Cave adaptation in the spider genus Anthrobia (Araneae, Linyphiidae, Erigoninae)

The genus Anthrobia Tellkampf, 1844 is revised and expanded to include two epigean species, Anthrobia acuminata ( Emerton, 1913 ) comb. nov., and A. whiteleyae sp. nov., and two troglobites, the type species A. monmouthia Tellkampf, 1844 , and A. coylei sp. nov. The female of A. acuminata is described for the first time. All four Anthrobia species were added to a phylogenetic analysis of erigonine genera. Analysis of this matrix results in a single most parsimonious tree (length = 915, CI = 0.23, RI = 0.58; uninformative characters excluded: length = 911, CI = 0.23), which places Anthrobia sister to Diplocentria Hull, 1911. Troglobitic Anthrobia and epigean Anthrobia are both monophyletic. In comparison to the epigean species, troglobitic Anthrobia exhibit the following putative adaptations to cave life: loss of eyes, elongation of the legs, and reduction of the tracheal system. The reliability of phylogenetic results indicating monophyly of cave Anthrobia are discussed in light of the fact that potentially cave adaptive synapomorphies support this relationship.     

Phylogenetic analysis and revision of the linyphiid spider genus Solenysa (Araneae: Linyphiidae: Erigoninae)

In this paper we carry out a taxonomic revision and phylogenetic analysis of the linyphiid spider genus Solenysa Simon, 1894. A total of 12 species is treated here, including five new species collected from China and Japan: Solenysa akihisai Tu sp. nov., Solenysa lanyuensis Tu sp. nov., Solenysa retractilis Tu sp. nov., Solenysa tianmushana Tu sp. nov. , and Solenysa yangmingshana Tu sp. nov. Solenysa circularis Gao, Zhu & Sha, 1993 is a junior synonym of Solenysa protrudens Gao, Zhu & Sha, 1993. We have assembled two different character matrices to reconstruct the phylogenetic relationships of Solenysa. In the first matrix (Matrix 1), five representative species of Solenysa were added to the morphological dataset of Miller & Hormiga to test the monophyly of the genus and its placement within Linyphiidae. The genitalic structures and somatic morphology of Solenysa were studied by means of scanning electron microscopy for the first time. To infer the species‐level phylogenetic relationships of Solenysa we produced a second matrix (Matrix 2) that includes all 12 Solenysa species and six outgroup species chosen from the results of the analysis of the first matrix. The two most parsimonious trees from the analysis of Matrix 1 support the monophyly of Solenysa and its placement within the ‘Distal Erigonines’ clade. The single most parsimonious tree resulting from the analysis of the second matrix suggests that the Solenysa clade includes four monophyletic groups, each group represented by a distinct genitalic pattern. The morphology of Solenysa, both somatic and genitalic, is highly autapomorphic. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 484–530.     

Systematics of the spider genera Mallos and Mexitlia (Araneae, Dictynidae)

This systematic study recognizes and describes 14 species of the genus Mallos O. Pickard-Cambridge, 1902 and three species of the genus Mexitlia Lehtinen, 1967. Three species of Mallos – Mallos gertschi, Mallos chamberlini and Mallos macrolirus –and one species of Mexitlia – Mexitlia altima –are newly described. Mallos ghiggi (Caporiacco, 1938) is considered a synonym of Mexitlia grandis (O. Pickard-Cambridge, 1896). Mexitlia grandis is considered the senior synonym of Mexitlia avara (Banks, 1898). Two species, Mallos jlavovittatus (Keyserling, 1880) and Mallos nigrescens (Caporiacco, 1955) are removed from Mallos. The males of Mallos kraussi Gertsch, 1946 and Mallos blandus Chamberlin and Gertsch 1958, are described for the first time. A cladistic analysis based on 26 morphological characters produced a cladogram that supports the monophyly of Mallos and the validity of Mexitlia. This cladogram presents a phylogenetic framework for considering the evolution of social behaviour in Mallos.     

Securing paternity: mating plugs in the dwarf spider Oedothorax retusus (Araneae: Erigoninae)

One of the various male strategies to prevent or impede female remating is the production of a mating plug that covers the female genital opening or remains inside of the female genital tract after mating. Such structures have been described for many species in many animal taxa; however, in most cases, we know little or nothing about their specific adaptive value. Our investigations demonstrate that females of the dwarf spider species Oedothorax retusus (Westring, 1851) (Linyphiidae, Erigoninae) exhibit a substance on one or both of her paired genital openings only after copulation. We performed double-mating trials and forced the second male to mate into the previously used or unused spermathecal duct of the female by amputating one of his paired male gonopods (pedipalps). Furthermore, to investigate whether the duration of the first mating has an effect on the size and efficiency of the mating plug, we interrupted first matings after either 1 or 3 min, categorized plug size and recorded mating behaviour of subsequent males. The amount of secretion transferred was larger in long compared to short copulations. A long first copulation successfully prevented subsequent males from mating into the used ducts, whereas mating success after short first matings was similar to matings into unused copulatory ducts of the females. The present study demonstrates that a male O. retusus can prevent a rival from transferring sperm into the same spermatheca by applying a mating plug, but only if he mates for long enough.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 574–583.     

Landscape context of sheetweb spider (Araneae: Linyphiidae) abundance in cereal fields

Aim Sheetweb spiders (Araneae: Linyphiidae, subfamily Linyphiinae) exemplify a highly mobile group of farmland arthropods with very variable abundances in crops within and between years. Despite their dominance in crops during summer, they overwinter predominantly in perennial non‐crop habitats, and their densities in crops during spring should therefore depend on the amount of favourable overwintering habitat in the surrounding landscape. We tested the effect of landscape composition on sheetweb spider abundance with special attention to the range of their aerial dispersal and weather dependence. Location The study was carried out in 18 non‐overlapping landscape sectors of 3 km radius around the city of Göttingen (Germany), forming a gradient from structurally simple, with up to 85% arable land, to structurally complex, with high percentages of grassland and other non‐crop habitats. Methods Sheetweb spider abundances in winter wheat fields were sampled during May and June 2001–2003 with a distance method. They were related to landscape composition at 11 spatial scales between 95 and 3000 m radius around the study sites. Results In 2001 and 2003, spider abundances were enhanced by high percentages of non‐crop habitats in 1–3 km circumference (e.g. from 18 to 130 m^?2 in late May 2001), and multiplied during consecutive sampling periods (e.g. from on average 36 to 131 m^?2 between mid‐May and late June 2001). Spider abundances were constantly low and unrelated to the landscape context in 2002. In that year, immigration appeared to be inhibited by factors connected to exceptionally high amounts of rain during May. Main conclusions Sheetweb spiders responded to landscape composition up to several kilometres away and the effects varied between years, demonstrating the need to consider large space and time‐scales to understand their population dynamics. Semi‐natural habitats should be preserved to enhance these important natural enemies of crop pests in agricultural landscapes.     

Multiple web-borne pheromones in a spider Frontinella pyramitela (Araneae: Linyphiidae)

The bowl-and-doily spider, Frontinella pyramitela, is a common inhabitant of low vegetation throughout most of temperate North America. All instars build concave-upward, bowl-shaped, nonviscid webs supported above and below by meshworks of silk. Previous studies of this species have revealed that chemical(s) on the silk of adult females elicit both courtship behaviour and positive geotaxis from adult males that contact the silk. This study demonstrates (1) that two different contact pheromones are responsible for the dual action of the silk of adult females and (2) that the webs of different age and sex classes of bowl-and-doily spiders (including the webs of adult males) contain functionally different mixtures of the two pheromones.     

Clade stability and the addition of data: A case study from erigonine spiders (Araneae: Linyphiidae, Erigoninae)

This study presents a new phylogeny of erigonine spiders with emphasis on genera from the Neotropics. Thirty‐nine exemplar taxa representing mostly Neotropical genera were added to a global sample of 31 erigonine and 12 outgroup exemplar taxa analyzed in a previous study. These 82 taxa were coded for 176 (172 informative) mostly morphological characters. Eighty‐one characters were identical to or modified from the 73 (67 informative) characters included in a previous study; the remaining 95 characters are new. The complete data set includes 70 erigonine exemplars representing 65 genera, seven nonerigonine linyphiid exemplars, and five exemplars representing four araneoid families in the outgroup. Cladistic analysis resulted in a single most parsimonious tree (L =904, CI = 0.23, RI = 0.58; uninformative characters excluded: L = 900, CI = 0.23). This paper explores the implications of the new topology for the evolution of several characters of interest in erigonine evolution. The phylogeny implies that the desmitracheate condition is a synapomorphy of erigonines, with a reversal to the haplotracheate condition in one large clade within Erigoninae. We infer that the loss of the paracymbium in Neotropical erigonines occurred twice and may have progressed by different evolutionary pathways. Our phylogeny differs markedly from the previous cladistic hypothesis of erigonine relationships. We investigate how the addition of characters and taxa (alone and together) have altered the earlier hypothesis of erigonine phylogeny. We conclude that topological changes from the previous study to the current one are largely the result of adding and modifying characters, not adding taxa. Continuous Jackknife Function (CJF) analysis predicts that the inclusion of additional character data will continue to imply changes in the relationships among taxa in our analysis.     

Cephalic modifications in dimorphic dwarf spiders of the genus oedothorax (Erigoninae,Linyphiidae, Araneae) and their evolutionary implications

Reproductive competition among males selects for a broad variety of strategies and traits from mate guarding to nuptial food gifts. Males of many dwarf spider species possess conspicuous secondary cephalic modifications, and the few studies available suggest that these cephalic structures are connected to extensive glandular tissue. Because females were observed to contact the male head structures during mating, these traits may have evolved in the context of sexual selection. We investigated the structure, glandular equipment, and sensory equipment of the cephalic regions of several species of the dwarf spider genus Oedothorax with varying degrees of sexual dimorphism using light and electron microscopy. In one Oedothorax species, there are two male morphs that exhibit a cephalic modification (O. gibbosus gibbosus) or not (O. gibbosus tuberosus). Our study demonstrates that all males investigated produce cephalic secretions, irrespective of the morphology of their cephalic region, however, they may differ in amount of secretion and in cellular organization. In males of O. apicatus, O. gibbosus gibbosus and O. retusus the gland cells are very abundant in the area of a cephalic hump, whereas in the less conspicuous O. agrestis, and O. gibbosus tuberosus the gland cells are restricted to a small area behind the ocular region or include the ocular region as in O. fuscus. The glandular tissue consists of two gland types in O. agrestis, O. fuscus, O. gibbosus tuberosus and O. retusus and of only one type in O. apicatus and O. gibbosus gibbosus. The setae present on the head structure of all species seem to function as mechano‐ and/or chemoreceptors. The implications of our findings for the evolution of secretory head structures are discussed along with their potential for driving speciation. J. Morphol. 2011. © 2011Wiley‐Liss, Inc.     

Cephalic secretion release in the male dwarf spider Oedothorax retusus (Linyphiidae: Erigoninae): An ultrastructural analysis

Secondary sexual traits in males can extend to glandular structures that play a role during courtship and mating. In dwarf spiders (Linyphiidae, Erigoninae), glandular secondary sexual traits are particularly common. Males are characterized by cephalic modifications which produce secretions that females contact with their mouthparts during courtship and/or copulation. We used the dwarf spider Oedothorax retusus as a model species to investigate if and when the contents of the glands are released during a mating sequence and if so, if the gland reservoirs are refilled after mating. To this aim, we quantitatively compared the glandular tissue on the ultrastructural level between a) inexperienced males, b) males that performed courtship, c) males immediately after copulation, and d) males three days after mating. We assessed whether the treatment groups differed in the filling state of the conducting canals and receiving canals (reservoir regions) of the glandular units. Our study shows that courting males as well as males three days after mating did not differ significantly from control (inexperienced) males in the presence of secretions. However, males exhibited significantly less secretion immediately after mating. This strongly suggests that the main function of the secretions is gustatorial courtship and not the emission of volatile pheromones for mate attraction as was previously assumed.     

Histological study of karaurids,the oldest known (stem) urodeles

Little is known about the initial phases of lissamphibian history (before the Cretaceous), because their fossil record is quite scanty. Only the morphology of the earliest members has been investigated, although other sets of data, from bone microanatomy and histology, are known to yield valuable paleobiological information. In the present study, we provide the first histological and microanatomical data on the oldest known stem-urodeles, the karaurids, from the Middle Jurassic. Three humeri from the Upper Bathonian, Oxfordshire, referred to juvenile or subadult individuals of Marmorerpeton and to an unnamed caudate of undetermined (but obviously non-larval) ontogenetic stage, were sampled in order to shed new light on the habitat and ontogeny of these basal caudates. The great compactness of the three humeri suggests that these salamanders were aquatic. The presence of extensive amounts of calcified cartilage in the humeri greatly strengthens the case for the presence of neoteny in these taxa, a suggestion that had initially been made on the basis of a few morphological characters. This constitutes the oldest known occurrence of neoteny in lissamphibians. Finally, bone histology reveals that the growth of Marmorerpeton and the related unnamed caudate was fairly slow and cyclic, a characteristic of extant lissamphibians.     

A mass rearing method for the linyphiid spider species Erigone atra (Blackwall) (Araneae: Linyphiidae)

Abstract:  A mass rearing method for Erigone atra (Blackwall) (Araneae: Linyphiidae) allowing continuous laboratory rearing is described. Twenty 1–2-day old spiderlings were kept together in plastic boxes, which were filled with soil containing a culture of the Collembola species, Lepidocyrtus lanuginosus (Gmelin) (Entomobryidae), and serving the spiders as a continuous available prey source. Once per week vestigial-wing fruit flies of Drosophila melanogaster Meigen (Diptera: Drosophilidae) were provided as additional prey. In addition, the rearing boxes were filled with wood-wool serving spiders as points of contact for their webs. After 3–5 weeks most of the spiderlings developed to adults, which were separated individually into glass tubes filled with soil and Collembola until all of them became adult. To produce a new generation of spiders 20–40 adult/subadult spiders originating from different mass rearing boxes were brought together and kept and fed in the same way as the spiderlings. Within a few days females started to produce eggsacs. The eggsacs were transferred into glass tubes filled with a layer of moist plaster of Paris until the spiderlings hatched, which were then bred as described above. Erigone atra was bred over 12 generations within a period of 2 years. The mean rearing success (from 1 to 2-day-old spiderlings to adults) was 59.3%. Decreasing rearing success, decrease of fecundity or decrease of adult spider size were not observed. Advantages and use of the mass rearing method are discussed in relation to rearing methods for other spiders.     

The Comb-footed spider genera Theridion, Achaearanea and Anelosimus of Israel (Araneae: Theridiidae)

Israeli thendiid spiders of the genera Theridion, Achaearanea and Anelosimus have been revised. A relative richness in species is presented providing thereby updated information on the little known Mediterranean spider fauna. All type and non-type material previously described from the Middle East, deposited in several European collections has been re-examined, along with species from adjacent regions considered pertinent to the study undertaken. Altogether 21 species are recognized. Systematic, ecologic and all available zoogeographic information on taxa treated are discussed along with recent, pertaining literature. The presence of seven species formerly reported from Israel has been confirmed and the occurrence of another four species unknown hitherto from this region, has been proved. Some of these have never been adequately described or illustrated.
Ten new species are described: Theridion ochreolus, T. agaricographus, T hierwhonticus, T. jordanensis, T. negebensis, T. gekkonicus, T. dafnensis, T. vallisalinarum, T. pustiliferus and Anelosimus giladensis. The male of Theridion melanostictum is described for the first time. Keys, illustrations of diagnostic characters and records of distribution are provided for each species, all readily applicable also in adjacent countries. These may provide clues for better understanding of zoogeographic patterns of the Palearctic fauna, including those of the Old World Desert belt extending south and east of the Mediterranean region.     

Minicia marginella (Araneae: Linyphiidae), a spider new to Britain, from the Channel Tunnel site

In the summer of 1987 a project was initiated to study certain aspects of the environmental impact of tunnelling for the Channel Tunnel. The study areas were situated in East Kent between Dover and Folkestone. At one of the chosen study sites, a male and female of the linyphiid spider Minicia marginella (Wider), hitherto unknown from Britain, were taken in pitfall traps. Both sexes of the species are described and illustrated from the British material.     

A phylogenetic analysis of the genera of Lejeuneaceae (Hepaticae)

The Lejeuneaceae are the largest family of the liverworts (Hepaticae), with almost a thousand species in 91 currently accepted genera. We analysed phylogenetic relationships of 69 genera, representing all major subfamilies and tribes recognized in the family, by using 49 informative morphological characters (31 gametophytic, 18 sporophytic), one chemical character, and applying equal and successive weighting of characters and parsimony analysis. In all trees recovered, the Lejeuneaceae were monophyletic with Nipponolejeunea (subfam. Nipponolejeuneoideae) forming the basalmost lineage. The remaining genera clustered in two major groups, the monophyletic Lejeuneoideae (52 genera) and the paraphyletic Ptychanthoideae (16 genera). Within each, several multigeneric lineages corresponding in part to previously described taxa were recovered: the Acrolejeuneinae and Ptychanthinae clades in the Ptychanthoideae, and the Brachiolejeuneinae, Lejeuneeae and Tuyamaella–Cololejeunea clades in the Lejeuneoideae. Bryopteris , a genus sometimes treated as a separate family, was nested in the Ptychanthinae clade. The Tuyamaella–Cololejeunea lineage corresponded with three previously recognized subfamilies (Cololejeuneoideae, Myriocoleoideae and Tuyamaelloideae) and contained genera with neotenic features, in two subclades. These features seemed to have originated by multiple heterochronic events: single origins were detected for 'protonemal neoteny' and 'primary neoteny', whereas 'secondary neoteny' probably evolved twice. Relationships within the large Lejeuneeae clade (43 genera) remained largely unresolved, although several putative lineages were detected in majority rule trees. Additional characters such as DNA sequences may provide better phylogenetic resolution in this group.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 391–410.     

Territoriality in the Sheet-Web Spider Linyphia triangularis (Clerck) (Araneae,Linyphiidae

• 1 Das adulte L. triangularis-♂ bleibt bis zu 2 Tagen im Netz eines ♀, beträchtliche Zeit verbringt es von Netz zu Netz wandernd. Während der Zeit des gemeinsamen Netzaufenthaltes ist das ♂, ob das ♀ nun kopulationsbereit ist oder nicht, stets der dominante Teil des Paares.
• 2 Wenn mehrere ♂♂ im ♀-Netz zusammentreffen, zeigen sie Droh- und Kampfverhalten, in dem die vergrößerten Chelizeren und Klauen benutzt werden. Mehrere Stufen des Kampfverhaltens werden beschrieben und als Aggressionsanzeiger betrachtet.
• 3 Netzreduktion durch das ♂ wird als Methode zur Verhinderung von Störungen während der Kopulation betrachtet. Selektionsmechanismen, die die Evolution solchen Verhaltens begünstigen, werden diskutiert.
• 4 Die Auslösung der Netzreduktion hängt anscheinend von dem Grad der weiblichen Kopulationsbereitschaft ab.
• 5 Weibchen an der Netzperipherie können in die Netze anderer ♀♀ ein-dringen und dort Beute machen.

     

Globuli ossei in the long limb bones of Pleurodeles waltl (Amphibia,Urodela, Salamandridae)

To date, little is known about the structure of the cells and the fibrillar matrix of the globuli ossei, globular structures showing histochemical properties of an osseous tissue, sometimes found in the resorption front of the hypertrophied cartilage in many tetrapods, and easily observed in the long bones of the Urodele Pleurodeles waltl. Here, we present the results obtained from the appendicular long bones of metamorphosed juveniles and subadults using histological and histochemical methods and transmission electron microscopy. The distal part of the cone‐shaped cartilage contains a heterogeneous cell population composed of the typical “light” hypertrophic chondrocytes and scarce “dark” hypertrophic chondrocytes. The “dark” chondrocytes display ultrastructural characteristics suggesting that they probably undergo degeneration through chondroptosis. However, in the hypertrophic, calcified cartilage close to the erosion front by the marrow, several noninvaded chondrocytic lacunae retained cells that do not show any morphological characteristics of degeneration and that cannot be identified as regular chondrocytes or osteocytes. These modified chondrocytes that have lost their regular morphology, appear to be active in the terminal cartilage and synthesize collagen fibrils of a peculiar diameter intermediate between the Type I collagen found in bone and the Type II collagen characteristic of cartilage. It is suggested that the local occurrence of globuli ossei is linked to a low rate of longitudinal growth as is the case in the long bones of postmetamorphic urodeles. J. Morphol. 275:1226–1237, 2014. © 2014 Wiley Periodicals, Inc.