ABSTRACT
Sponges have an important ecological role in coral reef ecosystems. However, when compared to other benthic Phyla, it has been little researched. This research was focused in the variability of the community structure of sponges in three locations at Morrocoy National Park (Cayo Sombrero, Playa Mero and Punta Brava) exposed to different environmental conditions (transparency and currents intensity) and affected in different degree of severity by a mass mortality event in 1996. A total of 15 transects (10m long and 1m wide) were evaluated in three strata (between 3 and 15m depth) in each site, where all the individuals were counted by species. Relative abundance by species, diversity and evenness were calculated. Locations showed differences respect turbidity, wave and current intensity. 27 species were found in Morrocoy; Cayo Sombrero (23), Playa Mero (18) and Punta Brava (15). Agelas sceptrum, Amphimedon erina and Niphates erecta were the most common in first location; Niphates erecta and Dysidea etheria in Playa Mero and Dysidea etheria, Niphates erecta and Amphimedon erina in Punta Brava. The species composition showed statistical differences between all three locations; Cayo Sombrero resulted the most diverse and even, followed by Playa Mero and Punta Brava. According to Sorensen Similarity Index results, Cayo Sombrero and Playa Mero were more similar, while Punta Brava resulted the most different. The variability in environmental conditions and the differential mass mortality effects of 1996 in all three reefs, were probably the main causes of the differences between their sponge communities. Nevertheless, we cannot conclude about the weight of these factors.
El presente estudio pone en evidencia la variación en la estructura de la comunidad de esponjas en tres localidades del Parque Nacional Morrocoy (Cayo Sombrero, Playa Mero y Punta Brava) con distintas condiciones ambientales y afectadas diferencialmente por una mortalidad masiva ocurrida en 1996. En un total de 15 transectos de 10m de largo y 1m de ancho en cuatro estratos comprendidos entre 3 y 15m de profundidad en cada localidad; se contabilizaron los individuos por especie para calcular la abundancia relativa, diversidad y equidad. Se analizaron las variables ambientales por localidad y se aprecian diferencias entre ellas con respecto a la corriente, turbidez, y exposición al oleaje. Fueron totalizadas 27 especies; Cayo Sombrero (23), Playa Mero (18) y Punta Brava (15), en la primera localidad domina: Agelas sceptrum, Amphimedon erina y Niphates erecta, en Playa Mero: Niphates erecta y Dysidea etherea y en Punta Brava: Dysidea etherea, Niphates erecta y Amphimedon erina. La composición de especies mostró diferencias estadísticamente significativas entre localidades. La mayor diversidad y equidad correspondió a Cayo Sombrero; donde las condiciones fueron más favorables para el crecimiento de estos organismos, seguido de Playa Mero y Punta Brava, guardando las dos primeras mayor similitud entre sí, según Índice de Sorensen.
Subject(s)
Animals , Coral Reefs , Environment , Porifera/classification , Conservation of Natural Resources , Environmental Monitoring , Population Density , Seawater , VenezuelaABSTRACT
Temporary abundance variation of Coralliophila abbreviata and Coralliophila caribaea (Mollusca, Coralliophilidae) in a coral reef at Morrocoy National Park. The mollusks Coralliophila abbreviata and C. caribaea are coral predators in the Caribbean Sea . We evaluated the temporal variability of abundance and size structure of C. abbreviata and C. caribaea in Cayo Sombrero, Morrocoy National Park, Venezuelar (September 2004 - August 2005). The density of C. abbreviata and C. caribaea was evaluated monthly by means of two 50- meter long transects paralell to the coast line, at 3 m and 6 m deep; aditionally, 30 individuals of C. abbreviata were collected to measure size. The densities of C. abbreviata at the shallow transect fluctuated between 1.78 ind/m² in September and 6.26 ind/m² in May. The densities at the deep transect fluctuated between 4.23 ind/m² in January and 7.66 ind/m² in May. The densities of C. caribaea at the shallow transect fluctuated between 0 ind/m2 (except in September) and 0.03 ind/m² (September) and the densities at the deep transect fluctuated between 0 ind/m² (October to March and July) and 0.1 ind/m² (April). Most individuals of C. abbreviata and C. caribaea measured between 12 and 16 mm and between 10 and 15 mm long respectively. Rev. Biol. Trop. 56 (2): 501-511. Epub 2008 June 30.
C. abbreviata y C. caribaea son moluscos coralívoros del Mar Caribe. Evaluamos la variabilidad temporal de la abundancia y los cambios en la estructura de talla de C. abbreviata y C. caribaea en Cayo Sombrero, Venezuela (septiembre 2004-agosto 2005). Se colocaron transectas fijas de 50 metros de longitud a profundidades de tres y seis metros cada una, paralelas a la costa. Se evaluó mensualmente durante un año la densidad de ambos depredadores y se seleccionaron 30 individuos de C. abbreviata para medirlos cada mes. Las densidades de C. abbreviata en la transecta somera fluctuaron entre 1.78 ind/m² en septiembre y 6.26 ind/m² en mayo; las densidades de C. abbreviata en la transecta profunda estuvieron comprendidas entre 4.23 ind/m² en enero y 7.66 ind/m² en mayo. Las densidades de C. caribaea fluctuaron en la transecta somera entre 0 ind/m² (todos los meses menos septiembre) y 0.03 ind/m² (septiembre) mientras que la transecta profunda fluctuó entre 0 ind/m² (octubre a marzo y julio) y 0.1 ind/m² (abril). La mayoría de los individuos de C. abbreviata midieron entre 12 y 16 mm de longitud. El largo de la mayoría de los individuos de C. caribaea estuvo comprendido entre 10 y 15 mm.
Subject(s)
Animals , Mollusca/classification , Mollusca/anatomy & histology , Population Density , Population Dynamics , Seasons , Seawater , VenezuelaABSTRACT
Unare Lagoon is one of the most important fishery coastal ecosystems in Venezuela. For the past 10 years, changes in its hydrological regime have affected the physiochemical characteristics of the water with important consequences on its faunal composition and abundance. An example of such variation is the abundant presence ofa fish species, Gobioides broussonnetii, recently registered in this ecosystem. The ecology of this species must be studied to identify new ecological processes occurring in the lagoon. Detritus is the most important component of the G. broussonnetii diet, followed by plant and animal items. The species is a primary detritivorous consumer and this may be associated with its activity pattern (morning): It may be an occasional visitor because it was not captured regularly in the monthly samplings.
La Laguna de Unare es uno de los ecosistemas costeros más importantes de Venezuela desde el punto de vista pesquero. Durante las décadas de 1980 y 1990, los cambios en su régimen hidrológico han afectado las características fisicoquímicas del agua, con consecuencias sobre la composición y abundancia de la fauna asociada. Un ejemplo de estas variaciones es la abundante presencia de Gobioides broussonnetii, una especie de pez registrada recientemente en este sistema. Por tal razón es importante identificar nuevos procesos ecológicos que pudiesen estarse dando en la laguna. El detrito es el componente más importante en la dieta de G. broussonnetii, seguido por un componente vegetal y animal asociado a este detrito: esta especie es un consumidor primario detritívoro, lo que podría relacionarse con su horario matutino de actividad. Esta especie no es capturada regularmente en los muestreos mensuales, lo cual hacer pensar que es un visitante ocasional de la laguna.
Subject(s)
Animals , Feeding Behavior/physiology , Diet , Ecosystem , Fishes/physiology , Gastrointestinal Contents , Seasons , VenezuelaABSTRACT
In this study, the rates of tissue regeneration and recovery from injuries that emulated the bites of either butterfly or parrotfish on colonies of Montastraea annularis exposed to different sedimentation regimesp were determined. Two small reef patches were chosen close to key Dos Mosquises, north of the Venezuclan mainland. Sixteen colonies (8 treatments + a single replicate) were artificially damaged at each patch and their recovery was monitored for three months by photographic means. The lesions were inflicted using two different techniques: scratching the polyps with a hard-nylon brush to resemble parrotfish (Scaridae) damages (Lesions Type 1) or jetting out the tissue with a syringe to simulate butterflyfish (Chaetondontidae) bites (Lesions Type 2). The diameter of the wounds ranged from 5 (small lesion) to 8 cm (large lesions) and both kinds were inflicted on the top and bottom of the colonies, with a single replicate for each treatment. The main factors affecting the recovery of the colonies' surface were lesion features (type, position and size), turbidity and chiefly, the sedimentation rate...
Subject(s)
Animals , Environment , Regeneration , Wounds and Injuries , Geologic Sediments , Time Factors , VenezuelaABSTRACT
En estudios ictiológicos realizados en praderas monoespecíficas de la fanerógama Thalassia testudinum, se determinaron un total de 7 registros nuevos de peces: dos géneros, Chilorhinus (Xenocongridae) y Parophidion (Opphidiidae); tres especies, Scorpaena bergi (Scorpaenidae), Sparisoma atomarinium (Scaridae) y Apogon aurolineatus (Apogonidae), para Venezuela; finalmente dos especies Scorpaena isthmensis (Scorpaenidae) y Crytotomus roseuus (Scaridae) corresponden a nuevos registros para el Parque Nacional Archipiélago Los Roques