[Crustacea • 2017] Parasesarma gazi • A New Species of the Genus Parasesarma De Man 1895 (Decapoda: Sesarmidae) from East African Mangroves and Evidence for Mitochondrial Introgression in Sesarmid Crabs

Parasesarma gazi 

Cannicci, Innocenti & Fratini, 

in Cannicci, Schubart, Innocenti, Dahdouh-Guebas, Shahdadi et Fratini, 2017

 DOI: doi.org/10.1016/j.jcz.2017.08.002 

 Researchgate.net/publication/319023850

Abstract

The Sesarmidae (Decapoda; Brachyura: Thoracotremata) is the most speciose family of crabs occurring in the mangroves of East Africa, accounting for 12 species belonging to seven genera. Among these, the genus Parasesarma accounts for a total of four species. Here we describe a new species, Parasesarma gazi sp. nov., based on specimens collected in mangrove forests of Kenya and Tanzania. The phylogenetic position of this new species within the family Sesarmidae was reconstructed, based on three mitochondrial and one nuclear marker. While nuclear data genetically resolve the systematic relationships, mitochondrial data reveal a surprising similarity of Parasesarma gazi sp. nov. and its sister species P. leptosoma. This result may reflect a short history of reproductive isolation or recent mitochondrial introgression between these two species. This is the first time that such an evolutionary event is reported for the family Sesarmidae and for mangrove crabs, in general.

Keywords: Hybridization, Mitochondrial DNA, Nuclear marker, Sesarmidae, Speciation, Molecular phylogeny, Taxonomy

Parasesarma gazi sp. nov. life colours (A), paratype male (14.2 × 11.7 mm) (MZUF 3678); upper view (B).
Parasesarma leptosoma (Hilgendorf, 1869), upper view (C)

Scale bars = 5 mm.

FAMILY SESARMIDAE DANA, 1851

GENUS PARASESARMA, DE MAN, 1895 

PARASESARMA GAZI Cannicci, Innocenti and Fratini sp. nov.

Sesarma (Parasesarma) lenzii De Man 1894.

  Etymology: The name of this new species, Parasesarma gazi, is derived from Gazi Bay (also named Maftaha Bay) and the village of Gazi, on the South coast of Kenya. In Arab, gazi or ghazi is the active participle of the verb gaza ‘to strive for’ or also ‘the one who struggles’. The new species is dedicated to the people of Gazi village and to the staff of the Gazi Mangrove Research Station of KMFRI, since without their help the largest known population of this new species would never have been found. We also believe that ‘the one who struggles’ correspondingly applies to mangrove crabs and their challenging adaptations to intertidal life, and that they are ‘key’ in mangrove ecosystems. The specific name is used as a noun in apposition.

Ecology: At all three sites, Parasesarma gazi sp. nov. was found in the Rhizophora mucronata Lamk, 1804 dominated belt of the mangrove forest, on the muddy floor. Only the specimens collected at Gazi Bay were collected on the lower part of R. mucronata roots, and there was no evidence of climbing behavior, such as in P. leptosoma. In all cases, they were found in areas where the by far dominant crab species was P. guttatum, with which they were mixing and totally overlapping. 

  Stefano Cannicci, Christoph D. Schubart, Gianna Innocenti, Farid Dahdouh-Guebas, Adnan Shahdadi and Sara Fratini. 2017. A New Species of the Genus Parasesarma De Man 1895 from East African Mangroves and Evidence for Mitochondrial Introgression in Sesarmid Crabs.  Zoologischer Anzeiger - A Journal of Comparative Zoology. 269; 89-99. DOI: doi.org/10.1016/j.jcz.2017.08.002

 Researchgate.net/publication/319023850_A_new_species_of Parasesarma_from_East_African_mangroves