Bathynellacea

Abstract: This study aims at demonstrating that the Bathynellacea arose by neoteny from a zoea-like ancestor (“Zoea Theory”). Bathynellacea basically have a larval morphology. Their post-embryonic development passes through phases which are directly comparable with some in the development of primitive Eucarida. These phases are called the parazoeal and bathynellid phase, and correspond to the protozoeal and zoeal phase of Penaeidea, respectively. Running initially parallel to that of Penaeidea, the development of the Bathynellacea breaks off precociously. They reach sexual maturity at a stage which, in the Penaeidea, is followed by metamorphosis. There are reasons to assume that the development of all Syncarida originally passed through a series of free-living larval stages and underwent metamorphosis. The bathynellaceans reach adulthood at a stage which corresponds to the last larval stage of their ancestor. The ecological path to interstitial life of the Bathynellacea and the bearing of the “Zoea Theory” upon views as to their phylogenetic position are discussed. The classical example of a group of crustaceans thought to have arisen by neoteny, the Cladocera, is critically examined and found to be in need of reevaluation.

Abstract: Four new species of the parabathynellid genus Nipponbathynella Schminke, 1973 are described from South Korea (Nipponbathynella leesookyungae sp. nov., Nipponbathynella donggangensis sp. nov. and Nipponbathynella wanjuensis sp. nov.) and Japan (Nipponbathynella shigaensis sp. nov.), raising the number of known species to seven. Nipponbathynella leesookyungae is characterized by the convex ventral surface of the labrum and the rich ornamentation (with three spinules and two teeth) of the exopod of male thoracopod VIII; N. donggangensis by the distal spine on the distal maxillular segment with many dentils; N. wanjuensis by the endopod of the male thoracopod VIII with one seta (instead of two) and the serrated endopodal spur of the uropod; and N. shigaensis by the basipod of thoracopods II–VII carrying strong hairs on their outer margin. The three new and one known (Nipponbathynella pectina) South Korean species share a bur-like inner lobe of the male thoracopod VIII, suggesting their close relationship. Bas...

Abstract: The genus Habrobathynella Schminke, 1973, comprises 14 species: two from Madagascar and 12 from the peninsular India. Two more new hyporheic species of this genus, viz. H. muvattupuzha n. sp. and H. adishankara n. sp., from the southwestern peninsular India, are described and illustrated, and their position in the genus is discussed. Both new species are more closely related to each other than to their hitherto known congeners. H. muvattupuzha n. sp. has a unique combination of characters: male Th VIII small in size, with protopod distinctly expanded latero-externally, and basipod balloon-shaped; uropodal sympod with inhomonomous row of five spines, with penultimate spine longer and thicker than others, and ultimate spine same as proximal spines; paragnaths with minaret-like smooth coupler and short lateral lobes; fifth antennular segment with only two long aesthetascs; and first maxillary segment with two setae. H. adishankara n. sp. is distinct from its congeners in having a unique set of characters: uropodal sympod with inhomonomous row of six spines, with penultimate and ultimate spines as in the preceding species; paragnaths with thumb-like, smooth coupler and small lateral lobes; first antennary segment nearly as long as the second one; fifth antennular segment with three long aesthetascs; and first maxillary segment with one seta. The principal morphological characters and their states among the Habrobathynella species, with special reference to the new species, are briefly discussed. Also, brief notes on the ecology and biogeography are given, as is an updated key to Habrobathynella species.

Abstract: Indobathynella socrates n. sp. is described from Karaiguda Cave in the Visakhapatnam District of Andhra Pradesh state, south-eastern India. This is the first cavernicolous species of Indobathynella , which is incidentally the most reduced genus in the family Bathynellidae as a whole. The type species of this genus, Indobathynella prehensilis , is from a farm bore. The new species fulfils all the principal generic criteria of Indobathynella , but is distinctly different from I . prehensilis in several essential features: absence of subapical seta on antennary exopod; 4 claws on distal maxillulary endite; 6 teeth on mandibular gnathobase, and uropodal exopod without ventro-medial seta. These and all other salient differences between the two species are tabulated. Besides providing brief notes on conservation and biogeography of the new species, a key to all the known Indian taxa of Bathynellidae is given for the first time.