Black-ray goby
Encyclopedia
The black-ray Goby is a species of marine goby
and is a member of the family of high fin gobies. This type of goby is also sometimes attributed the common name "shrimp goby" or "watchman goby". This is due to the interesting symbiotic relationship that these gobies can form with Randall's pistol shrimp (Alpheus randalli
).
becoming more raised and pronounced in adulthood. This elongated fin is the most obvious distinguishing feature between the black-ray goby and its close cousin, the yellow snout goby (S. Xanthorhinica). The fish are beautifully coloured with four diagonal brown stripes across a white body, and a distinctive yellow head. See accompanying photograph for reference.
It is almost impossible for anybody less than a specialised expert in the specific field of these types of fish to discern differences between males and females of the species.
. In fact, it is in reality quite shy, and when first introduced into an aquarium, may take up to several weeks before it is bold enough to leave its hiding place, or bolt hole. Whilst this fish can display aggression towards other tank inhabitants by opening its mouth and "yawning" at them, this is mostly show, and the goby will quickly turn tail and hide if confronted.
The goby will spend most of its time hovering about two inches above its bolt hole, searching for scraps of food in the water column. If scared or startled, it will slowly retreat towards its hole. If the danger does not go away, it will dart inside at lightning speed.
Mated pairs of this fish are very rare and difficult to attain. Individual males may fight if placed in a tank smaller than about 50 gallons (~200 litres).
in the sand in which both live. Burrows usually measure up to one inch in diameter, and can reach up to four feet in length. The goby has much better eyesight than the shrimp, and, as such, acts as the watchman for both of them, keeping an eye out for danger. The two animals maintain continuous contact, with the shrimp placing one of its antennae
permanently on the goby's tail. When danger threatens, the goby will make continuous flicks of its tail, warning the shrimp there is a predator nearby, and the shrimp will remain safely in the burrow. If the danger reaches a certain level, the goby will dart into the burrow after the shrimp.
At night, the goby will go into the burrow, and the shrimp will collapse the entrance to close it off. The burrow is exited the next day by the goby blasting its way out and collapsing the burrow. The shrimp then spends the next day laboriously rebuilding the entrance to the burrow. Both animals have also been known to share food with each other.
In the wild, most burrows are shared by male and female goby pairs, with their respective shrimp partners, and the female goby will use this burrow as a nesting site to lay her eggs.
The obvious benefits to both organisms of this symbiotic
relationship make the interaction a form of mutualism. Here is an interesting example of this. The other fish is a dartfish
(genus Ptereleotris). These fish are often found as unwelcome but ignored guests sharing the burrow with goby and shrimp.
should be 1.023 - 1.025, with a pH
of 8.1 - 8.4; water temperature at 72 - 76°F / 22 - 25°C is ideal.
shrimp, along with flake food and algae wafers, spirulina, etc. are all happily accepted. In the wild, these gobies most often feed on zooplankton
. The water quality must be kept reasonably high, as with all marine species. A substrate
of small-grained coral sand, with larger particles mixed in (preferably four inches or deeper) is ideal for the goby/shrimp pair to make their burrow.
Information on shrimp-goby interaction
Goby
The gobies form the family Gobiidae, which is one of the largest families of fish, with more than 2,000 species in more than 200 genera. Most are relatively small, typically less than 10 cm in length...
and is a member of the family of high fin gobies. This type of goby is also sometimes attributed the common name "shrimp goby" or "watchman goby". This is due to the interesting symbiotic relationship that these gobies can form with Randall's pistol shrimp (Alpheus randalli
Alpheus randalli
Alpheus randalli is a species of snapping shrimp in the genus Alpheus. It lives in the Marquesas Islands and parts of the Indian Ocean, including the Seychelles, in association with gobies of the genus Amblyeleotris. The shrimp is transparent or white with prominent red markings....
).
Physical features
Adult fish can grow up to two inches in length, with the striking pointed dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
becoming more raised and pronounced in adulthood. This elongated fin is the most obvious distinguishing feature between the black-ray goby and its close cousin, the yellow snout goby (S. Xanthorhinica). The fish are beautifully coloured with four diagonal brown stripes across a white body, and a distinctive yellow head. See accompanying photograph for reference.
It is almost impossible for anybody less than a specialised expert in the specific field of these types of fish to discern differences between males and females of the species.
Behaviour and compatibility
This fish is very docile and poses almost no threat to any other stock inhabiting a typical marine aquarium. This passiveness makes it a perfect tankmate for delicate species like sea horses or pipefishPipefish
Pipefishes or pipe-fishes are a subfamily of small fishes, which, together with the seahorses, form the family Syngnathidae.-Anatomy:...
. In fact, it is in reality quite shy, and when first introduced into an aquarium, may take up to several weeks before it is bold enough to leave its hiding place, or bolt hole. Whilst this fish can display aggression towards other tank inhabitants by opening its mouth and "yawning" at them, this is mostly show, and the goby will quickly turn tail and hide if confronted.
The goby will spend most of its time hovering about two inches above its bolt hole, searching for scraps of food in the water column. If scared or startled, it will slowly retreat towards its hole. If the danger does not go away, it will dart inside at lightning speed.
Mated pairs of this fish are very rare and difficult to attain. Individual males may fight if placed in a tank smaller than about 50 gallons (~200 litres).
Relationship with pistol shrimp
This goby, along with the others of its genus are renowned for their remarkable relationship with Randall's shrimp (or candy-stripe pistol shrimp, Alpheus randalli). This particular genus of goby does not associate with any other type of shrimp in the wild.Behaviour
The shrimp spends the day digging a burrowBurrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
in the sand in which both live. Burrows usually measure up to one inch in diameter, and can reach up to four feet in length. The goby has much better eyesight than the shrimp, and, as such, acts as the watchman for both of them, keeping an eye out for danger. The two animals maintain continuous contact, with the shrimp placing one of its antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
permanently on the goby's tail. When danger threatens, the goby will make continuous flicks of its tail, warning the shrimp there is a predator nearby, and the shrimp will remain safely in the burrow. If the danger reaches a certain level, the goby will dart into the burrow after the shrimp.
At night, the goby will go into the burrow, and the shrimp will collapse the entrance to close it off. The burrow is exited the next day by the goby blasting its way out and collapsing the burrow. The shrimp then spends the next day laboriously rebuilding the entrance to the burrow. Both animals have also been known to share food with each other.
In the wild, most burrows are shared by male and female goby pairs, with their respective shrimp partners, and the female goby will use this burrow as a nesting site to lay her eggs.
The obvious benefits to both organisms of this symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
relationship make the interaction a form of mutualism. Here is an interesting example of this. The other fish is a dartfish
Dartfish
Dartfishes are a family, Ptereleotridae, of goby-like fishes in the order Perciformes. They are saltwater fish.The dartfishes were formerly classified as the subfamily Ptereleotrinae of the wormfishes, Microdesmidae, but this classification made Microdesmidae polyphyletic, hence the elevation to a...
(genus Ptereleotris). These fish are often found as unwelcome but ignored guests sharing the burrow with goby and shrimp.
Black-ray goby in commercial trade
This goby is in high demand for home and hobby marine aquaria due to its beautiful colouration, docile nature and interesting interaction with symbiotic shrimp. This type of goby is the most common Stonogobiops species to show up in the marine trade, but is still quite rare.Natural environment
This goby is commonly found in the western Indo-Pacific (Indonesia and the Philippines), inhabiting sandy bottoms and rocky outcrops at depths ranging from 60 to 100 feet.Tank environment
For successful aquarium culture, this fish needs good sand/coral rubble cover for burrow building and lots of rock cover; a reef environment is suitable. The recommended minimum tank size is 20 gallons (80 litres). It may be possible to keep these fish happily in smaller "nano reefs", but this is not advised. The water specific gravitySpecific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
should be 1.023 - 1.025, with a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of 8.1 - 8.4; water temperature at 72 - 76°F / 22 - 25°C is ideal.
Care and maintenance
Small meaty foods, such as mysid (sometimes referred to as mysis shrimp) or brineBrine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...
shrimp, along with flake food and algae wafers, spirulina, etc. are all happily accepted. In the wild, these gobies most often feed on zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. The water quality must be kept reasonably high, as with all marine species. A substrate
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
of small-grained coral sand, with larger particles mixed in (preferably four inches or deeper) is ideal for the goby/shrimp pair to make their burrow.
External links
General information- General information on this type of goby, from About.com
- Some general/taxonomic info
- Wetwetmedia.com link, contains some useful information, along with helpful FAQs
Information on shrimp-goby interaction
- Interesting information on a parallel relationship between other goby/shrimp types in the Atlantic
- Excellent general information on this goby, and the Stonogobiops genus in general, along with their mutualism with pistol shrimp
- - An interesting study analysing daily shrimp activity cycles, the effects of goby presence on shrimp behavior, and the effects of predation on numerical density and size of gobies