Tanypus Meigen

Description

Introduction

Large larvae, 10-12 mm long. Body pink in life. Occipital margin and apical mandible usually dark. Head capsule rounded oval; cephalic index about 0.95. Dorsally, S5 anterior, level or posterior to S8; S8 distant from S7, close to DP. Ventrally, S9 and S10 aligned antero-posteriorly, both anterolateral to SSm, VP far lateral and slightly posterior to SSm. S5 apparently simple, S7 simple, S8 multibranched, S9 strong, 1-2 -branched, S10 2-multibranched, SSm apparently simple or multibranched.

Antenna

About 1/4 longer than mandible. Antennal ratio 5-8. Basal segment about 5x as long as basal width, with ring organ at 0.6-0.7; segment 2 very variable in length, 1. 5-4.5x as long as wide; segment 3 about as long as wide, shorter than segment 4; basal 1/2 of last segment with thickened wall. Style extending to apical margin of segment 3 or somewhat beyond, seated together with peg sensilla at sides, below apical margin of segment 2. Blade as long as flagellum or only slightly shorter.

Mandible

Short, compressed, with strong basal, ventral articular projection. Apical tooth 2x as long as basal width, about 1/5 length of mandible; middle section of inner margin with 2 long, flat teeth, one after another, with 2 adjacent equal-sized, pointed accessory teeth; mola quite protruding, bilobed apically, seta subdentalis arises at base from pit, fringed by sharp edge. Ventrolateral setae 1 and 3 simple, seta 2 with 1-3 branches, with ring organ well lateral of linearly-aligned setae 1-3; SIII rather distant from SI and SII.

Maxilla

Basal segment of palp about 2.0-2.5x as long as wide, apically narrowed and sloping, situated on slanting, sclerotized ring, with ring organ 0.7-0.8.

Body

With fringe of swim-setae. With 4 or 6 anal tubules; sometimes anal tubules absent. Procercus 4-5x as long as wide, with 14-16 apical setae, 6 or 7 shorter than remainder. Posterior parapod with about 15 claws; long claws very slender distally and scarcely curved, in part finely serrate along on inner and outer side; 1-3 of smaller claws with species-specific shapes.

Notes

Taxonomic Notes

Tanypus shows no close relationship with other Tanypodinae, and is placed in a monotypic tribe Tanypodini. The structure of the mentum, absence of pseudoradula, form of mandible and maxilla and reduced pecten hypopharyngis separates Tanypus from all other genera. On the basis of imaginal characters, Roback (1971) divided Tanypus into 2 subgenera, the worldwide Tanypus s. str. and the Nearctic Apelopia, which cannot be separated yet in the larval stage. Amongst the Nearctic species, distinction between T. neopunctipennis - recorded from the eastern Nearctic Region and southern Mexico (Roback, 1971) - and the western Nearctic T. grodhausi is unclear, as rearings from southern California key to one or the other depending on the life stage (Spies and Reiss, 1996). The finding by Niitsuma (2001) that the near identical adults of T. punctipennis and T. formosanus have differentiated immature stages implies that adult morphology may underestimate true diversity.

Keys

Epler (2001) keys six species and provides ecological notes for species from s.e. USA.

Ecological Notes

Tanypus larvae live in sediments in standing and slowly flowing waters, especially in temperate to warm regions, where they can tolerate high nutrient and salinities. Nearctic Tanypus nubifer is a salinity indicator distributed from western Canadian lakes to Mexico, and other species may do likewise in Africa. Larvae of Tanypus prey on and suck out the body fluids of other chironomid larvae (Roback 1977), but also ingest a great deal of plant material, especially desmids.

The genus is worldwide in distribution. Roback (1971) recorded 11 species for North America. Five species are recognised from the Palaearctic: T. punctipennis is widespread in the Holarctic, while T. kraatzi and T. vilipennis are western Palaearctic. Tanypus chinensis and T. formosanus are eastern Palaearctic/Oriental. Three named species have been recorded in Central America (Spies and Reiss, 1996); 6 are reported from South America including T. punctipennis but the taxonomy of this and many other regional species described in Tanypus, is unclear. An unidentified larva occurs in tropical/monsoonal northern Australia.

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