tiburón linterna enano

El tiburón linterna enano ( Etmopterus perryi ) es una especie de tiburón de la familia Etmopteridae y es el tiburón más pequeño del mundo, alcanzando una longitud máxima conocida de 20 cm (8 pulgadas) . Se sabe que solo está presente en las pendientes continentales superiores de Colombia y Venezuela , a una profundidad de 283–439 m (928–1440 pies) . Esta especie se puede identificar por su pequeño tamaño en la madurez, su cabeza larga y aplanada, y un patrón de marcas ventrales negras y una línea medio-dorsal. Al igual que otros miembros de su género , es capaz de producir luz a partir de una distintiva disposición de fotóforos . La reproducción es vivípara aplacentaria , con hembras que gestan dos o tres crías a la vez. El tiburón linterna enano no es significativo para la pesca comercial , pero podría verse amenazado por la mortalidad debida a la captura incidental ; se desconoce el grado de impacto de las actividades humanas en su población.    

Los ictiólogos estadounidenses Stewart Springer y George H. Burgess describieron el tiburón linterna enano a partir de especímenes recolectados mediante arrastre por el buque de investigación Oregon del Servicio de Pesca y Vida Silvestre de los Estados Unidos en 1964. Bautizaron a la nueva especie en honor al reconocido biólogo de tiburones Perry W. Gilbert y publicaron sus hallazgos en un artículo de Copeia en 1985. El espécimen tipo es una hembra de 18,2 cm (7,2 pulgadas) de largo capturada en el mar Caribe frente a la costa de Colombia . Esta especie se agrupa con el tiburón linterna de vientre aterciopelado ( E. spinax ), el tiburón linterna del Caribe ( E. hillianus ), el tiburón linterna de aleta franjeada ( E. schultzi ), el tiburón linterna marrón ( E. unicolor ), el tiburón linterna de bandas anchas ( E. gracilispinis ) y el tiburón linterna de dientes de peine ( E. decacuspidatus ) por tener dentículos dérmicos en forma de aguja dispuestos irregularmente . ^{[ 2 ]}  

At present, the dwarf lanternshark has been reported only from a small area of the Caribbean Sea off the coasts of Colombia and Venezuela, occurring between Barranquilla and Santa Marta, near the Guajira Peninsula, and between the Los Testigos Islands and Grenada.^[2] This shark apparently inhabits the upper continental slope at a depth of 283–439 m (928–1,440 ft).

The dwarf lanternshark appears to reach a maximum length of about 20 cm (7.9 in) (female).^[3] It has a long, wide, flattened head comprising a fourth to a fifth of its total length. The eyes are large, twice as long as high, with the anterior and posterior corners acute. The nares are large and preceded by poorly developed flaps of skin. There are 25–32 tooth rows in the upper jaw and 30–34 tooth rows in the lower jaw. The upper teeth of adult males have a single cusp flanked by two pairs of smaller cusplets, while the upper teeth of females are more robust and have only one pair of lateral cusplets flanking the central cusp. The lower teeth each have a single, strongly oblique cusp, and their bases are interlocked to form a continuous cutting surface. Scattered, sparse papillae are inside the mouth and on the edges of the gill arches. The five pairs of gill slits are small.^[2]

The trunk is short, with two relatively closely spaced, large dorsal fins bearing grooved spines in front. The first dorsal fin originates over the trailing margins of the pectoral fins. The second dorsal fin has twice the area of the first and is larger than the pectoral or pelvic fins, and originates over the end of the pelvic fin bases. There is no anal fin. The caudal fin is low, with a moderate lower lobe and a ventral notch near the tip of the upper lobe. The skin is densely covered by thin, needle-like dermal denticles in a random pattern, except for the lips and the tips of the fins. This shark is dark brown with a striking and distinctive pattern of black markings on its ventral surface, a continuous or broken, fine black line along the middle of its back (but without a white band like in the similar Caribbean lanternshark), a black band on the end of its caudal fin, and a dark blotch on its lower caudal fin lobe.^[2][4] Some of the ventral black markings are composed of light-producingphotophores, while others (including the patch behind the pelvic fins) are composed of pigment-containing chromatophores.^[2] The largest known individual is 21.2 cm (8.3 in) long.^[1]

Perhaps the smallest living shark species,^[5] male dwarf lanternsharks mature at a length of 16–17.5 cm (6.3–6.9 in) and females from a length of 15.5 cm (6.1 in) with 19–20 cm (7.5–7.9 in) long pregnant individuals known.^[1] The spined pygmy shark (Squaliolus laticaudus) and the pygmy ribbontail catshark (Eridacnis radcliffei) are known to attain maturity at comparably small sizes; difficulties in assessing the reproductive maturity of sharks precludes stating one of these species as definitively smaller than the others.^[5] This species is aplacental viviparous, with the developing fetuses being sustained by a yolk sac until birth. Females bear litters of two or three young, each measuring 5.5–6.0 cm (2.2–2.4 in) long.^[1]

Because of its very small size, the dwarf lanternshark is of no economic value. Its low fecundity and limited known range may merit concern if commercial fisheries in the region are taking it as bycatch. The International Union for Conservation of Nature assesses it as least concern.^[1]