The sand goby (''Pomatoschistus minutus''), also known as a polewig"Polewig" and "pollybait" in Webster's Unabridged Dictionary
/ref> or pollybait, is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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 h ...

native to marine and brackish waters European waters from the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...

through the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...

and into the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Ro ...

where it occurs in sandy or muddy areas of inshore waters at depths of from . This species can reach a length of TL. This species is sometimes kept in

public aquarium A public aquarium (plural: ''public aquaria'' or ''public Water Zoo'') is the aquatic counterpart of a zoo, which houses living aquatic animal and plant specimens for public viewing. Most public aquariums feature tanks larger than those kept ...

s. The sand goby is of a sandy colour, with darker markings on the sides and a creamy-white underside. In the breeding season the male fish has blue spot at the rear of the first dorsal fin, ringed with white. The fish has a slender body, and the head is about a quarter of the total length.

Description

The sand goby has two dorsal fins with a wider gap between them than the common goby (''Pomatoschistus microps''), the anterior one consisting of six soft spines and the posterior one eight to eleven soft rays. The pelvic fins are fused with the anal fins. There are 58 to 72 scales along the lateral line and these scales are rather smaller than those of the common goby. The caudal fin is rounded. In males, there is a conspicuous dark spot on the anterior dorsal fin and in both sexes there is a black patch on the

caudal peduncle 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 se ...

. The general colour is sandy brown with indistinct dark blotches and reticulations on the dorsal surface and dark striations on the pale fins. The colour of the male darkens during the breeding season and his fins become more coloured. The average size is about .

Behaviour

The sand goby normally lives at greater depths than the common goby. It feeds on 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 chorda ...

s living on the seabed especially

amphipod 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 de ...

s. It is well

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

d and lies motionless on the bottom waiting for its

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation (wh ...

to approach. It breeds in the summer, the male building a nest usually under a shell (which can be turned over if necessary). The female lays the eggs on the underside of this.

References

{{Taxonbar, from=Q1121059 Pomatoschistus Marine fish of Europe Fish of the Atlantic Ocean Fish of the North Sea Fish of the Black Sea Fish of the Baltic Sea Fish described in 1770 Taxa named by Peter Simon Pallas