Paleoecology of Sphenothallus on an Upper Ordovician hardground

A hardground from the Upper Ordovician Dillsboro Formation near Dillsboro, Indiana, U.S.A., preserves an assemblage of encrusting and boring fossils on both top and bottom surfaces. The slab is inferred to have been an undercut ledge, and the dominant fossils of the assemblage, holdfasts of the tube-building worm Sphenothallus and trepostome bryozoans, are prevalent on both sides. The clumping of Sphenothallus holdfasts has been statistically demonstrated using a nearest-neighbor technique. Sphenothallus has also been shown to withstand overgrowth in interactions with bryozoans.     

Evolutionary transitions in symbioses: dramatic reductions in bathymetric and geographic ranges of Zoanthidea coincide with loss of symbioses with invertebrates

Two fundamental symbiosis‐based trophic types are recognized among Zoanthidea (Cnidaria, Anthozoa): fixed carbon is either obtained directly from zooxanthellae photosymbionts or from environmental sources through feeding with the assistance of host‐invertebrate behaviour and structure. Each trophic type is characteristic of the suborders of Zoanthidea and is associated with substantial distributional asymmetries: suborder Macrocnemina are symbionts of invertebrates and have global geographic and bathymetric distributions and suborder Brachycnemina are hosts of endosymbiotic zooxanthellae and are restricted to tropical photic zones. While exposure to solar radiation could explain the bathymetric asymmetry it does not explain the geographic asymmetry, nor is it clear why evolutionary transitions to the zooxanthellae‐free state have apparently occurred within Macrocnemina but not within Brachycnemina. To better understand the transitions between symbiosis‐based trophic types of Zoanthidea, a concatenated data set of nuclear and mitochondrial nucleotide sequences were used to test hypotheses of monophyly for groups defined by morphology and symbiosis, and to reconstruct the evolutionary transitions of morphological and symbiotic characters. The results indicate that the morphological characters that define Macrocnemina are plesiomorphic and the characters that define its subordinate taxa are homoplasious. Symbioses with invertebrates have ancient and recent transitions with a general pattern of stability in host associations through evolutionary time. The reduction in distribution of Zoanthidea is independent of the evolution of zooxanthellae symbiosis and consistent with hypotheses of the benefits of invertebrate symbioses, indicating that the ability to persist in most habitats may have been lost with the termination of symbioses with invertebrates.     

Sporulation of Marteilioides branchialis N. Sp. (Paramyxea) in the Sydney Rock Oyster, Saccostrea commercialis: An Electron Microscope Study

ABSTRACT The ultrastructure of sporulation of a new parasite, Marteilioides branchialis (Paramyxea), in the Sydney Rock oyster, Saccostrea commercialis , is described. The development is typical of other Paramyxea whereby a stem cell internally cleaves a secondary cell contained within a vacuole. It differs from other species in the phylum in that each secondary cell produces a single spore composed of two concentric cells, one within a vacuole of the other. This type of sporulation represents the simplest of all known Paramyxea. Infection results in focal gill lesions and was observed concurrently with an epizootic of another paramyxean, Marteilia sydneyi .     

Biophysical Ecology and Heat Exchange in Insects

When used with observations of behavior and physiology of animalsin known microclimates, a biophysical approach is a powerfultool for predicting body temperatures of insects. For ectothermicinsects, solution of the energy budget equation and use of operativetemperature models have been used to determine the range oftemperatures which an insect can exhibit in a given environment.Knowledge of body temperature has allowed predictions of whenimportant behaviors arepossible in the field, thereby directlyrelating biophysical models to fitness parameters of animals.A proper understanding of the physiological mechanism(s) controllingheat exchange is prerequisite to application and interpretationof information obtained using biophysical techniques. For endothermicinsects, physiological regulation of heat exchange forces amore complicated analysis. Evaluation of thoracic heat exchangealone (aside from indicating whether insects are regulatingT_th) is of little utility for either quantifying total heatexchange, or evaluating thermoregulatory mechanisms withoutfurther information. Further studies of biophysics and physiologyof endothermic insects during flight are needed to correct thesedeficiencies. Application of biophysical techniques has allowedpredictions of behavior of flying insects based onprinciplesof heat exchange which cannot be examined directly. Analysesof endothermy of restinghoneybee swarms and hives indicate thatthese "superorganisms" regulate temperature rather preciselyover a remarkable range of environmental temperature using mechanismsequivalent to thoseused by resting endothermic vertebrates.     

The Spread of Infection by the Microsporidan,Nosema disstriae,in Insect Cell Lines1

Nosema disstriae, a parasite of the forest tent caterpillar, Malacosoma disstria, was cultured with cell lines UMN-MDH-1 (Malacosoma disstria), IPLB-1075 (Heliothis zea), and BTC-32 (Triatoma infestans). Infected cultured cells were used to infect the healthy cell lines. Electron micrographs of thin sections of 6-day-old cultures revealed infected cells that exocytosed vesicles containing vegetative and immature sporulating forms of the parasite. Some of these forms were believed to be responsible for intercellular transmission of the parasite. The spread of infection was augmented by culturing the cells at high densities; if the density was too low, there was little or no cross infection. Cross infection was inhibited, but not blocked completely, by high osmolality of the culture medium. The yield of spores from a confluent cell monolayer at the end of growth was generally 1–4 × 10⁷ per ml of culture medium.     

Articulated Knowledges: Environmental Forms after Universality's Demise

Critiques of universalism require rethinking when confronted with environmental political arenas, in which the very concepts of "universality" and "particularity" are in a constant process of self-conscious deployment. In this article, I attend to the analytic and political implications of such deployments in a recent incinerator controversy in Hong Kong. I suggest that an aesthetic of local appropriateness and its formal requirement of simultaneous universal and particular truth value normalize the politics of environmental expertise such that the only legible form for counterknowledge is one of articulated knowledges. To understand how the knowledges emergent in an NGO–village collaboration were scaled, linked, and mobilized, I analyze a translation of expert knowledge and the event's metapragmatic effects. A subsequent account of unarticulated knowledges emphasizes the political-economic conditions that limit whose knowledges can count as particular in articulations of counterexpertise.     

Long-term exposure of Boeckellagibbosa (Copepoda, Calanoida) to in situ levels of solar UVB radiation

1. The freshwater calanoid copepod Boeckella gibbosa is typical of high elevation lakes and ponds in Patagonia (Argentina). Previous studies have shown that this species is highly tolerant to short-term exposure to natural and artificial UVB radiation, and that its tolerance is due to photoreactivation by longer wavelength radiation. In this study, we investigate the potential sublethal effects of solar radiation after prolonged exposure.
2. We incubated B. gibbosa at 1 m depth in oligotrophic Lake Toncek for 24 days. The incubation chambers were 1.2 l acrylic cylinders covered with appropriate filters in order to obtain three radiation treatments: visible radiation only, visible radiation + UVA and visible radiation + UVA + UVB.
3. The three treatments did not differ significantly in variables considered as indicators of survival (number of individuals), reproduction (proportion of ovigerous females, clutch size) and development (instar composition). Although resistance to solar UVB radiation is certainly a requisite to live in transparent high elevation habitats, the fact of being effectively exposed to natural levels of UVB radiation does not seem to have measurable consequences on an already adapted species, such as B. gibbosa