The influence of predator sex on chemically mediated antipredator response in the wolf spider Pardosa milvina (Araneae: Lycosidae). —Ethology 110

Abstract The wolf spider, Pardosa milvina, reduces activity in the presence of chemical cues (silk and excreta) from a larger predatory wolf spider, Hogna helluo. Hogna is sexually dimorphic in body size and males and females differ in their propensity to attack prey. Consequently, each sex may present different levels of risk to Pardosa. We measured predation risk of Pardosa in the presence of male or female Hogna. We also assessed Pardosa antipredator responses and survival in the presence or absence of previously deposited chemical cues from male or female Hogna. In the absence of predator chemical cues, Pardosa survived significantly longer in the presence of male Hogna compared with female Hogna. We then assessed Pardosa survival in the presence of chemical cues from each Hogna sex by placing Pardosa in containers previously occupied by a female Hogna, a male Hogna, or no Hogna (control). We then introduced a female Hogna into each container and measured predation latency. Pardosa survived significantly longer in the presence of female and male cues compared with the control treatment. Median survival time of Pardosa was over four times longer on substrates with female Hogna cues compared with male cues, but this difference was not statistically significant. We tested Pardosa activity levels in the presence of chemical cues from male or female Hogna. Both Hogna sexes were maintained in separate containers after which we placed an adult female Pardosa in one of the containers or a blank control container. Pardosa significantly decreased activity in the presence of chemical cues from either sex relative to the control. Activity was lowest on substrates with female Hogna cues, but not significantly lower than on substrates with male Hogna cues. Results suggest that chemical information from male or female Hogna significantly reduces Pardosa activity which results in increased survival

SHORT COMMUNICATION Proximate cues governing egg sac discrimination and recognition in the wolf spider Pardosa milvina (Araneae: Lycosidae)

Abstract. Female lycosids carry their egg sacs on their spinnerets until spiderlings emerge but spiders are occasionally found carrying shells, dirt, or other objects on their spinnerets, suggesting recognition errors can occur. We investigated some proximate cues that may influence egg sac recognition and discrimination in the wolf spider Pardosa milvina (Hentz 1844). We tested the ability of female P. milvina to discriminate among egg sacs based on size, texture, and contrast. We also tested the ability of P. milvina to discriminate between its own or a conspecific's egg sac, and the ability to discriminate between an egg sac that had just been removed and an egg sac that was removed seven days earlier. When given a choice, females significantly chose their own egg sac over plastic beads of equal mass, preferred large plastic beads equal in mass to an egg sac over small plastic beads, round over faceted beads, and showed a non-significant tendency to attach black rather than white beads of equal mass. When given a choice between two conspecific egg sacs, spiders more often rejected those that had been removed from the mother seven days earlier than those that had been freshly removed. Spiders were unable to recognize their own egg sacs versus a conspecific's. Although spiders recognize egg sacs from non-egg sacs based on mass, texture, and presumably odor when given the choice, acceptance of non-egg sacs was common when no real egg sac was available. Also, females would not reattach their own egg sac once an artificial one had been attached. Attachment of any object on the spinnerets apparently ceases searching or attachment behavior

PARDOSA MILVINA (ARANEAE, LYCOSIDAE) SPIDERLING MOVEMENT IN THE PRESENCE OF CONSPECIFIC AND HETEROSPECIFIC SILK AND EXCRETA

Volume: 32Start Page: 341End Page: 34

Dragline deposition patterns among male and female Hogna helluo (Araneae, Lycosidae) in the presence of chemical cues from prey

Volume: 37Start Page: 97End Page: 10

Proximate cues governing egg sac discrimination and recognition in the wolf spider Pardosa milvina (Araneae: Lycosidae)

Volume: 38Start Page: 387End Page: 39

Shifting thermal regimes influence competitive feeding and aggression dynamics of brook trout (Salvelinus fontinalis) and creek chub (Semotilus atromaculatus)

Abstract The natural distributions of freshwater fish species are limited by their thermal tolerances via physiological constraints and increased interspecific competition as temperatures shift toward the thermal optima of other syntopic species. Species may mediate stress from temperature change physiologically, behaviorally, or both; but these changes may compromise competitive advantages through effects on feeding and social behavior. In the Appalachian Mountains of North America, creek chub (Semotilus atromaculatus) are found in warm‐water and cold‐water streams and overlap in range with brook trout (Salvelinus fontinalis) across lower thermal maxima, where they compete for food and space. As stream temperatures continue to increase due to climate change, brook trout are under increasing thermal stress which may negatively affect their ability to compete with creek chub. To examine the influences of temperature on competitive interactions between these species, we observed feeding behavior, aggression, and habitat use differences at three temperatures approaching brook trout thermal maxima (18°C, 20°C, and 22°C) among dyad pairs for all combinations of species in experimental flow‐through tanks. We also examined feeding and habitat use of both species under solitary conditions. We found as temperature increased, feeding and aggression of brook trout were significantly reduced in the presence of creek chub. Creek chub pairs were more likely to occupy benthic areas and refugia while brook trout pairs used surface water more. Space use patterns significantly changed by pairing treatment. Aggression and space use shifts allowed increased exploitative and interference competition from creek chub when paired with brook trout that was not present in conspecific pairs. The decreased dominance of a top predator may lead to diverse impacts on stream community dynamics with implications for the future range restriction of brook trout and demonstrate possible mechanisms to facilitate competitive advantages of warm water generalist species under thermal stress

THE EFFECT OF PERCEIVED PREDATION RISK ON MALE COURTSHIP AND COPULATORY BEHAVIOR IN THE WOLF SPIDER PARDOSA MILVINA (ARANEAE, LYCOSIDAE)

Volume: 33Start Page: 76End Page: 8

Initial Analysis of Metal Accumulation in Wolf Spiders Using Graphite Furnace Atomic Absorption Spectroscopy

High concentrations of metal contaminants can have detrimental effects on biological systems. Detection of these contaminants within animals can provide information about the pattern, source, and pathways of metals as they move through and between food chains. Wolf spiders may represent a model indicator species for heavy metals since they intersect detrital, terrestrial, and aquatic food chains. They also frequently cannibalize and engage in intraguild predation. These feeding behaviors and the trophic position of spiders as apex arthropod predators, make them more likely to concentrate metals. Spiders and soil samples have been collected from several coal-impacted sites such as waste piles from surface mining, mine fire sites, coal ash burial sites, and a residential area to serve as a non-contaminated reference location. Cadmium, copper, lead, and iron will be measured. Differences in heavy metal concentrations will be measured by spider species and location and then compared to metal concentrations in the soil for each site. The spiders and soil samples are dried, digested in acid, extracted and then are analyzed by graphite furnace atomic absorption spectroscopy for a variety of metals. Soil results so far indicate (in µg/g) copper 55-116, cadmium ND – 0.01, lead 0.2-0.5, and in spiders (in µg/spider) copper 5-184, cadmium ND (none detected) – 0.005, lead ND – 0.001. Additional samples are being prepared and analyzed for these and additional metals. With these results, there can then be more insight with heavy metal accumulation in the environment