Twineye Skate Raja miraletus

Found in the Mediterranean and Atlantic coast of Africa. Raja are bottom-dwellers that are active during both day and night, and typically feed on molluscs, crustaceans and fish.

DEEP-SEA SKATE USES HYDROTHERMAL VENTS TO INCUBATE EGGS

The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning, continually revealing unique biological processes. Now, experts report for the first time, a unique behavior where Pacific White Skate Bathyraja spinosissima, a deep-sea species, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally “incubate” developing egg-cases. 

In 2015, an international team of researchers used a remotely operated underwater vehicle (ROV) to survey in and around an active hydrothermal field located in the Galapagos archipelago, 28 miles north of Darwin Island.

The researchers found 157 egg cases in the area and collected four with the ROV's robotic arm. DNA analysis revealed that the egg cases belonged to Pacific White Skate. About 58 percent of the egg cases were found within 20 meters of a black smoker, the hottest kind of hydrothermal vent, and 89 percent of the egg cases were laid in water that was hotter than the background temperature of 2.76 C°. Researchers believe that the warmer temperatures in the area could reduce thE incubation time of the eggs.

- Clutch of egg-cases with dark brown coloration.

Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment. Hydrothermal vents are being targeted for deep seabed mining, and the oil and gas industry drills on the margins of methane cold seeps. Their destruction by bottom trawling or mining will impact populations of deep-sea skates.

Photo:  collection of egg-case using the Hercules ROV robotic arm.

An inmature male Shorttail Fanskate (Sympterygia brevicaudata) doing the thing. He arrived in capsule, the embryo prematurely left his capsule, achieved to develop completely, but regretfully passed away shortly after the realization of this video

Shorttail Fanskate is a shallow water fanskate recorded from the Eastern South Pacific from Ecuador, Peru and north and central Chile. It is a small species, reaching at least 26 cm total length and nothing is known of its biology. Little information available to assess the species beyond Data Deficient at this time.

LA RAYA ESTRELLADA YA NO ES ENDÉMICA DEL MEDITERRÁNEO.

La raya estrellada del Mediterráneo (Raja asterias), considerada una especie endémica del Mediterráneo, ha sido recientemente reportada por otros autores en pesquerías atlánticas en el sur de Portugal y el norte de Marruecos. Sin embargo, no se ha documentado correctamente la existencia de la especie fuera del Mediterráneo. Sin embargo, investigadores españoles han publicado el primer registro confirmado genética y morfológicamente de la raya estrellada en aguas del Atlántico, particularmente en el Golfo de Cádiz. 

La especie está catalogada en la lista roja de la IUCN como casi amenazada. Rayas y especies que viven asociadas al fondo marino son vulnerables a el impacto abrasivo de la pesca de arrastre y actividades mineras o extracción de hidrocarburos.

El ejemplar estudiado, una hembra madura de algo más de 60 centímetros y 1.5 kilogramos, se capturó en una pesca de arrastre de fondo durante la campaña de evaluación de recursos pesqueros ARSA. Estas campañas se llevan a cabo anualmente en la pesquería de arrastre del golfo de Cádiz. Este descubrimiento indica la necesidad de incluir la población atlántica de esta especie de raya en la descripción de su distribución geográfica y en futuras evaluaciones de su estado de explotación.

The deepwater chondrichthyan fauna of Papua New Guinea is very poorly understood, despite its rich biodiversity. But recent surveys conducted between 2010 and 2014 by the RV Alis have provided new records of shark and ray species from this region.

Collected during the 2012 expedition off Madang, and reported as softnose skate (Insentiraja subtilispinosa), recent examination of these specimens revealed that they actually represent an undescribed species, recently named Papuan velvet skate (Notoraja sereti), belonging to a subgroup known as the ‘velcro skates’ (because they are covered dorsally and ventrally with fine spinular denticles). This species represents the only species of softnose skate (Family Arhynchobatidae) currently known to occur in Papua New Guinea.

- The Papuan Velvet Skate (Notoraja sereti), lives at depths of 800–980 m.

Also, examination of lantern sharks collected during these surveys (currently housed in Taiwanese fish collections) showed a new species. One of the lantern shark were mistakenly identified at first as Etmopterus brachyurus, but upon detailed examination were determined to represent an undescribed species based on several differences in key characteristics. Furthermore, DNA sequence analysis also confirmed a new species. The new species called Papuan lanternshark (Etmopterus samadiae) is known from off the northern Papua New Guinea mainland, from west of Kairiru Island in East Sepik Province to off Lae in the Huon Gulf (Morobe Province) and at a depth range of 340 to 785 m. 

- Lateral view of Etmopterus samadiae, adult male fresh and post-preservation (click to enlarge)

White et al., 2017 A new species of velvet skate, Notoraja sereti n.sp. (Rajiformes: Arhynchobatidae) from Papua New Guinea. Zootaxa.

La raya-látigo rosa (Himantura fai) es la única especie conocida de raya que expresa este comportamiento de “llevar a cuestas”. De hecho, se sabe de múltiples casos de rayas-latigo rosa que van a cuestas sobre otros miembros de la misma especie, y esto es inesperado, los elasmobranquios, en general, sólo interactúan cuando tratan de comerse unos a otros.

La raya-látigo rosa es un raya de gran tamaño que se encuentra en hábitats de sedimentos blandos costeros en el Océano Índico.

Pero parece que les encanta, y la raya-látigo rosa van a cuestas incluso en otra especie. Las fotografías no mienten.

Las razones de este comportamiento son desconocidas, una posibilidad es que llevar a cuestas podría ser una estrategia de defensa para evitar la depredación, las rayas más pequeñas podrían parecer más grandes de lo que realmente son, rompiendo la silueta de la presa.

También puede haber alguna ventaja hidrodinámica o en la búsqueda de alimento, permitiendo a las rayas más pequeñas viajar con las especies más grandes de esta manera, aunque esto no explica por qué estas rayas llevan a cuestas a otras rayas que descansan en el fondo del mar o en las estaciones de limpieza.

Foto b) raya-látigo rosa  a cuestas sobre una raya moteada (Taeniura meyeni) a una estación de limpieza.

Referencia: Meekan et al. 2016. The piggybacking stingray Coral Reef 

The pink whipray (Himantura fai) is the only species of stingray know to engage in this sort of piggybacking behavior. In fact, multiples pink whiprays piggyback on others rays of the same species, and this is unexpected, elasmobranch, in general only interact when they try to eat each other.

The pink whipray is a large ray that occurs in coastal soft-sediment habitats in the Indian Ocean.

But apparently they love it, and pink whipray piggyback in another species. Pictures don’t lie.

The reasons for this behaviour are unknown, one possibility is that piggybacking is a predator defence strategy that allows the smaller rays to appear larger than they actually are and breaks up silhouettes on which predators can focus. There may also be some hydrodynamic or foraging advantage to the smaller rays in travelling with larger species in this manner, although this does not explain why these rays piggyback on other rays resting on the seabed or at cleaning stations. 

Photo b)  Pink whiprays piggybacking on a blotched fantail ray (Taeniurops meyeni) at a cleaning station.