A new species of the genus Siambathynella Camacho, Watiroyram & Brancelj, 2011 (Crustacea, Bathynellacea, Parabathynellidae) from a Thai cave

Abstract

Siambathynella janineana sp. nov. (family Parabathynellidae) discovered in Thailand is herein described. The new species displays an exclusive character: a distinctive organ on the antennule of males. It also displays a unique combination of morphological characters, including a seven-segmented antennule and antenna, sexual dimorphism of the antennule, a one-segmented exopod on thoracopod I and a two-segmented one on thoracopods II to VII, a male thoracopod VIII without basipodial setae and with a trapezoidal outer lobe, a female thoracopod VIII with two denticles at the base of two setae, pleopods absent, a sympod of the uropod with an inhomonomous row of spines and an uropod endopod with a spinous distal process and a very large distal spine covered with setules. This is the fifth record of Bathynellacea (family Parabathynellidae) found in caves in Thailand.