Claus, 1863
Short Description:
Euchirella messinensis messinensis is an aetideid calanoid copepod known after both sexes (female 4.40-6.20 mm and male 2.80-5.46 mm) from mesopelagic waters.
Taxonomic Description:
Female. Total length 4.40-6.20 mm. Cephalothorax nearly 4 times longer than abdomen. Rostrum comparatively large. Crest absent. Posterior Th5 corners rounded (lateral view), of slightly rectangular shape (dorsal view). Genital segment abruptly asymmetrical: its left side with large projection, covering 2 next abdominal segments (dorsal and lateral view). Genital segment nearly 1.2 times longer than wide. A1 slightly longer than cephalothorax, 24- segmented. Ri A2 about 5 times shorter than Re, coxo- and basipodite and Ri1 A2 with 1 seta each; Ri2 A2 with 5 setae on external and 4 on internal lobe. Md palp base without setae, Ri1 Md with 1 very small seta, Ri2 Md with 9 setae. Mx1 with 3 setae on posterior gnathobase surface and 4 and 3 (1 long and 2 small thin) setae on second and third internal lobes respectively, 3 setae on protopodite near the Ri base, 4 setae on Ri and 11 on Re. Mx2 and Mxp typical of the genus. P1 Re1 with first external spine longer than the second one and exceeding two thirds of its length. P2-P4 typical of the genus, terminal Re spines with about 19 denticles. P4 coxopodite with 2 spines.
Male. (Description after Bradford and Jillett (1980) with modifications). Total length 2.80-5.46 mm. Differs from female in low crest. Rostrum well developed. Re3 P5 left not reaching the first projection on Ri of right leg.
Vertical distribution:
Difficult to describe, i.e. species is very close to E. messinensis indica and very possible (in any case males) was mixed with E. messinensis messinensis . Due to the above mentioned reasons it is difficult to describe species vertical distribution. In the Gulf of Mexico species was found in day time in 500-2000 m, with the richest catches upper than 1000 m, at night the richest catches were in upper 100 m. This is a good evidence of intensive diurnal migrations (Park, 1976b). The species was also recorded in haul 0-150 m in the north-western Atlantic (Von Vaupel Klein, 1984).
Geographical distribution:
Some authors consider that further investigations should confirm allopatry of these species, will restrict distributional area of E. m. messinensis to the Atlantic Ocean and the Mediterranean Sea and E. m. indica to Indo-Pacific region (Von Vaupel Klein, 1984).
Type locality: the Mediterranean Sea (Claus, 1863).
Material examined:
1 female from sample 573. See examined samples module.