164
F.]. R. TAYLOR:
north and south with the seasons, lying between 1 r to 20
0
S during the NE monsoon, and
14 0 to 16 0 S in the SW monsoon.
Dinophysis miles represents an extreme morphological modification of the genus
Dinophysis in that it possesses an elongate dorsal process which can be greatly enlarged
(Fig. 5 b) so that it exceeds the antapical process in length. It exists in 3 principal forms
which differ in the length, shape and angel of the processes, especially the dorsal process
(see BOHM, 1935). These forms are here termed varieties because 2 can occur
sympatrically. The intermediately developed variety, D. miles var. indica, occurs over
the whole Indian Ocean region. In the Red Sea a short-horned variety has been observed
which, as it is the type variety, should be named D. miles var. miles (= D. miles var. maris
rubri). It has never been observed away from the Red Sea-western Araban Sea area. In
the vicinity of the East Indies a third variety exists: D. miles var. schroeteri (Fig. 5 b)
which possesses the greatest extension of dorsal process and most divergent angle
between the dorsal and antapical processes. Despite the currents flowing freely through
the various East Indian straits, this variety appears to be completely confined to the
eastern Andaman Sea, East Indies and SE Asian waters (see distribution shown on Fig. 1).
It co-occurs with the variety indica at many stations so that it is not apparently a phenotypic variant caused by an environmental gradient.
Such an unusual phenomenon as this deserves further investigation to fully evaluate it.
In fact, many authors may have seen evidence of it but unfortunately this cannot be
determined with certainty because of an error in the widely-used taxonomic work by
SCHILLER (1933) in which D. miles var. schroeteri was included with D. miles var. indica.
Thus the distributional pattern for D. miles var. indica shown by SUKHANOVA (1962 a, b)
suggests that it was the former variety. Also, the record from the Gulf of Tonkin by
KUSJMINA (1971) might also be D. miles var. schroeteri.
In this study no species were found to be particularly associated with the highsalinity water in the northern and western Arabian Sea. The dominant dinoflagellates in
that area (P. pseudonoctiluca, various ceratia and peridinia) were also found quite
commonly elsewhere. In the studies on Ceratium distribution carried out by PETERS
(1932), STEEMANN NIELSEN (1934, 1939) and GRAHAM (1941) no species were found
to show a good correlation with salinity per se except where the salinities were very low,
causing a decline in species.
3. Seasonal Features
Unlike the other major oceans, the tropical and subtropical regions of the Indian Ocean
were known, even prior to the HOE, to be subject to considerable seasonal fluctuations.
Recently OWEN and ZEITZSCHEL (1970) have shown marked seasonal variations in
the primary productivity of the eastern tropical Pacific. Unfortunately, due to the divergent
interests of participating scientists, although the general scheme of longitudinal lines of
stations was maintained on the "Anton Bruun" cruises, this seasonal aspect became subordinated to other aims and the resultant plankton samples are difficult to analyse from
the seasonal point of view. RYTHER et al. (1966), in their presentation of the primary
productivity data from the cruises, chose to ignore this aspect in favour of the total point
of view. As most of the open-ocean stations were occupied during the SW monsoon or
inter-monsoon periods, this may be a reasonable approach for the demonstration of the
grossest features. However, as cruises I (Andaman Sea/Bay of Bengal) and V (55 0 and
75
0
E meridians and a short line in the northern Arabian Sea from India to the Gulf of
F.]. R. TAYLOR:
north and south with the seasons, lying between 1 r to 20
0
S during the NE monsoon, and
14 0 to 16 0 S in the SW monsoon.
Dinophysis miles represents an extreme morphological modification of the genus
Dinophysis in that it possesses an elongate dorsal process which can be greatly enlarged
(Fig. 5 b) so that it exceeds the antapical process in length. It exists in 3 principal forms
which differ in the length, shape and angel of the processes, especially the dorsal process
(see BOHM, 1935). These forms are here termed varieties because 2 can occur
sympatrically. The intermediately developed variety, D. miles var. indica, occurs over
the whole Indian Ocean region. In the Red Sea a short-horned variety has been observed
which, as it is the type variety, should be named D. miles var. miles (= D. miles var. maris
rubri). It has never been observed away from the Red Sea-western Araban Sea area. In
the vicinity of the East Indies a third variety exists: D. miles var. schroeteri (Fig. 5 b)
which possesses the greatest extension of dorsal process and most divergent angle
between the dorsal and antapical processes. Despite the currents flowing freely through
the various East Indian straits, this variety appears to be completely confined to the
eastern Andaman Sea, East Indies and SE Asian waters (see distribution shown on Fig. 1).
It co-occurs with the variety indica at many stations so that it is not apparently a phenotypic variant caused by an environmental gradient.
Such an unusual phenomenon as this deserves further investigation to fully evaluate it.
In fact, many authors may have seen evidence of it but unfortunately this cannot be
determined with certainty because of an error in the widely-used taxonomic work by
SCHILLER (1933) in which D. miles var. schroeteri was included with D. miles var. indica.
Thus the distributional pattern for D. miles var. indica shown by SUKHANOVA (1962 a, b)
suggests that it was the former variety. Also, the record from the Gulf of Tonkin by
KUSJMINA (1971) might also be D. miles var. schroeteri.
In this study no species were found to be particularly associated with the highsalinity water in the northern and western Arabian Sea. The dominant dinoflagellates in
that area (P. pseudonoctiluca, various ceratia and peridinia) were also found quite
commonly elsewhere. In the studies on Ceratium distribution carried out by PETERS
(1932), STEEMANN NIELSEN (1934, 1939) and GRAHAM (1941) no species were found
to show a good correlation with salinity per se except where the salinities were very low,
causing a decline in species.
3. Seasonal Features
Unlike the other major oceans, the tropical and subtropical regions of the Indian Ocean
were known, even prior to the HOE, to be subject to considerable seasonal fluctuations.
Recently OWEN and ZEITZSCHEL (1970) have shown marked seasonal variations in
the primary productivity of the eastern tropical Pacific. Unfortunately, due to the divergent
interests of participating scientists, although the general scheme of longitudinal lines of
stations was maintained on the "Anton Bruun" cruises, this seasonal aspect became subordinated to other aims and the resultant plankton samples are difficult to analyse from
the seasonal point of view. RYTHER et al. (1966), in their presentation of the primary
productivity data from the cruises, chose to ignore this aspect in favour of the total point
of view. As most of the open-ocean stations were occupied during the SW monsoon or
inter-monsoon periods, this may be a reasonable approach for the demonstration of the
grossest features. However, as cruises I (Andaman Sea/Bay of Bengal) and V (55 0 and
75
0
E meridians and a short line in the northern Arabian Sea from India to the Gulf of