Medium-sized larvae, up to 10 mm long.
SI simple or palmately divided and directed anally, sclerites undescribed.
Antenna 5 segmented with variable sclerotisation, segments 3-5 minute. Ring organ situated in proximal 11/3 of basal segment. Blade and accessory blade short, arise on apex of basal segment, or basally fused with segment 2. Lauterborn organs absent. Style on apex of 2nd segment. Antennal seta absent.
SI small, seta-like, SII long, wide, blade-like, flanked by 1-2 long chaetae; SIII very small, seta-like; SIVa 3-segmented, variable in length; SIVb not identified. Labral lamellae absent. Pecten epipharyngis triangular, perhaps notched laterally, or more deeply divided into 3 lobes. Premandible with 4-7 teeth only, brush absent.
Mandible lacking dorsal tooth, with long apical tooth and 3 pointed inner teeth. Seta subdentalis quite long, slender. Seta interna 4 branched. Pecten mandibularis with 2-4 exceptionally 7-9 lamellae.
Mentum with double or broad single wide median tooth, pale to brown, as 7 (exceptionally 3 ) pairs of lateral teeth. Ventromental plates about as wide as mentum, or narrower, coarsely striate throughout, with crenulate anterior margin (sometimes strongly so). Setae submenti simple.
Posterior parapods longer than wide, sometimes very long, with simple claws.
Lenz (1954-1962a) divided the genus into the camptolabis and nigritula groups and the validity of these groupings was confirmed by Jackson (1977a). Moller Pillot (1978a) however, argued that larvae of the nigritula group are not separable from those of P. camptolabis. Reared specimens of P. camptolabis which have been examined in preparing the present work agree with Lenz's description in having the antennal blade basally fused with segment 2. Lenz's groupings are therefore retained, but the possibility that more than one species is included under the name P. camptolabis cannot be ruled out. To these groups must be added the doris group (Sæther 1979c). "Cryptochironomus" near rolli of Sæther (1977b) has been shown to be the larva of P. doris (Sæther 1979c).
Thus "Cryptochironomus" cf. rolli, also of Sæther (1977b), and Cryptochironomus rolli presumably also belong to this genus. Paracladopelma larvae may be distinguished from all genera other than Saetheria by the combination of seta-like SI, and strong bladelike SII flanked by 1 or 2 pairs of blade-like chaetae. Larvae of Paracladopelma have 5 segmented antennae, whereas those of Saetheria usually have 6 antennal segments.
Species groups of Paracladopelma
- 1. Antennae >1/3 as long as head. Posterior parapods about 4x as long as basal width ... doris group
- -- Antennae < 1/3 as long as head. Posterior parapods < 3 x as long as basal width ... 2
- 2. Antennal blade fused basally with segment 2 of antenna ... camptolabis group
- -- Antennal blade arises distally from segment I ... nigritula group
Larvae of Paracladopelma inhabit sandy substrata in lakes, streams and small rivers and the soft profundal sediments of deep lakes. They are relatively cold stenothermic and intolerant of eutrophication.
The genus has a Holarctic distribution, with at least 16 known species.