versión On-line ISSN 0718-1957
Rev. biol. mar. oceanogr. v.45 n.2 Valparaíso ago. 2010
Revista de Biología Marina y Oceanografía
Vol. 45, Nº2: 359-363, agosto de 2010
A parasitic copepod, Neoalbionella sp. (Lernaeopodidae), on the southern lanternshark Etmopterus granulosus (Etmopteridae) off Juan Fernández Archipelago, Chile
Un copépodo parásito, Neoalbionella sp. (Lernaeopodidae), en el tiburón linterna Etmopterus granulosus (Etmopteriidae) del archipiélago Juan Fernández, Chile
Sara M. Rodríguez1, José L. Luque1 and Mario George-Nascimento2
1Departamento de Parasitologia Animal, Universidade Federal Rural de Rio de Janeiro, Caixa Postal 74508, Seropédica, RJ, Brasil, CEP 23851-970
2Departamento de Ecología Costera, Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Casilla 297, Concepción, Chile
The morphology of an as yet undetermined Neoalbionella species is described from specimens collected from the second dorsal fin of the southern lanternshark Etmopterus granulosus, caught at a submerged ridge off Juan Fernández Archipelago, Southeastern Pacific Ocean, Chile. Two features of the females suggest that this may be an undescribed species: the presence of one secondary denticle on the claw of the maxilliped, and three setae on the outer lobe of the maxillule. However, males are essential to describe new species of Lernaeopodidae but were not found. This is a new host and geographical record of Neoalbionella sp. off the Pacific coast of South America.
Key words: Parasites, elasmobranch hosts, Southeastern Pacific, taxonomy
Four lernaeopodid copepod species parasitic on 6 elasmobranch hosts have been reported from the southeastern Pacific Ocean, off Chile (Muñoz & Olmos 2007). These are: Lernaeopoda tenuis Castro & Baeza, 1986 and Pseudolernaeopoda caudocapta Castro & Baeza, 1986 on Triakis maculata (Castro & Baeza 1986), Brianella corniger Wilson, 1915 on Psammobatis sp., Sympterygia brevicaudata and on an unidentified host species (Wilson 1915, Atria 1967, Castro & Baeza 1987), and Pseudocharopinoides myliobatidos Castro & Baeza, 1987 on Myliobatis chilensis (Castro & Baeza 1987). Kabata (1979) transferred four Lernaeopoda species to a new genus Albionella, mainly on the basis of the adult male morphology. In addition, Kabata (1986), Rubec & Hogans (1988), Benz & Izawa (1990), and Benz (1991a, b) noted that females of Albionella species could be separated from Lernaeopoda spp. by the presence of one secondary denticle on the claw of the maxilliped. In contrast, Lernaeopoda females have two or more secondary denticles present. The number of setae on the outer lobes of the maxillule is different: Albionella have three setae but there are two in Lernaeopoda. To date, six species have conformed to the generic diagnosis of Albionella. However, Özdikmen (2008) changed the name of nine crustacean genera, including Albionella which was changed to Neoalbionella: so its species became Neoalbionella globosa (Leigh-Sharpe, 1918), N. centroscyllii (Hansen, 1923), N. longicaudata (Hansen, 1923), N. etmopteri (Yamaguti, 1939), N. fabricii (Rubec & Hogans, 1988), and N. kabatai (Benz & Izawa, 1990).
Here, we report for the first time a Neoalboniella species from southern lanternshark Etmopterus granulosus (Günther, 1880) (Squaliformes: Etmopteridae) specimens collected off Juan Fernández Archipelago, southeastern Pacific Ocean, Chile.
MATERIAL AND METHODS
Thirty two southern lanternsharks Etmopterus granulosus were caught at depths between 450 and 800 m in the submerged ridges off Juan Fernández Archipelago (31°15'S, 71°47´W), southeastern Pacific Ocean, Chile, during April-May 2006. Collected parasite specimens were deposited at the Museum of Zoology, University of Concepción, Chile (MZUC 33513).
The copepods were fixed and stored in 70% ethanol until processing, and then cleared and dissected in lactic acid. Drawings were made with the aid of a camera lucida on a H600 (40-1000x) light microscope and a binocular dissecting scope Coleman (10-40x). Two specimens were examined under scanning electron microscopy (SEM) to reveal anatomical characteristics. Terminology conforms to that of Boxshall & Halsey (2004). Scientific and common name of the host are in accordance with Compagno et al. (2005). Measurements are in mm and ranges in parentheses.
RESULTS AND DISCUSSION
Four of 32 southern lanternsharks harbored Neoalbionella sp. and only ovigerous females of the copepod were found (prevalence 16.6%, abundance 0.125).
Description (based on 4 female specimens). Total body length (cephalothorax tip to tip of caudal rami) ranged between 5.8 and 6.2 mm. The cephalotorax dorsoventrally depressed and reflexed ventrally towards trunk (Fig. 1A, 2A, 2B). The dorsal cephalothoracic shield indistinct, truncated anteriorly, approximately 44.5% overall body length and the border between cephalothorax and trunk is delimited dorsally and ventrally by cuticular indentation. The anterior portion of trunk wrinkled and posterolateral boundaries rounded. The trunk dorsoventrally flattened, pyriform in dorsal and ventral view (Fig. 2B). The caudal rami located ventral to oviduct orifices, and each is armed with one long naked apical seta proximally (Fig. 2I). The egg sacs located dorsolateral to caudal rami (Fig. 2A), each is multiseriate and longer than the trunk. The antennule four-segmented (length = 0.068-0.070, Fig. 2C) and armed with setal elements as follows (base to apex): 0, 1, 1, 5. The antenna biramous (Fig. 2D) with an unarmed sympod; the exopod unsegmented with a lobated denticulate apical and outer margin (length = 0.34-0.35); with one small apical lateral spiniform element (Fig. 2D). The endopod two-segmented (length = 0.097-0.098), with the first segment bearing a small medial denticulate patch, and the second bearing one claw-like and three small, spiniform elements apically. The mouth cone and mandible are typical of the Lernaeopodidae (Fig. 2H), with a mandibular formula P1, S1, P1, S1, P1, S1, B4 (length = 0.114-0.116, maximum width = 0.045-0.047). The maxillule bilobate (Fig. 2E), outer lobe with three short naked apical setae, inner lobe with dorsal denticulate patch with three apical papillae each surmounted by a sturdy seta (length = 0.097-0.098). Maxillae forming cylindrical arms which are separate along their entire length except at the tip (Fig. 2F). They are slightly longer than the trunk body, tranversely wrinkled, tapering distally (length = 4.97-4.99). The bulla discoid (length = 0.314-0.318, width = 0.571-0.573, Fig. 2F). Maxillipeds (length = 0.328-0.331, width = 0.32-0.34) consisting of a broad corpus which tapers distally, and has denticulate cup on its distomedial border into which the opposing subchela fits (Fig. 2G, J). The myxal surface composed of a denticulate protuberance and more distal spiniform elements. The shaft of the subchela has one spiniform element approximately in the first-third of its length where shaft can opposes the denticulate cup on the corpus. There is a barb on the shaft just below the robust claw, which carries a small basal secondary denticle.
Figure 1. Neoalbionella sp. SEM micrograph of an adult female. A) Apical view, B) Maxilliped, C) Maxillule
Figura 1. Neoalbionella sp. Fotomicrografía en microscopio electrónico de barrido de una hembra adulta. A) Vista apical, B) Maxilípedo, C) Maxílula
Figure 2. Neoalbionella sp. adult female. A) Habitus dorsal. B) Habitus lateral. C) Antennule. D) Antenna. E) Maxillule. F) Maxillary arms and bulla. G) Maxilliped. H) Mandible. I) Caudal rami. J) Apex maxilliped shaft
Figura 2. Hembra adulta de Neoalbionella sp. A) Habitus dorsal. B) Habitus lateral. C) Anténula. D) Antena. E) Maxílula. F) Extremo de la maxila y bula.G) Maxilípedo. H) Mandíbula. I) Ramas caudales. J) Ápice del maxilípedo
In establishing the genus Albionella (now renamed Neoalbionella), existing species of Lernaeopoda were separated into two groups by Kabata (1979) solely on the basis of the morphological differences of the male. The differential generic diagnosis separating Lernaeopoda Blainville, 1822 from Albionella, now Neoalbionella was based solely on the morphology of the male (Kabata 1979). It would therefore be highly questionable to establish a new species of Neoalbionella based solely on the morphology of the female.
A female of Neoalbionella sp. described above is similar in structural features to some congeneric species in the following details (Table 1): (i) N. etmopteri and N. globosa both have the identical mandibular formula (Kabata 1979, Benz 1991b), (ii) N. oviformis have a similar apical armature of the antennule (Benz & Izawa 1990).
Females of this yet undetermined Neoalbionella species can be distinguished from all existing species in the genus by the following structural details (Table 1): N. fabricii is unique among Neoalbionella species in having an antennule of three segments instead of four, and two secondary teeth instead of three on the mandible. It can be easily distinguished from other members of the genus, except for N. oviformis and N. longicaudata by its long maxillae and caudal rami (Rubec & Hogans 1988). Neoalbionella kabatai has a shorter body length and a different apical armature of the antennule, the mandibular formula, the host species and geographical locality (Benz & Izawa 1990). Neoalbionella etmopteri is smaller and differs in the apical armature of the antennule (Benz 1991b). Neoalbionella oviformis is smaller and differs in the mandibular formula, in host species, Squalus mitsukurii, and in geographical locality, Japan (Benz 1991a). Neoalbionella globosa is the smallest species in the genus and also is different in the apical armature of the antennule, in host species, Scylliorhinus caniculus, and in geographical locality, British waters (Kabata 1979). Neoalbionella centroscyllii is also smaller and differs in the apical armature of the antennule and in mandibular formula, as well in host species, Centroscyllium fabricii and geographical locality, Canada (Kabata 1964).
Table 1. Mean body length (mm), features of segmentation and apical armature of the antennule, and mandibular formula of females in Neoalbionella species
Tabla 1. Longitud corporal promedio (mm), características de la segmentación y armadura apical de la anténula, y fórmula mandibular de las hembras de las especies descritas de Neoalbionella
The authors are grateful of the critical comments made by three anonymous referees that greatly improved the first version of the manuscript. We are deeply indebted with Claudio Carocca and Freddy Duarte for their help in collecting hosts and parasites. To Patricia B. Cepeda (Fish parasitology Research Group UFRRJ) for her help in the use of software for drawing. José L. Luque was supported by a Research fellowship from CNPq (Conselho Nacional de Pesquisa e Desenvolvimento Tecnológico, Brazil).
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Recibido el 28 de enero de 2010 y aceptado el 7 de mayo de 2010