Wednesday, November 4, 2015

[Crustacea • 2015] Aletheiana tenella • A New Genus and New Species of Freshwater hymenosomatid Crab (Decapoda: Brachyura) from Central Sulawesi, Indonesia


Aletheiana tenella
Ng, & Lukhaup, 2015
FIGURE 1. Aletheiana tenella gen. et sp. nov.. A, cascades at Puawu River, central Sulawesi, B, submerged roots at the riverbank of Puawu River where the specimens were collected; CF, colour in life.

Abstract 
A new genus and new species of free-living hymenosomatid crab, Aletheiana tenella, is described from Central Sulawesi, Indonesia. The two known Sulawesi hymenosomatid species, Cancrocaeca xenomorpha Ng, 1991, and Sulaplax ensifer Naruse, Ng & Guinot, 2008, are both from cave habitats. Aletheiana gen. nov. is most similar to Neorhynchoplax Sakai, 1938 (from freshwater and intertidal habitats in the Indo-West Pacific), and Sulaplax, but can be distinguished by its front possessing only one subventral rostral lobe, the base of the antenna is positioned between the base of the ocular peduncle and antennular fossa, the posterior margin of the epistome has two low, rounded median lobes, the merus of the third maxilliped is elongated, the ambulatory dactylus has a prominent subdistal spine, the cutting edges of the chela are armed with distinct teeth proximally, and the male abdomen is slender and elongate with the telson linguiform.

Key words: Hymenosomatidae, Aletheiana tenella, new genus, new species, taxonomy, Sulawesi

Etymology. Aletheia” is an ancient-Greek word for disclosure and a state of not being hidden. The latinised name is used here as a genus, alluding to the present discovery of the first free-living hymenosomatid crab from Sulawesi. Gender of genus feminine. The name is derived from the Latin “tenellus” for delicate; alluding to the small size and slender appendages of the species.

Biology. Aletheiana tenella gen. et sp. nov. was found among the submerged fibrous roots of trees at the slow flowing parts of the riverbank near cascades along the Puawu River, in Central Sulawesi (Fig. 1A, B). The crabs were observed at the slow flowing parts of the riverbank among roots near cascades of the Puawu River. The water at the time of collection was muddy and had a temperature of 22°C. In the faster flowing parts of the river, no crabs were found. This is a typical habitat for many free-living hymenosomatids (e.g., see Naruse & Ng 2007). A new species of Caridina, C. boehmei (Atyidae) was also recently described from the type locality of Aletheiana tenella gen. et sp. nov. by Klotz & von Rintelen (2013).

Ng, Peter K. L. and Christian Lukhaup. 2015. Aletheiana tenella, A New Genus and New Species of Freshwater hymenosomatid Crab (Crustacea: Decapoda: Brachyura) from Central Sulawesi, Indonesia. Zootaxa. 4039(1): 118–128. DOI: 10.11646/zootaxa.4039.1.4

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