Diet preferences of the Aglajidae: a family of cephalaspidean gastropod predators on tropical and temperate shores

Andrea Zamora-Silva,Manuel António E Malaquias

doi:10.1017/s0025315415000739

Andrea Zamora-Silva, Manuel António E Malaquias

Open Access

https://doi.org/10.1017/s0025315415000739

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Abstract

Aglajidae is a family of tropical and temperate marine Cephalaspidea gastropod slugs regarded as active predators. In order to better understand their food habits and trophic interactions, we have studied the diet of all genera through the examination of gut contents. Specimens were dissected for the digestive tract and gut contents were removed and identified by optical and scanning electron microscopy. Our results confirmed that carnivory is the only feeding mode in aglajids and showed a sharp preference for vagile prey (94% of food items). We suggest that the interaction between crawling speed, presence of sensorial structures capable of detecting chemical signals from prey, and unique features of the digestive system (e.g. lack of radula, eversion of the buccal bulb, thickening of gizzard walls) led aglajid slugs to occupy a unique trophic niche among cephalaspideans, supporting the hypothesis that dietary specialization played a major role in the adaptive radiation of Cephalaspidea gastropods.

Highlights

Aglajidae is a diverse group of predominantly shallow-water cephalaspidean gastropods with an extensive degree of morphological and colour variation (Rudman, 1971, 1972a, b, c, 1974, 1978; Gosliner, 1980, 2008)
Food items were found in the gut of 11 out of the 32 species studied and in 24 of the 92 specimens dissected, corresponding to 26% of the specimens analysed (Table 1): one specimen of Aglaja and Nakamigawaia, three specimens of Navanax, four specimens of Chelidonura, Philinopsis and Odontoglaja, and seven of Melanochlamys
With the exception of the studies by Paine (1963, 1965) on the diet of the genus Navanax, knowledge about dietary preferences of aglajid slugs is based on sparse records included in general works about the diversity or morphological aspects of the Aglajidae (e.g. Tchang-Si, 1934; Marcus, 1961; Marcus & Marcus, 1966; Blair & Seapy, 1972; Rudman, 1972a, b, 1978; Pennings, 1990; Pennings et al, 2001; Padilla et al, 2010; Gosliner, 2011; Camacho-Garcıa et al, 2013; see Table 2)

Summary

Introduction

Aglajidae is a diverse group of predominantly shallow-water cephalaspidean gastropods with an extensive degree of morphological and colour variation (Rudman, 1971, 1972a, b, c, 1974, 1978; Gosliner, 1980, 2008). The family contains seven recognized genera and approximately 80 species worldwide distributed in tropical, sub-tropical and temperate shores. They are mostly found in soft bottom habitats and alga tufts around rocky shores, coral reefs and seagrass meadows (Thompson, 1977; Martınez et al, 1993; Nakano, 2004; Valdes et al, 2006; Gosliner et al, 2008; Camacho-Garcıa et al, 2013; Costello et al, 2013; Bouchet, 2014; Malaquias, 2014). A recent phylogenetic hypothesis of the Aglajidae confirmed the monophyly of the genera Aglaja, Melanochlamys, Nakamigawaia, Navanax, Odontoglaja and Philinopsis but suggested the paraphyly of Chelidonura which branched in three subclades (Camacho-Garcıa et al, 2013). The taxonomic status of Chelidonura is presently not clear and for the purpose of this research, we adopted its traditional definition (sensu Burn & Thompson, 1998)

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