The cusk-eel family, Ophidiidae, is a group of marine Osteichthyes in the Ophidiiformes order. The scientific name is from the Greek language ophis meaning "snake", and refers to their eel-like appearance. True eels diverged from other Actinopterygii during the Jurassic, while cusk-eels are part of the Percomorpha clade, along with tuna, perch, seahorses, and others.
The oldest fossil cusk-eel is Ampheristus, a highly successful genus with numerous species that existed from the Late Cretaceous (Maastrichtian) to the early Oligocene.
Distribution
Cusk-eels live in temperate and tropical oceans throughout the world. They live close to the sea bottom, ranging from shallow water to the
hadal zone. One species,
Abyssobrotula galatheae, was recorded at the bottom of the Puerto Rico Trench, making it the deepest recorded fish at .
Ecology
Cusk-eels are generally very solitary in nature, but some species have been seen to associate themselves with tube worm communities.
Liking to be hidden when they are not foraging, they generally associate themselves within muddy bottoms, sinkholes, or larger structures that they can hide in or around, such as caves, coral crevices, or communities of bottom-dwelling invertebrates, with some parasitic species of cusk-eel actually living inside of
invertebrate hosts, such as
,
and
.
Cusk-eels generally feed
Nocturnality, preying on
Invertebrate,
and other small bottom-dwelling fishes.
Phylogeny
Due to the inconsistencies in specific morphological characteristics in closely related species, attempts to use different characteristics, such as the position of
, to classify Ophiididae into distinct families have proven highly unsatisfactory. Overall, Ophidiidae are classified based on whether or not they practice viviparity and the structures they contain that are associated with bearing life.
Characteristics
Cusk-eels are characterized by a long, slender body that is about 12–13 times as long as it is deep. The largest species,
Lamprogrammus shcherbachevi, grows up to in length, but most species are shorter than . Their dorsal and anal fins are typically continuous with the
caudal fin (with exception to a few species), forming a long, ribbon like fin around the posterior of the cusk-eel's body.
This caudal fin will often be seen to be reduced to a fleshy or bony point, especially when confluent with the dorsal and anal fins. The
dorsal fin to
anal fin ray ratio is approximately 1.5:1, leading to the dorsal fin typically being longer than the anal. The
pectoral fins of cusk-eels are typically longer than the length of their head. Unlike true
of the order
Anguilliformes, cusk-eels have
that are developed into a forked barbel-like organ below the mouth. In true eels by contrast, the ventral fins are never well-developed and usually missing entirely.
Cusk-eels have large mouths relative to their heads, with the upper jaw reaching beyond the eye, and paired nostrils on either side of the head. In cusk-eels,
Fish scale are potentially absent; when present, they are small.
Reproduction
Unlike their close relatives, the
Viviparity brotulas of the family
Bythitidae, cusk-eel species are egg-bearing, or
Oviparity, organisms. While the specifics of the eggs of the family Ophidiidae are unknown, they are believed to be either spawned as individual, free-floating eggs in the open water or are placed in a mucilaginous raft, which will float for several days until they hatch into cusk-eel larvae. These larvae live amongst the
plankton relatively close to the water's surface
and are believed to control their metamorphoses into adult cusk-eels, dispersing over greater distances into less utilized habitats and reducing competition in concentrated areas.
Conservation status
While a few species are fished commercially – most notably the
pink cusk-eel,
Genypterus blacodes – and several species of the order Ophidiiformes are listed as vulnerable, not enough information has been gathered about Ophidiidae as a whole to determine their conservation status.
Genera
The cusk-eel family contains about 240 species, grouped into 50
genera:
Subfamily Brotulotaenilinae
Subfamily
Neobythitinae
Subfamily Ophidiinae
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