Leonor Ceballos: ECOSUR, AP 36, Tapachula, Chiapas, México
Yann Hénaut: ECOSUR, AP 36, Tapachula, Chiapas, México. E-mail: firstname.lastname@example.org
Luc Legal: LADYBIO - CNRS/UPS,118, route de Narbonne - bât. 4R3, 31062 Toulouse cedex 4 – France
ABSTRACT. Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. Nocturnal spiders, however, face different conditions due to the type of prey found at night. A field study was conducted to observe the activity of adult females of Eriophora edax in their natural environment, and to analyze their predation efficiency and web retention properties. Most of the spiders were observed around sunset, which suggests that E. edax tends to build webs in the early evening. In order to evaluate the predation efficiency of E. edax we compared its behavior and web retention properties with the behavior of a diurnal orb-weaving spider, Verrucosa arenata. Two prey types, a diurnal Hymenoptera and a nocturnal Lepidoptera, were selected and presented to the spiders, to record approach time and prey capture time. The results showed that E. edax spent more time to capture Hymenoptera than to capture Lepidoptera. During the experiments of web prey retention time, Hymenoptera consistently showed greater tumbling than Lepidoptera, but the total retention time was the same for both prey types. Our results showed that E.edaxforages strictly at night and, in terms of prey capture and web retention, was more efficient when preying on Lepidoptera.
THE WASP SPIDER ARGIOPE BRUENNICHI (ARACHNIDA, ARANEIDAE): BALLOONING IS NOT AN OBLIGATE LIFE HISTORY PHASE
André Walter, Peter Bliss1 and Robin F.A. Moritz: Institut für Zoologie, Martin-Luther-Universität Halle-Wittenberg, Hoher Weg 4, D-06120 Halle (Saale), Germany. E-mail: email@example.com
ABSTRACT. Aerial dispersal(“ballooning”) of Argiope bruennichi spiderlings has been claimed to be an obligate life history trait and a prerequisite for spinning prey-capture webs. If this were true, a ballooning phase would be essential for any laboratory rearing of A. bruennichi making rearing protocols particularly elaborate. We tested the significance of ballooning for second-instar spiderlings in the laboratory and showed that the ballooning behavior is not essential for building prey-capture orb webs. Our results also give no evidence for the hypothesis that recent natural selection has changed ballooning behavior in newly founded field populations.
CAN SIMPLE EXPERIMENTAL ELECTRONICS SIMULATE THE DISPERSAL PHASE OF SPIDER BALLOONERS?
James R. Bell: Warwick HRI, Wellesbourne, Warwickshire. CV35 9EF firstname.lastname@example.org
Gabriel S. Weyman: Syngenta, Jealott’s Hill International Research Centre, Bracknell, Berkshire RG42 6EY
ABSTRACT. Here we describe the structure of a fall speed chamber designed to measure, with low experimental error, the terminal velocities (fall speeds) of spiders of known weight and a given length of silk. We also describe the construction of a simulated individual (SI) which could later be used to estimate the distance travelled by ballooning spiders in the field. Our data and analysis suggest that Oedothorax spp. (Linyphiidae) and Pachygnatha degeeri (Tetragnathidae) individuals have fall speeds that can be described by their silk length and mass. Of the observed deviance in the fall speeds, 73.7% could be explained by a GLM model common to both species groups. Overlaying the SI fall speed data on this GLM surface suggests that the SIs have similar fall speed behaviors to spiders. However, further estimation is necessary before SIs could be considered valid models for evaluating spider ballooning distances.
Nocturnal navigation in Leucorchestris arenicola (Araneae, sparassidae)
Thomas Nørgaard1: Department of Zoology, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich, Switzerland. E-mail: email@example.com
Abstract.When the males of the Namib Desert spider Leucorchestris arenicola (Araneae, Sparassidae)reach the adult stage they undertake long nocturnal searches for females. From these searches they return to their home burrow often in a straight line only retracing a fraction of their outward path if at all. Distances of 40 m and 13 m are conservative estimates of the mean round trip length and maximum distance from the burrow. Returning to the starting point of a round trip of such length is theoretically only possible if the navigator uses external cues for positional reference. The possible involvement of a range of external cues in the male L. arenicola was investigated. The direction of gravity, the sun, polarized sunlight, olfaction, constant wind direction and vibrational beacons are ruled out or deemed unlikely to be involved in the spiders’ homing.
THE SMALL JUVENILES OF EVARCHA CULICIVORA, A MOSQUITO-EATING JUMPING SPIDER
Ximena J. Nelson1,2Robert R. Jackson2,3 and Godfrey Sune3
2School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
3International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya.
ABSTRACT. The prey-capture behavior of the juveniles of Evarcha culicivora, an East African mosquito-eating jumping spider, was investigated in the laboratory using living prey and using dead, motionless lures made from two mosquito species, Anophelesgambiaesenu stricta and Culex quinquefasciatus. Having tested individuals of E. culicivora that had no prior experience with mosquitoes (rearing diet: only chaoborid and chironomid midges), our findings imply that the small, but not the large, individuals of E. culicivora have an innate predisposition to adopt Anopheles-specific prey-capture behavior. Findings from lure tests implicate posture as a primary cue by which the small juveniles of E. culicivora identify Anopheles. Each individual of E. culicivorawas presented with two lures, one in the posture typical of Anopheles and the other in the posture typical of Culex. Small, but not large, juveniles of E. culicivora often responded to Anopheles mounted in the Anopheles posture and Culex mounted in the Anopheles posture by taking a route or a detour to the prey which enabled the salticid to approach the lure from behind. However, detours were not routine for small or for large individuals of E. culicivora when the lure, whether made from Anopheles or Culex, was in the Culex posture. When tested with live mosquitoes, small juveniles of E. culicivora were more effective at capturing Anopheles than Culex. Large juveniles were more effective than small E. culicivora juveniles at capturing Culex, but large and small juveniles had similar success at capturing Anopheles.
EGG SAC STRUCTURE OF ZYGIELLA X-NOTATA (ARACHNIDA, ARANEIDAE)
T. Gheysens1, L. Beladjal1, K. Gellynck2, E. Van Nimmen2, L. Van Langenhove2 & J. Mertens1
1 Ghent University, Department of Biology, Terrestrial Ecology, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium. E-mail: Tom.Gheysens@UGent.be
2Ghent University, Department of Textiles, Technologiepark 9, B-9052 Zwijnaarde, Belgium
ABSTRACT. A detailed examination of the egg sac of Zygiella x-notata (Clerck 1757) revealed its structure, composition and different fibers. All egg sacs were composed of a basic layer, an insulation layer and an outer layer. The insulation layer consisted of two layers of cylindrical (or tubuliform) fibers with different diameters and probably with different mechanical properties. Knowing the complete structure of the egg sac allows us to locate and extract the needed fibers for further research and to observe how the egg sac composition alters in relation to the habitat.
NOTES ON THE NATURAL HISTORY OF A TRAPDOOR SPIDER
ANCYLOTRYPA SIMON (ARANEAE, CYRTAUCHENIIDAE) THAT CONSTRUCTS A SPHERICAL BURROW PLUG
Astri Leroy and John Leroy: PO Box 390, RUIMSIG, 1732, South Africa. E-mail: firstname.lastname@example.org
ABSTRACT. Burrows of an unidentified species of Ancylotrypa Simon from the floodplain of the Nyl River in Limpopo Province, South Africa are described. In addition to constructing a thin trapdoor, members of this species construct a hard, spherical plug or marble from soil particles held together with silk. Burrow structure, the plug and associated behavior are described for the first time.
THE SPERMATOZOA OF THE ONE-PALPED SPIDER TIDARREN ARGO (ARANEAE, THERIDIIDAE)
Peter Michalik1, Barbara Knoflach2, Konrad Thaler2, Gerd Alberti1 1Zoologisches Institut und Museum, Ernst-Moritz-Arndt-Universität, J.-S.-Bach-Straße11/12, D-17489 Greifswald, Germany 2Institut für Zoologie und Limnologie, LeopoldFranzens-Universität, Technikerstraße 25, A-6020 Innsbruck, Austria ABSTRACT. The species of the genus Tidarren are known for their one-palped males and outstanding copulatory behavior. In our ultrastructural observations of T. argo Knoflach & van Harten 2001, we show that this species possesses highly specific spermatozoa which differ from those found in other spiders: The nucleus of the sperm cell is strongly elongated and characterized by a conspicuous implantation fossa. The basis of the axoneme is located close to the acrosomal complex. The axoneme starts in front of the implantation fossa which extends deeply into the postcentriolar elongation. The implantation fossa is filled with dense staining globules and granules as in other theridiid species. Apart from these peculiarities, in T. argo the proximal centriole is located extraordinarily far away from the distal one. The encapsulated cleistospermia are surrounded by a thin secretion sheath. Remarkably, mature spermatozoa are not densely packed, but embedded in a copious secretion.
ON THE OCCURRENCE OF THE 9 + 0 AXONEMAL PATTERN IN THE SPERMATOZOA OF SHEETWEB SPIDERS (LINYPHIIDAE, ARANEAE)
Peter Michalik and Gerd Alberti: Zoologisches Institut und Museum, Ernst-Moritz-Arndt-Universität, J.-S.-Bach-Straße 11/12, D-17489 Greifswald, Germany. E-mail: email@example.com
ABSTRACT. In general, flagella and cilia of eukaryotes show an axoneme composed of a 9 + 2 microtubular pattern. However, the axoneme of spider spermatozoa is characterized by an exceptional 9 + 3 microtubular pattern, which is known as a synapomorphy of the Megoperculata (Amblypygi, Uropygi and Araneae). In contrast to all other observed spiders, the axoneme of the linyphiid spider Linyphia triangularis, was shown to lack the central microtubules thus representing a 9 + 0 axoneme. In the present study, we investigated the spermatozoa from several linyphiid species of different genera in order to show whether this peculiar pattern also occurs in other linyphiid spiders. Interestingly, in all observed species (Neriene clathrata, N. peltata, Linyphia hortensis, Lepthyphantes sp., Oedothorax gibbosus, Gongylidium rufipes and Drapetisca socialis) we found the 9 + 0 microtubular pattern in the axoneme. Since this study, although considering still a very limited number of species, includes species from Linyphiinae (Linyphiini and Micronetini) and Erigoninae it seems likely that this pattern is an autapomorphy of Linyphiidae.
Evidence for directional selection on male abdomen size in Mecolaesthus longissimus Simon (Araneae, Pholcidae)
Bernhard A. Huber: Zoological Research Institute and Museum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany, E-mail: firstname.lastname@example.org Abstract. Abdomens of male Mecolaesthus longissimus Simon 1893 are on average more than twice as long as in females, their length is highly variable, and they show extremely steep allometric values when scaled on body size (OLS, b = 2.64). Males cohabit with females, and they likely fight to defend this position as other pholcid spiders do. Male legs, which are usually used in pholcid male-male fights, do not show the usual high allometric values but a very low value (OLS, b = 0.37). Collectively, this lends support to the idea that M. longissimus males do not use their legs in fights and that male abdomens have assumed a role in male-male fights. However, behavioral data are missing and sexual selection by female choice or inter-male display might be involved. A large sample of data from taxonomic revisions is used to document that across pholcids, males consistently have longer tibiae 1 (and probably legs in general) than females. Several possible reasons have been suggested to account for longer male than female legs in various spider groups, but the pattern in pholcids remains to be explained.
Aino Hvam & Søren Toft: Department of Ecology & Genetics, University of Aarhus, Denmark, Bldg. 135 DK-8000 Århus C, Denmark.
ABSTRACT. Information on the value of various food types for harvestmen is sparse. The aim of this study was, therefore, to clarify the quality of six different food types to a harvestman. Survival, growth and development were used as measures of fitness in a laboratory experiment. Recently hatched Oligolophus tridens were fed the following experimental diets until maturity: Drosophila melanogaster (Diptera), entomobryid Collembola (Tomocerus bidentatus/Sinella curviseta), Folsomia candida (Collembola), Sitobion avenae (Aphidoidea), Rhopalosiphum padi (Aphidoidea), and a mixed diet containing the five prey types. Survival and growth rate were high on the D. melanogaster and entomobryid diets, and low on the F. candida, S. avenae and R. padi diets. The mixed diet caused a high early mortality, later a good survival and a high growth rate. The majority of harvestmen on the D. melanogaster and entomobryid diets matured. None of the harvestmen fed pure aphid diets developed beyond the fourth instar, and only few from the F. candida diet matured. Overall, the diets separate in three levels: D. melanogaster and the entomobryid diet were high-quality, the mixed diet was intermediate, and the two aphid diets and F. candida diet were low-quality. In general, the quality ranking agrees with that of other generalist predators, though there are differences in details.
CHROMOSOMAL DATA OF TWO PHOLCIDS (ARANEAE, HAPLOGYNAE): A NEW DIPLOID NUMBER AND THE FIRST CYTOGENETICAL RECORD
FOR THE NEW WORLD CLADE
Douglas de Araujo1, Antonio Domingos Brescovit2, Cristina Anne Rheims2,3 and Doralice Maria Cella1
1 Universidade Estadual Paulista - UNESP, Instituto de Biociências, Departamento de Biologia, Av. 24-A, 1515, CEP.: 13506-900, Bela Vista, Rio Claro, SP, Brazil. E-mails: email@example.com; firstname.lastname@example.org
2 Instituto Butantan, Laboratório de Artrópodes Peçonhentos, Av. Vital Brasil, 1500, CEP.: 05530-900, São Paulo, SP, Brazil.
3 Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
ABSTRACT. Mesabolivar luteus (Keyserling 1891) and Micropholcus fauroti (Simon 1887) specimens were collected in Ubatuba and Rio Claro, both in the state of São Paulo, Brazil. Mesabolivar luteus showed 2n (♂) = 15 = 14 + X and 2n (♀) = 16 = 14 + XX in mitotic metaphases and 7II + X in diplotenic cells. During late prophase I, all bivalents presented a ring shape, evidencing two chiasmata per bivalent. In this species, some diplotenic cells appear in pairs, maybe due to specific characteristics of the intercellular bridges. The metaphases II showed n = 7 or n = 8 = 7 + X chromosomes. Micropholcus fauroti evidenced 2n (♂) = 17 = 16 + X in spermatogonial metaphases and 8II+X in diplotenic cells, with only one chiasma per bivalent, contrasting with M. luteus. In both species, all chromosomes were metacentrics. The sexual chromosome X was the largest element and appeared as a univalent during meiosis I. These are the first cytogenetical data for the genera Mesabolivar and Micropholcus. Additionally, M. luteus is the first chromosomally analyzed species of the New World clade and the observed diploid number for M. fauroti had not yet been recorded in Pholcidae.
SIX STRIDULATING ORGANS ON ONE SPIDER (ARANEAE, ZODARIIDAE): IS THIS THE LIMIT?
Rudy Jocqué: Royal Museum for Central Africa, Leuvensesteenweg 13, B-3080 Tervuren, BELGIUM. E-mail: email@example.com ABSTRACT. A new type of stridulatory organ is described and figured occurring in three species of Mallinella Strand from Thailand and Singapore. In one species there are four stridulatory organs, with the ridges on femora I and II and the pegs in the shape of granulations on femora II and III. In both the other species an additional pair occurs, with ridges on femora III and pegs on femora IV. To date no more than four stridulatory organs have been recorded on a single spider. Examples of various known forms of stridulatory organs on spiders are illustrated and their significance briefly discussed.
FIRST ULTRASTRUCTURAL OBSERVATIONS ON THE TARSAL PORE ORGAN OF PSEUDOCELLUS PEARSEI AND P. BONETI (ARACHNIDA, RICINULEI)
Giovanni Talarico1, Jose G. Palacios-Vargas2, Mariano Fuentes Silva2 & Gerd Alberti1
2 Laboratorio de Ecología y Sistemática de Microartrópodos, Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, UNAM, México.
ABSTRACT. Due to their relative rareness and restricted distribution, little is known about the ultrastructure of ricinuleids. In particular, sense organs have not been the subject of electron microscopic research until now. Ricinuleids use their forelegs to explore their surroundings with tentative movements. The distal tarsomeres of legs I and II of two cavernicolous Mexican species, Pseudocellus pearsei from the Yucatán Peninsula and Pseudocellus boneti from Guerrero, were examined in this study with light microscopy, scanning (SEM) and transmission electron microscopy (TEM). A conspicuous feature of the distal tarsomeres of legs I and II is a single circular opening that extends as a deep tube-like pit into the tarsus. This pore organ is lacking in the 6-legged larvae. Comparable organs are present in Araneae, Scorpiones, Amblypygi and Anactinotrichida. The tarsal organs of the mentioned groups possess several types of sensilla (olfactory, thermo- and hygrosensitive and mechanosensitve). The pore organ is located in the distal third of the dorsal half of the tarsus. In longitudinal sections it shows a long oval shape. In cross sections it is nearly circular. The pore organ contains a large number of long, slightly curved setae. These setae are localized on the bottom and the lower two thirds of the wall of the pit and project into the lumen. The upper third of the wall is free of setae and shows folds which extend parallel to the opening. All setae inside the pit seem to be of the same type. In sections they show a complex inner structureand likely represent chemoreceptive wall pore single-walled (wp-sw) sensilla. This indicates a possible olfactory function. The pore organ is underlain by numerous gland cells which represent characteristics of unicellular “class I” gland cells.
ULTRASTRUCTURE OF MALE GENITAL SYSTEM AND SPERMATOZOA OF A MEXICAN CAMEL-SPIDER OF THE EREMOBATES PALLIPES SPECIES GROUP (ARACHNIDA, SOLIFUGAE)
Anja E. Klann1, Alfredo V. Peretti2 and Gerd Alberti1
2 CONICET - Cátedra de Diversidad Animal I, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 299, C. P. 5000, Córdoba, Argentina
ABSTRACT. The male genital system of Solifugae is divided into three different parts: a) a common genital chamber, b) the paired tubular vasa deferentia and c) the long, thin testes. On each side, the vas deferens splits into two smaller branches resulting in the thin, extremely long testes such that one individual possesses four tubular testes in total. The epithelium of a testis consists mainly of a glandular part and of a germinal part surrounded by a small layer of muscles. In Eremobates sp., within the germinal part the sperm cells are groups of a few, probably four, mature sperm cells each surrounded by thin extensions of somatic cells. These somatic cells can clearly be distinguished from the cells forming the glandular part which contain large amounts of rough endoplasmic reticulum. Once released into the narrow testicular lumen, the spermatozoa float more or less individually in a proteinaceous secretion. Earlier stages of spermatogenesis could not be detected, suggesting that spermatogenesis may occur in the subadult male (not examined in this study). In general, the sperm is rather simple, representing a round or slightly elongated cell devoid of a flagellum. The relatively small and flat acrosomal vacuole is attached to the disc-like nucleus. The acrosomal filament penetrates the nucleus and is coiled several times around it. In contrast to species of the family Ammotrechidae or Karschiidae, for which sperm cells have already been described, the sperm cells of the Mexican Eremobates sp., which belongs to the family Eremobatidae, show no tendency to form any piles or well ordered groups in the lumen of either the testes or the vasa deferentia.
TERGAL AND SEXUAL ANOMALIES IN BOTHRIURID SCORPIONS (SCORPIONES, BOTHRIURIDAE)
Camilo I. Mattoni: Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA. E-mail: firstname.lastname@example.org
ABSTRACT. New data concerning developmental anomalies observed among species of the family Bothriuridae (Scorpiones) are presented. Tergal malformations in Bothriurus coriaceus,Brachistosternus roigalsinai and Bothriurus noa are described and illustrated. Two new cases of intersexuality in scorpions, in specimens of Brachistosternus pentheri and Bothriurus araguayae, are reported and discussed.
Modeling of the stress-strain behavior of EGG SAC silk of the spider Araneus diadematus Els Van Nimmen & Kris Gellynck: Department of Textiles, Ghent University, Technologiepark 907, B-9052 Zwijnaarde, Belgium. E-mail: Els.VanNimmen@UGent.be
Tom Gheysens: Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium
Lieva Van Langenhove: Department of Textiles, Ghent University, Technologiepark 907, B-9052 Zwijnaarde, Belgium
Johan Mertens: Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium
ABSTRACT. Spider silk has attracted the attention of many scientists because of its desirable physical properties. Most of this attention has been devoted to dragline silk, a thread that has high tensile strength, high strain and ultra-low weight. To help understand structure-property relationships in spider silks, the tensile behavior of egg sac (cylindrical gland) silk of Araneus diadematus Clerck 1757 was compared with dragline (major ampullate gland) and silkworm silks. In addition, stress-strain curves of egg sac silk were simulated by a spring-dashpot model, specifically a Standard Linear Solid (SLS) model. The SLS model consists of a spring in series with a dashpot and in parallel with another spring, resulting in three unknown parameters. The average stress-strain curve of fibers from five different egg sacs could be accurately described by the model. Closer examination of the individual stress-strain curves revealed that in each egg sac two populations of fibers could be distinguished based on the parameters of the SLS model. The stress-strain curves of the two populations clearly differed in their behavior beyond the yield point and were probably derived from two different layers within the egg sac. This indicates that silks in the two layers of A. diadematus egg sacs probably have different tensile behavior.