82
THE BIOLOGY OF EUPHAUSIIDS
Thysanoessa parva Hansen, 1905
T. parva Hansen, 1905a: 25-26, figs. 22-24; 1905b: 27; 1911: 43, fig. 14;
Boden et al., 1955 : 358-359, fig. 37.
The distribution of this mesopelagic species is imperfectly known
(Fig. 27). Atlantic : occurs northwest of Bermuda, west of Portugal, the
entrance to the Mediterranean southwards off the west African coast
to near Cape Town. Pacific : there are two regions of occurrence in the
North Pacific, the eastern one being along the southeastern margin of
the Kuroshio (30"N t o 38"N, 1 3 3 " s to 14OoE), the western one dong
the western margin of the California Current (23"N to 33"N, 118"W to
131"W). It is also recorded from a restricted area in the South Pacific
(25"s to 41"S, 155"W to 164"W). Indian: there is a single record in the
Bay of Bengal a t 5'31" 94'48'E. Probably lives a t depths below 500 m
although it may live closer to the surface ; it has been taken down to
3 000 m with modal occurrences at 800 m and 1 6 0 0 m. Length
9-10-5 mm. (Hansen, 1905a, 1915; Illig, 1930; Leavitt, 1935, 1938;
Tattersall, 1936c; Boden, 1954; Nepgen, 1957 ; Brinton, 1962a;
Ponomareva, 1963.)
Thysanoessa gregaria G. 0. Sars, 1883
T. gregaria G. 0. Sam, 1883b : 26; 1885: 120-124, pl. xxi, figs. 8-17, pl. xxii ;
Hansen, 1905a ; 25-26 ; 1905b : 27-28 ; 1911 : 43-44, fig. 15 ; 1913 : 37, pl. vi, fig. 1,
a-b ; Boden et al., 1955 : 359-361, fig. 38 (nec Hansen, 1915 : 101).
T . gregaria (Fig. 27) occupies an ecological position midway
between that of the more surface-living T . longipes and T . inspinata
on the one hand and that of the deep-living T . parva on the other.
Atlantic : found south of 50"N extending to about 20"N in the western,
10"N in the eastern Atlantic, and present in the western Mediterranean.
It is not recorded between 1O"N and 30"s in the southern Atlantic but
does occur between 30"s and 56"s throughout the southern Atlantic
and Indian Ocean. Illig records it a t 0'46" 96"23'E off Sumatra and
so there may be a northern population of this species in the Indian
Ocean as well as in the Pacific and Atlantic Oceans. Pacific: it lives
in the transition zone, 40"N to 42"N in the North Pacific Drift, between
the Subarctic and Central Waters, and also in the region between 35"s
and 48's in the South Pacific. Occurs down to 1 000 m but probably
more usually above 500 m during the day, approaching the surface at
night. Length 11-16 mm. (Sars, 1885; Ortmann, 1893; Hansen,
1905a,b, 1911, 1915; Tattersall, 1913, 1918, 1924, 1925, 1927; Colosi,
1922b; Illig, 1930; Rustad, 1930; Leavitt, 1935, 1938; Ruud, 1936;
Pish and Johnson, 1937; Bigelow and Sears, 1939; Gurney, 1947;
THE BIOLOGY OF EUPHAUSIIDS
Thysanoessa parva Hansen, 1905
T. parva Hansen, 1905a: 25-26, figs. 22-24; 1905b: 27; 1911: 43, fig. 14;
Boden et al., 1955 : 358-359, fig. 37.
The distribution of this mesopelagic species is imperfectly known
(Fig. 27). Atlantic : occurs northwest of Bermuda, west of Portugal, the
entrance to the Mediterranean southwards off the west African coast
to near Cape Town. Pacific : there are two regions of occurrence in the
North Pacific, the eastern one being along the southeastern margin of
the Kuroshio (30"N t o 38"N, 1 3 3 " s to 14OoE), the western one dong
the western margin of the California Current (23"N to 33"N, 118"W to
131"W). It is also recorded from a restricted area in the South Pacific
(25"s to 41"S, 155"W to 164"W). Indian: there is a single record in the
Bay of Bengal a t 5'31" 94'48'E. Probably lives a t depths below 500 m
although it may live closer to the surface ; it has been taken down to
3 000 m with modal occurrences at 800 m and 1 6 0 0 m. Length
9-10-5 mm. (Hansen, 1905a, 1915; Illig, 1930; Leavitt, 1935, 1938;
Tattersall, 1936c; Boden, 1954; Nepgen, 1957 ; Brinton, 1962a;
Ponomareva, 1963.)
Thysanoessa gregaria G. 0. Sars, 1883
T. gregaria G. 0. Sam, 1883b : 26; 1885: 120-124, pl. xxi, figs. 8-17, pl. xxii ;
Hansen, 1905a ; 25-26 ; 1905b : 27-28 ; 1911 : 43-44, fig. 15 ; 1913 : 37, pl. vi, fig. 1,
a-b ; Boden et al., 1955 : 359-361, fig. 38 (nec Hansen, 1915 : 101).
T . gregaria (Fig. 27) occupies an ecological position midway
between that of the more surface-living T . longipes and T . inspinata
on the one hand and that of the deep-living T . parva on the other.
Atlantic : found south of 50"N extending to about 20"N in the western,
10"N in the eastern Atlantic, and present in the western Mediterranean.
It is not recorded between 1O"N and 30"s in the southern Atlantic but
does occur between 30"s and 56"s throughout the southern Atlantic
and Indian Ocean. Illig records it a t 0'46" 96"23'E off Sumatra and
so there may be a northern population of this species in the Indian
Ocean as well as in the Pacific and Atlantic Oceans. Pacific: it lives
in the transition zone, 40"N to 42"N in the North Pacific Drift, between
the Subarctic and Central Waters, and also in the region between 35"s
and 48's in the South Pacific. Occurs down to 1 000 m but probably
more usually above 500 m during the day, approaching the surface at
night. Length 11-16 mm. (Sars, 1885; Ortmann, 1893; Hansen,
1905a,b, 1911, 1915; Tattersall, 1913, 1918, 1924, 1925, 1927; Colosi,
1922b; Illig, 1930; Rustad, 1930; Leavitt, 1935, 1938; Ruud, 1936;
Pish and Johnson, 1937; Bigelow and Sears, 1939; Gurney, 1947;