No description available.

Calvert's Lagoon, a land-locked, brackish lagoon on the south-east coast of Tasmania, Australia, serves as a focus for the life-cycles of a wide variety of digenetic trematodes. A gastropod, Coxiella badgerensis (Johnston), is the only molluscai inhabitant, and it is heavily infected by trematodes throughout the year. The incidence of primary trematode infections was found to vary seasonally, with a peak in autumn. Developmental stages of 17 species from 7 trematode families were recorded in snails collected at the lagoon from April 1976 to September 1978. In order of abundance'of primary infections, the families were: Microphallidae (3spp.), Schistosomatidae (lsp.), Notocotylidae (4spp. 1, Renicolidae (2spp.) Psilostomidae (3spp.) , Heterophyidae (3spp.) and Strigeidae (lsp.). Gravid adults of 9 of these species were found infecting a wide range of birds at the lagoon, including swans, ducks, grebes, dotterels and coots. Two of the flukes, Apatemon gracilis (Rudolphi) and Psilochasmus oxyurus (Creplin) are cosmopolitan; however the geographical distributions of the others are unknown. About 80% of primary trematode infections at the lagoon were caused by the 3 microphallid species: Maritrema calvertensis Smith, Levinseniella tasmaniae (Smith) and Atriophallophorus coxiellae Smith. M. calvertensis and L. tasmaniae have typical 3 host life-cycles, however, A. coxiellae is one of 10 known microphallids that exhibit a reduced life-cycle, with metacercarial cysts being formed in the molluscan host. The daughter sporocysts and xiphidiocercariae of M. calvertensis and L. tasmaniae are distinguished by several morphological characteristics. The behaviour and ecology of the cercariae were also found to differ in ' many respects. There is a distinct periodicity in the patterns of emergence of both cercariae from their snail host, however the cercaria of L. tasmaniae emerges during the day, wiiereas that of M. calvertensis emerges at night. Although both species encyst in the amphipod Austrochiltonia australis gayce)only M. calvertensis is infective to the ostracod, Mytilocypris tasmanica McKenzie. Metacercarial cysts of L. tasmaniae induce a colour change, from green to bright orange, in the amphipod host. The hoary-headed grebe, the most abundant bird at Calvert's Lagoon, harbours the minute adults of each of the microphallids: L. tasmaniae inhabits the intestinal caeca and Maritrema calvertensis and Atriophallophorus coxiellae have overlapping, but different distributions in the lower small intestine. The life-cycles of the three microphallids, the psilostomes Psilochasmus oxyurus and Psilostomum spp.A and B, and the notocotylids Paramonostomum bursae n.sp. and P. caecai n.sp., were demonstrated experimentally. Growth and development in laboratory ducklings were studied. At Calvert's Lagoon, gravid adults of dpatemon gracilis were found in a black duck, and intramolluscan stages were found in C. badqerensis, however no second intermediate host was found. Metacercarial cysts of A. qracilis were found infecting the freshwater Q native fish, Galaxias auratus Johnston, at Lake Crescent, about 100 km NW of Calvert's Lagoon, (life-history notes on A. qracilis and another strigeoid, Diplostomum qalaxiae n.sp., infecting G. auratus at Lake Crescent, are presented in Appendix 2). A comparison was made of the in vitro development of metacercariae of the 3 microphallids developing in C. badgerensis atcalvert's Lagoon, and 4 microphallids, Gynaecotyla hickmani n.sp., G. macrocotylata n.sp., Maritrema eroliae Yamaguti and Microphallus paraqrapsi n.sp., that encyst in an estuarine crab, Paragrapsus gaimardii (M. Edw.), at Bruny Island, about 20 km SW of Calvert's Lagoon (descriptions of the microphallids infecting P. qaimardii are presented in Appendix 3). All of the microphallids produced eggs in vitro; however, the rates of egg production in different culture media varied between species. A direct relationship is suggested between the longevity of each species in its definitive host and its nutritional requirements in vitro, such that very short-lived flukes, like L. tasmaniae, relying on endogenous food reserves, can produce eggs at normal rates in balanced salt solution, whereas relatively long-lived flukes require more complex culture media for normal development. Preliminary investigations of the ecology of other water bodies in Tasmania revealed that the trematodes found at Calvert's Lagoon are widely distributed on the E and NE coasts of Tasmania in enclosed, brackish lagoons inhabited by C. badgerensis. The distributions of these trematodes probably extend to similar water bodies that occur on the Bass Strait Islands and in the SE of the Australian mainland.

This thesis describes results of a comprehensive study of the Tamar Estuary, a highly flushed system in northern Tasmania, conducted to investigate the link between hydrodynamic processes and zooplankton biomass with particular emphasis on larval fish dynamics. It comprised extensive plankton sampling together with measurements of physical parameters, between October 2001 and November 2002, including three 24-hour sampling sessions in the lower estuary to ascertain the effect of tidal currents in the transport of fishes. The Tamar was classified as a partially mixed estuary (Type 2a), based on salinity distribution, current velocities and freshwater flow. The weak vertical temperature and salinity stratification, together with strong mean current velocities (2 m/s), indicated a lack of two-layered circulation, and hence absence of a net upstream flow along the bottom. The study yielded 80,837 larval fishes representing 44 families, with catches dominated by gobiids, blenniids, clinids and engraulids. Temperature was found to be the most important variable driving temporal changes in zooplankton biomass and larval concentrations. Peaks in zooplankton biomass and larval concentrations occurred simultaneously in November, both in 2001 and 2002, at temperatures approx. 15 C, and lasted approx.2 months. Results suggest that the commencement and intensity of spawning in the Tamar may be triggered by changes in abiotic factors, such as increasing temperature and moderate freshwater flow, whereas spawning duration may be linked to biotic factors such as the presence of potential predators and food availability. No evident pattern in the spatial distribution, both of zooplankton biomass and larval fishes was observed during the peak abundance period. The spatial structuring of the larval assemblage was driven by salinity, with one assemblage representing mostly estuarine-spawned larvae (mouth to 35 km upstream), and the other representing larvae of freshwater taxa (>35 km). The geographical extent of each assemblage could be associated with the strong diffusive forces of tidal currents, which also affected zooplankton biomass. An estuarine transport model used to investigate fish movements along the lower estuary was able to accurately predict concentrations of virtual larvae early in the season, as they behaved similar to passive particles. However, it was unable to accurately predict concentrations later in the season, likely because most larvae were displaying a behaviour different to passive particles due to increased swimming ability. Strategies likely helping retention and survival of larvae in the Tamar Estuary include a short (approx.months), defined occurrence period that is well-timed with zooplankton production, and location where these larvae are spawned within the estuary.

Although snow petrels are ubiquitous around the Antarctic, population estimates of this “not so charismatic” top predator are generally limited. Such information is highly valuable for the monitoring and management of Antarctic and Southern Ocean ecosystems, especially in a climate change context. There is a need to complement long–term temporal demographic information obtained at a limited number of monitoring sites with spatial distribution data. Systematic surveys of snow petrels and Wilson’s storm petrels were undertaken at Casey (2002-2003) and Mawson (2004-2005) in order to provide better regional population estimates and test the performance of predictive distribution models based on topographic and substrate variables for refining such estimates. As habitat selection modelling is rarely used in Antarctic regions, methodological developments focus on dealing with the peculiarities of a semi-colonial hollow-nesting species, testing habitat selection modelling approaches and comparing the output of four types of models (Generalized Linear and Generalized Additive Models, Classification Trees and Ecological Niche Factor Analysis) across a range of scales. Snow petrel nest distribution was directly related to the nature of the rock substrate and to major topographic/geomorphological parameters such as hill slope and the direction of the prevailing winds. Model performance varied with the scale at which models were implemented, suggesting that nest selection processes happen predominantly at the habitat unit and individual nest scales. Further study at the nest scale highlighted that the influence of biotic related parameters such as conspecific attraction (modelled as autocorrelation due to coloniality) may be of lesser influence than selection based on individual nest quality. An alternative modelling method, ENFA, which creates environmental envelopes for the niche of the species with presence data only was identified as valuable for Antarctic data sets, which often lack comprehensive records of species absence. The validation of the models created at Casey with nest data collected in the Mawson region returned satisfactory prediction rates in two different habitat types, coastal islands and inland mountains, suggesting that it may be possible to predict snow petrel distribution across East Antarctica using remotely sensed information on topography and geomorphology, for example high-resolution aerial photography to guide in the design of and complement ground surveys. Similar modelling procedures applied to Wilson’s storm petrels produced more mitigated results and selection for this species appeared to be based principally on nest microhabitat characteristics. However, modelling provided useful information on the large-scale habitat preferences and ecological requirements of both species

No description available.

No description available.

No description available.

The New Zealand glowworm Arachnocampa luminosa (Diptera: Mycetophilidae) provides the national tourist industry with a unique attraction. The Glowworm Cave at Waitomo has an international reputation for the bioluminescent display produced by A. luminosa. The aim of the present study was to investigate glowworm ecology in the tourist caves at Waitomo, the results to provide factual information so that scientifically sound management procedures could be devised to ensure the long term survival of the population. The literature on all aspects of A. luminosa is reviewed. A continuous cycle of development occurs with most stages present throughout the year. However, the majority of the larval population pupates in late winter/early spring, producing a new generation in spring/early summer. There are five larval instars; the time for individual development in the Glowworm Cave varies considerably but is estimated to take 5 months on average. Distribution of glowworms is dependent on an adequate food supply, cool, moist climate and a suitable horizontal rock surface. Their diet consists of chironomids with some tipulids, ephemeropterans and trichopterans, most of which emerge inside the cave. Factors likely to influence distribution and productivity of benthic fauna in the cave are reviewed, including the importance of flooding and stream drift fauna in restocking the cave. Mortality is caused by two species of opiliones, cannibalism and a fungal pathogen identified as Tolypocladium sp. (Moniliales). Preliminary experiments with Tolypocladium indicate that the higher temperatures of the Glowworm Cave may be responsible for the prevalence of the fungus compared with non-tourist caves in the district. Observations on cave climate showed that the Glowworm Cave now has a higher range of temperature and relative humidity compared with earlier records and non-tourist caves at Waitomo. This is attributed in part to the free flow of air that occurs between the two entrances of the cave and the outside atmosphere. Reasons for the decline in the glowworm display that has occurred in the past few years are discussed. The installation of an open grille on the Top Entrance of the Glowworm Cave in 1975 is suggested as one of the main factors responsible. Future research projects are mentioned, together with recommendations for cave management related to glowworm ecology.

The structure and function of septate junctions have been studied by ultrastructural techniques in a wide range of invertebrate phyla. Techniques have included conventional and tracer impregnated tissue thin sectioning, and freeze-fracture of both fixed and unfixed tissue. Standard and goniometer stage transmission electron microscopy has been used. Work in this study has been concentrated mainly on the lower invertebrate phyla in which the simplest forms of junction might be seen, and on the higher invertebrate phyla. This latter group is of special interest in the transition region between the invertebrate and vertebrate phyla. Six new types of septate junction and a form of tight junction have been found in invertebrate phyla and are described. Two of these new septate junctions occur in each of the phyla Coelenterata, Echinodermata and Hemichordata. The tight junction occurs in the phylum Tunicata. Further data has also been obtained on five of the six previously described types of septate junction. The distribution of all twelve types within the invertebrates and their phylogenetic relationships are discussed. Work with the goniometer stage has aided in interpreting junctional structures. The results have revealed several features of the septate junction that support the idea that it has a mainly occluding function analogous to that of the vertebrate tight junction. In addition, an anastomosing septate junction has been found in the Echinodermata which is postulated to be a structural intermediate between the invertebrate septate junction and the vertebrate tight junction. A hypothesis is proposed suggesting how the septate junction might have evolved into the vertebrate tight junction. Tricellular junctional regions of most of the septate junction types are noted and briefly described.

In her classic review of the echinoderms, Hyman (1955), describes the ophiuroids as "the most successful echinoderm group living today". This success has largely been attributed to both their smaller size and their remarkable agility. Many authors have commented on their great importance in the bionomics of the sea; various species participate in food chains involving demersal fish and many others serve as agents for the disposal and recycling of organic materials on the benthos. Their wide occurrence in the marine environment, coupled with their dense numbers, has led to their inclusion in the nomenclature of benthic communities and sub-comnunities, particularly in European waters. Some 1,900 extant species, being referred to 255 genera, have no been described (Fell, 1960).