ANTABCITIC BENTHOS
161
to the habit in Paronuphis antarctica (Monro) of laying the eggs in one
clutch within the tube, where the developing young remain (Hartman,
1967~). It appears that a pygmy male is fixed to the female in this
species.
Potamethus scotiae (Pixell) (a sabellid) was found to incubate eggs
within the tube, as does Onuphis paucibranchis (Ehlers).
E. Nemertea
Joubin (1914) recorded what appears to be the first instance of egg
brooding in the Nemertea. In a species described by Joubin as Amphiporus incubator from Petermann Island, the females construct a cocoon
around themselves and seal it off. The eggs are laid inside the cocoon.
A most peculiar mechanism has been developed for fertilization which
in all other nemerteans is external. As the developing eggs swell inside
the female they gradually push out until they perforate the skin and
present a small surface of the egg membrane to the outside sea. At this
stage fertilization occurs.
About a hundred eggs are laid in the cocoon. On hatching the young
worms crawl on the inside eating egg membranes and other food
materials excreted by the female when the eggs are laid. The evidence
seems to show that the female does not survive. An allied species,
Amphiporus michelseni Joubin also incubates its eggs but in much
simpler fashion. The female secretes a parchment tube open at both
ends, in which the eggs are laid.
F. Reasons for incidence of viviparity
Discussions on the high incidence of viviparity amongst Antarctic
animals have usually been confined to the consideration of one group
of animals. A major difficulty in seeking to explain why viviparity is
so common in the Antarctic is that in general viviparity is not as well
marked in the Arctic. It cannot therefore be envisaged as a natural
response to cold water or “ difficult ” ecological conditions. The whole
concept of “ difficult ” conditions in the polar regions must surely
derive from an anthropocentric viewpoint. No biologist aware of the
great diversity of life in Antarctic waters, the enormous bulk of organic
matter produced, and the close adaptations that have been made to the
main physical cyclic changes throughout the year, can surely believe
that this is not a “ successful ” biota. Rather than “ difficult ”, the
environment must be almost perfect for those organisms which have
adapted successfully to it. Wohlschlag’s work on the physiology of
Antarctic fishes almost indicates that Antarctic animals may be adapted
161
to the habit in Paronuphis antarctica (Monro) of laying the eggs in one
clutch within the tube, where the developing young remain (Hartman,
1967~). It appears that a pygmy male is fixed to the female in this
species.
Potamethus scotiae (Pixell) (a sabellid) was found to incubate eggs
within the tube, as does Onuphis paucibranchis (Ehlers).
E. Nemertea
Joubin (1914) recorded what appears to be the first instance of egg
brooding in the Nemertea. In a species described by Joubin as Amphiporus incubator from Petermann Island, the females construct a cocoon
around themselves and seal it off. The eggs are laid inside the cocoon.
A most peculiar mechanism has been developed for fertilization which
in all other nemerteans is external. As the developing eggs swell inside
the female they gradually push out until they perforate the skin and
present a small surface of the egg membrane to the outside sea. At this
stage fertilization occurs.
About a hundred eggs are laid in the cocoon. On hatching the young
worms crawl on the inside eating egg membranes and other food
materials excreted by the female when the eggs are laid. The evidence
seems to show that the female does not survive. An allied species,
Amphiporus michelseni Joubin also incubates its eggs but in much
simpler fashion. The female secretes a parchment tube open at both
ends, in which the eggs are laid.
F. Reasons for incidence of viviparity
Discussions on the high incidence of viviparity amongst Antarctic
animals have usually been confined to the consideration of one group
of animals. A major difficulty in seeking to explain why viviparity is
so common in the Antarctic is that in general viviparity is not as well
marked in the Arctic. It cannot therefore be envisaged as a natural
response to cold water or “ difficult ” ecological conditions. The whole
concept of “ difficult ” conditions in the polar regions must surely
derive from an anthropocentric viewpoint. No biologist aware of the
great diversity of life in Antarctic waters, the enormous bulk of organic
matter produced, and the close adaptations that have been made to the
main physical cyclic changes throughout the year, can surely believe
that this is not a “ successful ” biota. Rather than “ difficult ”, the
environment must be almost perfect for those organisms which have
adapted successfully to it. Wohlschlag’s work on the physiology of
Antarctic fishes almost indicates that Antarctic animals may be adapted