Order BATHYNELLACEA Chappuis, 1915

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Introduction

Bathynellaceans are small interstitial crustaceans. Most are from ground water, a few are from sediments in lakes, and members of one genus are found in interstitial beach sands from low salinity to fully saline. They have a vermiform shape, no eyes and simple appendages typical of many interstitial forms; the largest species is 3.4 mm long. The method of reproduction is uncertain but the female lays 1 or 2 large eggs.

The group occurs worldwide. Most of the early literature of the Bathynellacea is written in German but Schminke (1982) and Schram (1986) have provided diagnoses and discussions of biology. The diagnosis here uses these and also that of Coineau (1996). Schminke (1973) recognised two families, both recorded from Australia. He also discussed at length the evolution and biogeography of the Parabathynellidae in particular. Comacho (2006) listed 235 species, a figure since exceeded, and half as many again as the 150 species listed by Schminke (1986) 20 years earlier. Coineau (1996) and Lopretto & Morrone (1998) listed 52 genera, all extant, but the figure is now over 70 genera.

Diagnosis

Thoracomere 1 free from cephalon. Pleonites 1-5 separate; pleonite 6 fused to telson; pleotelson with furca. Eyes absent. Antenna 1 inner flagellum minute, with 3 setae. Antennal statocysts absent. Mandibles symmetrical, left incisor fused to an accessory process. Paragnaths present or absent. Thoracopods 1-7 with endopod up to 4-articled, with exopod; thoracopod 8 transformed as copulatory organ in male, more or less reduced in female; epipods present on thoracopods 1-5 or 1-6. Seminal receptacle absent in female. Pleopods 1 and 2 often present, of male not forming a petasma. Uropods not forming a tailfan with telson. Without spermatophores. Seminal receptacle present in female.

General References

Camacho, A.I. 2006. An annotated checklist of the Syncarida (Crustacea, Malacostraca) of the world. Zootaxa 1374: 1-54

Chappuis, P.-A. 1915. Bathynella natans und ihre Stellung im System. Zoologische Jahrbücher. Abteilung für Systematik 40: 147-176

Coineau, N. 1996. Sous-classe des Eumalacostracés (Eumalacostraca Grobben, 1892) Super-ordre des syncarides (Syncarida Packard, 1885). pp. 897-954 in Forest, J. (ed.). Traité de Zoologie. Anatomie, Systématique, Biologie. Publié sous la direction de Pierre-P. Grassé. Tome VII. Crustacés. Fascicule 2. Généralités (suite) et systématique (Céphalocarides à Syncarides). Paris : Masson éditeur 1002 pp.

Lopretto, E.C. & Morrone, J.J. 1998. Anaspidacea, Bathynellacea (Crustacea, Syncarida), generalised tracks, and the biogeographical relationships of South America. Zoologica Scripta 27: 311-318

Schminke, H.K. 1973. Evolution, System und Verbreitungs geschichte der Familie Parabathynellidae (Bathynellacea, Malacostraca). Mikrofauna des Meeresbodens 24: 1-192

Schminke, H.K. 1982. Syncarida. pp. 233-237 in Parker, S.P. (ed.). Synopsis and classification of living organisms. New York : McGraw-Hill Vol. 2.

Schram, F.R. 1986. Crustacea. New York : Oxford University Press xii 606 pp.

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