Monday, August 3, 2015

The Sailfin catfish

     Three species of sailfin catfishes (Pterygoplichthys) native to South America, P. multiradiatus, P. pardalis and P. disjunctivus, have been collected recently in several countries in southeastern Asia. Pterygoplichthys multiradiatus is known to reproduce in Taiwan, and P. pardalis is presumed to be reproducing in Singapore given the frequency of its collection and the range in size of specimens collected. The status of the species elsewhere in southeastern Asia is less certain. These catfishes are common in the pet trade and almost certainly were released by aquarists. It is likely that these fishes will become widely established in southeastern Asia and will have negative environmental impacts, including alteration of food webs, in nonnative areas. 

   sailfin catfishes found in Indonesia as Pterygoplichthys pardalis. Specimens in the Zoological Reference Collection, Raffles Museum of Biodiversity Research (ZRC), and the Florida Museum of Natural History (UF) document the presence of Pterygoplichthys pardalis in Singapore, Peninsular Malaysia, Java and Sumatra, and Pterygoplichthys disjunctivus in Singapore, Java and Taiwan (see Material Examined). With about 80 genera and 680 species (Reis et al., 2003), Loricariidae is the largest family of catfishes (Siluriformes). Loricariids are endemic to South America and Panama and are characterized by having large bony plates and a ventral mouth. Loricariids with 10 or more dorsal fin rays are members of the genus Pterygoplichthys and are referred to as sailfin catfishes. All specimens of Pterygoplichthys from southeastern Asia lack an elevated supraoccipital process and have the supraoccipital bone bordered posteriorly by three scutes. 
       A group of four closely related species of Pterygoplichthys share these traits (Weber, 1991, 1992): P. multiradiatus, P. anisitsi, P. disjunctivus, and P. pardalis. Among these species, only P. anisitsi has light spots on a dark background, and only P. multiradiatus has a pattern of uncoalesced dark spots on a light background. Pterygoplichthys disjunctivus and P. pardalis possess a dorsal pattern of coalesced dark spots on a light background. Pterygoplichthys disjunctivus differs from P. pardalis in having dark spots on the venter coalesced to form a vermiculate pattern (Fig. 1); in P. pardalis the venter is covered with discrete spots (Fig. 2). Specimens at ZRC and UF are easily identified as P. pardalis and P. disjunctivus.

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