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R. K. DELL
6. Austrocidaris. The two species, A . canaliculata (Agassiz) and
A. spinulosa Mortensen are confined to Southern South America, the
Patagonian shelf and the Falkland Islands.
7. Ogmocidaris. Another monotypic genus, with 0. benhami
Mortensen being confined to the New Zealand region.
Thus of the seven genera and 21 species, five genera and 16 species
are found in Antarctica (three genera and 14 species being found nowhere else).
The genus Sterechinus, the only regular non-cidaroid sea urchin
genus in the Antarctic, has five species. One, S. diadema (Studer) is
known only from Kerguelen Island, one S. ugassizi Mortensen seems to
be centred in southern South America although it also occurs in South
Georgia. The other three species, S. neumayeri (Meissner), S. antarcticus
Koehler and S. dentifer Koehler, are found around the Continent with
S . neumayeri obviously circum-Antarctic and extending to the South
Orknep and South Georgia.
The name Sterechinus neumayeri crops up again and again in the
more recently published accounts of diving investigations in shallow
water from the islands of the Scotia Arc to the Ross Sea.
Pearse and Giese (1966) studied the food, reproduction and organic
constitution of this species in McMurdo Sound. Here S. neumayeri
occurred abundantly on basaltic gravel at less than 15 m depth. Like
many other regular echinoids, these sea urchins often cover their tests
with stones and whatever other debris is available.
In some areas in McMurdo Sound the echinoid occurred together
with abundant red algae (Iridaea sp.). However, the main food from
about November to April seems to be diatoms, an extensive layer of
which appears on the sea, floor in shallow water over this period. In
areas near extensive concentrations of Weddell seals, the sea floor
becomes littered with seal faeces. Sterechinus gathers round these
deposits in these areas, and Pearse and Giese found the gut then filled
with seal faeces with comparatively few diatoms. This species of echinoid is obviously another of the successful, widely distributed Antarctic
animals whose lack of adaptation to narrow feeding requirements has
undoubtedly contributed to their ecological success.
Pearse and Giese give a full account of gonad development and
oocyte generations, but were not able to study development after
fertilization.
The beginning of growth of the oocytes of Sterechinus probably takes
place between November and May, during the period of production of
phytoplankton. Gonads grow throughout the summer, in part through
the accumulation of food materials in the nutritive phagocytes of the
R. K. DELL
6. Austrocidaris. The two species, A . canaliculata (Agassiz) and
A. spinulosa Mortensen are confined to Southern South America, the
Patagonian shelf and the Falkland Islands.
7. Ogmocidaris. Another monotypic genus, with 0. benhami
Mortensen being confined to the New Zealand region.
Thus of the seven genera and 21 species, five genera and 16 species
are found in Antarctica (three genera and 14 species being found nowhere else).
The genus Sterechinus, the only regular non-cidaroid sea urchin
genus in the Antarctic, has five species. One, S. diadema (Studer) is
known only from Kerguelen Island, one S. ugassizi Mortensen seems to
be centred in southern South America although it also occurs in South
Georgia. The other three species, S. neumayeri (Meissner), S. antarcticus
Koehler and S. dentifer Koehler, are found around the Continent with
S . neumayeri obviously circum-Antarctic and extending to the South
Orknep and South Georgia.
The name Sterechinus neumayeri crops up again and again in the
more recently published accounts of diving investigations in shallow
water from the islands of the Scotia Arc to the Ross Sea.
Pearse and Giese (1966) studied the food, reproduction and organic
constitution of this species in McMurdo Sound. Here S. neumayeri
occurred abundantly on basaltic gravel at less than 15 m depth. Like
many other regular echinoids, these sea urchins often cover their tests
with stones and whatever other debris is available.
In some areas in McMurdo Sound the echinoid occurred together
with abundant red algae (Iridaea sp.). However, the main food from
about November to April seems to be diatoms, an extensive layer of
which appears on the sea, floor in shallow water over this period. In
areas near extensive concentrations of Weddell seals, the sea floor
becomes littered with seal faeces. Sterechinus gathers round these
deposits in these areas, and Pearse and Giese found the gut then filled
with seal faeces with comparatively few diatoms. This species of echinoid is obviously another of the successful, widely distributed Antarctic
animals whose lack of adaptation to narrow feeding requirements has
undoubtedly contributed to their ecological success.
Pearse and Giese give a full account of gonad development and
oocyte generations, but were not able to study development after
fertilization.
The beginning of growth of the oocytes of Sterechinus probably takes
place between November and May, during the period of production of
phytoplankton. Gonads grow throughout the summer, in part through
the accumulation of food materials in the nutritive phagocytes of the