''Aldrovandia phalacra'', the Hawaiian halosaurid, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Halosauridae Halosaurs are eel-shaped fishes found only at great ocean depths. As the family Halosauridae, halosaurs are one of two families within the order Notacanthiformes; the other being the deep-sea spiny eels, Notacanthidae. Halosaurs are thought to h ...

. It is a circumglobal species found at

bathyal The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagi ...

depths.

Description

''Aldrovandia phalacra'' is a long, slim, cylindrical fish growing to a length of . The snout is pointed with the upper jaw longer than the lower jaw. There are several separate palatine patches with teeth on the roof of the mouth. There are no scales on the snout, head or operculum. Mature males with ripe gonads have their nostrils extended into a dark coloured tube. There is a row of 24 to 28 large scales along the lateral line. The dorsal fin has 10 to 12 soft rays, the ventral fin has 1 spine and 8 soft rays and the pectoral fin has 1 spine and 11 to 13 soft rays. The head is steely blue, darker below, with a dark line edging the gill covers. The body is pale grey.''Aldrovandia phalacra''
Marine Species Identification Portal. Retrieved 2012-05-02.

Distribution

''Aldrovandia phalacra'' is a deep water fish, living at depths of . It is found in warm waters on the continental shelf, around islands
FishBase. Retrieved 2012-05-03. and in the vicinity of seamounts. Its range includes the Eastern Atlantic between 15° N and 45° N, the Western Atlantic at similar latitudes, the coastal shelves of South Africa and Brazil, the Indian Ocean and the vicinity of Hawaii. During exploratory trawls round the

Bear Seamount The Bear Seamount is a guyot or flat-topped underwater volcano in the Atlantic Ocean. It is the oldest of the New England Seamounts, which was active more than 100 million years ago. It was formed when the North American Plate moved over the New ...

, it was the commonest species of fish.

Behaviour

''Aldrovandia phalacra'' is

benthopelagic The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

. It hovers within a few metres of the seabed, darting down to catch the small

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s on which it feeds. These include

amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...

mysid Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in thi ...

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s and Polychaete, polychaete worms.

References

Halosauridae Fish described in 1888 {{Notacanthiformes-stub