Dual function of allopreening in the cooperatively breeding green woodhoopoe, Phoeniculus purpureus

Allopreening is a widespread but little-studied phenomenon in birds and is particularly prevalent in species where individuals are forced into close proximity. Such a situation facilitates the transfer of ectoparasites between individuals and allopreening has therefore been proposed to serve a hygienic function. In addition, allopreening might theoretically play a role in social communication. Green woodhoopoes (Phoeniculus purpureus) are cooperatively breeding birds that roost communally every night in a tree cavity and are thus susceptible to high ectoparasite loads. Our results suggest that allopreening of the head and neck (“head”), which cannot be efficiently self-preened, serves a primarily hygienic function: all individuals, irrespective of sex, dominance status, and group size, donated and received similar rates of head allopreening and terminated a similar proportion of bouts in which they were involved. Furthermore, there was a high occurrence of reciprocation and head allopreening occurred at a constant rate throughout the year. In contrast, allopreening of the rest of the body, which is accessible to the recipient itself, is likely to serve a primarily social function: body allopreening rates were higher in larger groups; dominant individuals received more body allopreening and terminated a significantly higher proportion of bouts than subordinates; and subordinates donated body allopreening at a higher rate than dominants. Moreover, bouts initiated by dominants were more likely to be reciprocated than those initiated by subordinates and body allopreening rates varied seasonally. Allopreening in the green woodhoopoe is therefore likely to serve a dual function, depending on the part of the body involved.     

Sperm motility and longevity in the giant cuttlefish, Sepia apama (Mollusca: Cephalopoda)

The sperm kinetics and fertilisation literature in marine invertebrates is heavily biased toward free-spawning species. Nonetheless, many species (e.g. cephalopods) transfer and/or fertilise gametes in confined external spaces or internally, creating very different selective pressures on sperm storage, sperm longevity and hence sperm competition. Here we report the results of an investigation into the effects of sperm age, water temperature and sperm concentration on sperm motility in the giant cuttlefish (Sepia apama). Significant positive correlations were found between percent motility and sperm concentration, and between sperm motile speed and sperm concentration. Mean percent motility of cuttlefish sperm suspension was still 9% eight hours after being released from the spermatophore and diluted into filtered seawater at 12°C (ambient field temperature during the spawning season). Sperm resuspended from spermatangia taken from (mated) females in the field were motile for up to 100 hours. When spermatophores were stored at 4°C motility was still observed in resuspended sperm after two months. Our results show that spermatangia and spermatophores can retain and release live sperm for long periods. The observed longevity of sperm in S. apama greatly increases the potential for sperm competition in this species.     

Survival and lifetime reproductive success in dispersing and resident red squirrels

Dispersal in red squirrels (Sciurus vulgaris) is not sex-biased and strict philopatry is rare. The immigration pattern suggests that nearly all animals have to disperse away from the natal site and that dispersal in this species is the outcome of local (intrasexual) competition. If this interpretation is correct, we predict that dispersers and residents, of both sexes, should have equal survival rates and lifetime reproductive success. Body mass, longevity, reproductive success and dominance rank of 34 resident offspring (settling within 400 m of the natal range) and 70 immigrants (dispersers) were compared. Immigrants did not weigh less than residents as adults, nor did they have a higher mortality during the pre-setding period. Survival rate, lifetime reproductive success (females) and the proportion of males obtaining a high dominance rank were similar for residents and dispersers, and no sex effect was found on either of the parameters studied. These results are consistent with the hypothesis that local competition determines whether an individual disperses further away or settles close to its birthplace.     

Phenotypic plasticity in a mutualistic association between the sponge Haliclona caerulea and the calcareous macroalga Jania adherens induced by transplanting experiments. I: morphological responses of the sponge

The mutualistic association between the sponge Haliclona caerulea and the calcareous red macroalga Jania adherens is conspicuous on shallow rocky regions of Mazatlán Bay (eastern tropical Pacific, Mexico). Transplanting experiments were carried out to examine the morphological responses of the association to an environmental depth gradient. Simultaneously, we conducted caging experiments to examine the effects of predation (mainly by angelfishes) on association morphology. For this, we transplanted specimens of the association from a control area at 3 m depth to depths of 1 and 5 m, and measured the morphological responses in the association (macro- and microstructure) from the three sites before and after 103 days. The association had the capacity to adjust both macro and micromorphologically, and both external morphology and body structure changed significantly with depth. The specimens grown at 1 m developed a larger surface area of attachment, higher organic density and higher inorganic content than the control specimens at 3 m, and the organisms grown at 5 m depth. We also detected significant differences in the aquiferous system of the sponge, which developed smaller and more numerous oscula at 1 m than at 5 m depth. These differences seem to be consistent with the wave movement as one of the main regulatory factors of the morphology of the association. However, the spicules from H. caerulea were most slender in shallow water, which is not consistent with increasing robustness in the face of greater wave force. The algal skeleton supplied up to 27% of the total inorganic structure of the association; thus, algal contribution significantly reduces the energy costs of spicule production, specifically under high wave exposure, when H. caerulea requires structural reinforcement relative to organic content. The contribution of the sponge to the association (as ratio Si to CaCO₃) increased significantly from 3 to 5 m (12% in the uncaged specimens and 22% in the caged specimens), showing that the mutualistic relationship decreases with depth. The production of sponge branches in caged individuals was the most notable difference from uncaged morphs, which could suggest the effect of predators like angelfishes. However, branches could also be a response to the reduction in water movement and irradiance inside the cages. Sponges are known to show morphological acclimation in response to habitat variation, but this is the first study to show it in a sponge living in association with a macroalga.     

Chemistry of preen gland secretions of passerines: different pathways to same goal? why?

Summary. Passeriformes is the largest order of birds and includes one third of the bird species of the world, living in very diverse habitats. We investigated the chemistry of preen gland secretions of some groups of passerines from temperate regions found in diverse microhabitats. Some of the common components were mixtures of homologous monoesters made up of long chain acids and alcohols. Individual species had characteristic distribution of esters and was unique to a given species, although there were some individual variations. We compared the composition of acids and alcohols that formed same molecular weight esters in different species and we found that the combination of acids and alcohols to arrive at same molecular compositions varied distinctly between species. To compare compositions of over all acids and alcohols that formed the esters, the representative samples of secretions from the individual species were transesterfied the produce methyl esters and alcohols. We found that there were distinct differences in number of acids and alcohols that produced the combination of homologous mixtures of esters. Also they differed both qualitatively and quantitatively. There were also seasonal differences in the secretion components. Thus though the intact mixtures of esters in individual species had some similarities, they were very complex mixtures and differed characteristically for individual species. Here we discuss possible causes for evolution of these variations. We suggest that the evolution in variation of preen gland secretion is probably due to selective pressures caused by ectosymbionts such as feather-mites and feather-chewing lice that live on feathers and probably feed on the secretions and surrounding environments     

Variations in the birth sex ratio and neonatal mortality in a natural herd of horses

Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many cases have been linked to resource availability. Most of these biases in offspring sex ratios concern polygynous species with pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies, such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality rates in nutritionally poor years than in good ones, whereas “year quality” had no effect on the mortality of female offspring; year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth interval between their two subsequent offspring. Received: 28 December 1996 / Accepted after revision: 27 July 1997     

Aggregation pheromone in Hypogastrura viatica (Collembola)

Summary An animal of the collembolan Hypogastrura viatica isolated on a substrate previously contaminated by individuals of the same species behaves as if it were part of an aggregate. The basic activity decreases by an amount equal to the constant of aggregation. This decrease is due to the response to a stimulus caused by a substance that is discharged onto the substrate by aggregating organisms. This substance seems to be an aggregation pheromone.     

Interpopulational differences in chemical composition and chemosensory recognition of femoral gland secretions of male lizards Podarcis hispanica: implications for sexual isolation in a species complex

Summary. Molecular studies suggest that the Iberian wall lizard, Podarcis hispanica, forms a species complex with several monophyletic types. In Central Spain two of these types are spatially not isolated and may interact. Sex pheromones are important for species recognition and, thus, differences between lizards’ types in chemicals used in intraspecific communication could lead to reproductive isolation. Analyses by GC-MS showed that the femoral gland secretions of adult males of different types were different. Males of one type had twelve exclusive compounds, and proportions of some shared compounds differed. This presumably would reflect selection for the persistency and efficiency of chemical signals in different environments; less volatile compounds and with a higher chemical stability being favoured in the type of lizards inhabiting more humid climatic conditions. Differential tongue-flick rates to scents from femoral secretions indicated that males were able to detect and discriminate between males of different types based on chemical cues alone. In contrast, females detected but did not seem able to discriminate between scents of the two types of males. Thus, multiple factors might be simultaneously acting either against or in favor of speciation, leading, on the one hand, to genetic differences between types, but, on the other hand, probably precluding an effective reproductive isolation in areas where both types of lizards may interact.     

When to come out from your own shell: risk-sensitive hiding decisions in terrapins

Animals should optimize the decision of when to come out from a refuge after a predators unsuccessful attack because hiding may be costly. Many prey run to hide in refuges in their habitat, whereas others are sessile and take refuge in a protective structure surrounding their body. An intermediate situation is when animals, such as turtles, have morphological structures that provide some partial protection, but they are also able to escape actively to safer refuges. This might complicate hiding decisions predicted by the theory of optimal-refuge use. We studied antipredatory tactics of Spanish terrapins (Mauremys leprosa) in response to simulated predatory attacks with different characteristics (i.e. combinations of several risk factors) and under different conditions (i.e. proximity to safe refuges), which should contribute to overall risk-level estimation. We specifically examined how risk level affected time spent withdrawn into the shell and time until turtles switched to an active escape tactic. The results showed that turtles were able to adjust their hiding behavior by assessing the risk of emerging before the predator had left the area. However, increasing hiding time may also increase the risk that the predator was able to injure or kill the turtle. Thus, the possibility of switching the antipredatory tactic to an alternative active escape to safer refuges (i.e. water) also influenced hiding times.Communicated by P. Bednekoff     

Organic compounds and trace metals of anthropogenic origin in sediments from Montego Bay,Jamaica: assessment of sources and distribution pathways

Surface sediments throughout Montego Bay, Jamaica were collected in 1995 and analyzed for their trace metal and trace organic contaminant content. A variety of trace metals, petroleum hydrocarbons, polycyclic aromatic hydrocarbons, coprostanol as well as chlorinated hydrocarbons such as pesticides and polychlorinated biphenyls were detected and provide evidence for several anthropogenic inputs to the bay. Two main sources of these chemicals are the Montego River and the North Gully, the latter being more significant. Particle-associated pollutants were found to be distributed along the Montego River plume, as well as being transported by the prevailing water currents to the South-Western sections of the bay, probably through re-suspension of enriched fine sediments from the North Gully outfall area.