258
MALCOLM R. CLARKE
With this in view the author examined several hundred otoliths of
ommastrephids taken off Madeira and Iceland. Very minute growth
laminations are detectable in Ommastrephes caroli, 0. pteropus and
Todarodes sagittatus off Madeira but no major fluctuations in these
could be detected; this one might expect in a warm region having
small variations in temperature, etc. In otoliths of Todarodes sagittatus
taken off Iceland, the Faroes and Norway the laminations show
periodic variations in thickness but the small size (less than 1 mm in
length) and crystal structure has prevented the relationship between
such variations and time, from being investigated.
Beaks of various cephalopod species were searched for laminations
by Tinbergen and Verwey (1945), Mangold-Wirz (1963b) and the author
(Clarke, 1965b). The author detected laminations in Moroteuthis
ingens beaks taken from Sperm whale stomachs. Laminations or
( ( microrings” vary in width and such variations are arranged in
(‘ cycles ”. The large number of microrings to a cycle (8-12) can be
shown to eliminate chance as the prime factor in causing the formation
of cycles. Although he has been unable to relate the cycles to time
it would seem that further work on cycles in the beaks of other species
may be fruitful.
An approximate idea of the size reached by oceanic squids in general
may be obtained by grouping species according to the known ( ( maximum ” mantle lengths in the various families (Table IV). It will then
be seen that only the architeuthids and one species of onychoteuthid
reach a mantle length greater than one metre. When the totale in
any size group are plotted as a cumulative percentage (Fig. 68) it may
be seen that over 60% of oegopsids have mantle lengths of less than
10 cm and over 90% of less than half a metre. However, it must be
remembered that sampling gear does not usually catch the larger
specimens so that these conclusions are necessarily biased towards the
. smaller squids.
In considering changes in form during growth we are somewhat
handicapped by inability to identify the earlier stages and by having
too few specimens to distinguish individual variation. However, by
considering change in the length of the arms, tentacles, head and
fins and the width of the body in relation to the mantle length it is
possible to draw some conclusions from the species figured here.
Table V shows how, with growth, the body becomes relatively wider
or narrower and the arms, tentacles, head and fin become relatively
longer or shorter. In some cases there is a reversal in the relationship
to the mantle length, during growth ( L S or S-L). It is apparent from
Table V that there is considerable diversity among the species. Further,
MALCOLM R. CLARKE
With this in view the author examined several hundred otoliths of
ommastrephids taken off Madeira and Iceland. Very minute growth
laminations are detectable in Ommastrephes caroli, 0. pteropus and
Todarodes sagittatus off Madeira but no major fluctuations in these
could be detected; this one might expect in a warm region having
small variations in temperature, etc. In otoliths of Todarodes sagittatus
taken off Iceland, the Faroes and Norway the laminations show
periodic variations in thickness but the small size (less than 1 mm in
length) and crystal structure has prevented the relationship between
such variations and time, from being investigated.
Beaks of various cephalopod species were searched for laminations
by Tinbergen and Verwey (1945), Mangold-Wirz (1963b) and the author
(Clarke, 1965b). The author detected laminations in Moroteuthis
ingens beaks taken from Sperm whale stomachs. Laminations or
( ( microrings” vary in width and such variations are arranged in
(‘ cycles ”. The large number of microrings to a cycle (8-12) can be
shown to eliminate chance as the prime factor in causing the formation
of cycles. Although he has been unable to relate the cycles to time
it would seem that further work on cycles in the beaks of other species
may be fruitful.
An approximate idea of the size reached by oceanic squids in general
may be obtained by grouping species according to the known ( ( maximum ” mantle lengths in the various families (Table IV). It will then
be seen that only the architeuthids and one species of onychoteuthid
reach a mantle length greater than one metre. When the totale in
any size group are plotted as a cumulative percentage (Fig. 68) it may
be seen that over 60% of oegopsids have mantle lengths of less than
10 cm and over 90% of less than half a metre. However, it must be
remembered that sampling gear does not usually catch the larger
specimens so that these conclusions are necessarily biased towards the
. smaller squids.
In considering changes in form during growth we are somewhat
handicapped by inability to identify the earlier stages and by having
too few specimens to distinguish individual variation. However, by
considering change in the length of the arms, tentacles, head and
fins and the width of the body in relation to the mantle length it is
possible to draw some conclusions from the species figured here.
Table V shows how, with growth, the body becomes relatively wider
or narrower and the arms, tentacles, head and fin become relatively
longer or shorter. In some cases there is a reversal in the relationship
to the mantle length, during growth ( L S or S-L). It is apparent from
Table V that there is considerable diversity among the species. Further,