Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Background: The organisms respond to changes in the environment, hence the reproductive process of an organism can be affected as a result of contamination. Chione undatella is a potential resource for fishing and cultivation, which has been intensively exploited for many years on the Mexican Pacific coast. Goals: The main objective of this study was to characterize the reproductive cycle and spawning temporality, estimate the size at first maturity, and determine if there is tissue damage that may have adverse effects on reproduc­tion of C. undatella because of the contamination found in the mining port of Santa Rosalía, Gulf of California. Methods: Through histological analysis, the general condition index (GCI), and environmental parameters, we evaluated aspects of the reproductive biology and health of the frilled venus clam from the coastal area of the port of Santa Rosalía. Results: C. undatella has reproductive activity throughout the year, unrelated to the concentration of chlorophyll-a, or to temperature. An inverse correlation was found between the GCI and the phase of development with higher frequency in females. The size at first maturity is 57 mm LC. In the gonadal tissue (> 80% of the individuals) an infiltration of eosinophilic cells was observed in all phases of gonadal development with an intermediate to abundant intensity (> 60% of the organisms). Conclusions: Although C. undatella has reproductive activity throughout the year, the high prevalence of hemocytic infil­tration in the gonadal tissue suggests a potential deficiency in its reproduction. We recommend more studies be undertaken to confirm this preliminary finding and determine the relationship of the deficiency with the contamination present in the area.

Background. In any culturing of organisms, to calculate fecundity we need to know how many descendants are produced. Goals. Marsupial and post-marsupial fecundity was calculated for Metamysidopsis elongata (Holmes, 1900) in two culturing generations (F1 and F2), and wild caught from Mazatlán Bay. Methods. From September 2010 to October 2011, we carried out monthly sampling on foot with a plankton net with a mesh size of 1 000 ?m and a mouth opening of 50 cm in diameter. The fecundity evaluation was calculated with organisms fixed with formaldehyde at 4%. Culturing occurred at a density of 5 ind • L-1 at 22 ± 1 o C, salinity 32 ‰ with continuous aeration. The mysids were fed ad libitum with recently hatched Artemia nauplii. Results. The average marsupial fecundity was 6.28 ± 2.94 embryos per female in wild mysids, 4.51 ± 1.20 in the F1, and 3.72 ± 0.89 in the F2. The average post-marsupial fecundity was 5.86 ± 1.45 in wild mysids, 3.74 ± 1.20 in the F1, and 3.32 ± 1.42 in the F2. No correlation between the length of females and fecundity was found. Conclusions. The fecundity of the wild mysids was present throughout the sampling cycle and was lower than that of the cultivated ones.  

Background. Most studies on benthic diatoms found in northwestern Mexico have been done along the western coast of the Baja California peninsula. Thus, few studies exist for the Gulf of California. Goals. To gather new records of benthic diatoms found in the Gulf of California. Methods. Diatom samples from sediments and rocks of the coast of Santa Rosalía, Baja California Sur, were observed under a light microscope (LM). Results. Three taxa were recorded and depicted: Caloneis liber var. bicuneata (common), Gyrosigma naja (scarce), and the new combination Entomoneis pulchra var. pulchella (scarce). Conclusions. These three taxa were recorded for the first time in northwestern Mexico.  

Background: The tropics are centers of high biodiversity of Rotifera that are highly variable and abundant. They play a key role since they are a link in the interaction network with members of other communities. Temporal changes in the community structure of the Rotifera assemblage is related to hydrologic phases. Goals: In this study, we focus on testing the hypothesis that the seasonal changes in alpha diversity and abundance (standing stocks) of Rotifera (Monogononta), considering also limnological variables, are mainly related to rainfall patterns. We consider four seasons based on rainfall: rainy, very rainy, dry, and very dry. Methods: Between 2008 and 2009, rotifers were sampled monthly with a plankton net in qualitative and quantitative sampling, and seven limnological variables were recorded at three sampling stations along Lake Amapá. Results: We found approximately 23% of all Rotifera listed for the Amazonia. The high Menhinick index revealed a high species dominance, except in the rainy season. The Shannon index did not show a greater distribution of organisms (0.3844 to 0.8886) independent of the layer and time season. In general, the equability index showed that all species were equally abundant in all seasons, with higher values at the surface and in the middle of the water column. The limnological variables also showed differences between all seasons in at least a layer of the water column. Conclusions: The seasons influenced the fluctuations in the communities of Rotifera of Lake Amapá, which led to a different species distribution pattern over time.

Background: Knowledge of growth is relevant because it provides information on the local dynamics of the population. Goals: This study evaluated the growth, size structure, morphometry, and sex ratio of C. belliosus crab caught in the El Colorado lagoon, Ahome, Sinaloa, Mexico. Methods: Through size distributions and by the modal-progression method using the FISAT II program. Similarly, the growth parameters of the von Bertalanffy stationalized equation and the growth performance or Munro index (Ø) were determined from March 2012 to March 2013. Results: 3,242 organisms of C. bellicosus were captured of which 1,770 were males and 1,472 were females. The population of C. bellicosus in the lagoon ranged in size from 40 mm to 190 mm (CW), showing two similar modes for males and females (100 mm and 110 mm, respecti­vely). The relationships between CL-CW for both sexes were adjusted to a linear type model (males, CL = 0.5265CW-0.0539, R2 = 0.8058, p <0.05, females, CL = 0.581CW-0.6335, R2 = 0.7643, p <0.05). The CW-TW relationship was of potential type (males, TW = 0.561AC3.0751, R2 = 0.7968, p <0.05; females, TW = 0.0834C2.9077, R2 = 0.7589, p <0.05). In females, K = 0.90 years-1 and L∞ = 169 mm, K = 1.20 years-1 and L∞ = 178.5 mm. Conclusions: The growth curves suggest that C. bellicosus reaches its maximum length at 2.5 to 3 years. The sex ratio of 0.81 F : 1 M was significant (X2 (0.05, 11) = 19.675, X2 observada = 58.481, p < 0.05).  

Background. Climate variability and climate change are related to changes in the climate regime, with effects on the hydrological cycle. The intense rains in short periods in the basin of Metztitlán River cause the river to quickly fill its discharge vessel (Lake Metztitlán) and flood Irrigation District 08 and nearby towns. Goals. This study undertook a long-term hydrological analysis of the Metztitlán watershed to identify signs of climate change by looking at statistical means, and it defined the limits of greatest flood risk in order to understand the affected locations. We also calculated the environmental flow and the probable discharge volumes of the Metztitlán River. Methods. The historical tendency of the runoffs from 1937 to 2008 was estimated using the Regime Shift Detection software; the environmental flow and the probable discharge volumes were evaluated based on the Tennant method. Results. The analysis showed the mean annual runoff regime: Maximum extreme rainfall occurred in 1944, 1955, 1998, and 1999; and minimum rainfall occurred in 1950 and 1997. In the mean monthly runoff regime, seven and five changes were observed in the ten and five-year longitude cuts, respectively. These imply a downward trend of runoffs in the dry period, and an upward trend in the rainy period in recent years. Conclusions. We were unable to detect any signs that might have allowed us to link these changes with climate change, although we did find a certain relationship with the El Niño-Southern Oscillation phenomenon. The highest flood risk limits lie between 1246 and 1258 meters above sea level; the susceptible populations are El Pedregal de Zaragoza, San Cristóbal, Tlacotepec, Tlatepexe, and Tecruz de Cozapa. The estimations of environmental flows indicate higher reserves for September and October and the release of excessive volumes throughout the year.  

Background. In the marine environment of San Cruz Island, no published references exist regarding the ecology of soft-bottom mollusks. Thus, it is important to carry out research that broadens and deepens the knowledge of this marine area and contributes to proposals of management methods and alternatives for the sustainable use of insular marine resources. Goals. This study seeks to characterize the community composition and structure of soft-bottom mollusks of the infralitoral zone of Santa Cruz Island, and describe some of the characteristics associated with their habitat. Methods. During August 2010, 32 samples were collected: 16 were biological samples and 16 were sediment samples. The composition, abundance, and diversity of the malacological community were analyzed using ecological indexes. Results. 695 individuals were recorded and grouped in two classes: Gastropoda with 446 organisms (5 orders, 11 families, and 19 species); the most abundant species was Siphonaria maura (18%); the class Bivalvia included 249 organisms (8 orders, 14 families, and 25 species); the most abundant species was Tellina eburnea (10%). The Gastropoda class were more abundant than the Bivalvia, i.e., 64.17% and 35% respectively. The species with major abundances and relative frequencies were the gastropods Siphonaria maura (18%) and the bivalve Septifer seteki (69%). Four trophic categories were identified: filterers (73%), herbivores (20%), carnivores (5%), and ectoparasites, the latter of which were the rarest group (2 %). Conclusions. At this site, the specific richness (44 taxa) was lower compared to other sites from different latitudes of the western Gulf of California, likely derived from the higher energy environment of the study area that allowed only juvenile mollusks and micromollusks to be collected.