HALF-SPOTTED GOBY
Asterropteryx semipunctatus Rüppell, 1830
     These gobies are abundant in the coral rubble of silty, well protected lagoons, bays and reef flats, usually perched in front of small holes into which they quickly disappear when alarmed. Kane`ohe Bay and Ala Moana Beach Park, O`ahu, are good places to see them. Their dark gray bodies are peppered with tiny blue spots, especially on the lower half (thus both the common and species names). The first three dorsal spines are usually prolonged into filaments. Mature females have one to seven yellow spots on the base of the tail. Lisa Privitera of the University of Hawai`i has found similar spots on small males, suggesting that they mimic females in order to "sneak" close to a spawning pair and release their own sperm. These gobies bob up and down rhythmically when they detect a predator, such as a lizardfish, or when they sense an injured goby nearby. Bobbing may have a dual function, both telling the predator "I see you" and warning other gobies of danger. To about 2 1/2 in. Indo-Pacific. Photo: Käne`ohe Bay, O`ahu. 2 ft.