Survival of Tick-Borne Encephalitis Virus in Goat Cheese and Milk

Food and Environmental Virology - Survival of tick-borne encephalitis virus was studied from pasteurized and unpasteurized goat milk and from salted/unsalted and spiced/unspiced cheese made from...     

Responses of female lizards,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>, to males' chemical cues reflect their mating preference for older males

Female mate choice based on visual traits appears to be rare in lizards. Field observations suggest that females of the lizard Lacerta monticola preferred to mate with larger/older males. Although older males are usually green and larger, and younger males brown and smaller, there is some overlap in size and coloration between age classes. Thus, visual cues may not always be reliable indicators of a male's age. We hypothesized that female mate-choice preferences may be based on males' pheromones, which might transmit information about characteristics such as age. In a laboratory experiment, we analyzed the effect of age of males on attractiveness of their scents to females. When we offered scents of two males of different age, females associated preferentially with scents of older males. This suggested that females were able to assess the age of males by chemical signals alone, and that females preferred to be in areas scent-marked by older males. Thus, females may increase their opportunities to mate with males of high quality, or may avoid harassment by sneaking young males. This result agreed with field observations on females mating with old males, and rejection of advances by young males. Our results also suggested that female preference for older males may depend on their own body size. Large females showed a strong preference for older males, whereas smaller females were not so selective. This, together with males' preference for large females, might lead to size-assortative matings. We suggest that the quality and/or quantity of male pheromones could communicate to the female heritable male genetic quality (i.e. age) and thereby serve as the basis of adaptive female choice in lizards.Communicated by W.E. Cooper     

Banding pattern of mussel (Mytilus galloprovincialis) chromosomes induced by 2 × SSC/Giemsa-stain treatment

Mytilus galloprovincialis were collected from an intertidal population in NW Spain in 1988, and chromosomes from the gill tissue of 37 individuals were studied. The present paper describes the banding pattern of aM. galloprovincialis population which enabled us to identify all pairs of chromosomes. Banding was induced by means of a 2 × SSC (0.3M sodium chloride:0.03M sodium citrate)/Giemsa-staining technique, and a diagrammatic representation was constructed based on mean number of bands. The application of this banding technique may prove useful in future research related to the cytogenetics and cytotaxonomy of mussels and other molluscs.     

Proliferation kinetics of mussel (Mytilus galloprovincialis) gill cells

A technique of sister chromatid differentiation (SCD) using bromodeoxyuridine (BrdU) incorporation and a modification of the fluorescence plus Giemsa (FPG) method was employed to determine cell-proliferation kinetics in gill tissue of the mussel Mytilus galloprovincialis. Dose-dependent proliferation inhibition was examined. In vivo administration of BrdU for 12, 24, 36, 48, 60, 72, 84, and 96 h was studied. Our data show that the highest yield of second-generation metaphase plates is obtained after 60 h BrdU treatment; the duration of a cell cycle is 24 to 30 h. On the basis of these data, a BrdU incorporation period of 48 to 60 h would seem to be most appropriate for the sister chromatid exchange (SCE) tests carried out in gill cells of M. galloprovincialis, whereas the 12 to 24 h exposure would give the best results for replication band analysis.     

Chemosensory cues allow male lizards<Emphasis Type="Italic"> Psammodromus algirus</Emphasis> to override visual concealment of sexual identity by satellite males

Males of many species of lizards show conspicuous breeding colors but, in some species, young competitively inferior males conceal their sexual identity by a female-like dull coloration that allows them to evade aggression from dominant males and to adopt an alternative satellite-sneaking mating tactic. However, large males of the lizard Psammodromus algirus reacted aggressively to young intruder males despite their female-like coloration, suggesting that they might have the ability to recognize competitor males by chemosensory cues. We experimentally manipulated the head coloration (brown vs orange) and scents (male vs female) of small young males. For staged agonistic encounters, we compared the response of resident unmanipulated large males to the different manipulated small males. When we manipulated only the color of small males, the response of resident large males was independent of the paint manipulation; brown and orange males elicited a similar aggressive response. However, when we also manipulated the scent, small males painted orange or brown, but bearing the scent of males, received a significantly higher number of aggressive responses than small males painted orange or brown, but bearing the scent of females. The results showed that, at close range, the reaction of large males to manipulated individuals was dependent on the scent, whereas color seemed to be less important. Coloration may be, however, more important in long-distance communication as shown by the outcome of the first encounters. Also, orange coloration may increase the intensity of the aggressive response. Effective sex recognition by territorial large males is important in natural situations to avoid sneak matings by young male competitors. Thus, even if small males visually conceal their sexual identity, chemosensory cues allow large males to identify them at close range.     

Studies on the defensive behaviour ofHypselodoris species (Gastropoda: Nudibranchia): Ultrastructure and chemical analysis of mantle dermal formations (MDFs)

The mantle dermal formations (MDFs) ofHypselodoris webbi (D'orbigny, 1839), andH. cantabrica (Bouchet and Ortea, 1980) are globular sub-epidermal structures located in the cephalic and caudal regions. Histologically they consist of an accumulation of vacuolate cells surrounded by a basal lamina and an outer muscular capsule. Chemical analysis ofH. webbi MDFs reveals the presence of high concentrations of longifolin, a well known deterrent furanosesquiterpenoid that had been previously isolated from this species. In the present paper it is demonstrated that the great majority of longifolin accumulated in the mantle ofH. webbi is stored in the MDF vacuolar cells. This finding strongly suggests that such structures act as chemical weapons against predation, mainly protecting vital organs such as the head, rhinophores and gills.     

Testosterone stress does not increase asymmetry of a hormonally mediated sexual ornament in a lizard

The theory that fluctuating asymmetry is sensitive to both environmental and genetic stress is gaining acceptance among evolutionary biologists. Most empirical work has focused on ornamental traits on the assumption that they are more susceptible to stress. In tegumentary coloration is a common ornament in nature, and frequently has a hormonal basis. Earlier studies in the lizard Psammodromus algirus indicate that testosterone induces the development of head nuptial coloration in large males and, at the same time, produces an increase of the ectoparasite load and higher mortality. Hence, the manipulation of testosterone levels may be a way to increase ornament expression and simultaneously create conditions that may make symmetrical development difficult. This positive covariation between character size and symmetry is opposite to that expected in theory for sexually selected traits, so the predicted elevation of asymmetry due to the treatment cannot be confounded by any intrinsic association between symmetry and character size. We firstly consider the effect that testosterone supplementation has on two variables that reflect the symmetry of bilateral throat nuptial coloration in large P. algirus males. Also, we examine whether ornament symmetry is positively associated with reproductive success, a prediction of theory of sexually selected symmetry. Testosterone treatment did not increase the fluctuating asymmetry of throat coloration. Size asymmetry increased with character size in individuals with a fragmented colour pattern, but changed suddenly to a highly symmetric pattern in individuals with non-fragmented coloration. Mirror asymmetry decreased steadily with character size. These results suggest that the development of coloration on both sides of the throat midline follows a random pattern. Asymmetry did not correlate with variables that estimated reproductive success, suggesting that asymmetry is not affected by physiological stress and that this trait is not a sexually selected signal in P. algirus. Received: 1 July 1996 / Accepted after revision: 4 May 1997     

Case selection by a limnephilid caddisfly [Potamophylax latipennis (Curtis)] in response to different predators

Some organisms use morphological structures obtained by behavioural processes to lower mortality by predation. We test whether larvae of the limnephilid caddisfly Potamophylax latipennis (Curtis) vary their responses to the presence of different predators (dragonfly naiads, fire salamander larvae or brown trout) by choosing organic or mineral cases. We offered both case types to larvae, and simulated differences in predation risk using water conditioned with chemicals from the different predators. Our results show that Potamophylax larvae detect and discriminate predators using water-borne chemical cues and alter their choice of case type according to the perceived predation risk. Moreover, the distribution of larvae bearing cases of different anti-predator value matches the spatial variation in predation risk in the field.     

Patterns of chemical defences in plants: an analysis of the vascular flora of Chile

Summary. The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs, shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and stress hypotheses are sustained.