glaucus atlanticus is a species of small-sized blue sea slug, a pelagic aeolid nudibranch, a marine gastropod mollusk in the family Glaucidae...
. Unlike some other pelagic animals, this species cannot swim or even float in water by itself, thus although it is pelagic, it is not considered to be planktonic.
Fiona pinnata has even been found on both adult and juvenile Loggerhead Sea Turtle
Loggerhead Sea Turtle
The loggerhead sea turtle , or loggerhead, is an oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around long when fully grown, although larger specimens of up to have been discovered...
s from the Canary Islands.
Feeding habits
Fiona pinnata attacks and preys on barnacleBarnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s of the genus Lepas
Lepas
Lepas is a genus of goose barnacles in the family Lepadidae.-Species:Species in the genus include:* Lepas anatifera Linnaeus, 1758* Lepas anserifera Linnaeus, 1767* Lepas australis Darwin, 1851* Lepas hilli Leach, 1818...
: gooseneck barnacle
Gooseneck barnacle
Goose barnacles , also called stalked barnacles or gooseneck barnacles, are filter-feeding crustaceans that live attached to hard surfaces of rocks and flotsam in the ocean intertidal zone.-Biology:...
Lepas anatifera, Lepas anserifera
Lepas anserifera
Lepas anserifera is a species of goose barnacle or stalked barnacle in the family Lepadidae. It lives attached to floating timber, ships' hulls and various sorts of flotsam.-Description:...
, Lepas fascicularis, Lepas hilli, and Lepas testudinata, which grow on floating debris. It can attack other barnacles, but only damaged ones: Pollicipes polymerus and Balanus glandula
Balanus glandula
Balanus glandula is one of the most common barnacle species on the Pacific coast of North America, distributed from the U.S. state of Alaska to Bahía de San Quintín near San Quintín, Baja California. It is commonly found in intertidal waters on mussels, rocks and pier pilings.It is a moderate-sized...
. It can also eat barnacles on the genus Alepas (see also Beeman & Williams 1980) and cnidarians Velella velella and Porpita porpita
Porpita porpita
Porpita porpita, commonly known as the blue button, is a marine organism consisting of a colony of hydroids found in tropical waters from California to the tropical Pacific, the Atlantic and Indian oceans It is often mistaken for a jellyfish, but although jellyfish and the blue buttons are part of...
. Some authors have noted that Fiona pinnata does not feed on the siphonophore Physalia physalis (see also Bayer 1963), but some authors mention Physalia
Physalia
Physalia is a genus of the order Siphonophora, colonies of four specialized polyps and medusoids that drift on the surface of the Indian and Pacific oceans. A gas-filled bladder resembling a blue bottle maintains their buoyancy, and a single long tentacle of venomous cnidocytes provide the animal...
as its prey.
Life cycle
The stadium of the veligerVeliger
A veliger is the planktonic larva of many kinds of marine and freshwater gastropod molluscs, as well as most bivalve mollusks.- Description :...
larva of Fiona pinnata lasts five days. Then it undergoes a metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
into a slug. The New Zealand malacologist Richard Cardeu Willan (1979) published a theory that the veliger can delay its metamorphosis if it does not find suitable floating habitat to attach itself to.
Fiona pinnata grows very rapidly. It has one of the highest growth rates among all nudibranchs (that is compared with benthic nudibranchs, the only ones for which the growth rates are known). The only species known to grow faster than this is Doridella obscura.
Fiona pinnata can grow from 8 mm to 20 mm in 4 days.
Further reading
- Bayer, F. M. (1963). "Observations on pelagic molluscs associated with the siphonophores Velella and Physalia". Bulletin of Marine Science of the Gulf and Caribbean, University of Miami 13(3): 454-466.
- Beeman, R. D. & Williams G. C. (1980). Chapter 14. Opisthobranchia and Pulmonata: the sea slugs and allies. pp. 308–354, pls. 95- 111. In: Robert H. Morris, Donald P. Abbott, & Eugene C. Haderlie. Intertidal invertebrates of California, ix + 690 pp., 200 pls. Stanford University Press. See page 338.
- Bergh, L. S. R.Rudolph BerghRudolph Bergh , full name Ludvig Sophus Rudolph Bergh, was a Danish physician and malacologist. He worked in Copenhagen....
(1859). "Contributions to a monograph of the genus Fiona, Hanc". Copenhagen, pp. 1–20. pls. 1-2. - Bieri, R. (1966). "Feeding preferences and rates of the snail, Ianthina prolongata, the barnacle, Lepas anserifera, the nudibranchs, Glaucus atlanticus and Fiona pinnata, and the food web in the marine neuston". Publications of the Seto Marine Biological Laboratory 14: 161-170, pls. III-IV.
- Burn, R. F. (1966). "Descriptions of Australian Eolidacea (Mollusca: Opisthobranchia). 4. The genera Pleurolidia, Fiona, Learchis, and Cerberilla from Lord Howe Island". Journal of the Malacological Society of Australia (10): 21-34.
- Holleman, J. J. (1972) "Observations on growth, feeding, reproduction, and development in the opisthobranch Fiona pinnata (Eschscholtz)". Veliger 15(2): 142-146.
- Jeffreys, J. G.John Gwyn JeffreysJohn Gwyn Jeffreys was a British conchologist and malacologist.He was born in Swansea into a propertied Welsh family and educated at Swansea Grammar School. He went to London to qualify as a barrister, which he did. His greater passion however was for conchology...
(1869) British conchology: or, an account of the Mollusca which now inhabit the British Isles and the surrounding seas. J. Van Voorst, London. Volume 5, Page 35. Plate 2, figure 2. - Williams, M . N . (1978) Buccal glands of some aeolid nudibranchs (Ultrastructure and histochemistry). Unpubl. MSc thesis, University of Auckland. 96 pp.
External links
- Pelagic snails: the biology of holoplanktonic gastropod mollusks By Carol M. Lalli, Ronald W. Gilmer. via Google books
- Powell A. W. B.Arthur William Baden PowellDr Arthur William Baden Powell CBE was a New Zealand malacologist, naturalist and palaeontologist, a major influence in the study and classification of New Zealand molluscs through much of the twentieth century. He was known to his friends and family by his third name, "Baden".Powell was born at...
, New Zealand Mollusca, William Collins Publishers LtdHarperCollinsHarperCollins is a publishing company owned by News Corporation. It is the combination of the publishers William Collins, Sons and Co Ltd, a British company, and Harper & Row, an American company, itself the result of an earlier merger of Harper & Brothers and Row, Peterson & Company. The worldwide...
, Auckland, New Zealand 1979 ISBN 0-00-216906-1 - Casteel D. B. (April 1904) "Cell Lineage and Early Larval Development of Fiona marina, a Nudibranch Mollusck". Proceedings of the Academy of Natural Sciences of Philadelphia 1(6): 325-405.
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