Social stimulation,nuptial colouration,androgens and immunocompetence in a sexual dimorphic cichlid fish

The nature of the costs maintaining honesty of sexual signalling in inter- and intrasexual interactions remains a contentious issue. For carotenoid-based colour ornaments, it has been hypothesized that the honesty of the signal is enforced when carotenoid allocation to colour expression is traded off against carotenoid availability for immunocompetence. In addition, honesty is enforced if androgens required for colour expression are immunosuppressive. We tested whether there is a trade-off between colour expression and immunocompetence in a lek-breeding haplochromine cichlid fish, Pundamilia nyererei, from Lake Victoria with a carotenoid-based nuptial dress. First, we showed that expression of red nuptial colouration and social rank in a group were positively correlated. We then successfully manipulated the level of colour advertisement by socially stimulating individually housed males with a rival male: Stimulated males developed larger areas of red nuptial colouration and had higher levels of circulating 11-ketotestosterone (11-KT) than non-stimulated males. We subsequently tested the humoral immune response to a novel antigen (sheep red blood cells). There was no overall significant effect of social stimulation on antibody production, but in the stimulated males, the degree of red colouration and the antibody response were negatively correlated. This significant interaction between colour and treatment thus shows that the negative correlation between colouration and antibody production is dependent on the (manipulated) social environment. This study provides correlational and experimental evidence for a trade-off between expression of a sexual trait and one component of immune function in fish. We found no evidence for a direct effect of 11-KT on antibody production, and we discuss alternative mechanisms that could mediate the trade-off.     

Temporal patterns in the vibratory courtship signals of the wandering spider Cupiennius salei Keys.

Summary The vibratory courtship signal generated by abdominal and leg movements of male Cupiennius salei on plants consists of impulses, which in groups of about ten form syllables. A syllable together with the preceding silent pause is called a sequence. Up to 50 sequences chained together form a series. A series together with the preceding silent period is called an interseries. A complete courtship is built up from a row of successive interseries. An additional signal produced by palpal drumming only occurs between syllables. Females respond to ca. 40% of the male signal series with a single irregular signal produced by leg oscillations and lasting for 113–1790 ms. Their response reduces the duration of the male interseries significantly from an average of 27.9 s to 20.6 s. The female signal follows a male signal series within a narrow time frame of 0.89±0.53 s. Analysis over long periods of time and of complete courtships showed the male signalling to be highly structured in the time domain and to contain many cues potentially usable by the female for both such precise timing and conspecific recognition: (1) On average, the interval between the last two syllables is significantly longer than the preceding ones. (2) During the course of a series, syllable durations increase nearly linearly from 93 ms to 123 ms. (3) The twelfth sequence (T-12) prior to the final one (T) is outstanding since here, roughly 4 s before the end of a series, the duration of sequences and pauses, the signal amplitudes and the occurrence of palpal drumming abruptly start to increase. Also, the frequencies contained in the syllables shift to higher values. (4) Between sequences T-4 and T-6 pause duration and sequence duration reach their minimum whereas the values for signal acceleration and the occurrence of palpal drumming are highest.     

Multistate models for monitoring individual trees in permanent observation plots

This interdisciplinary research on forest ecosystems begins with some characteristics of ecosystems which are the basis for the derivation of statistical models for the development and vitality of trees. Several ecological problems which could be solved by longitudinal studies are mentioned. Statistical methods for the evaluation of the crowns of spruce trees (Picea abies Karst) in three permanent observation plots in Switzerland are described. In particular, the time-dependent proportional odds model and a transitional model are used. Through application of these multistate models the data give information on the dependence of an ordered categorical response variable on covariates characterizing the ecosystem. The response variable is observed through infrared aerial photographs. This monitoring system gives insight into the dynamic behaviour of the forest ecosystem. The need for more eco-systematically motivated statistical research using longitudinal studies is identified.     

Ökotoxikologische Risikoanalyse der Cadmium-Belastung

Cadmium contamination in the agricultural soil of the region Leipzig-Halle was determined at 63 sites covering an area of ca. 7 000 km². Normalization according to lutum and organic matter lead to effective exposure values; their distribution was compared with NOEC data taken from literature. The risk analysis reveals that the soil fauna is potentially affected by cadmium contamination at 9% of the investigated sites.     

Ökologische Situation der Region Leipzig-Halle

The deposition of heavy metals bound to air dust and their ecological effects depend, to a large degree, on particle size, which influences the transport processes in the environment. To estimate the size range of the particles mainly taken up by the pine needles, concentration gradients along a sector leeward of Leipzig were modelled according toGauss plume calculations. The results show that the aerodynamic size is between 1 and 10 μm. Particles of this size range can be taken up by lungs and, thus, have a particular toxicological relevance.     

Optimal growth and maximal survival temperatures of Atlantic Laminaria species (Phaeophyta) in culture

The effects of temperature on growth rate of rapidly-growing cultured macrosporophytes of 9 isolates of Atlantic Laminaria comprising 4 species have been investigated. No significant population variation was observed within species despite wide variations in temperature between the original collecting sites. L. saccharina showed a broad temperature optimum in the 10°–15°C range, whereas L. longicruris had a sharp optimum at 10°C. L. digitata and L. hyperborea grew more slowly, with only slightly sub-optimal growth over a wide temperature range, but with peaks at 10°C (L. digitata) and 15°C (L. hyperborea). The maximum survival temperatures of individual male and female vegetatively-growing gametophytes were ascertained for these species plus the Arctic L. solidungula, and were as follows: L. saccharina and L. longicruris, 23°C; L. digitata (male), 23°C; L. digitata (female), 22°C; L. hyperborea, 21°C; L. solidungula, 18°C. The lack of within-species differences demonstrates that the success of the genus in areas with different temperature regimes is brought about by phenotypic plasticity of individuals rather than the selection of temperature races or ecotypes.     

Reproduction,growth and photosynthesis of gametophytes of Laminaria saccharina grown in blue and red light

The induction of reproductive activity by blue light in female gametophytes of the brown alga Lamnaria saccharina has been investigated and related to other effects of red and blue light on these plants. Although germination of zoo-spores is slightly delayed in red light, female gametophytes grow at similar rates in blue and red light of the same quantum irradiance up to an age of 8 to 10 days, when plants in blue light begin to form eggs. The percentage of plants forming eggs is proportional to the total quanta of blue wavelengths received up to a saturating value of about 400 μE·cm^-2; a 50% response is induced by 200 μE·cm^-2. The action spectrum for the induction of fertility has a main peak at 430 to 450 nm, with two subsidiary peaks in the blue and one in the near-ultraviolet light, but the action spectrum for photosynthesis is quite different, with peaks in the red, green and blue regions. These results indicate that egg formation in female gametophytes occurs as a specific morphogenetic response to blue light, which is independent of photosynthesis and growth, and trial experiments with male gametophytes of L. saccharina and gametophytes of other species of Laminariales indicate that these plants react similarly.     

Invertebrates of the upper chamber,Gatún Locks,Panama Canal,with emphasis on Trochospongilla leidii (Porifera)

Observations were made on the horizontal distribution of certain invertebrates on the walls and floor of the upper chamber of the Gatún Lock system of the Panama Canal. The hydroid Cordylophora caspia (Pallas) and the gastrophod Neritina usnea Röding extended the full length of the chamber; the oligochaete Marionina sp. was confined to the upper half of the chamber (adjacent to Gatún Lake), and the amphipod Gitanopsis tortugae? Shoemaker, the isopod Munna sp. and the bivalve Mytilopsis sallei (Recluz) to the lower half; the sponge Trochospongilla leidii (Bowerbank) was distributed from the upper end to near the lower end of the chamber. A peculiar wedge-shaped distribution of T. leidii is thought to be a response to the influence of slight increases in salinity. Morphological observations on T. leidii are presented.     

The biology of colonial hydroids. II. The morphology and ultrastructure of the medusa of Eirene viridula (Thecata-Leptomedusa: Campanulinidae)

The free-swimming medusae of Eirene viridula are typical marine hydroids, with distinct subdivisions into body regions, which were studied by comparison of light and electron microscopy. Particular attention is given to the epithelio-muscular and digestive muscle cells. The epidermis — apart from a few nerve cells and cnidocytes-consists of epitheliomuscular cells. At their bases these cells form a musculature and at the apex many secretory vesicles. In the velum, large expansions of the intercellular space are found. The gastrodermis — apart from the mucous and zymogen cells in the manubrium — consists of digestive muscle cells, the structure of which corresponds in principle to that of the epitheliomuscular cells. In its apex, this type of cells contains both normal coated vesicles and discoidal coated vesicles. In the solid tentacles, the digestive muscle cells form a turgescent vesicular tissue. The central nervous system consists of the exumbrellar, subumbrellar, and gastrodermal nerve rings. They are composed of ganglion cells, their processes, and intraepithelial flagella. The static organs are purely ectodermal statocysts which have only one lithocyte and only one sensory cell.