aqua, Journal of Ichthyology and Aquatic Biology Juvenile grunt (Haemulidae) mimicking a venomous leatherjacket (Carangidae), with a summary of Batesian mimicry in marine fishes Ivan Sazima Departamento de Zoologia and Museu de História Natural, Caixa Postal 6109, Universidade Estadual de Campinas, 13083-970 Campinas, São Paulo, Brazil. E-mail: [email protected] - Fax: +55 (19) 3289 3124 Accepted: 16.10.2002 Keywords Brasilien. Beim Durchschwimmen offener Gebiete Protective resemblance, mimicry, Oligoplites verhalten sich junge Pomadasys ramosus (Haemuli- palometa, Pomadasys ramosus, venomous model, dae), genau so wie das mutmaßliche Model, junge juveniles, tidal streams, western Atlantic Oligoplites palometa (Carangidae) , eine Art mit Gift- drüsen in der Rücken- und Afterflosse, und sie ähneln Abstract diesem auch sehr. Eine Zusammenfassung von 24 A presumed example of facultative Batesian mimicry veröffentlichten Beispielen Betesscher Mimikry unter between a grunt and a leatherjacket is described from Meeresfischen zeigt an, dass die meisten Arten (83,3 tidal streams and mangrove zones in south-eastern %) giftige Modelle, drei Arten (12,5 %) toxische Mod- Brazil. While moving over open areas or when threat- elle, und ein Modell dass weder giftig noch toxisch ist, ened, juvenile Pomadasys ramosus (Haemulidae) nachahmen. closely resemble, and behave like, their presumed venomous model, juvenile Oligoplites palometa Résumé (Carangidae), a species with venom glands in its dor- Est décrit un exemple présumé de mimétisme sal and anal spines. A summary of 24 published batésien facultatif entre un Grogneur et un Carange examples of Batesian mimicry in marine fishes shows originaires de fleuves soumis aux marées et de zones that most species (83.3%) mimic venomous models, de mangrove au sud-est du Brésil. Lorsqu'ils se meu- three species (12.5%) imitate poisonous models and vent en zones découvertes ou qu'ils sont menacés, only one species (4.1%) mimics a model which is nei- les Pomadasys ramosus (Haemulidae) juvéniles ther venomous nor poisonous. ressemblent fort à et se comportent comme leur mod- èle venimeux présumé, l'Oligoplites palometa Resumo (Carangidae) juvénile, une espèce à glandes Um presumível exemplo de mimetismo Batesiano vénéneuses dans ses épines dorsales et anales. Un facultativo, entre uma espécie de corcoroca e uma résumé de 24 exemples publiés de mimétisme espécie de guaivira, é descrito de manguezais no batésien chez les poissons de mer montre que la plu- sudeste do Brasil. O juvenil de Pomadasys ramosus part des espèces (83,3%) imitent des modèles ven- (Haemulidae), quando se desloca por áreas abertas imeux, trois espèces (12,5%) s'inspirent de modèles ou quando ameaçado, apresenta grande semelhança toxiques et une seule espèce (4,1%) imite un modèle de colorido e comportamento com o seu presumido qui n'est ni venimeux ni toxique. modelo peçonhento, o juvenil de Oligoplites palometa (Carangidae), uma espécie com glândulas de Sommario peçonha em seus acúleos dorsais e anais. Um Viene descritto un esempio di presunto mimetismo sumário de 24 casos publicados sobre mimetismo facoltativo batesiano tra un grugnitore e un carangide, Batesiano entre peixes marinhos mostra que a maio- osservato presso le correnti di marea e le zone a man- ria das espécies (83.3%) imita modelos peçonhentos, grovie del Brasile sudorientale. Quando si muovono in três espécies (12.5%) imitam modelos venenosos e aree aperte oppure si sentono minacciati, i giovani di apenas uma espécie (4.1%) imita um modelo que não Pomadasys ramosus (Haemulidae) prendono le sem- é peçonhento nem venenoso. bianze e il comportamento del loro presunto modello velenoso rappresentato dall’individuo giovane di Oligo- Zusammenfassung plites palometa (Carangidae), una specie provvista di Hier wird ein mutmaßliches Beispiel von fakultativer, ghiandole velenifere nei raggi spinosi dorsali e anali. Betesscher Mimikry beschrieben, zwischen einem Esaminando 24 esempi di mimetismo batesiano in Grunzer und einer Stachelmakrele, in einem Gehzeit- pesci marini si osserva che la maggior parte delle enfluss sowie in Mangrovenzonen, im südöstlichen specie (83.3%) ha come modello specie velenose per 61 aqua vol. 6 no. 2 - 2002 Juvenile grunt mimicking a venomous leatherjacket, with a summary of Batesian mimicry in marine fishes contatto, mentre tre (12.5%) imitano specie che sono count. In addition, I seined a stretch of about 100 m in velenose per ingestione e solo una (4.1%) imita un another stream. modello non velenoso. Voucher specimens of both species were deposited in the fish collection of the Museu de História Natural, Introduction Universidade Estadual de Campinas (ZUEC). Colour Batesian mimicry involves a harmless species, the transparencies taken both in the habitat and in field mimic, which resembles a harmful or unpalatable one, aquaria were scanned and deposited in the ZUEC fish the model (Wickler, 1968; Edmunds, 1974). Several photo file (numbers as for specimens). cases of presumed protective mimicry between Measurements used throughout are total length (TL) marine fishes have been proposed, some of them dis- for both species, standard length (SL) for the grunt, and puted and others generally accepted (summaries in fork length (FL) for the leatherjacket. Microscopic sec- Randall & Randall, 1960; Randall & Kuyter, 1989; tions of anal and dorsal spines of Oligoplites were pre- Smith-Vaniz et al., 2001). Perhaps one of the best- pared using routine histological methods, and stained known examples is the blenny Ecsenius bicolor (Day, with haematoxylin/eosin to demarcate the venom 1888), which mimics Meiacanthus atrodorsalis (Gün- glands (Halstead et al., 1972; Sazima & Uieda, 1979). ther, 1877) a fangblenny able to deliver a toxic bite The summary of recorded cases of Batesian mim- (Losey, 1972; Springer & Smith-Vaniz, 1972; Smith- icry is drawn from the literature, with one additional Vaniz et al., 2001). Toxic (venomous or poisonous) example based on field observations. Species names models include species in fish families as diverse as follow Eschmeyer (1998, updated 2000 in Froese & the Blenniidae, Scorpaenidae, Trachinidae, and Pauly, 2001). Tetraodontidae (Randall & Randall 1960; Randall & Kuiter, 1989). Among jacks (Carangidae), species of leatherjackets of the genera Scomberoides Lacepède, 1801 and Oligoplites Gill, 1863 have dorsal and anal spines with venomous glands and are able to inflict a painful wound (Halstead et al., 1972; Sazima & Uieda, 1979; pers. obs.). However, no species of leatherjacket has hitherto been proposed as a venomous model in any case of protective resemblance. During studies on the natural history of mangrove-dwelling fishes in south- eastern Brazil, I came upon what I regard as an exam- ple of facultative Batesian mimicry involving the grunt Pomadasys ramosus (Poey, 1860) as the mimic and the leatherjacket Oligoplites palometa (Cuvier, 1832) as the model. The morphological and behavioural sim- ilarities between the two species are described herein. In addition, a summary of Batesian mimicry in marine fishes is provided, with comments. Methods Juvenile grunts (P. ramosus) and leatherjackets (O. palometa) were opportunistically recorded from Feb- ruary to December 2001 in several tidal streams and mangrove zones in the region of Ubatuba (23° 23- 30'S), São Paulo, south-eastern Brazil. The behaviour of the fishes was recorded during daylight in the course of 11 surface and 3 underwater snorkelling session (Sazima 1986), using “local animal” and “all occurrences” samplings (Lehner 1979): a total of about 13 hours of field observations. Observations were focused on particular behaviours (e.g., foraging, flight) and associated colour changes related to the Fig. 1. Pomadasys ramosus juveniles: above, an individ- bottom type and potentially camouflaging back- ual about 15 mm TL drifting slowly close to the bottom in ground. In one tidal stream I counted the numbers of its mangrove habitat; below, a larger juvenile (22.4 mm individuals of both species on two occasions by slowly SL, ZUEC 5537) showing the dark, camouflaged, colour wading for one hour through clear, shallow water at pattern while hovering close to plant debris (pho- ebb tide, covering approximately 300 m during each tographed in field aquarium). Photos by I. Sazima. aqua vol. 6 no. 2 - 2002 62 Ivan Sazima Results both fishes occasionally darted at prey, which they Juvenile grunts, Pomadasys ramosus, bear a close engulfed before resuming their hovering. resemblance to juvenile leatherjackets, Oligoplites While close to decaying plant fragments and other palometa, both in colour pattern and behaviour, and dark debris, both species often adopted a dark colour were found together in tidal streams and mangrove pattern, which camouflaged them against the back- zones. The two counts produced similar proportions of ground (Fig. 1, see Sazima & Uieda, 1979 for a figure models to mimics: three leatherjackets and two grunts of O. palometa). When camouflaged in this dark attire, in one count and three leatherjackets and one grunt in both species moved slowly close to the bottom and the other. The seine catch yielded five leatherjackets their swimming resembled the movement of water- and two grunts. logged plant debris drifting in the water current. How- Both fish species may hover in a head-down, oblique ever, while moving over open, detritus-free, light- and curved posture (Fig. 1), although the leatherjacket coloured sandy bottom, both the leatherjacket and the was observed