摩鹿加云斑蛛卵袋结构与纤维组成

采用扫描电子显微镜（SEM）和氨基酸自动分析仪对摩鹿加云斑蛛Cyrtophora moluccensis卵袋的结构和组成进行了观察研究.结果表明摩鹿加云斑蛛的卵袋呈椭球状,是由多种丝腺纺出的微米与纳米级的丝纤维形成的多个覆盖层构成的,包括白色框架、军绿色与灰白色外覆盖层和白色内覆盖层3部分.卵袋框丝与典型的拖牵丝氨酸组成基本相似,丙氨酸和甘氨酸的含量最丰富,分别约占39%和33%,其次是谷氨酸、丝氨酸和脯氨酸,分别约占7.8%、5.7%和3.6%;其余卵袋丝纤维的氨基酸组成与典型的柱状腺丝相似,与卵袋框丝相比,卵袋覆盖层的丝氨基酸的含量显著增加,约占21%,同时甘氨酸和脯氨酸的含量显著减少,分别约占12%和1%,并含有更多的极性和大侧链氨基酸,其丙氨酸的含量变化不大,仍占了27%左右.根据氨基酸组成与扫描电镜的结果综合分析了不同自径丝纤维的丝腺来源.     

寡居种悦目金蛛若蛛群居机制初步研究

对寡居种悦目金蛛Argiope amoena若蛛群居生活对其结网的影响、温度和种群大小对若蛛存活率的影响、若蛛对限制性空间的利用及其扩散方式进行了观察和研究.结果表明,若蛛从卵袋出蛰后不经历群居扩散即具备结网能力,可结完整网,也具备在扩散前不进食水存活的能力;在变温条件下若蛛存活率要远远高于室温条件下的存活率,而在室温条件下若蛛开始死亡和半数死亡的时间比其聚居期长得多;若蛛主要通过群体空中扩散的方式进行扩散,可以减小能耗与敌害的威胁;不同种群大小的若蛛在限制性空间的分布均从第5d左右开始发生较大变化的,这与在空间不受限的条件下若蛛在第5d开始扩散的结果是一致的.据此我们推断:个体扩散代价最小化(包括御敌和能耗)和维持种群较高的生存率可能是寡居种悦目金蛛若蛛群居生活的主要原因.     

Structure,composition and mechanical properties of the silk fibres of the egg case of the Joro spider, <Emphasis Type="Italic">Nephila clavata</Emphasis> (Araneae,Nephilidae)

The silk egg case and orb web of spiders are elaborate structures that are assembled from a number of components. We analysed the structure, the amino acid and fibre compositions, and the tensile properties of the silk fibres of the egg case of Nephila clavata. SEM shows that the outer and inner covers of the egg case consist of thick, medium and thin silk fibres. The silk fibres of the outer cover of the egg case are probably produced by the major and minor ampullate glands. The silk fibres of the inner cover of the egg case from cylindrical glands appears to be distinct from the silk fibres of the major ampullate glands based on their micro-morphology, mole percent amino acid composition and types, and tensile behaviour and properties. Collectively, our investigations show that N. clavata uses silk fibres from relatively few glands in varying combinations to achieve different physical and chemical properties (e.g., color, diameter, morphology and amino acid composition) and functional and mechanical properties in the different layers of the egg case.     

Spiderling sex ratio and maternal investment in the bolas spider Mastophora cornigera (Araneae,Araneidae)

Male Mastophora cornigera exit egg sacs as adults, which allowed us to determine spiderling sex ratios and patterns of maternal investment in this species. We collected 15 egg sacs produced by seven mothers, which yielded 1945 emergent spiderlings which were sexed, 1850 of which were weighed. Two emergent broods were significantly male and female biased and were unaffected by pre-emergence mortality. The weights of male and female spiderlings differed in eight broods, with males and females being heavier in four cases each. Five of these broods were derived from multiple egg sac sets produced by one mother, and in each case, the total mean male and female spiderling weights for all broods in a set were biased in the same direction as the biased brood(s) within that set. Mean emergent spiderling weight was independent of brood size and sex ratio for both males and females. Despite such independence, sex allocation in M. cornigera can favor sons, daughters, or both equally, and by numbers, by weight, or both at once. The proximate mechanisms and adaptive significance of such variability is unknown. We also review evidence for gender-biased allocations in arachnid offspring and suggested mechanisms for their applicability to M. cornigera.     

Adaptive advantages of maternal care and matriphagy in a foliage spider,Chiracanthium japonicum (Araneae: Coubionidae)

I examined the function of maternal care in a foliage spider,Chiracanthium japonicum. Females of this species make breeding nests with rolled-up grass leaves and provide themselves to spiderlings as food at the end of maternal care. By removing mothers from their offspring at 2 different times, the effects of maternal care on egg and spiderling survival rates were estimated separately. Mother attendance greatly improved survival and development of eggs as well as spiderlings. Detailed observations on the fate of immatures in breeding nests with and without their mothers showed lower hatching and spiderling emergence rates when mothers were removed. Furthermore, spiderlings that fed on their mother’s body showed accelerated growth and quickly molted into the 3rd instar with the delay of dispersal. This suggests that matriphagy, or eating the mother, enables spiderlings of this species to disperse at a later instar. Therefore, I conclude that the maternal care of this spider consists of guarding offspring, supporting offspring development and feeding spiderlings.     

Variation in life-history characteristics over a clinal gradient in three populations of a communal orb-weaving spider

Summary Adult size and fecundity, total reproductive biomass, egg size, and spiderling size and resistance to desiccation were compared in three populations of the communal orb-weaving spider,Metepeira spinipes, in Mexico. In a desert population and in one from a moist tropical forest adult size, fecundity, and total reproductive biomass were similar, but were markedly smaller than in a climatologically intermediate agricultural habitat. Egg size and protein content were greater in the desert and agricultural habitats than in the moist forest, but spiderling size increased from desert to agricultural to moist forest populations. Desert spiderlings survived significantly longer than moist forest spiderlings at all humidity treatments over a 10% to 100% range. An explanation for these results is proposed based on apparent differences in energy allocation and expenditure which arise from the distinct climate, colony structure, and prey and space availability in the three habitats.     

Araneoid egg case silk: a fibroin with novel ensemble repeat units from the black widow spider, Latrodectus hesperus

Araneoid spiders use specialized abdominal glands to manufacture up to seven different protein-based silks/glues that have diverse physical properties. The fibroin sequences that encode egg case fibers (cover silk for the egg case sac) and the secondary structure of these threads have not been previously determined. In this study, MALDI tandem TOF mass spectrometry (MS/MS) and reverse genetics were used to isolate the first egg case fibroin, named tubuliform spidroin 1 (TuSp1), from the black widow spider, Latrodectus hesperus. Real-time quantitative PCR analysis demonstrates TuSp1 is selectively expressed in the tubuliform gland. Analysis of the amino acid composition of raw egg case silk closely aligns with the predicted amino acid composition from the primary sequence of TuSp1, which supports the assertion that TuSp1 represents a major component of egg case fibers. TuSp1 is composed of highly homogeneous repeats that are 184 amino acids in length. The long stretches of polyalanine and glycine-alanine subrepeats, which account for the crystalline regions of minor ampullate and major ampullate fibers, are very poorly represented in TuSp1. However, polyserine blocks and short polyalanine stretches were highly iterated within the primary sequence, and (13)C NMR spectroscopy demonstrated that the majority of alanine was found in a beta-sheet structure in post-spun egg case silk. The TuSp1 repeat unit does not display substantial sequence similarity to any previously described fibroin genes or proteins, suggesting that TuSp1 is a highly divergent member of the spider silk gene family.     

Hatching of an estuarine crab, Sesarma haematocheir: from disappearance of the inner (E3) layer to rupture of the egg case

Hatching of decapod crustaceans is characterized by the sudden rupture of the egg case. This study focused on the following two issues regarding the hatching mechanism of the estuarine terrestrial crab Sesarma haematocheir: (1) dissolution of the egg case, and (2) the site where the egg case breaks. The egg case comprises three layers: the outer two (E1 and E2) layers and the inner (E3) thin layer (0.2 microm in thickness). The outer layers showed no morphological changes upon hatching, but the inner layer (E3) was markedly digested. The digestion of this layer would enable the embryo to absorb ambient water via reverse peristalsis of the intestine, resulting in an increase of the volume. The egg case always ruptured perpendicular to the longitudinal axis of the embryo. In addition, breakage of the egg case occurred at the dorsal thorax of the embryo. The three major organs positioned at this area were (1) a sharp projection (dorsal spine), (2) an assemblage of muscles, and (3) a pair of secretory glands, each of which was about 30 microm in diameter. The dorsal projection is soft before hatching, and it is clear that the egg case does not break with the posterior expansion of this projection. The rupture instead appears to be caused by the expansion of the muscles arranged perpendicular to the body axis. In addition, some (unknown) factor might weaken the egg case just before hatching. The secretory glands may be a kind of rosette gland, but the role that this gland plays at hatching is not known. As a duct comes out from the center and enters the dorsal projection, some active substance may be released at the tip of this projection. However, immunochemical studies are not consistent with this substance being an ovigerous hair stripping substance (OHSS).     

Novel molecular and mechanical properties of egg case silk from wasp spider, Argiope bruennichi

Araneoid spiders use specialized abdominal glands to produce up to seven different protein-based silks/glues that have various mechanical properties. To date, the fibroin sequences encoding egg case fibers have not been fully determined. To gain further understanding of a recently reported spider silk protein gene family, several novel strategies were utilized in this study to isolate two full-length cDNAs of egg case silk proteins, cylindrical silk protein 1 (CySp1, 9.1 kb) and cylindrical silk protein 2 (CySp2, 9.8 kb), from the wasp spider, Argiope bruennichi. Northern blotting analysis demonstrated that CySp1 and CySp2 are selectively expressed in the cylindrical glands. The amino acid composition of raw egg case silk was closely consistent with the deduced amino acid composition based on the sequences of CySp1 and CySp2, which supports the assertion that CySp1 and CySp2 represent two major components of egg case silk. CySp1 and CySp2 are primarily composed of remarkable homogeneous assemble repeats that are 180 residues in length and consist of several complex subrepeats, and they contain highly homologous C-termini and markedly different N-termini. Our results suggest a possible link between CySp1 and CySp2. In addition, comparisons of stress/strain curves for dragline and egg case silk from Argiope bruennichi showed obvious differences in ultimate strength and extensibility, and similarities in toughness.     

A histochemical study of the secretory gland cells of Cercaria shikokuensis and their role during development from cercaria to metacercaria.

The roles of secretory glands during the developmental process from an immature cercaria to a metacercaria in Cercaria shikokuensis were studied. Four types of secretory cells were identified in this species. On maturation of the cercaria in redia, the products of ventral gland cells and mucoid gland cells formed a thick surface coat on the mature cercaria, and the products of cephalic gland cells also formed a thin cover on the surface coat. In the process leading to the formation of a metacercaria, the surface coat constituted the outer layer of the cyst, mucoid gland cells secreted mucous substances inside the wall, and then cystogenous gland cells discharged their products to the inner wall. The cyst wall was composed of four layers, and it was thought that the outermost surface layer helped the cyst wall to adhere to the matrix and the intermediate layers helped to put together outer and inner walls.     

Food imprinting and subsequent prey preference in the lynx spider,Oxyopes salticus (Araneae: Oxyopidae)

This object of this study was to determine if early feeding experience can affect subsequent prey choice in lynx spiderlings (Oxyopes salticus), and if so, is it evidence for food/olfactory imprinting. After emergence from the egg sac, three groups of 10 spiderlings were each fed exclusively for a 1-week period on one of three naturally-occurring prey species (crickets): group 1 fed on nymphs of Gryllotalpa hexadactyla; group 2 (Dialeurodes citrifoli); group 3 (Microcentrum rhombifolium). Following this, they were tested for subsequent prey preference in choice tests conducted in a plastic arena. Each spiderling was presented simultaneously with one individual of each prey species in a randomized design. Spiderlings exhibited a significant first preference for the original diet. Thus, experience with certain foods encountered by newly hatched spiderlings can affect subsequent prey preference in this species. Given the primacy of the early experience, the results are best interpreted in terms of imprinting and represent the first demonstration of olfactory imprinting in a spider.     

Organic structures of the hypercalcified peritubular matrix in horse dentine.

EDTA-insoluble organic structures of the hypercalcified peritubular matrix (PM) in horse dentine were observed by scanning electron microscopy. The PM was enveloped in double cylindrical structures composed of fibrillar sheaths in the inner and outer peripheries. Between the outer fibrillar sheath and intrinsic fibrils of the intertubular matrix, a calcified cementing membrane existed. Within the PM, warped cone-shaped structures of fibrillar sheaths, overlapping at intervals of 4-6 microns and semiconcentrically surrounding the dentinal tubule, extended from the inner fibrillar towards the outer fibrillar sheath. The cone-shaped fibrillar sheaths following the inner and outer fibrillar sheaths were identified as the incremental lines of the PM. Most of these fibrils may be collagen although it could not be confirmed, whereas non-collagenous organic materials in the lateral branches of the dentinal tubule are radially arranged in the PM. These EDTA-insoluble structures were three-dimensionally illustrated using an image-analysing system.     

Seasonal changes in resource allocation within an individual offspring of the wolf spider, Pardosa pseudoannulata (Araneae: Lycosidae)

Abstract.  Seasonal changes in resource investment into individual offspring are well documented, but no attention has been paid to the allocation of the invested resource among the body parts of the offspring. In the present study, seasonal changes in the absolute and relative sizes in a spiderling of the wolf spider Pardosa pseudoannulata Boes. et Str. are investigated, and the relationship between spiderling body size and the ability to moult during a food shortage is clarified. Spiderlings that emerge in November have a significantly larger cephalothorax and abdomen than those that emerge in June. In addition, the abdomen–cephalothorax size ratio is significantly greater in November than in June offspring. Under limited food availability conditions, only 40% of spiderlings moult. Nymphs that do moult have a significantly larger cephalothorax, abdomen and abdomen–cephalothorax size ratio than nymphs that do not moult. Thus, both the quantity of resources invested in the cephalothorax and abdomen of a spiderling and the proportional allocation of resources between the two body parts change seasonally in Pa. pseudoannulata ; alteration of the resource allocation occurs in late autumn. Larger spiderlings of Pa. pseudoannulata that emerge in late autumn would be able to develop into advanced instars even during food shortage, and therefore may have better overwintering survival rates.     

横纹金蛛卵袋结构与纤维组成

采用SEM和氨基酸自动分析仪对横纹金蛛(Argiope bruennichi)卵袋的超微结构与氨基酸组成进行了观察研究.结果表明,横纹金蛛卵袋呈封闭的葫形,是由多种丝腺纺出的微米与纳米级的丝纤维形成的多个覆盖层构成,具有多层复杂结构,从外向内分别为:框架、卵袋覆盖帽、外覆盖层和内覆盖层、卵块覆盖帽、卵块包裹层,其中外覆...     

Adhesive compatibility of cribellar and viscous prey capture threads and its implication for the evolution of orb-weaving spiders

Evolution of orb-weaving spiders that comprise the Orbiculariae clade involved a transition in the composition of prey capture thread that has been challenging to explain. The primitive cribellar threads spun by members of the Deinopoidea subclade resemble the capture threads of their non-orb-web-weaving ancestors and are formed of thousands of fine, dry, protein cribellar fibrils. In contrast, the derived viscous capture threads spun by members of the Araneoidea subclade have regularly spaced, aqueous adhesive droplets. When second instar deinopoid spiderlings emerge from egg sacs they are unable to spin cribellar threads, and, therefore, do not construct orb-webs; whereas second instar araneoids spin capture threads and construct orb-webs. If, as we hypothesize, viscous material evolved to enable second instar spiderlings to construct orb-webs, early araneoids may have spun composite cribellar-viscous capture threads. To examine the functional feasibility of such intermediate capture threads, we compared the adhesion of cribellar threads, viscous threads, and combined cribellar-viscous threads. The stickiness of these combined threads was greater than that of native cribellar or viscous threads alone. The viscous material of Araneus marmoreus threads exhibited a substantial increase in stickiness when combined with cribellar fibrils and that of Argiope aurantia threads a small increase in stickiness when combined with cribellar fibrils. Thus, if early araneoids retained their ability to spin cribellar threads after having evolved glands that produced viscous material, their composite threads could have formed a functional adhesive system that achieved its stickiness at no loss of material economy.     

Biology and behaviour of the neotropical ant-mimicking spider Aphantochilus rogersi (Araneae: Aphantochilidae): nesting, maternal care and ontogeny of ant-hunting techniques

Aphantochilus rogersi is an ant-mimicking spider that preys exclusively on cephalotine ants. The spiders oviposit in close proximity to nests of the model ant Zacryptocerus pusillus , and emergent spiderlings tend to remain in the vicinity of natal egg sacs. Females of A. rogersi actively defend their egg sacs against approaching workers of Z. pusillus , but the latter may sometimes destroy the eggs. Feeding specialization on these ants is confirmed by more than 300 observation of young and adult A. rogersi carrying ant corpses in the field. Although A. rogersi possesses several behavioural traits which may reduce the risk of being injured by ants during subjugation, field and laboratory observations showed that social defence by Z. pusillus may cause mutilation to the spiders. Tests in captivity revealed an ontogenetic change in the prey-capture techniques employed by A. rogersi. Early-instar spiderlings can apparently only seize the ant's petiole tightly if they are able to approach the ant from the front. As the ant is paralysed, the spiderling positions itself vertically in relation to the substratum. Larger spiders, on the other hand, attack ants most frequently from behind, and seem better equipped to seize the ant's petiole firmly with their larger chelicerae. Owing to their greater strength, late-instar spiders are able to lift the struggling ant aloft. The selection of a suitable oviposition site, the mother's ability to defend herself and the eggs from nearby ants, and the capacity to capture and subdue ants safely from emergence to maturity, are regarded as crucial traits inherent in the mimetic and feeding specialization by A. rogersi.     

The role of spider cocoons in controlling desiccation

Summary The abilities of the cocoons of the spiders Mecynogea lemniscata and Argiope aurantia to protect the enclosed egg and spiderling stages from desiccation were investigated in the laboratory under controlled humidities, and in the field under ambient conditions. For M. lemniscata, which has a relatively small clutch (8–30 eggs) and remains in the cocoon for approximately 9–10 months, removal of the cocoon had no effect on water loss from the egg stage, nor did it adversely affect hatching or molting success. Cocoon removal did, however, significantly affect water loss and, consequently, survival in the spiderling stage at all humidities in the laboratory and in the field. The importance of the cocoon for survival is probably related to the unusually long time M. lemniscata spiderlings spend in the cocoon overwintering. For A. aurantia, which has a substantially larger clutch size (300–1400 eggs) and remains in the cocoon for a shorter 6–7 months, cocoon removal had no effect on water loss, egg hatching success, molting success, nor spiderling survival. The lack of an effect suggests that other factors (e.g., relative humidity at the oviposition site, or a large clutch size) may be more important in controlling water loss for A. aurantia.     

Diversity of molecular transformations involved in the formation of spider silks

Spiders that spin orb webs secrete seven types of silk. Although the spinning process of the dragline thread is beginning to be understood, the molecular events that occur in spiders' opisthosomal glands, which produce the other fibers, are unknown due to a lack of data regarding their initial and final structures. Taking advantage of the efficiency of Raman spectromicroscopy in investigating micrometer-sized biological samples, we have determined the secondary structure of proteins in the complete set of glands of the orb-weaving spider Nephila clavipes. The major and minor ampullate silks in the sac of their glands have identical secondary structures typical of natively unfolded proteins. Spidroins are converted into fibers containing highly oriented β-sheets. The capture spiral represents a distinct structural singleton. The proteins are highly disordered prior to spinning and undergo no molecular change or alignment upon spinning. The cylindrical, aciniform, and piriform proteins are folded in their initial state with a predominance of α-helices, but whereas the cylindrical gland forms a fiber similar to the major ampullate thread, the aciniform and piriform glands produce fibers dominated by moderately oriented β-sheets and α-helices. The conformation of the proteins before spinning is related to intrinsic characteristics of their primary structure. Proteins that are unfolded in the gland have repeat sequences composed of submotifs and display no sequence regions with aggregation propensity. By contrast, the folded proteins have neither submotifs nor aggregation-prone sequence regions. Taken together, the Raman data show a remarkable diversity of molecular transformations occurring upon spinning.     

Offspring recognition by mother crab spiders with extreme maternal care

Maternal care is provided by several spider species, but there are no reports of mother spiders recognizing their young, which suggests that maternal care can be exploited by unrelated individuals. Diaea ergandros, a crab spider with extreme, sacrificial maternal care, does accept unrelated spiderlings (ca. 43.9% of spiderlings) into its nest in areas of high nest density. However, a field and a laboratory experiment with mother spiders and natural and adoptive spiderlings demonstrated that mothers did recognize their own offspring. Recognition was not expressed in survival as adopted (unrelated) spiderlings had similar survival rate to that of natural offspring. Instead it was displayed in growth; mother D. ergandros caught large prey items for their own offspring, but not for adopted spiderlings, and so natural offspring grew more than adopted spiderlings. Also, mothers produced trophic oocytes, which are important for the sacrificial care that influences spiderling survival, only when they lived with their own offspring.     

Drop and swing dispersal behavior of a tropical wandering spider: experiments and numerical model

Summary When exposed to certain air flows spiderlings of the wandering spider Cupiennius getazi (Ctenidae) drop from their dwelling plant and swing in the wind from a gradually lengthening dragline. If body contact is made with a nearby substrate the spiderling detaches. We refer to this form of aerial dispersal as the drop and swing dispersal behavior (DASDB). The dragline being only up to about 70 cm long and only rarely ruptured by the drag forces of the wind, this is a close range type of dispersal as opposed to the ballooning known for many other species of spiders. DASDB is readily elicited in spiderlings at an age of ca. 9 days (outside egg sac). At this age their mass is 1.26 ±0.35 mg and their yolk usually depleted. They then start to catch prey and escape from the unfavorable conditions in the small space around the egg sac where hundreds of spiderlings compete. Air flow rates effectively eliciting DASDB in the laboratory are between 0.2 m/s and 1.5 m/s. The number of spiderlings showing DASDB increases considerably if the air flow is turbulent as opposed to laminar. A numerical model defining the window within which DASDB is supported mechanically was developed from theoretical considerations. Taking the effective wind speeds and the mechanical properties of the dragline, the model accounts very well for the fact that actual rupture of the dragline was observed only rarely in C. Getazi. Other features of the DASDB are also correctly predicted. The model is not only applicable to DASDB but also to the drop and swing preballooning behavior known to occur in several other species of spiders.Abbreviations DASDB drop and swing dispersal behavior