Eight-Legged Encounters: Using Organismal Biology to Bring Science Education to Families & Communities

Path of the Predators: A Journey Through the Living Arachnids. Illustrations by Pawl Tisdale WHAT IS AN ARTHROPOD? CREATE A CHELICERATE ASSEMBLE AN ARACHNID TISSUE PAPER FLOWER MICROSCOPE MADNESS Eight-Legged Encounters Impact Change in interest in learning about scientific discoveries among adult respondents (n = 63). Youth’s interest in science activities (n = 42). Respondents were 50% female, 50% male and ranged in age from 4 – 14 with a mean of 7.7

Eight Legged Encounters

This program was funded in part by a National Science Foundation grant (DRL–1241482 to EAH). Material was developed in collaboration with Marie- Claire Chelini, Jessie Rose Storz, Cody Storz, and Malcolm Rosenthal. Steven Schwartz, Jason Stafstrom, Kathy French, Priscilla Grew, and Judy Diamond were all extremely helpful in grant writing, facilitating the first live event, and/or discussions. Pawl Tisdale (artist) was phenomenal to work with on all aspects of the project! TABLE OF CONTENTS CLASSIFICATION & TAXONOMY STATIONS I. WHAT IS AN ARTHROPOD? page 4 a. The goal of this station is to introduce the audience to some basic information about “arthropods”. Who are they? How and why are they grouped together? Answers to these questions are achieved through a sorting game with plastic animals. II. CREATE A CHELICERATE page 14 a. This station introduces the audience to the basic characteristics of chelicerates (a group which they have learned about from Station I) by allowing them to build their own chelicerate out of clay. III. ASSEMBLE AN ARACHNID page 16 a. Arachnids are surprisingly diverse, with 11 different living orders! This station introduces the audience to the diversity of body types found within the 11 living arachnid orders through a coloring activity. SPIDER-SPECIFIC STATIONS (ORDER ARANEAE) IV. BUILD A BURROW page 20 a. The first spiders didn’t build orb webs to catch prey out of the air, but instead, built silk-lined burrows with trapdoors. This station explores the early function of spider silk. V. CRIBELLATE VS. ECRIBELLATE SILK page 22 a. Spiders have evolved two different ways to improve the efficiency of prey capture with their webs. This station explores those two evolutionary solutions. VI. WEAVE A WEB page 24 a. Orb webs (the classical web most non-biologists envision when asked to think of a spider web) are quite complex structures. How do spiders build orb webs? Do they use the same type of silk for the entire web? Answers to these questions can be obtained as participants are guided through their own web-weaving exercise. VII. CATCH A MOTH page 27 a. This station highlights the unique foraging strategy of the ‘bolas spider’ through a game in which participants try to catch a moth out of the air using a lasso. VIII. TISSUE PAPER FLOWER page 29 a. This station lets the audience create their own tissue paper flower upon which their chosen crab spider (made of paper) can forage. It introduces the fact that some spiders can change color and highlights the adaptive value of camouflage. RESEARCH-RELATED STATIONS IX. MICROSCOPE MADNESS page 33 a. This station provides the audience an opportunity to take an up-close look at spiders - to examine body parts they cannot normally see and to get them thinking about how these details might relate to an animals’ lifestyle or evolutionary history. X. COMMUNITY EXPERIMENT page 38 a. This station engages participants in a hand’s on spider feeding experiment that examines the influence of seismic (vibratory) cues on foraging success. Participants are encouraged to imagine how their results may relate to the evolution of courtship displays that incorporate specific sensory modalities. MISCELANEOUS STATIONSXI. SILKEN SPINNERS page 44 a. This station provides some “down time” for participants, where they can sit and watch the amazing footage and associated information put together by the BBC in David Attenborough’s “Silken Spinners” episode from Life in the Undergrowth.XII. SOUND STATION page 45 a. Most people do not realize that some spiders can “sing” in the form of stereotyped vibrations that are sent through a substrate, or surface upon which they are standing (e.g. a leaf, a twig, a blade of grass, etc.). Here, participants can listen to the sounds of spiders and are asked to imagine if they might find these songs attractive. XIII. SPIDER DANCE DISCO page 46 a. Not only can spiders sing, but they can also dance! Participants can observe some of the amazing dances that spiders do and can learn some of their own spider dance moves by watching the “Spider Dance Disco” XIV. READ ALOUD page 47 a. This station enables participants to play with some arachnid stuffed animals, puzzles, and to look through arachnid-related children’s books. Several books are listed as suggestions for read alouds. PATH OF PREDATORS XV. LIVING ARACHNID ORDERS page 48 a. Araneae, Amblypygi, Thelyphonida, Schizomida, Scorpiones, Solifugae, Palpigradi, Ricinulei, Pseudoscorpiones, Acari, Opilione

Eight-Legged Encounters: Using Organismal Biology to Bring Science Education to Families & Communities

Path of the Predators: A Journey Through the Living Arachnids. Illustrations by Pawl Tisdale WHAT IS AN ARTHROPOD? CREATE A CHELICERATE ASSEMBLE AN ARACHNID TISSUE PAPER FLOWER MICROSCOPE MADNESS Eight-Legged Encounters Impact Change in interest in learning about scientific discoveries among adult respondents (n = 63). Youth’s interest in science activities (n = 42). Respondents were 50% female, 50% male and ranged in age from 4 – 14 with a mean of 7.7

A Review of Leg Ornamentation in Male Wolf Spiders, with the Description of a New Species from Australia, \u3ci\u3eArtoria schizocoides \u3c/i\u3e (Araneae, Lycosidae)

Morphological modifications of the first pair of legs in addition to widespread color variations of these legs among males of closely related species have been reported in a variety of spiders. Here, the evidence for sexual dimorphism in male foreleg morphology within wolf spiders (family Lycosidae) is reviewed and shown to occur in a number of species belonging to at least seven genera in five subfamilies: Alopecosa, Hogna, Schizocosa (all Lycosinae) Pirata (Piratinae), Evippa, (Evippinae), Pardosa (Pardosinae) and Artoria (Artoriinae). These modifications, often in combination with distinct dark pigmentation, can be divided into three major groups: leg elongation, segment swelling and exaggerated setation (“brushes”). The latter two occur mainly on the tibial segment of the first leg. The function of these foreleg modifications has been studied most extensively in the genus Schizocosa. Since the courtship displays of all male Schizocosa incorporate a seismic component, foreleg ornamentation (namely pigmentation and associated “brushes”) composes only one part of a multimodal courtship display. The function of this foreleg ornamentation appears to vary across closely related Schizocosa species and in some instances involves an interaction with the seismic signaling component. In most instances it appears to play a role in female mate choice and/or mate choice learning. In addition to reviewing lycosid foreleg modifications, we describe a new species of wolf spider, Artoria schizocoides from southwestern Western Australia that possesses sexually dimorphic modifications of the tibia of the first leg. Unique within the Artoriinae, males of this species carry spatulate setae on the ventral side of the tibia of the first leg that differ morphologically from other leg modifications in wolf spiders

Absence of Mate Choice and Postcopulatory Benefits in a Species with Extreme Sexual Size Dimorphism

Most hypotheses related to the evolution of female-biased extreme sexual size dimorphism (SSD) attribute the differences in the size of each sex to selection for reproduction, either through selection for increased female fecundity or selection for male increased mobility and faster development. Very few studies, however, have tested for direct fitness benefits associated with the latter – small male size. Mecaphesa celer is a crab spider with extreme SSD, whose males are less than half the size of females and often weigh 10 times less. Here, we test the hypotheses that larger size in females and smaller size in males are sexually selected through differential preand postcopulatory reproductive benefits. To do so, we tested the following predictions: matings between small males and large females are more likely to occur due to mate choice; females mated to small males are less likely to accept second copulation attempts; and matings between small males and large females will result in larger clutches of longer-lived offspring. Following staged mating trials in the laboratory, we found no support for any of our predictions, suggesting that SSD in M. celer may not be driven by pre- or post-reproductive fitness benefits to small males

Increased insertion number leads to increased sperm transfer and fertilization success in a nursery web spider

Across animals, a male\u27s fitness is largely dictated by his ability to fertilize eggs; and there exists a plethora of male adaptations associated with increasing fertilization success. In the nursery web spider, Pisaurina mira, males restrain females prior to and during copulation by wrapping them with silk. Previous research demonstrates that copulatory silk wrapping reduces a male\u27s chance of being sexually cannibalized and increases the number of sperm transfer opportunities (termed insertions) that a male can achieve within a mating. While avoiding cannibalism provides an obvious survival benefit to males, the impact of insertion number on male fitness remains unknown. This study tested the hypothesis that increased insertion number realized through copulatory silk wrapping increases (1) the quantity of sperm transferred and (2) fertilization success. To accomplish this, we directly quantified the amount of sperm in male pedipalps (i.e. the male sperm storage organ) before mating and after obtaining one or two insertions. We also, indirectly quantified fertilization success by measuring the number of hatched offspring when males were capable of achieving one versus two insertions within a mating. In support of our hypotheses, we found that males transfer roughly twice the amount of sperm when achieving two insertions compared to one. We additionally found that the amount of sperm transferred is negatively related to female size. In terms of offspring number, females obtaining two insertions had more offspring compared to females obtaining only one insertion. These results show that males achieve a fertilization benefit from increased insertion number, which is obtained through the male behavior of copulatory silk wrapping

ANATOMY AND PHYSIOLOGY OF GIANT NEURONS IN THE ANTENNIFORM LEG OF THE AMBLYPYGID \u3ci\u3ePHRYNUS MARGINEMACULATUS\u3c/i\u3e

Amblypygids have modified front legs that are not used for locomotion, but rather to probe the environment in the manner of antennae. These elongate, motile sense organs are referred to as antenniform legs. We have found remarkable replication in structure and function of giant neurons in the antenniform leg of the amblypygid Phrynus marginemaculatus C. L. Koch 1841 when compared with other amblypygids. These neurons have such large diameter axons (several μm) that their action potentials can be recorded outside the cuticle. Their cell bodies are found in the periphery, in the distal-most segments of the antenniform leg, centimeters away from the central nervous system. Primary afferents from sense organs on the antenniform leg synapse onto some of the giant fibers in these distal segments of the leg. Standard histological techniques and a novel whole mount preparation were used to identify the location of giant cell bodies within the antenniform leg. We found several new cell bodies in segments 10–20, three of which were predicted by previous electrophysiological studies of another amblypygid, Heterophrynus elaphus Pocock 1903. Electrophysiology was used to show that the structure and function of four of the giant neurons, GN1, 2, 6, and 7, is very similar in P. marginemaculatus and H. elaphus. Heterophrynus elaphus inhabits humid tropical forests in South America while P. marginemaculatus individuals were collected from a pine rock hammock in the Florida Keys, USA. The similarity of findings in species with such distinct habitats suggests that the giant neurons are required for basic neuromechanical operation of these extended limbs, and are not subject to intense selection via ecological factors

Nocturnal foraging enhanced by enlarged secondary eyes in a net-casting spider

Animals that possess extreme sensory structures are predicted to have a related extreme behavioral function. This study focuses on one such extreme sensory structure—the posterior median eyes of the net-casting spider Deinopis spinosa. Although past research has implicated the importance of vision in the nocturnal foraging habits of Deinopis, no direct link between vision in the enlarged eyes and nocturnal foraging has yet been made. To directly test the hypothesis that the enlarged posterior median eyes facilitate visually based nocturnal prey capture, we conducted repeated-measures, visual occlusion trials in both natural and laboratory settings. Our results indicate that D. spinosa relies heavily on visual cues detected by the posterior median eyes to capture cursorial prey items. We suggest that the enlarged posterior median eyes benefit D. spinosa not only through increased diet breadth, but also by allowing spiders to remain active solely at night, thus evading predation by diurnal animals

Testing the Hypothesized Antipredator Defence Function of Stridulation in the Spiny Orb-Weaving Spider, \u3ci\u3eMicrathena gracilis\u3c/i\u3e

The observable diversity of antipredator defenses across organisms demonstrates predation’s impact on trait evolution. The functions of many traits that are presumed to have an antipredator function have never been directly tested. The spiny orb-weaving spider, Micrathena gracilis, for example, stridulates when grasped. While stridulation was first hypothesized to be an antipredator defense nearly 50 years ago, no data exist to support this hypothesis. To explore the form and function of M. gracilis stridulation, we first quantified the behavioral and acoustical properties of sound production. Next, using laboratory assays, we directly tested the effect of stridulation on survival with an avian predator—blue jays, Cyanocitta cristata. Finally, we conducted a large mark-recapture field study in which we compared the natural survival of experimentally manipulated adult female M. gracilis that could not stridulate (silenced) versus could stridulate (control). Stridulatory pulses produced broadband frequency spectra, consistent with acoustic antipredator defenses in other taxa. We also observed stridulation by male M. gracilis for the first time. In staged laboratory interactions with captive blue jays, we found no differences in survival between silenced and control M. gracilis. Similarly, in our mark-recapture field study, we found no differences in survival estimates between silenced and control groups, nor an effect of stridulation rate. While M. gracilis stridulation closely resembles antipredator stridulation in other arthropods, our behavioral data do not yet provide solid support for an antipredator function in M. gracilis

Tactical adjustment of signaling leads to increased mating success and survival

Most sexually reproducing animals overcome the challenge of searching for and attracting mates by utilizing signals that are broadcast through a spatially and temporally varying environment. A diverse suite of behavioral solutions exist for overcoming such environmental variability, including the adjustment of signaling behavior based upon receiver feedback. Few studies have directly examined the relationship between such tactical signaling adjustments and proxies of male fitness; the few that have, failed to find a relationship. Using the wolf spider, Schizocosa rovneri, we set out to first quantify among-male variation in the form and degree of responsiveness to female feedback. Following exposure to female receptivity cues, some males increased their signaling on an effective signaling substrate (filter paper) while others decreased signaling on the effective substrate. These groups of males were then run through mating trials, conducted in a heterogeneous environment, to examine the relationship between male signaling adjustments and subsequent mating success. Males that adaptively adjusted their signaling (i.e. increased signaling on a more effective substrate) were (1) more likely to copulate, (2) achieved a copulation more quickly and (3) were less likely to be attacked; thus establishing a positive relationship between tactical adjustments of courtship signaling and male fitness