Stanislav Korenko

A parasitoid wasp induces overwintering behaviour in its spider host

Parasites and parasitoids control behaviors of their hosts. However, the origin of the behavior evoked by the parasitic organism has been rarely identified. It is also not known whether the manipulation is universal or host-specific. Polysphinctine wasps, koinobiont ectoparasitoids of several spider species that manipulate host web-spinning activity for their own protection during pupation, provide an ideal system to reveal the origin of the evoked behavior. Larva of Zatypota percontatoria performed species-specific manipulation of theridiid spiders, Neottiura bimaculata and Theridion varians, shortly before pupation. Parasitized N. bimaculata produced a dense web, whereas parasitized T. varians built a cupola-like structure. The larva pupated inside of either the dense web or the cupola-like structure. We discovered that unparasitized N. bimaculata produce an analogous dense web around their eggsacs and for themselves during winter, while T. varians construct an analogous ‘cupola’ only for overwintering. We induced analogous manipulation in unparasitized hosts by altering ambient conditions. We discovered that the behavior evoked by larvae in two hosts was functionally similar. The larva evoked protective behaviors that occur in unparasitized hosts only during specific life-history periods.

David and Goliath: potent venom of an ant-eating spider (Araneae) enables capture of a giant prey

It is rare to find a true predator that repeatedly and routinely kills prey larger than itself. A solitary specialised ant-eating spider of the genus Zodarion can capture a relatively giant prey. We studied the trophic niche of this spider species and investigated its adaptations (behavioural and venomic) that are used to capture ants. We found that the spider captures mainly polymorphic Messor arenarius ants. Adult female spiders captured large morphs while tiny juveniles captured smaller morphs, yet in both cases ants were giant in comparison with spider size. All specimens used an effective prey capture strategy that protected them from ant retaliation. Juvenile and adult spiders were able to paralyse their prey using a single bite. The venom glands of adults were more than 50 times larger than those of juvenile spiders, but the paralysis latency of juveniles was 1.5 times longer. This suggests that this spider species possesses very potent venom already at the juvenile stage. Comparison of the venom composition between juvenile and adult spiders did not reveal significant differences. We discovered here that specialised capture combined with very effective venom enables the capture of giant prey.

Parasitoid genus-specific manipulation of orb-web host spiders (Araneae, Araneidae)

Araneid spiders of genus Araniella are attacked by three polysphinctine parsitoid wasps Polysphincta boopsTschek, P. tuberose (Gravenhorst), and Sinarachna pallipes (Holmgren). In the present study, the trophic niche of sympatrically occurring parasitoids and the host manipulation they induced were studied. The aim was to identify whether the variation in host response to manipulation is as a result of differences among parasitoids or among host species. It was found that final instar larva forced the spider host to build a three‐dimensional (3D) ‘cocoon web’ to protect the parasitoid during pupation. The behaviour of parasitoid larva and the induced modification of the web architecture differed between wasps of genus Polysphincta and Sinarachna but not among three spider species. The larvae of genus Polysphincta forced the spider host to build the ‘cocoon web’ with a high thread density within which the pupa was positioned horizontally. The larvae of Sinarachna forced the spider host to build web with sparse threads and the pupa was positioned vertically in the middle of the ‘cocoon web’. There seems to be an investment trade‐off in parasitoid wasps: some species manipulate the host to build a dense protective web, while pupating in a sparse cocoon, whereas others make the spider produce a sparse web but build a dense pupa wall.

Predation activity of two winter-active spiders (Araneae:Anyphaenidae, Philodromidae)

Anyphaena accentuata and Philodromus spp. are cold adapted and winter-active spider species. Their predation activity was investigated at constant temperatures between -4 and 30°C. The lower temperature threshold for Anyphaena was -3.7°C, while that of Philodromus was -1.2°C. At 1°C the latency to capture and prey consumption was significantly shorter in Anyphaena than in Philodromus. The capture rate increased with temperature and was maximal at 15°C in Anyphaena and at 30°C in Philodromus. At 30°C, the latency to the capture was significantly shorter in Philodromus than in Anyphaena whose mortality significantly increased.

Manipulation of araneid spider web architecture by the polysphinctine parasitoid Zatypota picticollis (Hymenoptera: Ichneumonidae: Pimplinae)

We found that the koinobiont ectoparasitoid wasp Zatypota picticollis is exclusively associated with three orb weaving spiders Cyclosa conica, Mangora acalypha and Zilla diodia from the family Araneidae. Under the influence of the parasitoids final instar larva the spiders built a specific web architecture, which differed considerably from the capturing orb web. Manipulated webs of C. conica and M. acalypha lacked the spiral, stabilimentum and central hub, and the radials were reduced in number. The manipulated web of Z. diodia consisted of one strong horizontally oriented thread.

Phenotypic integration in a series of trophic traits: tracing the evolution of myrmecophagy in spiders (Araneae)

Several hypotheses have been put forward to explain the evolution of prey specificity (stenophagy). Yet little light has so far been shed on the process of evolution of stenophagy in carnivorous predators. We performed a detailed analysis of a variety of trophic adaptations in one species. Our aim was to determine whether a specific form of stenophagy, myrmecophagy, has evolved from euryphagy via parallel changes in several traits from pre-existing characters. For that purpose, we studied the trophic niche and morphological, behavioural, venomic and physiological adaptations in a euryphagous spider, Selamia reticulata. It is a species that is branching off earlier in phylogeny than stenophagous ant-eating spiders of the genus Zodarion (both Zodariidae). The natural diet was wide and included ants. Laboratory feeding trials revealed versatile prey capture strategies that are effective on ants and other prey types. The performance of spiders on two different diets - ants only and mixed insects - failed to reveal differences in most fitness components (survival and developmental rate). However, the weight increase was significantly higher in spiders on the mixed diet. As a result, females on a mixed diet had higher fecundity and oviposited earlier. No differences were found in incubation period, hatching success or spiderling size. S. reticulata possesses a more diverse venom composition than Zodarion. Its venom is more effective for the immobilisation of beetle larvae than of ants. Comparative analysis of morphological traits related to myrmecophagy in the family Zodariidae revealed that their apomorphic states appeared gradually along the phylogeny to derived prey-specialised genera. Our results suggest that myrmecophagy has evolved gradually from the ancestral euryphagous strategy by integrating a series of trophic traits.

Modification of Tetragnatha Montana (Araneae, Tetragnathidae) Web Architecture Induced by Larva of the Parasitoid Acrodactyla Quadrisculpta (Hymenoptera, Ichneumonidae, Polysphincta Genus-Group)

BackgroundThe polysphinctine wasp, Acrodactyla quadrisculpta, is a koinobiont ecto-parasitoid of spiders and is narrowly associated with the biology of its spider hosts. The larva, attached to the dorsal side of the abdomen, develops while the spider continues foraging. Shortly before pupation, the parasitoid larva manipulates the web-building activity of the host in order to construct a safe shelter against natural elements and predators during parasitoid pupation.ResultsA. quadrisculpta was associated exclusively with the orb web weaving spiders Tetragnatha montana, with a parasitism incidence of 19%. The manipulated spider constructed a unique cocoon web that provided strong mechanical support for the parasitoid’s pupal cocoon. The cocoon web consisted of one highly reinforced main thread, tensioned in 60% of cases by a reinforced side thread. The wasp cocoon, square in cross-section, was fastened along its length to the main cocoon thread.ConclusionsThe wasp A. quadrisculpta was exclusively associated with an orb-weaving spider T. montana in the family Tetragnathidae. The alteration of the web architecture of T. montana induced by the larva A. quadrisculpta was unique and species specific.

OGCODES FUMATUS (DIPTERA: ACROCERIDAE) REARED FROM PHILODROMUS CESPITUM (ARANEAE: PHILODROMIDAE), AND FIRST EVIDENCE OF WOLBACHIA ALPHAPROTEOBACTERIA IN ACROCERIDAE

Abstract. A first rearing record of the small-headed fly Ogcodes fumatus (Erichson, 1846) from the running crab spider Philodromus cespitum (Walckenaer, 1802) is reported. Aberrant web spinning activity of the host spider is documented. Molecular work comprises DNA barcoding (COI) for the host and parasitoid as well as PCR assays (16S rRNA, wsp) detecting the presence of at least two strains of Wolbachia bacteria in O. fumatus. A Neighbour-joining search of the 16S rRNA clusters these strains within supergroup A of Wolbachia.

Hymenopteran parasitoids of the ant-eating spider Zodarion styliferum (Simon) (Araneae, Zodariidae)

Abstract Calymmochilus dispar Bouček & Andriescu (Hymenoptera, Eupelmidae) and Gelis apterus (Pontoppidan) (Hymenoptera, Ichneumonidae) are newly recorded as parasitoids of the ant-eating spider Zodarion styliferum (Simon) (Araneae, Zodariidae). The larvae of both parasitoid species fed on juvenile spiders. The final instar larva and pupa of Calymmochilus dispar and the male of Gelis apterus are described for the first time. Both species represent new distribution records for Portugal. The biology and host associations of the parasitoids are discussed.

The effect of eight common herbicides on the predatory activity of the agrobiont spider Pardosa agrestis

The impact of eight herbicides in different residual stages on the predatory activity of a potential biological control agent, the wolf spider Pardosa agrestis, was studied in the laboratory. We found that fresh wet residues of all tested herbicides negatively affected the total and cumulative predatory activity of this species. Moreover, treatment with 48-h-old residues of the glufosinate ammonium herbicide Basta induced a significant increase in predatory activity in P. agrestis, presumably as a consequence of hormesis. These results imply that the natural pest control provided by the agrobiont spider P.agrestis can be weakened by the application of the studied herbicides. On the basis of our results, we suggest that sublethal effects on beneficial organisms should be considered in the planning of weed management of agroecosystems and should not be omitted from the herbicide registration process.