Jeopardy: host and parasite lessepsian migrants from the Mediterranean coast of Israel

Abstract

The defining feature of the fauna off the Mediterranean coast of Israel has been the mass establishment of migrant species from the Red Sea that entered through the Suez Canal. Of approximately 300 species that have been identified as Lessepsian migrants, 40 are decapod crustaceans (Galil , 1992). Churybdis longicollis Leene, found in the Red Sea (Leene, 1938), the Persian Gulf (Stephensen, 1946) and Madagascar (Guinot, 1966), was first recorded in the Mediterranean in 1954 from the Bay of Mersin, Turkey (Holthuis, L961). Since then, it has been recorded all along the Levant coast, from Egypt to the southern coast of Turkey (Lewinsohn and Holthuis, 1986). Off the Israeli coast, C. longicollis is common on sandy-mud bottoms at25 60m and occasionally deeper, to a record of l35m (Gali l, 1992). Of the thousands of specimens of C. longicollis collected off the Israeli coast in over three decades, none was parasitized until 1992. Among the C. longicollis collected off Palmahim in October of 1992, a few had bulging yellow protuberances carried beneath the abdomen. Those protrusions were identified as the externae of a sacculinid rhizocephalan, Heterosaccus dollfu,ri, Boschma, previously known only from a few specimens from the Gulf of Suez (Galil and LliJ.tzen, 1995). This is the first reported instance of Lessepsian migration by a rhizocephalan. Subsequent collections at the same site in October 1993 and May and November 1994, conflrmed its presence (Galil and L;jtzen, 1995). In March 1995, H. dollfusi was found infesting C. longicollis on the easternmost part of the Anatolian coast (Enzenross, personal communication). lt seems that although the host crab had immigrated to the Mediterranean over forty years ago, the parasite has appeared only recently and is spreading rapidly. C. longicollis specimens were collected in October 1993 and in May and November 1994by the RiV Shikmona with a 1.15m wide beam trawl at depths of 31 36m in the course of a monitoring programme of a marine sewage outlet at Palmahim (Galil andLiJtzen, 1995). Each sample was made up of l6 trawls of identical duration, taken within a limited area. The material from all trawls was pooled. A total of 1l 15 Charybdls specimens was examined. Among these, 345 were