How females of Achtheinus spp. (Pandaridae: Siphonostomatoida) attach to their elasmobranch hosts with notes on their effects on the hosts' fins.

Susan M Dippenaar,Anine Jordaan

doi:10.14411/fp.2015.005

Abstract

Copepods of the genus Achtheinus Wilson, 1908 (Pandaridae) are parasites of elasmobranchs that attach to their fins, gill slits and around the nostrils. Specimens of Achtheinus pinguis Wilson, 1912 were collected and examined using histology and scanning electron microscopy to determine their way of attachment to the host and the possible effect on the host. They insert their antennae deep into the dermis of the shark's skin, which causes the most damage due to possible tissue compression and/or fibrosis as well as rupture of the connective tissue. Additionally, the presence of the copepod on the skin causes cell erosion of the epidermal cells and thus reduces the number of epidermal layers. The maxillipeds are used to attach to the placoid scales that cover the shark's skin and probably serve to keep the copepod and inserted antennae in position. This is accomplished by the insertion of the placoid scales into the flaccid corpus of the maxillipeds. Observed damage seems to be negligible to the shark apart from the possibility of secondary infection.

Highlights

Achtheinus Wilson, 1908 is a member of Pandaridae Milne-Edwards, 1840 with a widely debated taxonomic position and was synonymised with Perissopus Steenstrup and Lütken, 1861 by Cressey (1967)
The three species are morphologically very similar with very subtle differences in the length of the caudal rami, the stoutness and curvature of the antennal claw, the size and deflection of the posterior process of the maxilliped subchela and length and width of the protopod of leg 4 as well as those of the cephalic shield (Izawa 2010). These three species have been reported from a variety of elasmobranch hosts with A. oblongus restricted to the eastern Pacific Ocean off North America, A. dentatus restricted to the eastern Pacific off the Americas and A. pinguis reported from all three oceans (Izawa 2010)
MATERIALS AND METHODS Copepods were collected from a variety of host species caught in the shark nets off the KwaZulu-Natal coast of South Africa and from sharks caught during the Fisheries Branch of the Department of Agriculture, Forestry & Fisheries’s (DAFF) demersal cruises off the south and west coasts as well as from hosts caught by commercial fishermen off the west coast

Summary

Introduction

Achtheinus Wilson, 1908 is a member of Pandaridae Milne-Edwards, 1840 with a widely debated taxonomic position and was synonymised with Perissopus Steenstrup and Lütken, 1861 by Cressey (1967). The three species are morphologically very similar with very subtle differences in the length of the caudal rami, the stoutness and curvature of the antennal claw, the size and deflection of the posterior process of the maxilliped subchela and length and width of the protopod of leg 4 as well as those of the cephalic shield (Izawa 2010) These three species have been reported from a variety of elasmobranch hosts with A. oblongus restricted to the eastern Pacific Ocean off North America, A. dentatus restricted to the eastern Pacific off the Americas and A. pinguis reported from all three oceans (Izawa 2010). Since the structure of the antennae and maxillipeds are mostly similar in the three Achtheinus species, it is expected that this will apply to all three species

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Conclusion