ABSTRACT
Only a small number of extant fi sh groups show adaptations to amphibious lifestyle (Graham, 1997). Among them, mudskippers stand out as one of the largest groups that volitionally emerge from water and spend a signifi cant portion of time on mudfl at surface. Th e term “mudskippers” typically refers to four genera of oxudercine gobies (Gobiidae: Oxudercinae) including Boleophthalmus, Periophthalmodon, Periophthalmus, and Scartelaos. Species of Periophthalmus are the most terrestrial of the four genera: Periophthalmus mudskippers have been observed to remain emerged even during high tide, perching on rocks and stems of mangrove trees and other halophytes (Ikebe and Oishi, 1996, 1997; Takita et al., 1999; Zhang et al., 2003). Th e degree of terrestriality of Periophthalmodon mudskippers seems to vary between
species. Zhang et al. (2003) reported that Pn. septemradiatus oft en spends more than 30 min on an exposed mudfl at, whilst Pn. schlosseri stays at the water’s edge during both low and high tide. In addition, Milward (1974) inferred that Pn. schlosseri remains inside its burrow when the burrow openings are covered by high tides. Boleophthalmus and Scartelaos species are more aquatic; neither ventures far from water pools on the mudfl at and both appear to reside in their burrows during high tide (Milward, 1974; Zhang et al., 2000; Lee et al., 2005). More recently, Polgar and Crosa (2009) reported on the habitat characteristics of seven Malaysian mudskippers (B. boddarti, B. pectinirostris, Pn. schlosseri, Ps. chrysospilos, Ps. gracilis, Ps. variabilis, and S. histophorus). Their analysis basically confi rmed earlier fi ndings of diff erent affi nities to terrestrial environment among the mudskipper genera, but also indicated possible influence of predation pressure on mudskipper’s distribution on tidal flats. In spite of the alleged burrow confi nement of more aquatic mudskippers during high tide, observations of underwater activities of mudskippers are oft en obscured by generally high turbidity of water inundating the mudfl ats, and therefore direct confi rmation of the supposition is diffi cult. Males of all mudskipper species probably reside in burrows during egg care (see section on Reproduction). Murdy (1989) published a cladistic analysis of oxudercine gobies, and verified 5 species belonging to the genus Boleophthalmus, 3 to Periophthalmodon, 12 to Periophthalmus, and 4 to Scartelaos. To our best knowledge, fi ve new Periophthalmus species have been reported thereaft er (Ps. magnuspinnatus, Lee et al., 1995; Ps. spilotus, Murdy and Takita, 1999; Ps. walailakae, Darumas and Tantichodok, 2002; Ps. darwini, Larson and Takita, 2004; Ps. takita, Jaafar and Larson, 2008). In addition, Jaafar et al. (2009) claimed that Ps. novemradiatus includes two species (i.e. Ps. novemradiatus and Ps. variabilis). Th is brings the total number of Periophthalmus species to 18*. No new species have been reported for the other three genera. Th e distribution of mudskippers centers mainly in the tropical Indo-Pacifi c. Th e known localities of Boleophthalmus and Scartelaos species are similar, ranging from the Red Sea throughout the East Asian countries, and south to the tropical regions of Australia. Th e distribution of Periophthalmodon species is more restricted to Southeast Asia and mid-northern Australia. Periophthalmus species show the widest distribution among mudskippers, from west coast of Africa to Polynesian islands (Murdy, 1989).
