Back in 1998 a new species of goby started to appear in the marine aquarium trade with some regularity. It was much different than any goby seen previously, so naturally it garnered attention. Names such as White ray goby or Yasha Hashe goby began to circulate amongst the internet hobbyists and wholesalers alike. In either instance, everyone has been quick to also label it the name of the genus, Stonogobiops. For many years this was the most definitive name we could offer outside of the common names our local retailers provided. However, this all changed in 2001 when a pair of scientists awarded the newest member of Stonogobiops with a valid species name.(Yoshino and Shimada, 2001). The most observant of goby aficionados may have just needed to read the previous sentence twice. Yes, I did just say 2001. So, why is it as recent as 2003 authors and hobbyists are still referring to Yasha Hashe as Stonogobiops sp.? Are they just trying to make Eric Borneman proud? Sorry, but we are not discussing Acropora sp.; this is a fish. We should be more than capable of referring to the species name during any discussion. So what is my New Year's resolution for 2004? I wish to get hobbyists across the world to stop referring to the Whiteray Shrimp goby as Stonogobiops sp. and to start calling it Stonogobiops yasha.

Meet the Family

The Gobiidae is the largest family of marine fish with over 2,000 members and it is still growing. Most Gobiidae are characterized by a few notable attributes. Other than the few gobies that swim above the substrate, most lack a swim bladder and lateral line. However, gobies have sensory ducts around their heads that make up for the loss of the lateral line (Smith and Knopf, 1997). Another interesting characteristic is the condition of the ventral fins, which in most gobies have joined together and developed small suction cups on the end. Also, every goby is a demersal spawner with most species having both parents acting as guardians over the eggs (Smith and Knopf, 1997). Some gobies will even produce sounds during courtship or territory disputes (CIBRA)!

Stonogobiops is considered to be a relatively new genus as it wasn't raised to generic status until Polunin and Lubbock (1977) described Stonogobiops dracula. In Hoese and Randall (1982) three additional species were added to the genus, followed by one species in Iwata and Hirata (1994) and finally the last species (for now) in the aforementioned Yoshino and Shimada (2001), which brings the total number of Stonogobiops species to six.

The relatively young age lends some assistance in keeping the genus fairly well organized. However, a shared characteristic belonging to several goby genera has assisted to keep little confusion in this genus. Unlike most gobies, Stonogobiops species have "vomerine teeth." These are teeth that are present on the vomer, a thin bone along the roof of the mouth. Eighteen genera of gobies were said to have vomerine teeth, but in fact the exact number has been found to be considerably less (see below). The species that were determined to not have vomerine teeth in fact had a vomerine that extended into the mouth. This abnormal vomerine extension was likely mistaken for vomerine teeth in their original description (Hoese and Randall, 1982).

In addition to the above genera, three additional genera have been noted to have vomerine teeth. Unfortunately, I was unable to locate any additional information on these unnamed genera. Therefore, I feel it is important to note the species which were initially reported to have vomerine teeth, but further research has proven they do not have vomerine teeth (see below).

In addition to the teeth on the vomer, Stonogobiops is noted to be one of the few genera of gobies that has a swim bladder. Additionally, it differs from its closest relative, the genus Cryptocentrus, by having a different pore pattern and reduction of sensory papillae on the head.

Stonogobiops is one genus of a small group of genera often referred to as "shrimp-gobies" or "watchman gobies." This is because these fish act as guardians over shrimp of the genus Alpheus. This symbiotic relationship will be discussed in detail below.

In the Wild

Stonogobiops species are represented in both the Indian and Pacific Oceans. However, the geographical distribution of each species is fairly limited. The most commonly occurring species, S. nematodes, is only common around the Philippine Island region. Stonogobiops dracula is the only member from the Indian Ocean, more specifically the Maldives and Seychelles. Stonogobiops xanthorhinica has the widest distribution stretching from Japan to the Northern coast of Australia. Stonogobiops medon maintains the eastern-most distribution, known only from the Marquesas Island area. It is not unusual for members of Stonogobiops to associate nearby other members of the watchman clan. For instance, S. dracula has been noted to live near members of the genus Amblyeleotris.

	Stonogobiops nematodes is the most common of the Stonogobiops to make it into the marine aquarium trade. Photos courtesy of Greg Rothschild (top left), Scott Chevalier (top right) and Philippe Goudket (left).

Most members of this genus are commonly found ranging from 60 to 100 feet. However, S. xanthorhinica can be found as shallow as 20 feet and as deep as 160 feet. At these depths individuals of Stonogobiops species will seek out protected rubble zones edging areas of white sand. Again, unlike most gobies, they utilize their swim bladder by hovering merely an inch or two above the substrate and only two to four inches outside of their burrow.

We should be as lucky as these fish; they never have to maintain or clean their home. Instead, they partake in a unique symbiotic relationship referred to as "mutualism" along with snapping shrimp, often called pistol shrimp, from the genus Alpheus. The term mutualism is derived from both members of the symbiotic relationship having something to gain from the other member. In this instance, the goby, unable to dig its own burrow, lives in the elaborate tunnels constructed by the shrimp. It will utilize these burrows each night when it retires for the evening or anytime danger is present in the nearby vicinity. The shrimp, being nearly blind, is an easy target of predators when it must exit its burrow to remove sand or mud from the burrow. To repay the shrimp for use of the burrow, the goby acts as the guardian of the burrow and warns the shrimp anytime danger approaches. This relationship can begin shortly after the goby settles from planktonic life, which occurs at roughly half an inch in length. An interesting video of the relationship can be seen here.

As may be seen in the above video, wormfish from the genus Ptereleotris are often found as unwelcomed, yet ignored, guests sharing the burrow with the goby and shrimp. Photo courtesy of Jun Harada.

Burrows usually measure up to one inch in diameter, may reach up to six inches of depth beneath the surface, and can stretch for up to four or more feet. Stonogobiops are always found as male/female pairs, so there is usually a pair of gobies and often a pair of pistol shrimp living within this cave. In most instances only one entrance/exit is extensively used; however, the constant shifting and settling of the upper layers of sediment requires regular maintenance by the shrimp. It is not unusual for additional entrances/exits to be in either the beginning phases of construction or slowly becoming sealed off over time.

Every time the shrimp needs to push sand and debris out of the burrow, or to search for the detrital material it will consume, it makes physical contact with the guardian goby. As can be seen in several of the photos in this article (here and here), the shrimp will use their antennae and touch the skin of the goby. If all is well, the shrimp will continue pushing sand out of the burrow and pile it just outside the entrance. However, if danger approaches, the goby will begin fluttering its caudal fin, thereby warning the shrimp (Preston, 1978; Karplus, 1979). If the shrimp was attempting to remove sand from the burrow or attempting to forage the nearby vicinity for a meal, it will now wait just inside the burrow until the danger is no longer present. If the shrimp is outside of the burrow at this time, it quickly retreats within the burrow. When the threat of danger escalates, the fish is known to position itself such that its tail is blocking the entrance to the burrow. Under maximum threat, the fish will quickly spin around and dart head first into the burrow. Of course, the shrimp is first to enter the burrow if both the shrimp and fish were outside of the burrow at the time the threat was noticed. For both the shrimp and goby to bolt into the burrow takes less than several tenths of a second.

The shrimp will collapse the entrance each night after all the occupants are inside. This serves as protection from animals that are able to slither into the burrow and capture their prey, such as Myrichthys maculosus, the spotted snake eel. Every morning the goby will burst through the collapsed entrance and the shrimp will begin the arduous task of rebuilding the entrance for the following day. Once all the maintenance duties are completed, the shrimp will begin foraging for food and feeding.

There are additional benefits to the goby in this relationship. The female goby uses the burrow as a nesting place for her eggs. Because of this, unfortunately, little is known about the mating ritual of this fish species. Lastly, the shrimp has also been noted to use the smaller of its two claws in actions similar to cleaning as it works over the goby's dorsal fin and caudal fin, possibly cleaning the fish of parasites (Karplus et al, 1972).

The goby always takes its food from the water column. While the fish hovers outside the burrow it is on constant watch for not only predators, but also prey. Prey items typically consist of most anything fitting under the classification of zooplankton. The goby will dart up to one or two feet from the burrow in an attempt to capture prey, always quick to return back to the burrow's entrance immediately after capturing the food item.

There are no readily apparent external differences hobbyists can use to differentiate between sexes. In some instances, pairs have been collected from the wild where the male is the larger member, while in other instances it is the female that is the largest. There have been reports (Baensch, 1994) of using the dorsal spine as a means to indicate the sex of the animal, but after reviewing the research data for this species, that would seem a highly unreliable characteristic. For all intents and purposes, there is no way a hobbyist can tell the difference between male and female Stonogobiops while the animal is still alive.

In the Home Aquarium

Stonogobiops species are relatively easy to care for provided their few requirements are met. Obviously of first thought is their relationship with the shrimp. Hobbyists love these relationships, and this one is no different. The good news is that this is a relationship which can be enjoyed in the home aquarium. Sadly, the bad news is that the symbiotic pistol shrimp rarely gets shipped in with the gobies, forcing hobbyists to find one on their own. The shrimp are considerably more difficult to capture and hence usually do not accompany their finned friends. Luckily, the gobies will do just fine in the home aquarium without their shrimp companion. Both the gobies and the shrimp can be very particular about whom they enter into a relationship with, however, so it may be best to avoid trying to pair up the two if they are acquired separately. Oftentimes, gobies will only pair up with one particular species of pistol shrimp, usually, but not always, Alpheus randalli (Hoese and Randall, 1982), as seen in the three photos below. Also, because the goby rarely leaves its burrow by more than one or two feet and the shrimp is most often tucked deeply into the burrow, the two are not likely to locate each other if introduced separately to the aquarium. So, try to acquire the goby and the shrimp at the same time as a pair if you hope to witness this fascinating relationship.

The best setting for a Stonogobiops and their shrimp companion would include a mixed rubble substrate combined with a traditional deep sand bed. The four-inch or deeper sand will afford the shrimp an opportunity to dig and create tunnels as it would naturally in the wild and the rubble will help provide some stabilty for the tunnels. To assist with acclimation it may behoove the hobbyist to bury a piece of PVC underneath the sandbed and utilize a 45 degree bend that breaks the surface of the sand. Place the shrimp in a clear plastic specimen container and keep the open top covered so the shrimp cannot swim out. A large fish net works well for this. Place the container over the open PVC pipe and flip the container upside down such that the open end of the container is now lying down in the sand. Remove the net from the underside and weigh down the container if needed. Within a minute or two the shrimp should find the open end of the PVC and quickly disappear down inside. Once this has occurred, repeat the process with the shrimp-goby. Acclimating using this procedure will ensure the goby and shrimp locate each other, and will give them a head start at building their burrow in the "prime real estate" chosen by the aquarist. Naturally, finding a burrow immediately will also reduce the stress involved with being moved into a new aquarium. If the goby is acquired without the symbiotic partner, it may still be best to utilize the PVC pipe idea; however, a deep sand bed is not important to the captive care of the goby. The deep sand bed is only useful to the maintenance of the pistol shrimp. If PVC is not used or not taken up by the fish or shrimp, a traditional sand bed doesn't really work well. The sands collapse too easily, and the presence of some small rubble or gravel like crushed coral or live rock chips will help reinforce the walls.

Acclimation to aquarium life is a slow battle for this goby. It may take a month or more before the aquarist can expect to see the goby with any regularity. Naturally, with a small, delicate goby such as this, one of the biggest factors in successful acclimation and maintenance is limiting its tank mates. Fast swimming or aggressive tank mates will all but eliminate any chance at success. Aggressive tank mates will obviously keep this goby tucked inside its preferred bolt hole, while fast swimming fishes will undoubtedly do the same. Unfortunately, these fish are also known to be jumpers when frightened, yet another reason to keep the fish load more passive. Aggressive feeders, such as surgeonfish or many of the wrasses, will make it difficult to get enough of the proper foods within striking range of the goby. If the plan is to maintain both the shrimp and goby as a pair, a small, possibly 10 to 20 gallon species dedicated aquarium would be ideal. In this situation the hobbyist is nearly guaranteed an uninterrupted viewing experience of the unique mutuality behavior. If the aquarist is only looking to maintain the fish and not the shrimp, then a larger aquarium with a more diverse community will also work. The ideal mix would include other small dither fish such as Wormfish from the genus Nemateleotris or the slightly larger and more active wrasses such as Macropharyngodon or Paracheilinus.

Compatibility chart for Stonogobiops:

Fish	Will Co-Exist	May Co-Exist	Will Not Co-Exist	Notes
Angels, Dwarf		X		A larger aquarium will contribute to greater success.
Angels, Large			X	Large physical size and aggressive feeding nature.
Anthias	X			Provided the aquarium is large enough for Anthias and direct feeding to the goby is administered.
Assessors	X			Excellent choice.
Basses			X	May consume Stonogobiops species.
Batfish			X	Large size and aggressive feeding habits.
Blennies		X		Most blennies should do well; larger ones may harass smaller gobies.
Boxfishes		X		The smaller members of the genus are the best option.
Butterflies	X			Excellent choice.
Cardinals	X			Excellent choice.
Catfish			X	May consume Stonogobiops species.
Comet		X		Small individuals will do well. Adults may attempt to consume the goby.
Cowfish		X		The smaller members of the genus are the best option.
Damsels		X		Most damsels can be incredibly abusive to tank mates.
Dottybacks			X	Most dottybacks will hunt and kill small gobies - Pseudochromis fridmani and P. springeri are possible exceptions.
Dragonets	X			Excellent choice.
Drums	X			Excellent choice.
Eels			X	May consume Stonogobiops species.
Filefish	X			Excellent choice.
Frogfish			X	May consume Stonogobiops species.
Goatfish			X	May consume Stonogobiops species.
Gobies	X			Excellent choice.
Grammas	X			Excellent choice, Gramma added after goby.
Groupers			X	May consume Stonogobiops species.
Hamlets			X	May consume Stonogobiops species.
Hawkfish			X	May consume Stonogobiops species.
Jawfish	X			The typical Yellowhead or Blue-Spotted is an excellent choice.
Lionfish			X	May consume Stonogobiops species.
Parrotfish			X	Overall size and aggressive swimming nature.
Pineapple Fish	X			Excellent choice.
Pipefish	X			Excellent choice.
Puffers			X	May harass smaller gobies.
Rabbitfish		X		Should be OK provided the aquarium is large enough for the rabbitfish and enough food reaches the goby.
Sand Perches			X	Larger individuals may harass or consume Stonogobiops species.
Scorpionfish			X	May consume Stonogobiops species.
Seahorses	X			Excellent choice.
Snappers			X	May consume Stonogobiops species.
Soapfishes			X	May consume Stonogobiops species.
Soldierfish			X	May consume Stonogobiops species.
Spinecheeks		X		Adult size may be intimidating.
Squirrelfish			X	May consume Stonogobiops species.
Surgeonfish		X		Aggressive feeding and swimming habits will likely require direct feeding to the goby.
Sweetlips			X	May consume Stonogobiops species.
Tilefish	X			Excellent choice.
Toadfish			X	May consume Stonogobiops species.
Triggerfish			X	May consume Stonogobiops species.
Waspfish			X	May consume Stonogobiops species.
Wrasses		X		Many wrasses are best avoided. The most peaceful ones will be good choices.

Note: While many of the fish listed are good tank mates for Stonogobiops species, one should research each fish individually before adding it to the aquarium. Some of the fish listed above are better left in the ocean or for advanced aquarists.

Predatory invertebrates such as brittle starfish from the genus Ophiarachna should also be avoided. Small gobies such as Stonogobiops are an easy meal for these aggressive predators. Likewise, anemones such as Stichodactyla species should be avoided. All too often fish will fall victim to these anemones.

Providing proper food is usually an easy obstacle to overcome once the goby begins to appear in the aquarium. Because they feed from the water column, they will likely snap at anything that floats past. The first Stonogobiops yasha I owned ate flake food in the retailer's 6" x 6" holding tank. Since they are not picky eaters, it should be easy to offer a varied diet. As they are zooplankton eaters, a diet rich in enriched brine shrimp or Mysis species shrimp is a good start, as is the aforementioned flake food or my personal favorite, fish roe. Most any food geared towards small carnivores will likely be accepted and appreciated. If the fish is in an aquarium with aggressive feeders, it may become necessary to directly feed the fish after placing food for the rest of the inhabitants at the far opposite end of the aquarium. Depending on tank mates, this may be a temporary exercise to ease acclimation or it may become a daily chore.

Meet the Species

By far the most popular Stonogobiops that makes its way into the aquarium trade is S. nematodes, the Highfin or Blackray Shrimp Goby. The word nematode is taken from the Greek language meaning "thread-like" or "filamentous," obviously referring to the first dorsal spine. Like all the rest of the genus, it remains a diminutive two inches of total length. This goby, always found in pairs, is also noted to associate only with Alpheus randalli in the wild.

A near exact match to Stonogobiops nematodes is S. xanthorhinica, or the Yellowfaced Shrimp Goby. Its common name is directly taken from the Greek meaning of xanthorhinica. "Xanthos" means yellow and "rhinos" refers to the snout. This goby, also only seen in pairs, relates with the shrimp Alpheus bellulus.

The most sought after Stonogobiops also happens to be the focus of this column. The Whiteray or Yasha Hashe Goby that is commonly referred to as scientifically un-described is actually named Stonogobiops yasha. This species is most often found in pairs, but not always. It is, however, always found with the shrimp Alpheus randalli.

Conclusion

It seems hobbyists are always looking for the next new thing to grasp their interest. Symbiotic relationships are certainly one of those new elements. However, most aquarists tend to gravitate towards the clownfish-anemone relationship, which is more than a unique relationship itself. But for some hobbyists the clownfish is just too common to satisfy the desire for something novel. For those individuals the goby-shrimp relationship might just satisfy that hunger.

References:

Baensch, H.A. 1994. Baensch Marine Atlas, Volume 1. Microcosm. Shelburne. 1215 pp.

DeLoach, N. 1999. Reef Fish Behavior. New World Publications. Jacksonville. 359 pp.

Hoese, D.F. and J.E. Randall. 1982. Revision of the Indo-Pacific gobiid fish genus Stonogobiops. Indo-Pac. Fish. (1):18 pp.

Iwata, A. and T. Hirata. 1994. A new gobiid fish, Stonogobiops pentafasciata, from Kashiwajima Island, Kochi Prefecture, Japan. Japan. J. Ichth. 41(2): 189-193.

Karplus, I. 1979. The tactile communication between Cryptocentrus steinitzi (Pisces: Gobiidae) and Alpheus purpurilenticularis (Crustacea, Alpheidae). Z. Tierpsychol. 49: 173-196, 13 figs.

Karplus, I. 1987. The association between gobiid fishes and burrowing alpheid shrimps. Oceanography and Marine Biology, Annual Revue, 25: 507-562.

Lieske, E. and R. Myers, 1994 Collins Pocket Guide. Coral reef fishes. Indo-Pacific & Caribbean including the Red Sea. Harper Collins Publishers, 400 pp.

Michael, S.W. 1999. Marine Fishes 500+ Essential-To-Know Aquarium Species. Microcosm. Shelburne, VT. 448 pp.

Polunin, N. V. C. and Lubbock, R. 1977. Prawn-associated gobies (Teleostei: Gobiidae) from the Seychelles, western Indian Ocean: systematics and ecology. J. Zool. (Lond.) 183: 63-101.

Preston, J.L. 1978. Communication systems and social interactions in a goby-shrimp symbiosis. Anim. Behav. 26: 791-802.

Smith, L. L. and Knopf, A. A. 1997. National Audubon Society: Field Guide to Tropical Marine Fishes. New York. p. 615.

Yoshino, T. and K. Shimada. 2001. Stonogobiops yasha, a new shrimp-associated goby from Japan. Ichthyol. Res. 48:405-408