Variation In Abundance And Size-Structure Of Populations Of The Small Chiton, Acanthochitona Retrojecta

Abstract

Hierarchically-nested sampling designs were used to test hypotheses about the population ecology of the small chiton Acanthochitona retrojecta (Pilsbry) in coralline algal turf on rocky shores near Sydney, Australia. Spatial sampling in January 1998 demonstrated that these small chitons were more abundant in mid-than in low-shore areas and more abundant on shores north of compared with those south of Sydney Harbour. Densities of A. retrojecta were extremely high, often exceeding 3500/m 2 . Temporal sampling showed there was little variation in the total abundance of A. retrojecta at scales of weeks and months. Nevertheless, there were significantly more juvenile chitons in June and July, which was offset by a reduction in the abundance of adults at the same time. The lengths of chitons ranged from 0.59 mm to 9.56 mm and size-frequency distributions demonstrated that A. retrojecta recruits continuously throughout the year. Several aspects of the population ecology of A. retrojecta differed greatly from those of previously studied species of larger chitons. These differences may be a function of the unique biology of A. retrojecta or be related to its unusually small size. More information is needed on other species of small chitons before general patterns of difference can be properly evaluated.

Diversity and temporal variation of peracarid fauna (Crustacea: Peracarida) in the shallow subtidal of a sandy beach: Playa América (Galicia, NW Spain)

“…Marine soft‐bottom fauna is frequently composed of a large number of species, which show different patterns of distribution and temporal dynamics (Rhoads & Young 1970). The study of these patterns is paramount, when determining the conditions and quality of marine benthos and for management of biodiversity and natural resources (Kelaher & Cole 2005).…”

Body size structure, biometric relationships and density of Chiton albolineatus (Mollusca: Polyplacophora) on the intertidal rocky zone of three islands of Mazatlan Bay, SE of the Gulf of California

“…Additionally, information on factors such as topography, tidal height and wave exposure, that may affect their ecology and limit their distributions, is only available for a few species (Andrus & Legard 1975, Otaíza & Santelices 1985, Smith & Otway 1997, Harper & Williams 2001, Kelaher & Cole 2005, Jörger et al 2008.…”

Effects of short-term rain events on mobile macrofauna living on seawalls

“…The chiton Acanthochitona retrojecta, a small species that lives almost exclusively in cryptic habitats, such as coralline turf, oysters and mussels (Kelaher & Cole, 2005), also showed a response to rain. The abundance of A. retrojecta in coralline turf was greater during the rain than when it was not raining.…”