Dermogenys collettei Meisner, 2001
|Dermogenys collettei (Photo: Wilfred & Chirstopher (C))|
Dermongenys collettei or the Pygmy halfbeak belongs to a group of halfbeaks that are widely distributed across Southeast Asia1 . As the halfbeak name implies, these fishes have an unusual lower jaw that is noticeably longer and protrudes beyond their upper jaw. This elongated lower jaw contains sensory receptors for the fish to sense its surroundings. The half-beak condition of these fishes become more prominent as the fish matures 2 . Males Dermogenys are known to be aggressive towards each another, hence members of this genus are sometimes used as fighting fishes 3 . Pregnant females of Dermogenys collettei give birth to live young that resembles a miniature adult, but without the prominent asymmetrical beak condition 4 . Recent phylogenetic studies suggest that this half-beak form is the basal condition within the taxon Beloniformes.
Scientific name 5
For more information on identification, click here.
Dermogenys collettei (Photo: Wilfred and Christopher (C))
Dermongenys collettei are surface-dwellers that feed mostly on small floating larvae and adult insects that have drifted by or landed onto the water surface 6 . A member of the genus, Dermogenys pusilla, was observed to prey fairly extensively on mosquito larvae, flies (dipterans), ephemeropterans (mayflies) and hymenopterans (ants)7 8 . These fishes were also observed to approach prey item from the side of the jaws rather than the front 9 . Studies on Dermogenys pusilla showed that the elongated lower jaws of this group of halfbeaks contain mechanoreceptive neuromasts to detect movements, and may also contain taste buds for sensing chemicals 4 .
Dermogenys collettei feeding on food items on the surface (Video: Wilfred (C))
Dermogenys collettei capturing food from side of mouth (Photo: Wilfred (C))
Dermogenys collettei are gregarious surface feeders that are often found together near the banks of water bodies 6 . Aggressive behaviour between male fishes are frequently documented from species in this genus that are sold in the aquarium trade, such as Dermogenys pusilla. Male fishes display a variety of combative behaviour such as threatening postures, biting, mouth fighting and chasing rivals. These fishes may also lock jaws during fights. Male fishes were found to display a dominance hierarchy in aquarium settings where only the dominant male is allowed near the female 4 .
A male Dermogenys collettei defending its territory (Video: Wilfred (C))
Two male Demogenys pusilla fighting (Video: Youtube)
The major elements of courtship for Dermogenys begin with males swimming towards the female and may involve nipping of her fins. Fin nipping may induce the female to stop or slow down her movement, hence giving the male a chance to copulate. The copulation process for Dermogenys occurs very quickly, where male fishes were observed to bend their body around the female and pushes onto her. Unreceptive females were observed to threaten and even attack her suitors. The specific process of insemination is unknown, likewise whether the spermatozuegmata (sperm packet) is deposited externally
on, near or into the genital opening of the female by the male's andropodium (modified anal fin) 4 .
A male Dermogenys collettei courting female fishes (Video: Wilfred (C))
Unreceptive female Dermogenys pusilla fighting off a male suitor (Video: Youtube)
Unlike most fishes, members of the genus Demogenys are viviparous, where the fish produce live young instead of eggs from within the body. Five unique forms of viviparity (Type 1-5) have been observed in freshwater halfbeaks and Dermogenys collettei display the type 1 form, where the whole gestation period is intrafollicular 10 . For more information on freshwater halfbeak viviparity, click here.
Female Dermogenys collettei with new born fry (Photo: Wilfred (C))
New born Dermogenys collettei (Picture: Wilfred & Christopher (C))
Larval halfbeaks have short jaws without prominent asymmetrical beak condition. As the fish matures, the lower jaw elongates to form the half-beak condition 11 .
Preserved specimens of Dermogenys collettei showing jaw development from; A) Larval stage; B) young juvenile; C) juvenile; D) adult (Photo: Wilfred & Christopher (C))
Dermogenys collettei are found in small streams and ponds ranging from fresh to brackish water in both forested and open areas. Fishes occupy the water surface and are frequently found near to the banks of water bodies. Specimens caught in Brunei were found in mangrove streams with acidic water of pH 3.8 6 12 .
Stream with Dermogenys collettei found in both open and forested areas (Photo: Wilfred (C))
Underwater view of Dermogenys collettei stream habitat (Photo: Wilfred (C))
Local populations of Hemirhamphodon pogonognathus:
A) Dermogenys collettei; B) Hemirhamphodon pogonognathus (Photo: Wilfred (C))
Local Dermogenys collettei distribution (Map outline adapted from Wikipedia Link
Distribution of Dermogenys collettei (Map:Wilfred (Information adapted from Meisner, 2001))
Dermogenys collettei has a greyish slender body that grows to about 6 cm. Mature female fishes are larger than males. The dorsal fin of Dermogenys collettei originates behind the anal fin origin and may have red markings 6 .
Adult female and male Dermogenys collettei (Photo: Wilfred & Christopher (C))
Lateral view of Dermogenys collettei (Photo: Wilfred and Christopher (C))
Jaw of Dermogenys collettei (Photo: Wilfred and Chrisopher (C))
Oral dentition on premaxilla plate (upper jaw) of Dermogenys collettei with outline on half of the upper jaw (Photo: Wilfred (C))
A) Tip of lower jaw of Dermogenys collettei; B) Halfbeak with lower jaw broken (Photo: Wilfred (C))
Eye of Dermogenys collettei (Photo: Wilfred & Christopher (C))
Nasal fossa of halfbeaks, reflected as a small ring; A) Dermogenys collettei; B) Marine halfbeak(Photo: Wilfred (C))
Nasal barbel of halfbeaks; A) Dermogenys collettei; B) Marine halfbeak (Photo: Wilfred (C))
Anal fin of Dermogenys collettei with with first 5 fin rays numbered; A) Retracted anal fin of male andropodium;B) Extended anal fin of male andropodium; C) Anal fin of female (Photo: Wilfred & Christopher (C))
Identification of local halfbeaks
Dermogenys collettei: anal fin originates before the dorsal fin origin
Hemirhamphodon pogonognathus: anal fin originates behind dorsal fin, presence of a fleshy tip on the lower jaw that curves downward 6
Comparison of the origin of anal fin; A) Dermogenys collettei; B) Hemirhamphodon pogonognathus (Photo: Wilfred (C))
A) Dermogenys collettei with no fleshy tip on jaw; B) Hemirhamphodon pogonognathus with fleshy tip on lower jaw (Picture: Wilfred (C))
unique row of teeth located behind the rows of outer teeth that extend medially in a concave row to approximately half the length of the premaxilla
shortened, expanded autopalatine
distinct geniculus on second anal-fin ray in males beginning at segment three or four
gestation is entirely intrafollicular
large spermatozeugmata due to the mode of spermatogenesis in which the spermatid nuclei become arranged in one layer evenly around the periphery of spermatocysts.
Species diagnosis 12
The anal fin structure of male Dermogenys collettei is closest to that of Dermogenys pusilla and can be distinguished by:
Thicker spiculus divided into 4-6 segments (vs. <3)
Proximal segments 4-6 of second anal-fin ray in males noticeably thicker along anterior edge
Diagrammatic illustration of the andropodium of a male Dermogenys (Adapted from Meisner & Collette, 1998 17 , illustration by Keiko Hiratsuka Moore and with approval from the Raffles Bulletin of Zoology)
Dermogenys collettei (Photo: Wilfred (C))
A) Jaw of Dermogenys collettei; B) Jaw of a needlefish (Photo: Wilfred & Christopher (C))
Finding out the evolutionary relationship between different species offers insight to speciation events that have occurred. In addition, information on the evolutionary history of organisms can be used as a criterion in conservation. Conserving an area with many different groups of organisms not only helps preserve a wider range of different species, but also their evolutionary history. Hence, areas with only a single or few groups of closely related organisms should have a lower conservation priority than areas with many different groups of organisms.
Meisner, 2001 performed a phylogenetic analysis on 28 taxa (10 species of Dermogenys and 13 species of Nomorhamphus) based on a data matrix comprising of 45 characters and constructed a strict consensus phylogenetic tree using the branch and bound option in PAUP 12 . Nested within node A, the monophyly of Dermogenys stricto sensu, is supported by 3 characters:
The genera (Dermogenys) is divided into 2 clades; Dermogenys pusilla group (Node B) and Dermogenys orientalis group (Node C). Dermogenys collettei is nested within the Dermogenys pusilla species group clade (Node B), sharing 2 common characters:
The data used in this study was unable to determine the relationship between species within a clade. More data such as using DNA barcoding may be needed to provide better resolution to the relationship between sister taxa 23 .
Simplified phylogenetic tree of Dermogenys (Diagram: Wilfred (Adapted from Meisner, 2001))
A holotype is an important specimen which the formal description of a species is based on, and should possess the typical characteristics of that particular taxon. Referring to holotype specimen is therefore the best way to identify unknown specimens. Due to the importance of holotype specimens, designating the correct specimen as the holotype is extremely important for taxonomists. A paratype is another specimen of the same type series not designated as the holotype, and there can be multiple paratype specimens.
The holotype for Dermogenys collettei is collected from Kuching, Sarawak in 1994. It is kept in the Raffles Museum of Biodiversity Research (RMBR), specimen number ZRC 37790, in Singapore. The paratype (a female) is collected with the holotype and is also stored in the RMBR, specimen number ZRC 46161 12 .
Preserved specimen of Dermogenys collettei (Photo: Wilfred and Christopher (C))
Dermogenys collettei is not yet assessed by IUCN Red List. Some species from the genus Dermogenys that are in the Red list includes:
Dermogenys burmanica (Least Concern)
Dermogenys siamensis (Least Concern)
Anthropogenic activities are major threats to some freshwater halfbeaks from the genus Dermogenys and Nomorhamphus 24 . As these fishes are commonly traded, the source of these fishes should be monitored to ensure sustainable catch. More research are therefore required to protect these unique fishes.
Dermogenys collettei (Photo: Wilfred (C))
Dermogenys collettei. Torres, A.G., 2012. Fishbase
Family Hemirhamphidae. Lim, K.K.P. & Ng,P.K.L., 1990. A guide to freshwater fishes of Singapore
Freshwater fishes in Singapore. National Parks Board, Singapore
Halfbeaks (Hemirhamphidae). Tan, R. 2008. WIld Singapore
Pygmy halfbeak. Baker, N., 2012. Ecology Asia
Wrestling Halfbeak (Dermogenys pusilla). Aquarium Life
Literature and References
|1||Meisner, A. D. & Burns, J. R. 1997. Testis and andropodial development in a viviparous halfbeak, Dermogenys sp. (Teleostei: Hemiramphidae). Copeia. 1997(1): 44-52.|
|2||Collette, B. B., McGowen, G. E., Parin, N. V. & Mito, S., 1984. Beloniformes: development and relationships. In: Mosher, H. G., Richards, W. J., Kendall, A. W. & Richardson, S. L., eds. Ontogeny and systematics of fishes. American Society of Ichthyologists and Herpetologists Special Publication, p. 335-354.|
|3||Lim, K. K. P. & Ng, P. K. L., 1990. A guide to the freshwater fishes of Singapore. The Science Centre, Singapore, p. 70. [ a b c d ]|
|4||Greven, H., 2010. What Do we know about reproduction of internally fertilizing halfbeaks (Zenarchopteridae)? In: Uribe, M. C. & Grier, H. J., eds. Viviparous Fishes II. New Life Publications, Homestead, Florida. [ a b c d e f ]|
|5||Meisner, A. D. & Burns, J. R., 1997. Viviparity in the halfbeak Genera Dermogenys and Nomorhamphus (Teleostei: Hemiramphidae). Journal of Morphology. 234: 295–317.|
|6||Baker, N. & Lim, K. K. P., 2008. Wild animals of Singapore. Draco Publishing and Distribution Pte Ltd, Singapore, p. 40. [ a b c d e ]|
|7||Usman, S. & Soemarlan, S., 1974. Pengamatan di laboratorium mengenai ikan-ikan pemakan jentik nyamuk. Buletin Penelitian Kesehatan. 2.|
|8||Ward-Campbell, B. M. S., Beamish, F. W. H. & Kongchaiya, C., 2005. Morphological characteristics in relation to diet in five coexisting Thai fish species. Journal of Fish Biology 67: 1266-1279.|
|9||Greven, H., 2006. Viviparous halfbeaks. Notes on structural peculiarities, feeding, and reproduction. Biologie der Aquarienfische. Tetra Verlag GmbH, p. 271-296.|
|10||Meisner, A. D. & Burns, J. R., 1997. Viviparity in the halfbeak Genera Dermogenys and Nomorhamphus (Teleostei: Hemiramphidae). Journal of Morphology. 234: 295–317.|
|11||Lovejoy, N. R., Iranpour, M. & Collette, B. B., 2004. Phylogeny and Jaw Ontogeny of Beloniform Fishes. Integrative and Comparative Biology. 44: 366–377. [ a b ]|
|12||Meisner, A. D., 2001. Phylogenetic systematics of the viviparous halfbeak genera Dermogenys and Nomorhamphus(Teleostei: Hemiramphidae: Zenarchopterinae). Zoological Journal of the Linnean Society. 133: 199-283. [ a b c d e f g h i j ]|
|13||Catalogue of Life. 2012. Available online at:http://www.catalogueoflife.org/col/search/all/key/Hemirhamphodon/match/1 [Accessed on 25th October 2012]|
|14||Boughton, D. A., Collette, B. B. & Mccune, A. R., 1991. Heterochrony in jaw morphology of Needlefishes (Teleostei: Belonidae). Systematic Zoology. 40(3): 329-354|
|15||Greven, H., Wanninger, A. C. & Clemen, G., 1997. Dentigerous bones and dentition in the hemiramphid fishDermogenys pusillus (Atheriniformes, Teleostei). Annals of Anatomy-Anatomischer Anzeiger. 179(1): 21-32.|
|16||Reckel, F., Melzer, R. R., Parry, J. W. L. & Bowmaker, J. K., 2002. The retina of five atherinomorph teleosts: Photoreceptors, patterns and spectral sensitivities. Brain, Behaviour and Evolution. 60:249-264.|
|17||Meisner, A. D. & Collette, B. B., 1998. A new species of viviparous halfbeak, Dermogenys bispina (Teleostei: Hemiramphidae) from Sabah (North Borneo). The Raffles Bulletin of Zoology. 46: 373-380.|
|18||Monks, N. Halfbeaks: Family Hemiramphidae. Available online at:http://www.wetwebmedia.com/ca/volume_4/V4I1/halfbeaks/Halfbeaks.htm [Accessed on 25th October 2012]|
Monks, N. 2011. 7 forgotten livebearers. Tropical Fish Magazine. Available online at:
http://www.tfhmagazine.com/details/articles/7-forgotten-livebearers-full-article.htm [Accessed on 26th October 2012]
|20||Roos, N., Chamnan, C., Loeung, D., Jakobsen, J. & Thilsted, S. H., 2006. Freshwater fish as a dietary source of vitamin A in Cambodia. Food Chemistry. 103: 1104-1111.|
|21||Encyclopedia of Life. Dermogenys collettei. Available online at: http://eol.org/pages/210958/names [Accessed online on 25th October 2012]|
|22||Lovejoy, N. R., 2000. Reinterpreting recapitulation: Systematics of Needlefishes and their allies (Teleostei: Beloniformes). Evolution. 54(4): 1394-1362.|
|23||de Bruyn, M., Grail, W., Barlow, A. & Carvalho, G. R., 2010. Anonymous nuclear markers for Southeast Asian halfbeak fishes (Dermogenys). Conservation Genetics Resources. 2(1): 325-327.|
|24||IUCN 2012. IUCN Red List of threatened species. Version 2012.2. Available online at: http://www.iucnredlist.org/search [Accessed online on 15th December 2012]|
This page was authored by Yeo Renjie Wilfred
Last curated on 2012