58
Systematic Account
normally reported for P. robusta f. typica
Steuer, 1931.
Distribution
P. robusta is widely distributed, inhabiting
intermediate depths but also occurring at the
surface. Farran (1929) reported it as a
common species in a small area south of New
Zealand between 51° and 53°S. Sars (1903)
found a few specimens north of the Faroe
Islands (200-400m) and from other areas of
Norway. Ramirez (1969, 1971) reported the
f. typica in offshore Argentinian waters from
0-600 m. Ramirez and Dinofrio (1976) sampled it in the Antarctic sector of Argentina.
Bjomberg (1963) found it from 400-600m
off Brazil in waters of Antarctic origin.
Mackintosh (1934) reported it from circumpolar Antarctic areas and Hardy and Gunther
(1935) near South Georgia from 0-1000m.
Vervoort (1951) found the f. antarctica in
samples from 0-100 m in the Atlantic sector
of the Antarctic. Vervoort (1965a) recorded
P. robusta robusta in Atlantic waters of
intermediate depth and also at the surface,
but in lower numbers. Fagetti (1962) cites P.
robusta in her catalogue of the planktonic
copepods of Chile. Roe (1972) provides
detailed information on the vertical distribution of P. robusta, without separation
between the two forms. This author reported
P. robusta as the least common of the
Pleuromamma species from the Sound cruise
but fairly common in intermediate waters,
with maximum day depths at 400 m and
extensive vertical migrations at night up to
25 m. In the present study, P. robusta was
present only from 150-700 m in the Pacific
area of the Straits of Magellan.