Gayana 72(2): 268-270,2008 Comunicación breve

COMUNICACION BREVE

CHROMOSOMES OF THE LIMPET FISSURELLA LIMBATA (SOWERBY, 1835) FROMNORTHERN CHILE (ARCHAEOGASTROPODA: FISSURELLIDAE)

CROMOSOMAS DE LA LAPA FISSURELLA LIMBATA (SOWERBY, 1835) DEL NORTE DE CHILE (ARCHAEOGASTROPODA: FISSURELLIDAE)

JoséPinochet-Roco¹, IrmaNorthland-Leppe¹, |Juana Capetillo-Arcos¹ & Pedro Jara-Seguel²

¹Departamento Biomédico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Casilla 170, Antofagasta-Chile. jmpinochet@uantof.cl
²Escuela de Ciencias Ambientales, Facultad de Recursos Naturales, Universidad Católica de Temuco, Casilla 15-D, Temuco-Chile.

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RESUMEN

Fissurella limbata (Sowerby, 1835), presenta un número cromosómico diploide 2n = 32 similar al descrito previamente para otras especies del género Fissurella Reeve 1849. El juego cromosómico haploide deF limbata tiene siete cromosomas metacéntricos, seis submetacéntricos y tres subtelocéntricos. Los cromosomas son pequeños y no exceden de 4,0 mm en longitud.

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Fissurella Reeve 1849 is a polytypic genus represented in Chile by 13 limpet species that inhabit in the sea coast from 18° to 56°S. Within the wide distribution range of the genus, nine species inhabit along the coastal area from Perú to Chile (Peruvian Province), whereas four species are localized in the coast of the southern region of Chile and Argentina (Magellanic Province) (Mcleanl984).

The identification of the species belonging to Fissurella has been classically based in morphological characters such as body-size, shell porous, epipodial tentacles, and pigmentation patterns of the shell, foot, mantle and head. Thus, various catalogue and guides for species identification have been documented for Chilean taxa of the genus (Oliva & Castilla 1992, Sasaki 1998, Osorio 2002). In contrast, genome studies in the genus Fisurrella are scarce. Recently, Olivares-Paz et al. (2006) have documented a first molecular study that included PCR-RFLP analysis of the mitochondrial cytochrome-b gene for authentication of 12 Chilean species of commercial importance. Additionally, Amar et al. (2003) have described preliminary chromosome characters for three Fissurella species, and Jara-Seguel (2007) has compiled chromosome numbers for five species all with a diploid number 2n = 32. F. limbata (Sowerby 1835) is a species belonging to the Peruvian Province (Guzman et al. 1998), and inhabits in the coastal area of Antofagasta in northern Chile. In this work, the somatic chromosome complement of F. limbata is shown for the first time.

To carry out the chromosome study, specimens of F. limbata were collected in the Constitución Beach, Mejillones Province (23°26'S; 70°35'W), northern Chile. The species was identified according to Oliva & Castilla (1992). In the laboratory, the specimens were submerged in colchicine 0.02% diluted in sea water (w/v) for 4 hours at room temperature and constant aeration.

Later, the gills were excised for dissection, hypotonised in 70% sea water solution (70% sea water and 30% distilled water) for 50 min and fixed in ethanol-glacial acetic acid (3:1 v/v) at 4°C until required. The metaphases were obtained by squashing of gill-cells using a phase contrast microscope OLYMPUS CH30. The chromosomes were stained using 4% Giemsa in phosphate buffer at pH 6.8. The metaphases were photographed withavideo camera SONNY CCD-IRIS connected to the microscope. Chromosomes were measured in photographic enlargements and standarized as a percentage of the total haploid set length. Chromosome shape was classified according Levan etal. (1964). The kary ogram was constructed with chromosomes organized on the basis of shape and size-decreasing order.

F. limbata has a diploid chromosome number 2n = 32 (Fig. 1). The formulaforthe haploid chromosome set of F. limbata was 7m + 6sm + 3st. Secondary constrictions and satellites were not observed on the chromosomes. The complement was moderately symmetric with most of 80% of the chromosomes within the metacentric and/or submetacentric categories, tendency previously described in almost.

14 species of Archaeogastropoda included within the families Haliotidae, Trochidae and Phasianellidae (Thiriot-Quiévreux 2003). The chromosomes ofF. limbata are small and the pair 1 do not exceed 4.0 urn in length. At present, species relationships using cytogenetic data are scarce for Fissurella, and only morphological and molecular characters have been used to its biosystematics study (McLean 1984, Oliva & Castilla 1992, Sasaki 1998, Olivares-Paz et al. 2006). In this work, F. limbata showed similitude in chromosome number respect to F. cumingi (Reeve 1849), F. maxima (Sowerby 1835) and-F latimarginata (Sowerby 1835) (Amare/al. 2003), being the haploid number n = 16 a conservative genome character among the species so far examined within the genus. In the future, additional chromosome studies in Chilean Fissurella species are necessary to be done, which may complement the zoogeographical, morphological and molecular antecedents so far documented for the genus (McLean 1984, Oliva & Castilla 1992, Guzman et al. 1998, Sasaki 1998, Olivares-Paz etal. 2006).

Figure 1. Karyogram of F. limbata 2n = 32. Bar =10 mm

Figura 1. Cariograma de F. limbata 2n = 32. Barra =10 mm

ACKNOWLEDGEMENTS

We are grateful to Unidad de Genética, Departamento Biomédico and Instituto de Investigaciones Oceanológicas, Facultad de Recursos del Mar, Universidad de Antofagasta, Chile. Thanks are due to Santiago Peredo for reading the English version of the manuscript.

BIBLIOGRAPHY

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Guzman, S. Saa & L. Ortlieb. 1998. Catálogo descriptivo de los moluscos litorales (Gastropoda y Pelecypoda) de la zona de Antofagasta, 23°S (Chile). Estudios Oceanológicos 17: 17- 86.        [ Links ]

Jara-Seguel, P. 2007. Avances en estudios cromosómicos de moluscos acuáticos chilenos. Boletín del Museo Nacional de Historia Natural, Chile 56: 53-61.        [ Links ]

Levan, A. K. Fredga & A. Sandberg. 1964. Nomenclature for centromeric position on chromosomes. Hereditas 52: 201-220.        [ Links ]

MClean, J. 1984. Systematics of Fissurella in the Peruvian and Magallanic faunal provinces (Gastropoda: Prosobranchia). Contributions in Science, Natural History Museum of Los Angeles Country 354: 1-70.        [ Links ]

Oliva, D. & J. Castilla. 1992. Guía para el reconocimiento y morfometría de diez especies del género Fissure lia Bruguiere, 1789 (Mollusca: Gastropoda) comunes en la pesquería y conchales indígenas de Chile Central y Sur. Gayana Zoología, 56(3-4): 77-108.        [ Links ]

Olivares-Paz,A., J. Quinteiro & M. Rey-Mendez. 2006. Autentificación de lapas del género Fissurella (Mollusca: Vetigastropoda) en la costa chilenas, mediante PCR-RFLP Investigaciones Marinas 34(1): 113-118.        [ Links ]

Osorio, C. 2002. Moluscos marinos en Chile. Especies de importancia económica. Guía para su identificación. Facultad de Ciencias, Universidad de Chile, Santiago, 21 pp.        [ Links ]

Sasaki, T. 1998. Comparative anatomy and phylogeny of the recent Archaeogastropoda (Mollusca: Gastropoda) of the University Museum. The University of Tokyo Bulletin 355(8): 329-355.        [ Links ]

Thiriot-Quievreux, C. 2003. Advances in chromosomal studies of gastropod mollusks. Journal of Molluscan Studies 69: 187-201.        [ Links ]

Recibido: 13.08.08

Aceptado :08.10.08