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 Editorial
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Corner |
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Vertebrates
An endemic enigma: the secret identity of Hong Kong’s black paradise fish
For a time, it seemed that we had things sorted out. There were two species of paradise fishes belonging to the genus Macropodus in Hong Kong: the common Chinese paradise fish, Macropodus opercularis, plus the recently recorded and relatively scarce black paradise fish, Macropodus concolor. A third species, the round-tailed paradise fish, Macropodus ocellatus, occurs further north in mainland China but has not been found in Hong Kong. Things appeared pretty simple: the two co-occuring Macropodus were easily distinguished by their colour patterns (concolor lacks the vertical banding of opercularis), although those seeking morphological differences between the two would have had to examine bony structures (specifically the otoliths). Scientists are frequently urged to seek simplicity of this type, but to mistrust it. Mistrust or skepticism was certainly warranted in this case, as the benefit of hindsight now shows. In fact, M. concolor does not occur in Hong Kong. Our ‘black paradise fish’ is, in fact, not the black paradise fish (i.e. M. concolor) but another black paradise fish. It has now been described by Jörg Freyhof and Fabian Heder, from specimens collected at Sha Lo Tung, and named Macropodus hongkongensis. Freyhof & Heder (2002) relegate M. concolor, first recorded from Hong Kong by Dudgeon & Chan (1996; see also Dudgeon, 1999; Chan & Töpfer, 2000), to a junior synonym of M. hongkongensis. The new species is, as far as anyone knows, a Hong Kong endemic. Given the threats to its habitat in Hong Kong (especially lowland marshes – the former wetland at Sham Chung comes to mind), M. hongkongensis should be treated as an endangered species.
So what is the difference between Macropodus concolor and Macropodus hongkongensis? To all intents and purposes they are indistinguishable by external characteristics when dead and preserved in formalin. In life, however, they can be separated by their colour. Macropodus hongkongensis has black spots on the top of the head and may have blotches on the back (around the anterior portion of the doral fin). In addition, it has a thin black margin along the anal fin. These characters are lacking in M. concolor. An additional distinguishing feature – probably the most conspicuous one - is the pelvic fin rays: the first soft pelvic fin ray of M. hongkonensis is white; it is red in M. concolor. Furthermore, M. hongkongensis has an opercular spot that M. concolor lacks or expresses indistinctly. There are also subtle differences in the scale pigmentation. As far as is known these two species are geographically separate, and may have evolved independently from populations of the widely distributed M. opercularis in Vietnam (concolor) and southern China (hongkongensis).
Is that the end of the story? Not at all. It turns out Macropodus concolor is not really M. concolor. In fact, M. concolor does not really exist! Let me explain. When Ahl described the ‘original’ M. concolor in 1937 he treated it as a subspecies of M.opercularis: i.e. M. opercularis concolor (Ahl, 1937). Vierke (1983) raised the subspecies to full speices rank, and this assignment has been widely accepted (Paepke, 1994). However, unknown to Ahl, Schreitmüller (1936) had already described some of the same batch of fish specimens as M. opercularis var. spechti in honour of the German aquarist M. Spechti who received the first importation of these paradise fishes to Europe. Under the International Code of Zoological Nomenclature, the oldest name applied to a species normally has precedence and, since both workers described portions of the same collection of fish, it is clear that M. spechti is the valid name (Freyhof & Heder, 2002). So M. concolor disappears, relegated to a junior synonym of M. spechti.
To recap: there are two species of paradise fish in Hong Kong: Macropodus opercularis and M. hongkongensis (the fish formerly known as M. concolor). An additional species that resembles M. hongkongensis is confined to Vietnam; it is called M. spechti (the other fish formerly known as M. concolor).
Some of the fishes known in the European aquarium trade as M. concolor are the descendents of Spechti’s original importation almost 70 years ago, and are now highly inbred. Others may be later exports from Vietnam or Hong Kong. This means that the actual identity of any fish illustrated in the aquarium literature under the name M. concolor is uncertain. But we can be confident of one thing: M. concolor is the wrong name! Of greater importance, we now know that Hong Kong is host to an endemic and apparently endangered freshwater fish. The challenge is now to conserve it. Inclusion under the Protection of Endangered Species Ordinance in Hong Kong would be a constructive initial step.
Bibliography
Ahl, E. (1937). Neue Süsswasserfische aus dem Indischen und Malaiischen Gebeit. Zool. Anz. 117: 113-119.
Chan, B.P.L. & Töpfer, J. (2000). Bernerkungen zu einem neuen natürlichen Fundort des Schwarzen Makropoden, Macropodus concolor Ahl, 1937. Der Makropode 22: 115-117.
Dudgeon, D. (1999). The Black Paradise Fish in Hong Kong (China): preliminary observations and conservation significance. Labyrinth 105: 6-7.
Dudgeon, D. & Chan, E.W.C. (1996). Ecological Study of Freshwater Wetland Habitats in Hong Kong. Unpublished report for the Agriculture & Fisheries Department, Hong Kong Government.
Freyhof, J. & Herder, F. (2002). Review if the paradise fishes of the genus Macropodus in Vietnam, with a description of two new species from Vietnam and southern China (Perciformes: Osphronemidae). Ichthyol. Explor. Freshwaters 13: 147-167.
Paepke, H.J. (1994). Die Paradiesfische. Westarp Wissenschaften, Magdeburg.
Schreitmüller, W. (1936). Ein neuer Macropode Marcopodus opercularis L. var. spechti Schreitmüller (1936) (Netz oder Gitterparadiesfisch). Das Aquarium 10: 181-182.
Vierke, J. (1983). Eine gute Art, Macropodus concolor Ahl, 1937. Der Makropode 5: 202-204.
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Fig.
1 A black paradise fish
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Porcupine! |
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