Dolioletta gegenbauri
Encyclopedia
Dolioletta gegenbauri is a species of tunicate
in the family
Doliolidae
. It is small, exists in various forms and is sometimes found in great abundance in the Atlantic and Pacific waters where it lives.
with gonad
s, is the most often seen. It is roughly cylindrical with a siphon at both of the flat ends, and has 8 bands of muscle arranged like hoops round a barrel. The U-shaped gut and other organs can be seen through the test which is pierced by 10 to 40 gill slits. The gonozooid ia hermaphrodite and the eggs are fertilised by sperm from another individual. These develop into oozooids which have no reproductive organs. They have 9 bands of muscle and are known as "nurses" as they develop a tail of zooids produced asexually
. Some of these are known as gastrozooids, have a nutritional function and are arranged in lateral rows. Others are phorozooids, have a transport function and are arranged in a single central row. Other zooids link to the phorozooids which then detach themselves from the nurse. The zooids develop into gonozooids and when these are mature they separate from the phorozooids to live independently and start the cycle over again. Meanwhile, the phorozooids have served their purpose and die.
Under the favourable conditions of a plentiful supply of planktonic food, a single oozooid can produce thousands of gonozooids within a few days. Dense swarms sometimes appear in which there are 500 individuals per cubic metre of water.
, the Mediterranean Sea
and the Red Sea
. It is also found in the Pacific Ocean
and is the commonest pelagic
tunicate off the coast of California
.
rate of growth and the quantity of food consumed. The study also aimed to assess their importance in relation to the ecology of planktonic organisms. It sought to quantify grazing
, ingestion rates and growth rates of the gonozooid stage of Dolioletta gegenbauri at various concentrations of the diatom
, Thalassiosira weissflogii
, and the red alga
, Rhodomonas
sp., and at a range of temperatures. It was found that at low to moderate concentrations of the phytoplankton
, growth rates increased exponentially
with concentration and that increases of temperature also increased input and growth. It was concluded that Dolioletta gegenbauri played an important role as consumers of plankton in the neritic zone
on the continental shelf off the United States.
Another study in Japan found that Dolioletta gegenbauri, along with Oikopleura
spp., increased greatly in number in times of algal bloom
s and played an important role as secondary producers.
Tunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...
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...
Doliolidae
Doliolidae
Doliolidae is a family of tunicates in the order Doliolida. Members of the family are pelagic and often found far away from coastlines.Members of the family are transparent, gelatinous, barrel-shaped or cylindrical marine organisms. They are mostly small and inconspicuous...
. It is small, exists in various forms and is sometimes found in great abundance in the Atlantic and Pacific waters where it lives.
Life cycle
Dolioletta gegenbauri is a small, transparent, gelatinous marine invertebrate up to one centimetre long. It has a complex life cycle and exists in several forms of which the gonozooid, or mature zooidZooid
A zooid or zoöid is a single animal that is part of a colonial animal. The zooids can either be directly connected by tissue or share a common exoskeleton...
with gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s, is the most often seen. It is roughly cylindrical with a siphon at both of the flat ends, and has 8 bands of muscle arranged like hoops round a barrel. The U-shaped gut and other organs can be seen through the test which is pierced by 10 to 40 gill slits. The gonozooid ia hermaphrodite and the eggs are fertilised by sperm from another individual. These develop into oozooids which have no reproductive organs. They have 9 bands of muscle and are known as "nurses" as they develop a tail of zooids produced asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
. Some of these are known as gastrozooids, have a nutritional function and are arranged in lateral rows. Others are phorozooids, have a transport function and are arranged in a single central row. Other zooids link to the phorozooids which then detach themselves from the nurse. The zooids develop into gonozooids and when these are mature they separate from the phorozooids to live independently and start the cycle over again. Meanwhile, the phorozooids have served their purpose and die.
Under the favourable conditions of a plentiful supply of planktonic food, a single oozooid can produce thousands of gonozooids within a few days. Dense swarms sometimes appear in which there are 500 individuals per cubic metre of water.
Distribution
Dolioletta gegenbauri is found in temperate areas of the Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
. It is also found in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and is the commonest pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
tunicate off the coast of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
.
Research
Research was undertaken to study the doliolids'Doliolida
Doliolida are small marine animals of the Tunicata phylum, related to salps and pyrosomas. The Doliolid body is small, typically 1–2 cm long, and barrel-shaped; it features two wide siphons, one at the front and the other at the back end, and eight or nine circular muscle strands reminiscent...
rate of growth and the quantity of food consumed. The study also aimed to assess their importance in relation to the ecology of planktonic organisms. It sought to quantify grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
, ingestion rates and growth rates of the gonozooid stage of Dolioletta gegenbauri at various concentrations of the diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
, Thalassiosira weissflogii
Thalassiosira weissflogii
Thalassiosira weissflogii is a species of centric diatom, a unicellular microalga. It is found in marine environments and also in inland waters in many parts of the world.-Taxonomy:...
, and the red alga
Red algae
The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000–6,000 species of mostly multicellular, marine algae, including many notable seaweeds...
, Rhodomonas
Rhodomonas
Rhodomonas is a genus of algae.It includes the species Rhodomonas salina....
sp., and at a range of temperatures. It was found that at low to moderate concentrations of the phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
, growth rates increased exponentially
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
with concentration and that increases of temperature also increased input and growth. It was concluded that Dolioletta gegenbauri played an important role as consumers of plankton in the neritic zone
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
on the continental shelf off the United States.
Another study in Japan found that Dolioletta gegenbauri, along with Oikopleura
Oikopleura
Oikopleura is a genus of Tunicata in the class Appendicularia. It forms a mucus house every four hours at 20 degrees Celsius...
spp., increased greatly in number in times of algal bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...
s and played an important role as secondary producers.