General Features of Dinoflagellate Material Collected by the "Anton Bruun"
159
the oceanic region whereas the second most strongly represented genus, Peridinium, was
much more restricted to neritic regions.
Tropical waters are characterized by a great diversity of dinophysoid genera, and it is
amongst these that bizarre morphological elaborations are found, particularly within the
rarely observed genus Histioneis (Figs. 4e, 6e). The most common of the dinophysoid
genera in tropical waters is Ornithocercus, of which O. quadratus (Fig. 5 c) is the most
widely distributed species.
Various species of the genus Pyrocystis (emended by TAYLOR, 1972b) are common,
and in particular, P. pseudonoctiluca, P. fusiformis and P. hamulus. This genus is also
interesting because of the strong bioluminescence produced by some of its members
Latitude
IO·N
~O· ®
@.10·S $
20·S
30·S
40·S
]
200
' "
i. 300
•
Q
400
500
Sialion$
321
326 325
324 323 322 321
3Z0 319
31S 311
600~ ____________________________________ ~~=-_ ___ ~~~~ __________ ~-LJ
Fig. 3. Profile of isotherms within the upper 600 m from the 75° E meridional stations occupied on
"Anton Bruun" cruise V (NE monsoon). G: Ceratium gravidum. D: Histioneis dolan
(SWIFT and TAYLOR, 1967; ZERNOVA, 1967), making them one of the commonest causes
of bioluminescence in oceanic tropical waters.
Some genera usually thought to be rare, such as Kofoidinium and Cladopyxis, were
quite common in the material. In the case of the former, not being thecate in the usual
sense, it becomes somewhat deformed by preservation, but not unrecognizably so.
However, it has probably been missed in the past, however tempting it might be to attribute its presence to a migration from the Mediterranean from which it has been commonly
recorded. It has also been considered to be a "shade genus" (e.g. HALIM, 1967), which
might account for its rarity in collections taken from shallow depths.
The "Anton Bruun" material did not contain examples of a rare genus, Brachydinium,
described from the SW Indian Ocean (TAYLOR, 1963, 1967) which, until recently, might
have been considered endemic to the region. LEGER (1971) has encountered B. capitatum
quite frequently in the western Mediterranean. Again, it is impossible to attribute this to
migration in view of the likelihood of its being overlooked by previous authors.
To this author's knowledge no species of parasitic dinoflagellates have been recorded
from the Indian Ocean prior to the present study, due, no doubt, to the fact that no one
has looked for them. Although no special attempt to observe them was made nevertheless
Amoebophrya ceratii was identified from within Peridinium steinii, and Blastodinium
spinulosum was found free in a sample (it typically inhabits the gut of copepods).
159
the oceanic region whereas the second most strongly represented genus, Peridinium, was
much more restricted to neritic regions.
Tropical waters are characterized by a great diversity of dinophysoid genera, and it is
amongst these that bizarre morphological elaborations are found, particularly within the
rarely observed genus Histioneis (Figs. 4e, 6e). The most common of the dinophysoid
genera in tropical waters is Ornithocercus, of which O. quadratus (Fig. 5 c) is the most
widely distributed species.
Various species of the genus Pyrocystis (emended by TAYLOR, 1972b) are common,
and in particular, P. pseudonoctiluca, P. fusiformis and P. hamulus. This genus is also
interesting because of the strong bioluminescence produced by some of its members
Latitude
IO·N
~O· ®
@.10·S $
20·S
30·S
40·S
]
200
' "
i. 300
•
Q
400
500
Sialion$
321
326 325
324 323 322 321
3Z0 319
31S 311
600~ ____________________________________ ~~=-_ ___ ~~~~ __________ ~-LJ
Fig. 3. Profile of isotherms within the upper 600 m from the 75° E meridional stations occupied on
"Anton Bruun" cruise V (NE monsoon). G: Ceratium gravidum. D: Histioneis dolan
(SWIFT and TAYLOR, 1967; ZERNOVA, 1967), making them one of the commonest causes
of bioluminescence in oceanic tropical waters.
Some genera usually thought to be rare, such as Kofoidinium and Cladopyxis, were
quite common in the material. In the case of the former, not being thecate in the usual
sense, it becomes somewhat deformed by preservation, but not unrecognizably so.
However, it has probably been missed in the past, however tempting it might be to attribute its presence to a migration from the Mediterranean from which it has been commonly
recorded. It has also been considered to be a "shade genus" (e.g. HALIM, 1967), which
might account for its rarity in collections taken from shallow depths.
The "Anton Bruun" material did not contain examples of a rare genus, Brachydinium,
described from the SW Indian Ocean (TAYLOR, 1963, 1967) which, until recently, might
have been considered endemic to the region. LEGER (1971) has encountered B. capitatum
quite frequently in the western Mediterranean. Again, it is impossible to attribute this to
migration in view of the likelihood of its being overlooked by previous authors.
To this author's knowledge no species of parasitic dinoflagellates have been recorded
from the Indian Ocean prior to the present study, due, no doubt, to the fact that no one
has looked for them. Although no special attempt to observe them was made nevertheless
Amoebophrya ceratii was identified from within Peridinium steinii, and Blastodinium
spinulosum was found free in a sample (it typically inhabits the gut of copepods).