Cestodes and feeding habits of ray Bathyraja sp. (Rajiformes: Arhynchobatidae) in the North Pacific (Simushir Island)

Сestodes of Pseudanthobothrium purtoni, Phyllobothrium georgiense and Onchobothrium sp. were found in rays of the genus Bathyraja in the Pacific Ocean (island Simushir) for the first time. It is revealed that Bathyraja sp. (TL 21.1–48.5 cm) feeds on amphipods (Acanthostepheia behringiensis, Ampelisca eschrichti, Eusirus cuspidatus, Gammaridea fam. gen. sp., Lysianassidae gen. sp., Oedicerotidae gen. sp., Stenothoidae gen. sp.), isopods (Arcturus crenulatus) and teleost fish. Due to change of the age feed spectrum of Bathyraja sp., characterized by the appearance of teleosts, the number of cestodes parasitizing them increases

New species of Guidus Ivanov, 2006 (Cestoda: Phyllobothriidea) from Bathyraja magellanica (Philippi) from the Patagonian Continental Shelf of Argentina

Specimens representing two new species of Guidus were collected from the Magellan skate (Bathyraja magellanica) in the Patagonian Continental Shelf of Argentina, Southwestern Atlantic Ocean. Guidus francoi sp. n. and Guidus magellanicus sp. n. differ from their congeners by a particular combination of features including type of bothridia, worm length, number of testes, and distribution of vitelline follicles. Guidus francoi sp. n. is distinguished from G. magellanicus sp. n. by having fewer proglottids, fewer testes and a higher ratio between the cirrus sac length and the proglottid width. The microtrix pattern of species of Guidus from the Southwestern Atlantic is described, based on specimens of Guidus francoi sp. n., Guidus magellanicus sp. n., and newly collected specimens of G. argentinense. These three species share the presence of wide aristate gladiate spinitriches on the proximal bothridial surface, narrow gladiate spinitriches on the bothridial rim, and filitriches on the distal bothridial surface. The diagnosis of Guidus is revised to include several features exhibited by the new species (i.e., presence of bothridial indentations and bothridial stalks, distribution of vitelline follicles, and eggs grouped in cocoons). The discovery of G. francoi sp. n. and G. magellanicus sp. n. from B. magellanica increases the number of species of Guidus collected from batoids in the Southwestern Atlantic from one to three. The specificity exhibited by the species herein described reinforces the tight association between Guidus and Bathyraja hosts.Fil: Menoret, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Ivanov, Veronica Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

Condrictios de la Argentina y Uruguay: lista de trabajo

Presentamos aquí una lista actualizada de los condrictios (tiburones, rayas, quimeras y pez elefante) que han sido citados de la Argentina y Uruguay, incluyendo las especies de agua dulce de la familia Potamotrygonidae. Cuando una especie está presente en Argentina o en Uruguay, se lo indica a continuación de la especie; las demás, son compartidas. No se indica la distribución de las especies en otras áreas. Muchas de las especies conocidas de Uruguay terminan allí su distribución meridional, y ocasionalmente algunas entran a aguas argentinas y otras podrían hacerlo. Estas presencias ocasionales parecen no ser muy comunes. La progresiva disminución de las capturas de Dasyatis violacea con la disminución de temperatura hacia el sur ha sido demostrada (Domingo et al., 2005). En 1981 Menni publicó una lista de las familias de peces que no sobrepasaban la latitud del Río de La Plata, y de los condrictios mencionados, Orectolobidae, Ginglymostomatidae y Rhinopteridae, sólo una especie de la última familia ha sido citada en años recientes de Uruguay. Al contrario, especies que han sido citadas de la Argentina, como Sphyrna tudes de Mar del Plata por Berg (1895) o Narcine brasiliensis de la provincia de Buenos Aires por Lahille (1928), no han sido halladas de nuevo. La lista está basada en el catálogo crítico de Menni et al. (1984), y se han hecho las modificaciones taxonómicas necesarias y agregado las especies nuevas para el área. Debido al carácter práctico de esta lista, sólo se incluyen los autores de las especies y la fecha de su descripción. En los nuevos registros se agrega un breve comentario fundamentando la inclusión. Estando disponible el catálogo de Eschmeyer (1998) y su versión on-line, nos pareció que más detalles eran innecesarios. En la macrosistemática de los holocéfalos se sigue a Didier (2004), en la de los tiburones a Compagno (2005) y en la de los batoideos a McEachran & Aschliman (2004). Para las especies de Uruguay se ha seguido principalmente a Nion et al. (2002) y a Meneses y Paesch (1997), y deben mencionarse los trabajos anteriores de Ximénez (1962) y de Carrera (1991) que proveen referencias previas. La bibliografía se limita a trabajos generales que pueden ser de utilidad, los trabajos en que se basan las nuevas referencias, y los que corresponden a comentarios. No se han incluido numerosos trabajos sobre biología y ecología de estos organismos, que han modificado mucho la información resumida en Menni (1986), pero sí algunos que muestran cambios considerables de distribución. (PDF tiene 18 paginas.

Diet and ecomorphology of the sandpiper skate, Bathyraja kincaidii (Garman, 1908) from the eastern North Pacific

Stomach contents of the sandpaper skate, Bathyraja kincaidii (Garman, 1908), were examined from a limited depth off central California and from a wider depth and area range along the eastern North Pacific (ENP). The species overall diet was dominated by euphausiids and shrimps, with polychaetes, squids, and gammarid amphipods important secondary prey. A three-factor MANOVA demonstrated significant differences in the importance of major prey categories by sex, maturity status, and oceanographic season in the central California data. These three main factors explained the greatest amount of dietary variation and season explained the most variance overall. Differences in the diet by sex, maturity status, and geographic zone of capture occurred in the ENP. Geographic zone explained the most variance in the diet, though much less than the amount explained by the central California data. A three-factor MANCOVA revealed significant differences in the oral and dental morphology of B. kincaidii due to all the main factors (sex, maturity status, and geographic zone) and their interactions among all variables measured. However, variation between the sexes explained one third of all the morphological variance. A comparison of the intra-specific differences in morphology with such differences in the diet indicated that the two were not related. I suggest that intra-specific differences in the morphology of skates are related more to mating; the extreme morphology of mature males allows them to better capture and hold females during courtship, but such differences do not satisfactorily account for differential exploitation of any prey category

Bathyraja cousseauae sp.n.: A New Softnose Skate from the Southwestern Atlantic (Rajiformes, Rajidae)

A new species of softnose skate, Bathyraja cousseauae, is described from two adult and 19 juvenile specimens collected from different localities of the southwestern Atlantic. Bathyraja cousseauae is distinguished from all other southwestern Atlantic softnose skate species by its color pattern, squamation pattern of dorsal surface, lack of interspace between dorsal fins, and clasper morphology. The new species has a round pale area ocellus-like, margined with dark brown on posterior part of each pectoral base of dorsal surface, paler and dark spots over the disk, a continuous row of 21–27 median thorns from nuchal region to first dorsal fin and upper side of disc densely covered with dermal denticles. Males have rod-shaped claspers not expanded at proximal section of glans as it does in Bathyraja brachyurops. Besides the external morphological features, skeletal characteristics (neurocranium, scapulocoracoids, and claspers) are also described and illustrated here.Bathyraja cousseauae, is described from two adult and 19 juvenile specimens collected from different localities of the southwestern Atlantic. Bathyraja cousseauae is distinguished from all other southwestern Atlantic softnose skate species by its color pattern, squamation pattern of dorsal surface, lack of interspace between dorsal fins, and clasper morphology. The new species has a round pale area ocellus-like, margined with dark brown on posterior part of each pectoral base of dorsal surface, paler and dark spots over the disk, a continuous row of 21–27 median thorns from nuchal region to first dorsal fin and upper side of disc densely covered with dermal denticles. Males have rod-shaped claspers not expanded at proximal section of glans as it does in Bathyraja brachyurops. Besides the external morphological features, skeletal characteristics (neurocranium, scapulocoracoids, and claspers) are also described and illustrated here.Bathyraja cousseauae is distinguished from all other southwestern Atlantic softnose skate species by its color pattern, squamation pattern of dorsal surface, lack of interspace between dorsal fins, and clasper morphology. The new species has a round pale area ocellus-like, margined with dark brown on posterior part of each pectoral base of dorsal surface, paler and dark spots over the disk, a continuous row of 21–27 median thorns from nuchal region to first dorsal fin and upper side of disc densely covered with dermal denticles. Males have rod-shaped claspers not expanded at proximal section of glans as it does in Bathyraja brachyurops. Besides the external morphological features, skeletal characteristics (neurocranium, scapulocoracoids, and claspers) are also described and illustrated here.Bathyraja brachyurops. Besides the external morphological features, skeletal characteristics (neurocranium, scapulocoracoids, and claspers) are also described and illustrated here.Fil: Díaz de Astarloa, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Marinas; ArgentinaFil: Mabragaña, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Marinas; Argentin

Early life sensory ability—ventilatory responses of thornback ray embryos (Raja clavata) to predator-type electric fields

Predator avoidance is fundamental for survival and it can be particularly challenging for prey animals if physical movement away from a predatory threat is restricted. Many sharks and rays begin life within an egg capsule that is attached to the sea bed. The vulnerability of this sedentary life stage is exacerbated in skates (Rajidae) as the compulsory ventilatory activity of embryos makes them conspicuous to potential predators. Embryos can reduce this risk by mediating ventilatory activity if they detect the presence of a predator using an acute electrosense. To determine how early in embryonic life predator elicited behavioral responses can occur, the reactions of three different age groups (1/3 developed, 2/3 developed, and near hatching) of embryonic thornback rays Raja clavata were tested using predator-type electric field stimuli. Egg capsules were exposed to continuous or intermittent stimuli in order to assess varying predator-type encounter scenarios on the ventilatory behavior of different developmental stages. All embryos reacted with a “freeze response” following initial electric field (E-field) exposure, ceasing ventilatory behavior in response to predator presence, demonstrating electroreceptive functionality for the first time at the earliest possible stage in ontogeny. This ability coincided with the onset of egg ventilatory behavior and may represent an effective means to enhance survival. A continuous application of stimuli over time revealed that embryos can adapt their behavior and resume normal activity, whereas when presented intermittently, the E-field resulted in a significant reduction in overall ventilatory activity across all ages. Recovery from stimuli was significantly quicker in older embryos, potentially indicative of the trade-off between avoiding predation and adequate respiration. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 721–729, 201

Survival rates of rays discarded by the bottom trawl squid fishery off the Falkland Islands

Waters off the Falkland Islands are subject to a specialized multispecies ray fishery and were first fished by a Korean fleet in 1989. More than twenty different rajid species have been recorded from catches around the islands, and five species accounted for 87.04% of the total catch during 1993−2002. Catches peaked in 1993 at 8523 metric tons, and specific fishing licenses — R (second season) and F (first season) — were first introduced in 1994 and in 1995, respectively (Agnew et al. 2000; Falkland Islands Government, 2002; Wakeford et al., in press)

Trophic niche partitioning of five skate species of genus Bathyraja in northern and central Patagonia, Argentina

Overexploitation of marine communities can lead to modifications in the structure of the food web and can force organisms like elasmobranchs to change their feeding habits. To evaluate the impact that fisheries have on food webs and on the interactions between species, it is necessary to describe and quantify the diet of the species involved and follow it through time. This study compares the diet of five skate species using the data obtained from the by-catch of the Argentine hake (Merluccius hubbsi) fishery in north and central Patagonia, Argentina. Diet composition was assessed by analysing the digestive tract contents and trophic overlapping between species of the genus Bathyraja: Bathyraja albomaculata, Bathyraja brachyurops, Bathyraja macloviana, Bathyraja magellanica and Bathyraja multispinis. A total of 184 stomachs were analysed. The diets of B. albomaculata and B. macloviana mainly comprised annelids, whereas that of B. brachyurops primarily comprised fish, including hake heads discarded by the fishery. The diets of B. magellanica and B. multispinis were largely based on crustaceans. Despite the morphological similarities and their shared preference for benthic habitats, no complete diet overlaps were found between the different species. These results suggest that these skate species have undergone a process of diet specialisation. This is a common feeding strategy that occurs to successfully eliminate competition when resources are limited, which corresponds to the conditions found in an environment being affected by the pressures of overfishing.Fil: Tschopp, Ayelen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Cristiani, Franco. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales y Ciencias de la Salud - Sede Puerto Madryn. Departamento de Biología y Ambiente; ArgentinaFil: Garcia, Nestor Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales y Ciencias de la Salud - Sede Puerto Madryn. Departamento de Biología y Ambiente; ArgentinaFil: Coscarella, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales y Ciencias de la Salud - Sede Puerto Madryn. Departamento de Biología y Ambiente; Argentin

Seamount egg-laying grounds of the deep-water skate Bathyraja richardsoni

Highly localized concentrations of elasmobranch egg capsules of the deep-water skate Bathyraja richardsoni were discovered during the first remotely operated vehicle (ROV) survey of the Hebrides Terrace Seamount in the Rockall Trough, north-east Atlantic Ocean. Conductivity–temperature–depth profiling indicated that the eggs were bathed in a specific environmental niche of well-oxygenated waters between 4·20 and 4·55∘ C, and salinity 34·95–35·06, on a coarse to fine-grained sandy seabed on the seamount’s eastern flank, whereas a second type of egg capsule possibly belonging to the skate Dipturus sp.) was recorded exclusively amongst the reef-building stony coral Solenosmilia variabilis. The depths of both egg-laying habitats (1489–1580 m) provide a de facto refuge from fisheries mortality for younger life stages of these skates