330
c. V. KURIAN: Cumacea of the Indian Ocean
waters. It is also remarkable that all the specimens of the IOBC collection come from the
stations near the coast-7 of the stations located off Gujarat, 3 off the SW coast of India
and 1 near the Malayan coast (Fig. 1). The specimens belong to the families Bodotriidae,
Holostylidae, Diastylidae, Pseudocumatidae and Nannastacidae.
The second series of specimens were received from the Smithsonian Institution having
been collected by RV "Anton Bruun" and RV ''Te Vega" during the period 1963 -1965,
from the Indian Ocean and adjacent seas. This collection consists of 43 samples and a
total of 502 well-preserved specimens. These specimens were collected from the intertidal
region to a depth of 2125 m and from a variety of substrata ranging from clay to rock.
While some of the specimens were collected by hand, others were obtained by using
rock dredge, shrimp trawl, Agassiz trawl and Menzies trawl. The specimens vary in length
from 1.2 mm to 15 mm and belong to the families Sympodammatidae, Bodotriidae,
Leuconidae, Diastylidae, Holostylidae, Nannastacidae and Campylaspididae. Most of the
shore collections are represented by very small specimens belonging to the genus
Nannastacus BATE. While mud and clay deposits yielded very few specimens, the rich
collections came from sand deposits. It is interesting to note that both series of collections
recorded cumacea specimens off the Gujarat coast. The systematics of the species collected
are dealt with separately.
From the study of the ecology of the specimens obtained during the HOE the following
conclusions can be drawn: All cumacea specimens obtained in the Indian Ocean samples
were from the nearshore waters. The 11 stations of the IOBC collections were located
on the west coast of India and Pakistan and the Malaya coast. The specimens of the
Smithsonian collections which were obtained mostly from benthos samples were also
obtained from the nearshore waters on the east coast of Africa, Red Sea, west coast of
India and Singapore strait. The IOSN samples were taken from 200 m upward and so
they actually missed the cumacea in the deeper water layers.
The HOE collections have definitely shown that the cumacea are essentially benthic
organisms and that their appearance in the open water is accidental. However, some of
the plankton nets which reached very near the bottom caught a few of the specimens.
The mass migration of cumacea as reported by JONES (1955, 1956) along the west coast
of Africa and their occurrence in large numbers in the plankton is attributed to low
oxygen concentration in the bottom water. Experiments conducted in the laboratory show
that Gigacuma halei KURIAN, the large species of cumacea that occurs in the inshore
waters of India, could tolerate very low oxygen content and that they migrate from the
bottom only when the dissolved oxygen content of the bottom water falls below 0.6 mll-l.
The total absence of cumacea in the IOSN samples taken in the open sea during the
day or during the night clearly shows that they are incapable of surviving in the upper
waters for any considerable length of time and that they usually remain on the bottom
or near the bottom of the sea. The cumacea are capable of living at great depths and in
the present collections 2 specimens of Campylaspis sp. were obtained from a depth of
2125 m off Madagascar with the Menzies trawl. However, cumacea are abundant on a fine
sandy bottom with a small percentage of silt, and rare in coarse sand and clay deposits.
Like many other benthic organisms they are more prevalent at shallow depths and as
depth increases their number decreases. The collections from Nosy-Be are mostly very
small specimens of 1.2 to 2.5 mm belonging to the genus Nannastacus BATE.
c. V. KURIAN: Cumacea of the Indian Ocean
waters. It is also remarkable that all the specimens of the IOBC collection come from the
stations near the coast-7 of the stations located off Gujarat, 3 off the SW coast of India
and 1 near the Malayan coast (Fig. 1). The specimens belong to the families Bodotriidae,
Holostylidae, Diastylidae, Pseudocumatidae and Nannastacidae.
The second series of specimens were received from the Smithsonian Institution having
been collected by RV "Anton Bruun" and RV ''Te Vega" during the period 1963 -1965,
from the Indian Ocean and adjacent seas. This collection consists of 43 samples and a
total of 502 well-preserved specimens. These specimens were collected from the intertidal
region to a depth of 2125 m and from a variety of substrata ranging from clay to rock.
While some of the specimens were collected by hand, others were obtained by using
rock dredge, shrimp trawl, Agassiz trawl and Menzies trawl. The specimens vary in length
from 1.2 mm to 15 mm and belong to the families Sympodammatidae, Bodotriidae,
Leuconidae, Diastylidae, Holostylidae, Nannastacidae and Campylaspididae. Most of the
shore collections are represented by very small specimens belonging to the genus
Nannastacus BATE. While mud and clay deposits yielded very few specimens, the rich
collections came from sand deposits. It is interesting to note that both series of collections
recorded cumacea specimens off the Gujarat coast. The systematics of the species collected
are dealt with separately.
From the study of the ecology of the specimens obtained during the HOE the following
conclusions can be drawn: All cumacea specimens obtained in the Indian Ocean samples
were from the nearshore waters. The 11 stations of the IOBC collections were located
on the west coast of India and Pakistan and the Malaya coast. The specimens of the
Smithsonian collections which were obtained mostly from benthos samples were also
obtained from the nearshore waters on the east coast of Africa, Red Sea, west coast of
India and Singapore strait. The IOSN samples were taken from 200 m upward and so
they actually missed the cumacea in the deeper water layers.
The HOE collections have definitely shown that the cumacea are essentially benthic
organisms and that their appearance in the open water is accidental. However, some of
the plankton nets which reached very near the bottom caught a few of the specimens.
The mass migration of cumacea as reported by JONES (1955, 1956) along the west coast
of Africa and their occurrence in large numbers in the plankton is attributed to low
oxygen concentration in the bottom water. Experiments conducted in the laboratory show
that Gigacuma halei KURIAN, the large species of cumacea that occurs in the inshore
waters of India, could tolerate very low oxygen content and that they migrate from the
bottom only when the dissolved oxygen content of the bottom water falls below 0.6 mll-l.
The total absence of cumacea in the IOSN samples taken in the open sea during the
day or during the night clearly shows that they are incapable of surviving in the upper
waters for any considerable length of time and that they usually remain on the bottom
or near the bottom of the sea. The cumacea are capable of living at great depths and in
the present collections 2 specimens of Campylaspis sp. were obtained from a depth of
2125 m off Madagascar with the Menzies trawl. However, cumacea are abundant on a fine
sandy bottom with a small percentage of silt, and rare in coarse sand and clay deposits.
Like many other benthic organisms they are more prevalent at shallow depths and as
depth increases their number decreases. The collections from Nosy-Be are mostly very
small specimens of 1.2 to 2.5 mm belonging to the genus Nannastacus BATE.