Chiridiella Sars, 1907
Taxonomic description:
Female. Total length 2.30-2.50 mm. Cephalothorax 3.5-5.0 times longer than abdomen. Cephalon and Th1 separated, incompletely separated or fused, Th4-Th5 fused. Crest absent. Rostrum absent. Cephalothorax usually oval, widest in its middle; cephalon always rounded in its anterior part. Posterior Th5 corners always rounded and symmetrical. Genital segment symmetrical. A1 23-24-jointed, shorter, or longer than cephalothorax, sometimes longer than body. Re A2 usually longer than Ri, sometimes rami of equal length (Ch. subaequalis ); Re1-Re2 A2 without setae, Re3-Re6 with one seta each, Re7 with 3 terminal setae; coxo- and basipodite usually with 1 seta each, Ri1 A2 without setae (except Ch. kuniae ), Ri2 A2 usually with 6 setae on external and 6-8 setae on internal lobe (9 in Ch. chainae (Grice, 1969)). Md palp base without setae, also Ri1 Md (but Sars (1925) figured seta in Ch. macrodactyla ). Ri2 Md may possess between 1 (Ch. gibba ) and 8 (Ch. atlantica ) setae. Mx1 in comparison with that of other Aetideidae genera reduced: second internal lobe, Re or external lobe may be absent also setation of Mx1 may be reduced. Mx1 gnathobase with 8-11, 13 setae; second internal lobe (if present) bears from 1 to 3 setae (Ch. subaequalis , Ch. kuniae ); third internal lobe with 1 (Ch. ovata ) commonly with 2-4 setae, Ri with 3-5 or 7, Re (if present) with 3-6, 8-10 setae; external lobe (if present) with 4-9 setae. Mx2 structure as well as Mx1 very specific. Mx2 within Chiridiella is strongly changing from structure close to typical of genus to strongly modified. Setation of endites, and sometimes endites themselves strongly reduced, and only a few setae are saved of the distal part of Ri. Structure of Mx2 most close to typical of family may be observed in Ch. bispinosa , Ch. brachydactyla , Ch. chainae , Ch. kuniae , Ch. subaequalis (even distal part of Ri is present); in other species setation of first-fifth endites is different through the reduction of setae number. Then on third-fourth endites 2 spines, a bigger and smaller one, both arranged like pincers appear: Ch. bichela , Ch. brooksi. In further transformation of Mx2 the pincer-like spines present only on one of endites and setation on first-second endites become even more reduced (on second endite only one small seta present): Ch. abyssalis , Ch. atlantica , Ch. gibba , Ch. macrodactyla , Ch. megadactyla , Ch. ovata , Ch. sarsi . Then one can observe the reduction in number of endites: there are only 4 in Ch. reducta and Ch. smoki and 3 in Ch. pacifica. Mxp protopodite with more typical of Aetideidae genera setation observed in Ch. subaequalis (1+1+3+3) (the first figure denotes seta in proximal part of joint, 3 following figures denote number of setae in 3 groups from proximal to distal part of the joint); Ch. bispinosa (0+1+3+3); Ch. brachydactyla (0+1+2+3); Ch. kuniae (1+1+2+3); Ch. chainae (0+0+1+3), in other species of the genus all groups of setae (except distal group with 1-2 setae) get reduced. Ri1 Mxp usually with 2 or 3 medial setae. P1 with one-jointed rami, Re with 1 or 2 external spines; Ri without external lobe (only in Ch. kuniae it present). P2 with 3-jointed Re but separation between Re1 and Re2 often incomplete. Ri usually one-jointed. P3-P4 with 3-jointed Re, sometimes division may be not clear, and 3-jointed or incompletely 2-3-jointed and even one-jointed Ri. Internal seta lacking on P4 coxopodite also hairs near seta base may be lacking.
Male. Known only for 2 species of genus: Ch. abyssalis and Ch. pacifica , they are very close in structure. Body shape, P1-P4 close to that in females of corresponding species, but separation between P2-P4 segments may be more complete. Oral parts remarkably reduced. P5 biramous with one-jointed Ri and 2-3-jointed Re, of simple structure.
Type species: Chiridiella macrodactyla Sars, 1907, by subsequent designation (Brodsky, 1950).
The genus Chiridiella includes 18 species. The descriptions of 15 species (except Ch. trichamata which is known after fifth copepodite stage; Ch. atlantica known of tropical Atlantic and Ch. megadactyla of the Ross Sea) are given.
Chiridiella abyssalis Brodsky, 1950
Chiridiella bichela Deevey, 1974 (male unknown)
Chiridiella bispinosa Park, 1970 (male unknown)
Chiridiella brachydactyla Sars, 1907 (male unknown)
Chiridiella brooksi Deevey, 1974 (male unknown)
Chiridiella chainae Grice, 1969 (male unknown)
Chiridiella gibba Deevey, 1974 (male unknown)
Chiridiella kuniae Deevey, 1974 (male unknown)
Chiridiella macrodactyla Sars, 1907 (male unknown)
Chiridiella ovata Deevey, 1974 (male unknown)
Chiridiella pacifica Brodsky, 1950
Chiridiella reductella Markhaseva, 1996 (male unknown)
Chiridiella sarsi Markhaseva, 1983 (male unknown)
Chiridiella smoki Markhaseva, 1983 (male unknown)
Chiridiella subaequalis Grice and Hulsemann, 1965 (male unknown)