The cuticular scales of Lynx spiders (Araneae,Oxyopidae)

An examination of the cuticular scales of the lynx spiders Oxyopes aglossus, O. salticus, and Peucetia viridans using scanning electron microscopy revealed that scales in these spiders are morphologically distinct, yet similar to the scales of the jumping spiders Eris militaris and Hentzia mitrata. Like the cuticular scales of jumping spiders, the cuticular scales of lynx spiders exhibit morphological differentiation in regard to location of occurrence on the body, with scales near the eyes tending to have more numerous and larger spines on the superior surface than scales on other regions of the prosoma and opisthosoma. The functional significance of this differentiation in scale morphology is unknown. Sexual dimorphism and ontogenetic variation in scale morphology and color were observed in the genus Oxyopes,but not in Peucetia. In addition, the scales of P. viridans were distinguishable from the scales of Oxyopes spp. on the basis of the number of apical spines (1 in P. viridans instead of 3–7 in Oxyopesspp.) and on the presence of spines on the inferior surface (many in P. viridans and none in Oxyopesspp.). J. Morphol. 236:223-231, 1998. © 1998 Wiley-Liss, Inc.     

The ultrastructure of the book lungs of the Italian trap-door spider Cteniza sp. (Araneae,Mygalomorphae, Ctenizidae)

The fine structure of book lungs is not homogeneous across Arachnids and is considered phylogenetically informative, however few reports on the ultrastructural features of this organ have been published. In this study, we examined the general morphology and ultrastructure of adult spiders of the genus Cteniza. The respiratory system of Cteniza sp. consists of two pairs of well-developed book lungs, which is considered indicative of primitive spiders. The general organization of the book lungs is similar to that described for other arachnids and consists of leaves of alternating air and hemolymph channels. The air channels are lined with cuticle and open to an atrium that leads to a slit-like spiracle. The air channels are held open by cuticular trabeculae. The space holders in the hemolymph channels are pillar trabeculae formed by two cells from the opposed walls. The pillar cells have a complex ultrastructure that includes an interdigitating connection, gap junctions, microtubules and hemidesmosomes. These features apparently help strengthen the pillar cells and their interconnections with each other and the underlying cuticle. The cytoskeleton resembles that of arthropod tendon cells where substantial structural support is needed.     

Water limitation prevails over energy in European diversity gradients of sheetweb spiders (Araneae: Linyphiidae)

Across large spatial scales, species richness in many taxa is mainly determined by climatic variables. However, some of the mechanisms behind large-scale patterns of species richness and abundance are expected to act on the community level, and on a smaller scale than the resolution of the data commonly used for deriving these patterns. We studied the distribution of sheetweb spiders (Araneae: Linyphiidae) across Europe using both standardised samples from local habitats and large-scale inventories. In the first approach, we analysed species and individual numbers from standardised pitfall traps from 17 locations distributed from northern Sweden to Spain and Greece. We also calculated Simpson indices to correct for different activity densities. Additionally, we analysed whether diversity of sheetweb spiders is sensitive to habitat type. In the second approach, we investigated the known sheetweb spider species richness of European countries and large islands. In both datasets, species richness of sheetweb spiders reached a maximum at about 55°N and declined towards the Mediterranean and the Arctic. In addition, species richness decreased from western (maritime) to eastern (continental) regions. Also Simpson diversity showed a hump-shaped relation to latitude, and was the only variable influenced by habitat type. In contrast to species richness and diversity, activity density increased monotonously with latitude. Towards the north, sheetweb spiders are likely limited by energy availability, towards the south, water limitation as well as bottom-up and top-down community interactions may reduce sheetweb spiders. Accordingly, their diversity does not follow the pattern of vertebrates, large insects and aquatic organisms, which depend more strongly on energy availability.     

Aged pesticide residues are detrimental to agrobiont spiders (Araneae)

Spiders are among the most abundant arthropods in agroecosystems, playing an important role as natural enemies of various pests. In this study we evaluated residual activity of selected pesticides on the mortality and behaviour of four spider species (Dictyna uncinata, Pardosa palustris, Philodromus cespitum and Theridion impressum). We used three pesticides: a herbicide Command (clomazone), and insecticides Decis (deltamethrin) and Nurelle (chlorpyrifos and cypermethrin). Mortality was recorded after exposure of spiders to fresh (2-h), 5, 10, 15 and 20-day-old residues. For each residue mortality was evaluated after 24–72 h. Residual effect differed between preparations and, in some cases, between spiders. All of the Nurelle residues (fresh to 20-day-old) caused 100% mortality in all spider species. Residues of Command were rather harmless (causing <20% mortality) to all spider species as the herbicide activity declined with age. Residues of Decis had species-specific effects as the mortality varied between 0 and 90%. In Dictyna the mortality gradually declined with the age of residues, while in Pardosa the mortality increased. In Philodromus and Theridion the mortality declined up to 10-day-old residues and then increased so that 20-day-old residues caused almost as high mortality as the new ones. Exposure to pesticide residues immediately affected the movement of Pardosa spiders. Residues of Decis and Nurelle decreased spider locomotion, while those of Command increased locomotion in comparison with the control. In another experiment, we studied repellence of fresh pesticide residues to Pardosa spiders. In comparison with the control, spiders stayed a similar time on the surface treated with Command, but four times less on Decis and nine times less on Nurelle-treated surfaces, respectively. In conclusion, aged insecticide residues possess a high activity and can cause long-term decline in the abundance and prolonged behavioural disturbance of spiders in agroecosystems.     

Predator-prey interactions between jumping spiders (Araneae, Salticidae) and Phokus phalangioides (Araneae, Pholcidae)

Portia is a genus of specialized web-invading salticids that use aggressive mimicry. Some other salticids leap into webs to catch spiders but do not use aggressive mimicry. Pholcus phalangioides is a web-building spider with a special defensive behaviour—called whirling—in which it swings its body around in a circle while keeping its long legs on the silk. Pholcus phalangioides is preyed on by Portia and probably other salticid spiders in nature. Interactions between P. phalangioides and 13 species of salticids were studied in the laboratory to compare how effective salticids with different styles of predation were at catching the pholcids. Four species of Portia were studied and each was more efficient at catching P. phalangioides than were the other nine salticids tested. For one species—Portia fimbriata—individuals from three different populations were studied. The Queensland P. fimbriata used aggressive mimicry more consistently and were more efficient at catching P. phalangioides than were the other species of Portia and the other populations of P. fimbriata . The salticids that were the most efficient at catching pholcids were also better able to avoid setting off whirling by the pholcids. An experiment in which pholcids were artificially induced to whirl whenever the predator was near provided additional evidence that whirling is an effective defence of pholcids against predation by salticids.     

Contrasting responses of arable spiders to the landscape matrix at different spatial scales

Aim Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales. Location Thirty‐eight landscapes around the cities of Göttingen and Giessen, Germany. Methods Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land‐use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness. Results In both study regions, local species richness was enhanced by non‐crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long‐jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non‐crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non‐crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances. Main conclusions Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non‐crop habitats.     

The female genitalic morphology of “micronetine” spiders (Araneae,Linyphiidae)

Current knowledge of “micronetine” female genitalia is almost exclusively based on transmitted light microscopy data. As such, our understanding of the epigynal anatomy is incomplete and somewhat misleading, to the extent that it hinders comparative studies of linyphiid diversity. We used scanning electronic microscopy (SEM) to study the complex epigynal morphology of “micronetine” spiders. Enzymatic digestion of soft tissues allowed us to examine the internal chitinized structures in detail using SEM. A taxonomic sample of nine species was selected to represent the morphological genitalic diversity of female “micronetines” (including one member of the Erigoninae clade). Results reveal that the epigynum consists of a pair of grooves formed by integument folds (copulatory and fertilization grooves). The protruding epigynal region is divided into a ventral and a dorsal plate by the grooves; both plates can be modified to form an epigynal cavity and/or a scape. Our observations confirm the widespread occurrence of epigynal grooves, rather than ducts, in “micronetines”. Epigynal grooves seem to be common in linyphioids and other spider groups.     

Phosphatases in the central nervous system of spiders (Arachnida, Araneae).

The central nervous systems of web-building spiders (Araneidae, Agelenidae) and hunting spiders (Lycosidae, Salticidae) were tested for non-specific and specific phosphatases. Acid phosphatase exhibited weakly to moderately positive reactions in the neuronal cell bodies and in the neuropile fibre mass of all species investigated. Alkaline phosphatase could only be demonstrated in the external and internal neural lamellae of the brain and ventral cord of several specimens of the araneid species investigated. Tests for thiamine pyrophosphatase were negative with both the lead and calcium-cobalt methods. Distinctive positive reactions for adenosine triphosphatase were visible in the nervous system of all the species used, being especially strong in the optic ganglia of the hunting spiders. The demonstration of adenosine triphosphatase was only possible when applying the calcium-cobalt method after Padykula and Herman, while the lead method after Wachstein and Meisel did not produce any staining reaction at all. Controls of the histochemical reaction showed that the enzyme was activated by Ca2+ and inhibited by sulphydryl destroying reagents (e.g. PCMB), but was insensitive to ouabain. It could be probably classified as a mitochondrial proton-translocating adenosine triphosphatase.     

How to catch foliage-dwelling spiders (Araneae) in maize fields and their margins: a comparison of two sampling methods

The foliage‐dwelling spider fauna was collected in maize fields and on stinging nettles in adjacent margins in Bavaria, South Germany. Two different sampling methods were evaluated: drop cloth sampling and suction sampling. The overall catch was dominated by juvenile spiders, web‐building spiders, and spiders of the families Theridiidae, Linyphiidae, Tetragnathidae and Araneidae (in decreasing order). Field margins harboured more species than maize fields, whereas the total spider abundance was higher in the maize crop. Web‐building spiders such as Theridiidae and Linyphiidae were prominent in maize by individual numbers. Suction sampling with a small suction device proved to be a more efficient and consistent sampling method for foliage‐dwelling spiders than drop cloth sampling. Density and species richness of foliage‐dwelling spiders in maize was shown to be fairly high, implying that spiders of higher strata may play a more important role in biological control than suspected up to now.     

Die feinstruktur der flüigelschuppen einiger Lycaeniden (Insecta,Lepidoptera)

Green, blue and violet colours of Lycaenidae examined by us — with the exception of Rapala arata (Theclinae) — are due to iridescent scales which are arranged before a dark background. The iridescent scales are constructed according to the Urania-type and may be diverted from pigmented scales by laying in equidistant lamellae and little cuticular bars, which maintain the distance between the lamellae. The ribs in the longitudinal axis of the scales contain lamellae and bars only in the Plebejinae, in Lycaeninae and Theclinae they are small and sit on the plain upperside of the scale with a narrow base.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

Functional genital morphology of armored spiders (Arachnida: Araneae: Tetrablemmidae)

This study describes the female genitalia of the tetrablemmid spiders Brignoliella acuminata, Monoblemma muchmorei, Caraimatta sbordonii, Tetrablemma magister, and Ablemma unicornis by means of serial semi‐thin sections and scanning electron microscopy and compares the results with previous findings on Indicoblemma lannaianum. Furthermore, the male palps and chelicerae are briefly described. The general vulval organization of females is complex and shows similarities in all of the investigated species. The copulatory orifice is situated near the posterior margin of the pulmonary plate. The opening of the uterus externus lies between the pulmonary and the postgenital plate. Paired copulatory ducts lead to sac‐like receptacula. Except for A. unicornis, the male emboli of all investigated species are elongated and thread‐like. However, they are too short to reach the receptacula. Hence, the spermatozoa have to be deposited inside the copulatory ducts. The same situation was also found in I. lannaianum. Females of this species store sperm encapsulated in secretory balls in their receptacula. The secretion is produced by glands adjoining the receptacula. The presence of paired fertilization ducts and spermatozoa in the uterus internus suggested that fertilization takes place internally in I. lannaianum. Secretory balls in the receptacula are found in all of the investigated species in this study, showing that sperm are stored in the same way. The place of fertilization may also be identical since dark particles, presumably spermatozoa, are located in the uterus internus of all investigated species except for T. magister. However, fertilization ducts are only found in B. acuminata and M. muchmorei. A sclerotized central process with attached muscles is present in A. unicornis, M. muchmorei, C. sbordonii and T. magister. Only in A. unicornis does the central process show an internal lumen and hold spermatozoa. In the other species, it could be used to lock the uterus during copulation in order to prevent sperm from getting into it as suggested for certain oonopid species. The uterus externus of all investigated species shows a sclerotized dorsal fold with attached muscles, previously described as “inner vulval plate.” Contractions of the muscles lead to a widening of the dorsal fold, thus creating enough space for the large oocytes to pass the narrow uterus externus. The males of all investigated species have apophyses on their chelicerae. At least in B. acuminata and A. unicornis, where females have paired grooves on the preanal plate, these apophyses allow males to grasp the female during copulation as described for I. lannaianum. © 2008 Wiley‐Liss, Inc.     

Cellular and body scale morphology of Heterocapsa huensis sp. nov. (Peridiniales, Dinophyceae) found in Hue, Vietnam

Cellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis , collected from Hue, Vietnam were investigated. Morphology of motile cell was observed by light, fluorescent and scanning electron microscopy, and body scale structure was examined by whole mounts of transmission electron microscopy. Cells of H. huensis were ellipsoid with a spherical nucleus located in the posterior and multiple pyrenoids located above the nucleus; this arrangement was similar to that of Heterocapsa pygmaea . Transmission electron microscopy revealed ultrastructure of the body scales consisted of a rounded triangular basal plate and three-dimensional ornaments. Structure of the basal plate resembles that of Heterocapsa illdefina ; however, the number of the peripheral spine is different from that of H. illdefina and this structure has never been reported from Heterocapsa species. A new Heterocapsa species, H. huensis Iwataki et Matsuoka sp. nov., is described based on positions of organelles and body scale ultrastructure.     

The scales of salticid spiders

The form and location of the scales of salticid spiders, as revealed by light and scanning electron microscopy, provide useful diagnostic characters for the separation of species, the assignment of species to genera, and a further understanding of the relationships between salticid genera. Partly on the basis of distinctions provided by scale structure, the new genus Platycryptus , type-species Aranea undata De Geer, 1778, is defined. Metaphidippus vitis Cockerell, 1894, is placed in the genus Sassacus Peckham, 1895, and Paromaevia michelsoni (Barnes), 1955, is returned to the genus Maevia . The placement of Eris, Hentzia, Icius, Metaphidippus, Phidippus , and Sassacus in the subfamily Dendryphantinae is substantiated; Tutelina and Zygoballus are added to this group. On the basis of common scale structure, Evarcha, Habrocestum, Menememerus, Phlegra, Platycryptus , and Sitticus are tentatively assigned to the subfamily Habrocestinae. Scales of Anasntis, Corythalia, Cosmophasis, Hyllus, Marpissa, Metacyrba, Pellenes, Plexippus, Salticus, Sarinda, and Thiodina are also described.     

Organization of the spinnerets and spigots in the orb web spider,Argiope bruennichi (Araneae: Araneidae)

Although the basic taxonomic characteristics usually remain unchanged, some spinning apparatuses undergo consistent adaptive variations. As the presence of additional protuberances known as nubbins and tartipores have caused disagreements regarding some Araneidae spiders, more detailed definitions on the cuticular structures have recently been proposed. Reflecting this definition, microstructural organization of silk spinning apparatuses in the orb web spider Argiope bruennichi were reconsidered using field emission scanning electron microscopy. Among the seven kinds of functional spigots in females, it was revealed that two types (major ampullates and pyrifoms) are located on anterior spinnerets and another five types are distributed on median (minor ampullates, tubuliforms and aciniforms) or posterior (tubuliforms, flagelliforms, aggregates and aciniforms) spinnerets, respectively. In addition to functional spigots, cuticular remnants of the nubbins and the tartipores were found on the spinning fields, but the number of tartipores on each spinneret varied among individuals based on maturity. Nevertheless, three kinds of cuticular protuberances of ampullate silk glands were clearly visible at both the anterior and median spinnerets.     

Ultrastructural observations of spermatozoa of several tetragnathid spiders with phylogenetic implications (Araneae, Tetragnathidae)

The present study reports on the ultrastructure of spermatozoa and spermatogenesis of 12 tetragnathid spiders (10 Tetragnatha species [T. boydi, T. dearmata, T. extensa, T. montana, T. nigrita, T. obtusa, T. pinicola, T. reimoseri, T. shoshone, T. striata]; Pachygnatha listeri and Metellina segmentata). All species develop typical cleistospermia with a coiled nucleus in the center and a coiled axoneme in the periphery of the cell. Remarkable differences in the sperm ultrastructure of the investigated species comprise the shape of the main sperm cell components (nucleus, acrosomal complex, implantation fossa, and centriolar complex). Within the observed Tetragnatha species, three types of sperms were characterized: T. montana-type, T. boydi-type, and T. striata-type. The highly derivative T. montana-type is characterized by the following remarkable features: an extremely elongated nucleus, shaped like a corkscrew and twisted around the axoneme (before coiling); a deep implantation fossa; a corkscrew-shaped acrosomal vacuole; after the coiling process, the nucleus is coiled five to six times in the center of the spermatozoon and the axoneme is coiled five to six times peripheral to the nucleus. The T. boydi-type hardly differs from the T. montana-type, but is remarkable due to the triangular-shaped nucleus (in cross section). The T. striata-type differs especially by a peculiar acrosomal vacuole with a long, slightly curved process and a short appendix, as well as a nucleus that describes only three loose coils around the axoneme (before coiling). The spermatozoa of Pachygnatha listeri and especially Metellina segmentata differ strikingly from the described Tetragnatha-types and are similar to more primitive araneomorph spermatozoa, such as Hypochilus pococki. The described Tetragnatha-types completely correspond with Okuma's (1988a,b, J Fac Agr Kyushu U 32:165-181, 32:183-213) classification of Tetragnatha species. Furthermore, our results suggest an early derivative systematic position of Pachygnatha within Tetragnathinae and the position of Metellina within the Tetragnathidae.     

Spectral sensitivity in jumping spiders (Araneae,Salticidae)

1. We report here a psychophysical technique for studying the spectral sensitivity of jumping spiders (family Salticidae), based on a newly discovered oculomotor reflex. 2. Our results, obtained from Maevia inclemens (Salticidae), are compatible with electrophysiological findings of retinal cells maximally sensitive in the green and ultraviolet regions of the spectrum. 3. Sensitivity to longer wavelengths (greater than 650 nm) has been controversial. In our study jumping spiders are shown to have a broad spectral sensitivity function extending from the ultraviolet (330 nm) to the deep red (700 nm).     

Diversity of grass-dwelling spiders (Arachnida: Araneae) in calcareous fens of the Coastal Lowland,Latvia

Calcareous fens have a high conservation priority in the European Union. They are very unique, very sensitive and very rare habitats in Latvia as well as in many other European countries. Because of their rarity, many organisms living in calcareous fens are nowadays considered threatened. The same is applied to spiders. Spiders have been suggested as good biodiversity indicators because they have numerous direct and indirect relationships with other organisms. Only few investigations have been carried out on fen inhabiting spiders. The knowledge of grass-dwelling spiders is especially lacking. Thus the aim of this study was to evaluate grass-dwelling spider diversity in several calcareous fens of Latvia, compare these fens and to find out the habitat features that might affect grass-layer inhabiting spiders. The research was carried out in eight calcareous fens located in the Coastal Lowland of Latvia. A total of 760 spiders from nine families and 20 species were collected with a sweep net. Two of the most abundant spider species were Dolomedes fimbriatus (Clerck, 1757) and Tibellus maritimus (Menge, 1875). Diversity indices suggested that the grass-dwelling spider community consists of few abundant species and numerous rare species. Correlation analysis as well as DCA showed that plant species diversity did not significantly affect spider species richness and diversity, although at the same time there were a lot of significant associations between spiders and individual plant species. It was shown that various spider species responded very differently to the presence of particular plant species, and thus habitat structural heterogeneity emerges to be an important factor influencing the grass-dwelling spider diversity and community structure. Correlation analysis also revealed that spider abundance was negatively affected by the vegetation height and wind speed.     

Small-scale spatial pattern of web-building spiders (Araneae) in alfalfa: relationship to disturbance from cutting, prey availability, and intraguild interactions

Understanding the development of spatial patterns in generalist predators will improve our ability to incorporate them into biological control programs. We studied the small-scale spatial patterns of spider webs in alfalfa by analyzing the relationship between web locations over distances ranging from 4 to 66 cm. Using a coordinate-based spatial statistic (O-ring) and assuming a heterogeneous distribution of suitable web sites, we analyzed the impact of cutting and changes in spider abundance on web distribution. We analyzed the influence of small-scale variation in prey availability by comparing web distributions to the pattern of sticky-trap captures of Aphididae and Diptera described by a count-based spatial statistic (SADIE). Cutting of alfalfa reduced the overall density of web-building spiders but had no immediate impact on the spatial distribution of their webs. Availability of aphids was highest before the alfalfa was cut and was clumped at a scale of 66 cm. Spider webs, however, were not clumped at any scale or date. In contrast, webs were regularly distributed at smaller distances (<20 cm) immediately before and after cutting. Because cursorial and web-building spiders were most active during this period, we hypothesize that the development of small-scale regularity in web locations was driven by intraguild interactions. Our results suggest that intraguild interactions contribute to the development of small-scale spatial patterns of spider webs in alfalfa. Variation in prey availability may have more of an influence on web distribution in crops with a different vegetation structure or if patterns are studied at larger spatial scales.     

Comparative study of the femoral organ in Zodarion spiders (Araneae: Zodariidae)

The femoral organ of Zodarion spiders has not been investigated in detail yet. In this study we describe the external and internal structure of this organ. The organ is situated at the distal tip of the femora of all the legs during all developmental stages. The size of the organ (expressed as the number of hairs) increased with the ontogenetic development of Zodarion species. The organ was confirmed to occur in both sexes of all 47 Zodarion species examined. It is possibly present in all species of this genus. The size of the organ increased with the size of the species. A comparative anatomical study was performed in juveniles and adults of both sexes of Zodarion rubidum, and females of both Z. cyrenaicum and Z. jozefienae. The femoral organ represents an exocrine gland composed of a group of secretory cells located below the epidermis. Each gland cell is connected with the leg surface by a single duct. The ducts run in intercellular spaces and specialised canal cells are lacking. The structure of the secretory cells, namely the abundance of smooth endoplasmic reticulum, suggests that the gland produces a volatile compound(s). The composition and the role of the secretion, however, remains unknown.