Aspectos reproductivos de la raya látigo Hypanus longus (Garman, 1880) de los desembarques de la pesca artesanal en el Pacífico de Guatemala / Reproductive aspects of the longtail stingray Hypanus longus (Garman, 1880) from the landings of the artisanal fishery in the Pacific of Guatemala

La raya látigo Hypanus longus, ha pasado de ser una especie de captura incidental a una especie objetivo en la pesca artesanal del Pacífico de Guatemala. Esta actividad es realizada sin considerar criterios biológicos esenciales para su aprovechamiento sostenible. Aunado a ello, H. longus es una especie sensible, presentando características biológicas como: madurez sexual tardía, ciclos reproductivos largos y baja fecundidad. El presente estudio contribuye al conocimiento de la biología reproductiva de la raya látigo. Durante mayo de 2019 a marzo de 2020 se realizaron 11 muestreos de los desembarques de la pesca artesanal en la comunidad de Sipacate, Escuintla, en cada muestreo se registró el ancho de disco (AD), el peso, sexo y estado de maduración sexual de H. longus. En total se registraron 336 organismos, que presentaron una proporción sexual de 1:1, un AD para hembras de M = 82.33 cm, DS = 22.24 y de M = 76.91 cm, DS = 11.86 para machos. A partir de las evaluaciones externas e internas de los aparatos reproductores se determinó la talla de madurez sexual (L50), siendo de 88.2 y 79.3 cm AD para hembras y machos respectivamente. Finalmente, este estudio evidencio que el 65.68% de hembras y el 52.10% de machos son capturados por debajo de la L50, por lo cual se recomienda elaborar e implementar estra-tegias o medidas tendientes a la regulación de las prácticas pesqueras o artes de pesca que permitan la captura de organismos mayores a 95 cm de AD.

The whip ray Hypanus longushas gone from being a bycatch species to a target species in artisanal fisheries in the Pacific of Guatemala. This activity is carried out without considering essential biological criteria for its sustainable use. In addition, H. longusis a sensitive species, presenting biological characteristics such as late sexual maturity, long reproductive cycles and low fecundity. The present study contributes to the knowledge of the reproductive biology of the whip ray. During May 2019 to March 2020, 11 samplings were conducted from artisanal fishery landings in the community of Sipacate, Escuintla, in each sampling the disc width (AD), weight, sex and sexual maturation stage of H. longus were recorded. A total of 336 organisms were recorded, which pre-sented a sex ratio of 1:1, with a female AD of M = 82.33 cm, SD = 22.24 and M = 76.91 cm, SD = 11.86 for males. From the external and internal evaluations of the reproductive apparatus, the size at sexual maturity (L50) was determined to be 88.2 and 79.3 cm AD for females and males, respectively. Finally, this study showed that 65.68% of females and 52.10% of males are caught below L50, so it is recommended to develop and implement strategies or measures to regulate fishing practices or fishing gear that allow the capture of organisms larger than 95 cm AD.

Diversity of white spot patterns in the eagle ray Aetobatus laticeps (Myliobatiformes: Aetobatidae) in the north Pacific coast of Costa Rica / Diversidad de patrones de manchas blancas de Aetobatus laticeps (Myliobatiformes: Aetobatidae) en la costa del Pacífico Norte de Costa Rica

Introduction: The Pacific white-spotted eagle ray Aetobatus laticeps, has recently separated from the Atlantic A. narinari based on both morphological and genetic evidence. This species is characterized by a dark body with numerous white spots all over its dorsal side. Considering the type, shape, number, and distribution of these natural markings as potential identifiers at the individual level, we studied the variation in the spot patterns. Objective: Describe and compare the white spot pattern (type and distribution) of individuals and evaluate their potential use as identifiers at the individual level. Methods: We analyzed 54 videos (105 subsequent extracted photos) and 19 photographic records that were taken at different sites along the Pacific coast of northern Costa Rica. Results: Seventeen distinctive types of white spots were identified across the entire dorsal side of the rays. Significant differences between each major body section (pectoral fins, back, head, and pelvic fins) were found in the type and frequency of white spots. The type 'single spot' was commonly distributed across the entire dorsal side, and the spot pattern on the pelvic fins was informative to identify 72 individuals. Conclusions: The analysis of the type, shape, and distribution of white spots in A. laticeps determined several combinations of white spot patterns that be used for further taxonomic description and provide potential identification of the individual for future population studies along with its distribution.

Introducción: La raya águila de manchas blancas del Pacífico, Aetobatus laticeps, se ha separado recientemente de A. narinari del Atlántico basándose en pruebas tanto morfológicas como genéticas. Esta especie se caracteriza por un cuerpo oscuro con numerosas manchas blancas en toda su parte dorsal. Considerando el tipo, la forma, el número y la distribución de estas marcas naturales como identificadores potenciales a nivel individual, estudiamos la variación en los patrones de manchas. Objetivo: Describir y comparar el patrón de manchas blancas (tipo y distribución) de individuos y evaluar su uso potencial como identificadores a nivel individual en especímenes recapturados. Métodos: Analizamos 54 videos (con 105 fotografías extraídas posteriormente) y 19 registros fotográficos que fueron tomados en diferentes sitios a lo largo de la costa pacífica del norte de Costa Rica. Resultados: Se identificaron diecisiete tipos distintivos de manchas blancas en todo el lado dorsal de los radios. Se encontraron diferencias significativas entre cada sección principal del cuerpo (aletas pectorales, espalda, cabeza y aletas pélvicas) en el tipo y frecuencia de manchas blancas. El tipo 'punto único' se distribuyó comúnmente en todo el lado dorsal, y el patrón de puntos en las aletas pélvicas fue informativo para identificar 72 individuos. Conclusiones: El análisis del tipo, la forma y la distribución de las manchas blancas en A. laticeps determinó varias combinaciones de patrones de manchas blancas que se utilizarán para una descripción taxonómica adicional y brindan una identificación potencial del individuo para futuros estudios de población a lo largo de su distribución.

Redescription of the Rio skate Rioraja agassizii (Rajiformes: Arhynchobatidae) with notes on internal anatomy and intraspecific variation

Rioraja agassizii belongs to the monotypic genus Rioraja and differs from the other Riorajini species of the genus Atlantoraja by the shape of anterior nasal flap, squamation, clasper skeleton, body measurements and color pattern. Although R. agassizii is a well-known species, commonly captured in inshore waters of the southwestern Atlantic, its external morphology and internal anatomy have never been fully described and little is known on intraspecific variation within the species. Juvenile and adult, male and female specimens were examined, measured and dissected. Herein, we redescribe the species and present detailed descriptions and illustrations of external morphology, neurocranium, jaws, hyoid and gill arches, and pelvic fin and girdle. Additionally, notes on sexual dimorphism and ontogenetic differences in coloration, body and cranial measurements, and dermal denticles are provided.(AU)

Rioraja agassizii pertence ao gênero monotípico Rioraja e difere das demais espécies da tribo Riorajini classificadas no gênero Atlantoraja pelo formato da aba nasal anterior, escamas, esqueleto do clásper, medidas corpóreas e padrão de coloração. Embora R. agassizii seja uma espécie bem conhecida, comumente capturada em águas costeiras do Atlântico Sul Ocidental, sua morfologia externa e anatomia interna não foram totalmente descritas e pouco se sabe sobre a variação intraespecífica nesta espécie. Espécimes juvenis, adultos, machos e fêmeas foram examinados, medidos e dissecados. Neste estudo, a espécie é redescrita e descrições detalhadas e ilustrações da morfologia externa, neurocrânio, maxilas, arcos hioide e branquiais, nadadeira e cintura pélvicas são apresentadas. Adicionalmente, notas sobre dimorfismo sexual e variação ontogenética na coloração, medidas corpóreas e craniais, e dentículos dérmicos são fornecidas.(AU)

Neuroanatomy of two species of genus Myliobatis (Chondrichthyes: Myliobatoidea) / Neuroanatomía de dos especies del género Myliobatis (Chondrichthyes: Myliobatoidea)

Several studies on the elasmobranchs neuroanatomy have shown that their brain is more complex than previously thought, and had significant intra and interspecific variations. The objective of this work was conducting a comparative encephalic neuroanatomy study of two species of genus Myliobatis. In total, 16 organisms of genera Myliobatis californica and Myliobatis longirostris, collected in the coasts of Kino Bay, Sonora, Mexico, were used. In Myliobatis, the brain has a long telencephalon and the posterior central nucleus is poorly developed. Their cerebellum is asymmetric, has several sulci, most of which are transversally oriented, with four lobes (anterior, medium and two posterior), a condition which has not been reported for any other species. It was observed that, despite the morphology of M. californica and M. longirostris is similar, there are some significant differences. Both species have moderate foliation, but M. californica has more sulci. In the diencephalon of M. californica, it was observed that the lobes of the infundibulum are oval-shaped and separated, while in M. longirostris, such lobes are rounded and near the medium line. It has to be highlighted that Myliobatis belongs to the most derived batoid group; nevertheless, its brain is considerably less complex, as compared to what has been reported for the most derived milyobatoids species.

Diversos estudios sobre la neuroanatomía de los elasmobranquios han demostrado que el cerebro es más complejo de lo que se pensaba y presenta considerables variaciones tanto intra como interespecíficas. El objetivo de este trabajo fue realizar un estudio de neuroanatomía comparada del encéfalo de dos especies del género Myliobatis. Se utilizaron un total de 16 organismos de Myliobatis californica y Myliobatis longirostris, los cuales fueron colectados en las costas de Bahía Kino, Son., México. El cerebro de Myliobatis tiene un telencéfalo largo, el núcleo central posterior está poco desarrollado; el cerebelo es asimétrico, presenta surcos que en su mayoría están orientados transversalmente, con cuatro lóbulos (anterior, medio y dos posteriores), condición que no ha sido reportada para otra especie. Se observó que, aunque M. californica y M. longirostris presentan una morfología similar existen ciertas diferencias. En ambas especies presentan una foliación moderada; sin embargo, en M. californica se observan más surcos. En el diencéfalo de M. californica se observa que los lóbulos del infundíbulo son ovalados y están separados, mientras que en M. longirostris son redondeados y se encuentran próximos a la línea media. Es importante señalar que, pese a que Myliobatis pertenece al grupo de batoideos más derivado, su cerebro es considerablemente menos complejo de lo que se ha reportado para las especies de miliobatoideos más derivadas.

Microscopic aspects of electrosensory system on the partially euryhaline lesser guitarfish

ABSTRACT The electrosensory system on elasmobranchs consists of subcutaneous electroreceptor organs known as ampullae of Lorenzini. The present study investigated the ampullae of Lorenzini morphology of the lesser guitarfish Zapteryx brevirostris, using light microscopy and scanning electron microscopy. The pore number found in the ventral skin surface is much higher than that found in the dorsal portion, characteristic of species that inhabit the euphotic zone. Under light microscopy it was possible to observe that the wall canal consists of a single layer of squamous epithelial cells. The canal features distal expansion, where the ampullae are located with up to six alveoli. The sensory epithelium of ampullae is composed by cubic cells, with oval nucleus, restricted to the interior of the alveoli. With analysis the clusters under scanning electron microscopy, it was possible to observe the structure and the random arrangement of individual ampullae, canals and nerves. The distribution of dorsal and ventral pores and ampullae in Z. brevirostris resembled those of the same family. The number of alveoli per ampullae was similar to that found in euryhaline elasmobranchs species, suggesting that the morphological organization in Z. brevirostris is linked to its possible evolutionary transitory position among batoids.

Skeleton anatomy of five species of Genus urotrygon (Chondrichthyes: Urotrygonidae) / Anatomía del esqueleto de cinco especies del género Urotrygon (Chondrichthyes: Urotrygonidae)

Skeleton of batoids has been important to outline kinship relations in this group. Therefore, the objective of this work is describing the anatomy of five species of genus Urotrygon. Skeleton of Urotrygonids displayed a common morphological pattern, with the following differences: 1) preorbital processes are reduced in Urotrygon nana and Urotrygon munda, and developed on all other species; 2) the first postorbital process is reduced in U. nana and U. munda; 3) the first hypobranchial cartilage is fragmented only in Urotrygon rogersi; 4) only Urotrygon aspidura had a bridge in the basibranchial cartilage; lateral processes of the synarcuale in U. aspidura are long and thin, while short and wide in U. nana and U. rogersi; 6) U. nana has only one single fenestra in its pectoral girdle, while other species have two; 7) In U. nana and U. munda the mesopterygium is rounded, but in all other species it is elongated in its anterior part; 8) U. nana y U. munda have a more arched pelvic girdle. Species with more plesiomorphic characters are U. nana and U. munda.

El esqueleto de los batoideos ha sido importante para establecer las relaciones de parentesco de este grupo. Es por ello que el objetivo del presente trabajo fue describir la anatomía de cinco especies del género Urotrygon. El esqueleto de las especies de urotrigonidos mostró un patrón morfológico común; sin embargo, se observaron las siguientes diferencias: 1) los procesos preorbitales están reducidos en Urotrygon nana y Urotrygon munda, en el resto de las especies están más desarrollados. 2) El primer proceso postorbital está reducido en U. nana y U. munda. 3) El primer cartílago hipobranquial se fragmenta únicamente en Urotrygon rogersi. 4) Solo en Urotrygon aspidura el cartílago basibranquial presentó un puente. 5) Los procesos laterales de la sinarcualia en U. aspidura son largos y delgados, mientras que en U. nana y U. rogersi son anchos y cortos. 6) En la cintura pectoral U. nana presenta una sola fenestra, en el resto de las especies hay dos. 7) En U. nana y U. munda el mesopterigio es redondeado, en el resto de las especies está alargado en su parte anterior. 8) La cintura pélvica está más arqueada en U. nana y U. munda. Las especies que presentaron los caracteres más plesiomórficos fueron U. nana y U. munda.

Anatomía comparada del neurocráneo y el encéfalo de la raya mariposa Gymnura micrura (Batoidea: Gymnuridae) / Comparative anatomy of the neurocranium and encephalon of the butterfly ray, Gymnura micrura (Batoidea: Gymnuridae)

Mediante la comparación del neurocráneo de la "raya mariposa" Gymnura micrura con especies representantes de cinco familias de Batoidea, se reconoce que corresponde al patrón anatómico del orden Myliobatiformes, por la ausencia del rostro, la presencia de una sola fontanela y el mayor desarrollo de los procesos postorbitarios. La especie en estudio difiere de los Urotrygonidae y Dasyatidae por tener los procesos postorbitarios subdivididos. La organización del encéfalo de G. micrura corresponde al patrón anatómico de los Batoidea, sin embargo, a diferencia de los Rhinobatidae, Urotrygonidae y Dasyatidae, el cerebelo es simétrico; en contraste con los Myliobatidae los hemisferios cerebrales son reducidos; y la principal diferencia con relación a los Narcinidae es la ausencia de los lóbulos eléctricos.

By comparing the neurocranium of the "butterfly ray" Gymnura micrura with representative species of five families of Batoidea, it is recognized that it corresponds to the anatomical pattern of the order Myliobatiformes, because of the absence of the rostrum, the presence of a single fontanelle and the development of the postorbital processes. The species under study differs from the Urotrygonidae and Dasyatidae by having subdivided postorbital processes. The organization of the encephalon of G. micrura corresponds to the anatomical pattern of the Batoidea. However, unlike the Rhinobatidae, Urotrygonidae, and Dasyatidae, the cerebellum is symmetrical; in contrast with the Myliobatidae, the cerebral hemispheres are reduced; and, the main difference in relation to the Narcinidae, is the absence of electrical lobes.

Nueva especie del género Urobatis (Myliobatiformes: Urotrygonidae) del Pacífico oriental tropical / A new species of Urobatis (Myliobatiformes: Urotrygonidae) from the tropical Eastern Pacific

A new species of round stingray, Urobatis pardalis sp. nov., is described from material collected in the Pacific coast of Costa Rica. This new species differs from its congeners by the color pattern of the dorsal surface and by several proportional measurements. A key to all species of the genus is provided.

Nueva especie del género Urobatis (Myliobatiformes: Urotrygonidae) del Pacífico oriental tropical. Una nueva especie de raya redonda con espina, Urobatis pardalis sp. nov., es descrita a partir de material recolectado en las costas del Pacífico de Costa Rica. Esta nueva especie difiere de sus congéneres por el patrón de la coloración dorsal del disco y por varias relaciones de medidas. Se presenta una clave para la determinación taxonómica de las especies del género.

The female reproductive system of Zearaja chilensis (Quichenot, 1848) (Chondrichthyes, Rajidae): gametogenesis and microscopic validation of maturity criteria / El sistema reproductor femenino de Zearaja chilensis (Quichenot, 1848) (Chondrichthyes, Rajidae): gametogénesis y validación microscópica de los criterios de madurez

Chondrichthyans are extremely susceptible to overfishing due, among other things, to their reproductive adaptations. Basic knowledge of reproductive parameters is essential, both of ecological and for economic points of view. Zearaja chilensis is a valuable economic resource in South America. This work analyzes the microanatomy of female reproductive system, as well as the size of the onset of vitellogenesis. The material was fixed in Bouin and processed using routine histological techniques. Both ovaries are equally functional. Folliculogenesis depicts the same pattern of other Chondrichthyans. Follicles with different degrees of maturation coexist in mature animals, with the exception of oogonia, which were only found in immature individuals. Likewise, atretic follicles were recorded in all stages of maturation. The size of yolk input, microscopically recorded, is lower than the detected at naked eye. Oviductal glands and uterus show similarity with those reported in other lecitotrophic cartilaginous fish. This work reports, for the first time, the morfofunctional microanatomy of the species, and puts to the test the accuracy of the commonly employed criteria for the determination of sexual maturity, a critical data when determining management policies.

Los condrictios son extremadamente susceptibles a la explotación pesquera debido, entre otras cosas, a sus adaptaciones reproductivas. Los conocimientos básicos de sus parámetros reproductivos son esenciales, ya sea desde el punto de vista ecológico como económico. Zearaja chilensis constituye un importante recurso económico en América del Sur. En este trabajo se analiza la anatomía microscópica del sistema reproductor femenino y la talla de inicio de la vitelogénesis. El material se fijó en Bouin y se procesó mediante técnicas histológicas de rutina. Ambos ovarios son igualmente funcionales. La foliculogénesis presenta el mismo patrón de otros condrictios. Los folículos con diferentes grados de maduración coexisten en animales maduros, con la excepción de las oogonias, que sólo se observaron en los individuos inmaduros. Los folículos atrésicos se registraron en todas las etapas de la maduración. La talla de inicio de la vitelogénesis, microscópicamente registrada, es inferior a la detectada en el ojo desnudo. La glándula oviductal y el útero muestran similitud con lo reportado en otros peces cartilaginosos lecitotróficos. Este trabajo describe por primera vez, la microanatomía morfofuncional de la especie y pone a prueba la precisión de los criterios comúnmente empleados para la determinación de la madurez sexual, una información crítica para la determinación de las políticas de gestión.

Estudio morfológico del cerebro y pares craneales de Diplobatis ommata (Elasmobranchii: Narcinidae) / Morphological study of the brain and cranial nerves of Diplobatis ommata (Elasmobranchii: Narcinidae)

El grupo de los Torpediniformes representa una de las líneas ancestrales de los batoideos cuya ruta evolutiva ha seguido una línea separada del resto de este grupo. No se han realizado estudios sobre la morfología del encéfalo de Diplobatis ommata, es por ello que el objetivo de este estudio fue describir la anatomía del encéfalo y pares craneales de esta especie. Los organismos fueron colectados en Zihuatanejo, Guerrero, México. El encéfalo se obtuvo por medio de la técnica de disección convencional. El encéfalo de Diplobatis ommata es similar al de los tiburones basales, sin embargo, presenta una vesícula eléctrica, característica de Torpediniformes. Las estructuras más grandes del encéfalo son los bulbos olfatorios y la médula oblongada. El telencéfalo es reducido y el cerebelo presenta simetría bilateral y es prácticamente liso. La disposición de los pares craneales es similar a la que presentan otros grupos de batoideos, sin embargo, la inervación de los pares craneales VII, IX y X se modifica, ya que además de inervar a las regiones descritas convencionalmente, inervan también a los órganos eléctricos.

The Torpediniformes group is one of the ancestral batoid lines, the evolution of which has followed a line separated from the rest of this group. No studies have been conducted on the brain morphology of Diplobatis ommata. This is why the objective of this work is describing the anatomy of the brain and the cranial nerves of this species. Organisms were collected in Zihuatanejo, Guerrero, Mexico. The brain was obtained through conventional dissection techniques. The brain of Diplobatis ommata is similar to that of basal sharks; however, it has the electric vesicle typical in Torpediniformes. The largest encephalic structures are the olfactory bulbs and medulla oblongata. The telencephalon is reduced, while the cerebellum has bilateral symmetry and is almost smooth. Disposition of cranial nerves are similar to other batoid groups; but innervation of pairs VII, IX and X is modified: they innervate regions conventionally described, but also electric organs.

Pesquería y biología de Rhinobatos percellens (Rajiformes: Rhinobatidae) capturados por la pesquería artesanal de playa La Pared, Venezuela / Fishery and biology of Rhinobatos percellens (Rajiformes: Rhinobatidae) caught by the artisanal fishery at La Pared beach, Venezuela

R. percellens is incidentally caught in Venezuela by the artisanal fishery using bottom gillnets. This species was classified by the IUCN as being near threatened, and there is poor knowledge about its biology and fishery in Venezuela. For this reason, we analyzed the specimens caught by the artisanal fleet in playa La Pared, once a week, from January to December 2007. We determined total length, sex and maturity for each captured specimen. A total of 210 specimens were analyzed, 159 females and 51 males. The 81% of all specimens caught were adults, but within this group 27% were pregnant. The average size of sexual maturity was found between 51 and 52cm for females and males, respectively. Adult females were found all year round, and pregnant females in seven of the months sampled; highest numbers were found between February-March and September. The analyzed females had a total of 96 embryos with a size range between 2 and 19cm, with a maximum fertility of four embryos per litter. February and June-July showed the maximum breeding time, and considering the broad range of embryos sizes and the frequency of pregnant females along the different months, allow us to believe that they reproduce throughout the year. Fishing regulation including minimum catch size in relation to maturity length and release of pregnant females in water is recommended.

Rhinobatos percellens es capturada en Venezuela por la flota artesanal que opera con redes de fondo. Está clasificada por la IUCN como casi amenazada, y no existen estudios sobre su biología o pesquería en el país. Por ello, se analizaron desembarques de la pesca artesanal de playa la Pared (isla de Margarita) durante enero-diciembre 2007. A cada ejemplar capturado se le determinó la longitud total, sexo y madurez. Fueron analizados 210 ejemplares, 159 hembras y 51 machos. El 81% de los ejemplares se encontraban maduros y un 27% de este grupo correspondió a hembras grávidas. La talla media de madurez sexual quedó ubicada en 51 y 52cm para hembras y machos, respectivamente. Se detectaron hembras maduras todo el año, y hembras grávidas en siete meses. Fueron analizados 96 embriones con tallas entre 2-19cm, siendo la fecundidad máxima cuatro embriones. La variación de las longitudes de los embriones entre los meses del año indican dos picos máximos de alumbramiento al año pero no existe una sincronía en la cópula ya que la especie se reproduce prácticamente todo el año. Se recomienda elaborar regulaciones pesqueras que incluyan una talla mínima de captura en función de la talla de madurez señalada y liberar las hembras grávidas al agua.

Morphological study of the oviductal gland in the smallnose fanskate Sympterygia bonapartii (Müller and Henle, 1841) (Chondrichthyes, Rajidae) / Estudo morfológico da glândula oviductal no smallnose fanskate Sympterygia bonapartii (Müller and henle, 1841) (Chondrichthyes, Rajidae)

The oviductal gland is an exclusive structure of cartilaginous fishes that produces the egg jelly, forms the tertiary egg envelopes and stores sperm. The biological importance of this structure is related to the special features of the reproductive strategy of the group and to its phylogeny, considering that egg-laying is the ancestral condition in this fish (Dulvy and Reynolds, 1997). This gland of the smallnose fanskate shows four morphofunctional zones. The lining epithelium along the gland is columnar with secretory and ciliated cells. Secretions are mucous and/or proteic according to the zone, and to their specific functions. This is the first report about the microanatomy of the female reproductive tract of S. bonapartii with evidence of sperm storage in the genus.

A glândula oviductal é uma estrutura exclusiva das elasmobrânquias que produz a geléia do ovo, o envoltório terciário do ovo e armazena espermatozóides. Sua importância está relacionada com as características especiais da estratégia reprodutiva do grupo e com a filogenia destes peixes em que oviparidade é a condição ancestral (Dulvy and Reynolds, 1997). A glândula oviductal do smallnose fanskate mostra quatro zonas morfofuncionais. O revestimento em toda a glândula é epitélio colunar ciliado com células glandulares e ciliadas. As secreções são diferentes entre as zonas e relacionada com as suas funções específicas. A informação aqui exposta constitui o primeiro relato sobre a micro-anatomia do trato reprodutivo feminino de S. bonapartii com evidencias de armazenamento do esperma neste gênero.

Morphology of lateral line canals in Neotropical freshwater stingrays (Chondrichthyes: Potamotrygonidae) from Negro River, Brazilian Amazon

The relationship between the distribution of the lateral line canals and their functionality has not been well examined in elasmobranchs, especially among Neotropical freshwater stingrays of the family Potamotrygonidae. The spatial distribution of the canals and their tubules and the quantification of the neuromasts were analyzed in preserved specimens of Potamotrygon motoro, P. orbignyi, Potamotrygon sp. "cururu", and Paratrygon aiereba from the middle Negro River, Amazonas, Brazil. The hyomandibular, infraorbital, posterior lateral line, mandibular, nasal and supraorbital canals were characterized and their pores and neuromasts quantified. The ventral canals are known to facilitate the accurate localization of prey items under the body, and our results indicate that the dorsal canals may be employed in identifying the presence of predators or potential prey positioned above the stingray's body. The presence of non-pored canals in the ventral region may be compensated by the high concentration of neuromasts found in the same area, which possibly allow the accurate detection of mechanical stimuli. The concentration of non-pored canals near the mouth indicates their importance in locating and capturing prey buried in the bottom substrate, possibly aided by the presence of vesicles of Savi.

A relação entre a distribuição dos canais da linha lateral e a sua funcionalidade é pouco conhecida para os elasmobrânquios, especialmente para as raias neotropicais da família Potamotrygonidae. A distribuição espacial dos canais e seus túbulos e a quantificação dos neuromastos foram analisadas em exemplares preservados das raias Potamotrygon motoro, P. orbignyi, Potamotrygon sp. "cururu" e Paratrygon aiereba, provenientes do médio rio Negro, Amazonas, Brasil. Foram identificados os canais hiomandibular, infra-orbital, linha lateral posterior, mandibular, nasal e supra-orbital, e os poros e neuromastos de cada um foram quantificados. Nossos resultados mostram que os canais dorsais podem ter a função de identificar a presença de predadores ou presas posicionadas acima do corpo da raia, enquanto os canais ventrais provavelmente permitem uma localização precisa da posição de presas sob o corpo. A existência de canais sem poros na região ventral pode estar relacionada com a alta concentração de neuromastos, que compensaria a falta de contato direto dos neuromastos com o meio externo na detecção de estímulos mecânicos. A concentração dos canais sem poros na proximidade da boca indica sua importância para a localização e captura de presas enterradas no substrato, possivelmente auxiliadas pela presença das vesículas de Savi.

The ovary of the bignose fanskate Sympterygia acuta Garman, 1877 (Chondrichthyes, Rajidae) in the Bahía Blanca estuary, Argentina: morphology and reproductive features / O ovário da bignose fanskate Sympterygia acuta Garman, 1877 (Chondrichthyes, Rajidae) no estuário de Bahía Blanca, Argentina: morfologia e características reprodutivas

Chondrichthyes have become an important economic resource in recent years. In spite of this importance, there is little knowledge about their reproductive biology, especially of species from the south-western Atlantic. In this work, we study the morphology and histology of the ovary of Sympterygia acuta. The results show that oogonia were present only in the immature females (stage I of maturity scale), whereas specimens in stages II and III of maturity displayed oocytes in all developmental steps. The most important histological features that vary throughout oocyte development are the presence or absence of yolk, the number of types and layers of follicular cells and the degree of development of the thecae. Follicular cells are, at least, of two different types. Finally, a new point of view for the determination of maturity stages in the field based on the size of follicles is discussed.

Os Chondrichthyes tornaram-se num importante recurso econômico nos últimos anos. Apesar da sua importância, é muito pouco o que se conhece da sua biologia reprodutiva, especialmente das espécies do Atlântico sul-ocidental. Neste trabalho, foi estudada a morfologia e histologia do ovário de Sympterygia acuta. Os resultados mostraram que as oogonias somente encontraram-se presentes nas fêmeas imaturas (fase I de escala de maturidade) e que os animais em estágio II e III de maturidade exibiram oocitos em todas as etapas de desenvolvimento. As características histológicas mais importantes que variam ao longo de desenvolvimento dos oocitos são a presença da suarda, o tipo e quantidade de celas foliculares e o grau do desenvolvimento do thecae. Existem pelo menos dois tipos de células foliculares. Finalmente se discute um novo ponto de vista para a determinação dos estágios de maturidade no campo, baseado no tamanho dos folículos.