MACROEVOLUTIONARY PATTERNS OF MORPHOLOGICAL DIVERSIFICATION AMONG PARASITIC FLATWORMS (PLATYHELMINTHES: CERCOMERIA)

Patterns of parasite morphological diversification were investigated using a morphological data base for the parasitic platyhelminths comprising 1,459 characters analyzed using phylogenetic systematic methods. Only 10.8% of the 1,882 character transformations are losses, casting doubt on views that parasites are secondarily simplified and exhibit degenerate evolution. Chi-squared analysis indicates that character loss in the Digenea and Monogenea occurs in proportion to total change and is disproportionately lower within the Eucestoda. In the Digenea fewer female characters and more male characters have been lost than expected by the total number of characters in that group, and more male and more nonreproductive characters have been lost in proportion to their distribution across groups. In the Monogenea fewer nonreproductive and more larval characters have been lost than expected within the group, and female character loss is high relative to other groups. In the Eucestoda fewer female and more larval characters have been lost than expected within the group, whereas loss of male and nonreproductive character is low, and loss of larval characters is high, compared to the other groups. Patterns of character loss result partially from characters that show repeated (homoplasious) loss in different groups. High consistency index and low homoplasy slope ratio values indicate that the parasitic platyhelminths show unusually low levels of homoplasy, casting doubt on views that parasite morphology is unusually adaptively plastic. Homoplasy within the monogeneans occurs in proportion to overall character change, is slightly higher than expected in the digeneans, and is much lower than expected within the eucestodes. Homoplasy occurs less often than expected in larval characters, and more often than expected in nonreproductive characters in the Digenea. Monogeneans show more homoplasy than expected for larval characters both within and among groups. Eucestodes show fewer homoplasious male and nonreproductive, and more homoplasious larval, characters than expected within the group, and higher homoplasy in larval characters and lower homoplasy in female and nonreproductive characters among groups.     

Sociobiology and the Comparative Approach: One Way to Study Ourselves

This paper is based on my lecture in a macroevolution course I team-teach with Profs. Daniel Brooks and David Evans at the University of Toronto. The lecture has undergone many revisions over the years as I grappled with problems discussing certain areas (e.g., rape as an adaptive strategy, gender “roles”). Eventually, I realized that the problem areas said more about my personal conflicts than they did about the science. This was one of those epiphany moments, a time when I recognized that I was less likely to accept hypotheses that contradicted the way I wanted the world to be and more likely to uncritically accept hypotheses that confirmed my world view. That epiphany, in turn, led me to realize that science is never separate from the personal biases/demons of its practitioners, especially when we are asking questions about the evolution of human behavior. That realization was not novel within the vast literature of sociology and philosophy. But it was novel for me. I was aware of discussions about personal biases clouding scientific interpretation; I just didn’t think it applied to me (I absorbed the philosophical discussions without making the connection to “my world”). So, on the heels of that epiphany, the following is a very personal take on the question of teaching sociobiology, based on where my journey, aided by my experience as an ethologist and phylogeneticist and colored by my own history, has taken me.     

Enhanced reactivation of UV-irradiated adenovirus 2 in HeLa cells treated with non-mutagenic chemical agents

Treatment of HeLa cells with ethanol and sodium arsenite, compounds which are known to elicit the heat-shock response, before infection with UV-irradiated adenovirus 2 has been found to result in the enhanced reactivation of the damaged virus in a manner similar to that obtained by pre-irradiation or heating of the cells. Enhanced reactivation may be the result of the inhibition of DNA synthesis caused by these agents since hydroxyurea also produced a significant enhancement.     

An open-loop model for investigating mammalian thermosensitivity

We have developed, and herein describe, a simple, open-loop model in the rat, in which both skin and hypothalamic temperatures can be modified and clamped. A water-perfused thermode was positioned in the abdomen to drive hypothalamic temperature, and a water-perfused jacket was used to clamp skin temperature. These permitted the independent control of hypothalamic and skin temperatures. The former could be altered between 35 and 41 °C whilst achieving an isothermal skin temperature clamp. Similarly, skin temperature could be modified between 22 and 42 °C whilst hypothalamic temperature was clamped. Maximal hypothalamic heating and cooling rates were: 0.75 and −2.04 °C h⁻¹ 100 g⁻¹. We are currently using this animal model to investigate how central thermosensitivity is affected via manipulations of hypothalamic cooling rates.     

High summer temperatures are associated with poorer performance of underyearling Atlantic salmon (Salmo salar) in upland streams

Future warming scenarios are predicted to result in an increased frequency of high, and potentially stressful, temperatures in aquatic ecosystems. Here we examined whether the performance of wild underyearling Atlantic salmon (Salmo salar) in Scottish streams stocked with identical egg densities was influenced by thermal stress. Biomass and density declined with degree hours exceeding 23°C, indicating apparent mortality or emigration as a possible result of exposure to high temperatures. These results strengthen the need for further action such as riparian tree planting to reduce stream summer temperatures.     

The bed nucleus of the stria terminalis has developmental and adult forms in mice,with the male bias in the developmental form being dependent on testicular AMH

Canonically, the sexual dimorphism in the brain develops perinatally, with adult sexuality emerging due to the activating effects of pubescent sexual hormones. This concept does not readily explain why children have a gender identity and exhibit sex-stereotypic behaviours. These phenomena could be explained if some aspects of the sexual brain networks have childhood forms, which are transformed at puberty to generate adult sexuality. The bed nucleus of stria terminalis (BNST) is a dimorphic nucleus that is sex-reversed in transsexuals but not homosexuals. We report here that the principal nucleus of the BNST (BNSTp) of mice has developmental and adult forms that are differentially regulated. In 20-day-old prepubescent mice, the male bias in the principal nucleus of the BNST (BNSTp) was moderate (360 ± 6 vs 288 ± 12 calbindin^+ ve neurons, p < 0.0001), and absent in mice that lacked a gonadal hormone, AMH. After 20 days, the number of BNSTp neurons increased in the male mice by 25% (p < 0.0001) and decreased in female mice by 15% (p = 0.0012), independent of AMH. Adult male AMH-deficient mice had a normal preference for sniffing female pheromones (soiled bedding), but exhibited a relative disinterest in both male and female pheromones. This suggests that male mice require AMH to undergo normal social development. The reported observations provide a rationale for examining AMH levels in children with gender identity disorders and disorders of socialization that involve a male bias.