Calanoidea: Families

J.M. Bradford-Grieve


Heterorhabdidae Sars, 1902

Description. Female. Anterior head in dorsal view rounded or bluntly triangular. Rostrum with 2 filaments; rostral margin extends into 1 blunt protrusion, or not extended. Cephalosome and pedigerous somite 1 separate; pedigerous somites 4 and 5 fused or partly fused. Posterior corners of prosome in lateral view bluntly rounded; dorsal view symmetrical. Genital double-somite symmetrical in dorsal view, or asymmetrical in dorsal view; gonopores close together and totally covered by single genital operculum; with pair of seminal receptacles; with pair of copulatory pores that are completely covered by genital operculum. Caudal rami asymmetrical; with both fused or partly fused to anal somite, or with one fused to anal somite.

Mouthparts. Antenna 1 with 25 free segments; ancestral segments X and XI separate. Antenna 2 exopod with 7-9 free segments; 7-11 setae; basis and endopod separate. Mandible basis without setae, or with 1 seta, or with 2 setae, or with 3 setae, or with 4 setae; endopod terminal segment with 6-10 setae. Maxilla 1 basal exite seta absent; exopod extends as far as endopod distal border, or elongate relative to endopod. Maxilla 2 coxal epipodite seta absent; endopod setae normal, or claw-like. Maxilliped coxal endite 2 with 1 seta, or with 2 setae, or with 3 setae.

Legs. Leg 1 basis outer seta present, or absent; endopod with 3 segments; exopod with 3 segments; exopod segment 1 with outer distal spine; exopod segment 3 with 4 inner setae. Leg 2 endopod with 3 segments; exopod with 3 segments; exopod segment 3 with 3 outer spines. Leg 3 basis outer distal spine absent; endopod segment 3 with 8 setae. Legs 3 and 4 endopod with 3 segments; exopod with 3 segments; exopod segment 3 with 3 outer spines; exopod segment 3 with 5 inner setae. Leg 4 endopod segment 3 with 7 setae. Legs 2-4 surfaces naked; terminal spine with outer border serrated. Leg 5 present; similar to legs 2-4; coxa inner border without seta; exopod segment 2 inner distal border with enlarged, spine-like seta. Leg 5 exopod segment 3 outer border with 2 spines; inner border with 4 setae.

Mode of life. Pelagic, in oceanic waters.

Depth distribution. Mesopelagic (500-1000 m), or bathypelagic (greater than 1000 m).

Generic composition. This family contains 7 genera: Disseta Giesbrecht, 1892; Hemirhabdus Wolfenden, 1911; Heterorhabdus Giesbrecht, 1892; Heterostylites Sars, 1920; Mesorhabdus Sars, 1905; Neorhabdus Heptner, 1972; Paraheterorhabdus Park, 1999. Alrhabdus Grice, 1973 and Microdisseta Heptner, 1972 have been removed from the Heterorhabdidae by Park (1999) but have not yet been placed in a family.


(Variant) Male (sexually dimorphic characters).

Description. Male.

Mouthparts. Mouthparts well-developed. Antenna 1 geniculate on left. Maxilliped endopod segments 5 and 6 with outer setae normal.

Legs. Right leg 5 biramous; endopod 3-segmented; exopod elongate, 3-segmented, segment 2 with inner expansion of variable shape and extent. Left leg 5 biramous; endopod 3-segmented; exopod elongate, 3-segmented, segment 3 often but not always terminated by elongate spine.



Cite this publication as: 'Bradford-Grieve, J.M. (2002 onwards). Calanoida: families. Version 1: 2 October 2002. http://crustacea.net'.