#gobiiformes

The Nurseryfish (Kurtus gulliveri) is so named for carrying their egg clusters on hooks protruding from the forehead of the males. Females do not have these hooks, and the hooks of their relative, the Indian Humphead (Kurtus indicus), are too small.

Some species of male cardinalfish (family Apogonidae) brood their eggs inside their mouths. They do not eat for the whole incubation period.

While most cardinalfish hide in rocky crevices during the day, they are well-known for also using the spines of sea urchins (particularly of the genus Diadema) as shelter.

The Conchfish (Astrapogon stellatus) is a species of cardinalfish so named because it will hide inside the mantle cavity of a living Queen Conch (Aliger gigas) by day. This does not harm the conch. Unfortunately, the Queen Conch is becoming increasingly rare because of over-fishing for its meat and shells, so some Conchfish have been reported to use Rigid Pen Shells (Atrina rigida) and Amber Pen Shells (Pinna carnea) as alternative refuges.

The Mouth Almighty (Glossamia aprion) is a cardinalfish which seems to have been named for its large mouth, used for ambush predation (but also mouthbrooding).

The Banggai Cardinalfish (Pterapogon kauderni) (image 3) is likely the most famous member of the cardinalfish family, due to its popularity in the aquarium trade. It is among the relatively few marine fish to have been bred regularly in captivity, but significant numbers are still captured in the wild to boost the trade, and it is now an endangered species.

Sand Divers (genus Trichonotus) (image 4) are small, wormlike fish which do exactly as their name suggests. When alarmed, the fish dive into the sand and remain stationary with just the upper parts of their head protruding from the sediment. If further disturbed, they will erupt from the sand and swim a short distance before submerging themselves again. Male sand divers are larger, and have a harem of females. Courtship involves erecting their dorsal fin while they lower their pelvic and anal fins.

All species of blind cave goby (family Milyeringidae), like many other unrelated species of cavefish, have no eyes and most lack pigment, using sensory papillae on their head and body to move around and find food. Most species are considered endangered or critically endangered, due to their restricted ranges in only some caves and aquifers, which are often in danger of pollution seeping through groundwater.

The Oaxaca Cave Sleeper (Caecieleotris morrisi) is the only cavefish in the family Eleotridae. Or, was. The Oaxaca Cave Sleeper was last seen in 1990, and its cave was since flooded by the building of a dam. Recent surveys have not been able to relocate the species, and it may be extinct.

The Peacock Gudgeon (Tateurndina ocellicauda) is known for its spectacular coloration and sexual dimorphism. Both males and females are colorful, but males are slightly moreso, and also develop a large nuchal hump on their foreheads to advertise their breeding status. Females are also more streamlined, while males are more rounded. These fish took the animated-movie-sexual-dimorphism route.

The Marble Goby (Oxyeleotris marmorata) is one of the largest gobiiformes, reaching a length of 65 cm (2 ft) (though most do not exceed 30 cm (1 ft)). This impressive size for a gobiiforme has turned the species into an economically important fish, being sought after by local commercial fisheries and farmed. It is highly popular among the Chinese community due to its fine texture and tasty white flesh, and is believed to have healing properties. It may also be the fish featured in the folk tale of the Golden Goby, Pla Boo Thong, a dark Cinderella-like tale from Thailand.

Mudskippers (subfamily Oxudercinae) (image 2) are some of the most famous “air-breathing” Actinopterygiians. They live in burrows in moist, muddy environments, and can even climb low-hanging tree branches and shrubs. They can breathe on land by storing water inside their large gill chambers. They are also able to absorb oxygen from the lining of their mouth and throat. Mudskippers may spend up to three quarters of their life on land. They can also leap up to 61 centimetres (2 feet) high by laterally flexing and pushing with their tails, which males do to attract females.

The most distinctive aspect of true goby (family Gobiidae) anatomy are their fused pelvic fins that form a disc-shaped sucker. The sucker is similar to the dorsal fin sucker of remoras and the pelvic fin sucker of lumpsuckers, but is anatomically distinct and the product of convergent evolution. Species in this family can often be seen using their sucker to adhere to rocks and corals, and in aquariums they will stick to glass walls of the tank as well.

Some of the smallest vertebrates in the world are gobies, including the Midget Dwarfgoby (Trimmatom nanus) which grows up to 1 centimetre (0.39 in) long, and the Dwarf Pygmy Goby (Pandaka pygmaea) whose larger females grow up to 1.5 centimetres (0.59 in) long.

Many species in the Gobiidae live in male-female pairs that construct and share burrows. The burrows are used for shelters and spawning places. They use their mouths to dig into the sea bottom, removing dead coral-fragments, rubble, and algae in order to build their burrows, then use coral rubble to block the burrow entrance. A single goby can carry as many as nine pieces of coral rubble per minute. Some species mate for life. Females prefer male gobies with large bodies, so smaller males may employ the “sneaker male” strategy, and sneak into a pairs’ burrow to fertilize their eggs.

Some gobies, such as Blackeye Gobies (Rhinogobiops nicholsii) and Blue-banded Gobies (Lythrypnus dalli), can change their sex, since the external genitalia for males and females do not differ much. Sex changes can take from days to weeks. Most sex changes in gobies are from female to male (protogyny) rather than male to female (protandry). This usually happens in goby species that live in harems, with one lead male and a small group of females. Female-to-male change usually occurs because the resident male of the group has died. Therefore, the dominant female turns into a male, allowing the group to continue reproducing. Male-to-female change may occur when the females all have a preference for larger males. Small males either choose to become sneakers (kleptogamy) or choose to transform into females to get more mating opportunities.

The Broad-barred Goby (Gobiodon histrio) is one of the very few species that can change sex both ways. When two MTF Broad-barred Gobies are on the same coral reef, one of them will transform back into a male goby.

The Broad-barred Goby is also capable of releasing a toxic compound to escape from predators. The compound inhibits the locomotion of other fish. At high enough concentrations, the toxin causes the predator to lose equilibrium and tip over. The goby achieves this through a mutualistic relationship with a species of coral, Acropora nasuta. When the coral is being damaged by toxic Chlorodesmis algae, it produces a compound that attracts the Broad-barred Goby. The fish eat the alga and this enhances its toxicity.

Neon Gobies (genus Elacatinus) are known for engaging in symbiosis with other marine creatures by providing them a cleaning service that consists of eating ectoparasites off their bodies.

Shrimpgobies (genus Amblyeleotris) (image 1 and gif below) are named for their symbiotic relationship with certain alpheid shrimps. The shrimp excavates and maintains a burrow used by both animals while the goby, which has far superior eyesight, acts as a lookout for predators. The shrimp maintains almost constant contact with the fish with an antenna. Fossil Amblyeleotris otoliths have been found together with alpheid shrimp remnants from as early as the early Miocene, suggesting a possible mutualistic relationship since then.