Calanoidea: Families

J.M. Bradford-Grieve


Mesaiokeratidae Matthews, 1961

Description. Female. Rostrum with 1 filament; rostral margin not extended. Cephalosome and pedigerous somite 1 fused or partly fused, or separate; pedigerous somites 4 and 5 fused or partly fused, or separate. 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 symmetrical.

Mouthparts. Antenna 1 with 23-24 free segments; ancestral segments X and XI fused. Antenna 2 exopod with 6 free segments; 9-12 setae; basis and endopod separate. Mandible basis with 1 seta, or with 4 setae; endopod terminal segment with 8 setae, or 10 setae. Maxilla 1 basal exite seta absent; exopod elongate relative to endopod. Maxilla 2 coxal epipodite seta absent. Maxilliped coxal endite 2 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, or without outer distal spine; exopod segment 3 with 3 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 5 setae. Legs 3 and 4 endopod with 3 segments; exopod with 3 segments; exopod segment 3 with 3 outer spines; exopod segment 3 with 4 inner setae. Leg 4 endopod segment 3 with 5 setae. Legs 2-4 surfaces weakly spinulose; terminal spine with outer border serrated. Leg 5 present; very dissimilar from legs 2-4; coxa inner border without seta; uniramous, coxae and intercoxal sclerite fused, single additional segment elongate and terminated in 2 teeth.

Mode of life. Benthopelagic, in coastal waters.

Distribution on sea floor. Less than 100 m, or 100-200 m.

Generic composition. This family contains only the genus Mesaiokeras Fosshagen, 1978.


(Variant) Male (sexually dimorphic characters).

Description. Male. Pedigerous somites 4 and 5 fused or partly fused. Posterior corners of prosome in dorsal view symmetrical, or asymmetrical.

Mouthparts. Mouthparts well-developed. Antenna 1 similar, neither geniculate. Maxilliped endopod segments 5 and 6 with outer setae normal.

Legs. Right leg 5 uniramous; exopod absent. Left leg 5 uniramous; exopod very narrow and elongate, 3-segmented, segment 3 tapers distally to point with 2 subterminal spinules.



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