Lithotanytarsus Thienemann

Description

Introduction

Small larvae, to 5 mm long.

Dorsal Head

Not described.

Antenna

Antenna with 5 segments on low pedestal lacking any basal tooth or spur, but with 2 short conical processes mesally. Antennal ratio > 1.0. Ring organ basal on 1st antennal segment; seta long, in proximal 1/2. Lauterborn organs large, sessile, opposite on apex of cylindrical 2nd segment. Antennal blade extending to apex of flagellum, accessory blade absent. Style on apex of 2nd segment shorter than segment 3.

Labrum

SI seta comb-like, fused at base, SII on large pedestal, distally plumose, SIII short, simple, SIV present. Labral lamellae well developed. Pecten epipharyngis comprising 3 very small finger-like lobes. Premandible distally bifid, outer tooth slender, pointed, inner broad, distally rounded, brush strong; seta premandibularis simple.

Mandible

Mandible with dorsal tooth, apical tooth and 2 pointed inner teeth yellow-brown. Seta subdentalis long, curved, reaching to tip of apical tooth. Seta interna of 4 plumose branches. Pecten mandibularis well developed with about 7 lamellae.

Mentum

Mentum pale, with rounded median tooth with 5 pairs of laterals, regularly decreasing in size. Ventromental plates close together medially, slightly wider than mentum.

Body

Setation apparently simple in contrast to other members of the tribe Tanytarsini. Without tubules. Claws of posterior parapod numerous, all simple.

Notes

Taxonomic Notes

The form of the pecten epipharyngis places this genus close to Paratanytarsus, although in Lithotanytarsus the structure is very small and difficult to see. However, details of the antenna, very long blade and antennal seta, together with the conical projections on antennal pedestal in Lithotanytarsus enable them to be easily distinguished.

Ecological Notes

Larvae of Lithotanytarsus inhabit limestone rich streams, chiefly in mountainous regions, where they encrust rocks with their characteristic tubes of tufa (calcareous deposits).

The genus has a palaearctic distribution. Only 1 species is known (L. emarginatus Goetghebuer).

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