Euchirella Giesbrecht, 1888
Taxonomic description:
Female. Total length about 3-8 mm. Cephalothorax 3.5-7.0 times longer than abdomen. Cephalon and Th1 completely, or incompletely fused (line of fusion sometimes visible), Th4-Th5 fused. Crest present, or absent. Rostrum 1-pointed, small, often well developed, rarely rudimentary (E. curticauda ). Posterior Th5 corners usually rounded (lateral and dorsal view), sometimes rounded-rectangular (dorsal view), rarely slightly prolonged symmetrical, rarely asymmetrical and weakly prolonged. Genital segment symmetrical, or asymmetrical; asymmetry may be slight (E. unispina ), or rather expressed. Length and width of caudal rami often equal, sometimes 1.3-1.4 times wider than long. A1 23-segmented, often longer than cephalothorax, sometimes exceeding caudal rami. A2 with typical of the genus short Ri, less than half the length of Re, more often about one third, or one fourth of Re length. A2 coxopodite with 1 seta, basipodite usually with 1, sometimes with 2 (E. rostrata ) setae, or seta absent (E. maxima ). Ri1 A2 usually with 1 seta, rarely seta absent. Internal Ri2 A2 lobe with 1-2 or 4-8 setae, external with 3-6 (7) setae, often its lateral border supplied with minute spinules. Re1 A2 and Re2 A2 completely or not completely fused, setae absent, sometimes tooth-like projection present (from Re 1 to 3). Structure and setation of Re2-Re7 A2 typical of Aetideidae. Md palp base usually without setae, sometimes there is 1 seta (E. curticauda ) or sclerotized sharp projection (E. amoena ); Ri1 Md usually without setae, rarely 1 seta present (E. curticauda , E. messinensis ), Ri2 Md nearly always with 9 setae (in E. bitumida with 7-8 setae). Mx1 gnathobase with 2, 3 or 4 setae on posterior surface, 9 terminal setae, and often 1 thin seta; second internal lobe with 3-4 setae, third with 1 (E. bella ), 2, 3 setae, often 1 small, possibly sensory knob present. Mx1 protopodite near Ri base, usually with 3 setae, sometimes 2; Ri with 3-5 setae, Re with 11, rarely with 10, or 8 setae, external lobe with 6, 8 or 9 setae. Mx2 with 1 claw-like spine on fourth and fifth endites, distal part of Ri with 6 long setae. Mxp protopodite shorter than Ri1 Mxp, on protopodite there is a seta near the base of the segment, or it is absent, then 3 groups of 2, 3 and 3 setae (looking from proximal end of the segment to its distal part), near the base of distal group there is a group of minute spinules; in the middle of Ri1 3 setae. P1 with 2-segmented Re, supplied with 2 external spines and one-segmented Ri with well developed external lobe. P2 with 3-segmented Re and one-segmented Ri. P3-P4 rami 3-segmented. P4 coxopodite with sclerotized spines near the base of internal seta. They are of different size and number: there may be 5 minute spinules on the posterior surface of segment (E. amoena ), or 1 big sclerotized spine containing of 5-8 fused smaller ones (E. maxima ). Usually from 1 to 5, or from 8 to 13 spines present.
Male. Total length 2.50-7.35 mm. Cephalothorax 3.5-4.0 times longer than abdomen. Rostrum present, sometimes virtually absent (E. curticauda ). Crest present (high, or
low), or absent. Cephalon and Th1, as well as Th4-Th5 fused. Posterior Th5 corners usually rounded. A1 longer than cephalothorax, reaching the end of Abd2 or the end of caudal rami, often they are supplied with aesthetascs. Re A2 often 1.4-1.5 times longer than Ri A2. Setation in comparison with that in females rudimentary, when described, then: for Ri2 A2 usually 6 setae on external and 6-7 setae on internal lobes; 8 setae on Ri2 Md and 10-11 setae on Re and Ri Mx1 each; 5-7 setae on external Mx1 lobe. Mx2 strongly reduced. Re P1 usually 2- segmented (Re1 and Re2 fused, but often the division between segments is more pronounced than in female); usually external spines on Re1-Re2 P1 strongly reduced, often one of them absent, terminal external spine usually present, but in some species 1, or 2 external spines well developed. P2-P4 segmentation close to that in females. P5 biramous, or only right P5 biramous. Re P5 left 3-segmented, Ri P5 left, if present, one-segmented, more often present as rudiment, rarely better developed. Fixed projection between Re2 P5 left and Re3 P5 left form nippers (tongs) with parts equal, or unequal length. Re P5 right 2-segmented, Ri P5 right one-segmented; sometimes nearly as long as Re1 of this leg and not forming tongs with Re; but more often Re P5 and Ri P5 right elongated and sharpened in their distal part, forming tongs. P5 right basipodite enlarged, in the majority of species. Right Re P5 significantly longer, than left Re.
Remarks. The synonymy to Euchirella species is given below in brief version from Von Vaupel Klein's (1984) detailed synonymy.
Type species: Undina messinensis Claus, 1863, by monotypy.
The genus Euchirella includes 25 species. 20 species of Euchirella are described in this program, except: species with unclear status (E. orientalis Sewell, 1929 and E. tanseii Omori, 1965), E. paulinae , known off the tropical part of the Indian Ocean and E. lisettae found in the eastern Pacific and off the coasts of South and Central America. Two species from antarctic and subantarctic waters E. latirostris and E. rostromagna , which, following Park (1978) and Bradford and Jillett (1980) may be identical are not described here either.
Euchirella amoena Giesbrecht, 1888
Euchirella bella Giesbrecht, 1888
Euchirella bitumida With, 1915
Euchirella curticauda Giesbrecht, 1888
Euchirella formosa Vervoort, 1949
Euchirella galeata Giesbrecht, 1888
Euchirella grandicornis Wilson, 1950 (male unknown)
Euchirella maxima Wolfenden, 1905
Euchirella messinensis indica Vervoort, 1949
Euchirella messinensis messinensis (Claus, 1863)
Euchirella pseudopulchra Park, 1976 (male unknown)
Euchirella pseudotruncata Park, 1975
Euchirella pulchra (Lubbock, 1856)
Euchirella rostrata (Claus, 1866)
Euchirella similis Wolfenden, 1911 (male unknown)
Euchirella speciosa Grice and Hulsemann, 1968 (male unknown)
Euchirella splendens Vervoort, 1963
Euchirella truncata Esterly,1911
Euchirella unispina Park, 1968
Euchirella venusta Giesbrecht, 1888