Worms Not Found in the Sandbed: The Genus Ptereleotris


I figured it was about time ReefKeeping.com offered some advice on worms that didn't originate from Dr. Ron Shimek. Except these are not worms with multiple pairs of appendages, or ones that crawl through our sandbeds. These worms are actually found with fins, and swimming through our water columns. They will not help maintain sandbeds, or eat detritus. These are the fish of the subfamily Ptereleotrinae, commonly called Wormfish in the marine ornamental fish hobby.

click here for full size picture
Ptereleotris zebra, or the Zebra Dart Goby, is the most common
and regularly imported Wormfish in the hobby. Photo courtesy
of Greg Rothschild of Mother Nature's Creations.

Meet the Family

Wormfish are sometimes also called Dartfish due to their defensive mechanism (more on this later). They are found in the subfamily Ptereleotrinae along with five other genera. Fourteen fish have the privilege of calling the genus Ptereleotris home. All fourteen species are long and thin with a large, slanted mouth. Additionally, each species has very small scales, and divided pelvic fins. All species remain small, usually between four to five inches long, and utilize an air bladder to hover above the substrate.

Ptereleotrinae
Ptereleotris
arabica
calliurus
evides
grammica
  • grammica
  • melanota
hanae
helenae
heteroptera
lineopinnis
melanopogon
microlepis
monoptera
uroditaenia
zebra

In 1863 Gill originally established the genus Ptereleotris. This was the renaming of Eleotris microlepis as Gill felt that Wormfish "appear to be rather entitled to the rank of a subfamily than that of a genus." Many authors (Herre, 1953; Herre, 1954; Koumans, 1953; and Smith, 1958) placed Ptereleotris in the family Eleotrididae, and these authors did so mainly due to the separated pelvic fins. However, when it was discovered that many gobies also possess these same separated pelvic fins, Ptereleotris was moved to Gobiidae.

Later, when Hoese (1984) decided to turn his attention to Ptereleotris, he moved them into the family Microdesmidae, which at that time had five genera classified within it (Dawson, 1974). Hoese took it a step further by naming two subfamilies within Microdesmidae, Microdesminae and Ptereleotrinae. He left the original five genera in the subfamily Microdesminae (see below) and differentiated the six genera of Ptereleotrinae from Microdesminae as "mouth strongly oblique (nearly vertical on some species), articular process of premaxilla absent or fused with the ascending process, and a single pterygiophore preceding the first haemal spine." These six genera consisted of four named genera, and two proposed genera that had yet been named. At present time only five genera are recognized (Rennis and Hoese, 1987). Hoese went even further stating that each subfamily shared characteristics with Gobiidae, and that further research may yield Ptereleotrinae as a distinct family.

Family Microdesmidae

  • Subfamily Microdesminae
    • Cerdale
    • Clarkichthys
    • Gunnellichthys
    • Microdesmus
    • Paragunnellichthys
  • Subfamily Ptereleotrinae
    • Aioliops
    • Ptereleotris
    • Parioglossus
    • Nemateleotris
    • Oxymetopon

In 2000 (Thacker) took an in-depth review of Microdesmidae as a whole, and helped clear up some of the misunderstandings surrounding the family. When the dust settled, she elevated the Ptereleotrinae to family status as the Ptereleotridae. This effectively raised the total number of families within Gobioidei to nine (see below). Further molecular phylogeny by Thacker (2001) reconfirmed her earlier work.

Gobioidei
Eleotrididae
Ptereleotridae
Gobiidae
Rhyacichthyidae
Kraemeriidae
Schindleriidae
Microdesmidae
Xenisthmidae
Odontobutidae
Thacker, 2000

In the Wild

Some of the Ptereleotris species can be found throughout the entire Indo-Pacific (P. evides, P. grammica) while some other species have a limited distribution (P. arabica, P. melanopogon) within the Indian or Pacific Oceans. All species seem to have their own preferred water depths with some ranging from as shallow as five feet (P. evides) to others that may range as deep as 300 feet (P. lineopinnis). Despite the varied depths, all relate to sand bottoms with nearby rubble and rock slopes.

The nearby rock and rubble zones serve as protection. It is in conjunction with the rocks that Ptereleotris earns the nickname 'Dartfish.' When danger looms nearby, these fish quickly retreat, or dart, into the rocks. In addition to using the 'dart holes' when danger approaches, these fish will also use them for overnight protection. These 'dart holes' are either burrows within the rock structure or, in most cases, burrows within the sand. However, the Wormfish do not make their own burrows within which they seek shelter. Instead, the Wormfish take up residence in the homes of alpheid shrimp or in the burrows dug by gobies of the genus Valenciennea. Additionally, burrows created by worms or mollusks are also utilized. They do not live in a symbiotic relationship with these fish, shrimp, and various other invertebrates, but rather invite themselves when they feel like it. Instead of concentrating on just one burrow, Ptereleotris species will usually exploit several different 'dart holes.' I guess they do not want to wear out their welcome in their rented homes.

Juveniles are found in groups, sometimes up 200 or more individuals, but most species will usually pair-up with a mate once they reach maturity. Feeding is remarkably similar among all of these species. The groups or pairs will hover from two to six feet above their rock patch and capture zooplankton as it drifts past. They will travel several feet from their security boltholes, but return promptly after snatching their intended morsel from the water column.

In the Home Aquarium

With a little precaution involving proper stocking and in providing adequate hiding places, Wormfish can generally make a seamless transition into the home aquarium. As with any small, peaceful fish, a major consideration is tank mates. An obvious group of fish to avoid is the predators; fish such as lionfish, groupers, and morays are not suitable tankmates. Wormfish will fall victim to these larger predators eventually. Fast swimming fish will keep Wormfish tucked closely to dart holes, and subsequently you will not have the chance to observe the fish as much as you may have envisioned. Otherwise, these same fast swimming fishes may suddenly frighten the Wormfish, which may send the fish sailing out of the aquarium water. Thus, for those that wish to attempt mixing Wormfish with fast fish, make sure your aquarium is completely enclosed. Ideal tank mates would include such fish that are also best kept in peaceful aquariums. This may include other gobies, some blennies, grammas, jawfish, and cardinals. It also includes conspecifics. Juveniles can be kept in large groups, but adults should be limited to pairs in the aquarium.

Within the confines of a reef aquarium, these 'worms' are completely reef safe. They will not bother corals, or mobile invertebrates. Predatory invertebrates like starfish and mantis shrimp should definitely be avoided, however, as Wormfish make easy prey.

Compatibility chart for Ptereleotris:

Fish

Will Co-Exist

May Co-Exist

Will Not Co-Exist

Notes

Angels, Dwarf

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Angels, Large

 

 
X

Can consume Wormfish.

Anthias

X
 

 

Should be excellent tank mates.

Assessors

X
 

 

Should be excellent tank mates.

Basses

 

 
X

Can consume Wormfish.

Batfish

 

X

 

Aggressive swimmers will keep the Wormfish hiding.

Blennies

X
 

 

Should be excellent tank mates.

Boxfishes

 
 

X

Aggressive feeders and swimmers with a possibility of consuming Wormfish.

Butterflies

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Cardinals

X
 

 

Should be excellent tank mates.

Catfish

 

 
X

Can consume Wormfish.

Comet

X

 

 

Should be excellent tank mates.

Cowfish

 
X

 

Size will eventually become an issue, which will keep Wormfish hiding.

Damsels

 

X

 

Aggressive swimmers will keep the Wormfish hiding.

Dottybacks

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Dragonets

X

 

 

Should be excellent tank mates.

Drums

X
 

 

Should be excellent tank mates.

Eels

 

 
X

Can consume Wormfish.

Filefish

X
 

 

Should be excellent tank mates.

Frogfish

 
 

X

Can consume Wormfish.

Goatfish

 
 

X

Can consume Wormfish.

Gobies

X
 

 

Should be excellent tank mates.

Grammas

X

 

 

Should be excellent tank mates.

Groupers

 

 

X

Can consume Wormfish.

Hamlets

X

 

 

Should be excellent tank mates.

Hawkfish

 

X

 

Aggressive swimmers will keep the Wormfish hiding.

Jawfish

X

 

 

Should be excellent tank mates.

Lionfish

 

 
X

Can consume Wormfish.

Parrotfish

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Pineapple Fish

X

 

 

Should be excellent tank mates.

Pipefish

X
 

 

Should be excellent tank mates.

Puffers

 

X

 

Aggressive swimmers will keep the Wormfish hiding.

Rabbitfish

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Sand Perches

 
X

 

Adults become aggressive and may keep Wormfish in hiding.

Scorpionfish

 
 
X

Can consume Wormfish.

Seahorses

X
 

 

Should be excellent tank mates.

Snappers

 

 

X

Can consume Wormfish.

Soapfishes

 

 

X

Can consume Wormfish.

Soldierfish

 

 

X

Can consume Wormfish.

Spinecheeks

 
X

 

Adult size is intimidating and may keep Wormfish in hiding.

Squirrelfish

 

 

X

Can consume Wormfish.

Surgeonfish

 

X
 

Aggressive swimmers will keep the Wormfish hiding.

Sweetlips

 

 

X

Can consume Wormfish.

Tilefish

X

 
 

Should be excellent tank mates.

Toadfish

 
 

X

Can consume Wormfish.

Triggerfish

 

 

X

Can consume Wormfish.

Waspfish

 
 

X

Can consume Wormfish.

Wrasses

 

X

 

Aggressive swimmers will keep the Wormfish hiding.

Note: While many of the fish listed are good tank mates for Ptereleotris sp., you should research each fish individually before adding it to your aquarium. Some of the fish mentioned are better left in the ocean, or for advanced aquarists.

Above and beyond the proper tank mates, one must ensure the proper diet is met. Enriched brine shrimp and Mysis are great foods for newly introduced specimens, but a larger selection and variety of foods will certainly benefit the fish. Any foods geared towards plankton eaters should be considered appropriate.

One consideration, which may not be quite so obvious, is proper construction of several dart holes. Since Ptereleotris is incapable of building its own holes, this duty is passed down to the reef keepers themselves. There should be several dart holes in the aquarium, with possibly several in the rockwork as well as the sandbed. When placed properly, they can be nearly invisible to human eyes, and yet the fish will bolt into the artificial shelters at lightning fast speeds. One of the best materials to employ for this purpose is PVC. A ¾" pipe of variable length can be fitted into a larger 2" diameter pipe of several inches of length and make a great bolthole. With the addition of a 90 degree bend, the ¾" opening can lie on the surface of the sand, with the rest of the chamber completely submerged beneath the sandbed. Don't be afraid to put two openings opposite each other on the same chamber. The fish will enjoy being able to enter their den and exit some place else. The same tactic can be used if the pipe is strategically placed behind the rockwork.

Meet the Species

Very few Wormfish are regularly harvested and shipped for the aquarium trade of North America. Two species in particular are more popular than any of the others: Ptereleotris evides and Ptereleotris zebra. Of these two, P. zebra is far more common.

Called the Zebra Bar Goby in the aquarium trade, P. zebra is fairly common throughout the entire Indo-Pacific. At one point this species was given monotypic classification in the genus Pogonoculius (Fowler, 1938) because it has a chin barbell. After further research, it was discovered that most Ptereleotris either have a chin barbell, or the start of what appears to be an undeveloped barbell. Therefore, it later rejoined Ptereleotris. It is among the most timid of all Wormfish, but will settle into a home reef aquarium within a week or two. If the tank mates are less aggressive, the Zebra goby will remain suspended in the water column for lengthy periods of time. Juveniles will completely lack the vertical stripes, while the adults will have pronounced stripes. It is a shallow water species, and thus will do well even in brightly lit aquariums.

click here for full size picture
Ptereleotris zebra and Chromis viridis square off in a staring match. Photo
courtesy of Greg Rothschild of Mother Nature's Creations.

The Scissortail goby, or Ptereleotris evides, is another widespread Wormfish, which can be found throughout the entire Indo-Pacific. The juvenile coloration has a distinct oval dark spot at the base of the caudal fin, but this is lost as the fish matures. This juvenile spotting confused researchers early on, which led to several different names for the fish, including P. tricolor (Smith, 1956, 1958). Like P. zebra, it prefers waters less than 40 feet deep. Scuba divers have noted how easily scared these fish are, and this edginess typically carries over into the aquarium. However, given a proper setup, it should only take a week or two before it settles down and becomes regularly visible.

click here for full size picture
click here for full size picture
Ptereleotris evides has become more popular in the aquarium trade as of late.
As more hobbyists begin to maintain smaller reef aquariums, fish like these will
continue to become more popular. Top photo courtesy of Greg Rothschild of
Mother Nature's Creations, bottom photo courtesy of Ken Hahn of Reef Corner.

Possibly the most sought after of all the Wormfish is Ptereleotris grammica grammica, or the Many-striped Wormfish. It is a deeper water fish than most Wormfish, found roughly 100 feet deep or deeper, which gives good reason as to why it is only irregularly collected for the hobby. The color form pictured below is the most often found variety. Their distribution is wide with specimens collected from the Indian, North, and South Pacific Oceans. However, within those oceans populations remain fairly limited to the Philippines, Great Barrier Reef, Indonesia, and New Britain. Randall and Lubbock (1982) also described a second color form found only from the Mauritius Islands and subsequently named it a different sub-species: P. grammica melanota. Its only notable color difference is the stripe that runs laterally across the body, which is black on P. grammica melanota.

click here for full size picture
The highly sought after Ptereleotris grammica grammica is pictured above.
It should be easy to understand why these are sought after. Photo
courtesy of Jun Harada of Jun's Underwater Photo Gallery.

Various other Wormfish show up in the trade from time to time, but the color is usually bland, consisting of tones of baby blue, cream, gray, and brown. It can be assumed that care is nearly identical for any of these other species as it is for those highlighted above.

Conclusion

Hopefully, this brief look at the Wormfish has given more ideas to many of the readers searching for small, peaceful fish for the reef aquarium. Fish of the genus Ptereleotris are possibly among the best fish to consider when stocking for a reef aquarium. Their overall resistance to disease, along with their passive nature and unique swimming characteristics make this a popular choice of hobbyists' worldwide.



If you have any questions about this article, please visit my author forum on Reef Central.

References:

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

Burgess, W.E., et al. 1991. Dr. Burgess's Mini-Atlas of Marine Aquarium Fishes MinEdition. T.F.H. Publications. Neptune City. 1023 pp.

Fowler, H.W. 1938. Descriptions of new fishes obtained by the United States Bureau of Fisheries steamer "Albatross", chiefly in Philippine Seas and adjacent waters. Proc. U.S. Natl. Mus. 85(3032): 31-135, 56 figs.

Gill, T. 1963. On the gobioids of the eastern coast of the United States. Proc. Acad. Nat. Sci. Phila.: 267-271.

Herre, A.W.C.T. 1953. The tropical Pacific Eleotridae with vomerine teeth with descriptions of two new genera and two new species from the Marshall Islands. Phillip. Jour. Sci. 82(2):189-192.

Herre, A.W.C.T. 1954. The eleotrid gobies of the Philippines and the adjacent regions. Phillip. Jour. Sci. 82(4) 345-373.

Koumans, F.P. 1953. The Fishes of the Indo-Australian Archipelago, Gobioidae. E.J. Brill, Leiden. Vol 10, xiii + 423pp.

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

Michael, S. W. 1998. Family Microdesmidae. Reef Fishes Volume 1. Microcosm. Shelburne. 624 pp.

Randall, J.E. and Hoese, D. 1985. Revision of the Indo-Pacific Dartfishes, Genus Ptereleotris (Perciformes: Gobioidei). Indo Pacific Fishes No. 7: 1 36.

Rennis, D.S. and Hoese, D.F. 1987. Aioliops, a new genus of ptereleotrine fish (Pisces: Gobioidei) from the tropical Indo-Pacific with descriptions of four new scecies. Rec. Aust. Mus. 39:67-84.

Smith, J.L.B. 1953. The Sea Fishes of Southern Africa. Central News Agency, Ltd. Cape Town. 2nd Edition, xvi + 564pp., 107 pls.

Smith, J.L.B. 1956. The fishes of Aldabra. Part VI. Ann. Mag. Nat. Hist., ser. 12, 9:817-829, 5figs.

Smith, J.L.B. 1958. The fishes of the family Eleotridae in the Western Indian Ocean. Rhodes Univ., Ichth. Bull. 11: 137-153, 3 pls., 17 text-figs.

Thacker, C.E. 2000. Phylogeny of Wormfishes (Teleostei: Gobioidei: Microdesmidae). Copeia, 2000(4), pp. 940-957.

Thacker, C.E. 2001. Molecular phylogeny of the gobioid fishes (Teleostei: Perciformes: Gobioidei). Mol. Phylo. And Evo. 26 (2003) 354-368.




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Worms Not Found in the Sandbed: The Genus Ptereleotris - ReefKeeping.com