Zelandochlus Brundin

Description

Introduction

Up to 7 mm long, dark brown to black head capsule with mentum, mandible and occipital margin. Eye spot single, subquadrate, in paler area.

Antenna

Antenna small, less than 20% of head capsule length, non-retractile; 5-segmented, segment 3 annulate, with segments 3 to 5 poorly differentiated from each other, style and peg sensillum well developed; blade broad, extending to apex of segment 4, accessory blade narrow, subequal to blade, without Lauterborn organs. Antennal ratio ca. 0.5. Scanning electron microscopy shows that antennal annnulations are on internal surface, with no external evidence.

Labrum

Labrum very like that of Parochlus kiefferi (Brundin, 1983). Frontoclypeal apotome present. SI, SII and SIII elongate and enlarged, somewhat sickle-shaped in lateral view, all arising from distinct pedestals; SIVa rod-shaped, arising from pedestal as long as rod, SIVb rod-shaped. One simple chaeta (perhaps the chaeta media), seta premandibularis and well-developed, slightly curved labral rod. Pecten epipharyngis of three basally-fused long scales. Premandible absent. Epipharynx with 3-4 pectinate, 2 simple elongate chaetulae laterales, and 2 robust, simple chaetulae basales; without basal sclerite.

Mandible

Mandible with modest-sized subapical tooth, longer apical tooth and 5 inner teeth, the innermost two of which are unclearly separated from the mola. Seta subdentalis apically pointed, arising from ventral surface of mola, seta interna arising from dorsal surface of mandible, with up to 30 simple branches.

Mentum

Mentum with 3 median teeth (ventromentum) and 8 pairs of lateral teeth (dorsomentum). Median mentum a triplet of teeth with the median taller than those flanking, lateral teeth diminishing in an even slope to very small outermost laterals. Ventromental plate. Setae submenti outside (lateral to) line of outermost mental teeth.

Maxilla

Palp well developed, with all setae and sensilla short, with long chaetulae. Few serrate galear lamellae, without pecten galearis. Chaetae numerous, long and simple, with broader weakly serrate anterior lacinial chaeta. Appendix absent. Premento-hypopharyngeal complex: Without developed ligula, with very dense apically finely-divided, scales filling the oral cavity.

Body

Anterior parapods fused basally, with separate crowns of serrate claws but without interconnecting fine claws. Spiracles absent. Procercus uniformly dark, cylindrical with lateral seta apparently displaced to apex, bearing apically 7 short dark setae. Posterior parapods well developed, with dark, simple claws of 2 distinct sizes, subapical ring of small claws, apical crown of long claws.

Notes

Taxonomic Notes

Zelandochlus latipalpis, the sole species of the purported genus*, is found in glacial New Zealand. The larva resembles that of Parochlus particularly in the mentum which has an enlarged median mental tooth in a moderately trifid median area, and rather evenly decreasing lateral teeth, and also in the finest details of the labrum. The spiral 3rd antennal segment is unusual amongst possible relatives, but occurs at least in the Parochlus araucanus group*. The larvae of Podochlus, unknown to Brundin (1966), can be eliminated from consideration since at least P. australiensis Brundin has a non-annulate, four-segmented antenna and a curious multiple-spined setal cluster laterally on abdominal segment IX. Unfortunately many larval podonomines remain unknown in the larval stage, including Rheochlus Brundin and many species of Podonomus and Parochlus and thus definitive larval features are not presently available.

*Molecular data (Cranston et al., 2010) confirms that Zelandochlus falls within the Parochlus araucanus group.

Ecological Notes

The larvae of Zelandochlus latipalpis, truly a member of the Parochlus araucanus group, are known only from meltwater pools and ice caves of the Franz Josef and Fox glaciers in Westland, New Zealand, where they are commonly referred to as “ice worms”. These pools and caves generally occur between the first and second icefalls on the glacier (c. 600 m.a.s.l.), as well as on the lower glacier (c. 400 m. a.s.l.). Brundin (1966) collected adult males in the Fox River, downstream of the face of the glacier, and adult males have also been recorded floating on streams on the ice (Dumbleton 1973) and on the walls of the ice caves (S. Norton, pers obs.). Although adult males cannot fly they appear to be able to hop for some distance (Dumbleton 1973), assisted by the long stout legs. Larvae occur more plentiful in shaded light in ice caves (S. Norton, pers com.), or in early morning shade in meltpools (Dumbleton 1973), avoiding direct sunlight. No detail on the food of the larvae is available.

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