Materials and methods
Sample collection
The Trichopsis fishes in this study were wild caught and only adults were used for experimentation. T. vittata were the most widely spread: from 9 provinces in the central plain of Thailand, 5 provinces in the north, 12 in the northeast, 4 in the west, 7 in the east, and 6 in the upper peninsula of Thailand. Bangkok is considered to be at the center of the country (see Table 1 and Fig. 1). In addition, there were T. vittata catch sites in 2 provinces in Cambodia, 1 in Lao PDR and 1 in Vietnam. T. schalleri were from 8 provinces in the northeast of Thailand and 1 province in Lao PDR whereas T. pumila were caught in 2 central, 4 eastern and 1 western provinces of Thailand, plus 1 province in Cambodia.