Opal Cling Goby  |  

The Opal Cling Goby has its first dorsal fin approximately the same height as the second. This physical difference can be a distinguishing characteristic for the species. In Australian habitats the Opal Cling Goby has been recorded at a maximum total length of 35 mm. Males and females differ in colouration, with males having a bright lateral band along the length of the body of vivid blue, green or pink that changes based on light reflectance in the water. Males have transparent dorsal and pectoral fins, a caudal fin that is transparent with mottled dark spots on the rays and an anal fin sooty in appearance with mottled blue flecks and a bright blue margin. Females are whitish-cream in colour with two horizontal black bands and a black spot on the caudal peduncle. Cling gobies are small, slender fish of the order Sicydiinae. Cling gobies get their name from the fused pelvic fins on their belly that form what is known as a ‘pelvic disk’ that assists them to adhere to rocks and submerged surfaces in the sometimes fast flowing streams in which they live. In Stiphodon species, the pelvic disk is attached to the belly only between the fifth pair of fin rays. Other species in the order Sicydiinae have the pelvic disk attached between all five of the fin rays on the belly. Cling gobies may also sometimes be known as ‘toothed-lip’ gobies, due to their outwardly pointing teeth in the upper jaw, that are tricuspid (having three pointed cusps) in shape. These teeth are replaced if they are lost. The number of teeth in an individual is also an aid in identifing specific species.