ANTAROTIO BENTHOS
I69
advantage in Antarctic waters where planktonic food material is
extremely seasonal in production.
B. Mollusca
Several writers have commented upon the fact that a relatively
large percentage of Antarctic bivalves retain the young within the
mantle cavity until a definite shell is formed. Pelseneer (1903) noted
the habit in a few species. Burne (1920) recorded the incubation of
eggs either in the mantle cavity or in the gills of Adacnarca and Laternula. Soot-Ryen (1951, p. 42) commented, “ It is a striking fact that
nearly all the more littoral species, here considered to be old inhabitants
of the Antarctic region, are ovoviviparous. . . . These conditions are
observed in the families, Philobryidae, Gaimardiidae, and Cyamiidae,
in many genera of the superfamily Leptonacea, in some Carditidae and
by Laternula ellipticu. The reproduction of Thracia meridionalis and
Adamussium colbecki is not known.”
The incubatory habit has been definitely recorded in the following
species :
Philob~ya sublaevis (Soot-Ryen, 1961 ; Dell, 1964b, up to 175
Philobrya cupillata (Dell, 1964b, up to 400 young shells) ;
Adacnarca nitens (Burne, 1920; Soot-Ryen, 1951; Dell, 1964b;
Lissarca notorcadensis (Dell, 1964b) ;
Lissarca miliaris (Soot-Ryen, 1951) ;
Kidderia bicolor (Soot-Ryen, 1951) ;
Gaimardia trapesina trapesina (Lamarck) (Pelseneer, 1903) ;
Mysella arthari (Cooper and Preston) (Dell, 1964b) ;
Pseudokellya cardifwmis (Pelseneer, 1903) ;
Cyamiocardium crassilabrum (Dell, 196413, up to 44 developing
Laternula ellipticu (Burne, 1920) ;
Cyclocardia astartoidee (Probably).
developing eggs) ;
Nicol, 1966) ;
eggs) ;
The habit has been observed in many other members of the family
Philobryidae and is probably universal in the family.
The habit is thus comparatively common in Antarctic bivalves in
contrast to its relative scarcity in non-Antarctic members of the group.
All species of Philobrya apparently brood their eggs. Burne (1920)
showed that in Anutina (=Laternula) ellipticu a specially enclosed
supra-branchial chamber exists, “ roomy enough to provide accommodation for a very considerable mass of eggs ”. This feature is also
I69
advantage in Antarctic waters where planktonic food material is
extremely seasonal in production.
B. Mollusca
Several writers have commented upon the fact that a relatively
large percentage of Antarctic bivalves retain the young within the
mantle cavity until a definite shell is formed. Pelseneer (1903) noted
the habit in a few species. Burne (1920) recorded the incubation of
eggs either in the mantle cavity or in the gills of Adacnarca and Laternula. Soot-Ryen (1951, p. 42) commented, “ It is a striking fact that
nearly all the more littoral species, here considered to be old inhabitants
of the Antarctic region, are ovoviviparous. . . . These conditions are
observed in the families, Philobryidae, Gaimardiidae, and Cyamiidae,
in many genera of the superfamily Leptonacea, in some Carditidae and
by Laternula ellipticu. The reproduction of Thracia meridionalis and
Adamussium colbecki is not known.”
The incubatory habit has been definitely recorded in the following
species :
Philob~ya sublaevis (Soot-Ryen, 1961 ; Dell, 1964b, up to 175
Philobrya cupillata (Dell, 1964b, up to 400 young shells) ;
Adacnarca nitens (Burne, 1920; Soot-Ryen, 1951; Dell, 1964b;
Lissarca notorcadensis (Dell, 1964b) ;
Lissarca miliaris (Soot-Ryen, 1951) ;
Kidderia bicolor (Soot-Ryen, 1951) ;
Gaimardia trapesina trapesina (Lamarck) (Pelseneer, 1903) ;
Mysella arthari (Cooper and Preston) (Dell, 1964b) ;
Pseudokellya cardifwmis (Pelseneer, 1903) ;
Cyamiocardium crassilabrum (Dell, 196413, up to 44 developing
Laternula ellipticu (Burne, 1920) ;
Cyclocardia astartoidee (Probably).
developing eggs) ;
Nicol, 1966) ;
eggs) ;
The habit has been observed in many other members of the family
Philobryidae and is probably universal in the family.
The habit is thus comparatively common in Antarctic bivalves in
contrast to its relative scarcity in non-Antarctic members of the group.
All species of Philobrya apparently brood their eggs. Burne (1920)
showed that in Anutina (=Laternula) ellipticu a specially enclosed
supra-branchial chamber exists, “ roomy enough to provide accommodation for a very considerable mass of eggs ”. This feature is also