SEXUAL SELECTION IN A WOLF SPIDER: MALE DRUMMING ACTIVITY,BODY SIZE,AND VIABILITY

Females are often believed to actively choose highly ornamented males (males with extravagant morphological signals or intense sexual display), and ornaments should be honest signals of male viability. However, this belief is relying only on some pieces of empirical evidence from birds. Our study reports active female choice on sexual display that indicates male viability in spiders. We established trials in which we studied female choice in relation to male courtship drumming activity and body size. Females chose the most actively drumming males as mating partners, but the body size of the males did not seem to be selected. Male drumming activity turned out to be a good predictor of male viability, whereas male viability was independent of male body mass. Our results suggest that by actively choosing mates according to male drumming performance, but independently of male body mass, females are preferring viable males as mates. Because Hygrolycosa rubrofasciata males do not provide obvious direct benefits to their offspring, females may gain some indirect benefits; offspring may have higher chance of survival, or the offspring may inherit the attractiveness of their father.     

安徽加马蛛雌蛛记述（蜘蛛目：卵形蛛科）

报道采自安徽黟县的安徽加马蛛雌蛛的描述,亦为该种雌蛛的首次纪录。     

Modelling Fungal (Neozygites cf. Floridana) Epizootics in Local Populations of Cassava Green Mites (Mononychellus Tanajoa)

The fungus, Neozygitis cf. floridana is parasitic on the cassava green mite, Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) in South America and may be considered for classical biological control of cassava green mites in Africa, where cassava is an important subsistence crop, cassava green mites are an imported pest and specific natural enemies are lacking. Spider mites generally have a viscous structure of local populations, a trait that would normally hamper the spread of a fungus that is transmitted by the contact of susceptible hosts with the halo of capilliconidia surrounding an infectious host. However, if infected mites search and settle to produce capilliconidia on sites where they are surrounded by susceptible mites before becoming infectious, then the conditions for maximal transmission in a viscous host population are met. Because the ratio between spider mites and the leaf area they occupy is constant, parasite-induced host searching behaviour leads to a constant per capita transmission rate. Hence, the transmission rate only depends on the number of infectious hosts. These assumptions on parasite-induced host search and constant host density lead to a simple, analytically tractable model that can be used to estimate the maximal capacity of the fungus to decimate local populations of the cassava green mite. By estimating the parameters of this model (host density, per capita transmission rate and duration of infected and infectious state) it was shown that the fungal pathogen can reduce the population growth of M. tanajoa, but cannot drive local mite populations to extinction. Only when the initial ratio of infectious to susceptible mites exceeds unity or the effective growth rate of the mite population is sufficiently reduced by other factors than the fungus (e.g. lower food quality of the host plant, dislodgement and death by rain and wind and predation), will the fungal pathogen be capable of decimating the cassava green mite population. Under realistic field conditions, where all of these growth-reducing factors are likely to operate, there may well be room for effective control by the parasitic fungus. This revised version was published online in November 2006 with corrections to the Cover Date.     

Photoperiodic induction of diapause in the spider mite Tetranychus urticae: qualitative or quantitative time measurement?

Abstract. Insects and mites may measure photoperiods eitfier by classifying them as long or short relative to a critical value (qualitative time measurement) or by using the absolute value (quantitative time measurement). The spider mite Tetranychus urticae is thought to use a qualitative mechanism of time measurement. In this paper we present the results of experiments with an inbred line of the spider mite (to keep genetic variation in photoperiodic responses small), to test whether quantitative aspects also play a role. Differences in diapause incidence in different long-night photoperiods at different temperatures may be an indication of quantitative responses to photoperiod. The effect of temperature on the photoperiodic response curve was studied at 16^oC, 19^oC and 22^oC. The response curves appeared to be similar at 16^oC and 19^oC, with a critical nightlength between 10 and 11 h. At 22^oC, diapause induction was less than 100% in all long-night regimens and die critical nightlength had shifted to 12 h. Maximum diapause induction (93%) occurred in a light-dark cycle with a 16 h dark phase (LD 8:16 h). Diapause induction was lowest in long-night photoperiods with dark phases of 20 h and longer. The number of light-dark cycles needed for 50% diapause induction at 19^oC varied. between 12.1 and 14.7 for LD 6:18 h, between 10.9 and 12.5 for LD 8:16 h, between 10.6 and 11.6 for LD 10:14 h, and between 10.1 and 10.7 for LD 12:12 h. Independent of die light-dark regimen, diapause induction took place in some individuals after receiving 8 cycles and virtually all individuals entered diapause after 16 cycles. No effect was found of the photoperiodic treatment during prediapause development (LD 6:18 h, LD 8:16 h, LD 10:14 h, LD 12:12 h) on diapause duration. The average diapause duration at LD 10:14 h and 19^oC was 61 days over all four treatments. We explained the results by hypothesising that nightlengths are assessed qualitatively and mat the photoperiodic clock operates more accurately near the critical nightlength.     

Screening of Necrotizing Spiders in Korea Using Nonradioactive Sphingomyelinase Assay (I) Wandering Spiders

There are now more than 40,000 identified spider species in the world, and considered about 100 species as actually dangerous to human. Spider bites cause a range of symptoms from simple swellings to disfiguring necrotic lesions, and occasionally death. While spider bites are not a major medical problem in Korea, it would be of great value to know which species of spiders pose a threat to human health. A middle molecular weight protein, sphingomyelinase D, has been identified in the venom of the brown recluse spider and strong evidence suggests that they have a major role in spider bite necrosis. For the identification of necrotizing species, we have investigated using recently developed non‐radioactive assay of sphingomyelinase for rapidly screening the necrotizing venoms. Here, we demonstrate the fetal toxicity of total 57 species (32 genera, 9 families) of the wandering spiders among 622 identified spider species in Korea. It has been revealed that two species of the Thomisidae spider, Ozyptila nongae (0.2467) and Diaea subdola (0.2020) have the strongest sphingomyelinase activities among themselves. In addition one species of the family Pisauridae, Dolomedes sulfureus (0.2341) has also relatively higher value comparing to other wandering spiders. However comparing to that of the brown recluse spider, Loxosceles reclusa (1.814) in North America the necrotizing activities of these Korean wandering species are still very low state, so there seems to be little possibilities to create serious medical problems by the necrotizing arachnidism in Korean peninsula.     

Multi‐color FISH facilitates analysis of cell‐type diversification and developmental gene regulation in the Parasteatoda spider embryo

The simultaneous and quantitative analysis of the expression of multiple genes helps to shed light on gene regulatory networks. We established a method for multi‐color fluorescence in situ hybridization (mFISH) for the analysis of cell‐type diversification and developmental gene regulation in the embryo of the spider Parasteatoda tepidariorum. This mFISH technique allowed quadruple staining using four types of labels for RNA probes, digoxigenin, fluorescein, biotin, and dinitrophenyl, together with different fluorescent tyramides. To validate the usability of mFISH, we conducted four experiments. First, we distinguished similar gene expression patterns with mFISH, which showed overlaps and differences in the expression domains of anterior patterning hedgehog (hh), orthodenticle (otd), and labial genes at a cellular resolution. Second, we used mFISH to identify early cell types that are internalized on the anterior side. We found that fork head‐positive cells were subdivided into two cell types, 012_A08‐positive endoderm cells and twist‐positive mesoderm cells. Third, we quantified the ratio of expression levels of the odd‐paired (opa) gene in the chelicera and pedipalp segments based on the intensity of mFISH signals. Finally, we combined mFISH with embryonic RNA interference. It was possible to identify opa knockdown cell clones and detect the specific reduction of opa and the upregulation of otd and hh expression levels in the same cell clone that formed in the head region. This study proposes that mFISH is a powerful tool for the cell‐level analysis of gene regulation and quantification in the spider model.     

Prey Luring Coloration of A Nocturnal Semi‐Aquatic Predator

Body coloration serves a variety of purposes in animals. Diurnal and nocturnal predators such as spiders may use their body coloration to lure prey. We predicted here that the white patches on the forelegs on females of the nocturnal semi‐aquatic spider Dolomedes raptor lure prey, explaining why they are primarily displayed when the spider forages along the water edge. To test our prediction, we developed a color vision model assessing whether the patches are visible to pygmy grasshoppers, the spider's primary prey. We conducted a field experiment using cardboard dummies that resemble D. raptor in size, shape, and color, but with half of them lacking leg patches, and we staged interactions between pygmy grasshoppers and D. raptor with and without leg patches in a greenhouse. We found the white patches to be visible to grasshoppers. The dummies with white patches attracted more grasshopper prey than the dummies without the patches. Moreover, grasshoppers were more attracted to spiders when their white patches were present. Our results supported the hypothesis that the white patches of D. raptor lure prey. Our findings, nevertheless, could not be explained as the spider's body coloration acting as a sensory trap but it should not be ruled out. More studies on a wider range of predators and prey will give more meaningful insights into the co‐evolution of predatory lures and prey sensory modalities.     

Development of species‐specific primers for rapid diagnosis of Tetranychus urticae,T. kanzawai,T. phaselus and T. truncatus (Acari: Tetranychidae)

Species diagnosis is of the utmost importance to both pest management and plant quarantine services. Because of difficulties in the morphological diagnosis of spider mites, molecular techniques are of great value to rapidly and accurately diagnose closely related species. We examined four species of genus Tetranychus (the green and red forms of T. urticae, and T. kanzawai, T. phaselus and T. truncatus), which are found in Korea and are of significance to plant quarantine services. DNA samples isolated from a single egg, larva or adult weighed 64–188 ng. We designed species‐specific primers by performing sequence alignment for 107 sequences of the ribosomal internal transcribed spacer 2 (ITS2) region, which we obtained from GenBank, and sequences generated in this study. Specific nucleotides of each species were selected for designing primers specific for each species. Each species‐specific primer pair, when used to perform PCR analyses, detected only the species from which it originated. However, a T. urticae‐specific primer pair did not discriminate between the green and red forms of this species. These species‐specific primers can be applied in practice for the rapid and accurate diagnosis of spider mite species in plant quarantine and in agricultural fields.     

Ancient hybrid origin of the eastern wolf not yet off the table: a comment on Rutledge et al. (2015)

A recent study of North American canids by Rutledge et al. (Biol. Lett. 11, 20150303 (doi:10.1098/rsbl.2015.0303)) refutes the hypothesized hybrid origin of the eastern wolf (EW) based on genomic evidence against very recent hybridization. However, the analyses do not rule out the possibility of more ancient hybridization. Claims to have resolved the evolutionary origin of the EW are therefore inappropriate. Importantly, though, we plead that uncertainty about the ancient history of the taxon should not affect current conservation policy.