Rev. Esp. Herp. (2006) 20:105-117 Diet and helminth parasites in the Gran Canaria giant lizard, Gallotia stehlini MIGUEL A. CARRETERO,1 VICENTE ROCA,2 JUAN E. MARTIN,2 GUSTAVO A. LLORENTE,3 ALBERT MONTORI,3 XAVIER SANTOS 3 & JUDIT MATEOS 3 1 CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal 2 Departament de Zoologia, Facultat de Ciències Biològiques, Universitat de València, c/ Dr. Moliner 50, 46100 Burjassot, València, Spain (e-mail: [email protected]) 3 Departament de Biologia Animal (Vertebrats), Facultat de Biologia, Universitat de Barcelona, Avgda. Diagonal 645, 08028 Barcelona, Spain Abstract: Diet and helminth fauna were analysed in Gallotia stehlini (Schenkel, 1901), a giant lacertid lizard endemic to Gran Canaria (Canary Islands, Spain) in order to explore eventual relationships between both traits. This species is mainly herbivorous, eating a large proportion of plant matter (occurrence 97.1%) including not only seeds but also leaves and other vegetative parts. Helminth fauna included many helminth species typical of herbivorous reptiles, and intestinal helminth diversity was high. A comparison with other lacertids suggests that both traits, diet and helminth fauna, result from an adaptation to insular conditions. Canarian Gallotia, a separate lineage evolving for a long time in insularity, constitutes the most modified lacertid group in this sense. Key words: Canary Islands, diet, lizards, parasites. Resumen: Dieta y helmintos parásitos en el lagarto gigante de Gran Canaria, Gallotia stehlini. –Se analizó la dieta y la helmintofauna de Gallotia stehlini (Schenkel, 1901), un lagarto gigante endémico de Gran Canaria (Islas Canarias, España), para explorar una eventual relación entre ambos parámetros. Esta especie de lagarto es eminentemente herbívora, con consumo de una alta proporción de materia vegetal (97.1%) que incluyó no sólo semillas sino también hojas y otras partes vegetativas. Su helmintofauna incluyó muchas especies típicas de reptiles herbívoros, y la diversidad de helmintos intestinales fue elevada. La comparación con otros lacértidos sugiere que ambos, dieta y helmintofauna, resultan de una adaptación a condiciones insulares. Los lagartos canarios del género Gallotia, un linaje que ha evolucionado durante largo tiempo en condiciones de insularidad, constituyen el grupo de lacértidos más profundamente modificado en este sentido. Palabras clave: dieta, Islas Canarias, lagartos, parásitos. INTRODUCTION Pharyngodonidae than carnivores. In this family of nematodes, PETTER & QUENTIN Previous studies have reported a relationship (1976) recognised two evolutionary lineages between diet (herbivorous vs. carnivorous) (each one of them with different genera) and helminth parasites in reptilian hosts parasitising carnivorous or herbivorous (PETTER & QUENTIN, 1976; ROCA, 1999; reptiles. Moreover, the structure of helminth MARTIN et al., 2005). In particular, communities is richer and more diverse in herbivorous reptiles are infected by different herbivorous reptiles (ROCA & HORNERO, 106 M.A. CARRETERO et al. 1991). It has been suggested (see ROCA, Islands, together with G. simonyi 1999) that the monoxenous life cycle typical (Steindachner, 1889), G. bravoana Hutterer, of the Pharyngodonidae favours the infection 1985 and G. intermedia Hernández et al., of herbivorous reptile hosts because they have 2000 (MATEO, 2002a, b; MATEO & PÉREZ- more opportunities to accidentally eat eggs MELLADO, 2002; RANDO, 2002; MARTÍN & deposited in plants through faecal pellets. RANDO, 2006). However, G. stehlini is not Moreover, the increase of plant matter directly related with the other giant lizards consumed provides a suitable environment but rather constitutes a branch that separated for the development of a more rich and early in the phylogeny of this genus (MACA- abundant helminth fauna (PETTER & MEYER et al., 2003). A general description of QUENTIN, 1976; ROCA, 1999; ROCA et al., its helminth community has been recently 2005). BOUAMER & MORAND (2003) published and its infracommunities and suggested that the evolution of the component communities have been analysed Pharyngodonidae in the Testudinidae (MARTIN & ROCA, 2004a). However, little is (herbivore hosts) is also related to the habitat known about the diet of this species (BARQUÍN selection in the host caecum. et al., 1986; MOLINA-BORJA, 1986; NARANJO Species or populations of the lizard family et al., 1991) and thus, the diet-parasite Lacertidae living on islands show a higher relationships of this lacertid lizard have not trend towards herbivory than comparable been assessed. Nevertheless, the large size of populations on the mainland (VAN DAMME, this lizard, insular distribution, herbivory, and 1999) and, when evolutionary history under the composition and structure of its helminth insular conditions is long enough, true community make this lizard species useful for specialisations involving anatomy and such analyses. Hence, the aim of this paper is behaviour have been demonstrated to investigate the relationship between (CARRETERO et al., 2001; OLESEN & VALIDO, helminth and diet parameters within G. 2003; CARRETERO, 2004; HERREL et al., stehlini, specifically addressing the following 2004a). The genus Gallotia constitutes an issues: i) characterisation of the patterns of early separated branch of lacertids endemic helminth community richness and diversity; to the Canary Islands where they arrived soon ii) characterisation of the patterns of after the formation of the archipelago (about dominance and diversity in the diet; iii) 23 m.y.a.) and diversified in isolated analysis of sexual variation in diet and conditions for more than 12 m.y. (MACA- parasites, and iv) determination of eventual MEYER et al., 2003). Since all extant relationships between helminths and diet. members of this genus consume plant matter Concerning this last point, we would expect to some extent (ROCA, 1999), some of the that G. stehlini, belonging to an old insular living forms have been used previously for lineage and having a large size, should studies of the host diet-parasites relationships harbour complex herbivorous helminth (MARTIN et al., 2005; ROCA et al., 2005). faunas (including some helminth species In this study, the diet and helminth typical of herbivorous reptiles). parasites of the Gran Canaria giant lizard Gallotia stehlini (Schenkel, 1901) have been MATERIALS & METHODS analysed. This species, naturally distributed only in Gran Canaria island, is one of the four Lizard sampling was carried out in Gran extant “giant” lizards living in the Canary Canaria, a volcanic island (1560 km2; 1948 m DIET-HELMINTHS RELATIONSHIPS IN Gallotia stehlini 107 maximum elevation) with a central position in would be minimal when comparing, as here, the Canarian Archipelago, located off the north the same digestive compartment between west coast of Africa, at 27º 44’-28º 10’ N species or classes (CARRETERO & LLORENTE, and 15º 23’-15º 49’ W. The island is 2001). microclimatically and ecologically heteroge- A total of 33 digestive tracts were neous, with strong differences between the analysed for helminths under a binocular north and the south, which has a warmer dissecting microscope. Helminths were climate (FERNÁNDEZ-PALACIOS & MARTÍN, counted, washed in saline, fixed, mounted 2001). A total of 33 adult G. stehlini (13 using standard techniques, and identified to males, 20 females) were collected by hand in species. Unfortunately, due to logistic Aldea Blanca (27º 50’ N and 15º 28’ W, 200 constraints, information on both diet and m above sea level), located in the south- parasites could be obtained only from 18 eastern part of the island in July 1994 (see specimens. Although based on a limited data MARTIN & ROCA, 2004a). This locality is set due to conservation reasons, the results of considered representative of the typical the present work confirm prior data on other habitat occupied by this species, which species of Gallotia (see Discussion) and are consists of xerophytic areas dominated by useful for understanding eco-parasitological volcanic rocks and scattered bushes. relationships among Canarian lizards. Lizards were transported to the laboratory, The descriptors of diet and parasite fauna sacrificed with an overdose of chloroform were: prevalence or occurrence (%P, and dissected immediately. Snout vent length percentage of lizards with prey/parasite (SVL) was measured with a digital calliper to items), relative abundance (%N, percentage the nearest 0.01 mm. No sexual size of each prey or parasite item), and resource dimorphism was found in our sample of use index (JOVER, 1989). The latter index Gallotia stehlini from Gran Canaria (13 emphasizes the homogeneity as a criterion for males: 121.67 ± 7.33 mm, range 71-161 mm; evaluating the importance of the different 20 females: 128.08 ± 4.63 mm, range 96-205 OTUs (CARRETERO et al., 2001; CARRETERO, mm; t37 = 0.78, p = 0.33, n.s.). Digestive 2004). The use of descriptive eco- tracts were removed and 24 stomach contents parasitological terms follows BUSH et al. were suitable for diet analysis. The minimum (1997). number criterion was used for prey counting The following parameters were calculated of animal items and seeds (CARRETERO, for both helminth infracommunity and diet 2004). Other plant matter was counted as for the entire lizard sample as well as fragments because herbivorous lizards pierce separated by sexes: absolute abundance leave and tile pieces in the same