Barry Wilson

Survival and reproduction of the mussel Xenostrobus securis (Lam.) (Mollusca: Bivalvia: Mytilidae) in a Western Australian estuary

Summary The Swan estuary is subject to extreme temporal and spatial variations in salinity. Downstream populations of the mussel Xenostrobus securis (Lamarck, 1819) are exposed to a seasonal range from 1·5‰. Cl to 20·0‰. Cl. In summer the estuary is progressively filled with saline water from the sea; in winter it is flooded by fresh river run-off water from the heavy and concentrated winter rains. The autumn fall in salinity is usually very rapid and constitutes a severe physiological shock for organisms inhabiting the estuary. The physiography and hydrology of the Swan estuary are described. Experiments are reported on the salinity tolerance and behavioural responses to salinity stresses of adult mussels and larval stages. Adult mussels show no ability to osmoregulate (except possibly at very low salinities). They can tolerate environmental chlorinities at least as high as 31‰. Cl and can withstand sudden dilutions from at least 18‰. down to 1‰.. They are capable of survival at 1‰. for many months. Clos...

New Species and Records of Volutidae ( Gastropoda) from Western Australia

Four new deep water species of volutid genera Amoria, Notovoluta, Notopeplum ,and Volutoconus are described from the central west coast of Western Australia. Another species of Notovoluta, previous...

An Overview of the Historical Biogeography of the North West Shelf

This chapter presents a provisional overview of the evolution of the marine benthic shelf, shore, and reef fauna of the North West Shelf and interprets observed distribution patterns in terms of geological, evolutionary, and biogeographic history. It takes account of climate change and modes and means of larval development and dispersal. The modern marine shelf fauna of the region is derived from the ancient pantropical Sea of Tethys with origins in the Mid Tertiary collision of the Australian and Eurasian plates as a result of continental drift. Coral reef species and others that have pelagic larvae appear to have quickly colonized Australian habitats. However, the fossil record of certain molluscan genera that lack a pelagic larval stage shows that they originated on the Sunda Shelf, invaded and flourished on the Australian shelf in the Miocene or earlier, but became isolated from the place of origin by tectonic changes to regional bathymetry. A wide carbonate platform that formed across the northern Australian margin in the Miocene allowed the spread of Tethyan species down both sides of Australia. Demise of that platform in the Early Pliocene splits the northern Australia tropical marine fauna into isolated western and eastern parts. Western and eastern sister species of marine benthic invertebrates may be explained by these vicariant events. Brief phases of high sea level in the Quaternary opened the Torres Strait connection between the Arafura and Coral Seas but have not played a major subsequent connectivity role in the evolution of the northern Australian marine fauna. The conclusions reached are (1) from the Miocene until the Early Pliocene there existed a uniform Northern Australian Biogeographic Province within the Indo-West Pacific Realm and (2) since the Middle Pliocene the tropical western and eastern marine regions have been separate biogeographic provinces, isolated by the Torres land bridge—the name Dampierian may be used for the northwestern province.

Patterns of Life and the Processes That Produce Them

Species are not randomly distributed. Their distribution patterns are governed by historical and contemporary environmental factors that are subject to ongoing change. Common distribution patterns of marine invertebrates on the North West Shelf, and the key biological and environmental factors that determine them, are discussed in this chapter. Biodiversity in the region is very high as a consequence of close proximity to the worlds most diverse bioregion in the Central Indo-West Pacific, its wide carbonate shelf and diverse habitats, its complex history of eustatic sea level change, and the presence of biogeographic barriers to dispersal that have promoted speciation. The prevalence of contemporary allopatric distributions among the shore and benthic shelf communities indicates a history of fragmentation of ancestral geographic range, with a high level of regional endemism the result. This does not apply to the oceanic coral reef communities of the shelf margin which operate on a different connectivity system and exhibit wide distributions and no endemism.

A New Species of Pterynotus (Gastropoda: Muricidae) From Western Australia

Summary A new species, Pterynotus (Pterochelus) westralis, is described from the south-western continental shelf of Australia. The radulae of two other species of Pterynotus are described.