Sea‐level changes and palaeo‐ranges: reconstruction of ancient shorelines and river drainages and the phylogeography of the Australian land crayfish Engaeus sericatus Clark (Decapoda: Parastacidae)

Historical sea levels have been influential in shaping the phylogeography of freshwater‐limited taxa via palaeodrainage and palaeoshoreline connections. In this study, we demonstrate an approach to phylogeographic analysis incorporating historical sea‐level information in a nested clade phylogeographic analysis (NCPA) framework, using burrowing freshwater crayfish as the model organism. Our study area focuses on the Bass Strait region of southeastern Australia, which is marine region encompassing a shallow seabed that has emerged as a land bridge during glacial cycles connecting mainland Australia and Tasmania. Bathymetric data were analysed using Geographical Information Systems (GIS) to delineate a palaeodrainage model when the palaeocoastline was 150 m below present‐day sea level. Such sea levels occurred at least twice in the past 500 000 years, perhaps more often or of larger magnitude within the last 10 million years, linking Victoria and Tasmania. Inter‐locality distance measures confined to the palaeodrainage network were incorporated into an NCPA of crayfish (Engaeus sericatus Clark 1936) mitochondrial 16S rDNA haplotypes. The results were then compared to NCPAs using present‐day river drainages and traditional great‐circle distance measures. NCPA inferences were cross‐examined using frequentist and Bayesian procedures in the context of geomorphological and historical sea‐level data. We found distribution of present‐day genetic variation in E. sericatus to be partly explained not only by connectivity through palaeodrainages but also via present‐day drainages or overland (great circle) routes. We recommend that future studies consider all three of these distance measures, especially for studies of coastally distributed species.     

Ultrastructure of the loop of terebratulide brachiopods

The folded and twisted calcareous ribbon, forming both the ascending and descending lamellae of the loop of Waltonia inconspicua (Sowerby), is a two-layered structure consisting of a wedge of regularly stacked secondary layer fibres that overlie a thin layer of non-fibrous calcite (herein termed brachiotest). On one surface, that facing into the mantle cavity, secondary fibrous mosaic predominates, but smooth, finely banded brachiotest occurs as a narrow marginal lip upon which secondary layer fibres proliferate and progressively overlap. This growing edge of the ribbon is secreted by long, folded epithelial cells with digitate extensions to their apical plasmalemmas, which are distinguishable from the cuboidal epithelium-secreting fibres and their membranous sheaths. The other surface, facing the body cavity and the brachial coelom, consists entirely of roughened brachiotest exhibiting prominent banding that is aligned parallel to the growing loop edge. This surface is overlain by microfilamentar epithelium acting as a holdfast for the connective tissue frame of the lophophore. The other edge of the ribbon consists of truncated sections of both secondary-layer fibres and brachiotest which bear signs of resorption consistent with the degenerated state of the associated epithelium. Growth of the Waltonia loop is controlled by these localized processes of secretion and resorption of the fibrous and brachiotest layers and is typical of all terebratulides so far studied. The brachiotest is not homologous with the non-fibrous primary shell secreted at the valve margin. □ Brachiopoda, Articulata, Terebratulida, ultrastructure, lophophore, loop.     

Boring Mechanism of Polydora websteri Inhabiting Crassostrea virginica

The boring mechanisms of species of polydorid polychaetes arelittle understood due to lack of experimental evidence and directobservations. In the present studies the boring mechanism ofadults and metamorphosing larvae of Polydora websteri was investigatedby (1) inducing adults and larvae to settle against test substrates,(2) observing behavior in natural burrows and in "artificialblisters" composed of transparent "Pliobond" films surroundingIceland spar substrates, (3) removing the giant setae of wormspriorto tests of boring, (4) applying the giant setae to substrates,and by (5) testing for production of acid. All the layers of oyster shell, including conchiolin, were bored.Calcareous substrates andIceland spar were penetrated rapidlyby adults without the assistance of the giant setae. Nor werethese organs essential to the boring of a larva. A characteristictype of behavior involving close contact with the substrateduring backwards and forwards movements and periods of immobilityalways preceded boring. The worms produced acid, probably somecommon product of metabolism, which can account for these results.     

Mutagenesis of Clostridium acetobutylicum

Mutagenesis of the obligate anaerobe Clostridium acetobutylicum was best accomplished using agents (e.g. ethyl methane sulphonate or N -methyl- N '-nitro- N -nitrosoguanidine) which are believed to act by a direct mutagenic mechanism. Other agents (e.g. u.v. radiation) whose effectiveness relies on misrepair of damaged DNA via an error-prone pathway, were poor mutagens of this organism. Procedures are described which readily yielded a variety of auxotrophic and other useful mutant strains of Cl. acetobutylicum and related saccharolytic clostridia.     

Elevated metabolic costs while resting on water in a surface feeder: the Black-legged Kittiwake Rissa tridactyla

Measurements of the energy costs of individual behaviours provide insights into how animals trade-off resource allocation and energy acquisition decisions. The energetic costs while resting on water are poorly known for seabirds but could comprise a substantial proportion of their daily energy expenditure. We measured the cost of resting on water in Black-legged Kittiwakes Rissa tridactyla , a species which does not fly during the night and for which estimating energy expenditure while resting on the water is therefore important. Their resting metabolic rate on water at 12.5 °C was at least 40% higher compared with resting at the same temperature in air. This indicates that, at comparable temperatures, metabolic costs are elevated for birds resting at sea compared with on land. We argue that Kittiwakes meet much of this extra thermoregulatory demand by dedicated metabolic activity. During the winter months, their costs are likely to be even higher owing to lower sea temperatures. Accordingly, we suggest that migration to milder latitudes, following breeding, will provide enhanced benefits, particularly to seabirds such as Kittiwakes which rest on the sea surface during darkness.