Mudskipper | |
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Atlantic mudskipper (Periophthalmus barbarus) in The Gambia | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Gobiiformes |
Family: | Oxudercidae |
Subfamily: | Oxudercinae Gunther 1861 [1] |
Genera | |
Apocryptes Contents | |
Synonyms | |
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Mudskippers are any of the 23 extant species of amphibious fish from the subfamily Oxudercinae of the goby family Oxudercidae. [2] They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestrial locomotion and jumping, and the ability to survive prolonged periods of time both in and out of water.
Mudskippers can grow up to 30 cm (12 in) long, and most are a brownish green colour that ranges anywhere from dark to light. During mating seasons, the males will also develop brightly coloured spots in order to attract females, which can be red, green or blue. Unlike other fish, the mudskipper's eyes protrude from the top of its flat head. Their most noticeable feature however is their side pectoral fins that are located more forward and under their elongated body. These fins are jointed and function similarly to limbs, which allow the mudskipper to crawl from place to place. Although having the typical body form of any other gobiid fish, these front fins allow the mudskipper to actively "skip" across muddy surfaces (hence the common name) and even climb low-hanging tree branches and scrubs. Mudskippers have also been found to be able to leap distances of up to 61 centimetres (24 in) by laterally flexing and pushing with their tails.[ citation needed ]
Oxudercinae is sometimes classified within the family Gobiidae (gobies). [3] Recent molecular studies do not support this classification, as oxudercine gobies appear to be paraphyletic relative to amblyopine gobies (Gobiidae: Amblyopinae), thus being included in a distinct " Periophthalmus lineage", together with amblyopines. [4] Mudskippers can be defined as oxudercine gobies that are "fully terrestrial for some portion of the daily cycle" (character 24 in Murdy, 1989 [3] ). This would define the species of the genera Boleophthalmus, Periophthalmodon, Periophthalmus, and Scartelaos as "mudskippers". However, field observations of Zappa confluentus suggest that this monotypic genus should be included in the definition. [5]
Mudskippers typically live in burrows in intertidal habitats, and exhibit unique adaptations to this environment that are not found in most intertidal fishes, which typically survive the retreat of the tide by hiding under wet seaweed or in tide pools. [6] These burrows are most often characterised by their smooth and vaulted ceilings. The way the males dig these burrows has been found to be directly linked to their ability to survive submerged in almost anoxic water. It has also been found to play a crucial role in the development of the eggs within the burrow. Mudskippers are quite active when out of water, feeding and interacting with one another, for example, to defend their territories and court potential partners. Once the male has completed digging his burrow he will resurface and will begin attempting to attract a female through assorted yet typical displays. These displays consist of body undulations, different postures and energetic movements. Once the female has made her choice she will then proceed to follow the male into the burrow where she will lay hundreds of eggs and allow them to be fertilized. After fertilization occurs, the period of cohabitation between the male and female is rather short. Eventually, the female will leave and it is the male that ends up guarding the egg filled burrow from hungry predators.[ citation needed ]
Mudskippers are amphibious. When leaving the water and moving into a more dry environment on land, they are still able to breathe using water that is trapped inside their large gill chambers. They are also able to absorb oxygen from the lining of their mouth and throat, allowing them to stay out of water for long periods of time. It has been discovered that they spend up to three quarters of their life on land. They are found in tropical, subtropical, and temperate regions, including the Indo-Pacific and the Atlantic coast of Africa.[ citation needed ]
Compared with fully aquatic gobies, these specialised fish present a range of anatomical and ethological adaptations that allow them to move effectively on land as well as in the water. [7] [8]
As their name implies, these fish use their fins to move around in a series of skips.
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 elongated 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 an 'intra-fin' joint where the radials meet the rays. [7] 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.
Mudskippers have 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 that they keep themselves moist. The ability to breathe through their skin is associated with increased capillary density in their skin. [12] This mode of breathing, similar to that employed by amphibians, is known as cutaneous respiration. [6] 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, due to a ventromedial valve of the gill slit, keeping the gills moist, and allowing them to function while exposed to air. Gill filaments are stiff and do not coalesce when out of water. [6]
The different species have adapted to various diets on the mudflats. Boleophthalmus boddarti is detritivorous, while others will eat small crabs, insects, snails and even other mudskippers. [13]
Digging deep burrows in soft sediments allows the fish to thermoregulate, [14] avoid marine predators during the high tide when the fish and burrow are submerged, [15] and lay their eggs. [16] When the burrow is submerged, several mudskipper species maintain an air pocket inside it, which allows them to breathe in conditions of very low oxygen concentration. [17] [18] [19]
To reduce toxic ammonia production, mudskippers can suppress amino acid breakdown when exposed to air. [20] Another method they use involves the partial breakdown of amino acids leading to the production of alanine, which also reduces ammonia production. [20]
Mudskippers can reduce the membrane permeability of their skin and acidify the water in their burrows to reduce levels of ammonia from the environment. [21] [22]
Mudskippers evolved the ability to blink independently from terrestrial tetrapods. Their eyes are located high on their head compared to other gobies, and they blink by lowering their eyes as a membrane called the dermal cup rises to cover them. Although other fully aquatic goby species do not have the ability to blink, mudskippers did not evolve different muscles or glands to blink with; their blinking is accomplished with the same muscles in a different configuration. Rather than having specialized glands to produce eye lubricant, the fluid film on their cornea is likely composed of mucus secreted by their skin and water from their environment, possibly stored in the infraorbital space behind the dermal cup membrane. Mudskippers likely evolved blinking in response to conditions of terrestrial life, such as to keep their eyes wet out of water (they blink more frequently in high evaporation conditions and only when colliding with things in water) and to clean and protect the eye from debris, which may adhere to the eye or approach at a faster, more dangerous speed when in air versus when in water. Their eyes are not elevated when they are still juveniles, which are fully aquatic. [23]
The genus Periophthalmus is by far the most diverse and widespread genus of mudskipper. Eighteen species have been described. [24] [25] [26] 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, Taiwan, and the Ryukyus, to Samoa and Tonga Islands. [3] It grows to a length of about 9.5 cm [3] and is a carnivorous opportunist feeder. It feeds on small prey such as small crabs and other arthropods. [27] However, a recent molecular study suggests that P. argentilineatus is in fact a complex of species, with at least three separate lineages, one in East Africa, and two in the Indo-Malayan region. [28] Another species, Periophthalmus barbarus , is the only oxudercine goby that inhabits the coastal areas of western Africa. [3]
Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the tetrapods. The mouths of lungfish typically bear tooth plates, which are used to crush hard shelled organisms.
Gobiidae or gobies is a family of bony fish in the order Gobiiformes, one of the largest fish families comprising more than 2,000 species in more than 200 genera. Most of gobiid fish are relatively small, typically less than 10 cm (3.9 in) in length, and the family includes some of the smallest vertebrates in the world, such as Trimmatom nanus and Pandaka pygmaea, Trimmatom nanus are under 1 cm long when fully grown, then Pandaka pygmaea standard length are 9 mm (0.35 in), maximum known standard length are 11 mm (0.43 in). Some large gobies can reach over 30 cm (0.98 ft) in length, but that is exceptional. Generally, they are benthic or bottom-dwellers. Although few are important as food fish for humans, they are of great significance as prey species for other commercially important fish such as cod, haddock, sea bass and flatfish. Several gobiids are also of interest as aquarium fish, such as the dartfish of the genus Ptereleotris. Phylogenetic relationships of gobiids have been studied using molecular data.
Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body and tail in the water, and in various specialised fish by motions of the fins. The major forms of locomotion in fish are:
Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits, a process known as convergent evolution. These fish use a range of methods for land movement, such as lateral undulation, tripod-like walking, and jumping. Many of these methods of locomotion incorporate multiple combinations of pectoral-, pelvic-, and tail-fin movement.
A walking fish, or ambulatory fish, is a fish that is able to travel over land for extended periods of time. Some other modes of non-standard fish locomotion include "walking" along the sea floor, for example, in handfish or frogfish.
Elacatinus is a genus of small marine gobies, often known collectively as the neon gobies. Although only one species, E. oceanops, is technically the "neon goby", because of their similar appearance, other members of the genus are generally labeled neon gobies, as well. Except for a single East Pacific species, all reside in warmer parts of the West Atlantic, including the Caribbean and Gulf of Mexico. They are known for engaging in symbiosis with other marine creatures by providing them cleaning service that consists of getting rid of ectoparasites on their bodies. In return, Elacatinus species obtain their primary source of food, ectoparasites.
The Gobiiformes are an order of fish that includes the gobies and their relatives. The order, which was previously considered a suborder of Perciformes, is made up of about 2,211 species that are divided between seven families. Phylogenetic relationships of the Gobiiformes have been elucidated using molecular data. Gobiiforms are primarily small species that live in marine water, but roughly 10% of these species inhabit fresh water. This order is composed chiefly of benthic or burrowing species; like many other benthic fishes, most gobiiforms do not have a gas bladder or any other means of controlling their buoyancy in water, so they must spend most of their time on or near the bottom. Gobiiformes means "goby-like".
Periophthalmus is a genus of fish in the family Oxudercidae that is native to coastal mangrove woods and shrubland in the Indo-Pacific region, except for P. barbarus, which lives on the Atlantic coast of Africa. It is one of the genera commonly known as mudskippers. Periophthalmus fishes are remarkable for using limited terrestrial locomotion and jumping to live temporarily out of water to feed on insects and small invertebrates. All Periophthalmus species are aggressive and territorial.
Fin and flipper locomotion occurs mostly in aquatic locomotion, and rarely in terrestrial locomotion. From the three common states of matter — gas, liquid and solid, these appendages are adapted for liquids, mostly fresh or saltwater and used in locomotion, steering and balancing of the body. Locomotion is important in order to escape predators, acquire food, find mates and bury for shelter, nest or food. Aquatic locomotion consists of swimming, whereas terrestrial locomotion encompasses walking, 'crutching', jumping, digging as well as covering. Some animals such as sea turtles and mudskippers use these two environments for different purposes, for example using the land for nesting, and the sea to hunt for food.
The Atlantic mudskipper is a species of mudskipper native to fresh, marine, and brackish waters of the tropical Atlantic coasts of Africa, including most offshore islands, through the Indian Ocean and into the western Pacific Ocean to Guam. The Greek scientific name Periophthalmus barbarus is named after the eyes that provide the Atlantic mudskipper with a wide field of vision. The Atlantic mudskipper is a member of the genus Periophthalmus, which includes oxudercine gobies that have one row of canine-like teeth.
Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only by muscles.
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. Tetrapods are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals. While most species today are terrestrial, little evidence supports the idea that any of the earliest tetrapods could move about on land, as their limbs could not have held their midsections off the ground and the known trackways do not indicate they dragged their bellies around. Presumably, the tracks were made by animals walking along the bottoms of shallow bodies of water. The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear. They are areas of active research and debate among palaeontologists at present.
Platygobiopsis is a genus of gobies native to the western Pacific Ocean.
Darwin's mudskipper is a relatively newly discovered mudskipper in 2004, so little is known about it. It is a brackish water ray-finned fish found in Australia along mud banks never far from mangrove trees. It is in the goby family Gobiidae. It is named after Charles Darwin because the holotype was collected in Darwin Harbour. Its greatest distinguishing characteristic from other mudskippers is its greatly reduced first dorsal fin in both sexes.
Oxudercidae is a family of gobies which consists of four subfamilies which were formerly classified under the family Gobiidae. The family is sometimes called the Gobionellidae, but Oxudercidae has priority. The species in this family have a cosmopolitan distribution in temperate and tropical areas and are found in marine and freshwater environments, typically in inshore, euryhaline areas with silt and sand substrates.
Periophthalmodon septemradiatus is a species of mudskipper found along tropical shorelines of the eastern Indian Ocean where it occurs in marine, brackish and fresh waters from India to Mekong Delta Vietnam, Indonesia. It is found along in estuaries as well as in the rivers.
Communication occurs when an animal produces a signal and uses it to influences the behaviour of another animal. A signal can be any behavioural, structural or physiological trait that has evolved specifically to carry information about the sender and/or the external environment and to stimulate the sensory system of the receiver to change their behaviour. A signal is different from a cue in that cues are informational traits that have not been selected for communication purposes. For example, if an alerted bird gives a warning call to a predator and causes the predator to give up the hunt, the bird is using the sound as a signal to communicate its awareness to the predator. On the other hand, if a rat forages in the leaves and makes a sound that attracts a predator, the sound itself is a cue and the interaction is not considered a communication attempt.
Boleophthalmus pectinirostris, commonly known as the great blue spotted mudskipper, is a species of mudskipper native to the north-western Pacific Ocean. It can be found on the coastlines of Japan, eastern China, Sumatra, Malaysia, Taiwan and the Korean Peninsula.
Boleophthalmus boddarti, commonly known as Boddart's goggle-eyed goby, is a species of mudskipper native to the Indo-Pacific, and the type species of the genus Boleophthalmus.
Boleophthalmus birdsongi, also known as Birdsong's goggle-eyed goby, North Australian great mudskipper, and Birdsong's mudskipper, is a species of mudskipper. It occurs in the mudflats of Northern Territory, Australia.