Louisiana dwarf crayfish

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Louisiana dwarf crayfish
Louisiana dwarf crayfish (Cambarellus shufeldtii)

Louisiana dwarf crayfish ( Cambarellus shufeldtii )

Systematics
Order : Decapods (decapoda)
Partial order : Large crayfish (Astacidea)
Superfamily : Crayfish (Astacoidea)
Family : Cambaridae
Genre : Dwarf crayfish ( Cambarellus )
Type : Louisiana dwarf crayfish
Scientific name
Cambarellus shufeldtii
( Faxon , 1884)

The Louisiana dwarf crayfish ( Cambarellus shufeldtii ) is a dwarf crayfish native to the United States .

features

The Louisiana dwarf crayfish shows a total of four dark brown longitudinal stripes on the top and sides on a light brown background that extend to the telson . The stripes can be jagged and outlined in dark colors or just consist of rows of dark brown spots. The intensity of the drawing is stronger in the females than in the males. The Louisiana dwarf crayfish resembles the boy crayfish ( Cambarellus puer ) and other dwarf crayfish with this drawing . The striding legs are also darkly striped. The length of the cephalothorax in mature males of these two species varies from 7 to 12 millimeters, in mature females up to 14 mm.

The seasonal reproduction cycles of the two cambarids Cambarellus shufeldtii and Cambarellus puer are similar. Both show two annual climaxes of their reproductive activity and in both the adult males switch between two clearly different morphological forms by moulting . The animals are therefore referred to as Form I and Form II males. The change in shape is directly related to the seasonal reproductive cycle. The cambarids change from a phase capable of copulation to a sexually inactive phase. On the underside of the body of the males, the mating pens ( gonopods ) can be seen. They can be used not only to differentiate between the sexes, but also to identify species. In boy cancer, the three finger-shaped extensions of the gonopods are all bent by almost 90 degrees towards the shaft. In the Louisiana dwarf crayfish, the area of ​​distribution of which overlaps with that of the boy cancer, these processes are straight.

The peaks of reproductive activities were analyzed in a 1966 comparative study between the male reproductive cycles of Cambarellus shufeldtii and Cambarellus puer . It was found that form I males ready for copulation and females capable of fertilization could be found in almost every season of the year, but two seasonal high phases could be defined. There was a greater concentration of reproductive activities in January, February and March and a smaller one in July. The Cambarellus puer in particular showed this timing, while the Cambarellus shufeldtii showed a strong tendency towards continuous, year-round reproduction. Despite these differences, males of both species had two major sperm production peaks as adults, with their first burst of sperm occurring during the first reproductive period after their own birth. A second episode occurred when the males were about a year old. Animal growth studies showed an average increase of approximately 0.45 millimeters in cephalothorax length per molt for both species, with 12 to 13 molting in Cambarellus shufeldtii and 13 to 14 molting in boy cancers required to reach sexual maturity.

distribution and habitat

The crustaceans of the genera shufeldti and puer were initially not treated by most zoologists mainly because of their small size, since they were generally considered to be immature individuals of other species. The basic ecological niches of the two cambarids are similar. The Louisiana dwarf crayfish is distributed from southeast Texas to the Mississippi Basin and southern Louisiana with the Mississippi Delta . The type specimen comes from the New Orleans area . The cancer is spread east of the Mississippi in the states of Mississippi and Alabama . From south to north, it stretches from the Mississippi Delta to Kentucky , Arkansas , Tennessee , Missouri and adjoining Illinois .

The Louisiana pygmy crayfish lives in shallow marshy waters with aquatic plants or fallen leaves. If the water dries up, the crustacean can survive in the damp mud for some time until the rain fills the pools again.

Way of life

The early stages of cancer molt 12 to 13 times before they are sexually mature. The females are then often no larger than 1.7 centimeters. They carry 30–40 eggs on the underside of their abdomen. Even after hatching, the young animals, which are just a few millimeters in size, remain on their mother for a few days. They too are sexually mature after around three months. The females can lay eggs twice a year. In between they shed their skin again. Life expectancy is around one year for females and up to 18 months for males.

orientation

The sense of direction of the two dwarf crabs, Cambarellus shufeldti and Cambarellus puer , was obtained in 1963 by the invertebrate scientists George Henry Penn (1918-1963) and Joe B. Black from the Department of Zoology at Tulane University using a simple 32 millimeter wide , water-filled gutter that bifurcated into a Y-shape after 250 millimeters. All of the test crabs were forced to react at the entrance to the channel by constant nudging and pushing. The majority of individuals of both species (> 79%) showed the same behavior because they withdrew into one of the forks. As soon as one of the forks was covered, this hiding place was preferred by 95 percent of the animals. After the extirpation of one eye stalk, 55 percent reacted positively to the cover, but after the extirpation of both eye stalks it was only 37 percent. After removing one chela , 86 percent responded positively to the cover, and after removing both chelae, still 86 percent. The experiments made it clear that both species, typical representatives of the Cambarellus species, tended to avoid open, sun-drenched waters. The particularly high importance of the eyesight for the orientation of the crabs was identified as an essential result of the investigation. A task that the animals' impressive antennae could not cope with.

Parasites in Cambarellus shufeldti

Microsporidia infections are among the most common parasitic diseases in the animal kingdom. The American zoologist and anatomist Franklin Sogandares-Bernal (1931-2016), whose specialty was parasitology , recognized microsporidiosis in the dwarf crabs Cambarellus shufeldti and Cambarellus puer in 1962 . During his examination he had a boy cancer and two Cambarellus shufeldti at his disposal. The former was collected at Chacahoula , Louisiana and the latter just 11 miles east of Covington , Louisiana. It turned out that the muscles of these crabs were infected with microsporidia . Sogandares-Bernal had received the animals by George Henry Penn after it to him unknown, strange milky muscles in Basipoditen the first pereiopods had recognized through the shell of the infected crabs. By then, Penn had examined around 20,000 specimens of various Louisiana crustaceans, but had never observed crabs with milky-colored muscles before. Sogandares -Bernal could not determine pansoroblasts containing sporoblasts in the material available to him, but spores could be determined in Cambarellus puer , which suggested a genus Pleistophora species (Gurley, 1893). The two Cambarellus shufeldti, however, undoubtedly carried parasites of the genus Thelohania . Apparently Sogandares-Bernal investigations brought the first evidence of microsporidia of the genera Thelohania and probably Plistophora in North American crabs. For Sogandares-Bernal, the fact that only a few highly infected crabs were collected indicated that the parasites either kill the affected animals or, through their paralyzing effect, make the hosts easier prey for predators.

literature

  • Walter Faxon: Descriptions of New Species of Cambarus, to Which is Added a Synonymical List of the Known Species of Cambarus and Astacus. Proceedings of the American Academy of Arts and Sciences, 20, pp. 107–158, 1884 (first description)
  • Franklin Sogandares-Bernal : Presumable microsporidiosis in the dwarf crayfishes Cambarellus puer Hobbs and C. shufeldti (Faxon) in Louisiana . In: The Journal of Parasitology 48, 3, (1962), p. 493.
  • George Henry Penn, Joe B. Black: Orientation of the Dwarf Crawfishes Cambarellus shufeldti (Faxon) and C. puer Hobbs in a Simple Maze . In: The American Midland Naturalist 70, 1 (1963), pp. 149-158.
  • Joe B. Black: Cyclic male reproductive activities in the dwarf crawfishes Cambarellus shufeldtii (Faxon) and Cambarellus puer (Hobbs) . In: Transactions of the American Microscopical Society 85, 1966, pp. 214-232.
  • Joseph F. Fitzpatrick Jr .: A Revision of the Dwarf Crayfishes (Cambaridae, Cambarellinae). Journal of Crustacean Biology , 3, 2, pp. 266-277, 1983
  • Horton H. Hobbs Jr .: An Illustrated Checklist of the American Crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Institution Press, 1989
  • CA Taylor, ML Warren Jr., JF Fitzpatrick Jr., Horton H. Hobbs III, RF Jezerinac, WL Pflieger & HW Robison: Conservation Status of Crayfishes of the United States and Canada. Fisheries 21, p. 4, 1996
  • Chris Lukhaup and Reinhard Pekny: Freshwater crabs from all over the world. Dähne-Verlag, 2nd edition, Ettlingen 2008 ISBN 3-935-17540-X

Web links

Individual evidence

  1. ↑ a b c Jerry G. Walls: Crawfishes of Louisiana. Louisiana State University, 2009, p. 210 ISBN 0807134090
  2. ↑ a b c George Henry Penn, Joe B. Black: Orientation of the Dwarf Crawfishes Cambarellus shufeldti (Faxon) and C. puer Hobbs in a Simple Maze . In: The American Midland Naturalist 70, 1 (1963), pp. 149-158; here: p. 149.
  3. ↑ George Henry Penn, Joe B. Black: Orientation of the Dwarf Crawfishes Cambarellus shufeldti (Faxon) and C. puer Hobbs in a Simple Maze . In: The American Midland Naturalist 70, 1 (1963), pp. 149-158; here: pp. 149–150.
  4. ^ Joe B. Black: Cyclic male reproductive activities in the dwarf crawfishes Cambarellus shufeldtii (Faxon) and Cambarellus puer (Hobbs) . In: Transactions of the American Microscopical Society 85, 1966, pp. 214-232.
  5. ↑ Keith A. Crandall, James W. Fetzner Jr. and Horton H. Hobbs Jr .: Cambarellus (Pandicambarus) puer . Tree of Life web project, 2001
  6. ↑ Distribution map of Cambarellus shufeldtii from the United States Geological Survey
  7. ↑ George Henry Penn, Joe B. Black: Orientation of the Dwarf Crawfishes Cambarellus shufeldti (Faxon) and C. puer Hobbs in a Simple Maze . In: The American Midland Naturalist 70, 1 (1963), pp. 149-158; here: p. 154.
  8. ↑ George Henry Penn, Joe B. Black: Orientation of the Dwarf Crawfishes Cambarellus shufeldti (Faxon) and C. puer Hobbs in a Simple Maze . In: The American Midland Naturalist 70, 1 (1963), pp. 149-158; here: p. 157.
  9. ↑ Franklin Sogandares-Bernal: presumable microsporidiosis in the dwarf crayfishes Cambarellus puer Hobbs and C. shufeldti (Faxon) in Louisiana . In: The Journal of Parasitology 48, 3, (1962), p. 493.