Journal of the Marine Biological Association of India

The Ocean-strider Halobates (Heteroptera: Gerridae).

Volume 15 Issue 1

Lanna Cheng

Abstract

The genus Holobates, first described by Eschscholtz (1822) was monographed b> Herring|(1961), with notes on biology and known distribution of the 38 known species and a key for their separation. More recently Savilov (1967) provided additional information on the distribution of the Pacific species. Our knowledge on the biology and ecology of these unique oceanic insects is very scanty.

Ten species of Halobates have been recorded from the Indian Ocean and the adjacent seas. These include 2 oceanic species, H. inicans and H. germanus, which only occur in the open ocean many miles away from land, and 8 species confined to coastal waters. H. micans, a circumtropical species, is widely distributed between the latitudes of 30°N to 30°S in the Atlantic between the latitudes of 10°N to 10°S in the Pacific; and between 20° N to 20° S in the Indian Ocean. H. germanus is also widely distributed in the three oceans; in the Indian Ocean it often occurs together with H. micans in ar«!as north of latitude 25°S. Most of the coastal species (H. alluadi, H. formidabilis, H. flaviventris, H. galatea, H. hayanus, H. poseidon H. proavus, and H. teihys) are rather restricted in their distribution in the Indian Ocean area, but H. fiaviventrls is found from the Bay of Bengal to the coast of Tanzania.

Relatively few of the zooplankton samples collected during the International Indian Ocean Expedition contain Halobates, since the sampling methods used were not originally designed to collect samples from the sea surface. However, these samples have provided some additional information on the biology and distribution of the two Indian Ocean striders Halobates germanus was collected at 26 stations between latitudes 20°N and 23°S and between longitudes 38°E and 97°E. From the samples analysed there appears to be no definite breeding season. Nymphs were collected in most months (except June - September and December). Females collected in any month were found to have their abdomens packed with well developed eggs. Halobates micans was collected only from 15 stations between latitudes 19°N and 10°S and between longitudes 61 °E and 93°E.

Our knowledge of the limits of distribution of oceanic Halobates is still very incomplete. From available data they seem to be largely determined by the climatic conditions of the water, and there is no doubt that wind as well as water current play an important role in their distribution. An understanding of the relative importance of these two dispersive factors may help us to understand the distributions not only of Halohates but also of other pleuston organisms.

Date : 31-08-1973