Juday, 1923
Short Description:
Senecella calanoides is an aetideid calanoid copepod known after both sexes (female 1.90-3.35 mm and male 2.45-2.55 mm) from Siberian seas and fresh water lakes of North America.
Taxonomic Description:
Female. (Description after Borutsky and Stepanova (1991), Juday (1925) and Marsh (1933)). Total length 1.98-3.35 mm. A1 25-jointed. Re1 A2 with 1 seta (Juday, 1925) (after Marsh (1933) here -2 setae), Re2 A2 with 3 seta (Juday, 1925) (after Marsh (1933) here -2 setae), Ri1 A2 with 2 setae and Ri2 A2 with 7 setae on both lobes. Md palp base with 2 setae, Ri1 Md with 2 setae, Ri2 Md with 9 setae. Second and third internal lobes of Mx1 with 3 (?) setae each, protopodite near Ri base with 5 setae; Ri with 12 and Re with 10 setae, external lobe with 7 setae. Mx2 with sixth endite with 1 long seta (as in Jaschnovia). Re P1 3-jointed, Re1 P1 lacking external spine, Ri P1 well developed. Re3 P2-P4 with 2 external spines unique of Aetideidae. P4 coxopodite with 1 robust internal spine.
Male. (Description after Borutsky and Stepanova (1991) with modifications). Total length 2.45-2.55 mm. A1 25-jointed. P4 coxopodite without internal spine. P5 biramous. Right Re P5 2-jointed; Re1 with 1 small spine distally; from internal distal corner of Re1 narrow plate comes from that extending along internal border of Re2. Re relatively short with small seta distally; terminal spine long. Right Ri one-jointed, elongated. Left Re 2-jointed, Re2 with short terminal spine; Ri one-jointed.
Geographical distribution:
The species was found in the Siberian seas and in the mouth of Siberian rivers (Pirozhnikov, 1958; Borutsky and Stepanova, 1991), in lakes of Canada and North American States.
Type locality: Finger lakes, New York (Juday, 1923).
Ecology:
Mostly brackish-water species, may be found in marine and fresh waters. In the northern Siberia found in abundance under salinities not higher than 15-20รค. The species is common in zooplankton of the North American fresh lakes. Total length of specimens depends on the locality, varying from 3.15-3.35 to 2.62-2.95 in the direction from sea to river mouth (Smirnov, 1938). In North Siberia adult females emerge in the second half of September, become more numerous in January; in summer only naupliar and copepodite stages may be found. In American lakes specimens get matured in July-August (Borutsky and Stepanova, 1991).