Larval anisakids parasitizing the blue whiting, Micromesistius poutassou, from Motril Bay in the Mediterranean region of southern Spain A. Valero * , J. MartõÂn-Sa Ânchez, E. Reyes-Muelas and F.J. Adroher Departamento de Parasitologõ Âa, Facultad de Farmacia, Universidad de Granada, E-18071 Granada, Spain Abstract A total of 301 blue whiting, Micromesistius poutassou Risso, 1826, ranging in length from 17 to 28 cm, from Motril Bay (Mediterranean coast, south Spain) were examined for anisakid nematodes, as these ®sh are common items in the Spanish Mediterranean diet. Three anisakid species were morphologically identi®ed with a total prevalence of 10.63%. Anisakis simplex s.l. Rudolphi, 1809 had a prevalence value of 6.65%, compared with 2.66% for A. physeteris Baylis, 1923 and 2.33% for Hysterothylacium aduncum Rudolphi, 1802. Variations in prevalence values with season and host size are discussed. Allozyme markers (leucine aminopeptidase-1) were used to identify anisakid nematodes assigned to the A. simplex complex and all examined larvae were found to correspond genetically to A. pegref®i Nascetti et al., 1986. Introduction Anisakids are present in many marine teleosts and the consumption of commercial ®sh, containing third larval stages (L3) of some anisakid species, constitutes a potential risk for public health. With reference to ®sh infections, a number of authors have studied the role of marine zooplankton in the transmission of anisakids (Kùie, 1993a; Kùie et al., 1995; Marcogliese, 1995), although ®sh may also become infected as a result of predation of other ®sh infected with L3. Experimental studies on the infection of marine and freshwater ®sh have shown that the larvae reach the body cavity by penetrating the wall of the stomach or pyloric caecum, infect the general body cavity a few hours later and the musculature after a few days (Smith, 1974). In some ®sh, such as the herring, the number of larvae of Anisakis simplex in the musculature increases after storage (Smith & Wootten, 1975). However, Wootten & Smith (1976) and Smith (1984) showed no migration from the viscera into the ¯esh of blue whiting once the host is dead. The presence of anisakid larvae in Micromesistius poutassou has been previously reported (Wootten & Smith, 1976; Bussmann & Ehrich, 1979; Smith, 1984; Petter & Maillard, 1988; Ruiz-Valero et al., 1992; Kùie, 1993b). The aim of this survey was to study anisakid infections of the blue whiting, as this ®sh is frequently consumed in Spain. Materials and methods A total of 301 blue whiting (Micromesistius poutassou, family Gadidae) from Motril Bay in southern Spain (Mediterranean Sea) were studied from February 1996 to January 1997. Fish lengths ranged from 17 to 28 cm. Once measure- ments of total length were made, the ®sh were dissected, and the free anisakid larvae collected from the body cavity. The viscera, inner organs, and ventral and dorsal musculature were then separately treated with a pepsin- HCl solution (pH 2±2.3) at 378C, for 2±3 h (modi®ed after McGladdery, 1986). After the larvae were isolated, they were washed with 0.9% NaCl solution and examined under a light microscope. Morphological identi®cation of the anisakids was undertaken using features described by Hartwich (1974), Yoshinaga et al. (1987), Petter & Maillard Journal of Helminthology (2000) 74, 361±364 361 * Fax: 34 958 243862 E-mail: fparasi@ucartuja.ugr.es