Gobies (phylum Chordata, subphylum Vertebrata, superclass Osteichthyes, class Actinopterygii, order Perciformes, family Gobiidae) are mostly fishes with short and broad heads, and the eyes are usually located either on top of the head or high up by the sides. They are generally bottom dwellers, and hence the higher location of the eyes allows them to have a good view of the surrounding.
Many species can survive well in both brackish and sea water, while some may spend their entire lives in freshwater. Several species form symbiotic relationships and live with other organisms, such as shrimps, corals and other fishes - they may aid in the detection of threats, remove parasites, or protect their hosts from predators. Some species, e.g. the mudskippers, can survive for long periods out of water by holding water in their gill chambers and/or breathing through the skin. During the breeding season, the males will usually guard and tend to the eggs.
Here are some examples of marine gobies that can be seen in Singapore.
A) SUBFAMILY OXUDERCINAE
Members of this subfamily are commonly referred to as mudskippers, due to their amphibious habits and their ability to "skip" along over the muddy substrate. These fishes are able to survive for short periods out of the water by holding water in their gill chambers, but have to replenish the water when the oxygen runs out. They are also able to breathe through their skin if they keep it moist. The pelvic fins on the underside are united into a disc-like structure, functioning somewhat like a suction cup which helps them to cling on to the roots and branches of mangrove trees, allowing them to even climb up the lower parts of trees. They also have a muscular body, allowing them to skip over the substrate and even pounce on their prey. Most of the time, however, they just use their pectoral fins to push their body forward and walk around. Being bottom dwellers, their eyes are on top of the head to give them a good view of the surrounding to look out for both prey and predators. Their colours are usually dull, so as to blend into the surrounding. They are generally found in coastal areas, and are able to tolerate brackish and sometimes even fresh waters.
The Giant Mudskipper (Periophthalmodon schlosseri) is the biggest mudskipper in Singapore, growing to about 27cm long. Apart from its size, it can be recognised by the pair of black stripes running along the upperside from the eye to the tail, and pale blue speckles on the cheek. This carnivorous species feeds on other smaller animals, usually crustaceans or worms on the mudflat.
The Yellow-spotted Mudskipper (Periophthalmus walailakae) can be mistaken for juveniles of the previous species, but lacks the bluish-white speckles on the cheeks and instead, is covered in yellowish spots all over. The body is greyish to brownish, often with darker blotches. The first dorsal fin is reddish. This species grows to about 13cm long, and is carnivorous. It is usually seen on mudflats and in mangrove forests.
The Gold-spotted Mudskipper (Periophthalmus chrysospilos) has greyish brown upperparts and pale underparts, usually marked with numerous orange spots. The back may have several broad darker bands. This carnivorous species feeds on small invertebrates, and is usually found in groups on rocks and sandy shorelines. It grows to about 12cm long.
The Blue-spotted Mudskipper (Boleophthalmus boddarti) can be recognised by the numerous bluish spots on its brownish body. The upperparts are often marked with several dark bars, and a dark stripe is often seen on the sides. It is usually found on the mudflat, constantly moving its head left-and-right, feeding on the algae and detritus on the surface. This species gets to about 22cm long.
B) SUBFAMILY GOBIINAE
Members of this subfamily are commonly called the true gobies. Like the mudskippers, many of the true gobies have had their pelvic fins modified into a suction cup which allows them to hold on to the substrate. They have two dorsal fins - a spiny one in front and a soft one behind, similar to the mudskippers as well, but unlike the latter, they are not amphibious. They are marine species, though some species can tolerate brackish waters as well. The eyes are usually located high on the sides of the head, but seldom sticking out all the way at the top of the head, unlike the mudskippers.
The Head-stripe Goby (Amblygobius stethophthalmus) can be recognised by the thin blue stripes and yellowish to brownish bands on its head. It feeds on algae and small invertebrates, growing to about 8cm long.
The Shadow Goby (Acentrogobius nebulosus) is one of the few poisonous gobies, possessing a toxin similar to those found in pufferfishes. It can be identified by the large rounded blackish blotches along the sides, the large eyes and the brownish spots on a pale body. This species appears to tolerate heat well, and can be seen in shallow pools on hot days. It grows to about 12cm long.
The Slender-lined Shrimp-goby (Cryptocentrus leptocephalus) has six pinkish oblique bars on its reddish and green body. The head is covered in numerous pink and blue spots and blotches. This goby is usually found living with snapping shrimps (Alpheus spp.), sharing their burrows. The relationship is believed to be mutualistic, as the shrimps build and maintain the burrow, while the gobies which have better eyesight keep a lookout for threats. Usually, the shrimp will maintain contact with the goby using one of its antennae. This shrimp-goby gets to about 8cm long.
The Crocodile Flathead Goby (Psammogobius biocellatus) has a heavily pigmented head with a light stripe from the eye to the upper jaw. In addition, it has a protruding lower jaw and a pointed snout. The adults have lines of blackish spots along the sides of the body. This species grows to about 8cm long.
The Reiche's Sand-goby (Favonigobius reichei) can be recognised by the pair of black spots that are joined to each other at the base of the tail fin. The body is whitish but covered in small yellow, reddish and brownish spots. This species grows to about 7cm long.
The above is likely to be an Ornate Lagoon-goby (Istigobius ornatus), which has pale yellowish head and body with black, yellow, blue and red markings. It has two obvious rows of blackish spots along the sides of the body. This species can grow to about 8cm long.
References
Many species can survive well in both brackish and sea water, while some may spend their entire lives in freshwater. Several species form symbiotic relationships and live with other organisms, such as shrimps, corals and other fishes - they may aid in the detection of threats, remove parasites, or protect their hosts from predators. Some species, e.g. the mudskippers, can survive for long periods out of water by holding water in their gill chambers and/or breathing through the skin. During the breeding season, the males will usually guard and tend to the eggs.
Here are some examples of marine gobies that can be seen in Singapore.
A) SUBFAMILY OXUDERCINAE
Members of this subfamily are commonly referred to as mudskippers, due to their amphibious habits and their ability to "skip" along over the muddy substrate. These fishes are able to survive for short periods out of the water by holding water in their gill chambers, but have to replenish the water when the oxygen runs out. They are also able to breathe through their skin if they keep it moist. The pelvic fins on the underside are united into a disc-like structure, functioning somewhat like a suction cup which helps them to cling on to the roots and branches of mangrove trees, allowing them to even climb up the lower parts of trees. They also have a muscular body, allowing them to skip over the substrate and even pounce on their prey. Most of the time, however, they just use their pectoral fins to push their body forward and walk around. Being bottom dwellers, their eyes are on top of the head to give them a good view of the surrounding to look out for both prey and predators. Their colours are usually dull, so as to blend into the surrounding. They are generally found in coastal areas, and are able to tolerate brackish and sometimes even fresh waters.
The Giant Mudskipper (Periophthalmodon schlosseri) is the biggest mudskipper in Singapore, growing to about 27cm long. Apart from its size, it can be recognised by the pair of black stripes running along the upperside from the eye to the tail, and pale blue speckles on the cheek. This carnivorous species feeds on other smaller animals, usually crustaceans or worms on the mudflat.
The Yellow-spotted Mudskipper (Periophthalmus walailakae) can be mistaken for juveniles of the previous species, but lacks the bluish-white speckles on the cheeks and instead, is covered in yellowish spots all over. The body is greyish to brownish, often with darker blotches. The first dorsal fin is reddish. This species grows to about 13cm long, and is carnivorous. It is usually seen on mudflats and in mangrove forests.
The Gold-spotted Mudskipper (Periophthalmus chrysospilos) has greyish brown upperparts and pale underparts, usually marked with numerous orange spots. The back may have several broad darker bands. This carnivorous species feeds on small invertebrates, and is usually found in groups on rocks and sandy shorelines. It grows to about 12cm long.
The Blue-spotted Mudskipper (Boleophthalmus boddarti) can be recognised by the numerous bluish spots on its brownish body. The upperparts are often marked with several dark bars, and a dark stripe is often seen on the sides. It is usually found on the mudflat, constantly moving its head left-and-right, feeding on the algae and detritus on the surface. This species gets to about 22cm long.
B) SUBFAMILY GOBIINAE
Members of this subfamily are commonly called the true gobies. Like the mudskippers, many of the true gobies have had their pelvic fins modified into a suction cup which allows them to hold on to the substrate. They have two dorsal fins - a spiny one in front and a soft one behind, similar to the mudskippers as well, but unlike the latter, they are not amphibious. They are marine species, though some species can tolerate brackish waters as well. The eyes are usually located high on the sides of the head, but seldom sticking out all the way at the top of the head, unlike the mudskippers.
The Head-stripe Goby (Amblygobius stethophthalmus) can be recognised by the thin blue stripes and yellowish to brownish bands on its head. It feeds on algae and small invertebrates, growing to about 8cm long.
The Shadow Goby (Acentrogobius nebulosus) is one of the few poisonous gobies, possessing a toxin similar to those found in pufferfishes. It can be identified by the large rounded blackish blotches along the sides, the large eyes and the brownish spots on a pale body. This species appears to tolerate heat well, and can be seen in shallow pools on hot days. It grows to about 12cm long.
The Slender-lined Shrimp-goby (Cryptocentrus leptocephalus) has six pinkish oblique bars on its reddish and green body. The head is covered in numerous pink and blue spots and blotches. This goby is usually found living with snapping shrimps (Alpheus spp.), sharing their burrows. The relationship is believed to be mutualistic, as the shrimps build and maintain the burrow, while the gobies which have better eyesight keep a lookout for threats. Usually, the shrimp will maintain contact with the goby using one of its antennae. This shrimp-goby gets to about 8cm long.
The Crocodile Flathead Goby (Psammogobius biocellatus) has a heavily pigmented head with a light stripe from the eye to the upper jaw. In addition, it has a protruding lower jaw and a pointed snout. The adults have lines of blackish spots along the sides of the body. This species grows to about 8cm long.
The Reiche's Sand-goby (Favonigobius reichei) can be recognised by the pair of black spots that are joined to each other at the base of the tail fin. The body is whitish but covered in small yellow, reddish and brownish spots. This species grows to about 7cm long.
The above is likely to be an Ornate Lagoon-goby (Istigobius ornatus), which has pale yellowish head and body with black, yellow, blue and red markings. It has two obvious rows of blackish spots along the sides of the body. This species can grow to about 8cm long.
References
- Allen, G. R. 1997. Marine fishes of South-east Asia. Periplus Editions, Hong Kong. 292 pp.
- Froese, R. & D. Pauly. Editors. 2013. FishBase, version (02/2013). Retrieved May 7, 2013, from http://www.fishbase.org.
- Kuiter, R. H. & H. Debelius. 2006. World atlas of marine fishes. IKAN-Unterwasserarchiv, Frankfurt. 720 pp.
- Lim, K.K.P & J. K. Y. Low. 1998. A guide to common marine fishes of Singapore. Singapore Science Centre, Singapore. 163 pp.
- Ng, P. K. L. & N. Sivasothi (eds.), 1999. A guide to the mangroves of Singapore II: animal diversity. Singapore Science Centre. 168p.
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