Calanoidea: Families

J.M. Bradford-Grieve


Ryocalanidae Andronov, 1974

Description. Female. Rostrum without filaments; rostral margin extends into 2 points, or extends into 1 point. Cephalosome and pedigerous somite 1 separate; pedigerous somites 4 and 5 separate. Posterior corners of prosome in lateral view with 1 acute point, or divided into 2 protrusions, or triangular or obtusely pointed; dorsal view symmetrical. Genital double-somite symmetrical 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 symmetrical, or asymmetrical.

Mouthparts. Antenna 1 with 24-25 free segments; ancestral segments X and XI partly fused. Antenna 2 exopod with 5-6 free segments; 10-12 setae; basis and endopod separate. Mandible basis with 2 setae, or with 3 setae; endopod terminal segment with 9-10 setae. Maxilla 1 basal exite seta absent; exopod extends short of endopod distal border. Maxilla 2 coxal epipodite seta present. Maxilliped coxal endite 2 with 2 setae, or with 3 setae.

Legs. Leg 1 basis outer seta absent; endopod with 1 segment; exopod with 3 segments; exopod segment 1 with outer distal spine; exopod segment 3 with 4 inner setae. Leg 2 endopod with 2 segments; exopod with 3 segments; exopod segment 3 with 3 outer spines. Leg 3 basis outer distal spine absent; endopod segment 3 with 6 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 6 setae. Legs 2-4 surfaces strongly spinulose, or weakly spinulose; terminal spine with outer border serrated. Leg 5 absent.

Mode of life. Pelagic, in oceanic waters.

Depth distribution. Bathypelagic (greater than 1000 m).

Generic composition. This family contains only the genus Ryocalanus Tanaka, 1956.


(Variant) Male (sexually dimorphic characters).

Description. Male. Posterior corners of prosome in lateral view bluntly rounded, or triangular or obtusely pointed. Caudal rami symmetrical.

Mouthparts. Mouthparts well-developed. Antenna 1 geniculate on right; geniculation between ancestral segments XXIII and XXIV. Maxilliped endopod segments 5 and 6 with outer setae normal.

Legs. Right leg 5 uniramous, or biramous; endopod separate from basis and 1-segmented; exopod 1-segmented, segment rounded distally, unarmed. Left leg 5 uniramous, or biramous; endopod 1-segmented; exopod elongate, 3-segmented, segment 1 unarmed, segment 2 with inner border hairs, segment 3 rounded distally, unarmed.



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