Calanoidea: Families

J.M. Bradford-Grieve


Arietellidae Sars, 1902

Description. Female. Anterior head in dorsal view pointed, or rounded or bluntly triangular. Rostrum with 2 filaments, or without filaments; rostral margin extends into 1 blunt protrusion, or extends into 2 blunt protrusions, or 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, or with 1 acute point, or divided into 2 protrusions, or triangular or obtusely pointed; dorsal view symmetrical. Genital double-somite symmetrical in dorsal view, or asymmetrical in dorsal view; gonopores not covered by genital operculum; with pair of seminal receptacles, or with one seminal receptacle; with single copulatory pore on surface of somite, or with pair of copulatory pores on surface of somite. Caudal rami symmetrical, or asymmetrical; separate from anal somite.

Mouthparts. Antenna 1 with 15-22 free segments; ancestral segments X and XI separate. Antenna 2 exopod with 5-10 free segments; 5-8 setae; with 2 terminal setae; basis and endopod separate. Mandible basis without setae; endopod 1-segmented, or absent; endopod terminal segment with 0-2 setae. Maxilla 1 basal exite seta absent; exopod elongate relative to endopod. Maxilla 2 coxal epipodite seta absent; endopod setae normal, or claw-like. Maxilliped coxal endite 2 without setae, or with 1 seta.

Legs. Leg 1 basis inner distal seta inserted directly on surface of joint; outer seta present; 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 6-8 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; very dissimilar from legs 2-4; coxa inner border without seta; variable and not natatory, usually symmetrical, coxae and intercoxal sclerite separate or fused, basis and endopod fused or separate (in Griceus leg 5 formed of only one segment with terminal seta), endopod with 0-4 setae, exopod 1-3-segmented or completely fused with basis, with 0-5 elements.

Mode of life. Pelagic or benthopelagic, in oceanic waters or in coastal waters.

Depth distribution. Bathypelagic (greater than 1000 m).

Distribution on sea floor. Less than 100 m, or 100-200 m, or 200-1000 m.

Generic composition. This family now contains 12 genera: Arietellus Giesbrecht, 1892; Campaneria Ohtsuka, Boxshall, Roe, 1994; Crassarietellus Ohtsuka, Boxshall, Roe, 1994; Metacalanus Cleve, 1901; Paramisophria T. Scott, 1897 (= Parapseudocyclops Campaner, 1977); Paraugaptiloides Ohtsuka, Boxshall, Roe, 1994; Paraugaptilus Wolfenden, 1904; Pilarella Alvarez, 1985; Rhapidophorus Edwards, 1891; Sarsarietellus Campaner, 1984; Scutogerulus Bradford, 1969. Griceus Ferrari & Markhaseva, 2000 is also probably an arietellid.


(Variant) Male (sexually dimorphic characters).

Description. Male. Rostral margin extends into 1 blunt protrusion, or not extended. Pedigerous somites 4 and 5 fused or partly fused. Posterior corners of prosome in lateral view bluntly rounded, or with 1 acute point, or triangular or obtusely pointed.

Mouthparts. Mouthparts well-developed. Antenna 1 geniculate on left. 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 distinctly or indistinctly 3-segmented, segments 1 and 2 each with seta on outer margin (rarely segment 1 unarmed), segment 2 with tuft of setules on inner distal angle, segment 3 with 0-3 spines and setae terminally; left endopod 1-2-segmented, unarmed or completely absent. Left leg 5 uniramous, or biramous; endopod 1-segmented, or 2-segmented; exopod distinctly 3-segmented, segments 1 and 2 each with seta on outer margin, segment 3 with 1-3 spines and setae terminally.



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