Genus Dysdera Research Articles

The ultrastructure of the peculiar synspermia of some Dysderidae (Araneae, Arachnida)

The present study reports on the ultrastructure features of spermatozoa and spermatogenesis of several species of Dysderidae ( Dysdera crocata, Dysdera erythrina, Dysdera ninnii, Harpactea arguta, Harpactea piligera, Dasumia taeniifera). Dysderid spiders are known to possess a peculiar sperm transfer form known as synspermia, characterized by fused spermatozoa surrounded by a secreted sheath. Until now the exact mode of formation of the synspermia is unknown. The present study demonstrates that the spermatids are connected via narrow cell bridges during the entire spermiogenesis as is usual, although in Dysderidae they do not separate at end of the spermiogenesis. Instead, they fuse completely within the testes shortly after the spermatid has coiled to get a spherical shape. The number of fusing sperm cells is different in the different observed species. The species of the genus Harpactea thus have synspermia consisting of two fused spermatozoa; whereas in the species of the genus Dysdera four sperm cells are fused and in D. taeniifera at least three spermatozoa are fused. In contrast with other known families with this peculiar form transfer of sperm, the synspermia in Dysderidae are mainly characterized by a conspicuous vesicular area which extends through the entire synspermium surrounding the cell organelles. Thus, all main cell components (e.g., nucleus, acrosomal vacuole, and axoneme) are covered by the vesicular membrane. The vesicular area seems to be functional and probably it is important during sperm activation in female genital system. Simultaneously to the extension of the vesicular area, the synspermium accumulates large amounts of glycogen. The glycogen is mainly located around the centriolar adjunct and along the axoneme accompanying the postcentriolar elongation of the nucleus. A further peculiar feature is the extremely elongated acrosomal vacuole, which seems to be synapomorphic trait for sperm cells of dysderids. Interestingly, spermatogenesis, including the fusion, exclusively occurs within the testes (in contrast to the formation of coenospermia). In the vas deferens only synspermia were found. The secreted sheath surrounding the spermatozoa is finally synthesized in the parts of the vasa deferentia, which are close to the genital opening where numerous vacuoles and microvilli are seen in the epithelial cells.

Radiation of the Spider Genus Dysdera (Araneae, Dysderidae) in the Canary Islands: Cladistic Assessment Based on Multiple Data Sets

The volcanic archipelago of the Canary Islands, 100 km off the northwestern coast of Africa, harbors 43 endemic species of the mostly circum‐Mediterranean spider genus Dysdera (Araneae, Dysderidae). This amounts to approximately one‐fourth of all known Dysdera species in an area that represents 0.1% of the range of the genus. In order to address the origin of this extraordinary number of endemic species, the phylogenetic relationships among all the endemic taxa and a sample of 27 continental species were reconstructed. A simultaneous cladistic analysis was performed on 66 morphological characters, 471 bp of the cytochrome oxidase I and 424 bp of the 16S rRNA mitochondrial genes. The preferred most parsimonious tree supports a single origin for most of the endemic species (84%), although this tree is ambiguous regarding the total number of overseas colonizations (allowing a minimum of two and a maximum of four colonization events). Our data suggest that the Canary Islands have been the source of the colonizers of some of the remaining Macaronesian archipelagoes (certainly for the Selvagem Islands and the Cape Verdes and possibly for Madeira); the Azores have been independently colonized by dysderids from the continent. The present study provides a phylogenetic framework for an exceptional case of insular species radiation, an essential tool for unraveling the factors that have promoted this amazing diversification. Species radiations in oceanic archipelagoes are excellent models for the study of speciation processes.

Radiation of the Spider Genus Dysdera (Araneae, Dysderidae) in the Canary Islands: Cladistic Assessment Based on Multiple Data Sets

The volcanic archipelago of the Canary Islands, 100 km off the northwestern coast of Africa, harbors 43 endemic species of the mostly circum-Mediterranean spider genus Dysdera (Araneae, Dysderidae). This amounts to approximately one-fourth of all known Dysdera species in an area that represents 0.1% of the range of the genus. In order to address the origin of this extraordinary number of endemic species, the phylogenetic relationships among all the endemic taxa and a sample of 27 continental species were reconstructed. A simultaneous cladistic analysis was performed on 66 morphological characters, 471 bp of the cytochrome oxidase I and 424 bp of the 16S rRNA mitochondrial genes. The preferred most parsimonious tree supports a single origin for most of the endemic species (84%), although this tree is ambiguous regarding the total number of overseas colonizations (allowing a minimum of two and a maximum of four colonization events). Our data suggest that the Canary Islands have been the source of the colonizers of some of the remaining Macaronesian archipelagoes (certainly for the Selvagem Islands and the Cape Verdes and possibly for Madeira); the Azores have been independently colonized by dysderids from the continent. The present study provides a phylogenetic framework for an exceptional case of insular species radiation, an essential tool for unraveling the factors that have promoted this amazing diversification. Species radiations in oceanic archipelagoes are excellent models for the study of speciation processes.

SYSTEMATICS OF THE GENUS DYSDERA (ARANEAE, DYSDERIDAE) IN THE EASTERN CANARY ISLANDS

Abstract The circum-Mediterranean spider genus Dysdera has undergone an outsanding species radiation in the volcanic archipelago of the Canary Islands. The present study deals with the endemic species that inhabit the older and ecologically distinct islands of Fuerteventura, Lanzarote and their nearby islets. A new species, Dysdera sanborondon, is described. The male of D. spinidorsum Wunderlich 1991, is described for the first time. Five species are redescribed: D. alegranzaensis Wunderlich 1991; D. lancerotensis Simon 1907; D. longa Wunderlich 1991; D. nesiotes Simon 1907, and D. spinidorsum Wunderlich 1991. The species D. liostethus Simon 1907 is proposed to be a senior synonym of D. clavisetae Wunderlich 1991 and its presence in the eastern islands is considered to be doubtful. A neotype is designated for D. nesiotes. The distribution of D. alegranzaensis is extended to Lanzarote and the other northern islets. Dysdera nesiotes is reported for the first time in the eastern Canaries. Morphological affin...

Radiation of the genus Dysdera (Araneae, Haplogynae, Dysderidae) in the Canary Islands: The western islands

The spider genus Dysdera has undergone an extraordinary species radiation in the Canary Islands. As a first step towards the recovery of the endemic species phylogeny and the study of the evolutionary processes underlying its diversification, an exhaustive taxonomical work is required. The present paper deals with the endemic species that inhabit the western Canaries: La Gomera, La Palma and El Hierro. Four new species are described: Dysdera enghoffi sp. n., D. hirguan sp. n., D. orahan sp. n. and D. ramblae sp. n. Three new synonymies are reported: D. palmensis Schmidt, 1982 =D. crocota Koch, 1839, D. multipilosa Wunderlich, 1991 =D. levipes Wunderlich, 1987 and D. silvatica Schmidt, 1981 =D. rugichelis Simon, 1907. Four species are redescribed: D. calderensis Wunderlich, 1991 D. clavisetae Wunderlich, 1991 D. levipes Wunderlich, 1987 and D. rugichelis Simon, 1907 for which a neotype is designated. The presence on the western islands of the formerly described species D. insulana Simon, 1883, D. macra Simon, 1883 and D. nesiotes Simon, 1907 are considered to be doubtful. The citation of D. cribellata Simon, 1883 in La Palma (Simon, 1907) was based on a mis‐identification. The species D. gomerensis Strand, 1911 is designated as a nomen dubium. Morphological affinities as well as ecology and distribution of the species are discussed.

Spider Genus Dysdera (Araneae, Dysderidae)

THE scientific study of spiders has remained peculiarly neglected. In particular the field of systematics, until recently, has relied almost exclusively on the morphological species concept of the nineteenth century. Systematic difficulties have in turn discouraged research in other branches of spider biology. This communication summarizes an investigation into the spider genus Dysdera (Dysderidae), undertaken to strengthen the taxonomic foundations of a difficult but phylogenetically important group.

A Contribution to the Biology of the British Spiders belonging to the Genus Dysdera

The genus Dysdera comprises approximately eighty species, of which the great majority are Western European or Mediterranean in distribution. This paper is one of a series resulting from an investigation into some of the basic problems of Dysdera taxonomy (see Cooke 1965a for a general account) and summarises our present knowledge of the biology of the group. The main topics discussed are the prey, predators and parasites of Dysdera, and various aspects of the sexual biology. Under the latter heading are included sections on courtship, copulation, seasonal activity and egg laying. An account is also given of interspecific matings, which although never occurring in wild populations, may occasionally be induced in laboratory-reared individuals. The eggs resulting from such mating are infertile. Pe3ioMe JaHnlbie no 6uoioeuu 6pumancKux naYKO6 U3poda Dysdera. Pogp Dysdera BKJIKoaeT OKOJO 80 BH4,OB, 6011b]lUHHCTBO H3 KOTOpbIX pacnpOCTpaHeHbI B 3anaJRHof4 EBpone H Ha no6epewxbe CpeAH3eMHoro MOpSI. HaCTOslluaA CTaTbh COqepX4HT aaHHbIe no 6HollorHH Dysdera. noJIyqeHHbIe npH TaKcoHOMHWICKHX HCCJieaOBaHHAX npeaCTaBHTeJIeft 3TO0 rpynnmI (OCHOBHas CTaTb5 Cooke, 1965). B CTaTbe npHBOAITCq qaHHbIe o6 o6-beKTax HHTaHH5I H eCTeCTBeHHbIX sparax nayKoB, o6Cy)KgaalOTCA pa3JIHlHbiTe aCfleKTbI 6HoJIornH pa3MHOweHCHH Dysdera, a HMeHHO, 6paqHinIe uirpii, oco6eHHOCTH CrIapHBaHHAT, ce3OHHaS aKTHBHOCTb R OTKJIiaKa SIHi. YaejieHOB HHMaHIe Bonpocam Me)]KBHJOBOrO cKpeIIUHBaHKA, KOTOpOe, XOTA H He BCTpetiaeTCA B npHpoge, HO MO)KeT Ha6mno0aTbCH y nayKoB, coxaepxaIIHxcs B JIa6opaTOpHbIX yCJIOBH4AX. 5Aifia, OTJIOxKeHHbIe B pe3yJlbTaTe TaKOrO CiiapHBaHH$T He)KH3HecHoco6HbI. Manuscript accepted 15 May 1965 OIKOS 16, 1-2 (1965) This content downloaded from 207.46.13.118 on Sun, 11 Sep 2016 06:03:50 UTC All use subject to http://about.jstor.org/terms Biology of British Dysdera 21