Residency of bull sharks, Carcharhinus leucas (Carcharhiniformes: Carcharhinidae), at San Pedrillo Islet in Islas Murciélago, North Pacific of Costa Rica / Residencia del tiburón toro, Carcharhinus leucas, (Carcharhiniformes: Carcharhinidae) en el islote de San Pedrillo, Islas Murciélago, Pacífico Norte de Costa Rica

Introduction: The bull shark, Carcharhinus leucas, is particularly vulnerable to anthropogenic actions because of its permanence in coastal ecosystems; populations depletion is registered in different places around the world. Aggregations of bull sharks have been reported in the North Pacific of Costa Rica, at Islas Murciélago, within the Guanacaste Conservation Area. Objective: To study the residency of bull sharks at San Pedrillo islet, Islas Murciélago. Methods: During the study period (June 2013 to February 2015) we used passive telemetry to tag 10 bull sharks. Results: All the sharks tagged were females, they were detected on 59 798 occasions by the acoustic receiver deployed in San Pedrillo. Acoustic signals from tagged sharks were received for a total period of 1 to 229 days (mean = 73.9 ± 71.3 days), with the last detections occurring on 9 January 2015. The Residency Index for each tagged shark across the entire monitoring period ranged from 0.41 to 1.00. The bull shark activity showed a significant pattern throughout the day at the receiver that specifically corresponded with the daily light cycle. Conclusions: This study concludes that San Pedrillo is an aggregation site (cleaning station) for bull sharks (C. leucas), possibly related to reproduction and not feeding behaviors.

Introducción: El tiburón toro (Carcharhinus leucas) es una especie tropical y subtropical que habita ríos, estuarios y aguas costeras. Objetivo: Estudiar la residencia del tiburón toro en San Perdillo, Islas Murciélago, Área de Conservación Guanacaste. Métodos: Durante el período de estudio (junio de 2013 a febrero de 2015) se marcaron 10 tiburones toro con telemetría acústica en San Pedrillo. Resultados: Los tiburones marcados fueron todos hembras y fueron detectados en 59 798 ocasiones por el receptor acústico desplegado en San Pedrillo. Las señales acústicas de los tiburones marcados se recibieron durante un período total de 1 a 229 días (media = 73.9 ± 71.3 días), y las últimas detecciones ocurrieron el 9 de enero de 2015. El índice de residencia de cada tiburón marcado durante todo el período de seguimiento osciló entre 0.41 y 1.00. La actividad del tiburón toro mostró un patrón significativo a lo largo del día en el receptor que se corresponde específicamente con el ciclo de luz diario. Conclusiones: Este estudio concluyó que San Pedrillo es un sitio de agregación (estación de limpieza) para el tiburón toro, posiblemente relacionado con comportamientos de reproducción y no de alimentación; y es un sitio crítico para la especie. Se necesitan más estudios para identificar áreas de alimentación y cría en el Área de Conservación de Guanacaste y áreas circundantes.

Age and growth of the smalleye smooth-hound shark, Mustelus higmani (Carcharhiniformes: Triakidae) from the Venezuelan Caribbean / Edad y crecimiento del tiburón, Mustelus higmani (Carcharhiniformes: Triakidae) de Venezuela

Introduction: Mustelus higmani is one of the shark species most commonly caught in the Northeastern region of Venezuela; however, this species has been poorly studied. Objective: To evaluate the age and growth of M. higmani on the basis of the optical analysis of vertebrae. Methods: Between August 2016 and July 2017, the vertebral samples were collected in the fishing port of Juan Griego, Margarita Island. The growth study was based on a sample of 238 individuals, 86 males (24.1-59.5 cm TL) and 152 females (24.4-69.5 cm TL) and the use of VBGF modeling approach. Results: The RMI analysis suggested an annual periodicity for the deposition of growth rings. Ages assigned varied between 0 and 5 years in males, and between 0 and 6 years in females. The estimates of VBGF parameters were L ¥ = 60.4 cm TL, k = 0.53 years-1 and t 0 = -1.02 years in males; and L ¥ = 71.1 cm TL, k = 0.38 years-1 and t 0 = -1.17 years in females. The ages at maturity and longevities resulted respectively in 2.6 and 6.6 years for males; and in 2.1 and 9.0 years for females. Conclusions: In general, results indicate that M. higmani has a rapid growth, early maturity, short longevity, and annual reproductive cycle, characterizing it as a biologically productive species.

Introducción: Mustelushigmani es una de las especies de tiburones más comúnmente capturadas en el nororiente de Venezuela; sin embargo, ha sido poco estudiada. Objetivo: Examinar la edad y crecimiento de M. higmani con base en el análisis óptico de las vértebras. Métodos: Entre agosto 2016 y julio 2017, se recolectaron muestras de vertebras en el puerto pesquero de Juan Griego, Isla de Margarita. La asignación de las edades se realizó con base en 238 ejemplares, 86 machos (24.1-59.5 cm LT) y 152 hembras (24.4-69.5 cm LT). Resultados: El análisis de RMI sugiere una periodicidad anual en la formación de los anillos de crecimiento. Las edades estuvieron comprendidas entre 0 y 5 años en los machos, y entre 0 y 6 años en las hembras. A su vez, los valores de los parámetros VBGF fueron L ¥ = 60.4 cm LT, k = 0.53 años-1 y t 0 = -1.02 años en los machos, y L ¥ = 71.1 cm LT, k = 0.38 años-1 y t 0 = -1.17 años en las hembras. Las edades medias de madurez y las longevidades resultaron respectivamente en 2.6 y 6.6 años para los machos, y en 2.1 y 9.0 años para las hembras. Conclusiones: En general los resultados indican que M. higmani presenta un crecimiento rápido, madurez temprana, corta longevidad y ciclo reproductivo anual, caracterizándola como una especie productiva desde el punto de vista biológico.

Large-scale migration of a school shark, Galeorhinus galeus, in the Southwestern Atlantic

Knowledge of the spatial and temporal distribution patterns of chondrichthyans is critical for their effective management. In this study we report and analyze a large-scale latitudinal migration (~ 1,425 km) of a female school shark in the Southwestern Atlantic shelf where it is currently classified as Critically Endangered. During the austral summer (February 15, 2015), ninety-four school sharks were captured (75 females and 19 males) and tagged with fin tags in Nuevo Gulf (~ 42°43'S, 64°53'W, Argentina). A female of 112 cm total length was recaptured in Uruguayan shelf waters in the austral winter (August 17, 2015). This long displacement represents the first direct evidence to support Vooren and Lucifora's hypothesis of a single transnational population of Galeorhinus galeus in the Southwestern Atlantic. The good agreement found between the school shark habitat conditions (salinity 33-34, temperature 12-17°C) and the warmer member of Subantarctic Shelf Waters suggests that the seasonal variation in school shark abundance within this region could be related to water masses movements.(AU)

El conocimiento sobre los patrones de distribución espacio-temporal de los condrictios es crítico para su manejo efectivo. En este trabajo presentamos y analizamos una migración latitudinal de gran escala (~ 1.425 km) de una hembra de cazón en la plataforma del Océano Atlántico Sudoccidental, donde está actualmente clasificada como Críticamente en Peligro. Durante el verano austral (15 de Febrero de 2015), 94 cazones fueron capturados (75 hembras y 19 machos) y señalados con marcas "rotatag" en el Golfo Nuevo (~ 42°43'S, 64°53'W, Argentina). Una hembra de 112 cm de longitud total fue recapturada en aguas de la plataforma uruguaya durante el invierno austral (17 de Agosto de 2015). Este gran desplazamiento representa la primera evidencia directa para apoyar la hipótesis de Vooren y Lucifora sobre una única población transnacional de Galeorhinus galeus en el Océano Atlántico Sudoccidental. La gran coincidencia encontrada entre las condiciones de hábitat para el cazón (salinidad 33-34, temperatura 12-17° C) y el integrante más cálido del Agua de Plataforma Subantártica sugiere que la variación estacional en la abundancia del cazón dentro de esta región podría estar relacionada con el movimiento de las masas de agua.(AU)

Are whale sharks exposed to persistent organic pollutants and plastic pollution in the Gulf of California (Mexico)? First ecotoxicological investigation using skin biopsies.

The whale shark (Rhincodon typus) is an endangered species that may be exposed to micro- and macro-plastic ingestion as a result of their filter-feeding activity, particularly on the sea surface. In this pilot project we perform the first ecotoxicological investigation on whale sharks sampled in the Gulf of California exploring the potential interaction of this species with plastic debris (macro-, micro-plastics and related sorbed contaminants). Due to the difficulty in obtaining stranded specimens of this endangered species, an indirect approach, by skin biopsies was used for the evaluation of the whale shark ecotoxicological status. The levels of organochlorine compounds (PCBs, DDTs), polybrominated diphenyl ethers (PBDEs) plastic additives, and related biomarkers responses (CYP1A) were investigated for the first time in the whale shark. Twelve whale shark skin biopsy samples were collected in January 2014 in La Paz Bay (BCS, Mexico) and a preliminary investigation on microplastic concentration and polymer composition was also carried out in seawater samples from the same area. The average abundance pattern for the target contaminants was PCBs>DDTs>PBDEs>HCB. Mean concentration values of 8.42ng/g w.w. were found for PCBs, 1.31ng/g w.w. for DDTs, 0.29ng/g w.w. for PBDEs and 0.19ng/g w.w. for HCB. CYP1A-like protein was detected, for the first time, in whale shark skin samples. First data on the average density of microplastics in the superficial zooplankton/microplastic samples showed values ranging from 0.00items/m3 to 0.14items/m3. A focused PCA analysis was performed to evaluate a possible correlation among the size of the whale sharks, contaminants and CYP1A reponses. Further ecotoxicological investigation on whale shark skin biopsies will be carried out for a worldwide ecotoxicological risk assessment of this endangerd species.

Fishers' ecological knowledge of smalleye hammerhead, Sphyrna tudes, in a tropical estuary

Coastal hammerheads have suffered from overexploitation and environmental degradation. We interviewed 79 artisanal fishers to verify fishery aspects, temporal changes in catches and biological aspects of the smalleye hammerhead, Sphyrna tudes , in a marine protected area on Abrolhos Bank, Brazil. Data were compared between three generations of fishers: young, middle-aged and old. Fishers' age varied between 17 and 88 years. We verified significant reductions in the weight of individuals caught by younger fishers. The main types of fishing gear used to catch S. tudes were gill nets and longlines. Overfishing through gill nets and trawl fisheries were mentioned as the cause of S. tudes population collapse in the region. The shark's diet as reported by fishers consisted of fish, crab and shrimp; austral summer was the reproductive season. A strong similarity was verified between fishers' knowledge and biological data. We suggest as plausible strategies to conserve the local population of S. tudes the reduction of net fisheries impact through zoning and establishment of no take areas. These steps can help to initiate the recovery of this depleted species.

Tubarões martelo costeiros têm sofrido com a sobrepesca e degradação ambiental. Foram entrevistados 79 pescadores artesanais para verificar aspectos da pesca, mudanças temporais nas capturas e aspectos biológicos de Sphyrna tudes em uma área marinha protegida no Banco dos Abrolhos, Brasil. Os dados foram comparados entre três gerações de pescadores: novos, meia idade e mais velhos. A idade dos pescadores variou entre 17 e 88 anos. Verificaram-se reduções significativas no peso dos indivíduos capturados pelos pescadores mais jovens. Os principais petrechos usados para captura de S. tudes foram redes de emalhe e espinhel. Pescadores mencionaram que o colapso da população local de S. tudes foi decorrente do excessivo uso de redes de emalhe e pelas pescarias de arrasto. A dieta reportada foi peixes, caranguejos e camarões e a época de reprodução foi o verão. Uma forte similaridade foi verificada entre o conhecimento dos pescadores e dados biológicos. São sugeridas como estratégias plausíveis para conservar a população local de S. tudes a redução do esforço das pescas com rede através de zoneamento e estabelecimento de áreas de exclusão de pesca. Esses passos podem ajudar a iniciar a recuperação de espécies depletadas.

Zoogeography of Elasmobranchs in the Colombian Pacific Ocean and Caribbean Sea

Para conocer los patrones zoogeográficos de los elasmobranquios marinos de Colombia, la riqueza de especies de Pacífico y Caribe y sus subáreas (Pacífico costero, Pacífico oceánico, Caribe costero y Caribe oceánico) fue analizada. Las áreas compartieron 10 familias, 10 géneros y 16 especies de tiburones y ocho familias, tres géneros y cuatro especies de batoideos. Carcharhinidae tuvo la mayor contribución a la riqueza de tiburones mientras que Rajidae y Urotrygonidae tuvieron la mayor contribución a la riqueza de batoideos en el Caribe y el Pacífico, respectivamente. La mayoría de los elasmobranquios estuvieron asociados con hábitats bénticos y costeros. El análisis de similitud permitió la identificación de cinco grupos de familias que caracterizan la riqueza de elasmobranquios en ambas áreas. La diversidad beta indicó que el mayor recambio de especies se produjo entre el Pacífico costero y las dos subáreas del Caribe. La diferencia en la riqueza y composición de especies entre las áreas puede ser debida a eventos vicariantes tales como el surgimiento del Istmo de Panamá. Es poco probable que la diversidad de elasmobranquios en Colombia se originara de un único evento de colonización. Eventos locales de diversificación/especiación, dispersión desde las regiones templadas de América, del Pacífico y del Atlántico son orígenes posibles que no se excluyen entre sí.

In order to investigate zoogeographical patterns of the marine elasmobranch species of Colombia, species richness of the Pacific and Caribbean and their subareas (Coastal Pacific, Oceanic Pacific, Coastal Caribbean, Oceanic Caribbean) was analyzed. The areas shared 10 families, 10 genera and 16 species of sharks, and eight families, three genera and four species of batoids. Carcharhinidae had the highest contribution to shark richness, whereas Rajidae and Urotrygonidae had the greatest contribution to batoid richness in the Caribbean and Pacific, respectively. Most elasmobranchs were associated with benthic and coastal habitats. The similarity analysis allowed the identification of five groups of families, which characterize the elasmobranch richness in both areas. Beta diversity indicated that most species turnover occurred between the Coastal Pacific and the two Caribbean subareas. The difference in species richness and composition between areas may be due to vicariant events such as the emergence of the Isthmus of Panama. It is unlikely that the Colombian elasmobranch diversity originated from a single colonization event. Local diversification/speciation, dispersal from the non-tropical regions of the Americas, a Pacific dispersion and an Atlantic dispersion are origin possibilities without any of them excluding the others.

Androgen receptors in the bonnethead, Sphyrna tiburo: cDNA cloning and tissue-specific expression in the male reproductive tract.

As demonstrated in past studies, androgens appear to play critical roles in regulating reproduction in male sharks. However, little is known about the cell-specific actions of androgens in these fishes. To address this, this study examined androgen targets in reproductive organs of a seasonally reproducing shark, the bonnethead (Sphyrna tiburo). A partial bonnethead AR cDNA clone was isolated and found to exhibit strong homology with known vertebrate ARs. Using RT-PCR and in situ hybridization, AR was found to be expressed in multiple cell types in the male bonnethead testis (premeiotic germ cells, Leydig-like interstitial cells, Sertoli cells, peritubular myoid cells, and mature spermatozoa) and gonadal ducts (stromal cells, luminal epithelial cells, mature spermatozoa). Furthermore, AR expression in these organs was found to vary temporally in relation to the seasonal reproductive cycle. Based on immunocytochemistry, the presence of AR protein in male bonnethead reproductive organs was largely consistent with patterns of AR gene expression with the single exception of mature spermatozoa, which exhibited consistently strong mRNA expression but only inconsistent and weak AR protein immunoreactivity. These results suggest important roles for androgens in regulating germ cell proliferation, hormone production, spermatid elongation, spermiation, and gonadal duct function in male bonnetheads. In addition, high abundance of AR mRNA in bonnethead spermatozoa suggest the potential for de novo protein synthesis following spermiation/copulation and/or a role for AR mRNA in early embryonic development, both of which have been proposed to explain the occurrence of mRNA transcripts in spermatozoa from various vertebrates.

Agregaciones de alimentación del tiburón ballena, Rhincodon typus (Orectolobiformes: Rhincodontidae) en Golfo Dulce, Península de Osa, Costa Rica / Whale shark, Rhincodon typus (Orectolobifoms: Rhincodontidae) feeding aggregations in Golfo Dulce, Osa Peninsula, Costa Rica

Resumen El tiburón ballena (Rhincodon typus), es el condrictio viviente más grande del mundo, con una distribución cosmopolita, encontrándose tanto en mares tropicales como subtropicales. La Unión Mundial para la Conservación (IUCN) lo clasifico como vulnerable y con una tendencia poblacional en disminución, conocido por realizar grandes agregaciones alrededor del mundo, relacionadas a procesos oceanográficos que incrementan la productividad primaria del ambiente marino. Por primera vez, se reporta cuatro eventos de alimentación de tiburón ballena dentro de la cuenca interna de Golfo Dulce, un fiordo tropical ubicado en la costa del Pacífico Sur de Costa Rica. Los avistamientos fueron realizados en enero y agosto del 2009, marzo 2012 y enero del 2013, donde la estructura y tamaño de los grupos se mantuvo constante en el tiempo encontrándose una proporción similar de adultos y juveniles. Estas agregaciones fueron observadas en la costa occidental de Golfo Dulce en un área que abarcaba los 23km, cerca de los ríos Rincón y Tigre, siendo estos los responsables de una alta concentración de nutrientes que favorecen la presencia de comunidades planctónicas. Durante las agregaciones se observó la presencia de zooplancton en la columna de agua, copépodos (Orden: Calanoidea). Dada la vulnerabilidad del tiburón ballena, es de suma importancia la implementación de estrategias de manejo de las actividades antropogénicas que se desarrollan en el Golfo, como son las actividades turísticas, desarrollo costero, aumento del tráfico marítimo, y la pesca comercial y deportiva, que ponen en riesgo a esta especie bandera.

Abstract The zooplanktivorous whale shark (Rhincodon typus), is the largest living chondrichthyan and a cosmopolitan species, living in tropical, warm and temperate waters. It is considered vulnerable by the International Union for Conservation of Nature (IUCN), and is known for big aggregations in many parts of the world. These are associated with particular oceanographic features where primary productivity is thought to be high. For the first time, four whale shark feeding aggregations are documented in Golfo Dulce, Costa Rica, a tropical fjord-like embayment located in the south Pacific region of the country. Observations were made in January and August 2009, March 2012 and in January 2013, Estimated group structure and size remained constant over time with an equal proportion of adults and juveniles in the same area. These aggregations were observed on the north-western coast of Golfo Dulce's inner basin, close to the Rincón and Tigre rivers. These two rivers are known to provide organic material which area important nutrients for the gulf zooplanktonic communities. During one of the observed feeding aggregations, copepods (Order: Calanoida) were seen in the water close to feeding individuals. Given the vulnerability of whale sharks, management decisions for Golfo Dulce need to include strategies to control tourism, boat circulation, commercial and sports fisheries and coastal development. Rev. Biol. Trop. 63 (Suppl. 1): 299-306. Epub 2015 April 01.

Development and characterization of a cell line WAF from freshwater shark Wallago attu.

A new epithelial cell line, WAF was developed from caudal fin of freshwater shark, Wallago attu. The cell line was optimally maintained at 28 °C in Leibovitz-15 (L-15) medium supplemented with 20 % fetal bovine serum. The cell line was characterized by various cytogenetic and molecular markers. The cytogenetic analysis revealed a diploid count of 86 chromosomes at different passages. The origin of the cell lines was confirmed by the amplification of 547 and 654 bp sequences of 16S rRNA and cytochrome oxidase subunit I genes of mitochondrial DNA, respectively. WAF cells were characterized for their growth characteristics at different temperature and serum concentration. Epithelial morphology of the cell line was confirmed using immunocytochemistry. Further cell plating efficiency, transfection efficiency and viability of cryopreserved WAF cells was also determined. Cytotoxicity and genotoxicity assessment of cadmium salts on WAF cells by MTT, NR and comet assay illustrated the utility of this cell line as an in vitro model for aquatic toxicological studies. The cell line will be further useful for studying oxidative stress markers against aquatic pollutants.

Chronotopographical distribution patterns of cell death and of lectin-positive macrophages/microglial cells during the visual system ontogeny of the small-spotted catshark Scyliorhinus canicula.

The patterns of distribution of TUNEL-positive bodies and of lectin-positive phagocytes were investigated in the developing visual system of the small-spotted catshark Scyliorhinus canicula, from the optic vesicle stage to adulthood. During early stages of development, TUNEL-staining was mainly found in the protruding dorsal part of the optic cup and in the presumptive optic chiasm. Furthermore, TUNEL-positive bodies were also detected during detachment of the embryonic lens. Coinciding with the developmental period during which ganglion cells began to differentiate, an area of programmed cell death occurred in the distal optic stalk and in the retinal pigment epithelium that surrounds the optic nerve head. The topographical distribution of TUNEL-positive bodies in the differentiating retina recapitulated the sequence of maturation of the various layers and cell types following a vitreal-to-scleral gradient. Lectin-positive cells apparently entered the retina by the optic nerve head when the retinal layering was almost complete. As development proceeded, these labelled cells migrated parallel to the axon fascicles of the optic fiber layer and then reached more external layers by radial migration. In the mature retina, lectin-positive cells were confined to the optic fiber layer, ganglion cell layer and inner plexiform layer. No evident correlation was found between the chronotopographical pattern of distribution of TUNEL-positive bodies and the pattern of distribution of lectin-labelled macrophages/microglial cells during the shark's visual system ontogeny.

Age and growth of the Scalloped Hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834), from the southern Brazilian coast / Idade e crescimento do tubarão-martelo-entalhado, Sphyrna lewini (Griffith and Smith, 1834), da costa sul do Brasil

Age and growth studies for the scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834) caught along the southern Brazilian coast, were based on ring measurements of vertebrae sections of 115 males, 116 females and 14 unknown sexed sharks between 48 and 344 cm total length (TL). The von Bertalanffy growth models were best fit using back-calculated data. The growth parameters obtained for males, were L∞ = 266 cm; K = 0.05/year; L0 = 47 cm. For females, L∞ = 300 cm; K = 0.05/year; L0 = 51 cm. An adult female reached 217 cm TL and was 31.5 years old. On the other hand, an adult male was 29.5 years old and measured 234 cm TL. Longevity estimate for males and females was 55 years. Therefore, S. lewini is a long-lived fish. Ageing precision, based on the IAPE index, was 5.6 percent. Marginal Increment analysis based on MIR index from hammerheads smaller than 105 cm, compared with the percentual of opaque and hyaline bands found per month ageing whole vertebrae, showed an annual ring formation, i.e., in winter.

O estudo da idade e do crescimento do tubarão-martelo-entalhado, Sphyrna lewini (Griffith and Smith, 1834), na costa sul do Brasil, baseou-se na leitura de anéis em seções de vértebras de 115 machos, 116 fêmeas e de 14 exemplares com sexo indeterminado, com comprimentos totais (CT) entre 48 e 344 cm. Modelos de crescimento de von Bertalanffy foram mais bem ajustados aos dados de idade e comprimento retrocalculados, considerando sexos em separado. Os parâmetros de crescimento obtidos para os machos foram L_∞ = 266 cm; K = 0,05/ano; L₀ = 47 cm. Para as fêmeas L_∞ = 300 cm; K = 0,05/ano; L₀ = 51 cm. Uma fêmea adulta atingiu um CT de 217 cm e uma idade de 31,5 anos. Por sua vez, um macho adulto tinha 29,5 anos e CT de 234 cm. A estimativa de longevidade para machos e fêmeas foi de 55 anos. O índice de erro percentual médio (IAPE), que avalia a precisão na leitura de idades, foi de 5,6 por cento. A análise do incremento marginal baseada no índice MIR e aplicada em tubarões com CT < 105 cm, comparada com o percentual de bandas opacas e hialinas mensais, obtido através de leituras de vértebras inteiras, indicou um padrão anual na formação dos anéis, ou seja, anéis de inverno.

Population size and survivorship for juvenile lemon sharks (Negaprion brevirostris) on their nursery grounds at a marine protected area in Brazil

Sharks face a number of obstacles for surviving their first several years of life and many species occupy nursery areas. Although estimates of survival, particularly for young age classes, are essential for assessing, monitoring and effectively managing animal populations, there have been relatively few calculations of survival within shark populations and even fewer estimates based on direct methods for sharks on their nursery grounds. We used tag-recapture methods to estimate the population size and survival of juvenile lemon sharks (Negaprion brevirostris) on their nursery grounds at Atol das Rocas, a marine protected area in Brazil. Sharks were sampled from 1999 to 2003. Population size estimates ranged from 12 to 100 juvenile sharks and survival estimates ranged between 24-54% with a mean of 44.6% over the most robust sampling periods. The population of juvenile lemon sharks declined over the course of our study, whereas survival rates may have increased over the same time period. Even a modest level of fishing and removal of mature females in adjacent areas may dramatically affect small populations of sharks within a small and isolated nursery such as Atol das Rocas. The lower survival rates and population size at Atol das Rocas could be the result of differences in physical characteristics of this nursery in comparison to others used by lemon sharks in the northwestern Atlantic. Such comparatively lower populational parameters suggest that the population of young lemon sharks is fragile at the Atol das Rocas nursery.

Os tubarões enfrentam muitos obstáculos para sobreviver nos primeiros anos de vida e muitas espécies ocupam áreas de berçário. Embora estimativas de sobrevivência, particularmente para jovens, sejam essenciais para acessar, monitorar e manejar efetivamente populações animais, existem poucos cálculos destas estimativas para populações de tubarões e poucas estimativas baseadas em métodos diretos para estes animais em suas áreas de berçário. Métodos de marcação e recaptura foram utilizadosno presente estudo para estimar o tamanho populacional e a sobrevivência de jovens tubarões-limão (Negaprion brevirostris) em uma área de berçário na Reserva Biológica do Atol das Rocas, Brasil. Os indivíduos foram amostrados entre 1999 e 2003 e as estimativas de tamanho populacional variaram entre 12 a 100 indivíduos jovens e a taxa de sobrevivência entre 24 e 54%, com média de 44,6% durante o período de amostragem mais robusto. A população destes tubarões jovens diminuiu ao longo de nosso estudo, ainda que as taxas de sobrevivência tenham aumentado durante o mesmo período. Mesmo um nível moderado de pesca e a remoção de fêmeas maduras em áreas adjacentes podem afetar dramaticamente pequenas populações de tubarões num berçário pequeno e isolado como o Atol das Rocas. As taxas de sobrevivência e tamanho populacional relativamente mais baixos em Rocas podem ser resultado das diferenças nas características físicas deste berçário, comparadas a outros utilizados pela espécie no Atlântico norte-ocidental. Tais parâmetros comparativamente mais baixos no Atol das Rocas sugerem a fragilidade da população jovem de tubarões-limão neste berçário.

Hábitos alimentares de tubarões-martelo jovens, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), no litoral sul do Brasil / Feeding habits of young smooth hammerhead sharks, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), in the Southern Coast of Brazil

O presente estudo foi conduzido em duas comunidades da pesca artesanal nas cidades Guaratuba (Paraná) e Itapoá (Santa Catarina), no sul da costa brasileira. Os conteúdos estomacais de indivíduos Sphyrna zygaena foram identificados, sendo os itens alimentares agrupados em três categorias. As categorias mais importantes foram teleósteos (78,6 por cento) e cefalópodes (60,7 por cento), representados pela sardinha Harengula clupeola e a lula Loligo sp., ambos considerados como principais itens alimentares de S. zygaena na região estudada.

The present study was conducted in two artisan fishing communities in the cities Guaratuba (Paraná) and Itapoá (Santa Catarina), in the South Brazilian coast. Stomach contents of Sphyrna zygaena specimens were identified, showing three categories of food items. The most important feeding categories were teleosts (78.6 percent) and cephalopods (60.7 percent), represented by the sardine Harengula clupeola the squid Loligo sp., both considered the main food items of S. zygaena in the studied region.

Distribution and ontogeny of glucagon-like cells in the gastrointestinal tract of the cartilaginous fish Scyliorhinus stellaris (L.).

The ontogeny and distribution of glucagon-like cells were studied in the gastrointestinal tract of embryos, neonates, and adults of the cartilaginous fish Scyliorhinus stellaris (L.) by immunocytochemistry. The results indicate that they appear early during embryonic development, and, in some portion of the gastrointestinal tract, even before the mucosa morphological differentiation. Immunoreactive glucagon-like cells were observed both in gastric and intestinal epithelium, being present in the pyloric portion only at a particular period of its differentiation. Some differences were observed between the embryonic and adult distributive pattern. They were more numerous in proliferative zone and sometimes were situated near other endocrine epithelial cells. These findings together with available information on trophic effects of some gastrointestinal hormonal peptides suggest a possible regulatory role of this peptide on the growth and differentiation of the gastrointestinal tract.

Selachian tooth development: II. Immunolocalization of amelogenin polypeptides in epithelium during secretory amelogenesis in Squalus acanthias.

We have determined the distribution of amelogenin polypeptides in an order of elasmobranchs using indirect immunofluorescence with rabbit polyclonal antibodies prepared to purified murine amelogenins. We find that amelogenins are definitely present within the inner enamel epithelium prior to the production of the extracellular matrix component termed "enameloid" (row II developing tooth organs). During subsequent stages of selachian tooth development (row III tooth organs), immunofluorescence staining data indicated localization of amelogenin antigens within epithelium as well as the enameloid extracellular matrix. The results from these immunohistochemical studies suggest that the 16-20 kdalton amelogenins, which are characteristic of murine inner enamel epithelial cells undergoing terminal biochemical differentiation into secretory ameloblasts, may also be regarded as molecular markers for amelogenesis in developing teeth in the spiny dogfish, Squalus acanthias.