What makes a crayfish a crustacean

Besides the pair of compound eyes, at least some crustacean larvae have a non-imaging photoreceptor system based on a naupliar eye and possibly other frontal eyes. Larval compound eye photoreceptors send axons to a large and well-developed optic lobe consisting of a series of neuropils that are similar to those of adult crustaceans and insects, implying sophisticated analysis of visual stimuli. The visual system fosters a number of advanced and flexible behaviors that permit crustacean larvae to survive extended periods in the plankton and allow them to reach acceptable adult habitats, within which to metamorphose [ 15 ].

Crustaceans are mainly males, excavate burrows largely in carbonate substrates, and are therefore referred to as the burrowing barnacles. While their greatest diversity is found in shallow tropical seas, the most generalized or primitive members are found for the most part in deep water between and m.

Trace fossils, ranging back to the Devonian if not the Ordovician [ 16 ], reveal that species once occupied relatively high latitudes in Northern Europe and Gondwanaland, and at least one extant species is known from Antarctic waters today. Interpretation of the crustacean burrows from Mallorca makes them very comparable to some modern and fossil thalassinidean burrow systems [ 17 , 18 ], and it is a direct consequence of the versatile behavior of fossorial shrimps.

The helical burrows described herein were very likely part of complex burrow systems produced by thalassinideans. From an ichnotaxonomic point of view, these would be compound structures composed of pellet-lined Ophiomorpha and unlined Thalassinoides branching tunnels, sometimes with spreiten due to vertical shifting Teichichnus , or double Lapispira helical elements. Such double helix elements Lapispira were previously known only from the Jurassic as isolated burrows, also assigned to crustaceans [ 13 ].

Despite the lesser geometric regularity of the Mallorcan burrows, the presence of a knobby lining and the fact that these may be connected to branching systems. The new occurrence of this unusual ichnogenus may record a case of behavioral convergence expressed in burrow architecture [ 19 ] Figures 3 — 6.

While most crustaceans are marine, a large number of crayfish live in freshwater, including crayfish Figure 7. Etyus martini is one of the more common crabs in the Gault Clay Figure 8. Spiny lobsters are among the larger crustaceans. Big specimens can weigh several kilograms and make very good eating Figure 9.

Helical burrows. Chthamalus stellatus Sessilia. Fossil stomatopod, center image by Dr. Cees Hof, used with permission. Etyus martini. Spiny lobsters. The crustaceans, such as crabs and lobsters, that have hard exoskeletons reinforced with calcium carbonate tend to preserve well as fossils, but many crustaceans have only thin exoskeletons.

Most of the crustacean fossils known are from coral reef or shallow sea-floor environments, but many crustaceans live in open seas, on deep sea floors, or in burrows. Crustaceans tend, therefore, to be rare in the fossil record than trilobites.

Some crustaceans are reasonably common in Cretaceous and Cenozoic rocks, but barnacles have a particularly poor fossil record, with very few specimens from before the Mesozoic era. The Late Jurassic lithographic limestones of Solnhofen, Bavaria, which are famous as the home of Archaeopteryx, are relatively rich in decapod crustaceans five pairs of legs , such as Eryon an eryonoid , Aeger a prawn , or Pseudastacus a lobster.

Crabs have been found at a number of sites, such as the Cretacoues Gault clay and the Eocene London clay. Ostracods are tiny crustaceans, typically about one to two millimeters in length, with a well-documented fossil record beginning in the early Ordovician e. During the Ordovician period, ostracods already possessed a global biogeographical distribution from high southern latitudes to the palaeo-tropics [ 26 ].

Crustacean ostracods are variously represented in washing residue and thin sections, two valves left and right valves , the two valves being joined together along the hinge line. The body covered by external shell called Carapace is composed of two valves connected in the Dorsal side. Two valves are equal in the genus Amphisites or overlapping in Cytherella. Ovoid shape or semi ovoid, 0. Articulation along the dorsal margin is further characterized by development of teeth, socket, ridges, and grooves all together called hinge element hinge elements: teeth, socket, grooves, and ridge-bar.

The body is subdivided into Cephalon, Thorax, and Posterior, seven pairs appendages antenna, antennule, mandible, maxilla, 1st thoracic leg, 2nd thoracic leg, and 3rd thoracic leg , one eye center, and two lateral calcareous part—internal and outer lamella with the valves are hard calcareous part, Carapace—right and left valve connected with hinge Figure Ostracoda shell.

Marginal denticulation: most of the species in Ostracoda have more denticulations resemble to tooth accumulated on the external margin of the valves; the number and shape of these denticulation differ from one sp.

Caudal process: some of the species in Ostracoda are characterized by having elongated end that is long and narrow and ended by anus. This caudal process is on the mid-posterior or on the posterodorsal side or posteroventral side. Hinge ears: some species of Ostracoda have protuberance on anterior side of the hinge line which is formed by addition of calcareous materials. Posteroventral spine: it is an calcareous spine on the posteroventral side, usually to the posterior side.

Anteroventral beak-rostrum Cypridea : some genera of Ostracoda are characterized by having protuberance resembling to beak, which is most abundant in the genus Cypridea. Is shown in the carapace view. The outer surfaces of the ostracod valves can be smooth or ornamented with pits, striations, reticulations, spines, sulci, tubercles, and wing-shaped alae Figure 11 [ 22 ].

Ornamentation in some species of Ostracoda. Normal pores open normal pores and sieve normal pores and open normal pores: these pores penetrated the carapace, but sieve normal pores penetrated the wall.

Marginal pores: these pores penetrated the test wall vertically and are distributed on the external surface; the number of the pores differ from family, genus species, and important in classification.

Marginal pore canal: long pores distributed on the marginal zone; more pores on the anterior part than the other parts are also important in the classification.

Test in ostracods is composed of calcareous material with chitineous test around them which helps to fix the hinge. Hinge elements are Hinge elements: teeth, socket, grooves, ridge-bar Figure Important parts in Ostracoda. The teeth in crustacean differ from one taxon to another; for example, ostracods have Adont hinge which is the simplest, without teeth or sockets, and often form part of a contact groove on the larger valve and a corresponding ridge on the smaller valve.

The Merodont hinge is composed of a tooth and socket at each end of a groove or ridge structure complementary negative and positive structures in left and right valves. The Amphidont hinge has a more complex median structure with an anterior tooth and socket Figure Teeth types in Ostracoda.

Ostracods as a mode of life are pelagic planktonic by using organic-walled shell less CaCO 3 or by producing oil droplets. They can burrow, swim near the sea-bed, or crawl on or through the sediment.

Benthic forms occur in all the aquatic environments from the abyss to the shoreline. They also occur in estuaries, lagoons, freshwater lakes, ponds and streams, salt lakes, hot springs, and damp vegetation Figure Psychrospheric and thermospheric ostracods. Ostracods can be influenced ecologically by various factors such as [ 27 ]: Type of the substrate: swimmers have smooth, thin, bean-shaped carapace; fine-grained mud dwellers have flattened ventral, wing-shaped carapace; coarse-grained sand dwellers have thick carapace with coarse ornamentation; and interstitial ostracods are small, long, and robust.

Salinity: ostracods carapace morphology tends to vary according to variation in salinity. They occur in fresh water 0. Fresh water ostracods—simple morphology, hinge adont, thin carapace, no marginal pores, and other weakly developed variable abundance and diversity.

Most shelf seas ostracods: low abundance, high diversity, stenohaline Cytheropteron. Brackish lagoon and estuaries ostracods: thick shell, weakly ornamented, marginal pore canal, amphidont hinge. High abundance, low diversity, euryhaline, Cyprideis with tubecles. Hypersaline lagoons ostracods, high abundance, low diversity, euryhaline, Cyprideis. Marine ostracods-continental shelf: strongly calcified carapace, strongly ornamented, hinge well developed Figure Class Maxillopoda is a very diverse group of crustaceans, including such varied organisms as barnacles and the parasitic fish lice.

The most diverse subset of this group is the copepods, many of which are important members of the zooplankton fauna of lakes and ponds, and some of which are parasitic on fish.

Both planktonic and parasitic copepods are found in Arkansas. Class Ostracoda is a large group of superficially clam-like crustaceans sometimes known as seed shrimp. Some species are part of the zooplankton in freshwaters and oceans, but most live on the sea floor and some are even found in humid tropical forest soils. Class Malacostraca is the largest group of crustaceans, including such well-known examples as crabs, shrimp , and lobsters.

Malacostracans are abundant in the oceans of the world and also exist in freshwater and on land. They share a common body plan composed of a head, an eight-segmented thorax, and an abdomen of usually six segments. Within this group, Arkansas is home to noteworthy species of peracarids amphipods, isopods and decapods shrimp, crayfish. Arkansas Malacostraca In peracarids superorder Peracarida , the basal segments of the legs have flattened plates that enclose a pouch where the young develop; this is called the marsupium.

In contrast to the peracarids are the eucarids superorder Eucarida , characterized by having stalked eyes and a carapace fused to all thoracic segments.

Arkansas is home to two native shrimp species. The Mississippi Grass Shrimp Palaemonetes kadiakensis is a common inhabitant of wetlands in the southern and eastern half of the state. The most impressive of the crustaceans are the members of the infraorder Astacidea, with their enlarged first pair of claws, or chelae. The clawed lobsters family Nephropidae , a well-known symbol of fine dining, are marine and have pelagic larvae which have the potential to disperse long distances.

Crayfishes Worldwide, crayfishes fall into three families and reach their greatest diversity in the southeastern United States, where all species are in the family Cambaridae. Arkansas has nearly sixty different crayfish species, more than any other state west of the Mississippi River , and eight species are endemic to the state.

Two Arkansas crayfish species are designated as endangered under the federal Endangered Species Act. The genus Bouchardina is monotypic—meaning that it includes only one species—and endemic to Arkansas. Bouchardina robisoni , the Bayou Bodcau Crayfish, grows to a maximum size of less than two inches and inhabits seasonally flooded backwaters of Bayou Bodcau in south-central Arkansas.

This species is an example of a secondary burrower, a crayfish that lives much of the year in burrows but is found in surface waters for part of the year. Three members of the genus Cambarus are endemic to Arkansas. Cambarus aculabrum , the Benton County Cave Crayfish, and Cambarus zophonastes , the Hell Creek Cave Crayfish, are white, eyeless crayfish found only in caves and designated as endangered species under the federal Endangered Species Act.

The third species, Cambarus causeyi , the Boston Mountains Crayfish, is a primary burrower found around highland springs in the Boston Mountains ecoregion. The genus Fallicambarus reaches its peak diversity in Arkansas with six endemic species and nine total species found in the state.

Members of this genus are examples of primary burrowers—they spend the majority of their life in burrows, often in lawns and roadside ditches. They venture onto the surface only during warm, moist nights in order to find supplemental food items or mates.

Both are found in the Ouachita Mountains region of Oklahoma and Arkansas and are examples of tertiary burrowers—species that live in rocky stream bottoms and rarely if ever burrow.

While the major crayfish farming operations are primarily in Louisiana, Arkansas does have some smaller operations as secondary crops for farmers of rice or fish. Crayfish are also commonly used as fishing bait, since they are prominent in the diet of many of our popular sportfish. People are often aware of primary burrowing crayfish by the mud chimneys they build. However, these crayfish are causing little real harm, their chimney-building will end during dry seasons, and their tunneling activity mixes and aerates the soil, making it more productive.

Efforts continue to improve the understanding of Arkansas crayfish, but there is much to be learned regarding the taxonomy, distribution, life history, and conservation status of many of the crayfish species in the state.

For additional information: ohnson, S. Texas Crawdads. Martin, J. An Updated Checklist of the Recent Crustacean. Orconectes rusticus Though this species, commonly known as the Rusty Crayfish, is native to the basin of the Ohio River, it was introduced in many rivers in United States, Canada and Europe.

In systems where it is established, the Rusty Crayfish manages to overcome its indigenous competitors and cause their populations to drop in proportion to the growth of its own population Lodge et al.

This species already problematic in North America Olden et al. The potential invasion of Quebec freshwater habitats by the Rusty Crayfish calls for better knowledge of the crayfish status and continued tracking of its communities along the fluvial corridor of the St.

Orconectes limosus O. The distribution of the Spinycheek Crayfish throughout the St. Even if the species has spread throughout most of the fluvial corridor, and in spite of its ability to migrate upstream, it has not been observed upstream of these structures. The Spinycheek Crayfish has had significant impact on indigenous species in European countries where it was introduced, and proved to be an aggressive and invasive species Holdich et al.

According to Hamr , the species was first observed in Quebec around although its presence in the river was first noted in Despite uncertainties surrounding the causes of its presence in the St. Lawrence, it is necessary to document the distribution of the Spinycheek Crayfish as well as its status among the crayfish communities of Quebec. Despite their importance in freshwater ecosystems, crayfish have been of relatively little scientific interest in Quebec.

Nationally, the only existing reference document written by Hamr , presented a brief morphological description and the geographical distribution of species. When released in , the article reported on a significant information gap regarding crayfish in Quebec. That being said, information on crayfish communities still remains very fragmented, especially relating to the St.