Spawning ecology of the Saint Paul's Gregory Stegastes sanctipauli, a damselfish endemic to the remote St Peter and St Paul's Archipelago.

We studied the spawning ecology of Stegastes sanctipauli, a damselfish endemic to the small and remote St Peter and St Paul's Archipelago (Brazil), aiming to determine the main correlates of reproductive success, as inferred from rates of egg losses along a spawning season. New clutches appeared mostly in the last quarter moon, when egg predation intensified. Predation by heterospecifics, particularly Halichoeres radiatus (Linnaeus, 1758), accounted for most egg losses, while filial cannibalism showed negligible influence. Predation pressure was highest for larger nests with higher initial density of eggs. Hatching of eggs occurred close to the new moon (i.e., ~5 days after spawning). Most nests occur in shallow reefs (<16 m depth), where main food resources for adults (turf algae) are concentrated, but abundance of egg predators, particularly H. radiatus, is also highest. This latter result suggests that the spawning activity of S. sanctipauli is influenced by the trade-offs between food accessibility by adults and egg predation risk. The patterns recorded here are similar to those known for other tropical damselfish species and may reflect strategies for attenuating predation pressure over new fry and eggs.

A new synapomorphy in the pelvic girdle reinforces a close relationship of Zanobatus and Myliobatiformes (Chondrichthyes: Batoidea).

The rays of the order Myliobatiformes present several diagnostic characters, the most striking one being the presence of a serrated sting on the dorsal region of the tail. Although several morphological hypotheses have been proposed supporting the monophyly and interrelationships of its members, few characters of the appendicular skeleton were employed. In the present study, we analyzed comparatively the pelvic girdle morphology across all the groups of rays to investigate the distribution of the ischial process. To understand its significance, we tested this character of the pelvic girdle as a potential synapomorphy for the Myliobatiformes plus Zanobatus. Accordingly, the phylogenetic position of Zanobatus as a sister taxon to Myliobatiformes is reinforced and its pelvic girdle morphology reinterpreted in relation to previous morphological studies.