The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


PARASITES OF DEEP SEA FISHES IN THE GULF OF EILAT

Asaf Lipshitz¹, Anton Post¹ and Arik Diamant²*

1 Interuniversity Institute for Marine Science, Hebrew University of Jerusalem

2 Israel Oceanographic and Limnological Research Ltd., National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel


Abstract

Parasites of coral reef fishes and commercially grown finfish have been studied for three decades in Eilat. However, fish that inhabit the deeper waters of the Gulf of Eilat (the dysphotic zone at depths> 150 m, where illumination is too slight and brief for effective photosynthesis) have generally been overlooked. Practically no information is available on fish parasites at this depth. Sixty-nine species of fish have been recorded in this habitat. Most are atypical of deep-sea species and, therefore, are considered to have evolved from shallow water species. The absence of true deep-sea species in the gulf is attributed to shallow sills at Bab el Mandeb and Tiran, which effectively exclude invasion by deep-sea species from the Indian Ocean. The present study is the first to characterize the parasites of endemic Red Sea fish fauna that inhabit this isolated and unique deep habitat.

We encountered a parasitic fauna that differs significantly from those of the typical ocean abyss and of Red Sea shallow-water fish. During 14 months, we collected parasites from 283 fish specimens belonging to 13 species. The overall prevalence of digestive tract helminths was 70.4-100%, with the infraclass Cestodaria being the most abundant group among the demersal and benthic host species. Four orders of cestodes were represented:Tetraphyllidea, Trypanorhyncha, Diphyllidea and Pseudophyllidea. Another highly prevalent group, particularly in demersal species (e.g.,Sparidae), was the phylum Nematoda. In contrast, other groups of gut helminths (e.g.,subclass Digenea and phylum Acanthocephala) and ectoparasites (infraclass Monogenea and subclass Copepoda) were extremely rare.

In this ongoing study, we are attempting to trace the origin of the parasites using both morphological characteristics and molecular phylogeny tools. We are examining the population biology and ecology of deep-sea organisms which are generally inaccessible for direct observation and, consequently, poorly known. The life cycles of selected parasites are being studied in vivo and molecular sequence analyses are being employed to overcome the constraints of experimental infections and artifacts such as near-identical morphology of unrelated species. This approach will likely form the basis for future studies of deep-sea fish and population-monitoring in the dysphotic and aphotic zones, as there is a regional trend to develop the deep-sea fishery.

*email: diamant@agri.huji.ac.il

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