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RESUMEN Se presentan los resultados del estudio concerniente a la taxonomía, distribución, origen halino y tipos de nutrición de los moluscos en la laguna Mecoacán y se mencionan algunos aspectos hidrológicos de la región. Se describe la distribución local y geográfica, así como el habitat de 42 especies, 20 de ellas correspondientes a la Clase Gas...
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... a la población total de moluscos (Fig. 7), la afinidad resultante indica que de las 190 combinaciones posibles, dadas por el número total de estaciones, el 44.7% se ubica dentro del rango 50-74 con 85 combinaciones, el 42.1% corresponde al intervalo 25-49 con 80, quedando los rangos de 75-100 y 0-24 con porcentajes de 5.2% y 7.9%, con solo 10 y 15 combinaciones respectivamente. El valor medio de afinidad para todo el conjunto de estaciones es de ...
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Molluscs are a diverse phylum in coastal lagoons because the numerous taxa collectively display broad ranges of optima and tolerance with respect to ambient conditions. We report on the taxonomic composition, habitat preferences and feeding guilds of molluscs from Río Lagartos coastal lagoon, Mexico. Molluscs were collected in the rainy season (September/October 2017), during the winter ( Nortes ) season (February 2018) and at the end of the warm, dry season (May 2018). Samples were taken using a Ponar dredge, a cylindrical PVC core barrel, or a beach seine. We studied the abiotic characteristics (sediment grain-size distributions, submersed aquatic vegetation abundance and salinity) to explore assemblage differences across the broad salinity gradient that characterizes the system (~30–78 PSU). Molluscs were represented by 39 species, 34 genera, 23 families and two classes. Stenohaline species were more numerous overall than euryhaline species, but their occurrence in samples was low (<20% of the samples). Stenohaline taxa lived primarily in environments characterized by marine salinity, and few were found under hypersaline conditions. We collected a smaller number of species than did studies carried out in the lagoon >35 years ago. Species accumulation curves revealed that the full species richness was not captured in our study. Euhaline environments displayed greater mollusc species richness and had a larger proportion of amount (mass) of submersed aquatic vegetation. In the hypersaline environments, species richness may be favoured by the lower dominance of sands. Suspension feeders were the most diverse group in both the euhaline and hyperhaline environments.
Antecedentes:
La distribución y dieta de los peces, así como la composición específica de sus presas, ha sido afec tada por la intensificación de las variaciones espaciales de la salinidad debido a la infraestructura hidráulica y cambio climático. Cathorops aguadulce se seleccionó por los registros previos de su dieta y su actual dominancia en los sis temas estuarinos del sur del Golfo de México.
Objetivos:
La dieta fue evaluada en relación con las variaciones de su composición por tallas, día-noche y estacionales en la laguna Mecoacán.
Métodos:
Doscientos diez tractos digestivos se analizaron entre juveniles y adultos capturados en un muestreo que incluyó la variación diurna-nocturna y estacional en tres localidades ubicadas en un gradiente de salinidad. La composición por tallas se correlacionó (coeficiente de Spearman) con la variación espacial y temporal de la salinidad y la temperatura. La variación temporal y espacial de los índices de repleción (IR) y de importancia relativa (IIR) se analizó mediante la prueba Kruskal-Wallis y agrupamiento jerárquico.
Resultados:
La composición por tallas fue independiente a la variación de la salinidad y al índice de repleción (Kruskal-Wallis; p =0.649), pero la intensidad de la dieta en sequía fue significativamente mayor que en las temporadas de transición y lluvias (Kruskal-Wallis; p =0.00001). Entre los 11 ítems alimenticios definidos, el detrito animal y los malacostracos, principalmente tanaidáceos, fueron las categorías alimenticias dominantes por frecuencia de ocurrencia e IIR. Sin embargo, el detrito predominó en juveniles, mientras que los tanaidáceos fueron el ítem preponderante en los adultos.
Conclusiones:
Aunque la laguna Mecoacán registró una amplia variación de la salinidad y C. aguadulce presentó una variación temporal significativa en su intensidad de dieta, la deriva ontogénica fue más determinante que los efectos de la variación ambiental en sus hábitos alimenticios. Esta conclusión abre la posibilidad de comprobar si la variación ontogenética de sus rasgos morfométricos funcionales está asociada con la adquisición de alimento y movimiento.
Poster presentado en la RENAMAC, Guadalajara, México
The richness of aquatic snails was determined, on two basin of the state of Tabasco, samples were taken at 23 locations during two seasons, the rainy season (September and October 2008) and the dry season (April and May 2009). The organisms were collected from the roots of Rhizophora mangle (red mangrove) and those adhered to Eichhornia crassipes (water hyacinth). Thirteen gastropods and three bivalves associated with water hyacinth as well as four gastropods and four bivalves from mangrove roots were collected. The CH Grijalva River-Villahermosa present he highest species richness 21 and 20 species were within the Subc. Carrizal River 52.17% of the species were from freshwater and collected on water lily; 30.44% were collected were brackish and collected on mangrove roots; 17.39% on euryhaline and harvested on both vegetation types. As for the estimation of richness, a difference of one to five species was observed between then species richness estimated and that estimated with SChao2. Of the 23 species recorded in this study none are listed in the NOM-059-SEMARNAT-2010. The most abundant freshwater species on the two basins were Pyrgophorus coronatus, Mexinauta impluviata, Littoridinops tenuipes, Mayabina polita and Pomacea flagellata; and brackish Mytilopsis leucophaeata, Brachidontes exustus, Littorina angulifera, Neritina virginea and Musculium transversum. The greatest richness and abundance of molluscs associated with both E. crassipes as R. mangle were present during the rainy season.
Several studies have been conducted on the richness and abundance of molluscs in the coastal coral reefs of the Gulf of Mexico since 1960's, but these have focused mainly on knowledge of prosobranch gastropods and bivalves species, while only 6 species of opisthobranchs have been registered for this ecosystem. In this paper we present a list of 23 species of opisthobranchs from the Veracruz Reef System National Park, a complex of 23 coral formations located on the coast of Veracruz on the Gulf of Mexico. The list includes 9 new records, a systematic arrangement and pictures of several of the species mentioned here.
Algunos autores han planteado que los géneros Pyrgophorus Ancey 1888 y Potamopyrgus Stimpson 1865, son sinónimos, mientras que otros opinan que ambos se encuentran restringidos geográficamente. La similitud en la escultura de la concha, es lo que ha llevado a que sean considerados sinónimos, sin embargo las especies de Pyrgophorus son mucho más pequeñas, con cinco o menos vueltas y de sutura poco profunda. El objetivo de este trabajo es dar a conocer la distribución y taxonomía del gasterópodo de agua dulce Pyrgophorus platyrachis en el Sistema de Maracaibo, estado Zulia, Venezuela. Durante muestreos efectuados entre 2001 y 2009 se detectó la presencia de cientos de individuos de P. platyrachis en las localidades de la laguna de Gran Eneal, laguna Las Peonías, Punta Capitán Chico, San Francisco, Curarire, desembocadura del Río Apón, Ciudad Ojeda, Bachaquero y Tomoporo de Agua. Por lo tanto, se realizó un análisis taxonómico de los ejemplares obtenidos, destacando su distribución y la presencia de tres morfotipos: liso, enroscado y espinoso; el primero limitado a la Laguna de Gran Eneal, las Peonías, desembocadura del Río Apón y Punta Capitán Chico, mientras que los otros dos se encuentran juntos en las localidades restantes. Además, se propone la sinonimia entre P. platyrachis y otras especies descritas como Pyrgophorus parvulus y Pyrgophorus spinosus.
Dredging the inlet of Laguna Mecoacán, Tabasco, southern Gulf of Mexico in 2000, affected the distribution of aquatic fauna after modifying the volume of water, salinity gradient, and migration patterns between estuarine and marine organisms. Ten sites were bimonthly sampling during the day in February, April, June, August and October 2000. A total of 702 decapods belonging to nine families, 14 genera and 19 species were collected with an otter trawl. Dominant species in density (ind/m2) were Eurypanopeus depressus, Litopenaeus setiferus, Farfantepenaeus aztecus, F. duorarum and Clibanarius vittatus, whereas for biomass (g/m2) the penaeids, C. vittatus and the swimming crabs Callinectes rathbunae, C. similis and C. sapidus were dominant. The highest density (61%) was recorded in the rainy season, whereas the highest biomass (57%) was obtained in the dry season. The spatial variation in salinity is reflected as a gradient from the southeast to the north, defining three zones due to the marked fluctuation of the river discharge. The 81% of the species, 87% of the density, and 77% of the biomass of all decapods were collected in mesohaline and polyhaline conditions (zones II and III), and the minimum values in oligo-mesohaline conditions (zone I). The lower number of decapod species in Laguna Mecoacán, in comparison to other coastal lagoons in the southwestern Gulf of Mexico, is related to the restricted distribution of the submerged aquatic vegetation and the prevalent oligohaline and mesohaline conditions, while habitats as seagrass and macroalgae beds, and the mussel and oyster reefs have drastically decreased, and the unvegetated muddy substrates are predominant in this lagoon.
This paper reviews literature from the Americas and Europe on the dark falsemussel Mytilopsis leucophaeata (Conrad in J Acad Nat Sci Phila 6(2):256–268, 1831), including data collected in its native habitat in the Americas that appear as incidental information in published reports.
Mytilopsis leucophaeata is a poorly studied dreissenid bivalve that is native to mainly oligohaline–mesohaline regions of estuaries in North America.
In its native habitat, it usually occurs in very low numbers and has rarely been mentioned in field survey reports. However,
occasionally in its native habitat and often in habitats where it has been introduced (as in Europe and Brazil), it may undergo
population irruptions for no clear reason. This review describes habitat characteristics, environmental tolerances, and biological
and ecological attributes of the species. The assembled information reveals the species to be euryhaline and eurythermal,
with an unexplained ability to persist in its native estuaries even though it is relatively short-lived and usually uncommon.
KeywordsControl–Distribution–Ecology–Habitat–Physiology–Reproduction
