are blennioids; perciform marine fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
of the odd family Dactyloscopidae
. Found in temperate to tropical waters of North
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
; some may also inhabit brackish environments.. There are 44 species in nine genera represented, the giant sand stargazer (Dactylagnus mundus
) being the largest at 15 centimetres in length; all other species are under 10 centimetres.
These blennies are named well: sand stargazers have protruding eyes on the top of their heads, fixed in an upward gaze, and may be on stalks. Their large mouths are also upturned. The dorsal fin is long and may or may not be continuous, with 7-23 spines; the pelvic fins are situated below the throat and possess one spine. The anal fin is equally long and flowing. The mouth is fringed, and like the upper edge of the operculum
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
(the gill cover), this fringe is divided into finger-like structures. The body is greatly elongate and coloration is generally drab.
As their name would suggest, sand stargazers spend most of their time buried in sandy substrates waiting for unsuspecting prey; only the eyes, nose and mouth are usually visible. Their mode of respiration is also unique among the blennioids, utilizing a branchiostegal
rather than opercular
pump; this is thought to be an adaptation to their largely sedentary, obscured lives. Sand stargazers generally stay within shallow (< 10 metres) intertidal zones in areas protected from surges. Small invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and fishes make up the bulk of the sand stargazer's diet.
The family name Dactyloscopidae
derives from the Greek
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
meaning "finger" (a reference to the divided mouth and operculum fringes) and skopein
meaning "to watch".