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.