Gastropods as intermediate hosts of Angiostrongylus spp. in the Americas: bioecological characteristics and geographical distribution

BACKGROUND Intermediate hosts are key organisms in maintaining parasite life cycles, because they can act as amplifiers in the transmission from natural reservoirs to humans. One of the most important groups of intermediate hosts for zoonotic nematode infections are gastropods,slugs and snails. These are essential organisms in the larval development of Angiostrongylus species. OBJECTIVES The objective of this paper is to review reports of Angiostrongylus spp. in naturally infected gastropods from the Americas, taking into account the diagnostic methods used in their identification, to be able to provide more accurate list of their intermediate hosts. We also discuss the factors that aid the dispersion of Angiostrongylus spp. in the Americas. METHODS This study reviews scientific publications and book sections on Angiostrongylus spp. in the Americas, including original works assessing larvae of Angiostrongylus in intermediate hosts. The eligible reports were classified accordingly to their geographical location, year of first record, and the larvae identification methodologies used. Digital repositories were used for the search. The bioecological characteristics of the main intermediate hosts are summarised. FINDINGS A total of 29 gastropod species that are naturally infected with Angiostrongylus spp. have been reported as intermediate hosts, 16 of which are land snails, two are freshwater snails, and 11 land slugs. MAIN CONCLUSIONS This study highlights the importance of integrative studies, analysing both the etiological agent and its transmission dynamic in the environment, the biological and ecological characteristics of the hosts, and the impact on host populations. It is necessary to increase interdisciplinary studies to determine the potential epidemiological health risk of angiostrongyliasis in the Americas, and thus be able to establish prevention, monitoring and contingency strategies in the region.

Shell occupation by the hermit crab Dardanus insignis (Decapoda, Diogenidae) from the north Coast of São Paulo state, Brazil / Ocupação de conchas pelo ermitão Dardanus insignis na costa norte do estado de São Paulo, Brasil

Abstract The pattern of shell occupation by the hermit crab Dardanus insignis (Saussure, 1858) from the subtropical region of southeastern coast of Brazil was investigated in the present study. The percentage of shell types that were occupied and the morphometric relationships between hermit crabs and occupied shells were analyzed from monthly collections conducted during two years (from January 1998 to December 1999). Individuals were categorized according to sex and gonadal maturation, weighed and measured with respect to their cephalothoracic shield length (CSL) and wet weight (CWW). Shells were measured regarding their aperture width (SAW), dry weight (SDW) and internal volume (SIV). A total of 1086 hermit crabs was collected, occupying shells of 11 gastropod species. Olivancillaria urceus (Roding, 1798) was most commonly used by the hermit crab D. insignis, followed by Buccinanops cochlidium (Dillwyn, 1817), and Stramonita haemastoma (Linnaeus, 1767). The highest determination coefficients (r2 > 0.50, p < 0.01) were recorded particularly in the morphometric relationships between CSL vs. CWW and SAW vs. SIV, which are important indication that in this D. insignis population the great majority the animals occupied adequate shells during the two years analysed. The high number of used shell species and relative plasticity in pattern of shell utilization by smaller individuals of D. insignis indicated that occupation is influenced by the shell availability, while larger individuals demonstrated more specialized occupation in Tonna galea (Linnaeus, 1758) shell.

Resumo O padrão de ocupação de conchas pelo ermitão D. insignis (Saussure, 1858) na região subtropical da costa sudeste do Brasil, foi investigada no presente estudo. Foram analisadas a percentual de tipos de conchas que foram ocupados e as relações morfométricas entre os ermitões e conchas ocupadas, a partir de coletas mensais realizadas durante dois anos (de janeiro de 1998 a dezembro de 1999). Os indivíduos foram classificados de acordo com o sexo e maturação, pesados ​​e medidos em relação ao comprimento escudo cefalotoracico (CEC) e peso úmido (CPU). As conchas foram medidas em relação à sua largura de abertura (LAC), peso seco (PSC) e volume interno (VIC). Um total de 1.086 ermitões foram coletados, ocupando conchas de 11 espécies de gastrópodos. Olivancillaria urceus (Roding, 1798) foi a mais utilizada pelo ermitão D. insignis, seguido por Buccinanops cochlidium (Dillwyn, 1817), e Stramonita haemastoma (Linnaeus, 1767). Os maiores coeficientes de determinação (r2 > 0,50, p < 0,01) foram registrados principalmente nas relações morfométricas entre CEC e CPU contra LAC e VIC, que é uma importante indicação de que nesta população de D. insignis a grande maioria dos animais ocupavam conchas adequadas durante os dois anos analisados. O elevado número de espécies de conchas utilizadas ​​e a relativa plasticidade no padrão de ocupação de conchas pelos menores indivíduos de D. insignis indicaram que a ocupação é influenciada pela disponibilidade de conchas, enquanto os indivíduos maiores demonstraram uma ocupação mais especializadas na concha de Tonna galea (Linnaeus, 1758).

Variación fenotípica de la concha en Neritinidae (Gastropoda: Neritimorpha) en ríos de Puerto Rico

Phenotypic variability of the shell in Neritinidae (Gastropoda: Neritimorpha) in Puerto Rican rivers. Gastropods of the Neritinidae family exhibit an amphidromous life cycle and an impressive variability in shell coloration in Puerto Rican streams and rivers. Various nominal species have been described, but Neritina virginea [Linné 1758], N. punctulata [Lamarck 1816] and N. reclivata [Say 1822] are the only broadly reported. However, recent studies have shown that these three species are sympatric at the river scale and that species determination might be difficult due to the presence of intermediate color morphs. Individuals (8 751) were collected from ten rivers across Puerto Rico, and from various segments and habitats in Mameyes River (the most pristine island-wide) during three years (2000-2003), and they were assigned to one of seven phenotypes corresponding to nominal species and morphs (non-nominal species). The “axial lines and dots” morph corresponding to N. reclivata was the most frequent island-wide, while the patelliform N. punctulata was scant, but the only found in headwater reaches. The “yellowish large tongues” phenotype, typical of N. virginea s.s. was the most frequent in the river mouth. The frequency of secondary phenotypes varied broadly among rivers, along the rivers, and among habitats, seemly influenced by salinity and predation gradients. The occurrence of individuals with coloration shifts after predation injuries, suggests phenotypic plasticity in the three nominal species, and urges for the use of molecular markers to unravel the possible occurrence of a species complex, and to understand the genetic basis of polymorphism. The longitudinal distribution of individual sizes, population density and egg capsules suggested the adaptive value of upstream migration, possibly to avoid marine predators. Rev. Biol. Trop. 62 (Suppl. 2): 53-68. Epub 2014 April 01.

Los gasterópodos Neritinidae de Puerto Rico presentan un ciclo de vida anfídromo y exhiben polimorfismo en los patrones de coloración de la concha. Se identificó que la oviposición aumenta río arriba conforme los individuos alcanzan mayores tamaños, a pesar de que la densidad poblacional disminuye. La frecuencia de siete fenotipos previamente establecidos se analizó en diez ríos de la isla durante dos años (n=8 751 individuos). Debido a que el río Mameyes es el más conservado, se tomó como modelo para estudiar la variación a lo largo del río y entre hábitats durante tres años. El fenotipo de líneas axiales y puntos (N. virginea) fue el predominante en toda la isla y el fenotipo pateloide (N. punctulata) fue el menos frecuente. Se observaron diferencias significativas de las frecuencias de los fenotipos (principalmente en los secundarios) entre ríos, a lo largo de ellos y entre hábitats. Esta variabilidad espacial puede responder a gradientes de salinidad y depredación. Se observó plasticidad fenotípica en algunos individuos.

Densidad, estructura de tallas y actividad reproductiva del caracol rosado Eustrombus gigas (Mesogastropoda: Strombidae) en Banco Chinchorro, México / Density, size structure and reproductive activity of the pink conch Eustrombus gigas (Mesogastropoda: Strombidae) in Banco Chinchorro, Mexico

The pink conch Eustrombus gigas is an important fisheries resource. At the regional level in the Caribbean, over-exploitation and habitat destruction have caused a decrease in the abundance of this resource. In order to provide necessary information for the species management in Mexico, this work aimed to analyze the total density, adult density, size structure and reproductive behavior of pink conch population at Banco Chinchorro during 2009-2010. Data from three seasons were obtained (rainy, dry and cold fronts periods) in three areas: Norte (North), Centro (Center) and Sur (South). The organisms were separated into two groups: (a) the criteria based upon legal harvest in Mexico: legal size conchs (siphonal length≥200mm) and illegal size conchs (siphonal length<200mm), and (b) the criteria based upon sexual maturity using the 15mm lip thickness standard: lip<15mm as juvenile conch and lip≥15mm as adult conch. Copulation, spawning, egg masses and aggregations were evaluated as reproductive evidences. The highest total density was observed during the dry season with 384ind./ha, and the lowest during the rainy season with 127ind./ha. The highest density was reported at Sur (385ind./ha) and the lowest at Norte (198ind./ha). The highest adult density was observed during the rainy season (8.33ind./ha), and the lowest occurred in the dry season (6.11ind./ha). Adult density values were 5.55, 7.05 and 8.33ind./ha for Centro, Sur and Norte areas, respectively. Adult densities were lower than the threshold needed for reproduction, and 42% of the population may be vulnerable to fishing, as they had the minimum size for catch (Lsi 200mm). Furthermore, only 2.2% of the population reached a Gl>15mm as sexual maturity indicator. During the study period, only six evidences of reproductive activity were observed. The smaller densities reported at Banco Chinchorro may cause reproduction events to be almost absent which in turn is sufficient ...

Eustrombus gigas es uno de los recursos pesqueros costeros más valiosos en la región del Caribe y constituye un molusco con un elevado valor estético y ecológico. En esta investigación se evalúa su densidad total, densidad de adultos, la estructura de tallas y frecuencia de evidencias reproductivas en Banco Chinchorro, México, periodo 2009-2010; durante tres períodos (de lluvias, seca y de frentes fríos) en tres zonas: Norte, Centro y Sur. La densidad total para el área de estudio varió de 127ind./ha en lluvias a 384ind./ha en seca, la menor densidad se presentó en la zona Norte del Banco (198ind./ha) y la mayor en la zona Sur (385ind./ha). La densidad de caracoles adultos fue baja (6.11ind./ha en seca y 8.33ind./ha en lluvias y 5.55, 7.05 y 8.33ind./ha para las zonas Centro, Sur y Norte, respectivamente). Las densidades de adultos estuvieron por debajo del umbral mínimo necesario para mantener la reproducción. El 42% de la población es vulnerable a la pesca (Lsi≥200mm); sin embargo, solo 2.2% de la población alcanza un Gl>15mm. Solo se observaron seis evidencias de reproducción durante el período de estudio, lo que señala la presencia del efecto Allee en la población y la urgente necesidad del cierre de su pesquería. Se proponen tres puntos importantes para el manejo de la especie: cierre de la pesca, monitoreo de la población y la implementación refugios pesqueros.

Declining densities and reproductive activities of the queen conch Strombus gigas (Mesogastropoda: Strombidae) in Banco Chinchorro, Eastern Caribbean, Mexico / Disminución de la densidad y actividades reproductivas de la concha reina Strombus gigas (Mesogastropoda: Strombidae) en el Banco Chinchorro, Caribe Oriental

Queen conch is a gastropod inhabiting the Caribbean Sea, it represents the second largest fishery after the spiny lobster, but it has been extensively captured in the area. In order to know its population status in Chinchorro Bank, we determined conch density changes and its effects on reproductive activities, between July and November 2009. For this, data on conch density, morphology and reproductive activities were obtained from 15 sites within three fishing zones, and compared with previously collected data (1990, 1992, 1994, and 1997). Data showed that adult density decreased with time, from 10 700ind./ha in 1990, to 198ind./h in 2009. Neither egg masses nor spawns were found and mating was only observed once in July 2009. In July, adult (lip>4mm) density in the Southern zone was 23ind./ha whereas in the Northern zone and Central zone densities were 15 and 9ind./ha respectively. In November, density was somewhat higher: Southern zone 96ind./ha; Central zone 39ind./ha and Northern zone had 38ind./ha. In July, mean shell length was 170.80±46.28mm, with a higher median abundance at 180-189mm. In November, higher frequency was 187.63±45.14mm, maximum at 210-219mm interval. For the last 10 years period, mean adult conch densities have diminished in each zone, which might be the main cause of decreased reproductive activities of the conch at Banco Chinchorro. It is therefore an immediate need to analyse the management plan for this species in this Reserve and perhaps to promote a re-population of queen conch and culture activities. Rev. Biol. Trop. 61 (4): 1671-1679. Epub 2013 December 01.

El caracol Rosado es un gasterópodo que habita en el Caribe, y representa la segunda pesquería después de la langosta espinosa, sin embargo, el caracol ha sido pescado a niveles de casi extinción. Para conocer el estatus de la población se analizaron los cambios de densidad del caracol rosado en Banco Chinchorro y su efecto en las actividades reproductivas entre julio y noviembre 2009. Se recolectaron datos de densidad y morfología en tres zonas de pesca en 15 localidades; y se compararon con datos recolectados previamente en los mismos sitios (1990, 1992, 1994, y 1997). Los datos mostraron que la densidad de adultos ha decrecido con el tiempo de 10 700 (ind./ha) en 1990 a 198 (ind./ha). Las actividades reproductivas o productos se registraron, no se encontraron ni masas de huevo ni desoves, y únicamente se observó una copulación en julio. Considerando únicamente a los adultos (labio>4mm), en julio 2009, la densidad fue de 23ind./ha, mientras que en la zona norte y centro las densidades fueron 15 and 9 (ind./ha). En noviembre 2009, la densidad fue ligeramente más alta: zona sur 96 (ind./ha); zona Centro 39 (ind./ha) y zona Norte 38 (ind./ha). En julio (2009) la longitud de concha promedio fue de 170.80±46.28mm, con una mayor abundancia en las tallas 180-189mm. En noviembre (2009) la frecuencia más alta ocurrió en las talla promedio 187.63±45.14mm, con un intervalo de 210-219mm de longitud de concha. En los últimos 10 años, la densidad de los caracoles adultos ha disminuido en cada una de las zonas de pesca, lo cual podría ser la causa de la disminución de las actividades reproductivas del caracol rosado en Banco Chinchorro.

Density and reproduction of the Queen Conch Eustrombus gigas (Mesogastropoda: Strombidae) at Cabo Cruz, Desembarco del Granma National Park, Cuba / Densidad y reproducción de la concha reina Eustrombus gigas (Mesogastropoda: Strombidae) en Cabo Cruz, Parque Nacional Desembarco del Granma, Cuba

The queen conch Eustrombus gigas is an important fisheries resource in the Caribbean region. In Cuba Island the studies about this resource are very scarce and particularly in the Southeastern regions of the country. With the aim to get important fishery information about this gastropod, adult Queen Conch density and frequency of reproductive activity were evaluated in Cabo Cruz, Cuba, during 2009-2010. Data from three seasons were obtained (rainy, dry and cold fronts periods) from three different areas: Farito, Guafe and Laguna. The highest density was observed in cold fronts season (468.5ind./ha) and the lowest occurred during the dry season (268.5ind./ha). The highest density was reported at Laguna (520.4ind./ha) and the lowest at Farito (290.9ind./ha). In total, 158 reproductive events were observed. The highest frequency was reported in rainy season (36%), followed by dry (9%) and cold fronts (5%) seasons. Reproductive behavior (mating and egg laying) was related to temperature and photoperiod. Reproductive activity was observed during the whole year, which suggests the existence of an important Queen Conch reserve in the Southeastern region of Cuba and an apparently self-sufficient population for recruitment. From our results we may conclude that, the population’s sustainable exploitation is viable if the following management measures are observed: functional zoning within the area, rotation of fishing areas and a closed season. We recommend that the Laguna site should be protected as a reproduction zone and banned for fishing activities.

El Eustrombus gigas es un recurso pesquero importante en la región del Caribe. En Cuba, los estudios acerca de este recurso son muy escasos y en la zona Sur-oriental del país son casi nulos. En este trabajo se evalúa la densidad de adultos y frecuencia de la evidencia reproductiva de Eustrombus gigas Linneus 1758 en Cabo Cruz, Cuba, en el periodo 2009-2010. Se obtuvieron datos de tres períodos (lluvias, seca y frentes fríos) en tres zonas: Farito, Guafe y Laguna. La mayor densidad de adultos se observó en frentes fríos (468.5ind./ha) y la menor en seca (268.5ind./ ha). Por zonas, la mayor densidad de adultos se reportó en Laguna (520.4ind./ha) y la menor en Farito (290.9ind./ha). Se observaron 158 evidencias reproductivas. La mayor frecuencia se reportó en lluvias (36%). La temperatura se relacionó con la frecuencia de desove y cantidad de masas de huevos, y el fotoperiodo con la cantidad de agregaciones y frecuencia de cópula. Se observó actividad reproductiva intensa durante todo el año, lo que sugiere una importante reserva de la especie en la región sur-oriental de Cuba y una aparente autosuficiencia de la población para el reclutamiento. La explotación sostenible de la población es viable y Laguna debe ser protegida como zona de reproducción.

Dinámica poblacional y reproductiva de Turbinella angulata y Busycon perversum (Mesogasteropoda: Turbinellidae y Melongenidae) en el Banco de Campeche, México / Turbinella angulata and Busycon perversum (Mesogasteropoda: Turbinellidae and Melongenidae) population and reproductive dynamics in the Campeche Bank, Mexico

Turbinella angulata and Busycon perversum are two marine gastropods that support the 90% of conch fisheries in the Gulf of Mexico, nevertheless there is no information available to support a management strategy for both species. The aim of this work was to obtain preliminary fishery information to promote management actions for both species in the Campeche Bank. The population of conchs was sampled in 12 transects (150x1.5m) by SCUBA diving from April 2008 to March 2010. All conchs were collected and siphonal length (SL) was measured. These samples were complemented with data from the commercial catches, analyzing a total of 2 832 individuals of T. angulata. Siphonal length varied between 63 and 282mm. Sex ratio was of 0.98:1 female:male. The von Bertalanffy growth equation parameters were: L=346mm; K=0.30 and t=-0.24. Spawning extended from January to May with a long resting stage from June to September for over 80% of the adult population. The first gonadic maturity (L) was at 210mm (SL) for females and 200mm for males. For B. perversum a total of 1 655 individuals were analyzed. Siphonal length varied between 78 and 291mm with significant differences between male and female (p0.05). Sex ratio was of 1:0.25 female:male. The growth parameters obtained were: L=360mm; K=0.35 and t=-0.19. The spawning period was from August to December with resting stage from January to April. The L was 215mm (LS) for females and 190mm for males. Both species presented one recruitment pulse. These results will be useful to design management schemes based on population dynamics and reproductive attributes.

Turbinella angulata y Busycon perversum aportan la mayor captura de caracol en el Golfo de México (90%).Se realizaron muestreos mediante transectos lineales (150x1.5m) de abril 2008 a marzo 2010 y en las capturas comerciales del Banco de Campeche (18°-20º N - 90°- 91º O). 2 832 individuos de T. angulata fueron medidos, las tallas variaron entre 63-282mm (LS), la proporción hembras:machos fue 0.98:1. Los valores de crecimiento fueron: L=346mm, K=0.30 y t0=-0.24. El periodo reproductivo fue de enero a mayo con reposo de junio a septiembre (80%). La talla de primera madurez (L) fue de 210mm (LS) en hembras y 200mm en machos. De B. perversum,1 655 ejemplares fueron analizados con tallas entre 78-292mm, presentando diferencias significativas entre longitudes de machos y hembras (p0.05). La proporción hembras:machos fue 1:0.25. Los valores de crecimiento fueron L=360 mm, K=0.35 y t=-0.19. El periodo reproductivo fue de agosto a diciembre con reposo de enero a abril. La L50 fue de 215mm (LS) en hembras y 190mm en machos. Se observó un pulso de reclutamiento anual en ambas especies relacionado con el incremento en la temperatura marina. Los resultados ayudarán a definir un esquema de manejo basado en los atributos poblacionales y reproductivos de las especies.

Effects of short-term sediment nutrient enrichment and grazer (Neritina reclivata) removal on sediment microalgae in a shallow eutrophic estuary (Alabama, USA)

The olive snail (Neritina reclivata) is ubiquitous in tropical and sub-tropical systems of the Gulf of Mexico, however its impacts on sediment microalgae have been little studied. Many coastal systems around the world are being eutrophied due to human activities, and seemingly they will continue to be eutrophied to a further extent in the future. Exploring the single and combined impacts of further nutrient enrichment and grazing by the olive snail on sediment microalgae in such eutrophic systems is an important question for our understanding and management of these systems. Here we examine the effects of short-term nutrient enrichment and grazing by the olive snail N. reclivata on sediment microalgal biomass and composition in a shallow eutrophic estuary (Weeks Bay, Alabama, USA) of the Northern Gulf of Mexico. For this, we performed a series of factorial experiments adding or not nutrients and removing or not the snail, for a total of four treatments in each experiment: ambient grazing, ambient nutrients; ambient grazing, increased nutrients; no grazing, ambient nutrients; and no grazing, increased nutrients. We did not find any significant impact of nutrient addition in any of the eight short-term (i.e. four days) experiments carried out. Impacts by the snail were minor; we only found a decrease in biomass due to snail grazing in one of the eight experiments, and no impacts on microalgal (i.e. diatom) composition. High ambient nutrient concentrations in the sediment porewater and low snail abundances on the sediment could explain these findings. Our results suggest that ephemeral, short-term nutrient pulses into eutrophic coastal systems of the Northern Gulf of Mexico, such as Weeks Bay (Alabama, USA), should not greatly affect the abundance of sediment microalgae, even though those pulses occur in well-lit areas. The results further suggest the snail N. reclivata is not a major control of sediment microalgal populations in the subtidal sedimentary areas studied. Our findings contrast with the results of past work in sediments with well-lit and nutrient poor conditions, or sediments with high densities of other snail grazers. In conjunction this and other investigations indicate that the response of sediment microalgae to nutrient enrichment and modified grazer abundance depends to a large extent on the initial levels of nutrient availability and grazing before the system is altered.

El caracol Neritina reclivata está presente en los sistemas tropicales y subtropicales del Golfo de México, sin embargo, su impacto en los sedimentos de microalgas ha sido poco estudiado. Muchos de los sistemas costeros de todo el mundo están siendo eutrofizados debido a actividades humanas, y al parecer van a seguir siendo eutrofizados en mayor grado en el futuro. La exploración de los efectos individuales y combinados de un mayor enriquecimiento de nutrientes y la herviboría por este caracol en microalgas de sedimentos en estos sistemas eutróficos es una cuestión importante para la comprensión y el manejo de estos sistemas. Aquí se examinan los efectos a corto plazo del enriquecimiento de nutrientes y herviboría del caracol de olivo sobre la biomasa y composición de microalgas de sedimentos en un estuario eutrófico superficial (Weeks Bay. Alabama, USA) del norte del Golfo de México. Para esto se llevaron a cabo una serie de experimentos factoriales añadiendo o no nutrientes y removiendo o no el caracol, para un total de cuatro tratamientos en cada experimento: ambiente con herviboría sin nutrimentos añadidos, ambiente con herviboría y nutrimentos añadidos, ambiente sin herviboría sin nutrimentos añadidos, y ambiente sin herviboría con nutrimentos añadidos. No se encontró ningún impacto significativo por la adición de nutrimentos en ninguno de los ocho experimentos a corto plazo (i.e. cuatro días). Los impactos debidos al caracol fueron menores, sólo se encontró un decrecimiento en la biomasa por herviboría del caracol en uno de los ocho experimentos, y no hubo impacto en la composición de microalgas (i.e. diatomeas). Ambientes con alta concentración de nutrimentos del sedimento y baja abundancia del caracol sobre el sedimento pueden explicar estos resultados. Los resultados obtenidos sugieren que pulsos efímeros y de corto plazo en sistemas costeros eutrofizados del Norte del Golfo de México tal como Weeks Bay (Alabama, USA), no deberían afectar de gran manera la abundancia de microalgas sobre el sedimento, a pesar de que los pulsos ocurran en áreas bien iluminadas. Además los resultados sugieren que el caracol N. reclivata no ejerce mayor control sobre las poblaciones de microalgas en las áreas submareales y sedimentarias estudiadas. Nuestros hallazgos contrastan con resultados de trabajos anteriores en sedimentos con buena iluminación y pobres condiciones nutritivas, o sedimentos con altas densidades de otros caracoles herbívoros. En conjunto, esta y otras investigaciones indican que la respuesta de microalgas en sedimentos al enriquecimiento de nutrientes y abundancia modificada de herbívoros depende en gran medida de los niveles iniciales de disponibilidad de nutrientes y herviboría antes de que el sistema se vea alterado.

Efecto de la conversión del manglar a potrero sobre la densidad y tallas de dos gasterópodos en el delta del río Turbo (golfo de Urabá, Caribe colombiano) / Effects mangrove conversion to pasture on density and shell size of two gastropods in the Turbo River Delta (Urabá Gulf, Caribbean coast of Colombia)

Mangrove deforestation is widespread in the Greater Caribbean but its impact on macrobenthos has not been evaluated to date. In order to assess the impact of mangrove conversion to pasture, densities and shell sizes of two dominant gastropods (Neritina virginea and Melampus coffeus) were compared among four mangrove types: 1) Rhizophora mangle-dominated fringing mangroves, 2) Avicennia germinans-dominated basin mangroves, 3) Mixed-species basin mangroves, and 4) A. germinansbasin mangroves converted to pastures, in the Turbo River Delta (Urabá Gulf, Colombia). Mangrove types were polygon-delimited with satellite images and color aerial photographs were taken in 2009. various (n<5) polygons per mangrove type were sampled in January, July and December 2009, and a total (n<20) 0.025m²-quadrats were randomly placed along each polygon. Forest structure variables, pore-water physico-chemical variables and sediment-grain metrics were measured in the four mangrove types. Mean density and size of both gastropod species were measured. The results showed that the mean density and size of both species were significantly greater in R. mangle-fringing mangroves. N. virginea density decreased gradually towards the A. germinans-basin mangroves seemly related to the diadromous life-history. This species nearly disappeared in the neighboring pastures because individuals were constrained to a few remaining flooded areas. In the pastures, M. coffeus individuals were clumped in the remaining A. germinans trees due to its climbing behavior as a pulmonate. We hypothesize that the decline of these two gastropods was related to physical microhabitat (e.g. trees, prop roots, and seedlings) degradation, and alteration of soil properties (e.g. temperature, pH, organic matter content). Finally, we also hypothesize that the local extinction of N. virginea due to clear-cutting may exert strong negative effects on the ecosystem function because it is a dominant omnivore.

El delta del río Turbo es una de las áreas del golfo de Urabá, Colombia donde la tala de manglar es más extensa y activa, por lo tanto, se evaluó el impacto de la conversión de manglar a potrero, comparando la densidad y talla promedio de dos gasterópodos (Neritina virginea y Melampus coffeus), variables dasonómicas, físico-químicas intersticiales y granulométricas del suelo entre varios parches de: 1) manglar de franja, 2) manglar de cuenca, 3) manglar de cuenca mixto y 4) manglar de cuenca convertido a potrero, en el delta del río Turbo de este golfo, entre enero y diciembre 2009. Las densidades y tallas de los gasterópodos fueron mayores en el manglar de franja. N. virginea fue muy abundante pero disminuyó hacia el manglar de cuenca (debido a sus hábitos diádromos), y desapareció casi completamente en los potreros, donde los individuos estuvieron agregados en las pocas áreas anegadas. En los potreros, los individuos de M. coffeus estuvieron agrupados en los árboles remanentes debido a su hábito arborícola y su condición de pulmonado. Se sugiere que la escasez de los gasterópodos está relacionada con la degradación del microhábitat físico, y la alteración de propiedades del suelo. Finalmente, también planteamos que la extinción local de N. virginea debida a la tala puede ejercer fuertes efectos negativos sobre la función ecosistémica debido a que es un omnívoro dominante.

Reproductive cycle and embryonic development of the gastropod Melampus coffeus (Linnaeus, 1758) (Ellobiidae) in the Brazilian Northeast / Ciclo reprodutivo e desenvolvimento embrionário do gastrópode Melampus coffeus (Linnaeus, 1758) (Ellobiidae) no Nordeste do Brasil

Melampus coffeus belongs to a primitive group of pulmonate mollusks found mainly in the upper levels of the marine intertidal zone. They are common in the neotropical mangroves. Little is known about the biology of this species, particularly about its reproduction. The aim of this study was to 1) characterize the morphology and histology of M. coffeus' gonad; 2) describe the main gametogenesis events and link them to a range of maturity stages; 3) chronologically evaluate the frequency of the different maturity stages and their relation to environmental factors such as water, air and sediment temperatures, relative humidity, salinity and rainfall; and 4) characterize M. coffeus' spawning, eggs and newly hatched veliger larvae. Samples were collected monthly between February, 2007 and January, 2009 from the mangroves of Praia de Arpoeiras, Acaraú County, State of Ceará, northeastern Brazil. The characterization of the gonad development stages was carried out using routine histological techniques. The results of this study show that Melampus coffeus is a simultaneous hermaphrodite. The follicles have masculine and feminine elements, interleaved within the gonad. M. coffeus presents a well-defined synchronous reproductive cycle, showing successive maturation, release and resting periods. The average diameter of the oocytes was negatively correlated with salinity and positively correlated with rainfall. The results show that no reproductive activity occurs during periods of drought. After the dry season, the increasing rainfall levels and reduced salinity lead to the appearance of very dense populations, predominantly composed of small individuals.

Melampus coffeus encontra-se em um grupo primitivo de moluscos pulmonados, primordialmente marinhos, habitantes dos níveis superiores da zona entremarés, comum em manguezais do Oceano Atlântico. Pouco se sabe sobre a biologia da espécie, em especial, sobre a sua reprodução. Os objetivos deste trabalho foram: 1) caracterizar morfo-histologicamente a gônada de M. coffeus; 2) descrever os principais eventos da gametogênese e associá-los a uma escala de estágios de maturidade; 3) avaliar temporalmente a frequência dos estágios de maturidade e sua possível relação com os fatores ambientais, como a temperatura da água, do ar e do sedimento, a umidade relativa, a salinidade e a pluviosidade, e 4) caracterizar a postura, os ovos e a véliger recém-eclodida de M. coffeus. Foram realizadas coletas mensais de fevereiro de 2007 a janeiro de 2009, no manguezal da Praia de Arpoeiras, município de Acaraú-Ceará, na Região Nordeste do Brasil. A caracterização das fases de desenvolvimento da gônada foi realizada utilizando-se técnicas histológicas de rotina. Os resultados deste estudo mostram que Melampus coffeus é um hermafrodita simultâneo. Os folículos apresentam elementos masculinos e femininos, distribuindo-se na gônada intercalados radialmente. M. coffeus apresenta um ciclo reprodutivo sincrônico bem definido, evidenciando-se períodos sucessivos de amadurecimento, de liberação e de repouso. O diâmetro médio dos oócitos apresentou correlação negativa com a salinidade e positiva com a pluviosidade. Os resultados indicam que, nos períodos de estiagem, não há atividade reprodutiva. Após essa estação, quando os valores de pluviosidade aumentam e a salinidade diminui, as populações são bastante densas e predominam indivíduos pequenos.

Reproduction of Omalonyx matheroni (Gastropoda: Succineidae) under laboratory conditions

The life histories of succineids have received relatively little attention. To evaluate life history characteristics of Omalonyx matheroni, we studied a Brazilian population (Reserva Particular do Patrimônio Natural Feliciano Miguel Abdala, in Caratinga, Minas Gerais, Brazil) under laboratory conditions. The aims of the present study were (1) to describe in detail an appropriate rearing method; (2) to investigate the effects of different temperature and photoperiod conditions; and (3) to assess the effects of self and cross-fertilization on the reproductive biology of these mollusks. We studied the oviposition site, the time to sexual maturity and the influences of photoperiod and temperature on reproductive parameters of O. matheroni reared under laboratory conditions. We tested three combinations of temperature and photoperiod, designated A, B and C (A: 25ºC, 24 hours of light; B: environmental conditions of temperature and photoperiod, characterized as follows: average máximum temperature=27.1ºC, average minimum temperature=18.3ºC, average day length=12.06 hours; and C: 25ºC, zero hours of light) and two rearing densities (I: isolated and G: grouped) on reproductive parameters (number of eggs per egg mass, number of unviable eggs per mass, egg mass incubation period, and duration of the hatching period). A total of 186 individuals and 565 egg masses were studied. Data were analyzed by Student’s t-test, two-way ANOVA and Chi-Square test. Eight generations were produced (March/2004-March/2006), from 35 field specimens, 91% of 3 197 eggs hatched. The time to sexual maturity was approximately three months for individuals reared in groups or in isolation (Student’s t-test: t=1.41, df=31, p=0.16); however, they differed significantly in weight (Student’s t-test: t=3.6, df=31, p<0.001). Regarding the influences of temperatura and photoperiod on reproductive parameters, under natural environmental conditions, individuals produced a greater number of eggs per mass (ANOVA: F2,573=84.15, p<0.001), with a longer incubation period (ANOVA: F2;559=170.05, p<0.001). The extreme photoperiod conditions of 24 hours of light or zero hours of light likely imposed stress and could be related to the significant reductions in the number of eggs per mass, and egg incubation period as well as the increased synchrony in egg hatching. No correlations were observed between the number of unviable eggs per mass and the temperature, photoperiod (ANOVA: F2,573=0.87, p=0.92) or rearing density (ANOVA: F1,573=0.21, p=0.64). Individuals reared in isolation under natural conditions produced more eggs per mass and did not presented any disadvantage with respect to the variables analyzed as compared to the animals reared in groups. These results indicate that O. matheroni can successfully reproduce by selfing. Rev. Biol. Trop. 60 (2): 553-566. Epub 2012 June 01.

Gasterópodos asociados al alga calcárea Halimeda opuntia (Udoteaceae) en Puerto Rico

Gastropods associated with the calcareous alga Halimeda opuntia (Udoteaceae) in Puerto Rico. Gastropod communities associated with the calcareous green alga Halimeda opuntia are described and compared for two Puerto Rico coral reefs: one in the northeast with front tradewinds (windward zone) and one in the southwest (leeward zone). We analyzed the content of 21 lots (2432 g) of H. opuntia from leeward zone and 15 lots (2448 g) from the windward zone. In total we recovered 526 gastropods (prosobranchs) classified in 54 taxa. Thirteen species of gastropods represented 79.6% of the community. Differences between species richness and mean density values were not significant (p>0.100). Forty species were identified from leeward and thirty one (31) species from windward. Gastropod mean density was 13.9 /100g of algae in leeward and 7.6/100g in windward. Significant differences were found for the Simpson Diversity Index (0.91 in the leeward and 0.82 in the windward community; t=3.44, α=0.005). We found no correlation between the weight of the algae and the frequency of the gastropods (R²=0.0893 in leeward, 0.0249 windward and 0.0923 for both). The relationship between species composition in lots of windward and leeward study sites was explored via polar ordination and no segregation was found. When compared, the gastropod communities found in H. opuntia collected in coral reefs in Puerto Rico were more similar within them than any other communities found in other genera of seaweed and in other environments. Our results agree with the hypothesis that H. opuntia offers the interstitial community a protected microhabitat from water movement impact. H. opuntia creates more homogenous conditions than those of the habitat where we found the algae. Rev. Biol. Trop. 56 (4): 1665-1675. Epub 2008 December 12.

Se describen y comparan las comunidades de gasterópodos asociados al alga verde calcárea H. opuntia. Se compararon estas comunidades en arrecifes coralinos de lugares geográfica y ambientalmente diferentes, uno en el noreste de Puerto Rico, frente a los vientos alisios (barlovento), el otro en el suroeste (sotavento). Se analizó el contenido de 15 lotes (2432 g) de H. opuntia recolectadas en la estación de sotavento y 21 lotes (2448 g) en la de barlovento. En los 36 lotes se recuperaron 526 gasterópodos (prosobranquios) que se clasificaron en 54 taxones. Trece especies de gasterópodos representaron el 79.6% de la muestra de la comunidad. No encontramos diferencias significativas en las densidades de gasterópodos ni en la riqueza de especies (p>0.100). La densidad promedio fue de 13.9/100 g alga en la estación de sotavento y 7.6/100 g en la de barlovento. Se identificaron 40 especies diferentes en las muestras de sotavento y 31 en las de barlovento. Solamente se encontraron diferencias significativas en los valores de diversidad (Simpson), de 0.91 para la comunidad de sotavento y de 0.82 en la de barlovento (t = 3.44, α = 0.05). No encontramos correlaciσn entre el peso de la muestra del alga y la frecuencia de gasterσpodos en ésta, R² = 0.0893 para sotavento, 0.0249 para barlovento y 0.0923 para datos combinados. Utilizando los métodos de ordenación polar se comprueba la similitud de las dos comunidades estudiadas. Estos resultados sostienen la hipótesis de que H. opuntia le ofrece a los organismos que viven en sus intersticios un microhábitat protegido del impacto del movimiento del agua, creando condiciones más homogéneas que las del hábitat donde encontramos creciendo el alga.

Diversidad de moluscos gasterópodos terrestres en la región del Pacífico de Nicaragua y sus preferencias de hábitat / Diversity of terrestrial gastropod mollusks in the Pacific region of Nicaragua, and their habitat preferences

Diversity of terrestrial gastropod mollusks in the Pacific region of Nicaragua, and their habitat preferences. Landsnail communities of the Nicaraguan Pacific Slope were studied. The study area was subdivided into 21 quadrats (ca. 40 x 40 km). A high taxonomic richness was found: 79 species, 43 genera and 23 families. Species richness (S) per quadrat ranged from 17 through 50. The biogeographic index presented higher values on quadrats 5 (3.04), 6 (3.03), 8 (2.96) and 11(2.96). Quadrat 11 had the highest species richness (S=50), and one of the highest biogeographic index values (IB=2.96). Gastropod mollusk communities are favored by sites with an illumination of filtered sun, associated to riparian forests and with a susbtratum of wet soils and leaf litter.

Se estudiaron las comunidades de moluscos gasterópodos terrestres de la región del Pacífico de Nicaragua, con el método de cartografiado UTM. El área de estudio fue subdividida en 21 cuadrículas. Se recolectaron un total de79 especies distribuidas en 43 géneros y 23 familias, lo que significa una alta riqueza de especies, géneros y familias.El valor más alto de riqueza de especies (S) correspondió a la cuadrícula 11 (S=50, Península de Chiltepe), y el valor más bajo a la cuadrícula 1 (S=17, Península de Cosigüina). El índice biogeográfico calculado con base en la información sobre distribución de las especies, presentó los valores más altos en las cuadrículas 5 (3.04), 6 (3.03), 8 (2.96) y 11(2.96). La cuadrícula 11 tuvo la mayor riqueza de especies (S=50) y uno de los mayores índices biogeográficos (IB=2.96). Esta cuadrícula contiene dos áreas protegidas y se encuentra en un estado de conservación relativamente bueno. El hábitat idóneo para una comunidad de moluscos gasterópodos terrestres presenta una iluminación de sol filtrado, asociado con bosques de galería y sustrato de suelo húmedo suelto con hojarasca.

Comparison of gastropod mollusc (Apogastropoda: Hydrobiidae) habitats in two crater lakes in Nicaragua

The aquatic gastropod mollusc, Pyrgophorus coronatus, may perform an important role in the transmission of an emergent ocular pathology among fishes in Lake Apoyo, Nicaragua. This disease emerged after an introduction of tilapia (Oreochromis niloticus) and the subsequent loss of Chara sp. beds in the lake. We compared the mollusc population densities in three habitats (sandy/muddy substrates, rocks, and Chara vegetation) at varying depths (1.5, 10, 20, and 30 m) in two volcanic crater lakes in Nicaragua: Lake Apoyo and Lake Xiloa. where lower numbers of affected fishes were found and tilapia has not been introduced. Duplicate samples at 1.5 m depth were taken in each habitat monthly for a year, and triplicate samples for bathymetric analysis of snail populations were performed during August, 2005. Samples of fixed surface area were filtered in a 0.4 cm size screen and live snails were counted from each sample. The preferred snail habitat in both lakes, Chara beds, was vastly reduced in Lake Apoyo via consumption by introduced Nile tilapia (Oreochromis niloticus). Structureless sandy substrates (mean +/- standard error 3.1+/-1.3 ind/m2) had lower population densities than other habitats in Lake Xiloa (rocks 590.9+/-185.3 ind/m2; vegetation 3 686.5+/-698.2 ind/m2; ANOVA 1, p<0.01 in both cases) but this difference was attenuated in Lake Apoyo (sand 384.4+/-111.1 ind/m2; rocks 1 480.4+/-384.8 ind/m2: 0.0 1

El gasterópodo acuático, Pyrgophorus coronatus, podría jugar un papel importante en la transmisión de una patología ocular emergente entre los peces de la laguna de Apoyo, Nicaragua. Esta enfermedad surgió después de una introducción de tilapia (Oreochromis niloticus) y la subsecuente pérdida de lechos de Chara sp. en la laguna. Comparamos las densidades poblacionales del caracol en tres hábitats (substratos arenosos/lodosos, rocas y vegetación de Chara) en dos lagunas cratéricas volcánicas en Nicaragua: La laguna de Apoyo y la laguna de Xiloá, donde no se encuentraron grandes cantidades de peces afectados y donde no se han introducido tilapias. Mensualmente, por un año tomamos muestras duplicadas a 1.5 m profundidad mensualmente por un año, y durante agosto de 2005, muestreos triplicados de las poblaciones del molusco, para análisis batimétrico (1.5, 10, 20 y 30 m). Para determinar el número de individuos por unidad de área superficial, las muestras fueron filtradas en un colador de 0.4 cm de apertura de malla y contamos los moluscos vivos en cada muestra. El hábitat preferido de los caracoles en ambas lagunas fue la vegetación de Chara, que en la laguna de Apoyo fue vastamente reducida al ser consumida por las tilapias nilóticas introducidas (Oreochromis niloticus). Los substratos arenosos, menos estructurados que los otros sustratos estudiados, tuvieron densidades poblacionales más bajas (media ± error estándar 3.1±1.3 ind/m2) que en los otros hábitats en la laguna de Xiloá (vegetation 590.9±185.3 ind/m2; rocas 3 686.5±698.2 ind/m2; ANOVA I, p<0.01 en ambos casos) pero esta diferencia fue atenuada en la laguna de Apoyo (arena 384.4±111.1 ind/m2; rocas 1 480.4±384.8 ind/ m2; 0.01

Microhabitat use by two rocky shore gastropods in an intertidal sandy substrate with rocky fragments

Praias arenosas em algumas partes do Canal São Sebastião, região sudeste do Brasil, têm sido constantemente submetidas a diferentes tipos de impacto como deposição de fragmentos rochosos na região entremarés. Como conseqüência, estes ambientes abrigam uma rica fauna com organismos tanto de costões rochosos quanto de praias arenosas. Em especial, duas espécies de gastrópode típicas de costões rochosos, Tegula viridula e Morula nodulosa, são muito abundantes nestes ambientes. Uma avaliação do uso de microhabitats por estas duas espécies revelou que elas ocupam os microhabitats disponíveis em diferentes proporções e que a presença de uma espécie esteve associada à ausência da outra. Morula nodulosa apresentou uma dispersão ao acaso ocupando áreas com sedimento e algas marrons ramificadas recobrindo os fragmentos de rocha. Tegula viridula apresentou uma dispersão agrupada associada à característica agrupada dos microambientes ocupados: presença de algas verdes incrustantes e ausência de sedimento e algas marrons ramificadas recobrindo os fragmentos de rocha. Os resultados indicam que T. viridula pode ser menos tolerante que M. nodulosa à inundação dos fragmentos rochosos por sedimento, um evento estocástico comum ao ambiente estudado.