Branchiopoda Temporal range: | |
---|---|
![]() | |
Clockwise from top left: Artemia (Anostraca), Triops (Notostraca), Daphnia (Cladocera) & Cyzicus (Spinicaudata) | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Superclass: | Allotriocarida |
Class: | Branchiopoda Latreille, 1817 |
Subclass | |
|
Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca, the Devonian Lepidocaris and possibly the Cambrian Rehbachiella . They are mostly small, freshwater animals that feed on plankton and detritus.
Members of the Branchiopoda are unified by the presence of gills on many of the animals' appendages, including some of the mouthparts. This is also responsible for the name of the group [1] (from the Ancient Greek : βράγχια, gills, akin to βρόγχος, windpipe; Greek : πούς, foot). [2] They generally possess compound eyes and a carapace, which may be a shell of two valves enclosing the trunk (as in most Cladocera), broad and shallow (as in the Notostraca), or entirely absent (as in the Anostraca). [3] In the groups where the carapace prevents the use of the trunk limbs for swimming (Cladocera and clam shrimp), the antennae are used for locomotion, as they are in the nauplius. [3] Male fairy shrimp have an enlarged pair of antennae with which they grasp the female during mating, while the bottom-feeding Notostraca, the antennae are reduced to vestiges. [3] The trunk limbs are beaten in a metachronal rhythm, causing a flow of water along the midline of the animal, from which it derives oxygen, food and, in the case of the Anostraca and Notostraca, movement. [3]
Branchiopods are found in continental fresh water, including temporary pools and in hypersaline lakes, and some in brackish water. Only in two groups of water fleas do we find marine species: Family Podonidae in the order Diplostraca, and family Sididae in the order Diplostraca. [4] [5] [6] Most branchiopodans eat floating detritus or plankton, which they take using the setae on their appendages. [3] But notostracans are omnivorous and very opportunistic feeders and will eat algae and bacteria in addition to animals as both predators and scavengers. [7]
In early taxonomic treatments, the current members of the Branchiopoda were all placed in a single genus, Monoculus. [8] The taxon Branchiopoda was erected by Pierre André Latreille in 1817, initially at the rank of order. [9]
The current upper-level classification of Branchiopoda, according to the World Register of Marine Species (2021), is as follows: [10]
Class Branchiopoda Latreille, 1817
In addition, the extinct genus Lepidocaris is generally placed in Branchiopoda.
The fairy shrimp of the order Anostraca are usually 6–25 mm (0.24–0.98 in) long (exceptionally up to 170 mm or 6.7 in). [11] Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia (swimming legs), and the body lacks a carapace. [12] They live in vernal pools and hypersaline lakes across the world, including pools in deserts, in ice-covered mountain lakes and in Antarctica. They swim "upside-down" and feed by filtering organic particles from the water or by scraping algae from surfaces. [11] They are an important food for many birds and fish, and are cultured and harvested for use as fish food. [8] There are 300 species spread across 8 families. [13]
Lipostraca contains a single extinct Early Devonian species, Lepidocaris rhyniensis , [14] which is the most abundant animal in the Rhynie chert deposits. [15] It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. [16] The body is 3 mm (0.12 in) long, with 23 body segments and 19 pairs of appendages, but no carapace. [17] It occurred chiefly among charophytes, probably in alkaline temporary pools. [18]
The order Notostraca comprises the single family Triopsidae, containing the tadpole shrimp or shield shrimp. [19] The two genera, Triops and Lepidurus , are considered living fossils, having not changed significantly in outward form since the Triassic. [13] They have a broad, flat carapace, which conceals the head and bears a single pair of compound eyes. [11] The abdomen is long, appears to be segmented and bears numerous pairs of flattened legs. [11] The telson is flanked by a pair of long, thin caudal rami. [3] Phenotypic plasticity within taxa makes species-level identification difficult, and is further compounded by variation in the mode of reproduction. [13] [20] The evidence of phenotypic plasticity of Arctic tadpole shrimp ( Lepidurus arcticus , Notostraca) has been observed in Svalbard. [21] Notostracans are the largest branchiopodans and are omnivores living on the bottom of temporary pools, ponds [21] and shallow lakes. [11]
Clam shrimp are bivalved animals which have lived since at least the Devonian. The three groups are not believed to form a clade. They have 10–32 trunk segments, decreasing in size from front to back, and each bears a pair of legs which also carry gills. A strong muscle can close the two halves of the shell together.
These four orders make up a group of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. [22] They are ubiquitous in inland aquatic habitats, but rare in the oceans. [11] Most are 0.2–6.0 mm (0.01–0.24 in) long, with a down-turned head, and a carapace covering the apparently unsegmented thorax and abdomen. [23] There is a single median compound eye. [11] Most species show cyclical parthenogenesis, where asexual reproduction is occasionally supplemented by sexual reproduction, which produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats. [24] In the water bodies of the world, a lot of Cladocera are non-native species, many of which pose a great threat to aquatic ecosystems. [25]
The fossil record of branchiopods extends back at least into the Upper Cambrian and possibly further. The group is thought to be monophyletic, with the Anostraca having been the first group to branch off. [26] It is thought that the group evolved in the seas, but was forced into temporary pools and hypersaline lakes by the evolution of bony fishes. [11] Although they were previously considered the sister group to the remaining crustaceans, it is now widely accepted that crustaceans form a paraphyletic group, and Branchiopoda are thought to be sister to a clade comprising Xenocarida (Remipedia and Cephalocarida) and Hexapoda (insects and their relatives). [27] [28]
The order Notostraca, containing the single family Triopsidae, is a group of crustaceans known as tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, with similar forms having existed since the end of the Devonian, around 360 million years ago. They have a broad, flat carapace, which conceals the head and bears a single pair of compound eyes. The abdomen is long, appears to be segmented and bears numerous pairs of flattened legs. The telson is flanked by a pair of long, thin caudal rami. Phenotypic plasticity within taxa makes species-level identification difficult, and is further compounded by variation in the mode of reproduction. Notostracans are omnivores living on the bottom of temporary pools and shallow lakes.
Clam shrimp are a group of bivalved branchiopod crustaceans that resemble the unrelated bivalved molluscs. They are extant and also known from the fossil record, from at least the Devonian period and perhaps before. They were originally classified in the former order Conchostraca, which later proved to be paraphyletic, due to the fact that water fleas are nested within clam shrimps. Clam shrimp are now divided into three orders, Cyclestherida, Laevicaudata, and Spinicaudata, in addition to the fossil family Leaiidae.
Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are referred to as fairy shrimp. They live in vernal pools and hypersaline lakes across the world, and they have even been found in deserts, ice-covered mountain lakes, and Antarctic ice. They are usually 6–25 mm (0.24–0.98 in) long. Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia, and the body lacks a carapace. They swim "upside-down" and feed by filtering organic particles from the water or by scraping algae from surfaces, with the exception of Branchinecta gigas, or "giant fairy shrimp", which is itself a predator of other species of anostracans. They are an important food for many birds and fish, and some are cultured and harvested for use as fish food. There are 300 species spread across 8 families.
Triops is a genus of small crustaceans in the order Notostraca. The long-lasting resting eggs of several species of Triops are commonly sold in kits as pets. The animals hatch upon contact with fresh water. Most adult-stage Triops have a life expectancy of up to 90 days and can tolerate a pH range of 6 to 10. In nature, they often inhabit temporary pools.
Triops longicaudatus is a freshwater crustacean of the order Notostraca, resembling a miniature horseshoe crab. It is characterized by an elongated, segmented body, a flattened shield-like brownish carapace covering two thirds of the thorax, and two long filaments on the abdomen. The genus name Triops comes from Greek ὤψ or ṓps, meaning "eye" prefixed with Latin tri-, "three", in reference to its three eyes. Longicaudatus is an Latin neologism combining longus ("long") and caudatus ("tailed"), referring to its long tail structures. Triops longicaudatus is found in fresh water ponds and pools, often in places where few higher forms of life can exist.
Branchinecta is a genus of fairy shrimp in family Branchinectidae. It includes around 50 species, found on all continents except Australia. Branchinecta gigas, the giant fairy shrimp, is the largest species in the order, with a length of up to 10 centimetres (4 in), and Branchinecta brushi lives at the highest altitude of any crustacean, at 5,930 metres (19,460 ft), a record it shares with the copepod Boeckella palustris. A new genus, Archaebranchinecta was established in 2011 for two species previously placed in Branchinecta.
Lepidurus packardi, the vernal pool tadpole shrimp, is a small, rare species of tadpole shrimp (Notostraca) found in temporary ponds of the western United States.
Triops australiensis, sometimes referred to as a shield shrimp, is an Australian species of the tadpole shrimp Triops.
The Diplostraca or Cladocera, commonly known as water fleas, is a superorder of small, mostly freshwater crustaceans, most of which feed on microscopic chunks of organic matter, though some forms are predatory.
Arctic tadpole shrimp Lepidurus arcticus is a species of tadpole shrimp which inhabits ephemeral pools, ponds or permanent freshwater lakes of Finland, Norway, Sweden, Svalbard, Greenland, Iceland, Russia and the Kuril Islands.
Branchipodidae is a family of fairy shrimp, one of eight in the order Anostraca. It contains 35 extant species in five extant genera:
Chirocephalus diaphanus is a widely distributed European species of fairy shrimp that lives as far north as Great Britain, where it is the only surviving species of fairy shrimp and is protected under the Wildlife and Countryside Act 1981. It is a translucent animal, about 0.5 in (13 mm) long, with reddened tips to the abdomen and appendages. The body comprises a head, a thorax bearing 11 pairs of appendages, and a seven-segmented abdomen. In males, the antennae are enlarged to form "frontal appendages", while females have an egg pouch at the end of the thorax.
Lepidocaris rhyniensis is an extinct species of crustacean. It is the only species known from the order Lipostraca, and is the only abundant animal in the Pragian-aged Rhynie chert deposits. It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. The body is 3 mm (0.12 in) long, with 23 body segments and 19 pairs of appendages, but no carapace. It occurred chiefly among charophytes, probably in alkaline temporary pools.
Branchinecta paludosa is a species of fairy shrimp with a Holarctic distribution.
Crustaceans are a group of arthropods that are a part of the subphylum Crustacea, a large, diverse group of mainly aquatic arthropods including decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, opossum shrimps, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. The three classes Cephalocarida, Branchiopoda and Remipedia are more closely related to the hexapods than they are to any of the other crustaceans.
Lepidurus apus, commonly known as a tadpole shrimp, is a notostracan in the family Triopsidae, one of a lineage of shrimp-like crustaceans that have had a similar form since the Triassic period and are considered living fossils. This species is cosmopolitan, inhabiting temporary freshwater ponds over much of the world, and the most widespread of the tadpole shrimps. Like other notostracans, L. apus has a broad carapace, long segmented abdomen, and large numbers of paddle-like legs. It reproduces by a mixture of sexual reproduction and self-fertilisation of females.
Streptocephalus sirindhornae is a species of crustacean in the family Streptocephalidae; a genus of freshwater dwelling shrimp belonging to the Anostraca order of Branchiopoda. It is endemic to Thailand, and it was named after Princess Sirindhorn.
Podonidae is a family of onychopods in the order Diplostraca. There are about 8 genera and at least 20 described species in Podonidae. A lot of them are non-native species, many of which pose a great threat to aquatic ecosystems.
Lynceidae is a family of clam shrimp in the order Laevicaudata. There are about 5 genera and more than 20 described species in Lynceidae.