CYTOGENETIC STUDY OF Centropristes ocyurus Jordan and Evermann (PISCES: SERRANIDE)

Trabajo recibido el 8 de enero de 1990 y aceptado para su publicación el 6 de marzo de 1990.

RESUMEN

INTRODUCCIÓN

Due to the Serranidae family is located phylogenicaly in the base of the Suborder Percoidei, cytogenetic studys are particularly important. This suborder along with other 15 suborders from the Perciforms Order, which is one of the richer and more varied, in number of suborders and families, of the 31 orders that compound the Osteichthyes Class (Nelson, 1984). Moreover, this family presents a very interesting taxonomical problem (Kendall, 1979), because all the fishes that can not be included in any other family due to their morphological characteristics, have been located in it. Also, it is the receptor of all the lower percoidei which are not accepted in other taxa (Gosline, 1966). In accordance with the Mexican Marine Fishes Catalog (Ramírez-Hernández and González-Pages, 1976), published by the National Institute of Fisheries, of the Fisheries Secretariat of Mexico, this family is represented in the Mexican waters by 14 genera, meanwhile Castro - Aguirre (1978) considers that there are only 7 genera; being common for both cases only 5 genera.

According lo Miller (1959)Centropristes ocyurus is located from Cape Hatteras in North Carolina, U. S. A., to Yucatan, Mexico, with a limited distribution. The populations of this species forms part of the bentonic ictiofauna of the Mexican Caribe; they are an exploted local consumption resource, taking in account its quality as fresh seafood (Yáñez et al., 1985).

The studied species in this work belongs to the Centropristes genus, which is formed by 4 species: C. striatus, C. philadelphicus, C. ocyurus andC. melanus (Miller, 1959). Among these species there is a high number of "synonymias". For instance, the C. Striatuspopulations receive diverse names depending on the geographic location. TheC. ocyurus presents 3 "synonymias" and was considered a deep water variety of C. striatus. According with the above, it is of particular importance the cytogenetic study ofCentropristes ocyurus organisms caught in the Mexican Caribbean Sea, in order to know the characteristics of its chromosomic complements and to compare them with those of other taxonomic entities closely related.

The studied organisms were collected and processed on board of the B/O "Justo Sierra" vessel, during the oceanographic campaigns "Prospección Caribe Mexicano PROIBE III" and "V", which took part in April of 1985 and February of 1986, respectively. The specimens were caught in the area located between the 21°45'-22°20' North latitude and the 86°45'-87°10' West longitude, at variable deeps between the 44 and 60 meters, which determine the sample area located in the Yucatan Channel (Fig. 1).

Ten organisms, male and female, were treated by the techniques of McPhail and Jones (1966), Denton (1973) and Kligerman and Bloom (1977).

Sixty metaphases were analyzed, and 11 mitotic fields (9 from male and 2 from female), showed a complete chromosomic complement. In order to stablish the karyotype, mitosis with a high definition of the chromosomes and adequated concentration of chromatine (not very high) were chosen. Those fields with overlapping chromosomes were omited (Fig. 2).

The chromosomes were classified by the methods propoused by Levan et al (1964) and Al-Aish (1969).

According with the statistical analysis of the chromosomic complements, Centropristes ocyurus presents a karyotype formed by 48 chromosomes from which 14 pairs are metacentric and 10 pairs submetacentric (Table 1, Fig. 3 and Fig. 4) and the major chromosome arm number is n. f. = 96 because the 48 chromosomes are biarmed. Chromosomic heteromorphism or negative heteropygnosis which make evident the presence of sexual chromosomes was not found

Some authors (Ohnoet al., 1968; Denton, 1973; Thompson, 1979; and Uyenoet al., 1983) consider that the karyotype of the ancestral teleost fishes was of 48 achrocentric chromosomes, taking in to account that the karyotypes with biarmed elements (metacentric or submetacentric) are more evolved, because they come from the monoarmed chromosomes (acrocentric: telocentric). From the cytotaxonomic point of view the studied species shows a considerable evolved karyotype among the serranidae fishes, since all the chromosomes are biarmed and the n. f. = 96. This point of view is in accordance with Smith and Young (1966), because they consider that theCentropristes genus has his own morphologic characteristics and an accentuated sexual dimorphism, being a protogenic hermaphrodite

Figure 1. Collecting area of Centropristes ocyurus.

Figure 2. Mitotic fields of Centropristes ocyurus.

Figure 3. Karyotype of Centropristes ocyurus.

TABLE 1 RESULT OF THE STATISTICAL ANALYSIS OF THE KARYOTYPE'S CHROMOSOMES OF Centropristes ocyurus

Figure 4. Idiogram of Centropristes ocyurus.

Centropristes ocyurus shows a diploid number of 48 chromosomes from which 14 pairs are metacentric and 10 pairs are submetacentric. Due to the 48 chromosomes are biarmed the karyotype presents a fundamental number of 96. No evidence of sexual chromosomes exists in the species. For such reasons it is a very evolved species from the cytotaxonomic point of view.

The authors are grateful to Enrique Lozano-Alvarez and to Felipe Flores-Andolais from the Estación de Investigaciones Marinas Puerto Morelos of the Instituto de Ciencias del Mar y Limnología of the Universidad Nacional Autónoma de México (UNAM) for the help given in the participation in the oceanographic campaigns "Prospección Caribe Mexicano PROIBE". Likewise, we thank to Patricia Fuentes-Mata and Héctor Espinosa-Pérez from the Instituto de Biología of UNAM for the classification of the Biological Material.

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