New Records for GASTROPODA Class of Species Found in the Rocky Intertidal Zone of the Marine Priority Region 32 , Guerrero , Mexico

The GASTROPODA class, one of the best known marine environments, is formed by a large number of species and the shape of their shell structure varies greatly. These mollusks are distributed from the intertidal zone all the way to the abyssal zone, and there are also swimming and floating species. This research was conducted at seven sites, located in the Marina Priority Region 32 (MPR 32), located in the State of Guerrero, Mexico. The aim of this report is to document the scope of the geographic distribution of the 34 species of GASTROPODA class. 11,263 total specimens were analyzed. 108 species were identified, of which four species are new records for Mexico, 15 for the Transitional Mexican Pacific, 11 for the State of Guerrero and four for the MPR 32. Here we report a significant number of new records of species of class GASTROPODA found on the rocky intertidal zone of the MPR 32. The reporting of these new records, demonstrates the need to focus research efforts on the study of marine diversity, since knowledge in this respect is quite incomplete, especially regarding marine mollusks, a fact that has been reported by the National Commission for the Management and Use of Biodiversity.


Introduction
Mexico has seven of the 24 marine ecoregions into which North America is divided.Region 17, also called the Mexican Pacific Transitional includes the coastal waters of the states of Jalisco, Colima, Michoacán, Guerrero and Oaxaca and the southern tip of Baja California Sur.The physiography of this region is characterized by a narrow continental shelf with an amplitude of 10 -15 km and a slope of less than 1˚30', with a deep ocean trench and complex abyssal plains [1].
For the State of Guerrero the National Commission for the Knowledge and Use of Biodiversity (Comision Nacional Para el Uso y Conocimiento de la Biodiversidad; CONABIO) stated that there are four marine priority areas for the conservation of coastal and ocean biodiversity; about these regions CONABIO has highlighted the lack of knowledge about the diversity of marine species.
The Marine Priority Region No. 32 (MPR 32) is located in the state of Guerrero and is known by the name Coyuca-Tres Palos, has an area of 829 km 2 .This region is identified as an area of high biodiversity and that presents problems as reported by CONABIO due to the modification of the environment by discharges of fresh water, chemicals and fertilizers, live stock waste, damage to the environment by tourism, the use of its resources such as endangered bird species, the introduction of exotic species such as tilapia and coconut palm, and the lack of current regulations for the use of natural resources [2].
As part of the marine fauna that make up the MPR 32 are mollusks, and within this taxon is the GASTRO-PODA class, which are known as the best of the marine environment, being numerous and varied as to the form of their shells These organisms have a muscular foot retractor having the function of moving the head and foot of the mollusk in the shell.They are distributed from the intertidal zone to the deep or abyssal zone, but there are also swimming and floating species [3].
For organisms that belong to the class GASTROPODA, there are reports concerning global taxonomic and geographical aspects [4] [5].There are also reports of this type exclusive to the American Pacific as [6]- [8].
In the Mexican Pacific research has been conducted involving taxonomic aspects, composition and structure of communities; others include diversity, abundances, zonation, variation over time and geographical distribution of species, such as [9]- [24].
In particular for the coasts of Guerrero where there are reports of the class GASTROPODA analyzed as part of the set of classes studied, among which are those of [25]- [37], however, the class GASTROPODA in the coast of Guerrero, there are still many outstanding issues, regarding the knowledge of biodiversity.It is important to have an inventory of species, to study communities and composition, and to manage and maintain biodiversity of highly diverse regions such as the state of Guerrero in rational and responsible manner.
The aim of this contribution is to report the scope of geographical distribution for 34 species of the class GASTROPODA found in MPR 32.

Study Area
The coast of Guerrero is located in the 17th Marine Ecoregion of North America.As part of the coast of Guerrero is the MPR 32, (Coyuca-Tres Palos area) is located at latitude 16˚35'24'' to 17˚28'12'' and longitude 99˚25'12'' to 100˚33' (Figure 1).
The climate is warm sub-humid, has an average annual temperature over 26˚C, tropical storms and hurricanes occur from May to November.It belongs to the North American plate, is constituted by metamorphic rocks and a narrow platform.It is bathed by Costa Rica Coastal and North Equatorial Currents, receives fresh-water input from rivers, some areas are hit by harsh high surf waves, el Niño, red tide and other processes of turbulence occurs.It is an area with a rich and abundant biodiversity: mollusks, polychaetes, echinoderms, crustaceans, turtles, fish, birds, marine mammals, endemic fish and mangrove, and is an important bird feeding area.There are also regulatory issues; ignorance of current regulations for the use of resources and illegal fishing is frequent.This region is particularly important because it represents an area for several zoological groups with respect to conservation, especially birds and their diversified habitat, and the potential impact by tourism and the lack of information on this issue [2].
Sampling was conducted from 2009 to 2012 at seven sites: Parque de la Reina, Tlacopanocha, Majahua, Muelle, Manzanillo, La Angosta and Pie de la Cuesta.Geographical coordinates were registered for each site and described according to the following criteria: approximate length of the sampling area, the substrate structure and stability, rock type, and wave exposure of the substrate.Descriptions of the collection sites were based on [38], geological maps of the National Institute of Statistics, Geography and Informatics "Instituto Nacional de Estadística, Geografía e Informática" INEGI (Acapulco maps E14-11, 1:50,000), and complemented with field observations (Table 1).
The sites may change with the type of substrate, its stability and exposure to wave impact; and were classified as substrate Type: 1) Rock masses: fixed structures such as walls, cliffs, terraces, and alike.2) Large boulders: unattached rocks larger than 50 cm, immovable or difficult to move by the waves impact.3) Rolled boulders: loose rock smaller than 50 cm and greater than 8 cm. that can easily be moved by the impact of the waves.4) Gravel: loose rocks o pebbles no larger than 8 cm.The substrate stability was classified as: 1) High: when the substrate remains practically unchanged by the impact of waves, 2) Middle: when the configuration of the substrate is basically not changed by the waves impact but there is some rock displacement, 3) Low: when the site configuration is changed by the impact of waves, most of the rocks are moved.Wave exposure was classified as: 1) High: when waves hits the unprotected substrate directly, 2) Middle: when the wave impact on the substrate is softened or hampered by barriers and 3) Low: when the wave does not hit directly, since the sites are protected by different types of barriers [39].

Collection of Samples
Three samples were conducted per site between 2009.Sampling was performed during the hours of low tide on new moon days.Sampling was carried out using quadrants and travels in search of organisms that were not found in the quadrants.The quadrants were used for the purpose of carefully reviewing an area and to keep smaller organisms from being excluded from the sample and this was carried out in the following way.The starting point was randomly selected, then a nylon rope 30 m long was placed parallel to the shore on the intertidal zone using a PVC pipe square frame 1 m per side to delimit the sampling unit.Once the starting point was established, the PVC frame was placed at the selected point.All GASTROPODA specimens found alive, even those attached under rocks within the sampling unit, were collected and placed into a plastic container filled with seawater and protected from direct sunlight.After completing the collection, a 2-m section along the rope was measured then the frame was again placed to define the following sampling unit.This procedure was repeated ten times along the length of the nylon rope.
Upon completion of the sampling there was a preservation of the specimens where there was doubt about its identification.The specimens were placed in jars with 96% ethyl alcohol and were transferred to the laboratory.

Laboratory Work and Data Analysis
The collected specimens were identified and quantified, using literature [5] and the nomenclature was updated according to [8].Literature and specialized websites [40]- [42] were consulted to determine if the organisms identified in the field and returned alive to their habitat and collected were recorded in the Pacific Coast of Mexico and particularly in the MPR 32.
The collected specimens were measured in length and width and the values of descriptive statistics such as maximum, minimum, average and standard deviation were obtained, these values are expressed in millimeters and were obtained using a digital caliper.
Subsequently, the specimens were deposited in the National Collection of Molluscs at the National Institute of Biology, Universidad Nacional Autónoma de México and the Molluscs Colletion of the Academic Unit of Marine Ecology of the Universidad Autónoma de Guerrero  are new records for the Transitional Mexican Pacific (Table 3 and Figure 3), 11 are new records for the state of Guerrero (Table 4 and Figure 4) and seven are new records for the Marine Priority Region 32 (Table 5 and Figure 5).

Conclusions
CONABIO reports that molluscs are a group about which little is known and further research is required in all of Mexico [2].This contribution reports a significant number of new records for species of class GASTROPODA found on the rocky intertidal zone of the MPR 32, of which several of these records are for Mexico, others for Transitional Mexican Pacific, the state of Guerrero and the MPR 32.With these new records report, we demon- strate the need to focus research efforts on the study of marine diversity.This has been noted by CONABIO, especially in regions that have been identified as priorities for conservation and use of biodiversity in Mexico.This report increases the biodiversity information for malacological fauna on the local and regional scales and establishes a basis for future investigations of marine molluscs.

Figure 1 .
Figure 1.Marine Priority Regions in the state of Guerrero, Mexico and sampling sites.Source: National Commission for the Knowledge and Use of Biodiversity (CONABIO) Authors: C. Torreblanca-Ramírez, R. Flores-Garza and L. Galiana-Rebolledo.

Table 1 .
Sampling sites considered in the study, indicating the location and relevant characteristics of the habitat.

Table 2 .
New records for Mexico, examined material, sizes and distributions prior to this contribution.

Table 3 .
New records for Transitional Mexican Pacific, examined material, sizes and distributions prior to this contribution.

Table 4 .
New records for the State of Guerrero, México, examined material, sizes and distributions prior to this contribution.