Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay,New South Wales

Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.     

Proposal for adoption of the base of the Undulograptus austrodentatus Biozone as a global Ordovician stage and series boundary level

The base of the Undulograptus austrodentatus Biozone appears to be a synchronous event that is widely recognizable within graptolitic facies around the world. It occurs within an interval in which graptolite species ranges are now well known and in which there is a rapid turnover in the composition of graptolite faunas. This turnover reflects the rapid evolutionary radiation of the Diplograptacea simultaneously with the appearance of several distinctive pseudisograptid and glossograptid species. These events provide the basis for the recognition of two thin but widely applicable subzones; a lower Arienigraptus zhejiangensis Subzone and an upper U. sinicus Subzone. The occurrence of the lower boundary of the U. austrodentatus Biozone within a succession of first appearances also permits accurate and reliable identification of the boundary as well as assessment of stratigraphic completeness across the boundary interval in correlated sections. Diverse graptolite faunas of late Yapeenian and early Darriwilian age occur in association with the Histiodella altifrons Biozone of the North American midcontinent conodont zonation and the Paroistodus originalis and Microzarkodina parva biozones of the North Atlantic conodont zonation. They also occur in association with the shelly-fossil zonations developed for several different continents. These features of the base of the U. austrodentatus Biozone make it a suitable level for use as the boundary level for a global stage. Its stratigraphic position within the Ordovician System relative to other likely global stages as well as its coincidence with one of the major events in graptolite evolutionary history suggest that this level also may be a suitable level for the base of a global Middle Ordovician Series.Ordovician System, Ordovician stages, graptolite zonation, chronostratigraphy, international correlation. Charles E. Mitchell and Jörg Maletz, Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260-1550, USA; 13th July, 1994; revised 22nd May, 1995.     

The ground parrot (Pezoporus wallicus Kerr) in south-eastern Australia: a fire-adapted species?

The ground parrot (Pezoporus wallicus) has a coastal distribution in Victoria and has declined in range since European colonization. Its habitat consists of two major vegetation communities: coastal heathland and sedgeland. These are further divided into various sub-communities. These habitats contained high densities of cyperaceous and restionaceous plants, the seeds of which form the bulk of the bird's diet. Seeds and small fruits of some dicotyledonous plants and grasses are also eaten. Seed production by sedges remains fairly constant over time in sedgelands but varies in heathland, depending on time since burning. This variation is reflected by parallel changes in ground parrot population density. Both long unburnt and very frequently burnt heathlands are unsuitable for ground parrots. The birds also require dense vegetation cover. Ground parrots appear to live in territorial breeding pairs with enforced natal dispersal. This is an adaptation to an environment where habitat is patchily distributed in space and variable in quality over time.     

Ecophenotypic strategies of dalmanellid brachiopods

General ecophenotypic patterns, of particular interest when they apply to all, or most, taxa of the group concerned, can never be demonstrated until after monophyletic taxa have been recognized, that is, until after the initial stages of phylogeny construction have been carried out. In criticizing certain dalmanellid phylogenies, and based in large part on a study of five 'species subgroups'. Hurst & Watkins (1978; Geologica et Palaeontologica 12 ) postulate ecophenotypic patterns for Isorthis , and Hurst (1978; Palaeontology 21 ) postulates general patterns of ecophenotypic variation for dalmanellid brachiopods. These patterns may be invalid for four reasons: (1) Univariate and 'bivariate' statistical analysis of the samples used to define the five subgroups reveals no significant differences between subgroups, or vertical trends, for the very morphological characters claimed to exhibit the ecophenotypic patterns; (2) Hurst & Watkins' discriminant function analysis contains procedural errors and its results are ambiguous; (3) several of the five subgroups represent mixtures of unrelated taxa; (4) in recognizing the alleged patterns, Hurst & Watkins ignored contrary evidence from many taxa (and from many dalmanellid studies). □ Brachiopoda, Dalmanellidae, Silurian, ecology, evolution, systematics.     

A comparative study of the life style of two Jurassic irregular echinoids

The irregular echinoids Plesiechinus ornatus (Buckman) (Pygasteroida) and Galeropygus agariciformis (Forbes) (Cassiduloida) occur together in beds of the murchisonoe Zone, Bajocian, outcropping in the Cheltenham region of Gloucestershire. These species were largely restricted to different lithofacies within the carbonate shelf environment. Both adopted a hidden mode of life but achieved this by different techniques. Plesiechinus had fairly short spines and strongly muscular podia over the whole corona and was able to cover itself with coarse substrate particles. The oral tubercles are bilaterally symmetrical and are radially arranged. The oral spines are thought to have pulled sediment out from beneath the test, excavating a small depression for it. Galeropygus bore a dense covering of very small spines and its tube feet were differentiated into aboral respiratory podia and oral suckered podia. It had a preferred anterior direction of locomotion and is thought to have buried itself completely by excavating and ploughing into the substrate as it moved forward. Plesiechinus fed using only its lantern and postulated peristomial tube feet, whereas Galeropygus was a continugus sediment swallower and used its phyllode tube feet and peristomal lip spines in transferring particles towards the mouth.     

Species-Recognition in the Field Cricket, Teleogryllus oceanicus: Behavioral and Neural Mechanisms

SYNOPSIS. Field crickets depend on acoustic organs to detectthe presence of potential predators as well as conspecific crickets.Predators are recognized largely on the basis of spectral frequenciesthat are contained in their acoustic signals. Puffs of air andvery low frequencies activate a cricket's cereal receptors andultrasonic frequencies activate their tympanal organs. Bothof these acoustic stimuli release "escape behavior," in theform of evasive movements. An identified neuron sensitive toultrasound is described. Crickets recognize singing conspecificsby both frequency and temporal properties of cricket songs;however species recognition requires specific temporal informationin calling songs. While previous studies have emphasized therole of songs on female behavior, males also recognize conspecificsongs; sexual differences in recognition behavior occur.     

A reappraisal of the concept of metabolic cold adaptation in polar marine invertebrates

The concept of 'metabolic cold adaptation', namely that polar marine ectotherms are adapted in having an elevated basal metabolic rate, has been examined in the light of recent biochemical, physiological and ecological data for Antarctic marine organisms. It is now clear that marine invertebrates from Antarctic waters are characterized by slow growth rates, low basal metabolism and reduced annual reproductive effort, and there is thus no clear evidence of the traditional view of an elevated metabolic rate. By analogy with fish, protein synthesis rates are probably also low. This suggests that the major feature of cold adaptation is a reduction in the individual total annual energy intake in comparison with ecologically similar organisms from warm water. This allows a high standing crop of suspension feeders to develop, and low temperature is thus a significant factor in the successful widespread adoption of typical K-strategies in Antarctic marine invertebrates.