Distribution of Hydromedusae in the Indian Ocean
281
Botrynema brucei
l.
Vl
~ temperature 1°C)
'"
0
0
~
CJ oxygenlmI021-1) u0
° E
CD
_
salinity 1%0$)
~CD
M
~~~ D
N
~
N
Lf)
~Lf)
M
~
-.t
M
;:!
M
I rl I I
c:!M
M
$2
N
CON
M
~
CD
M
-.t~
N
0 0
160 33.b 35t b 35td 3530 378 sto"on
15 2 1
1 2 1 No. of spec.
Fig. 6. Distribution of Botrynema brucei, in relation to salinity, temperature and dissolved oxygen,
showing its stenotopic properties
Botrynema brucei, Halicreas minimum, Halitrephes maasi, Colobonema sericeum, Crossota alba (Fig. 6).
Divergent adaptation of species, especially congeneric species, is noteworthy. Thus,
Koellikerina fasciculata, an immigrant from the high-salinity Mediterranean, is found
in the Arabian Sea while K. constricta, K. elegans, K. multicirrata and K. octonemalis
occupy different low-salinity niches in the Bay of Bengal. A similar situation arises between
Euphysora annulata (restricted to the Arabian Sea), E. furcata (an Antarctic species), and
E. bigelowi (widely distributed). Other examples may be quoted for the genera Zanclea,
Aequorea (Table 1), Bougainvillia and others.