''Assessor macneilli'', the blue devilfish or blue scissortail, is a fish from the southwest

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

Ocean. It occasionally makes its way into the aquarium trade. It grows to in length. It is purple-blue with long fins.

Description

''Assessor macneilli'' is a dark blue fish which has a thin paler blue edge on the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...

anal Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving ...

, and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s. The dorsal fin has 11 spines and 8-10 rays, the anal fin has 3 spines and 9-10 rays and the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s have 14-16 rays.

Distribution

The blue devilfish is found in the western Pacific Ocean from north eastern Australia and New Guinea, through the

Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

and the

Coral Sea The Coral Sea () is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends down the Australian northeast coast. Most of it is protected by the Fren ...

to New Caledonia.

Habitat and biology

''Assessor macneilli'' is found on reefs at depths of , where it can group together in shoals of up 100 fishes in caves, crevices and under ledges, where they often swim upside down. It is a

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...

feeder and its main food are

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

s such as

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

ostracods Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typi ...

and

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 ...

. It is a

mouthbrooder Mouthbrooding, also known as oral incubation and buccal incubation, is the care given by some groups of animals to their offspring by holding them in the mouth of the parent for extended periods of time. Although mouthbrooding is performed by a va ...

and the male guards the eggs in his mouth for 15–16 days, as hatching approaches the male keeps his mouth open continually and shifts the eggs backwards and forwards every 2–8 minutes.

Naming

''Assessor macneilli'' was described in 1935 by G.P. Whitley from specimens collected at

Hayman Island Hayman Island is the most northerly of the Whitsunday Islands, off the coast of Central Queensland in the locality of Whitsundays in the Whitsunday Region, Queensland, Australia. The island is . It is a private island open to the public, most f ...

in the

Whitsunday Passage The Whitsunday Islands are 74 continental islands of various sizes off the central coast of Queensland, Australia, north of Brisbane. The northernmost of the islands are off the coast by the town of Bowen, while the southernmost islands are o ...

off

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

. Whitley did not set out why he chose the name but it is thought that the genus name ''Assessor'' means assistant or helper and that the specific name refers to Whitley's colleague, the

carcinologist A carcinologist is a scientist who studies crustaceans or is otherwise involved in carcinology (the science of crustaceans). References {{Reflist, 24em . Carcinologists ...

Francis A. McNeill of the

Australian Museum The Australian Museum is a heritage-listed museum at 1 William Street, Sydney central business district, New South Wales, Australia. It is the oldest museum in Australia,Design 5, 2016, p.1 and the fifth oldest natural history museum in th ...

. McNeill probably assisted Whitley in his

ichthyological Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish ( Chondrichthyes), and jawless fish ( Agnatha). According to FishBase, 33,400 species of fish had been described as of Octob ...

collections.

References

{{Taxonbar, from=Q590024 macneilli Fish described in 1935