Hanochironomus Ree

Description

Introduction

Blood-red, thorax with irregular green markings, head pale except tips of mandible. Small to medium-sized larvae, up to 7 mm long.

Dorsal Head

Frontoclypeal apotome, with straight transverse anterior margin.

Antenna

Antenna with 6 segments, segment 2 much shorter than 3rd, 4th shorter than 3rd. Paired Lauterborn organs and stronger style both on apex of 3rd segment. Ring organ in proximal 1/5 of segment 1, seta absent. Blade apical on 2nd segment, subequal to flagellum, accessory blade extending to 3rd segment.

Labrum

Bases of SI fused, SI blade-like, SII also blade-like, subequal to SI, flanked by 2 long, blade-like, apically serrate, labral chaetae; SIII short, seta-like; SIVA long, '3-segmented', SIVB a short rod on tubercle. Labral lamellae absent. Pecten epipharyngis a distally serrate simple plate. Eight pairs of strong to slender chaetae laterales, serrate along inner margin. Premandible with 6 pointed teeth, brush absent.

Mandible

Mandible with long pale, slender, dorsal tooth, with apical tooth and 3 subequal triangular, inner teeth. Seta subdentalis lanceolate, extending just beyond innermost tooth. Seta interna of 3 serrate main branches. Pecten mandibularis of several long lamellae, located in basal half of mandible.

Mentum

Mentum with broad median tooth, rounded medially, crenulate laterally, concolourous with 6 pairs of lateral teeth on each side; 3rd laterals smaller, 4th larger than even line of slope. Each ventromental plate narrower than mentum, widely separated medially, with distinct striae not reaching anterior margin, anterolateral marginal short spines or striae. Setae submenti strong, simple.

Maxilla

Palp moderately well developed, 1st segment about 2 times as long as wide; whole palp subequal in length to antennal segment 1. Lacinial chaetae hyaline, thin.

Body

Anterior parapods contiguous; posterior parapod with simple claws. Procerci with 7 long setae. Anal papillae short, tapered to round apices. Lateral and ventral tubules absent.

Notes

Taxonomic Notes

The structure of the antenna of Hanochironomus resembles Saetheria, in that the 6-segmented antenna arises by division of the second segment, such that the Lauterborn organs are on the apex of the 3rd: the blade is located on the subapex of the 2nd segment. These two genera resemble Paracladopelma in possession of seta-like SI, stong blade-like SII and flanking blade-like, serrate chaetae.

Hanochironomus differs from these members of the Harnischia-complex in having a distinct outer mandibular tooth. Diagnosis follows Yamamoto et al. (2007).

Ecological Notes

Hanochironomus was described from South Korea based on the adult alone. The larva of the sole species, H. tumerestylus, is abundant in sand-filter beds in filtration plants in Ishigaki Island, Okinawa, southern Japan (Yamamoto, et al., 2000a).

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