A Microtomographic Osteology of the Supraoccipital Hook of Nurseryfish,Kurtus gulliveri(Perciformes: Kurtidae)

Abstract

The Nurseryfish, Kurtus gulliveri, is known for “forehead brooding” parental care behavior in which the adult male carries the egg mass on a hook that overhangs the “forehead” region. This hook is derived from the supraoccipital bone, and it has been suggested to be formed through absorption rather than growth of the supraoccipital crest (SOC). Here we employed X-ray microtomography to investigate the neurocranium with focus on occurrence of the supraoccipital hook in a series of specimens from postflexion larva to adult male and female (10–200 mm SL). A slit-like cavity filled with soft tissue but not spongy bony tissue was revealed in the SOC in all examined specimens except the two smallest larvae (<15 mm SL), thus the cavity appears in the late postflexion-stage. The SOC can be divided into three parts from anterior to posterior in juveniles and adult females by reference to the cavity. 1. The crest rostrum is the most anterior end of the supraoccipital, and it increases in height with a sloped dorsal...