The role of lantern fish (Myctophidae) in the life-cycle of cetacean parasites from western Mediterranean waters Paula Mateu a,n , Valentina Nardi b , Natalia Fraija-Fernández a , Simonetta Mattiucci b , Luis Gil de Sola c , Juan Antonio Raga a , Mercedes Fernández a , Francisco Javier Aznar a a Unitat de Zoologia Marina, Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, PO Box 22085, Valencia 46071, Spain b Department of Public Health Sciences and Infectious Diseases, Section of Parasitology, “Sapienza University of Rome”, P. le Aldo Moro, 5, 00185 Rome, Italy c IEO, Puerto pesquero s/n, Ap. 285, 29640 Fuengirola, Spain article info Article history: Received 10 July 2014 Received in revised form 21 October 2014 Accepted 23 October 2014 Available online 7 November 2014 Keywords: Lantern fish Myctophidae Cephalopoda Anisakis pegreffii Anisakis physeteris Helminth Life-cycle abstract Myctophids (lantern fish) and cephalopods play a key role in trophic webs from the continental slope and oceanic waters linking the zooplankton to top predators. Many cetaceans feed on both lantern fish and cephalopods, and such prey would thus be expected to bridge the trophic gap in the life-cycles of helminths infecting cetaceans. However, information on the life-cycles of most of these helminths is extremely scanty. We examined the parasite fauna of myctophids and cephalopods in two areas from the western Mediterranean where at least 21 helminth taxa from cetaceans have been reported and both cetacean diversity and abundance is high. A total of 1012 individuals of 8 lantern fish species, namely, Ceratoscopelus maderensis, Lampanyctus crocodilus, Notoscopelus elongatus, Benthosema glaciale, Mycto- phum punctatum, Lobianchia dofleini, Diaphus holti and Hygophum benoiti, and 792 individuals of 2 cephalopod species, Alloteuthis media and Sepietta oweniana, were collected from the Gulf of Valencia and Alboran Sea (Spanish Mediterranean) during 2010–2012 and examined for larval helminths. All these species have been reported as prey for at least some cetacean species in the area. Only five helminth taxa were found. The nematodes Anisakis pegreffii and Anisakis physeteris were detected in N. elongatus and C. maderensis (overall prevalence for Anisakis: 8.1% and 0.5%, respectively). Their prevalence in N. elongatus was significantly higher than that from the other three myctophid species with n 450 individuals. A single individual of Hysterothylacium sp. was found in N. elongatus (prevalence: 0.5%) and Raphidascarididae gen. spp. in N. elongatus and L. crocodilus (prevalence: 20.3% and 0.7%, respectively). Juvenile didymozoid digeneans (Torticaecum type) were detected in N. elongatus and L. crocodilus (prevalence: 18.5% and 4.3%, respectively). Two unidentified cestode plerocercoids were collected from N. elongatus. Our study suggests, for the first time, that myctophids could play a role as paratenic hosts in the oceanic life-cycle of A. pegreffii and A. physeteris in the western Mediterranean. None of the other larvae identified at least to family level infect cetaceans, but some of them can be transmitted to large predatory fish. The extreme scarcity of such cetacean parasites in this, and previous parasitological surveys of mesopelagic fish and cephalopods is at odds with the key role of these preys in the diet of oceanic cetaceans. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Mesopelagic fishes, especially of the family Myctophidae (lan- tern fish), account for a high abundance and biomass in the continental slope and oceanic waters (Olivar et al., 2012). These fish prey mainly on small copepods, euphausiids, amphipods and decapods (Williams et al., 2001; Klimpel et al., 2008) linking the zooplankton to top predators, such as large cephalopods, fish and cetaceans (Olivar et al., 2012). Cephalopods also play a key trophic role because they, depending on ontogenetic stage and size, feed on small crustaceans or mesopelagic fish (Quetglas et al., 2010) and are, in turn, common prey of several top predators (Clarke, 1996; Boyle and Rodhouse, 2005). The diet of many cetaceans, especially of species exploiting offshore waters, is largely composed of mesopelagic fish and/or cephalopods (Clarke, 1996; Barlow et al., 2008). These prey could thus be expected to bridge the trophic gap in the life-cycles of parasites infecting cetaceans (Klimpel et al., 2008). However, Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsri Deep-Sea Research I http://dx.doi.org/10.1016/j.dsr.2014.10.012 0967-0637/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ34 963543685. E-mail address: paula.mateu@uv.es (P. Mateu). Deep-Sea Research I 95 (2015) 115–121