Triops longicaudatus
Encyclopedia
Triops longicaudatus is a freshwater crustacean
of the order Notostraca
, resembling a miniature horseshoe crab
. It is characterized by an elongated, segmented body, flattened shield-like brownish carapace
covering two thirds of the thorax and two long filaments on the abdomen. Triops refers to its three eyes, and longicaudatus refers to the elongated tail structures. Triops longicaudatus is found in freshwater ponds and pools, often in places where few higher forms of life can exist. Like its relative Triops cancriformis
, the longtail tadpole shrimp is considered a living fossil
because its basic pre-historic morphology has changed little in the last 70 million years, exactly matching their ancient fossils. Triops longicaudatus is one of the oldest animal species still in existence.
, which contains primarily freshwater animals with gill
s on their legs. The class Branchiopoda is divided into the subclasses Sarsostraca, containing fairy shrimp
, and Phyllopoda, containing all other members (cladocera
ns, clam shrimp
s and the tadpole shrimp
). The subclass name, literally meaning leaf-footed, is derived from their flat, leaflike appendages. Notostracans are placed in the infraclass Calamanostraca, which also contains the extinct Kazacharthra
.
. Apart from Triops cancriformis
, it is the only tadpole shrimp species whose individuals display as many as three reproductive strategies: bisexual, unisexual (parthenogenetic
) and hermaphroditic
; see below. Triops cancriformis is easily recognizable by its yellow carapace
with dark spots, whilst T. longicaudatus individuals have a uniform carapace. The species also appeared about 50 million years later, and, as its name suggests, its elongated tail structures are often nearly as long as the rest of the body, which has been recorded to reach 5 cm (2 in) in length.
The head of Triops longicaudatus is typical of crustaceans and consists of five segments, but there is a tendency to reduction of cephalic appendage
s. The trunk is not distinctly divided into thorax
and abdomen
. Most trunk segments bear appendages. Zoologists find it difficult to decide where the thorax stops and the abdomen begins; the debate is seemingly endless. The first 11 trunk segments each bear a single pair of limbs. They are followed by segments that are fused similarly to those of millipede
s, and as a result, each segment bears up to six pairs of limbs. The trunk ends with a region of limbless segments. Some zoologists consider the thorax to consist of the two regions with appendages, and the abdomen the region without appendages. Others believe the region of fused segments to be part of the abdomen. For clarity, this article uses "thorax" to mean the two body regions with limbs.
present, but no cephalothorax
, since no thoracic segment is fused with the head. The terms carapace and cephalothorax are often confused, but should not be. The carapace of crustaceans is a fold of the body wall of the fifth head segment.
The head bears a pair of dorsal
compound eyes that lie close to each other, and are nearly fused together. The compound eyes are generally sessile (not stalked). In addition, there is a naupliar ocellus
in between. The compound eyes are on the surface of the head, but the ocellus is deep within the head. All the eyes, however, are easily visible through the shell covering of the head. A distinct horizontal groove, known as the mandibular groove, marks the division between the anterior three head segments and the posterior two. Posterior to it is the cervical groove, marking the division between the head and the thorax.
On the ventral
side of the head is a lenslike window, admitting light to the naupliar eye, which is aimed both dorsally and ventrally. The first antennae (antennules) are small, slender filaments on the ventral surface of the head, at about the same level as the eyes. The second antennae are similar and lie laterally to the first. They are nonfunctioning. The large, well-developed mandibles
oppose each other across the ventral midline. The opposing surfaces bear strong brownish teeth. As the crustacean periodically opens and closes the mandibles the teeth move apart and close together. Of the usual crustacean head appendages, only the mandibles are well developed. In Triops longicaudatus, the larger second maxillae are absent, only maxillules
being present.
The anterior thorax consists of 11 segments, each bearing a pair of appendages, called thoracopods or pereiopods. None of the thoracopods are modified into maxillipeds for feeding. The posterior thorax consists of 16–25 segments, incompletely separated to form rings. Each ring may consist of as many as six fused segments and bear up to six pairs of appendages (there are 54–66 limbs altogether).
Most of the thoracic appendages resemble each other but the first 11 pairs are best developed. There is a slight tendency to regional specialization and the first pair of legs is unlike the rest. It is an elongated, cheliped-like structure with a sensory function, while all the other appendages aid in feeding, respiration and locomotion. In females, the 11th pair of legs is modified into brood pouches. The many legs posterior to the 11th pair move the spent feeding and respiratory currents away.
) connected to long, multisegmented uropods.
. The anterior appendages (second pair to tenth pair) stir sediments and swirl muddy water into the wide, midventral food groove. The gnathobases (inward-facing lobes at the base of the leg) guide food anteriorly to the mouth. The large flat exopods (outward-facing lobes at the end of the leg) stir and lift the sediments. Fine silt particles and water escape easily, but large, coarse food particles are torn into smaller pieces by the blade-like, inward-facing lobes called endopods at the end of the leg.
in each of these segments. Hemoglobin
is sometimes present in the blood and the crustacean may be pink as a result. The excretory
organs are the paired maxillary gland
s, located on the segment of the second maxilla. The long looped ducts of these glands can be seen in the carapace. The role of the maxillary glands is primarily osmoregulatory
. Nitrogen
, in the form of ammonia
, is lost by diffusion
across the gill
surfaces.
(development from unfertilized eggs) is the most common reproductive strategy. Some populations, however, consist of hermaphrodite
s who fertilize each other. It has been noted that different populations display different strategies or combinations of strategies, and may therefore be considered separate species
or subspecies
in the future.
In females, the eleventh pair of legs is modified into egg sacs, where the eggs are carried for several hours. The eggs are released in batches and have a thick shell and can stand freezing temperatures as well as drought, enabling the population to survive from one season to the next. The eggs have to dry out completely before being submerged in water again in order to successfully hatch; they may remain in a state of diapause
for up to 20 years. These eggs may have helped Triops longicaudatus, as well as other notostracans, to survive the natural disasters that may have killed the dinosaur
s 65 million years ago.
they inhabit. During the dry season (summer and fall), they stay inside the eggs. As the pool fills with rainwater during the winter and spring, they hatch and feed on fairy shrimp
s and other invertebrates. The first larval stage (the metanauplius
) is orange in color. It has a single eye and six legs, and develops through instar
s (growth stages). Each instar ends with shedding
the exoskeleton. The number of segments and appendages increases as Triops grow, and they slowly change to greyish-brown. In approximately eight days, they reach maturity and lay eggs. Adult Triops die as the pools dry up. Triops generally live for about 20–90 days if the pool doesn't dry up.
. It is most active at a temperature of around 20 °C (68 °F), and is usually found scratching the mud at the bottom of pools, searching for benthic
food. Triops collect food particles by straining the water with hairs on their limbs. Loose food particles are collected in a groove running down the underside of the body lengthwise, and held together by a sticky secretion until they are swallowed by their very small (2 mm wide) mouth. The tiny mouth is deep in the underbelly of their body and whilst capable of breaking up a plant root or dead fish, it is incapable of chasing and eating prey larger than itself.
; known to chase very small fry and tadpoles, and oligochaete
worms. In general, they eat anything organic that is smaller than themselves, which may even include their siblings (they are cannibalistic
). In turn, Triops longicaudatus is eaten by frogs and birds.
The species is considered a human ally against the West Nile virus
, as the individuals consume Culex
mosquito larvae. They are used as a biological agent
in Japan, eating weeds in rice paddies
. In Wyoming
, the presence of Triops longicaudatus usually indicates a good chance of the hatching of spadefoot frog
s. Dried eggs of Triops longicaudatus are sold in kits to be raised as aquarium pets, sold under the name of "aquasaurs" or "triops".
It is hypothesis
ed that Triops longicaudatus may continue its trend of longevity as a species and, if humans do not devastate its habitat, the species may survive for another 500 million years.
. In Canada
, it is only found in the provinces of Alberta
and Saskatchewan
. It is widespread throughout the continental United States
, Mexico
and Hawaii
, but not Alaska
. Tadpole shrimps can be found in all parts of South America
the West Indies, and the Pacific Islands
, including Japan
and New Caledonia
. The related European species Triops cancriformis
is an endangered species in the United Kingdom
, and is legally protected under Schedule 5 of the Wildlife and Countryside Act 1981
(as amended).
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
of the order Notostraca
Notostraca
The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic. They have a broad, flat carapace, which conceals the...
, resembling a miniature horseshoe crab
Horseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...
. It is characterized by an elongated, segmented body, flattened shield-like brownish carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
covering two thirds of the thorax and two long filaments on the abdomen. Triops refers to its three eyes, and longicaudatus refers to the elongated tail structures. Triops longicaudatus is found in freshwater ponds and pools, often in places where few higher forms of life can exist. Like its relative Triops cancriformis
Triops cancriformis
Triops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
, the longtail tadpole shrimp is considered a living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...
because its basic pre-historic morphology has changed little in the last 70 million years, exactly matching their ancient fossils. Triops longicaudatus is one of the oldest animal species still in existence.
Classification
Triops longicaudatus is a member of the crustacean class BranchiopodaBranchiopoda
Branchiopoda is a class of crustaceans. It is the sister group to the remaining crustaceans, and comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris...
, which contains primarily freshwater animals with gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s on their legs. The class Branchiopoda is divided into the subclasses Sarsostraca, containing fairy shrimp
Fairy shrimp
Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are also known as fairy shrimp. They are usually long . Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia , and the body lacks a carapace...
, and Phyllopoda, containing all other members (cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
ns, clam shrimp
Clam shrimp
Clam shrimp are a taxon of bivalved branchiopod crustaceans that resemble the unrelated bivalved molluscs. They are extant, and known from the fossil record, from at least the Devonian period and perhaps before...
s and the tadpole shrimp
Notostraca
The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic. They have a broad, flat carapace, which conceals the...
). The subclass name, literally meaning leaf-footed, is derived from their flat, leaflike appendages. Notostracans are placed in the infraclass Calamanostraca, which also contains the extinct Kazacharthra
Kazacharthra
Kazacharthra is an extinct order of branchiopod crustaceans, closely related to the living order Notostraca . Kazacharthrans lived in marshes and ponds in the Upper Triassic of Western China and Mongolia, and in Lower Jurassic Kazakhstan...
.
Structure
Triops longicaudatus is usually greyish-yellow or brown in color, and differs from many other species by the absence of the second maxillaMaxilla (arthropod)
In arthropods, the maxillae are paired structures present on the head as mouthparts in members of the clade Mandibulata, used for tasting and manipulating food. Embryologically, the maxillae are derived from the 4th and 5th segment of the head and the maxillary palps; segmented appendages extending...
. Apart from Triops cancriformis
Triops cancriformis
Triops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
, it is the only tadpole shrimp species whose individuals display as many as three reproductive strategies: bisexual, unisexual (parthenogenetic
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
) and hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
; see below. Triops cancriformis is easily recognizable by its yellow carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
with dark spots, whilst T. longicaudatus individuals have a uniform carapace. The species also appeared about 50 million years later, and, as its name suggests, its elongated tail structures are often nearly as long as the rest of the body, which has been recorded to reach 5 cm (2 in) in length.
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s. The trunk is not distinctly divided into thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
and abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. Most trunk segments bear appendages. Zoologists find it difficult to decide where the thorax stops and the abdomen begins; the debate is seemingly endless. The first 11 trunk segments each bear a single pair of limbs. They are followed by segments that are fused similarly to those of millipede
Millipede
Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...
s, and as a result, each segment bears up to six pairs of limbs. The trunk ends with a region of limbless segments. Some zoologists consider the thorax to consist of the two regions with appendages, and the abdomen the region without appendages. Others believe the region of fused segments to be part of the abdomen. For clarity, this article uses "thorax" to mean the two body regions with limbs.
Carapace
There is a carapaceCarapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
present, but no cephalothorax
Cephalothorax
The cephalothorax is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax...
, since no thoracic segment is fused with the head. The terms carapace and cephalothorax are often confused, but should not be. The carapace of crustaceans is a fold of the body wall of the fifth head segment.
Head
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
compound eyes that lie close to each other, and are nearly fused together. The compound eyes are generally sessile (not stalked). In addition, there is a naupliar ocellus
Ocellus
A simple eye refers to a type of eye design or optical arrangement that contains a single lens which detect light. A "simple eye" is so-called in distinction from a multi-lensed "compound eye", and is not necessarily at all simple in the usual sense of the word...
in between. The compound eyes are on the surface of the head, but the ocellus is deep within the head. All the eyes, however, are easily visible through the shell covering of the head. A distinct horizontal groove, known as the mandibular groove, marks the division between the anterior three head segments and the posterior two. Posterior to it is the cervical groove, marking the division between the head and the thorax.
On the ventral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
side of the head is a lenslike window, admitting light to the naupliar eye, which is aimed both dorsally and ventrally. The first antennae (antennules) are small, slender filaments on the ventral surface of the head, at about the same level as the eyes. The second antennae are similar and lie laterally to the first. They are nonfunctioning. The large, well-developed mandibles
Mandible (arthropod)
thumb|250px|The mandibles of a [[Bull ant]]The mandible of an arthropod is either of a pair of mouthparts used for biting, cutting and holding food. Mandibles are often simply referred to as jaws. Mandibles are present in the extant subphyla Myriapoda , Crustacea and Hexapoda...
oppose each other across the ventral midline. The opposing surfaces bear strong brownish teeth. As the crustacean periodically opens and closes the mandibles the teeth move apart and close together. Of the usual crustacean head appendages, only the mandibles are well developed. In Triops longicaudatus, the larger second maxillae are absent, only maxillules
Maxilla (arthropod)
In arthropods, the maxillae are paired structures present on the head as mouthparts in members of the clade Mandibulata, used for tasting and manipulating food. Embryologically, the maxillae are derived from the 4th and 5th segment of the head and the maxillary palps; segmented appendages extending...
being present.
Thorax
Most of the thoracic appendages resemble each other but the first 11 pairs are best developed. There is a slight tendency to regional specialization and the first pair of legs is unlike the rest. It is an elongated, cheliped-like structure with a sensory function, while all the other appendages aid in feeding, respiration and locomotion. In females, the 11th pair of legs is modified into brood pouches. The many legs posterior to the 11th pair move the spent feeding and respiratory currents away.
Abdomen
The posterior 5–14 rings at the end of the body do not bear appendages. At the end of the body is a pleotelson (fusion of the last abdominal segment and the telsonTelson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
) connected to long, multisegmented uropods.
Feeding behavior
The feeding method of tadpole shrimps is similar to that proposed for the ancestral crustaceanCrustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
. The anterior appendages (second pair to tenth pair) stir sediments and swirl muddy water into the wide, midventral food groove. The gnathobases (inward-facing lobes at the base of the leg) guide food anteriorly to the mouth. The large flat exopods (outward-facing lobes at the end of the leg) stir and lift the sediments. Fine silt particles and water escape easily, but large, coarse food particles are torn into smaller pieces by the blade-like, inward-facing lobes called endopods at the end of the leg.
Internal anatomy
The heart of tadpole shrimps is a long dorsal tube in the anterior 11 trunk segments. It has a pair of ostiaOstium
Ostium may refer to:Anatomy*Ostium of Fallopian tube*Ostium primum or foramen ovale of the developing heart*Ostium maxillare of the maxillary sinus*Ostium of female lepidoptera genitalia...
in each of these segments. Hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
is sometimes present in the blood and the crustacean may be pink as a result. The excretory
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...
organs are the paired maxillary gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
s, located on the segment of the second maxilla. The long looped ducts of these glands can be seen in the carapace. The role of the maxillary glands is primarily osmoregulatory
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...
. Nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, in the form of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, is lost by diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
across the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
surfaces.
Reproduction
Triops longicaudatus displays several reproductive strategies. Individuals may reproduce sexually, but this is rare, as most populations are highly male- or female-biased. ParthenogenesisParthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
(development from unfertilized eggs) is the most common reproductive strategy. Some populations, however, consist of hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
s who fertilize each other. It has been noted that different populations display different strategies or combinations of strategies, and may therefore be considered separate species
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...
or subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
in the future.
In females, the eleventh pair of legs is modified into egg sacs, where the eggs are carried for several hours. The eggs are released in batches and have a thick shell and can stand freezing temperatures as well as drought, enabling the population to survive from one season to the next. The eggs have to dry out completely before being submerged in water again in order to successfully hatch; they may remain in a state of diapause
Diapause
Diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
for up to 20 years. These eggs may have helped Triops longicaudatus, as well as other notostracans, to survive the natural disasters that may have killed the dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s 65 million years ago.
Life cycle
To complete their lives, tadpole shrimps depend on the changing nature of the temporary watersVernal pool
Vernal pools, also called vernal ponds or ephemeral pools, are temporary pools of water. They are usually devoid of fish, and thus allow the safe development of natal amphibian and insect species...
they inhabit. During the dry season (summer and fall), they stay inside the eggs. As the pool fills with rainwater during the winter and spring, they hatch and feed on fairy shrimp
Fairy shrimp
Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are also known as fairy shrimp. They are usually long . Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia , and the body lacks a carapace...
s and other invertebrates. The first larval stage (the metanauplius
Metanauplius
Metanauplius is an early larval stage of some crustaceans such as krill. It follows the nauplius stage.In sac-spawning krill, there is an intermediary phase called pseudometanauplius, a newly hatched form distinguished from older metanauplii by its extremely short abdomen...
) is orange in color. It has a single eye and six legs, and develops through instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s (growth stages). Each instar ends with shedding
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
the exoskeleton. The number of segments and appendages increases as Triops grow, and they slowly change to greyish-brown. In approximately eight days, they reach maturity and lay eggs. Adult Triops die as the pools dry up. Triops generally live for about 20–90 days if the pool doesn't dry up.
Ecology
T. longicaudatus is the most widespread notostracan species, and can be found in western North America, South America, Japan and several Pacific IslandsPacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
. It is most active at a temperature of around 20 °C (68 °F), and is usually found scratching the mud at the bottom of pools, searching for benthic
Benthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...
food. Triops collect food particles by straining the water with hairs on their limbs. Loose food particles are collected in a groove running down the underside of the body lengthwise, and held together by a sticky secretion until they are swallowed by their very small (2 mm wide) mouth. The tiny mouth is deep in the underbelly of their body and whilst capable of breaking up a plant root or dead fish, it is incapable of chasing and eating prey larger than itself.
Diet
Tadpole shrimps are omnivorous and may eat algae, insects and other organic debrisOrganic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
; known to chase very small fry and tadpoles, and oligochaete
Oligochaeta
Oligochaeta is a subclass of animals in the biological phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and this includes all of the various earthworms...
worms. In general, they eat anything organic that is smaller than themselves, which may even include their siblings (they are cannibalistic
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
). In turn, Triops longicaudatus is eaten by frogs and birds.
Interaction with humans
West Nile virus
West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic...
, as the individuals consume Culex
Culex
Culex is a genus of mosquito, and is important in that several species serve as vectors of important diseases, such as West Nile virus, filariasis, Japanese encephalitis, St. Louis encephalitis and avian malaria....
mosquito larvae. They are used as a biological agent
Biological agent
A biological agent — also called bio-agent or biological threat agent — is a bacterium, virus, prion, or fungus which may cause infection, allergy, toxicity or otherwise create a hazard to human health. They can be used as a biological weapon in bioterrorism or biological warfare...
in Japan, eating weeds in rice paddies
Paddy field
A paddy field is a flooded parcel of arable land used for growing rice and other semiaquatic crops. Paddy fields are a typical feature of rice farming in east, south and southeast Asia. Paddies can be built into steep hillsides as terraces and adjacent to depressed or steeply sloped features such...
. In Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, the presence of Triops longicaudatus usually indicates a good chance of the hatching of spadefoot frog
American spadefoot toads
Scaphiopodidae is a family of American spadefoot toads. They are native to southern Canada and USA south to southern Mexico. Scaphiopodidae is a small family, comprising only seven species....
s. Dried eggs of Triops longicaudatus are sold in kits to be raised as aquarium pets, sold under the name of "aquasaurs" or "triops".
It is hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
ed that Triops longicaudatus may continue its trend of longevity as a species and, if humans do not devastate its habitat, the species may survive for another 500 million years.
Distribution
Triops longicaudatus is widespread in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. In Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, it is only found in the provinces of Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
and Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
. It is widespread throughout the continental United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, but not Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. Tadpole shrimps can be found in all parts of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
the West Indies, and the Pacific Islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
, including Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
. The related European species Triops cancriformis
Triops cancriformis
Triops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
is an endangered species in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and is legally protected under Schedule 5 of the Wildlife and Countryside Act 1981
Wildlife and Countryside Act 1981
The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom and was implemented to comply with the Directive 2009/147/EC on the conservation of wild birds...
(as amended).