Zoological Studies 51(7): 905-912 (2012) Feeding Behavior of Spurilla sp. (Mollusca: Opisthobranchia) with a Description of the Kleptocnidae Sequestered from Its Sea Anemone Prey Agustín Garese1,*, Stella García-Matucheski2, Fabián H. Acuña1, and Claudia Muniain2 1Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICET, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350 (7600) Mar del Plata, Buenos Aires, Argentina 2Laboratorio de Ecología Química y Biodiversidad Acuática, Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de San Martín, Campus Miguelete (1650), San Martín, Pcia. Buenos Aires, Argentina (Accepted March 19, 2012) Agustín Garese, Stella García-Matucheski, Fabián H. Acuña, and Claudia Muniain (2012) Feeding behavior of Spurilla sp. (Mollusca: Opisthobranchia) with a description of the kleptocnidae sequestered from its sea anemone prey. Zoological Studies 51(7): 905-912. Cnidocysts are sequestered from cnidarian prey by aeolid nudibranchs and stored in the tips of their appendages (cerata). The kleptocnidae of 11 specimens of Spurilla sp. are described in detail. The types and relative abundances of prey cnidocysts in nudibranch cerata were highly variable, suggesting exclusive anemone consumption. Spirocysts and several types of microbasic p-mastigophores, microbasic b-mastigophores, and basitrichs were found in external and internal tissues of sea anemone prey. This is the 1st report of predation of aeolid Spurilla sp. on the sea anemones Antholoba achates, Metridium senile lobatum, and Parabunodactis imperfecta from the rocky intertidal of Patagonia (Chubut Province, Argentina) and on Anthothoe chilensis and Tricnidactis errans at Mar del Plata (Buenos Aires Province, Argentina). Photographs and digital videos of aeolidacean feeding behavior were recorded in situ and in aquaria. The purpose of this study was to provide valuable information on the diet of Spurilla sp. from Argentina using field observations and descriptions of the kleptocnidae. http://zoolstud.sinica.edu.tw/Journals/51.7/905.pdf Key words: Nudibranchia Aeolidiidae, Cerata, Sea anemone, Argentina. Nudibranchs are shell-less gastropods. 2009). Some authors also suggested that Their diverse color patterns, high diet specificity, nudibranchs incorporate immature cnidocysts, and mechanical and chemical defensive attributes which can complete maturation within the have attracted the attention of marine biologists cnidosacs (Naville 1926, Greenwood and Mariscal and biotechnologists (Su et al. 2009). Aeolid 1984b, Harris 1971 1973). nudibranchs are known to feed upon cnidarians Cnidarians have different types of cnidocysts, and are capable of sequestering the cnidocysts which form the cnidom (assemblage of cnidocysts of their prey. The cnidocysts are ingested, pass present in any cnidarian), and vary among species through the digestive diverticula, migrate to the tips even within their tissues (England 1991, Östman of the dorsal cerata, and are stored in a functional 2000, Fautin 2009). Many aeolid species are state in cnidosacs within specialized cells termed specific in the selection of cnidocysts, and the cnidophages (Grosvenor 1903, Conklin and types can vary according to the prey consumed, Mariscal 1977, Greenwood and Mariscal 1984a, which provides information about the feeding Greenwood 1988). The set of cnidocysts selected history of the nudibranch (Day and Harris 1978). by the aeolid is termed kleptocnidae (Greenwood Specific types of cnidocysts stored by nudibranchs *To whom correspondence and reprint requests should be addressed. E-mail:[email protected]; [email protected] 905 906 Garese et al. – Feeding Behavior and Description of the Kleptocnidae are poorly known, probably due to difficulties with Study of the kleptocnidae cnidocyst identification (Conklin and Mariscal 1977). Kleptocnidae were often supposed to be In total, 11 specimens of nudibranchs of defensive (Edmunds 1966, Harris 1973, Aguado Spurilla sp. were collected by hand from 4 rocky and Marín 2007), but direct observational and intertidal sites; Punta Gales, Larralde (Chubut experimental evidence does not fully support that Province), Punta Cantera, and La Estafeta (Mar del (Miller and Byrne 2000, Edmunds 2009, Penney et Plata, Buenos Aires Province). Three specimens al. 2010). were collected from each site, except from Spurilla sp. is an intertidal nudibranch Larralde, where only 2 were collected. Specimens recorded for the 1st time in Argentina by Muniain were fixed in 5% formaldehyde and subsequently (1997 2004); its distribution range extends transferred to ethanol. In the laboratory, cerata from Mar del Plata (Buenos Aires) to Chubut (Fig. 1A) were haphazardly removed from the (Patagonia). Preliminary studies on kleptocnidae animal, using fine-pointed forceps; ceras squashes of Spurilla sp. collected from Mar del Plata (Buenos were then prepared to study the kleptocnidae. At Aires) showed that this species incorporates least 3 cerata per individual were analyzed, and cnidocysts of the sea anemones Anthothoe at most 100 cnidocysts per ceras were identified chilensis (Lesson, 1830) and Tricnidactis errans and measured using a Zeiss Axiolab microscope De Oliveira Pires, 1987 (Garese et al. 2009). with oil immersion at 1000x magnification. When The present work focused on the diet of Spurilla the intended number of cnidocysts had not been sp. from Argentina using field observations and reached, more cerata (up to 10) were dissected kleptocnidae examination. until we had sampled 300 cnidocysts per individual. In total, 3247 capsules were identified and measured. Cnidocysts were classified MATERIALS AND METHODS according to England (1991). Statistically descriptive parameters, such as the size (length Nudibranch feeding behavior and width) and abundance of the different types of cnidocysts, were obtained using the R program Field observations to identify species of (R 2008). Finally, with those results and making sea anemone prey of Spurilla sp. were made comparisons with available information about the in the intertidal of Larralde and Punta Gales cnidae of common sea anemone species from the (Chubut Province), Punta Colorada (Río Negro sampled sites, we identified probable prey sources Province), Punta Cantera, and La Estafeta (Mar of the kleptocnidae found and the specific structure del Plata, Buenos Aires Province); all locations of the prey consumed by the aeolids. are in Argentina. Aquarium experiments were Voucher specimens were preserved at the conducted to study in detail the predation steps invertebrate collection (MACN-In) of the Museo of the aeolids on sea anemones from Chubut. Argentino de Ciencias Naturales “Bernardino Spurilla sp. specimens together with their prey Rivadavia” (Buenos Aires). Spurilla sp., 1 were collected by hand from intertidal rocks and specimen, 20 Jan. 2006, MACN-In: 37723, transferred to the laboratory in containers with Larralde (42°24'14"S, 64°18'19"W, Chubut natural seawater under controlled conditions of Province); 1 specimen, 12 June 2009, MACN- temperature, aeration, and salinity. Sea anemones In: 39307, La Estafeta, Mar del Plata (38°15'S, were first placed in the center of the aquaria; after 57°56'W, Buenos Aires Province). 2 h of acclimation, groups of 4 nudibranchs were introduced, 1 group at a time, into 3 aquaria, each one containing specimens of the sea anemone RESULTS species. Observations lasted 3 h and allowed us to describe in detail the sequence of the nudibranch Nudibranch feeding behavior attack, its preference for a particular structure of the sea anemone, and the behavioral response of Specimens of Spurilla sp. were observed the prey. After the experiments, specimens were in situ preying on Antholoba achates (Drayton preserved in 75% ethanol for taxonomic studies. in Dana, 1846) at Punta Colorada (Río Negro) Photographs and digital videos of nudibranchs and (Fig. 1B), Parabunodactis imperfecta Zamponi & their prey were taken in situ and in aquaria. Acuña, 1992 at Larralde (Chubut) (Fig. 1C), and on patches of A. chilensis and T. errans at Punta Zoological Studies 51(7): 905-912 (2012) 907 Cantera (Mar del Plata) (Fig. 1D). contracted its column, withdrew its tentacles Aeolids were found in rocky intertidal tide inside, and began to detach its pedal disc from pools, most of the time behind rocks in darkness, the substrate. The nudibranch finished feeding where sea anemones were common. Laboratory at the top of the sea anemone column, without feeding experiments confirmed predation of touching or ingesting the tentacles. We observed Spurilla sp. on A. achates (Fig. 1E) and P. that several nudibranchs fed together on the same imperfecta (Fig. 1F). After an acclimation period, sea anemone, and similar feeding behaviors were the sea anemones had become tightly attached to observed by individuals in the 3 aquaria. the substrate. When we introduced aeolids into the aquaria, they moved immediately towards the Study of the kleptocnidae prey. Initial contact involved the oral tentacles and rhinophores of the nudibranch with the prey Specimens of Spurilla sp. from Punta Gales pedal disc. The nudibranchs extended their (Chubut) had 8 types of cnidocysts. Specimen 2 buccal mass and attached it to the sea anemone showed the most diverse kleptocnidae (6 types), to begin feeding. Meanwhile, the sea anemone followed by specimen 3 (5 types) and specimen (A) ecc (B) e cp cc cs sm dd (C) (D) (E) (F) Fig. 1. (A) Cerata structure of Spurilla sp. (ecc = expelled