Watson, Keith & Marquet, 2007
Based on characteristics of fin osteology, subfamily Sicydiinae is divided into two tribes. Sicydiini Gill, 1860 is defined as having a broad based pelvic disc, fused to belly between all 5 rays and Sicyopini, new tribe, is defined as having a short based pelvic disc, fused to belly between fifth rays only. Akihito n. gen., Sicyopini, is described based onmaterial collected in freshwater streams in the island nation of Vanuatu. Akihito n. gen. is differentiated from all other genera in Sicydiinae by a combination of characteristics that include male with only conical and caniniform premaxillary and dentary teeth, female with few caniniform and numerous tricuspid premaxillary teeth and fine horizontal teeth in dentary; tongue free; large broad epural; male with midline scales much greater in height than length; and pelvic disc fused to belly between fifth rays only. Akihito vanuatu n. sp. is characterized by dorsal fins VI-I,10, spines 4, 5 and 6 filamentous in male and not in female; anal fin I,10; pectoral fin usually 16 (15-17); scales in lateral series: male 14-18, female 24-32; predorsal scales: male zero, female 0-2; belly: male naked and female with few cycloid scales close to anus; cephalic sensory pores usually A, B, C, D, F, H, N and O, pores K and L and associated posterior oculoscapular canal not usually present, all pores paired except pore D which is singular.
Key words. - Gobioidei - Sicydiinae - Akihito vanuatu - PSE - Vanuatu - New genus - New species - Freshwater.
Akihito n. gen.
Type species: Akihito vanuatu ♂ Watson, Keith & Marquet, 2007.
Etymology: Akihito: Named for Japanese Emperor Akihito for his many contributions to goby systematics and phylogenetic research.
Ecology: Akihito vanuatu is found in swift clear streams with rocky bottom. The stream near “Pauls conservation” in Ambae island is not perennial. In July 2002, when a part of the specimen were caught, there was no running water in the river and the species was found in small or large pools grooved in the main rock. This absence of running water during a part of the year involve a real adaptation of the species life cycle. Indeed, all larvae of Sicydiins need to go to the sea to complete their development and then, after few weeks spent in the sea, they need to recolonize rivers for growth and reproduction (Keith, 2003). In this particular case of no perennial stream, the new species needs to use heavy rains to migrate to the sea or to the river. The site where the mature specimens where found is situated at an altitude of 300 m. Feeding habits have not been studied in depth but the few specimens examined seemed to feed on aquatic insects and crustacean.
Distribution: currently known only from the island nation of Vanuatu.
Watson, R.E., P. Keith, & G. Marquet 2007: Akihito vanuatu, A New Genus and New Species of Freshwater Goby (Sicydiinae) from the South Pacific. Cybium. 31(3): 341-349.