Dominance of Intergrades of Invasive Suckermouth Armoured Catfishes Pterygoplichthys spp. (Siluriformes: Loricariidae) in Coastal Wetlands of West Bengal, India

Abstract

Unauthorized introduction of South American suckermouth armoured catfishes (Loricariidae) of the genus Pterygoplichthys into the waste water bheries of East Kolkata Wetland, West Bengal has led to their noticeable naturalization in this ecosystem. A total of 439 specimens collected during this study were externally evaluated for affirming the species identity. Morphometric traits of the specimens were found to have unimodal distribution, but pattern of body colouration, especially of the belly (the main diagnostic character for the species identification of this genus) were found be very diverse. Abdominal patterns analysis revealed that 27% specimens were closely related to Pterygoplichthys pardalis or Pterygoplichthys disjunctivus and remaining 73% have intermediary coloration pattern of unknown identity. Forty one specimens were identified as P. disjunctivus with abdominal pattern including light and dark vermiculations formed as a result of coalescence of spots and seventy seven has discrete black spots on the ventral side of the body identical to P. pardalis. All the 22 sampling localities were found to be dominated by intermediary forms, which are possibly the introgressive hybrids between P. pardalis and P. disjunctivus or specific Pterygoplichthys species with varied abdominal pattern as they have significant plasticity to change the colour. To affirm the species identify it is recommended that multiple molecular tools be used in future studies.