Sperm Nuclear Transformation and Aster Formation Related to Metabolic Behaviour in Amphibian Eggs

Bufo arenarum oocyte maturation is related to important modifications in the metabolism of carbohydrates. Such changes involve a different relative participation of the main oxidative routes and are under the influence of seasonal variations of the pituitary activity.
Ovulated coelomic oocytes obtained during the winter period, were unable to initiate cleavage after injection of a sperm suspension. The extent of sperm head transformation and aster formation in the cytoplasm of oocytes with a different metabolic behaviour (obtained during the winter and summer periods) were studied.
Our results show that sperm nuclear transformation and DNA synthesis were quite similar in both types of oocytes. In contrast to summer oocytes, in which the pronucleus was sourranded by an aster, no aster structure was formed in winter ooctyes notwithstanding pronucleus formation occurred.
These results suggest that the failure to develop aster may explain the lack of cleaving in winter oocytes. It appears that the metabolic changes, aster formation and the capability to cleave are closely related and could be dissociated from oocyte nuclear maturation in this species.     

Fine structure of Lasaea subviridis and Mysella tumida sperm (Bivalvia,Galeommatacea)

Summary Lasaea subviridis and Mysella tumida sperm resemble the primitive spermatozoan type, but exhibit several unique morphological features. L. subviridis sperm heads vary in shape and size owing to differing degrees of nuclear condensation. A fully mature, heterogenous acrosomal vesicle with an associated axial rod is present. Up to 50% of L. subviridis sperm in developing gonads have conspicuously angled flagella that propel the sperm cells in irregular helical paths. This may represent a penultimate stage in sperm development because the remainder of the sperm cells have posteriorly-directed flagella and swim in a nonhelical anterior direction. A trend toward a reduction in both nuclear condensation and swimming ability may be a long-term consequence of increasing degrees of localized, but non-internal self-fertilization in marine invertebrates that brood. Mysella tumida sperm are monomorphic and possess numerous microvilli (30–60 nm in diameter and up to 5.7 m in length) that resemble stereocilia and radiate from the cell membrane surrounding the basal body. In this species, the sperm cell does not have an axial rod, and the complex acrosomal vesicle contains five distinct zones of varying electron opacity. One of these zones is a transverse, electron-opaque band that is apparently composed of rolled-up membrane. Following acrosomal breakdown, this membrane unfolds to cover the anterior tip of the sperm cell. Although both L. subviridis and M. tumida are hermaphroditic, the relative size of their male investments is conspicuously different. Approximately 40–50% of the M. tumida gonadal volume is testis compared with about 5% of that in L. subviridis.     

Correlation between spermathecal morphology and mating systems in spiders

This study tested predictions regarding male mating preferences which were based on some aspects of female reproductive morphology which may influence sperm precedence patterns in six species of spiders. Males of two species, whose 'conduit' spermathecal design has been associated in previous studies with first male sperm precedence, showed the predicted preference for associating with immature females about to moult to maturity rather than mature females. Those of a third species, however, associated indiscriminately with mature and penultimate instar females. As predicted, males of three other species with 'cul-de-sac' spermathecal morphology did not associate preferentially with immature females. Immature females were avoided in two of the species, but not in the third. One of the species with cul-de-sac spermathecae showed, as predicted, lack of a strong first male advantage in sperm precedence. These data give only limited confirmation of the predictions.     

Food preference of freshwater invertebrates: comparing fresh and decomposed angiosperm and a filamentous alga

1. Fresh and decomposed Mougeotia sp. (a filamentous green alga) and Elodea nuttallii (a vascular plant) were offered as food to three species of aquatic macroinvertebrates (Lymnaea peregra, Asellus meridianus and Endochironomus albipennis) to test: (i) if filamentous algae are preferred to aquatic higher plants (hereafter, called ‘macrophytes’) and (ii), as is known for higher plants, if decomposition also results in greater palatability of filamentous algae. 2. Compared with the alga, the macrophyte in both states was of higher nutritional value. Conditioning improved the nutritional value of both food types, but especially of the macrophyte. 3. Both fresh alga and fresh macrophyte were eaten little by all animals except A. meridianus feeding upon the macrophyte. Consumption was higher for both plants in their decomposed state. However, L. peregra consumed more decomposed macrophyte than the decomposed alga. Both decomposed plants were eaten most by E. albipennis followed by A. meridianus and L. peregra. 4. Digestibility of both plants, but especially of the macrophyte, increased significantly after decomposition. The assimilation efficiencies of all animals on the fresh E. nuttallii were higher than on fresh Mougeotia sp. After decomposition, the efficiency increased significantly only on the alga. Consequently, both decomposed plants were assimilated with similar efficiency by all test animals. 5. Amongst aquatic macrophytes, the increase of their consumption and digestibility upon decomposition has hitherto been known only for vascular plants but not for filamentous algae.     

Aspects of hadrosaurian cranial anatomy

Supraorbital bones in Saurolophus angustirostris are described, and their presence in all hadrosaurs is suggested. Frontal-nasal and premaxillar-nasal fontanellae are distinguished in hadrosaurs; their presence is explained as connected with growth and considered to he responsible for the variability of crest structures. New data indicating the presence of a cartilaginous diverticulum nasi within the circumnarial depression in Saurobphus ongustirostris are presented. A physiological (respiratory and/or thermoregulatory) function of the nasal diverticulum is proposed.     

Territorial damselflies do not show immunological priming in the wild

Adaptive immunity allows vertebrates to gain protection against repeated pathogenic infections. Analogous responses (priming) have been recently uncovered in invertebrates. However, whether such responses are widespread is not known. The present study investigated the presence of immunological priming in males of a species whose phylogenetic position places it in one of the less derived insect orders. It is hypothesized that the efficiency of such a response could be related to animal condition, as assessed by the expression of a sexually selected ornament. Hetaerina americana Fabricius (Odonata: Calopterygidae) males bear a conspicuous ornament (a red wing spot), which is evolutionarily maintained via male territorial competition. Using field‐collected animals, a group of males is challenged with bacteria before exposure to a higher dose of the same or a different bacteria, and survival is compared with that of infected males not previously challenged, as well as control groups. Gram‐positive and Gram‐negative bacteria are used. To explore how long priming may take to work, the second exposure is carried out either after 1 or 5 days. Red spot and body size are entered in the analysis as predictors of survival within and between groups. There is no difference in survival among groups, which suggests no priming effect. Overall, red spot and body size are not consistent in explaining survival.     

Environmental drivers of the bryophyte propagule bank and its comparison with forest-floor assemblage in Central European temperate mixed forests

Species richness, composition and abundance of the bryophyte diaspore bank of Central European temperate mixed forests were compared with the forest-floor bryophyte assemblage. The impact of environmental variables and anthropogenic disturbances, including tree species composition, stand structure, microclimate, light conditions, soil and litter properties, management history, and landscape properties, potentially influencing bryophyte diaspore bank assemblages were explored. Thirty-four, 70–100 years old mixed stands with differing tree species composition were examined in the ?rség National Park, Western Hungary. The diaspore bank was studied by soil collection and cultivation, and data were analysed by multivariate methods. Contrary to the forest-floor bryophyte assemblage, where substrate availability, tree species composition and stand structure were the most influential environmental variables, the composition and abundance of the diaspore bank was mainly affected by site conditions (microclimate, litter and soil properties). Species richness of the bryophyte diaspore bank was lower than that of the forest-floor bryophyte assemblage. Short-lived mosses (colonists, short-lived shuttles) were dominant in the diaspore bank, as opposed to the forest-floor bryophyte community, where perennial mosses dominated. In the studied forests, the importance of the bryophyte diaspore bank was relatively low in the regeneration and maintenance of the forest-floor bryophyte vegetation.     

Phlebotominae of epidemiological importance in cutaneous leishmaniasis in northwestern Argentina: risk maps and ecological niche models

In Argentina, 58.2% out of the 8126 Cutaneous Leishmaniasis (CL) incident cases accumulated from 1954 to 2006 were reported in the provinces of Salta and Jujuy. The aim of this study was to develop an exploratory risk map and a potential distribution map of the vector, in order to offer recommendations for CL prevention. A total of 12 079 Phlebotominae (Diptera: Psychodidae) belonging to the species Lutzomyia neivai (Pinto), Lu. migonei (França), Lu. cortelezzii (Brèthes), Lu. shannoni (Dyar), Lu. quinquefer (Dyar) and Brumptomyia spp. (França & Parrot) were captured. Potential distribution models were created for two species, Lu. neivai (incriminated vector of Leishmania braziliensis) and Lu. migonei, associated with domestic animals in Argentina and that in turn could be involved as a link between zoonotic transmission cycles and anthropozoonotic. The Maximum Entropy Modeling System (MaxEnt) was used. The Jackknife test was performed, and the ‘rainfall of the driest month’ was the variable that best generalized the models. Accuracy was evaluated by the area under the curve (AUC) and validated by the Cohen's kappa index. This approximation provides a new analytical resource of high potential for the prevention of the disease, in order to allocate resources properly and to develop the most suitable strategies for action.