Cytoevolution, Phylogeny and Taxonomy in Epacridaceae

Chromosome numbers in Epacridaceae were collated from variousauthors and superimposed on to recent cladograms for the family.The results strongly indicate that reduction in chromosome numberoccurs with evolutionary advancement. Thus Epacridaceae, incommon with ‘Ericaceaesens. strict .’ and ‘Vacciniaceaesens.strict. ’, has evolved from a primitive karyotype of atleastx =12 and probablyx =13. This conclusion dispels earlierpaleopolyploid models based on a primitivex =6 in the family.Other aspects of cytoevolution, such as chromosome number asa generic character especially in cytologically advanced generaof the Styphelieae, are discussed. Cytoevolution; cladistic models; primitive character states for chromosome number; dysploid falls; cytotaxonomy; Epacridaceae; Richeoideae; Epacridoideae; Epacrideae; Styphelieae; Ericaceae     

Patterns in biogeochemical properties of sediments and benthic animals among different habitats in mangrove forests

Abstract Determining interactions between biological and physical structure of intertidal sediments and their relationships to ecological functioning is vital for improving our understanding of these complex habitats. If spatial and/or temporal variations in the benthos are related to properties of the sediment, one can infer that sediments should vary and change at similar scales to the benthos. The mangrove forests of Sydney Harbour, Australia consist of distinct subhabitats (termed MH1‐3, representing a change from open mudflat to canopied mangrove forest), which might affect benthos and, independently, properties of the sediment. This study tests the model that the benthos and sediment would respond to environmental differences between MH1–3 similarly in different locations and thus show consistent patterns of difference among habitats. Although general patterns of sediment properties and benthos were relatively similar, detailed patterns varied among locations. The relative importance of the different sedimentary properties varied in unpredictable ways among habitats in the different locations. Out of all the variables, only total carbohydrate was consistently important in driving differences among habitats in all three locations, but only between MH1 and MH2. That there were no other strong consistent differences between the different microhabitats in terms of the measured properties of the sediments indicates that there is more driving these patterns than a simple relationship to different habitat formed by mangrove forests and/or feedbacks between sediment properties and benthos. With respect to the benthic assemblage, in all bays MH1 and MH3 were the most different. The benthos showed stronger patterns relating to the different subhabitats than did the sediment, suggesting that there are important differences affecting these habitats that were not revealed by our suite of biogeochemical measurements of the sediment.     

Female nutritional status determines the magnitude and sign of responses to a male ejaculate signal in Drosophila melanogaster

Ejaculate chemicals transferred from males to females during mating cause significant changes in female behaviour and physiology, but the causes of phenotypic variation in these responses is little understood. We tested here the effect of adult female nutrition on the response of female Drosophila melanogaster to a specific ejaculate component, the sex peptide (SP), which is of interest because of its effects on female egg laying, sexual receptivity, feeding rate, immune responses and potential role in mediating sexual conflict. We exposed adult females to five different diets and kept them continuously with males that did or did not transfer SP. Diet altered the presence, magnitude and sign of the effects of SP on different phenotypic traits (egg laying, receptivity and lifespan) and different traits responded in different ways. This showed that the set of responses to mating can be uncoupled and can vary independently in different environments. Importantly, diet also significantly affected whether exposure to SP transferring males was beneficial or costly to females, with beneficial effects occurring more often than expected. Hence, the food environment can also shape significantly the strength and direction of selection on mating responses.     

The Fine Structure of the Cyst Wall of the Ciliated Protozoon Didinium nasutum1

SYNOPSIS. Electron microscope observations of the complex cyst wall of Didinium nasutum are reported. The cyst wall is composed of 3 major coats. The outermost coat, the ectocyst, consists of short strands of filamentous material which forms a diffuse, amorphous layer approximately 8–9 μ thick. Culture debris, bacteria and unidentified inclusions have been observed adhering to the outer coat. The mesocyst, approximately 2.5 μ thick, has 2 distinct regions. The outer region is differentiated into several slightly thicker layers which in face view have a honeycomb appearance. The deeper region of the mesocyst consists of compact lamellae lacking the obvious honeycomb appearance of the layers of the outer region. Finally, the endocyst (0.3 μ thick), which arises in the mature cyst in the space that develops between the pellicle and the mesocyst, consists of delicate fibrils in a compact matrix. Both mesocyst and endocyst may be undulant and folded. The structure, origin and possible relationships of the various coats composing the cyst wall are discussed. The present study also contributes information on the role and fate of mucocysts and other cytoplasmic structures during the formation of the cyst wall.     

Bioenergetics, Exercise, and Fatty Acids of Fish

The bioenergetic aspects of pentachlorophenol poisoning andexercise in fish are discussed. When cichlids are exposed to0.2 ppm of pentachlorophenol, the intake of food was increasedand energy losses were also increased. Growth was decreased.The cost of specific dynamic action was higher and the costof exercise was increased above the cost of similar exercisein nonpoisoned controls. In salmon swimming to exhaustion at52 cm/sec fatty acids 18:1, 16:0, and 16:1, and at 59 cm/secfatty acids 22:6, 18:2, and 20:4 suffered the greatest depletion.At 52 and 59 cm/sec, respectively, average exhaustion timeswere 1141 and 398 minutes; the equivalents of distance traveledwere 26.0 and 12.7 miles; the loss in lipids, 54 and 10 mg;and the average weight losses, 830 and 480 mg per salmon. Totalcaloric losses calculated from the data on lipid and weightlosses were approximately 1118 and 566 calories. Calculatedfrom the data of Brett (1964) on O₂ consumption, caloric losseswere estimated at only 344 and 188 calories. The differencebetween observed values and values calculated from the dataof Brett may lie in the duration and severity of the exercise.Brett collected his data on O₂ consumption on the basis of atmost two hours at high velocity. Possibly when maximum effortis involved each succeeding mile and each succeeding hour ismore difficult and more costly to the salmon.     

SPATIAL PATTERNS OF SHELL SHAPE OF THREE SPECIES OF CO-EXISTING LITTORINID SNAILS IN NEW SOUTH WALES, AUSTRALIA

The shape and relative weight of the shell have been shown tovary intraspecifically and interspecifically in a number ofspecies of gastropods, including many different littorinids.These differences give rise to different shell forms in differenthabitats. In those species which have non-planktotrophic development,differences in shell form among shores have been usually explainedin terms of natural selection because exposure to waves supposedlyfavours light shells with large apertures, while predation bycrabs on sheltered shores favours elongated, thick shells withsmaller apertures. Differences in shell shape among speciesfound at different heights on the shore have been explainedin terms of resistance to desiccation and temperature. Suchvariables would tend to act on a relatively broad-scale, i.e.causing differences among heights on a shore or among shores.Rates of growth, which might vary at much smaller scales withina shore, have also been shown to affect the shapes of many shells. In this study, the shape and relative weight of shells of threespecies of co-existing littorinids (Littorina unifasciata, Bembiciumnanum and Nodilittorina pyramidalis) were measured. These speciesall haveplanktotrophic development and they are found on manyshores where there is no evidence that they are preyed uponby crabs. Before explanations of shell shape are proposed, itis necessary that patterns of variation, within different partsof ashore and among different shores are clearly documented.These patterns were measured at a number of different spatialscales within and among replicate shores with different amountsof wave exposure. Large and small specimens were included toallow intraspecific comparisons among snails of different sizesfound at different heights on the shore. The results showedsignificant differences among shores in shape and relative weightof shells, but these differences could not be explained by exposureto waves. In addition, snails of different sizes and differentspecies did not show the same patterns although they were collectedfrom the same sites. Importantly, the shell shape of Liuorinaunifasciata varied significantly among sites at approximatelythe same height within a shore. These differences could notbe clearly correlated with density, mean size nor exposure towaves. The only consistent pattern was a decrease in relativeaperture size in specimens living higher on the shore. Modelsthat have commonly been proposed to explain shape and relativeweight of shells in other species of gastropods are not adequateto explain the small- and large-scale variation of the measurementsdescribed here. It is proposed that any selective advantageof shell morphology and the effects of any variables on thedevelopment of shell morphology in these species can only beidentified after appropriately designed and replicated fieldexperiments. (Received 4 March 1994; accepted 13 September 1994)