The effects of body size on mating and reproduction in Brachinus lateralis (Coleoptera: Carabidae)

Abstract. 1. The causes and reproductive consequences of body size variation of Brachinus lateralis Dejean, a parasitic carabid beetle, were investigated.
2. Body size variation occurs within and between sites. Host size has a major influence on body size of the adult.
3. Fecundity is positively correlated with body size. Egg size is not correlated with body size.
4. Mating males tend to be larger than non-mating males. There is a positive correlation of body sizes in mating pairs.
5. Limited opportunity for host choice may maintain size variation despite the advantages of large size.
6. The non-random patterns of mating for a species without obvious intrasexual aggression suggest that subtle means of male-male competition or female choice may be important.     

Formation of Basal Bodies in Ciliary Epithelium of Molluscs Buccinum undatum L. and Lymnaea stagnalis L.

Electron microscopic studies of the leg ciliary epithelium was carried out in two mollusks. In the epithelium of the leg of adult animals, the centrioles were mostly formed de novo with participation of deuterosomes during the formation of basal bodies. Transformation of the centriolar cylinder in a mature basal body is accompanied by the cylinder elongation and appearance of pericentriolar structures, such as rootlet system, basal legs, and basal plate. Centriolegenesis proceeds in both ciliate and nonciliate (with microvilli) cells of the epithelium. It has been proposed that the cell with microvilli represent a transitional stage in differentiation of the ciliary cells.     

Marine and estuarine gradients — An overview

The Proceedings of the ECSA 21 symposium on Marine and Estuarine Gradients are reviewed. It is emphasised that this is probably the first time that a full set of papers on the tidal freshwater sections of estuaries has appeared. There is however some ambiguity in the terminology applied to such waters, and a more consistent terminology is proposed. In particular the estuary is defined as reaching upstream as far as the tidal limit, irrespective of salinity. A wide variety of gradients within estuaries and coastal waters are considered, but it is apparent that the crucial spatial gradients are based on salinity, oxygen and turbidity, and that many other gradients are co-variables with these parameters. Temperature is also important for temporal gradients.     

Female and male Texas cichlids (Herichthys cyanoguttatum) do not fight by the same rules

Selection usually acts differently on males and females duringintrasexual competition for resources and/or mates. Nevertheless,agonistic behavior has been examined both theoretically andempirically mostly in males. Our research questions whethermales and females follow the same rules of engagement in intrasexualcontests as predicted by the sequential assessment model (SAM).The SAM predicts negative correlations between contest intensityand duration and the magnitude of asymmetry in resource holdingpower (RHP) between the contestants, such that the most escalatedcontests are those between similarly endowed individuals. Westaged male and female intrasexual contests with varying degreesof body size asymmetry under a round robin design using themonogamous Texas cichlid fish (Herichthys cyanoguttatum) asa study case. We used Mantel's matrix analysis to compare howthe behavioral content, duration, structure, and outcome ofmale and female contests were affected by the relative bodysize of the contestants. In the case of males, relative sizein each contest predicted outcome, duration, and frequency ofconventional and escalated behaviors according to prevailingtheory. Female contest structure and outcome, however, werenot predicted by the relative size of contestants. We discussour results in terms of other asymmetries that might be importantin structuring female contests, and we propose potential approachesto study female–female aggression.     

Seasonal growth of Atlantic cod: effects of temperature, feeding and reproduction

Growth of 2659 Atlantic cod Gadus morhua aged 4 to 9 years examined in Placentia Bay, Newfoundland, peaked in most cases in June and was at a minimum in October or November. Water temperature, partial fullness index ( I _P) and gonado‐somatic index ( I _G) explained between 31 and 52% of the monthly variability in growth. Temperature and I _P of capelin Mallotus villosus had significant effects on growth of all age groups and explained most of the variance for ages 6–8 and 4–5 years, respectively. The I _P of large invertebrates (ages 4 to 7 years), sandlance ( Ammodytes sp. age 6 years) and demersal fishes (age 9 years) had age‐specific effects in the model. Overall, amphipods, decapods and echinoderms dominated the Atlantic cod diet in most seasons, but fish consumption by Atlantic cod was high in June and July, particularly on capelin. The rapid increase in somatic mass during June and July occurred despite cold water temperatures ( < 3° C at 50 m) and moderate to high gonado‐somatic index. The findings of this study suggest that when food was not a limiting factor, growth tended to increase even when Atlantic cod occupied colder waters, but when food was limiting, the opposite may have occured.     

The effect of caffeine,different fixation regimes and low temperature on microtubules in the cells of higher plants

Caffeine, (1:3:7-tri-methyl-xanthine), either as a prefixation treatment or included with glutaralde-hyde as the primary fixative, destroys or disorganises the microtubules associated with the formation of secondary walls in fibres from the flowering stem of the grass Lolium temulentum L. There is no observable effect of caffeine treatment on the microtubules associated with primary wall formation in collenchyma and young fibres from L. temulentum or in root cap cells of Zea mays L. and Phaseolus vulgaris L. The microtubules associated with primary wall formation are destroyed by cold treatment but not those associated with secondary wall formation. Tannic acid included in the fixative shows the microtubules associated with secondary wall formation in fibres of L. temulentum to be composed of 13 subunits. Treatment with lanthanum hydroxide does not stain the core or the halo of the microtubules.Abbreviation PIPES Piperazine N-N- bis 2 ethanol sulphonic acid The Grassland Research Institute is financed through the Agricultural Research Council     

Toe pad morphology and mechanisms of sticking in frogs

Sticking ability in frogs was measured on a series of different substrates. Analysis of performance suggests that frogs use two sticking mechanisms: interlocking on rough surfaces and capillarity on smooth surfaces. There is a correlation between morphological specializations of the toe pad and sticking ability, but these morphological features are not unique to arboreal species. Terrestrial species that use leaves as resting sites during times of inactivity have many of the same morphological specializations and stick as well as the strictly arboreal species.     

Maternal induction of larval diapause and its sensitive stage in the blow fly Lucilia sericata (Meigen) (Diptera: Calliphoridae)

Lucilia sericata has a facultative diapause in the third larval instar after cessation of feeding. Induction of the diapause is influenced by the photoperiod and temperature conditions experienced by insects in the parental generation as well as those experienced by the larvae themselves. The sensitive stage of the parental generation for induction of diapause was examined using diapause‐averting conditions of 16 h light : 8 h darkness (LD 16:8) at 25°C and diapause‐inducing conditions of LD 12:12 at 20°C. The incidence of diapause in the progeny was predominantly determined by the conditions experienced by the parents in the adult stage. Moreover, the results of reciprocal crosses showed that only the mother's experience is involved in the induction of diapause in the progeny.