Family HAPLOTAXIDAE Michaelsen, 1900

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Family HAPLOTAXIDAE Michaelsen, 1900

Compiler and date details

Adrian M. Pinder

Haplotaxidae Michaelsen, W. 1900. Oligochaeta. Das Tierreich 10: 1-565 [107].
Type genus:
Haplotaxis Hoffmeister, 1843.
Phreoryctidae Claus, C. 1880. Grundzüge der Zoologie. Marburg : N.G. Elwert'sche Univ. Vol. 1 482 pp.

Taxonomic Decision for Synonymy

Michaelsen, W. 1900. Oligochaeta. Das Tierreich 10: 1-565 [107]

Brinkhurst, R.O. 1988. A taxonomic analysis of the Haplotaxidae (Annelida, Oligochaeta). Canadian Journal of Zoology 66: 2243-2252 [2250]

Introduction

This family of about 20 earthworm-like oligochaetes, together with the monospecific Tiguassuidae, are believed by some (Brinkhurst 1984) to be direct descendents of an ancestral form of oligochaete, though this is not a universal view (Timm 1981). The lack of a unique apomorphy for the family certainly is certainly consistent with the 'ancestral' hypothesis, but suggests that the grouping of these in a single family is artifactual (Jamieson 1988). Most species inhabit semi-terrestrial (e.g. river banks) or subterranean (caves, groundwater, hyporheic zones) habitats, though haplotaxids are occasionally found in surfacial sediments of lakes and streams. The type genus, Haplotaxis, consists of a small number of predatory worms which have a particularly muscular gizzard-like pharynx and large sickle-shaped ventral chaetae for grasping prey and is represented in Australia by H. heterogyne. Only one haplotaxid, Hologynus ornamentus Br. & Fulton (1980), described from deep Tasmanian lakes, is endemic, and the rest have been identified from very few specimens.

Diagnosis

Mostly aquatic oligochaetes superficially resembling earthworms (Opisthopora). Genitalia consisting of one or two pairs of testes and one or two pairs of ovaries, in two to four successive segments (unlike earthworms which normally have a segment between the testes and ovary-bearing segments without gonads). Genital ducts leading from each gonadal segment to pores on the next posterior segment (plesioporous). As in the Lumbriculida and Tubificida, but unlike earthworms, the clitellum is just one cell thick. Four pairs of simple-pointed chaetae per bundle.