The Response of Contractile and Non-Contractile Vacuoles of Paramecium calkinsi to Widely Varying Salinities

ABSTRACT. Paramecium calkinsi from tidal marshes survive a wide salinity range. Fluid output of contractile vacuoles of these cells decreased as salinity of the medium to which they were acclimated increased, and both pulse rate and vacuole volume were used to regulate output. When cells were first exposed to more dilute medium, contractile vacuoles greatly increased volume so that fluid output increased even though pulse rate decreased. In cells shifted to a more concentrated medium, contractile vacuole output decreased by decreasing pulse rate. The contractile vacuole is surrounded by a set of collecting structures which change form as the salinity changes. Distensible ampullae are found in media of low salinity and collecting canals are found in media of high salinity. When cells are shifted from high salinity to low, the number of ampullae increases and the number of canals decreases. When cells are shifted from low salinity to high, the number of ampullae decreases and the number of canals decreases. Other non-contracting vacuoles also appear in response to a hypoosmotic shock. These include vacuoles within the cell as well as "blisters" on the surface. The number and frequency of blisters increases with the size of the hypoosmotic shock. They detach from cells without resulting in any visible loss of cytoplasm. Non-contractile vacuoles may play a role in sequestering and removing excess water that the contractile vacuoles cannot handle.     

Genetic structuring in the freshwater mussel Anodonta corresponds with major hydrologic basins in the western United States

Freshwater mussels (unionids) are increasingly recognized as important providers of ecosystem services, yet are among the most endangered fauna in the world. Because unionids are generally sessile and require specific fish hosts for development and dispersal, they are particularly vulnerable to habitat degradation. Surprisingly, little is known about the distribution of genetic diversity in freshwater mussels and this gap has a negative impact on taxonomy, monitoring, conservation and ecological research in these species. Here, we focus on western North American Anodonta, one of only three genera known to exist in this broad landscape and which contains three highly divergent lineages. We describe phylogeographical subdivision in the most widespread and diverse of these lineages, which includes Anodonta californiensis and Anodonta nuttalliana and occurs from Canada to Mexico. Using mitochondrial and nuclear data, we found that genetic structuring within this clade is inconsistent with morphologically based species designations, but instead follows patterns of vicariance among major hydrogeologic basins. Furthermore, there was a strong tendency for population diversity within drainage systems to increase downstream, implying greater habitat or host fish availability in this direction. Microsatellite results indicated that sampling locations were all genetically distinct, even at short distances. Many of our sample populations showed evidence of a recent demographic bottleneck, although this effect seemed to be very local and not drainage or basin‐specific. This study provides a foundation for the establishment of appropriate management units and future research on adaptive differentiation and host fish relationships.     

Differences in inhibitory capability among queens of the ant Solenopsis invicta

ABSTRACT. The abilities of various categories of queens of the fire ant, Solenopsis invicta Buren, to inhibit de-alation by virgin queens are compared by means of a standardized bioassay that detects the presence of an inhibitory pheromone. Highly fecund (high weight) queens of monogynous colonies and virgin replacement queens in queenless colonies have a significantly greater inhibitory capability than queens of lower fecundity (lower weight). In polygynous colonies, inhibitory effectiveness is also positively related to the fertility of individual queens, although no pheromone can be detected in queens that lay few eggs. Alate virgin queens that have overwintered in the parental nest, and sexually mature spring-reared virgin queens, either do not produce the pheromone, or produce too little to be detected. These results are discussed in relation to the degree of ovarian development of different queen categories and in relation to the social status of these queens.     

Predicting development, metabolism and secondary production for the invertebrate predator Bythotrephes

1. Rates of embryonic and post-embryonic development for Bythotrephes cederstroemi from Lakes Erie, Huron and Michigan are represented almost equally well by three empirical models across water temperatures ranging from about 12–22 °C, but at lower temperatures two of the competing models fail and an exponential development rate model proves most robust.
2. Clutch masses of parthenogenic females can greatly exceed the tissue mass of the mother. Clutch size is strongly correlated with the mass of reproductive adults, accounting for over 90% of the variation among individuals. Hence, the mass gain from neonate to reproductive adult can be estimated directly from clutch size.
3. Tissue stoichiometries, respiration quotients and stoichiometries of C and N metabolism were determined experimentally, extending the predictions of existing respiration and growth models.
4. A predictive model for growth and production by the invertebrate predator has advantages over previous model formulations owing to our expanded calibration data base. The model is presented in a modular design that is easily upgraded as additional calibration data become available.     

Digestive Efficiency Mediated by Serum Calcium Predicts Bone Mineral Density in the Common Marmoset (Callithrix jacchus)

Two health problems have plagued captive common marmoset (Callithrix jacchus) colonies for nearly as long as those colonies have existed: marmoset wasting syndrome and metabolic bone disease. While marmoset wasting syndrome is explicitly linked to nutrient malabsorption, we propose metabolic bone disease is also linked to nutrient malabsorption, although indirectly. If animals experience negative nutrient balance chronically, critical nutrients may be taken from mineral stores such as the skeleton, thus leaving those stores depleted. We indirectly tested this prediction through an initial investigation of digestive efficiency, as measured by apparent energy digestibility, and serum parameters known to play a part in metabolic bone mineral density of captive common marmoset monkeys. In our initial study on 12 clinically healthy animals, we found a wide range of digestive efficiencies, and subjects with lower digestive efficiency had lower serum vitamin D despite having higher food intakes. A second experiment on 23 subjects including several with suspected bone disease was undertaken to measure digestive and serum parameters, with the addition of a measure of bone mineral density by dual‐energy X‐ray absorptiometry (DEXA). Bone mineral density was positively associated with apparent digestibility of energy, vitamin D, and serum calcium. Further, digestive efficiency was found to predict bone mineral density when mediated by serum calcium. These data indicate that a poor ability to digest and absorb nutrients leads to calcium and vitamin D insufficiency. Vitamin D absorption may be particularly critical for indoor‐housed animals, as opposed to animals in a more natural setting, because vitamin D that would otherwise be synthesized via exposure to sunlight must be absorbed from their diet. If malabsorption persists, metabolic bone disease is a possible consequence in common marmosets. These findings support our hypothesis that both wasting syndrome and metabolic bone disease in captive common marmosets are consequences of inefficient nutrient absorption. Am. J. Primatol. 75:153‐160, 2013. © 2012 Wiley Periodicals, Inc.     

Herbivory in Crabs: Adaptations and Ecological Considerations

Plant material is the major source of nutrition for many speciesof crabs in both marine and terrestrial habitats. Physical andchemical characteristics of plants can lead to difficultiesin harvesting and ingestion, to low digestability, unpalatabilityand toxicity, and to deficiencies in specific nutrients, especiallynitrogen, vitamins and fatty acids. We describe the range ofherbivory in crabs, as well as the anatomical, physiologicaland behavioral adaptations that enhance nutrient acquisitionfrom plant material. We assess the impact of herbivory by crabson plant communities, and highlight topics for further research.     

Sex Chromatin Frequency in the Avian Aminon

Conflicting results have been reported on the incidence of sexchromatin in avian cells. In this study the sex chromatin frequenciesare explored in the ammotic cells from two .Leghorn varietiesof domestic fowl, a species which is reported to possess anheterochromatic and late leplicating W sex chromosome. The incidenceof sex chromatin was also examined in the ammotic epitheliumof the Japanese quail throughout the incubation period. Thisspecies of quail possesses a W sex chromosome that is euchromaticat metaphase When the sex chromatin frequencies in the domestic fowl werecompared with the gonadal sex of the embryos, a nuclear sexualdimorphism was apparent with the high frequencies correspondingto embryos of the female sex. No such nuclear sexual dimorphismwas found in the quail, both male and female embryos had approximatelythe same incidence of sex chromatin in their ammotic cells These findings are interpreted in support of the idea that thecytological entity identified as sex chiomatin in the domesticfowl represents the W sex chromosome in the interphase nucleus