Dwarf crayfish

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Dwarf crayfish
Striped pygmy crayfish (Cambarellus patzcuarensis) in an orange color morph

Striped pygmy crayfish ( Cambarellus patzcuarensis ) in an orange color morph

Systematics
Order : Decapods (decapoda)
Subordination : Pleocyemata
Partial order : Large crayfish (Astacidea)
Superfamily : Crayfish (Astacoidea)
Family : Cambaridae
Genre : Dwarf crayfish
Scientific name
Cambarellus
Ortmann , 1905

The dwarf crayfish ( Cambarellus ) are a genus in the family Cambaridae . The 17 species live in the fresh water of the Mexican plateau, along the North American Gulf coast and - in the case of Cambarellus puer - from the Texas counties Brazos and Brazoria in the west to the Mississippi basin and southern Louisiana and north to Illinois (Johnson County).

features

The dwarf crayfish were often overlooked by researchers because of their small size or could not be caught in the wide-meshed nets or pots . They reach a maximum length of 4 centimeters for females and 3 centimeters for males. They are therefore only comparable in size with the smallest species of the other genera within their family, such as Procambarus youngi or Orconectes clypeatus .

The limbs of the first abdomen segment of the male are formed into a pair of gonopodia . The gonopodia have processes that can be used to differentiate the species. Typical of the genus are also small thorn-shaped hooks on the base element of the male's striding legs. These are used to hold the females in place during copulation . In contrast to the other genera of the Cambaridae family, such ischium hooks are found in the dwarf crayfish on the second and third pair of striding legs. The sperm store ( annulus ventralis ) of the females and the matching sperm groove of the males are also characteristic of the genus.

Taxonomy

genus

The genus Cambarellus was initially established in 1905 by Arnold Edward Ortmann as a sub-genus of the genus Cambarus . Ortmann thus followed a list by Walter Faxon , who in 1885 had divided the genus Cambarus into five groups according to the characteristics of the males' walking legs. In the fifth group were the Montezuma dwarf crayfish , which had already been described by Henri de Saussure as Cambarus Montezumae in 1857 and is today the type species of the genus Cambarellus , as well as the Louisiana dwarf crayfish , then described as Cambarus Shufeldti by Faxon himself. He noticed that these two species were the only ones within the genus Cambarus that did not have hooks on the third or fourth strider leg, but on the second and third. Faxon had put a Mexican species and one from the United States in the same group. Ortmann was able to add a third to these two species, namely Cambarus chapalanus , which had meanwhile been described by Faxon. In 1942, Horton H. Hobbs Jr. raised the subgenus Cambarellus to the genus.

Subgenera

The division into three subgenera was carried out in 1983 by JF Fitzpatrick Jr. He assumed that the radiation of the individual species began before the Miocene in the southern Mississippi basin. Fossil finds also seem to confirm this. This results in the geographical distribution of the sub-genera. In Mexico only the derived forms of the nominotypical subgenus Cambarellus are native. The subgenus Pandicambarus , which is characterized by original characteristics, occurs exclusively in the USA . The subgenus Dirigicambarus is monotypical , that is, it includes only one species, the Louisiana pygmy crayfish ( Cambarellus shufeldtii ). This species lives sympatric with other species, for example the boy cancer ( Cambarellus puer ). The simultaneous occurrence of different species in the same area could have resulted from the migration of a species back in the late Miocene or early Pliocene , i.e. at a time interval of around 18 million years.

Subgenus Cambarellus (Cambarellus)
Subgenus Cambarellus (Dirigicambarus)
Subgenus Cambarellus (Pandicambarus)
Cambarellus diminutus

behavior

Dwarf crayfish behave territorially. They create shelter in their area by digging in sand and gravel or by weaving parts of plants together.

Individual evidence

  1. ↑ Keith A. Crandall, James W. Fetzner Jr. and Horton H. Hobbs Jr .: Genus Cambarellus . Tree of Life web project, 2001
  2. ↑ 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
  3. ^ Arnold Edward Ortmann: The mutual affinities of the species of the genus cambarus, and their dispersal over the United States. Proceedings of the American Philosophical Society held at Philadelphia for promoting useful knowledge, XLIV, 1905, pp. 106-107
  4. ^ Walter Faxon: A revision of the Astacidæ. Memoirs of the Museum of Comparative Zoology at Harvard College, X, 4, 1885
  5. ↑ Horton H. Hobbs Jr .: A Generic Revision of the Crayfishes of the Subfamily Cambarinae (Decapoda, Astacidae) with the Description of a New Genus and Species. American Midland Naturalist, 28, 2, pp. 334-357, 1942
  6. ↑ JF Fitzpatrick Jr .: A Revision of the Dwarf Crawfishes (Cambaridae, Cambarellinae). Journal of Crustacean Biology, 3, 2, pp. 266-277, 1983
  7. ^ ITIS - Standard Report Page: Cambarellus (Cambarellus) Ortmann, 1905
  8. ^ ITIS - Standard Report Page: Cambarellus (Dirigicambarus) Fitzpatrick, 1983
  9. ^ ITIS - Standard Report Page: Cambarellus (Pandicambarus) Fitzpatrick, 1983

literature

  • 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

  • Keith A. Crandall, James W. Fetzner Jr. and Horton H. Hobbs Jr .: Genus Cambarellus , Tree of Life web project, 2001