Nota

 

A benthic mollusks checklist from laguna Cuyutlan, Colima, Mexico

 

Listado de moluscos bénticos de la laguna de Cuyutlán, Colima, México

 

Vania Serrano-Pinto and Javier Caraveo-Patiño

 

Centro de Investigaciones Biológicas del Noroeste Apartado Postal No. 128. La Paz, 23090 B.C.S. México.

 

Recibido: 30 de enero de 2002
Aceptado: 22 de octubre de 2002

 

Abstract

A malacological list of Laguna Cuyutlán in the state of Colima, Mexico and its surrounding area is provided. The list includes all species collected during the spring and fall of 1986. Inside the lagoon 54 species that belong to 38 genera, 26 families, and two classes were identified. In the sea surrounding the lagoon, 70 species were found that belong to 52 genera, 32 families, and 3 classes. The maximum number of species was found in the adjacent marine zone. In the surrounding sea, were found Gastropoda, Pelecypoda, and Scaphopoda classes. Inside the lagoon only Gastropoda and Pelecypoda classes were found.

Key words: Benthic mollusks, Laguna Cuyutlán Colima, Marine Ecology.

 

Resumen

En este trabajo se proporciona la lista malacológica de la Laguna de Cuyutlán, Colima, México y zona marina adyacente. La lista incluye las especies recolectadas durante las estaciones de primavera y otoño de 1986. En la laguna se identificaron 54 especies, pertenecientes a 2 Clases, 26 familias y 38 géneros. En el mar se encontraron 70 especies, pertenecientes a 3 Clases, 32 familias y 52 géneros. El mayor número de especies se presentó en la zona marina adyacente. En donde fueron encontradas las clases Gastropoda, Pelecypoda, y Scaphopoda. Dentro de la Laguna, solamente las clases Gastropoda y Pelecypoda, fueron halladas.

Palabras clave: Moluscos bénticos, laguna Cuyutlán, Colima, ecología marina.

 

It is well known that coastal lagoon contain considerable fishery resources (Hildebrand, 1946; Günther, 1969; Stuardo and Villarroel, 1976). For this reason, benthic resources, such as mollusks, are one of the most important groups to be surveyed prior to any proposal for a rational management inside lagoons (Yáñez-Arancibia and Nugent, 1975).

The sessile characteristics of the benthic communities and its resilience cause such communities to be good ecological indicators of potential modifications by external influences. Benthic organisms are usually selected for this kind of studies because of their abundance, diversity, and trophic importance (Cobo, 1978).

Taxonomic lists are an important perspective on the biodiversity composition of a specific area. Taxonomic lists show a primary element for environmental assessments, as well as the basis for studies addressing the requirement of establishing rules for the rational use of natural resources (Cruz-Agüero et al., 1994).

There are very few studies on Laguna Cuyutlán (Cobo, 1978; Treviño and González, 1984; Ascencio, 1985). There is no study dealing with the Cuyutlán benthic communities, and there is not any taxonomic list of mollusks. For this reason, the Universidad Nacional Autonóma of México developed an environmental impact assessment study in the Laguna Cuyutlán in 1986.

During this study, samples were taken from the benthic part of the lagoon and surrounding areas. The malacological list of the lagoon and marine environments are presented here.

Laguna Cuyutlán, situation is along the Pacific coast of the state of Colima Mexico, between 18°56' and 19°03' N and 104°00' and 104°19 W. The lagoon is part of a coastal lowland between Bahía Manzanillo and Río Armería. The lagoon area is 7,200 ha (Contreras, 1985; Fig. 1). Inside the lagoon, were established 8 sampling locations and 4 were established in the surrounding sea (Fig. 1). Sampling locations were selected where potential damages produced by proposed hydraulic activities in the lagoon. Two boats were used for sampling. Inside the lagoon, a 3-m flat-bottomed boat with a 7-hp motor was used. In the sea, a 7-m boat was used, with two 135-hp motors.

A "Van Veen" 1-1 dredge was used for sampling. From each sampling location, were obtained 3-I samples, because, as a point study this quantity is enough to determine the specific richness (Soto, pers. com.). Sampled material was placed in plastic bags. After each sample was sifted with a 0.5-mm sieve to separate the mollusks. Organisms were placed in glass jars filled with 10% formaldehyde. Each organism was identified and quantified in the laboratory with a stereoscopic microscope. For taxonomic identification specimens were compared with photographs and schemes contained in the following books: Morris (1966) Keen (1971), Keen and Coan (1974), Abbott (1974), Linder (1983), and Fisher et al. (1995). Shells were for the identification to the species level, when possible. The reference collection of this sampling has been deposited in the Instituto de Ingeniería, U.N.A.M.

For the inner part of the lagoon, were identified 54 species, belonging to 2 classes, 26 families, and 38 genera (Table 1). In the sea, were found 70 species that belong to 3 classes, 32 families, and 52 genera (Table 2). Acteocina smirna (Dall, 1919), A. angustior (Baker and Hanna, 1927), Assiminea californica (Tryon, 1865), Elephantulum insculptum (Carpenter, 1857), Alabina effusa (Carpenter, 1852). Mytella strigata (Hanley, 1843), Chione squamosa (Carpenter, 1857) and Tagelus longisinautus (Pilsbry and Lowe, 1932) were species founded inside and outside the lagoon.

Mexico is a country, with a high biodiversity richness in plant and animal species because of an overlap of the Nearctic and Neotropical biogeographic regions (Wilson, 1988; Reguero-Reza and García-Cubas, 1993). Mexico is one of the five nations with the greatest species richness (Navarro and Llorente, 1991; Reguero-Reza and García Cubas, 1993).

Results from the sampling project confirm such a great species richness in both marine and lagoon environments (Morris, 1966; Keen, 1971; Keen and Coan, 1974; Abbott, 1974; Lindner, 1993). However, neritic species are more abundant in the surrounding sea than inside the lagoon, not only in species, but also in classes Gastropoda, Pelecypoda, and Scaphopoda. Inside the lagoon, only were found Gastropoda and Pelecypoda classes. According to Morton (1971), the mollusks group can be defined as a phylum characterized with great diversity and adaptative plasticity (Reguero-Reza and García-Cubas, 1993).

Of the species found in the lagoon and the sea the only marine-euryhaline species is Tagelus longisinuatus. However, Stuardo and Villarroel (1976) report such species as endemic inhabitants of estuaries, inlets, and coastal lagoons. It is more appropriate to include such species in the estuarine component. Stuardo and Villarroel (1976) consider Mytella strigata exclusively as part of the estuarine component. However, M. strigata was found inside and outside the lagoon.

The results of this study will be a key element for future environmental impact assessments prepared for this region.

We appreciate the support provided by the Universidad Nacional Autónoma de México and M. en C. Luis Treviño-Acuña. To Dra. Celia Vázquez and the Centro de Investigaciones Biológicas del Noroeste, S. C. (CIBNOR for logistic support. Ira Fogel of CIBNOR edited the English-language text.

 

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