Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

– We present an updated classification for the entire Crustacea Decapoda, listing all known families and genera organized by higher taxonomic groups and including estimates of the number of species in every genus. All taxonomic names are also linked to the verified literature in which they were described, the first compilation of its kind for the Decapoda. To arrive at this compilation, we began with the classification scheme provided by Martin & Davis (2001) for extant families, updated the higher classification and included the fossil taxa. The resultant framework was then populated with the currently valid genera and an estimate of species numbers within each genus. Our resulting classification, spanning both extant (living) and fossil taxa, is the first comprehensive estimate of taxonomic diversity within the entire Decapoda. The classification consists of 233 families of decapods containing 2,725 genera and an estimated 17,635 species (including both extant and fossil species). Of the families in our classification, 53 are exclusively fossil, 109 contain both fossil and extant species, and 71 are extant only. The current estimate for extant species is 14,756, whereas 2,979 species are known exclusively as fossils.

A Classification of Living and Fossil Genera of Decapod Crustaceans

https://commons.nmu.edu/cgi/viewcontent.cgi?article=1038&context=facwork_journalarticles

Freshwater crabs and the biodiversity crisis: Importance, threats, status, and conservation challenges

An assessment of the global freshwater crab diversity is presented. A total of 1,476 species in 14 families are currently known from all zoogeo- graphical regions (except Antarctica), including 1,306 species in eight exclusively freshwater families (Pseudothelphusidae, Trichodactylidae, Potamonauti- dae, Deckeniidae, Platythelphusidae, Potamidae, Gecarcinucidae and Parathelphusidae). Estimates of true freshwater crab diversity including likely num- bers of undescribed taxa suggest that the field remains largely in a ''discovery'' phase. Main ideas on the origins, diversification, and phylogeny of true fresh- water crabs are briefly discussed. The economic importance of freshwater crabs is also highlighted.

/pdf/global-diversity-of-crabs-crustacea-decapoda-brachyura-in-5cjtbddv39.pdf

Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater

Crabs of the infra-order Brachyura are one of the most diverse groups of crustaceans with approximately 7,000 described species in 98 families, occurring in marine, freshwater, and terrestrial habitats. The relationships among the brachyuran families are poorly understood due to the high morphological complexity of the group. Here, we reconstruct the most comprehensive phylogeny of Brachyura to date using sequence data of six nuclear protein-coding genes and two mitochondrial rRNA genes from more than 140 species belonging to 58 families. The gene tree confirms that the "Podotremata," are paraphyletic. Within the monophyletic Eubrachyura, the reciprocal monophyly of the two subsections, Heterotremata and Thoracotremata, is supported. Monophyly of many superfamilies, however, is not recovered, indicating the prevalence of morphological convergence and the need for further taxonomic studies. Freshwater crabs were derived early in the evolution of Eubrachyura and are shown to have at least two independent origins. Bayesian relaxed molecular methods estimate that freshwater crabs separated from their closest marine sister taxa ~135 Ma, that is, after the break up of Pangaea (∼200 Ma) and that a Gondwanan origin of these freshwater representatives is untenable. Most extant families and superfamilies arose during the late Cretaceous and early Tertiary.

/pdf/evolutionary-history-of-true-crabs-crustacea-decapoda-3g5suf80i8.pdf

Evolutionary History of True Crabs (Crustacea: Decapoda: Brachyura) and the Origin of Freshwater Crabs

Taxonomy and zoogeography of the freshwater crabs of Europe, North Africa, and the Middle East (Crustacea, Decapoda, Potamidae)

Commensal pea crabs inhabiting bivalves have a high reproductive output due to the extension and fecundity of the ovary We studied the underlying morphology of the female reproductive system in the Pinnotheridae Pinnotheres pisum, Pinnotheres pectunculi and Nepinnotheres pinnotheres using light microscopy and transmission electron microscopy (TEM) Eubrachyura have internal fertilization: the paired vaginas enlarge into storage structures, the spermathecae, which are connected to the ovaries by oviducts Sperm is stored inside the spermathecae until the oocytes are mature The oocytes are transported by oviducts into the spermathecae where fertilization takes place In the investigated pinnotherids, the vagina is of the "concave pattern'' (sensu Hartnoll 1968): musculature is attached alongside flexible parts of the vagina wall that controls the dimension of its lumen The genital opening is closed by a muscular mobile operculum The spermatheca can be divided into two distinct regions by function and morphology The ventral part includes the connection with vagina and oviduct and is regarded as the zone where fertilization takes place It is lined with cuticle except where the oviduct enters the spermatheca by the "holocrine transfer tissue'' At ovulation, the oocytes have to pass through this multilayered glandular epithelium performing holocrine secretion The dorsal part of the spermatheca is considered as the main sperm storage area It is lined by a highly secretory apocrine glandular epithelium Thus, two different forms of secretion occur in the spermathecae of pinnotherids The definite role of secretion in sperm storage and fertilization is not yet resolved, but it is notable that structure and function of spermathecal secretion are more complex in pinnotherids, and probably more efficient, than in other brachyuran crabs J Morphol 272: 12-26, 2011 (C) 2010 Wiley-Liss, Inc

Morphology of the Female Reproductive System of European Pea Crabs (Crustacea, Decapoda, Brachyura, Pinnotheridae)

https://research.nhm.org/pdfs/31279/31279.pdf

Phylogeny, biogeography and a new taxonomy for the Gecarcinucoidea Rathbun, 1904 (Decapoda: Brachyura)

To understand the reproductive processes of freshwater crabs of the genus Potamon, we examined the first and second gonopod and the gonoducts of the female by histological methods. The gonopods are highly modified compared to those of other brachyuran crabs. In particular, the second gonopod is unusually long and has a special morphology, ending in a long sclerotized tube. Suggestions for the function of both gonopods and their different parts are presented. Tubulation of the first and second gonopod is observed. Rosette glands, which are abundant in the subterminal joint of the first gonopod, are connected to the sperm channel by cuticular pores. In females, the chitinous parts of the inner vulva may prove to have a more constant morphology than the external flexible structures. J. Morphol. 239:157–166, 1999. © 1999 Wiley-Liss, Inc.

Dirk Brandis

Papers

Taxonomy and zoogeography of the freshwater crabs of Europe, North Africa, and the Middle East (Crustacea, Decapoda, Potamidae)

Morphology of the Female Reproductive System of European Pea Crabs (Crustacea, Decapoda, Brachyura, Pinnotheridae)

Phylogeny, biogeography and a new taxonomy for the Gecarcinucoidea Rathbun, 1904 (Decapoda: Brachyura)

Morphology and function of the copulatory system in freshwater crabs of the genus Potamon.

Phylogeny and Biogeography of Asian Freshwater Crabs of the Family Gecarcinucidae (Brachyura: Potamoidea)