INTRODUCTION
Angelfishes (family Pomacanthidae) are very common and conspicuous reef fish with a circum-global distribution on tropical and warm temperate reefs. The French angelfish Pomacanthus paru (Bloch, 1787) inhabits coral reefs and rocky shores from Florida (USA) to Santa Catarina State (Southern Brazil) (Randall & Hartman, Reference Randall and Hartman1968; Ferreira et al., Reference Ferreira, Floeter, Gasparini, Ferreira and Joyeux2004), including Ascension Island (Maugé, Reference Maugé, Quero, Hureau, Karrer, Post and Saldanha1990). In Brazil, P. paru is the most abundant angelfish and shows a patchy distribution (Ferreira et al., Reference Ferreira, Floeter, Gasparini, Ferreira and Joyeux2004), living close to coralline or rocky substrate, being diurnal and usually wandering in pairs through their territory (Carvalho-Filho, Reference Carvalho-Filho1999).
Pomacanthids feed mainly on the structurally resilient and firmly attached benthic prey items avoided by most predators (Konow & Bellwood, Reference Konow and Bellwood2005), having sponges as the dominant item in the diet of several Holacanthus and Pomacanthus species, thus being historically considered spongivorous fish, with algae being usually a secondary item in their diet (Randall & Hartman, Reference Randall and Hartman1968; Hourigan et al., Reference Hourigan, Stantion, Motta, Kelley and Carlson1989; Wulff, Reference Wulff, Van Soest, Van Kempen and Braekman1994; Verdín et al., Reference Verdín, Carballo and Camacho2010). Contrastingly, more recent studies in Brazil considered P. paru an omnivorous benthic feeder, with more plasticity in their diet, which is mainly composed of algae and, secondarily, sponges (Batista et al., Reference Batista, Muricy, Andréa and Villaça2012).
The Scyphomedusa Chrysaora lactea Eschscholtz, 1829 is considered widespread and is one of the most common and most widely distributed Scyphozoans on the Brazilian south-eastern coast (Migotto et al., Reference Migotto, Marques, Morandini and Silveira2002), but little information is available on its biology (Morandini et al., Reference Morandini, Silveira and Cornelius2006). Here we report the first record of the feeding behaviour of a French Angelfish on the jellyfish C. lactea.
MATERIALS AND METHODS
The present observation was carried out at Queimada Pequena Island, Ilha Grande bay, Angra dos Reis, Rio de Janeiro State, (23°05′25.48″S 44°18′34.20″W), a subtropical region on the Brazilian south-eastern coast.
The observations were made during SCUBA dives, in January 2014. The sandy bottom was at a depth of 15 m and the water had 10 m visibility during the observations. The feeding activity was photographed between 9:30 and 10:00 h.
RESULTS
The predation on Chrysaora lactea individuals, measuring around 120 mm in umbrella diameter, occurred while one pair of Pomacanthus paru (around 40 cm in length) foraged on a rocky bottom covered by a great variety of sponges, tunicates and bryozoans, predominated by Palythoa carybaeorum – all of them yet to have been reported as food items to the fish species. At a certain point of the feeding activity, the pair moved up to the water column, at depths from 9 to 11 m, simultaneously preying on the jellyfish. After nibbling on it for around 2 min, other Pomacanthus paru joined the feeding activity. At the height of agitation, 14 specimens were accounted for as Pomacanthus paru (Figure 1A–C), but not all individuals had nibbled the new food item; similarly two individuals of Abudefduf saxatilis (Linnaeus, 1758), Pomacentridae (Figure 1B, C), and one Stephanolepis hispidus (Linnaeus, 1766), Monacanthidae (Figure 1A–C), also approached the action, although no nibbling activity by these species on the jellyfish was observed. Tissue damage on portions of the umbrella and velarium of the jellyfish, after the fish had ceased the activity, accounted for nearly 40% of the total body area.
Pomacanthus paru (Bloch, 1787) feeding on a Chrysaora lactea Eschscholtz, 1829 jellyfish. (A) Close at the P. paru feeding aggregation; (B) P. paru feeding on C. lactea with the presence of a Stephanolepis hispidus (Linnaeus, 1766) and an Abudefduf saxatilis (Linnaeus, 1758); (C) Total number of individuals involved in the action: P. paru (14), A. saxatilis (2) and S. hispidus (1).
DISCUSSION
Fish are the best documented group of jellyfish predators (Arai, Reference Arai2005), and most pelagic coelenterates feeders have a broader diet (Purcell & Arai, Reference Purcell and Arai2001). Pomacanthus paru corroborates this rule, with a broad diet composed of sponges, algae, bryozoans, zoantharians, gorgonians and tunicates (Cervigón, Reference Cervigón1993), a trait that is not shared by other Pomacanthid family members (Carvalho-Filho, Reference Carvalho-Filho1999; Konow & Bellwood, Reference Konow and Bellwood2005).
Jellyfish are well-recognized predators in food webs, however, as food items they are often overlooked for the easy digestibility of their tissue (Arai, Reference Arai2005). As many fish feed on such prey, it is expected to be an important accessory food item for generalist and opportunistic predators (Chaves et al., Reference Chaves, Feitosa and Pereira2010).
Other reports on the predation on Chrysaora lactea have been made: (1) at Santa Catarina, southern Brazil, involving the filefish Stephanolepis hispidus (Bonaldo et al., Reference Bonaldo, Krajewski and Sazima2004); (2) a more recent study at Arraial do Cabo, south-western Brazil, involving the butterfly fish Chaetodon striatus Linnaeus, 1758 (Chaves et al., Reference Chaves, Feitosa and Pereira2010). As in Bonaldo et al. (Reference Bonaldo, Krajewski and Sazima2004), we also observed herein the filefish S. hispidus, however, without any nibbling activity, probably due to the large size of the Pomacanthus paru. Not all individuals of Pomacanthus paru and the Abudefduf saxatilis nibbled the jellyfish, perhaps because they had less interest in the new food item or simply because of intraspecific competition, meaning they could not approach the prey.
The record presented herein could be a result of the higher abundance of the food source itself (during jellyfish blooms), thus becoming a constant and relatively easy prey to catch. Opportunistic feeding on a temporarily available item is reported for several fish (Lowe-McConnell, Reference Lowe-McConnell1987), mainly generalist species, thus indicating that these occasional items benefit those with some level of feeding plasticity, but the results seem to show that opportunistic feeding can also benefit species with some level of specialization.
Pomacanthus paru is known to feed on the zoanthids Palythoa carybaeorum Duchassaing & Michelotti, 1860 (Francini-Filho & Moura, Reference Francini-Filho and Moura2010) and on sponges, both of which contain toxic substances, often as their main food, which makes them liable to feed on other toxic coelenterates.
This new record is further evidence for the feeding plasticity of the benthic omnivore Pomacanthus paru.
ACKNOWLEDGEMENTS
Authors would like to thank Abudefduf Atividades Subaquáticas for logistic support during fieldwork, and L.C.T. Chaves (Universidade Federal de Pernambuco) and M.R. Britto (Museu Nacional/UFRJ) for their suggestions on the manuscript. The study was supported by CAPES, grant no. 2346/2011 (PNPD Institucional) and CNPq.
