A male Epibulus brevis, the dwarf slingjaw wrasse, photographed in the Raja Ampat Islands, West Papua. Photo by Scott W. Michael. 
The yellow color form of the female Epibulus brevis photographed in Lembeh Strait, Sulawesi. Note the black coloration on the pectoral fins. Photo by Scott W. Michael. 
The brown color form of the female Epibulus brevis photographed in Lembeh Strait, Sulawesi. Note the yellow spot on the dorsum. Photo by Scott W. Michael. The slingjaw wrasse (Epibulus insidiator) is a well known member of Indo-Pacific reef fish communities. It has also been recognized for some time that a strange, smaller slingjaw wrasse was lurking around coral reefs of the Western Pacific. (Some of us thought it was simply a color variant of E. insidiator.) It took ichthyologist, Dr. Bruce Carlson, to solve the Epibulus mystery, once and for all. Bruce, along with the god of reef fish taxonomy, Dr. John Randall, and molecular biologist, Michael Dawson, described Epibulus brevis, commonly known as the dwarf slingjaw wrasse, earlier this year.
Carlson et al. (2008) report E. brevis from Palau, the Philippines, Papua New Guinea, Solomon Islands, Sulawesi, Bali, Lombok, and Flores in Indonesia. I recently observed this fish in West Papua as well. It differs from E. insidiator in color. The males of this species are all brown with yellow on the throat area, on the caudal fin and a yellow marking at the opercular flap. Females vary in color from dark to light brown to yellow or almost white. The pectoral fins of the female almost always have black on the pectoral fins. The dwarf slingjaw also has longer pectoral fins than E. insidiator and there are also genetically distinct.
What is refreshing about this paper, is that it not only deals with taxonomy issues, but also compares the biology of the two known Epibulus spp. For example, the authors examined the stomach contents of both slingjaw species. The stomach contents of 20 E. brevis consisted mostly of crustaceans (crabs and shrimps), with only one larger individual (17.2 cm [6.8 in.]) containing both fishes and crabs. They also examined the “gut” contents of 31 E. insidiator and observed that the stomachs yielded more fish than E. brevis, but also crabs, shrimps, and polychaete worms. The authors suggest that the larger size of the E. insidiator may explain their proclivity to ingest more fish (likewise, smaller E. insidiator tended to contain more crustaceans than larger conspecifics). In both species, prey was highly masticated as a result of the actions of the pharyngeal teeth.
There are also some subtle differences between the behavior of the two species. Male E. insidiator will patrol high in the water column. When patrolling, the dorsal and anal fins are contracted, while the caudal fin is spread open extended. Most of male E. insidiator activity occurs over prominent reef features such as coral promontories and large boulders, which apparently serve as sites where the fish rendezvous with potential mates. Females hover or swim slowly about these sites and occasionally bob up and down as they move near a male. According to Colin and Bell (in Carlson et al. 2008), E. brevis spawns at sunset. Males do swim around a territory and occasionally rise into the water column, but they engage in less flagrant displays than E. insidiator and usually remain nearer the sea floor. When attempting to entice a female to spawn, a male E. brevis will swim around his potential mate with all his fins collapsed. However, the median fins are spread as the pair rise into the water column to spawn. There may even be differences in habitat preferences. Epibulus insidiator tends to occur in clear, outer reef habitats, while E. brevis is more common in protected areas.
There are many more reef fishes that have long been known to reef fish taxonomists that await formal descriptions. But, I for one, and very happy that the new Epibulus has finally been given a moniker.
References
Carlson, B. A., J. E. Randall, and M. N. Dawson. 2008. A New Species of Epibulus (Perciformes: Labridae) from the West Pacific. Copiea 2008 (2): 476-483.
Copyright (2008) Scott W. Michael
1 comment:
Do you have any thoughts as to why juvenile slingjaw wrasses are so similar to the Wetmorella wrasses? are the two genera related?
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