Tanytarsus, Wulp, 1874

Cranston, Peter S., 2007, The Chironomidae Larvae Associated With The Tsunami-Impacted Waterbodies Of The Coastal Plain Of Southwestern Thailand, Raffles Bulletin of Zoology 55 (2), pp. 231-244 : 237

Tanytarsus v.d. Wulp

( Figs. 20, 22–24 )

Tanytarsus is a worldwide genus with many species, with taxonomy based especially on the complex male genitalia, on diagnostic pupal exuvial spine and spinule patterns. Larvae are much more difficult to distinguish, and in every region studied, there is a mismatch between the number of larval types recognised and the substantially greater total number of species present.

One readily-recognisable species, T. formosanus Kieffer , occurs throughout regional standing waters. The species identity is confirmed by pharate pupae (that is, with characteristic pupal abdominal patterning visible within the late 4 th instar larva) and some pharate adults, with male genitalia visible within pupae. The larva conforms to that described by Ekrem (2001), who resolved the convoluted taxonomy and nomenclature of this widespread Old World species. As elsewhere, the larvae of T. formosanus in Thailand exhibit wide environmental tolerance, occurring in tsunamiimpacted and unimpacted ponds, including disturbed and undisturbed peat swamps. Maximum conductivities tolerated were as high as 7,800 µS. cm−1 with dissolved solids of 3,900 ppm, in impacted sites in which the species can be common and persistent across the survey period. Unassociated larvae likely to be conspecific based on basic morphology are also present in dilute water.

Two further types of larval Tanytarsus can be distinguished by the relative lengths and pigmentation pattern of the antennal segments and by differences in the relative and absolute length of the Lauterborn organs stems. A species with very long stems to the Lauterborn organs ( Fig. 23 ), here termed ‘Thai sp. 1’ occurs sporadically in dilute water bodies with conductivity of 43–260 µS. cm−1 and dissolved solids of 22–120 ppm. A third larval morphotype ‘Thai sp. 2’ with intermediate lengthened stems to the Lauterborn organs ( Fig. 24 ) occurs in both unimpacted dilute (44–100 µS. cm−1, 22–52 ppm) ponds and in one impacted site of 1,650 µS. cm−1 and 820 ppm dissolved solids. All larval Tanytarsus larvae are considered to be collector-gatherers (detritivores).

Figures

Figs. 13–25. Thai post-tsunami Chironomidae. Ventral head setae and pit: 13, Monopelopia sp., 14, Larsia sp. Larsia sp.: 15, mentum; 16, pupal thoracic horn. Parakiefferiella sp.: 17, mentum; 18, antenna; 19, mandible. Menta: 20, Tanytarsus formosanus; 21, Zavreliella sp. Antennae: 22, Tanytarsus formosanus; 23, Tanytarsus ‘Thai 1’; 24, Tanytarsus ‘Thai 2’; 25, Zavreliella sp. Abbreviations: LO, Lauterborn organ; m, mentum; sm, submentum; SSm,seta submenta; S9, S10, cephalic setae 9, 10; vmp, ventromental plate; VP, ventral pit.