120
R. I ( . DELL
georgiana (Michaelsen), P . discoveryi (Herdman), P . setosu (Sluiter),
Bathypera splendens Michaelsen, Molgula pedunculata Herdman, M .
malvinensis Arnback, M . gigantea Herdman and Pareugyrioides
arnbackae (Millar).
One ascidian which raises immensely interesting theoretical considerations is Cnemidiocarpa zenkevitchi (Vinogradova, 1958) from
brackish water bays off the Knox Coast. This form is obviously derived
from the widespread Antarctic C. verrucosa. It may represent an adaptation to the peculiar physical conditions in these bays which have the
entrances blocked by ice in the winter and are subject to a considerable
influx of fresh water run-off in the summer. Some fish remains and
echinoderms were also found in the area but apparently little else. It
would be of great interest to ascertain if any other animals show
comparable adaptations .
The ascidians are one of the few groups where the recent collections
have been worked on and where therefore the abyssal forms are reasonably well known. It has often been speculated that some elements of
the present shelf and slope Antarctic fauna might well have been
derived from adjacent abyssal basins, especially since the water temperatures in these great depths will be no lower than Antarctio shelf
waters (Broch, 1961; Dell, 1965, etc.). Kott (1969a) has shown that
this does not appear to be true for the ascidians. Only Styela mrdenskjoldi, Pyura squamata Hartmeyer and some species of Bathypera were
taken both from the Antarctic continental shelf and from the contiguous
abyssal basins. The Antarctic abyssal fauna is peculiar in its endemic
genera Protoholozoa, Pharyngodictyon, Abyssascidia and Fungulus.
Abyssal ascidians in general show a tendency towards certain modifications, e.g. branchial sac wide and open, stigmata considerably enlarged
or lost, test delicate, usually transparent, often stalked. These modifications show up in a reasonable proportion of the Antarctic abyssal
fauna, thus indicating that it has been long established.
Vinogradova (1962) recorded the collection of simple ascidians
found during the Soviet expeditions in the Indian Ocean sector. Some
110 specimens were collected from 14 stations ranging in depth from 64
to 3 800 m. Vinogradova identified 17 species arranged in 9 genera from
the families, Rhodostomatidae, Styelidae, Pyuridae and Molgulidae.
Five of these species were described as new, including the rather
strange Cnemidocurpa barbata Vinogradova which has developed long
villi which help anchor the animal to soft substrates. One of the species
discussed, Bathypera splendens is known to occur over a wide bathymetric range, from 170 t o 4 636 m.
Millar (1971) in a general review of the biology of ascidians discussed
R. I ( . DELL
georgiana (Michaelsen), P . discoveryi (Herdman), P . setosu (Sluiter),
Bathypera splendens Michaelsen, Molgula pedunculata Herdman, M .
malvinensis Arnback, M . gigantea Herdman and Pareugyrioides
arnbackae (Millar).
One ascidian which raises immensely interesting theoretical considerations is Cnemidiocarpa zenkevitchi (Vinogradova, 1958) from
brackish water bays off the Knox Coast. This form is obviously derived
from the widespread Antarctic C. verrucosa. It may represent an adaptation to the peculiar physical conditions in these bays which have the
entrances blocked by ice in the winter and are subject to a considerable
influx of fresh water run-off in the summer. Some fish remains and
echinoderms were also found in the area but apparently little else. It
would be of great interest to ascertain if any other animals show
comparable adaptations .
The ascidians are one of the few groups where the recent collections
have been worked on and where therefore the abyssal forms are reasonably well known. It has often been speculated that some elements of
the present shelf and slope Antarctic fauna might well have been
derived from adjacent abyssal basins, especially since the water temperatures in these great depths will be no lower than Antarctio shelf
waters (Broch, 1961; Dell, 1965, etc.). Kott (1969a) has shown that
this does not appear to be true for the ascidians. Only Styela mrdenskjoldi, Pyura squamata Hartmeyer and some species of Bathypera were
taken both from the Antarctic continental shelf and from the contiguous
abyssal basins. The Antarctic abyssal fauna is peculiar in its endemic
genera Protoholozoa, Pharyngodictyon, Abyssascidia and Fungulus.
Abyssal ascidians in general show a tendency towards certain modifications, e.g. branchial sac wide and open, stigmata considerably enlarged
or lost, test delicate, usually transparent, often stalked. These modifications show up in a reasonable proportion of the Antarctic abyssal
fauna, thus indicating that it has been long established.
Vinogradova (1962) recorded the collection of simple ascidians
found during the Soviet expeditions in the Indian Ocean sector. Some
110 specimens were collected from 14 stations ranging in depth from 64
to 3 800 m. Vinogradova identified 17 species arranged in 9 genera from
the families, Rhodostomatidae, Styelidae, Pyuridae and Molgulidae.
Five of these species were described as new, including the rather
strange Cnemidocurpa barbata Vinogradova which has developed long
villi which help anchor the animal to soft substrates. One of the species
discussed, Bathypera splendens is known to occur over a wide bathymetric range, from 170 t o 4 636 m.
Millar (1971) in a general review of the biology of ascidians discussed