Caulophryne jordani

Caulophryne jordani, the fanfin angler, is a species of marine ray-finned fish belonging to the family Caulophrynidae, the fanfins. This species is a deepwater species which is found in Oceanic waters around the world. Like other deepwater anglerfishes it shows extreme sexual dimorphism with the males being much smaller than the females and acting as sexual parasites of the females.

Taxonomy
Caulophryne jordani was first formally described in 1896 by the American ichthyologists [George Brown Goode]] and Tarleton Hoffman Bean with its type locality given as the Gulf Stream off Long Island, New York at 39°27'N, 71°15'W, Albatross station 2747 from a depth between 0 and 1276 fathom. When Goode and Bean described the species they placed it in a new monospecific genus, Caulophryne, so this species is the type species of that genus by monotypy. Caulophryne is one of two genera within the family Caulophrynidae. The 5th edition of Fishes of the World classifies the Caulophrynidae within the suborder Ceratioidei of the order Lophiiformes, the anglerfishes.

Etymology
Caulophryne jordani is a species within the genus Caulophryne, this name is a combination of caulis, which mean" stem", an allusion to the stem-like base of the illicium, with phryne, meaning "toad", a suffix commonly used in the names of anglerfish genera. Its use may date as far back as Aristotle and Cicero, who referred to anglerfishes as “fishing-frogs” and “sea-frogs,” respectively, possibly because of their resemblance to frogs and toads. The specific name honours the American ichthyologist, educator, and eugenicist David Starr Jordan, the president of Leland Stanford Jr University in California, in recognition of his work in the field of ichthyology.

Description
Caulophryne jordani has a high degree of sexual dimorphism. The females have short, round bodies with large mouths. The lower jaw reaches back past the base of the pectoral fin. The teeth in the jaws are thin, backwards curving and depressible. They have highly elongated dorsal and anal fins, with the soft rays of these fins resembling long threads. There are 8 fin rays in the caudal fin. They do not have pelvic fins. The sensory cells of the lateral line system are at the tips of the filamentous rays of the dorsal and anal fins. They have a simple esca, or lure, which lacks a bulb but which may have filaments or appendages. The skin is naked and they do not have any dermal spines. The males are much smaller than the females and have more elongated bodies. They have large eyes and large nostrils, with large olfactory receptors. They have no teeth in the jaws, although there are tooth-like structures on the jaw bones which are used to attach to the larger female. The male do not have elongated dorsal and anal fins but so have large pectoral fins. The dorsal fin of this has between 16 and 19 rays while the anal fin has between 14 and 18 rays. The morphology of the esca and illicium distinguish C. jordani from its congeners. In this species the illicium has pigment apart from the part near the esca and there are between 5 and 14 elongated translucent filaments along the whole length of the illicium, all of these except for the ones nearest the esca have their origin on the rear margin of the illicium. The length of the illicium is equivalent to between 16.8% and 36.8% of the standard length. The esca has a long, filamentous appendage arising on its side towards the front, two appendages on its tip which each have manty filaments, thicker toward the front of the appendage and thinner towards the rear. These filaments are opaque along the rear margin and the rearmost are the thinnest. The appendage on the side of the esca near its front has many short filaments and has a palmate and opaque tip. The maximum published total length is 1.6 cm for males and 20 cm for females.

Distribution and habitat
Caulophryne jordani has a circumglobal distribution, although most records come from the Eastern Atlantic Ocean, Southern Ocean and the Indo-Pacific region. It is a bathypelagic species that has been recorded at depths between 100 and 1510 m.

Biology
Caulophryne jordani is a predator on other fishes. They reproduce by means of pelagic eggs which hatch into pelagic larvae. The short, rounded larvae have swollen skin and well-developed pectoral and pelvic fins, the pelvic fins being lost as they metamorphose. Both larval males and females have a basic illicium. Metamorphosis starts at a standard length of 8 to 10 mm. The large, well-developed eyes and olfactory apparatus of the metamorphosed males are used to detect and home in on a species specific chemical released by the female to attract males. When the male finds a female he bites her and the tissue and circulatory systems of the pair fuse, he becomes a sexual parasite on the female and is nourished by the female through shared blood. For the remainder of his life he is attached to the female and fertilises her eggs.