|Mudskippers in The Gambia|
Mudskippers are members of the subfamily Oxudercinae (tribe Periophthalmini), within the family Gobiidae (gobies). They are completely amphibious fish that can use their pectoral fins to walk on land. Being amphibious, they are uniquely adapted to intertidal habitats, unlike most fish in such habitats which survive the retreat of the tide by hiding under wet seaweed or in tidal pools.
Mudskippers are quite active when out of water, feeding and interacting with one another, for example, to defend their territories. They are found in tropical, subtropical, and temperate regions, including the Indo-Pacific and the Atlantic coast of Africa.
Compared with fully aquatic gobies, these fish present a range of peculiar behavioural and physiological adaptations to an amphibious lifestyle. These include:
- Anatomical and behavioural adaptations that allow them to move effectively on land as well as in the water: As their name implies, these fish use their fins to move around in a series of skips. They can also flip their muscular bodies to catapult themselves up to 2 ft (60 cm) into the air.
|“||Although mudskippers’ fins do not have a joint homologous to the elbow, the joint between the radials and the fin rays serves a functionally analogous role.||”|
|“||The mudskipper pectoral fin differs from most actinopterygian fishes in that the radials of the mudskipper pectoral fin are elongate and protrude from the body wall. This unusual morphology creates a pectoral fin with two fin segments (the radials and the rays) and two movable hinge joints: a `shoulder' joint where the cleithrum meets the radials and a `intra-fin' joint where the radials meet the rays (Harris, 1959). In addition, [...] the abductor superficialis muscle of the pectoral fin is divided into two sections (rather than being a single muscle, as is common with the rest of the Oxudercinae gobies) with one section inserting on the dorsal rays and the other section inserting on the ventral rays (Murdy, 1989).||”|
- The ability to breathe through their skin and the lining of their mouth (the mucosa) and throat (the pharynx): This is only possible when the mudskippers are wet, limiting them to humid habitats and requiring they keep themselves moist. This mode of breathing, similar to that employed by amphibians, is known as cutaneous air breathing. Another important adaptation that aids breathing while out of water is their enlarged gill chambers, where they retain a bubble of air. These chambers close tightly when the fish is above water, keeping the gills moist, and allowing them to function. They act like a scuba diver's cylinders, and supply oxygen for respiration also while on land.
- Digging deep burrows in soft sediments allow the fish to thermoregulate, avoid marine predators during the high tide when the fish and burrow are submerged, and for laying their eggs.
The genus Periophthalmus is by far the most diverse and widespread genus of mudskipper. Eighteen species have been described. Periophthalmus argentilineatus is one of the most widespread and well-known species. It can be found in mangrove ecosystems and mudflats of East Africa and Madagascar east through the Sundarbans of Bengal, Southeast Asia to Northern Australia, southeast China, and southern Japan, to Samoa and Tonga Islands. It grows to a length of about 9.5 cm  and is a carnivorous opportunist feeder. It feeds on small prey such as small crabs and other arthropods. Another species, Periophthalmus barbarus, is the only oxudercine goby that inhabits the coastal areas of western Africa.
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