ANTARUTIU BENTHOS
107
gonads. Spawning takes place in the southern winter, somewhere between May and December. The ova are of relatively small size (about
125 p) and this suggests indirect development. From the evidence of
echinoplutei collected on earlier expeditions, and almost certainly
belonging to this species, Sterechinw probably develops feeding echinopluteus larvae during the summer. Plankton samples taken throughout the year a t McMurdo Sound failed to produce any echinoplutei.
From the available evidence it appears that oocytes take from 18 to
24 months to reach maturity, spawning occurs in winter between May
and December and that early embryonic development is slow, so that
echinopluteus larvae are finally produced in the summer, when maximum plant food is available. The larval habitat is presumed to be close
to the bottom.
Members of the family Schizasteridae comprise some of the most
typical Antarctic animals. The genus Abatus with ten species is confined to the Antarctic and Subantarctic with an incursion into the
coastal waters of Argentina. One species A. cordatus (Verrill) has been
recorded only from the vicinity of Kerguelen and Heard Island. Three
species, A. agassizi (Pfeffer), A. cavernosus (Philippi) and A. philippi
L o v h have been recorded from East Antarctica, the Antarctic Peninsula (except for agussizi), south Georgia and Southern South America,
with A . cavernosus and A . philippi extending to about 36'5. Two
species have a restricted distribution in West Antarctica, with A.
elongatus (Koehler) confined to the South Orkneys and A. curvidens
Mortensen known only from the Antarctic Peninsula. Two species, A.
nimrodiuna (Koehler) and A. ingens Koehler are known only from East
Antarctica while A . shackletoni Koehler and A . bidens Mortensen
appear to be circum-Antarctic. It seems probable that most (if not
all) of the species of Abatus brood their young in the sunken dorsal
petals of the female. This habit has been recorded for A . nimrodi,
A. shackletoni and A . bidens (Amaud, 1964) and A. ingelzs (Koehler,
1926).
All records for species of this genus appear to be from depths less
than 700 m. If the habit of larval brooding has always been part of
the generic makeup, the dispersal mechanism must have been slow
along comparatively shallow water shelves. Given time (and this seems
to have been abundantly available for Abatus) this seems to have been
no barrier to dispersal.
The genus Amphipneustes is even more strictly Antarctic than
Abatus. One species A. koehleri Mortensen occurs off South Georgia
and Shag Rocks. A. sirnilis Mortensen occurs off the Antarctic Peninsula
and off the South Orkneys. The other species are all confined to the
107
gonads. Spawning takes place in the southern winter, somewhere between May and December. The ova are of relatively small size (about
125 p) and this suggests indirect development. From the evidence of
echinoplutei collected on earlier expeditions, and almost certainly
belonging to this species, Sterechinw probably develops feeding echinopluteus larvae during the summer. Plankton samples taken throughout the year a t McMurdo Sound failed to produce any echinoplutei.
From the available evidence it appears that oocytes take from 18 to
24 months to reach maturity, spawning occurs in winter between May
and December and that early embryonic development is slow, so that
echinopluteus larvae are finally produced in the summer, when maximum plant food is available. The larval habitat is presumed to be close
to the bottom.
Members of the family Schizasteridae comprise some of the most
typical Antarctic animals. The genus Abatus with ten species is confined to the Antarctic and Subantarctic with an incursion into the
coastal waters of Argentina. One species A. cordatus (Verrill) has been
recorded only from the vicinity of Kerguelen and Heard Island. Three
species, A. agassizi (Pfeffer), A. cavernosus (Philippi) and A. philippi
L o v h have been recorded from East Antarctica, the Antarctic Peninsula (except for agussizi), south Georgia and Southern South America,
with A . cavernosus and A . philippi extending to about 36'5. Two
species have a restricted distribution in West Antarctica, with A.
elongatus (Koehler) confined to the South Orkneys and A. curvidens
Mortensen known only from the Antarctic Peninsula. Two species, A.
nimrodiuna (Koehler) and A. ingens Koehler are known only from East
Antarctica while A . shackletoni Koehler and A . bidens Mortensen
appear to be circum-Antarctic. It seems probable that most (if not
all) of the species of Abatus brood their young in the sunken dorsal
petals of the female. This habit has been recorded for A . nimrodi,
A. shackletoni and A . bidens (Amaud, 1964) and A. ingelzs (Koehler,
1926).
All records for species of this genus appear to be from depths less
than 700 m. If the habit of larval brooding has always been part of
the generic makeup, the dispersal mechanism must have been slow
along comparatively shallow water shelves. Given time (and this seems
to have been abundantly available for Abatus) this seems to have been
no barrier to dispersal.
The genus Amphipneustes is even more strictly Antarctic than
Abatus. One species A. koehleri Mortensen occurs off South Georgia
and Shag Rocks. A. sirnilis Mortensen occurs off the Antarctic Peninsula
and off the South Orkneys. The other species are all confined to the