Effects of temperature on success of (self and non-self) fertilization and embryogenesis in Diploria strigosa (Cnidaria, Scleractinia)

The effects of seawater temperature on the degree of success of self-fertilization versus cross-fertilization and on embryogenesis were investigated in the scleractinian coral Diploria strigosa (Dana 1846). Gametes from nine colonies were collected from the Flower Garden Banks reefs, a set of coral reefs in the northern Gulf of Mexico, ~110 nm offshore from Texas, United States. Gametes from the coral colonies were combined in all possible combinations and placed in 30°, 31°, and 32°C water baths on successive nights, respectively. Each cross, whether selfed or out-crossed, and each temperature treatment, was replicated twice. A high frequency of successful self- and cross-fertilization was observed at all temperature treatments and in both blocks. Higher temperatures, however, commonly produced numerous developmental aberrations during embryogenesis of the larvae. Thus, although fertilization rates can remain high under high temperature conditions, if temperatures remain high for several days, embryonic development and larval viability may be expected to decrease dramatically. We propose that the success of coral larval development may be diminished in areas where abnormally high sea surface temperatures occur during the spawning season. We also propose that highly successful selfing may enhance the abundance of locally adapted genotypes, which in turn may be advantageous where reefs, such as the Flower Garden Banks, are relatively geographically isolated.     

A protein signal triggers sexual reproduction in Brachionus plicatilis (Rotifera)

The defining feature of the life cycle in monogonont rotifers such as Brachionus plicatilis (Muller) is alternation of asexual and sexual reproduction (mixis). Why sex is maintained in such life cycles is an important unsolved evolutionary question and one especially amenable to experimental analysis. Mixis is induced by a chemical signal produced by the rotifers which accumulates to threshold levels at high population densities. The chemical features of this signal were characterized using size exclusion, enzymatic degradation, protease protection assays, selective binding to anion ion exchange and C3 reversed phase HPLC columns, and the sequence of 17 N-terminal amino acids. These studies were carried out over two years beginning in 2003 using B. plicatilis Russian strain. When rotifer-conditioned medium was treated with proteinase K, its mixis-inducing ability was reduced by 70%. Proteinase K was added to medium auto-conditioned by 1 female ml⁻¹ where typically 17% of daughters became mictic and mixis was reduced to 1%. A cocktail of protease inhibitors added to conditioned medium significantly reduced degradation of the mixis signal by natural proteases. Conditioned medium subjected to ultrafiltration retained mixis-inducing activity in the >10 kDa fraction, but the <10 kDa fraction had no significant activity. The putative mixis signal bound to an anion exchange column, eluting off at 0.72 M NaCl. These fractions were further separated on a C3 reversed phase HPLC column and mixis-inducing activity was associated with a 39 kDa protein. Seventeen amino acids from the N-terminus have strong similarity to a steroidogenesis-inducing protein isolated from human ovarian follicular fluid. The 39 kDa protein is an excellent candidate for the rotifer mixis induction signal.     

Effect of temperature,salinity and food level on sexual and asexual reproduction in Brachionus plicatilis (Rotifera)

The reproductive response of sexual and asexual female Brachionus plicatilis (Muller) was examined over temperatures ranging from 20° to 40°C, salinities from 5 to 40 S, and food levels from 0.25 to 20 g Chlorella vulgaris dry-weight per ml. Reduced food levels, as well as temperature and salinity extremes, reduced reproduction of both sexual and asexual females, but did so differentially. Reproduction by sexual females was reduced to a greater extent at environmental extremes than asexual females. The broad, flat reproductive response curve of asexual females extended beyond the limits of the narrower, more sharply peaked curve of sexual females. Thus zones of exclusively asexual reproduction exist at environmental extremes where sexual reproduction is physiologically restricted. These results are corroborated by a comparison of the lifetime fecundity of individual sexual and asexual females over a 20°C temperature range. No differences in lifetime fecundity occurred between sexual and asexual females at 18° and 28°C. At 38°C, however, asexual female fecundity reached its highest level, while sexual female fecundity declined 15%. The appearance of sexual females in rotifer populations in the result of both inducible and repressible factors.     

Lessons from Developing Methods to Study the Relationship of Energy and Water Savings to Housing Conditions and Resident Health

Energy- and water-saving have been promoted as ways of saving money while there has been controversy about the effects (if any) of such measures on resident health. In public housing in the US, energy saving has taken the form of Energy Savings Performance Contracts (ESPC) that pay for renovations out of future savings. In an attempt to test feasibility and pilot research methods we conducted a study of the relationship between gas and water use, exterior heat sensor locations, and basement ventilation with indices developed from resident-reported living conditions and health symptoms in a single housing development. The data sources that we had available to us were not ideal. In particular, we were unable to obtain water use data that coincided in time with our health survey data. Also, we did not have enough surveys in buildings with high water or gas use and had to pool those buildings with other buildings for analysis. Nevertheless, we found several associations between our measures of energy use and resident reports of health symptoms. The associations that we found were generally in the direction that energy and water savings were associated with fewer symptoms and fewer environmental problems. There is a need for studies that obtain better input data but that generally follow the approach we developed.     

Lessons from Developing Methods to Study the Relationship of Energy and Water Savings to Housing Conditions and Resident Health

Abstract

Energy- and water-saving have been promoted as ways of saving money while there has been controversy about the effects (if any) of such measures on resident health. In public housing in the US, energy saving has taken the form of Energy Savings Performance Contracts (ESPC) that pay for renovations out of future savings. In an attempt to test feasibility and pilot research methods we conducted a study of the relationship between gas and water use, exterior heat sensor locations, and basement ventilation with indices developed from resident-reported living conditions and health symptoms in a single housing development. The data sources that we had available to us were not ideal. In particular, we were unable to obtain water use data that coincided in time with our health survey data. Also, we did not have enough surveys in buildings with high water or gas use and had to pool those buildings with other buildings for analysis. Nevertheless, we found several associations between our measures of energy use and resident reports of health symptoms. The associations that we found were generally in the direction that energy and water savings were associated with fewer symptoms and fewer environmental problems. There is a need for studies that obtain better input data but that generally follow the approach we developed.     

Full life-cycle toxicity assessment using rotifer resting egg production: implications for ecological risk assessment

The majority of standardized toxicity tests incorporate only a fraction of the test organism's life-cycle. However, in natural ecosystems, organisms may be exposed at various times during their life-cycle or throughout their life-cycle. Thus, ecotoxicological data from standardized toxicity tests is of limited ecological relevance. Existing standardized toxicity tests using the freshwater rotifer Brachionus calyciflorus utilize 24-h survival or 48-h asexual reproduction as endpoints, despite evidence that sexual reproduction is more sensitive. A 96-h B. calyciflorus resting egg toxicity test was developed and used to estimate the toxicity of pentachlorophenol (PCP) and copper. Results were compared to a variety of acute and sublethal endpoints for both toxicants. The B. calyciflorus 96-h resting egg production NOEC for PCP of 10 micrograms/l was 20 times lower than the 48-h asexual reproduction no observed effect concentration (NOEC) and 120 times lower than the 24-h acute lethal concentration 50%. The 96-h resting egg production NOEC for copper of 2.8 micrograms/l was 7 times lower than the 48-h asexual reproduction NOEC and nine times lower than the 24-h acute LC50. Resting egg production was a more sensitive indicator of toxicity than several other sublethal endpoints as well. These results indicate that partial life-cycle toxicity tests are not sufficiently sensitive to detect ecologically relevant adverse effects.     

A rapid,simple screening toxicity test using desiccated bdelloid rotifers: Rotifer Activity Inhibition Test (RAIT)

Environmental Science and Pollution Research - A protocol for an ultra-rapid screening toxicity test is described using the rotifer Philodina acuticornis/roseola. The test can be executed in 30 min...     

Importance of climate uncertainty for projections of forest ecosystem services

Regional Environmental Change - Mountain forests provide a wide range of ecosystem services (ES, e.g., timber production, protection from natural hazards, maintaining biodiversity) and are...