Photoreceptors of Bryozoan Larvae (Cheilostomata, Cellularioidea)

The ultrastructure of potential photoreceptors in larvae of Tricellaria occidentalis and four species of Bugula is described and compared with previously reported photoreceptors in larvae of Bugula neritina and Scrupocellaria bertholetti. A single sensory cell forms the functional unit of each photoreceptor. This cell is distinguished by a concentration of pigment vesicles in its apical part, a direct connection with the nervous system, and a large number of cilia that form the photoreceptoral organelle. These cilia have axonemes morphologically identical to those of motile cilia. The membranes of sensory cilia are unbeaded and qualitatively less osmophilic than those of the motile cilia of adjacent accessory and coronal cells. Three photoreceptor types are designated based on topological complexity: Type I, in which the sensory cell is flush with adjacent coronal cells and the photoreceptoral organelle is unprotected; Type II, in which the apical surface of the sensory cell is invaginated, forming a lumen containing the photoreceptoral organelle; and Type III, in which the sensory cell is at the base of an epidermal invagination and the photoreceptoral organelle is protected in a lumen formed by the sensory cell and accessory cells. There is a greater range of morphological variation among photoreceptors in larvae of Bugula spp. than between those of two species of the related genera Scrupocellaria and Tricellaria.     

Effect of malformin on the major constituents of Phaseolus vulgaris

Malformin inhibits wet and dry weight, nitrogen accumulation,and cell wall, RNA, DNA and protein synthesis in Phaseolus vulgaris.The relative proportion of dry matter and nitrogen in malformedtissues is increased in the ethanol soluble fraction and decreasedin the residue remaining after hydrolysis with 0.5 N HCl. Inhibitionof cell wall and protein synthesis was generally greater thaninhibition of nitrogen accumulation and RNA and DNA synthesis.The effects of malformin on the composition of P. vulgaris aresimilar to alterations in composition reported for ethylene,and opposite to those reported for gibberellic acid. ¹This research was supported by grant GB-7158 from the NationalScience Foundation and grant E-146-F from the American CancerSociety. ²Journal Paper No. 3509 of the Purdue Agricultural ExperimentStation. (Received October 23, 1968; )     

Perfect Order: Recognizing Complexity in Bali

Perfect Order: Recognizing Complexity in Bali . J. Stephen Lansing. Princeton: Princeton University Press, 2006. 225 pp.     

Late stage deferral of parturition in the viviparous lizard Niveoscincus ocellatus (Gray 1845): implications for offspring quality and survival

The ability of viviparous lizards to defer parturition after completion of embryonic development is a potentially key strategy for enhancing offspring fitness. Using the spotted snow skink, Niveoscincus ocellatus , we investigated the ability of females to defer birth if placed into cold conditions at the same time, for 1, 2 or 3 weeks at the end of gestation. The ability to defer birth was compared between two populations at each end of the species' altitudinal range. We hypothesized that females from the high elevation population would be less likely to defer parturition under extended periods of poor conditions, thus ensuring that young were not born too late in the season. In all but the 3-week treatment group from the high elevation population, females were able to defer birth when placed under cold conditions: for all groups, there was no treatment effect on offspring phenotype at birth, dispersal distance or survivorship after release. However, there was a significant negative effect of treatment on offspring growth measured after release, with the results differing between the populations. Females from the high elevation population were less able to defer birth under long periods (3 weeks) of cold conditions, and this was accompanied by a decrease in viability of the offspring.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 735–746.     

Heterozygosity and components of fitness in a strain of rainbow trout

We examined the relationship between multilocus heterozygosity and several components of fitness in the Arlee strain of rainbow trout (Salmo gairdneri) . There is a significant negative association between multilocus heterozygosity and standardized rate of oxygen consumption (VO₂) in 168 fish produced from a pooled mating between 55 females and 60 males. Fish which are more heterozygous also tend to be longer, heavier and have a significantly greater condition factor than fish which are less heterozygous. However, no relationship is evident between VO₂, weight, length, condition factor and multilocus heterozygosity within two full-sib families. These results indicate that the larger size of more heterozygous fish may partially be attributed to the increased metabolic efficiency in heterozygotes compared to homozygotes and that these differences may only be detectable at the population level. More heterozygous females of the same age also have larger eggs. Energy conversion may be more efficient in more heterozygous females resulting in the production of larger eggs. The prediction that fish with faster developmental rates are metabolically more efficient and, therefore, have lower VO₂ was also tested. Earlier hatching fish from five families do not have significantly lower VO₂ than their later hatching full-sibs.     

Biogeography of Puerto Rican ants: a non-equilibrium case?

Ants were studied on Puerto Rico and 44 islands surrounding Puerto Rico. Habitat diversity was the best predictor of the number of species per island and the distributions of species followed a nested subset pattern. The number of extinctions per island was low, approximately 1–2 extinctions per island in a period of 18 years, and the rates of colonization seem to be greater than the extinction rates. Ant dynamics on these islands do not seem to support the basic MacArthur and Wilson model of island biogeography. The MacArthur and Wilson equilibrium is based on the notion that species are interchangeable, but some extinctions and colonizations can change the composition and number of species drastically.