Skate Bathyraja spp. egg predation in the eastern Bering Sea

Predation on skate eggs by snails was examined for three skate species at seven nursery sites in three regions (north, middle and south) of the eastern Bering Sea. Mean predation levels were 6·46% for the Alaska skate Bathyraja parmifera , 2·65% for the Aleutian skate Bathyraja aleutica and 22·25% for the Bering skate Bathyraja interrupta . Predation levels were significantly higher at the middle and north sites than the south sites for all species combined. Predation levels decreased with increasing egg-case densities at all nursery sites, and the highest predation levels occurred where egg-case densities were very low. Predated egg-case density increased with increasing snail densities across all nursery sites examined. The Oregon triton Fusitriton oregonensis was the most abundant snail species at all nursery sites and displayed ability to drill holes in the egg case of B. parmifera. Holes left by predatory snails in egg cases of B. parmifera were significantly larger, and of different shape at the middle site compared to the south site. Holes in B. parmifera were also significantly larger than those in egg cases of B. interrupta across all sites examined. Egg cases of B. aleutica possess surface spines that cover the egg case and may inhibit predation by snails at a greater rate than that of the B. parmifera and B. interrupta , which have a smoother egg-case surface.     

Über die Entwicklung der Eikapselvolumina bei verschiedenen Opisthobranchier-Arten (Mollusca,Gastropoda)

An attempt has been made to estimate the volumes of eggs and egg-capsules employing the formula for the rotation-ellipsoid, first after oviposition, second for the capsules during different stages of embryonic development until hatching. The results of the calculations permitted analysis of: (a) the relationship between egg-case volume and egg volume immediately after oviposition; (b) the size of capsules during development until hatching; (c) the relationship of the capsule volume at hatching in comparison to that after oviposition (enlargement-factor).Placida dendritica shows no increase in capsule volume during development.Gonidoris nodosa, Rostanga rufescens, Trinchesia viridis, Acanthadoris pilosa, Archidoris pseudoargus, Tritonia hombergi andAeolidia papillosa show a distinct increase in capsule volume at the time of velarcilia appearance. The degree of egg-case enlargement and the time of its beginning reveal interspecific differences; within some of the species, both also depend on the number of larvae present in the egg-case. The reasons for such behaviour are not yet known; some possible explanations are discussed.     

Embryo developmental events and the egg case of the Aleutian skate Bathyraja aleutica (Gilbert) and the Alaska skate Bathyraja parmifera (Bean)

Embryo development events were correlated with egg-case changes for the Aleutian skate Bathyraja aleutica and the Alaska skate Bathyraja parmifera . Yolk absorption underwent two phases: that of steady absorption during early development and that of rapid yolk absorption during the final development stages. Total length ( L _T) for 50% of the pre-hatching embryos egg-case jelly disappearance was 92·04 mm (range 81–102 mm) and 99·36 mm (range 81–100 mm) for B. aleutica and B. parmifera , respectively, allowing the inner chamber to open to seawater flow. The tail filament underwent three phases of growth: rapid elongation during early development (<100 mm embryo L _T), stasis of tail filament length during the remainder of embryo development and rapid absorption soon after hatching. Complete tail filament development coincided with the disappearance of egg-case jelly. Clasper buds first developed at embryos >70 mm L _T for both species and the sex ratio was 1:1 well before hatching. Egg cases that were devoid of an ova or developing embryo were c. 5·0 and 6·5% of the egg cases examined for B. aleutica and B. parmifera , respectively. Measurements showed that egg cases containing only egg jelly were smaller in both width and length than those possessing an ova. Embryo stages were punctuated with distinct events that correlated with egg case changes controlling the internal environment of the developing embryo.     

Egg-case diversity among dogfish, Scyliorhinus canicula (L.): a study of egg laying rate and nidamental gland secretory activity

Egg-case size, shape and pigmentation are distinctive features of each female lesser-spotted dogfish, Scyliorhinus canicula. During 9 months captivity under constant conditions (water, temperature, photoperiod, food), a laying sequence reminiscent of an annual cycle was observed in three females. While oocyte size and (with exceptions) egg-case weight remained constant, there was a marked decrease of the'albumen'jelly secreted by the anterior halves of nidamental glands.     

Egg-jelly production and composition in an oviparous chondrichthyan,Scyliorhinus canicula (Linnaeus, 1758)

Embryos of oviparous chondrichthyans develop within a structurally complex tertiary egg envelope known as the egg-case, which is provisioned with a secondary egg coat known as the egg-jelly. Whereas the former has been studied in detail, relatively little attention has been paid to the latter. This study examined the production and composition of egg-jelly in the small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758) and determined that it is a mucin hydrogel. The role of the egg-jelly appears to be one of simple, physical support for the developing embryo, as it was not found to possess bactericidal properties, nor did its constituents suggest a nutritive role.     

Brownie,a Gene Involved in Building Complex Respiratory Devices in Insect Eggshells

Background

Insect eggshells must combine protection for the yolk and embryo with provisions for respiration and for the entry of sperm, which are ensured by aeropyles and micropyles, respectively. Insects which oviposit the eggs in an egg-case have a double problem of respiration as gas exchange then involves two barriers. An example of this situation is found in the cockroach Blattella germanica, where the aeropyle and the micropyle are combined in a complex structure called the sponge-like body. The sponge-like body has been well described morphologically, but nothing is known about how it is built up.

Methodology/Principal Findings

In a library designed to find genes expressed during late chorion formation in B. germanica, we isolated the novel sequence Bg30009 (now called Brownie), which was outstanding due to its high copy number. In the present work, we show that Brownie is expressed in the follicle cells localized in the anterior pole of the oocyte in late choriogenesis. RNA interference (RNAi) of Brownie impaired correct formation of the sponge-like body and, as a result, the egg-case was also ill-formed and the eggs were not viable.

Conclusions/Significance

Results indicate that the novel gene Brownie plays a pivotal role in building up the sponge-like body. Brownie is the first reported gene involved in the construction of complex eggshell respiratory structures.     

The reproductive biology of Scyliorhinus canicula in the Bristol Channel, U.K.

Among 972 Scyliorhinus canicula , the overall sex ratio (males:females) was 1:1·23. Males matured between 490 and 540 mm L _T with 50% maturity at 520 mm. Females matured between 520 and 640 mm L _T with 50% maturity at 550 mm. Female gonadosomatic index peaked in May. Fecundity increased with fish length. The egg laying season lasted 10 months with a peak in June and July. The importance of erect, sessile invertebrates such as bryozoans, poriferans and hydroids as egg-case deposition sites has been established. Recently hatched fish were born in an equal sex ratio and at a mean length of 100·5 mm and mean weight of 3·07 g. One intersexual fish is described.     

秦巴拟小鲵在河南的发现及地理分布探讨

报道了采自河南省内乡县的一种小鲵科标本,经形态学鉴定以及DNA序列比对,确定为秦巴拟小鲵(Pseudohynobius tsinpaensis)。内乡是该物种已知分布区的东限,与已知分布点相差3个经度,呈间断分布。秦巴拟小鲵在内乡的发现可为探讨小鲵科动物的起源和演化提供重要的动物地理学依据。     

Placentation and associated aspects of gestation in the bonnethead shark, Sphyrna tiburo

The left ovary of the bonnethead shark, Sphyrna tiburo, is rudimentary, and the right ovary supplies both oviducts which share a common ostium situated in the falciform ligament. Preceding ovulation the nidamental gland of each oviduct hypertrophies and the caudal two-thirds of each oviduct is modified to form a uterus. In the Florida-Caribbean area Sphyrna tiburo probably mates in March and 3–7 eggs are fertilized in the vicinity of the nidamental gland of each oviduct. The developing embryo is nourished during the first 3–4 months of gestation by yolk stored in its extensive yolk sac. Approximately three and one-half months after fertilization, the distal portion of the yolk sac becomes convoluted and interdigitates with deep folds in the uterine wall to form a yolk-sac placenta. As the placenta develops, the maternal uterine epithelium is reduced from columnar cells to squamous cells, and the foetal yolk-sac epithelium is reduced from columnar and cuboidal cells to squamous cells. Exchange between the maternal and foetal blood systems takes place through maternal endothelium, reduced maternal epithelium, egg-case membrane, reduced foetal epithelium, and foetal endothelium.     

How within-group behavioural variation and task efficiency enhance fitness in a social group

How task specialization, individual task performance and within-group behavioural variation affects fitness is a longstanding and unresolved problem in our understanding of animal societies. In the temperate social spider, Anelosimus studiosus, colony members exhibit a behavioural polymorphism; females either exhibit an aggressive 'asocial' or docile 'social' phenotype. We assessed individual prey-capture success for both phenotypes, and the role of phenotypic composition on group-level prey-capture success for three prey size classes. We then estimated the effect of group phenotypic composition on fitness in a common garden, as inferred from individual egg-case masses. On average, asocial females were more successful than social females at capturing large prey, and colony-level prey-capture success was positively associated with the frequency of the asocial phenotype. Asocial colony members were also more likely to engage in prey-capture behaviour in group-foraging situations. Interestingly, our fitness estimates indicate females of both phenotypes experience increased fitness when occupying colonies containing unlike individuals. These results imply a reciprocal fitness benefit of within-colony behavioural variation, and perhaps division of labour in a spider society.     

The biology of Portia fimbriata, a web-building jumping spider (Araneae, Salticidae) from Queensland: intraspecific interactions

Portia fimbriata (Doleschall) is an unusual salticid because it spins webs and uses its own webs and those of other species in predation. However, the courtship and threat displays of this species are more like those of typical, cursorial salticids than like typical web-building spiders. During male-female interactions, males perform leg-waving and leg-shaking displays, with legs I and II extended stiffly forward, while distant from the females. Before mounting they tap the females with their legs; and after mounting they tap, scrape and stroke the females' abdomens. Copulation takes place on or near the female's web or on the webs of other species. Hunched-legs displays, with legs I–III highly flexed and held to the side of the body, occur in male-male interactions. Also, during male-female and female-female interactions, females perform hunched-legs displays, strike, charge, ram, embrace, grapple with and leap at conspecifics. Sometimes they lose legs while grappling. After female-female interactions associated with maternal webs, if the resident decamps, the intruder eats the eggs left behind on a suspended leaf, spins a new egg-case over the destroyed one, and oviposits. Adult and sub-adult males co-habit in webs with sub-adult females for as long as 48 days and mate when the spiders mature.     

Factors responsible for the initiation of a second oöcyte maturation cycle in the ovoviviparous cockroach Nauphoeta cinerea

The factors responsible for the initiation of a second oöcyte maturation cycle were investigated by measuring oöcyte growth, vitellogenin titre, and corpus allatum activity after injection of juvenile hormone and/or removal of the egg-case from pregnant females and by performing ovary and corpus allatum transplant experiments.Egg-case removal in late pregnancy results in immediate oöcyte growth, whereas in early pregnancy oöcyte growth is resumed only after a lapse of time, even after injection of juvenile hormone. This, however, induces an immediate increase in the haemolymph vitellogenin titre. A single injection of 2 or 10 μg of juvenile hormone II first stimulates some oöcyte growth after this lapse of time and later activates the corpora allata, which in turn leads to completion of oöcyte maturation. A repeat injection of 10 μg stimulates continuous oöcyte growth without activating the corpora allata. In the presence of an egg case, activation of the corpora allata is suppressed, even after injection of 2 μg of juvenile hormone III, and the oöcytes do not grow. Injection of higher doses stimulates oöcyte growth and leads to expulsion of the egg case in up to 95% of the females. This, however, is not a direct consequence of the increase in size of the ovaries. Ovary transplant experiment show that in young pregnant females the second generation of oöcyte is not yet competent for growth and that ovaries which are competent can mature in young pregnant females, treated with juvenile hormone, whose egg case has been removed.The results are summarized in a model demonstrating the various factors involved in regulating corpus allatum activity in oöcyte maturation and pregnancy and after application of juvenile hormone. We prepose that the corpus allatum activating effect of exogenous juvenile hormone is mediated by the growing oöcyte and that this activation can be suppressed by the continuous presence of exogenous juvenile hormone.     

Adhesion Characteristics of a Novel Synthetic Polydimethylsiloxane for Bionic Adhesive Pads

Materials with appropriate adhesive properties are suitable for the fabrication of bionic adhesive pads. In this study, a novel polydimethylsiloxane （PDMS） material enhanced with two types of crosslinkers, carbon nanotubes and graphene sheets, was fabricated. The Contact Angle （CA） and cross-sectional morphology of the new material were investigated and observed using a CA meter and Scanning Electron Microscopy （SEM）, respectively. CA measurements indicate that the surface energy of the novel material is twice that of the common PDMS material. SEM observations show that carbon nanotubes and graphene sheets are well dispersed in the polymer, a feature that improves the mechanical properties of the new material. The adhesive performance of this novel composite was tested on an in-house fabricated friction machine. Results show that at a preload of only 50 mN, the adhesion of the novel PDMS material is up to -3.7 times that of common PDMS. The maximum macroscale shear strength and normal adhesion reach 4 N·cm^-2 and 1 N·cm^-2, respectively. The adhesive capability of the material is maintained even after hundreds of times of repeated use. This novel material exhibits excellent adhesion, sufficiently high elastic modulus and high repeatability at low preloads.     

The importance of learning young: the use of nesting material in laboratory rats

Unlike mice, adult laboratory rats do not spontaneously build nests when nesting material is offered. As a result, nesting material is often regarded as unsuitable environmental enrichment for laboratory rats. Wild rats and pet rats, however, have been observed to build complex nests from nesting material at hand. It was hypothesized that nest building in rats is an acquired behaviour, rather than genetically predisposed. To test this hypothesis, the progeny of three Wistar rats provided with nesting material (Kleenex tissues) during pregnancy and three standard-housed rats were divided in 34 same-sex couples with access to nesting material: (1) from the age of 8 weeks (n=7); (2) from weaning (n=8); (3) from birth (n=17). The latter were subdivided into two groups after weaning, one provided with Kleenex tissues (n=9), the other with Enviro-dri (n=8). At the age of 12 weeks, all couples were provided with both types of nesting material for one week. Amount, shape, and soiling of the nesting material were scored on weekdays, and behaviour of the rats was scored twice weekly. Results indicated that the older the rats were when first provided with nesting material, the greater the amount of nesting material eaten and soiled, and the nests built were less elaborate. Overall, Enviro-dri was eaten less than Kleenex tissues. It is concluded that rats need to learn the proper use of nesting material. When provided from birth, nesting material is a suitable type of environmental enrichment for laboratory rats.     

Material flow analysis (MFA) of an eco-economic system:a case study of Wujin District,Changzhou,China

The economic and ecological aspects of a social system are coherently linked and can be examined by its material and energy flows.In this study,we used the material flow analysis (MFA) to model the material input and output of the Wujin District of Changzhou City,Jiangsu Province in China.It was revealed that:(1) total material input and material input per capita increased with economic development,while the total material out-put and material output per capita decreased consistently;(2) except for water,the total material input continued to increase.Input of solid materials grew faster than that of gaseous materials,while the total material output declined.The gas output accounted for the largest pro-portion of the output resulting in primary environmental pollution as burned fossil fuel; (3) water use in agriculture continued with an increasing trend while that in industrial and residential sectors decreased per capita.The total wastewater discharge and wastewater discharge per capita decreased with a faster decreasing rate of residential was-tewater discharge followed by industrial wastewater dis-charge; (4) material input per unit GDP fluctuated and material output per unit GDP decreased.A decreasing trend in both water use and wastewater discharge per unit GDP was disclosed.These results suggest that the effi-ciency of resource use in the Wujin District has improved.This weakened the direct link between economic develop-ment and environmental deterioration.Additionally,we discussed the harmonic development between environ-ment and economy.Potential limitations of MFA's application were also discussed.It is suggested that effec-tive measures should be taken for the enforcement of cir-cular economic strategies and the construction of a resource-saving economy     

Optimizing cardiac material parameters with a genetic algorithm

Determining the unknown material parameters of intact ventricular myocardium can be challenging due to highly nonlinear material behavior. Previous studies combining a gradient-search optimization procedure with finite element analysis (FEA) were limited to two-dimensional (2D) models or simplified three-dimensional (3D) geometries. Here we present a novel scheme to estimate unknown material parameters for ventricular myocardium by combining a genetic algorithm (GA) with nonlinear finite element analysis. This approach systematically explores the domain of the material parameters. The objective function to minimize was the error between simulated strain data and finite element model strains. The proposed scheme was validated for a 2D problem using a realistic material law for ventricular myocardium. Optimized material parameters were generally within 0.5% of the true values. To demonstrate the robustness of the new scheme, unknown material parameters were also determined for a realistic 3D heart model with an exponential hyperelastic material law. When using strains from two material points, the algorithm converged to parameters within 5% of the true values. We conclude that the proposed scheme is robust when estimating myocardial material parameters in 2D and 3D models.     

Can the theory of critical distances predict the failure of shape memory alloys?

Components made from shape memory alloys (SMAs) such as nitinol often fail from stress concentrations and defects such as notches and cracks. It is shown here for the first time that these failures can be predicted using the theory of critical distances (TCDs), a method which has previously been used to study fracture and fatigue in other materials. The TCD uses the stress at a certain distance ahead of the notch to predict the failure of the material due to the stress concentration. The critical distance is believed to be a material property which is related to the microstructure of the material. The TCD is simply applied to a linear model of the material without the need to model the complication of its non-linear behaviour. The non-linear behaviour of the material at fracture is represented in the critical stress. The effect of notches and short cracks on the fracture of SMA NiTi was studied by analysing experimental data from the literature. Using a finite element model with elastic material behaviour, it is shown that the TCD can predict the effect of crack length and notch geometry on the critical stress and stress intensity for fracture, with prediction errors of less than 5%. The value of the critical distance obtained for this material was L?=?90?μm; this may be related to its grain size. The effects of short cracks on stress intensity were studied. It was shown that the same value of the critical distance (L?=?90?μm) could estimate the experimental data for both notches and short cracks.     

A protein-glucan intermediate during paramylon synthesis.

A sodium deoxycholate extract containing glucosyltransferase activity was obtained from a particulate preparation from Euglena gracilis. It transferred glucose from UDP-[14C]glucose into material that was precipitated by trichloroacetic acid. This material released beta-(1 leads to 3)-glucan oligosaccharides into solution on incubation with weak acid, weak alkali and beta-(1 leads to 3)-glucosidase. The products of the incubation of the deoxycholate extract with UDP-[14C]glucose were analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Radioactive bands were obtained that had the properties of beta-(1 leads to 3)-glucan covalently linked to protein by a bond labile to weak acid. High-molecular-weight material containing a beta-(1 leads to 3)-glucan was also shown to be present by gel filtration. The bond linking glucan to aglycone is possibly a pyrophosphate linkage. It is proposed that in Euglena gracilis beta-(1 leads to 3)-glucan (paramylon) is synthesized on a protein primer.     

Thiobarbiturate-reacting Materials in Microorganisms

The amount of thiobarbiturate-reacting material in 51 strains of bacteria and three yeasts was determined. Reactive material was found to be present in all of the gram-negative bacteria examined. It was assumed that the reactive material in this case was primarily 2-keto-3-deoxyoctonate (KDO), an eight-carbon sugar acid which is usually associated with the cell wall lipolysaccharide of members of the Salmonella-Escherichia group. Very little reactive material could be detected in the gram-positive species and yeasts that were examined. When expressed as per cent dry weight, the gram-negative bacteria exhibited about eight times more reactive material than the gram-positive species. It is suggested that the small amount of reactive material detected in gram-positive cells and yeasts is due to compounds other than KDO.     

Some Nutritional Characteristics of a Naturally Occurring Alga (Microcystis sp.) in a Guatemalan Lake

The nutritional characteristics of an alga (Microcystis sp.) that occurs naturally in a Guatemalan lake were determined. The sun-dried material proved to have a high protein content (55.6%) and to be a possible good source of calcium and phosphorus (1, 169.1 and 633.4 mg/100 mg, respectively). Amino acid analysis showed that total sulfur amino acids were the most deficient ones, giving a protein score of 42 to the material. The in vitro protein digestibility of the material was 69.5%. Biological trials demonstrated that when the material was offered as the only protein source, very low consumption and a high mortality rate were obtained whether or not the diet was supplemented with 0.4% dl-methionine. However, when the material supplied 25% of the total protein of a corn-algae diet, the protein quality of the cereal was significantly improved (P < 0.05).