Boy cancer

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Boy cancer
Systematics
Order : Decapods (decapoda)
Partial order : Large crayfish (Astacidea)
Superfamily : Crayfish (Astacoidea)
Family : Cambaridae
Genre : Dwarf crayfish ( Cambarellus )
Type : Boy cancer
Scientific name
Cambarellus puer
Hobbs , 1945
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The boy crayfish ( Cambarellus puer ) is a species of the pygmy crayfish ( Cambarellus ) native to the USA . It was first described by the American crustaceologist and taxonomist Horton H. Hobbs Jr. (1914-1994). The species-identifying epithet puer ( Latin for “child”, “boy”) refers to the males of this species, which are clearly smaller than the females and which are considered harmless on the red list of endangered species .

features

The basic colors of the dorsal and lateral surfaces of the chelae , carapaces and abdomen of the boy cancer are variable and range from rust-red to light brown to gray. Two brown or black longitudinal stripes can appear on the carapace and abdomen of the animal, extending from above the eyes to the telson . The stripes can also have a dark border. Varying from this, the cancer can also have two rows of spots of the same color that run along the body as continuous bands. These spots are rarely outlined with dark circles. The belly is cream-colored to whitish. Both drawing variants occur in both sexes. The striding legs are also darkly striped. With this drawing, the boy cancer resembles the Louisiana dwarf crayfish ( Cambarellus shufeldtii ). The color dimorphism the Cambarellus puer probably lies in the ecological and evolutionary proximity of the two cancers.

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 female animals of the boy cancer reach a maximum size of 40 mm, the males remain significantly smaller with 20 to 30 mm.

The seasonal reproductive cycles of the two cambarids Cambarellus puer and Cambarellus shufeldtii 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 the copulatory form I to the sexually inactive form II. On the underside of the body, the mating pens ( gonopods ) can be seen in the males . 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 activity were analyzed in 1966 by Joe B. Black at McNeese State University in Lake Charles , Louisiana, in a comparative study between the male reproductive cycles of Cambarellus puer and Cambarellus shufeldtii . 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, the males of both species had two major sperm production peaks as adults, with their first large burst of sperm occurring during their first reproductive period after birth, i.e. in the first year of life. 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.

In a study from 1979 it was shown that local variants of boy cancer had developed. Animals from southeast Texas were longer and narrower relative to the length of the cephalothorax than animals from southern Arkansas and northern Louisiana, which are relatively shorter and wider. Populations found along the Mississippi and west of southern Louisiana, however, were of medium stature. Overall, it was found that cambarids from the eastern populations grew larger than animals from the western populations.

distribution and habitat

The crustaceans of the genera Cambarellus puer and Cambarellus shufeldtii 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.

Boy cancer is native to the southern states of the United States . Its distribution area extends from the Texas counties Brazos and Brazoria in the west, along the coastal plains in the Gulf of Mexico to the Mississippi basin . In Texas, it occurs in shallow waters with aquatic vegetation and underground hiding places. This is where the animals take refuge during periods of drought or dry summers. In southern Louisiana , the boy crayfish prefers semi-permanent, shallow waters that have a certain aquatic flora, with some occurrences there also in marshy river arms and slow-flowing streams. From south to north it can be found from the Mississippi Delta to the extreme south of Illinois ( Johnson County ). The ichthyologist Lawrence M. Page from the University of Illinois at Urbana-Champaign reported in 1985 that the boy cancer could be found there, in southern Illinois, in mostly permanent waters. The species was also discovered in a very limited area in southeast Oklahoma state . Here it was a swampy area of ​​thick vegetation along the Little River in McCurtain County . According to information from 2013, however, the cancer has not been detected there since 1975. The ichthyologist and astacologist Christopher A. Taylor from the University of Illinois at Urbana-Champaign and the zoologist Guenter A. Schuster from Eastern Kentucky University discovered in 2004 that boy cancer is also widespread in Kentucky , albeit to a very small extent. It was found there in the area of ​​the Mayfield Creek drainage system, which drains into the Mississippi and extends into McCracken and Graves Counties , which are in a gusset between the states of Illinois in the north and Missouri in the west and are part of the Jackson Purchase . This region, located in the extreme west of Kentucky, is partly dominated by extensive cypress swamps. These swamps are preferred by the Jackson Purchase crab, where it exists under living or dead vegetation. Given the abundance of suitable habitats in western Kentucky, the two scientists found the limited spread of boy cancer in that state strange. As possible explanations, they could imagine a previously incomplete sampling of possible lowland habitats or interactions between the two types of cancer of the genera Cambarellus puer and Cambarellus shufeldtii . The invertebrate scientists George Henry Penn (1918–1963) and Joseph F. Fitzpatrick Jr. (1932–2002) had already established in 1962 and 1963 after experimental tests that Cambarellus shufeldtii was dominant over Cambarellus puer and that Cambarellus shufeldtii was the competitor Cambarellus puer had displaced it for several years at several locations along the Gulf Coast. Page (1985) suggested that this exclusion of competition between the two species could partially explain their distribution in southern Illinois. In western Kentucky, Cambarellus shufeldtii is far more common and widespread in lowland habitats. In 1985, Page had suggested that this exclusion of competition between the two species could partially explain their distribution in southern Illinois. Cambarellus shufeldtii is far more common in western Kentucky and has become widespread in lowland habitats.

The numerous wetlands around the basin and delta of the Mississippi offer the boy crayfish an ideal habitat . It lives in swamps, pools, ponds, ditches and slow flowing waters as well as bayous . The type specimen after which the species was described comes, for example, from a ditch around 11 kilometers west of Dayton in Liberty County in Texas ( Highway 90 ).

orientation

The sense of direction of the two dwarf crabs, Cambarellus puer and Cambarellus shufeldtii , was obtained in 1963 by invertebrate scientists Penn and Joe B. Black from the Department of Zoology at Tulane University using a simple, 32 millimeter wide, water-filled channel that extends after 250 millimeters it forked in a Y-shape. 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.

Parasite infestation in boy cancer

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 puer and Cambarellus shufeldtii in 1962 . During his examination he had a boy cancer and two Cambarellus shufeldtii 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 shufeldtii, 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. Also in 1962, Sogandares-Bernal published the isolation of the Microphallus progeneticus , a parasitic trematode on the Cambarellus puer .

Keeping in the aquarium

The Canadian biologist and crustacean expert Zen Faulkes stated in 2015 that Cambarellus puer was not found in the pet trade in the United States , but in Germany and the Czech Republic . At that time, however, the animal had been introduced to the German market for a long time. In the internet magazine Garnele online , issue 1, 2007, the hobby aquarists Christian Splettstößer and Volker Eßer reported about the cancer, which is “relatively new to the hobby”.

The German Animal Welfare Act (TierSchG) requires that all animals to be cared for must be fed, cared for and housed appropriately according to their species and needs. No one should inflict pain, suffering, or harm on an animal for no good reason. In addition, keepers must have the knowledge and skills required for adequate nutrition, care and behavioral accommodation of the animal. In a similar way, the Animal Welfare Act in Austria stipulates that no animal may be inflicted unjustifiably pain, suffering or harm, or that it may be terrified. There animals are to be kept in such a way that their bodily functions and behavior are not disturbed and their adaptability is not overwhelmed. In Switzerland, in addition to similar aspects, dignity, the intrinsic worth of the animal, comes into play. In all countries, however, the status of invertebrates, in this case crabs, remains problematic, as the legislators have still not ascribed any or only a reduced sense of pain to this class of animals, although aquarium experts and scientists have long since provided evidence that crabs are capable of suffering.

Before purchasing an aquarium, sufficient information on keeping it must be available, because the care of the boy cancer also has its special difficulties. For a large part of the aquatic animals kept by humans, the smaller an aquarium is planned, the more complicated it is to keep them, since a stable balance of the complex biological-ecological structures and functions of the abiotic and biotic processes is more difficult to achieve. In community aquariums in particular, it quickly becomes clear how fragile and unstable an otherwise intact habitat can become in the event of human failure. Here beginners' mistakes can be avoided with appropriately acquired information.

Boy cancer tends to lead a shadowy existence in the German-language specialist literature and is usually treated only marginally. Even the very detailed "Aquarium Atlas" by the aquarists Hans A. Baensch and Hans-Georg Evers from 2002 does not list the animal. The invertebrate experts and non-fiction authors Reinhard Pekny and Chris Lukhaup describe the behavior of the cancer as very peaceful and see a water temperature between 14 and 35 degrees Celsius as possible, whereby they separately point out that it is kept at room temperature. Splettstößer and Eßer have had good experiences with temperatures between 20 ° C and 28 ° C. They raised concerns that higher or lower values ​​are tolerated, but are not recommended in the long term. According to ichthyologists Jakob Geck and Ulrich Schliewen , section head of the Zoological State Collection in Munich , the water should be “rather cool” at 16 to 25 ° C. Splettstößer and Eßer saw a somewhat harder water with a pH value above 7 as favorable. Here Geck and Schliewen wrote very similarly that the pH value should be 7 to 8, that is, the water should be “medium hard to hard, under no circumstances acidic”, i.e. below a pH value of 7.

Geck and Schliewen stated in 2017 that the conditions for keeping the boy cancer were similar to those for the pygmy crayfish . They therefore saw care in a tank with a capacity of at least 25 liters as possible, but generally asked for the animals to be kept in pairs. In addition, in their opinion, the filtering must not be too strong in order to get some sludge and plant residues, which are considered to be an important food supplement for the crabs. As in nature, the aquarium should have densely vegetated areas. In connection with a community tank, Pekny and Lukhaup mention that the boy crayfish should only be kept with very small fish, which is also emphasized by Splettstößer and Eßer as well as Geck and Schliewen. The latter were of the opinion that the reluctant nature of the crabs would tend to lead to the fact that the crabs would otherwise hardly get their food. Splettstößer and Eßer can imagine species of armored catfish as companions, some of which are also active free-swimming. Cancer females can become pregnant almost all year round and carry between 40 and 110 eggs.

literature

  • Horton H. Hobbs Jr .: Two New Species of Crayfishes of the Genus Cambarellus from the Gulf Coastal States, with a Key to the Species of the Genus (Decapoda, Astacida). American Midland Naturalist, 34, 2, pp. 466–474, 1945 (first description)
  • Horton H. Hobbs Jr .: An Illustrated Checklist of the American Crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Institution Press, 1989
  • 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.
  • Franklin Sogandares-Bernal: Microphallus progeneticus, a new Apharyngeate Progenetic Trematode (Microphallidae) from the Dwarf Crayfish, Cambarellus puer , in Louisiana . In: Tulane Studies in Zoology 9, 5 (1962) pp. 319-322.
  • 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: Comparison of the Male Reproductive Cycles in the Dwarf Crawfishes Carnbarellus shufeldti and Cambarellus puer (abstract). IN: American Zoologist 3 (1963), p. 524.
  • 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.
  • Joe B. Black, and RS Latiolais: Inheritance of Chromatophore Pattern in the Dwarf Crayfish Cambarellus puer Hobbs (Abstract). In: Proceedings of the Louisiana Academy of Sciences 40 (1977). P. 121.
  • Lawrence M. Page, Brooks M. Burr: Distributional Records for the Crayfishes Cambarellus puer, C. shufeldti, Procambarus gracilis, P. viaeviridis, Orconectes lancifer, O. bisectus, and O. rusticus . In: Transactions of the Kentucky Academy of Science, 34 (1973), pp. 51-52.
  • Carlene L. Chambers, James F. Payne, Michael L. Kennedy: Geographic Variation in the Dwarf Crayfish, Cambarellus puer (Crustacea: Decapoda) (abstract). In: ASB Bulletin 23 (1976), p. 49.
  • Carlene L. Chambers, James F. Payne, Michael L. Kennedy: Correlation of Environmental Factors with the Geographic Variation of the Dwarf Crayfish , Cambarellus puer (abstract). In: Journal of the Tennessee Academy of Science 62 (1977), p. 72.
  • Carlene L. Chambers, James F. Payne, Michael L. Kennedy: Geographic variation in the dwarf crayfish, Cambarellus puer Hobbs (Decapoda, Cambaridae) . In: Crustaceana 36, 1 (1979), pp. 39-55.
  • Carlene L. Chambers, James F. Payne, Michael L. Kennedy: Geographic Variation in the First Pleopod of the Form I Male Dwarf Crayfish. Cambarellus puer Hobbs (Decapoda, Cambaridae) . In: Crustaceana 38, 2, (1980), pp. 169-177.
  • Christopher A. Taylor, Melvin L. Warren, Jr., Joseph F. Fitzpatrick, Jr., Horton H. Hobbs III, Raymond F. Jezerinac, William L. Pflieger, Henry W. Robison: Conservation Status of Crayfishes of the United States and Canada . In: Fisheries 21 (1996), p. 4.
  • Christopher A. Taylor, Guenter A. Schuster: The crayfishes of Kentucky . (= Illinois Natural History Survey Special Publication 28), 2004, ISBN 1-882932-09-9 , p. 52.
  • 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 Reinhard Pekny, Chris Lukhaup: Freshwater Crabs (= GU Tierratgeber ), Gräfe and Unzer, Munich 2009, ISBN 978-3-8338-1606-2 , p. 19.
  2. ^ Tadashi Kawai , Keith A. Crandall : Global Diversity and Conservation of Freshwater Crayfish (Crustacea: Decapoda: Astacoidea) . In: Tadashi Kawai , Neil Cumberlidge (Eds.): A Global Overview of the Conservation of Freshwater Decapod Crustaceans . Springer, Cham 2016, ISBN 978-3-319-42527-6 , pp. 65-114; here: p. 70.
  3. ↑ a b c d e Christopher A. Taylor, Guenter A. Schuster: The crayfishes of Kentucky . (= Illinois Natural History Survey Special Publication 28), 2004, ISBN 1-882932-09-9 , p. 52.
  4. ↑ a b c Jerry G. Walls: Crawfishes of Louisiana. Louisiana State University, 2009, p. 210 ISBN 0807134090
  5. ↑ a b c d 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.
  6. ↑ Knabenkrebs, Cambarellus puer , invertebrates in the aquarium, crabs, shrimps, snails, crabs, from August 8, 2014, accessed on December 15, 2015.
  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: pp. 149–150.
  8. ^ 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.
  9. ^ Carlene L. Chambers, James F. Payne, Michael L. Kennedy: Geographic variation in the dwarf crayfish, Cambarellus puer Hobbs (Decapoda, Cambaridae) . In: Crustaceana 36, 1 (1979), pp. 39-55.
  10. ↑ a b Keith A. Crandall, James W. Fetzner Jr. and Horton H. Hobbs Jr .: Cambarellus (Pandicambarus) puer . Tree of Life web project, 2001
  11. ^ Sterling K. Johnson, Nathan K. Johnson: Texas crawdads , Crawdads Club Designs, College Station, Texas, 2008, ISBN 0980110300 .
  12. ^ William L. Pflieger: The crayfishes of Missouri . Missouri Department of Conservation, Jefferson City, Missouri, 1996 ISBN 188724705-X .
  13. ^ A b Lawrence M. Page : The Crayfishes and Shrimps (Decapoda) of Illinois. Illinois Natural History Survey Bulletin 33, 4 (1985), pp. 335-448.
  14. ^ Reid L. Morehouse Michael Tobler : Crayfishes (Decapoda: Cambaridae) of Oklahoma. Identification, distributions, and natural history . In: Zootaxa 3717, 2 (2013), pp. 101–157.
  15. ↑ Horton H. Hobbs Jr .: Two New Species of Crayfishes of the Genus Cambarellus from the Gulf Coastal States, with a Key to the Species of the Genus (Decapoda, Astacida). American Midland Naturalist, 34, 2, pp. 466-474, 1945
  16. ↑ 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.
  17. ↑ 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.
  18. ↑ 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.
  19. ↑ Franklin Sogandares-Bernal: Micro phallus progeneticus, a new Apharyngeate Progenetic trematode (Microphallidae) from the Dwarf Crayfish, Cambarellus puer , in Louisiana . In: Tulane Studies in Zoology 9, 5 (1962) pp. 319-322.
  20. ↑ Zen Faulkes : The global trade in crayfish as pets . In: Crustacean Research 44 (2015), pp. 75-92.
  21. ↑ a b c d Christian Splettstößer, Volker Eßer: Cambarellus puer. The boy cancer . In: Garnele online , Edition 1, 2007, pp. 4-6; here: p. 4.
  22. ^ Federal Ministry of Justice and Consumer Protection / Federal Office of Justice: Animal Protection Act.
  23. ↑ Federal Act on the Protection of Animals (Animal Protection Act - TSchG)
  24. ^ Animal Welfare Act of December 16, 2005 (TSchG)
  25. ↑ Cancers feel pain too. In: Scinexx. The knowledge magazine.
  26. ↑ Hans A. Baensch , Hans-Georg Evers : Aquarien Atlas Volume 6, Mergus, Melle 2002, ISBN 3-88244-068-6 .
  27. ↑ a b c d Jakob Geck, Ulrich Schliewen: Nano aquariums. Wonder world in mini format up to 35 liters. , Gräfe and Unzer, Munich 2017, ISBN 978-3-8338-5516-0 , p. 40.