Cancrocaeca

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.

Abstract: Sulaplax gen. nov. and Guaplax gen. nov. are established for two new species of cave-dwelling false spider crabs (Hymenosomatidae) from Muna Island, Sulawesi Tenggara, and Kalimantan Timur, Indonesia, respectively. Sulaplax ensifer spec. nov. and Guaplax denticulata spec. nov. are distinguished from each other by carapace, rostral, pereopodal, abdominal and male gonopodal characters. Sulaplax and Guaplax share with Cancrocaeca Ng, 1991, another troglobitic hymenosomatid, cave-adapted characters like reduced eyes, pale coloration and slender ambulatory legs. However, the gonopods, abdomens and egg-brooding features of Sulaplax and Guaplax are closer to those of the epigeal Neorhynchoplax Sakai, 1938, whereas those of Cancrocaeca are closer to those of the epigeal Limnopilos Chuang & Ng, 1991, and Hymenicoides Kemp, 1917. It appears that the hypogeal lifestyles of Sulaplax-Guaplax and Cancrocaeca species have resulted in many convergent characters.