Stimulus Presentation and its Influence on Repeatability of Behavior
Richard Granquist (Department of Biology, IU)
ABSTRACT  Zigzagging and biting are commonly displayed by territorial male threespine stickleback and are used to measure courtship and aggressive tendencies, respectively. The purpose of this study was to determine whether individuals respond differently to single vs. simultaneous presentations of a nuptially colored male dummy (aggression stimulus) and a gravid head-up female dummy (courtship stimulus). Repeatability was measured to identify variation among and within individuals in the population. Each treatment was repeated three times per fish for a total of six trials. Treatment had little effect on a subject's response to the male dummy. Repeatability was low in both zigzagging (r = approx. 0.25) and biting (r = approx. 0.35). However, there was a strong treatment effect on a subject's response to the female dummy. Zigzagging repeatability was low (r = 0.21) in the single presentation and high (r = 0.91) in the simultaneous presentation. This effect was also observed in biting repeatability ( r = 0.40 in the single presentation and r = 0.70 in the simultaneous presentation). The increase in repeatability from the single to the simultaneous presentation was due to an increase in the variation among individuals and not because of decreased variation within individuals. Further study may reveal why this change in repeatability occurred, but it is likely that these differences are due to either temporal variation in individual responses or the use of different behavioral tactics when territorial males simultaneously encounter stimuli that elicit mutually incompatible behaviors (e.g., aggression and courtship).

 
Mate Choice in the Sailfin Molly (Poecilia latipinna): Female Preference for Male Fin Elaborations and Body Size
R. David MacLaren (Department of Biology, IU)
ABSTRACT   Female perceptual biases influence the evolution of male secondary sexual traits. Males that evolve traits that exploit these preexisting preferences are favored by sexual selection. The role of sensory biases in the evolution of female preferences for various fin elaborations has been well studied in live-bearing fishes (Poeciliidae). The specific form and placement of the fin elaboration may be a result of idiosyncratic patterns of genetic variation in an ancestral population. The fin elaborations of Poeciliids may reflect a general perceptual preference of females to associate with larger males. Male sailfin mollies erect their enlarged dorsal fin and display them to females in an elaborate courtship display. I propose that the sexually dimorphic dorsal fin of this fish may function as a metabolically inexpensive means by which males may appear larger, thereby exploiting the female's perceptual system. The shape and strength of female preference functions were obtained in a choice test in which females were presented with pairs of dummies that simulated males that differed in dorsal fin and body size. Females responded to the dummy males much as they do to live conspecifics and exhibited a significant directional preference to associate with male dummies of greater lateral projection area (LPA). The strength of female preference for male body size was greater than that for fin size. However, the directional nature of both preference functions suggests the sailfin trait may have originated as an incidental result of selection for increased LPA owing to the greater stimulation of the female's retina at a given viewing distance.

 
Development of Preference in a Choice Situation
Eric W. Macaux (Department of Psychology, IU)
ABSTRACT   Compared to the vast literature on steady-state behavior, relatively few studies have sought to understand how an organism comes to prefer the richer of two probabilistic alternatives. This is quite surprising because although every experiment includes a period of acquisition of preference the majority of studies have not analyzed the data from this early stage. In the present research, we examined how two variables affect the rate at which pigeons learn to prefer the richer of two probabilistic alternatives. Experiment 1 varied the overall probability of reward, T, while keeping the difference in reinforcement probability, D, constant. Experiment 2 varied the difference in reinforcement probability, D, while keeping the overall probability of reinforcement, T, constant. We propose a theory based on a Weber-like ratio D/T (perhaps with different weights, e.g., D a/T b) that determines the rate at which the optimal patch is learned such that larger ratios result in faster acquisition. In general, the theory accounted for the results well.

 
Testing Timing Theories in a Time-Place Learning Task
Matthew T. Sitomer (Department of Psychology, IU)
ABSTRACT   The predictions of two competing interval timing theories, Learning to Time (LeT; Machado, 1997) and Scalar Expectancy Theory (SET; Gibbon, 1977), were tested in a time-place learning task. Pigeons learned to respond at one of two spatially disparate locations depending on the duration of a diffuse sample stimulus. LeT assumes that animals use overt behavioral patterns to time intervals. In the present experiment, the birds exhibited consistent locomotor patterns during the interval to be timed. Pivoting floor panels recorded a bird's position in the chamber throughout the session, enabling an analysis of arrival and departure times at each patch. While SET predicts uncorrelated arrival and departure times, LeT predicts a positive correlation between these two measures. The correlation results were mixed; but, overall, departure times were considerably earlier than the predictions made by both theories.

 
Syringeal Lateralization of Song Production in Northern Mockingbirds: A Comparative Study of Vocal Strategies
Sue Anne Zollinger (Department of Biology, IU)
ABSTRACT   Songbirds produce their vocalizations by means of a bipartite syrinx, a vocal organ located at the junction of the two bronchi, just caudal to the trachea. The right and left sides of the songbird syrinx are controlled independently, which allows for the expression of two distinct motor patterns and potentially the production of two, simultaneous, harmonically unrelated sounds. Different species of songbirds use different patterns of motor lateralization for song production using the right and left syrinx. It is unclear, however, why these diverse vocal motor strategies are used. Three possible hypotheses include: first, physiological constraints on the syrinx make it possible to produce only a certain range of sounds from each side of the syrinx and songbirds must use a coordinated effort of both sides to increase the complexity of song. Second, innate differences in development or physiology between species dictate how the syrinx is used to produce adult song. Third, there may be auditory cues present in the song of adult tutors that tell a listener how the sound was produced, and the listener uses these cues to imitate the song using the same production strategy. Northern mockingbirds (Mimus polyglottos) are renowned as accomplished vocal mimics. Since they regularly sing copies of the songs of heterospecifics, they present a unique opportunity to study these hypotheses. I have trained young mockingbirds to sing songs of several species that have been shown to use different patterns of syringeal lateralization. By studying the song mimicries of these mockingbirds in the laboratory, I can address the hypotheses about why different motor strategies exist. I am currently recording song, and airflow through the left and right bronchi in mockingbirds singing heterospecific song. I will present these data and discuss the implications they have for understanding the diversity of song production strategies and why they exist.

 
Ontogeny and the Consistency of Individual Differences in Behaviour Among Gray Treefrog Tadpoles
Cerisse Allen (Department of Biology, IU)
ABSTRACT   Developmental processes can profoundly affect the way that natural selection acts on behaviour. Change in the behavioural differences among indivduals or variability within individuals can affect the relationship between behaviour and fitness through ontogeny. To address developmental effects on within and among individual components of behavioural variation I examined the repeatability and ontogenetic consistency of one component of escape behaviour during larval ontogeny using tadpoles of the gray treefrog (Hyla chrysoscelis). Maximum burst speed and body length of individuals were assayed at four ages during larval development (14, 22, 32, and 41 days post-hatching). Repeatability of burst speed was not affected by ontogeny despite changes in the mean behaviour expressed through time. Individual differences in behaviour and morphology were only moderately consistent through ontogeny, and individuals were more consistent in their expression of body length than burst speed. Tadpoles appear to follow non-parallel ontogenetic trajectories so that among-individual differences are redistributed across ages. As a result, aspects of the larval phenotype are decoupled across ages and selection acting on behaviour or morphology at any one stage may have different evolutionary effects than selection that acts at other times through ontogeny.

 
Hormones in Yolk Layers and Offspring Sex Ratios Vary Seasonally in a Turtle
Rachel M. Bowden, Michael A. Ewert, Joseph L. Lipar & Craig E. Nelson (Department of Biology, IU)
ABSTRACT   The presence of hormones in yolks of freshly laid eggs has recently been described in reptiles. These hormones are probably of maternal origin. Their potential to influence offspring sex may be enhanced by temperature-dependent sex determination.
    Profiles of circulating hormones have been described for several temperate turtles. There appears to be a general pattern to the seasonal oscillations in testosterone (T), progesterone (P), and estradiol (E2). To determine whether this pattern is represented in egg yolks, we measured T, P, and E2 concentrations via radioimmunoassay in three layers of yolk from eggs of early and late nesting female painted turtles (Chrysemys picta). Also, we extracted small yolk biopsies to measure T and E2. We compared the hormone concentrations from the biopsied eggs to the sex ratio of their clutchmates to determine whether maternally-derived yolk hormones influence offspring sex.
    T and P concentrations were highest in the exterior layer of yolks and E2 concentrations were lowest. The same layered pattern of hormones occurred in red-eared sliders (Trachemys scripta elegans). Yolk E2 concentrations varied seasonally in painted turtles, with low levels in all yolk layers early in the nesting season and higher levels in all layers later on. Neither T nor P exhibited significant seasonal variation. In the yolk biopsies, there also was seasonal variation in E2, but not in T. We found a significant correlation with sex ratio for E2, but not for T.

 
Experimentally Elevated Testosterone in Male Dark-eyed Juncos Suppresses Cell-Mediated Immune Function of Social Mates and Offspring
Joseph M. Casto, Ian M. Parker-Renga, Ellen D. Ketterson, & Val Nolan Jr. (Department of Biology, IU)
ABSTRACT   Experimental elevation of testosterone (T) in male dark-eyed juncos suppresses immunity and enhances male attractiveness to females. T also suppresses male parental behavior and their social mates attempt to compensate for reduced male care by increasing their own parental effort. Here we test whether the effects of treating males with T might extend beyond individual males and indirectly influence immune function of their social mates and offspring. We used wing-web swelling in response to an antigenic challenge as a test of cell-mediated immunity. We tested free-living females juncos that were mated to T-treated males (T-males) or controls (C-males), and tested offspring of those matings. We found that immune responses were significantly suppressed in mates of T-males (41% lower) and their offspring (19% lower) as compared to those of C-males. Combining these results with earlier findings, we suggest that the costs to males of T-induced attractiveness may go beyond immunosuppression. Reductions in T-nestling immunity may explain a previous finding that in juncos T-males fledge significantly fewer young from their nests than C-males. Additionally, the consequences for females of choosing males with traits enhanced by T appear to be more complicated than previously thought.

 
Fine Structure of the Sperm Storage Organs of the Caribbean Fruitfly, Anastrepha suspensa (Diptera: Tephritidae)
Ann H. Fritz & F.R. Turner (Department of Biology, IU)
ABSTRACT   Female insects with multiple sperm storage organs may control the ultimate destination of spermatozoa and the rate at which it is stored. The Caribbean fruitfly, Anastrepha suspensa, may store and use sperm differentially with respect to its 3 spermathecae. In order to understand the mechanisms responsible for the dynamics of sperm storage and use in A. suspensa, the fine structure of female sperm storage organs was detailed using in vivo DAPI staining, tissue sectioning, and scanning and transmission electron microscopy. Structures not previously described for this species include a ventral receptacle for sperm storage, a conical-shaped valve at the junction between the spermathecal capsules and their ducts, laminar and granular secretions, and spermathecae with sclerotized, hollow projections that terminate in single glandular cells.

 
Offspring Sex Ratio is Unrelated to Male Attractiveness in Dark-eyed Juncos (Junco hyemalis)
Jennifer L. Grindstaff, C.A. Buerkle, J.M. Casto, V. Nolan Jr. & E.D. Ketterson (Department of Biology, IU)
ABSTRACT   Sex allocation theory predicts that parents should bias investment toward the offspring sex that confers higher relative fitness on the parents. When variance in reproductive success is higher in males than females, and some males are more attractive to females than others, thereby achieving higher reproductive success, then female parents mated to attractive males are expected to bias reproductive allocation towards sons. Modification of the primary sex ratio is one mechanism by which avian parents may bias allocation. In mate choice trials, captive female dark-eyed juncos (Junco hyemalis) prefer to associate with males whose circulating testosterone level has been elevated experimentally. We asked whether females socially mated to testosterone-treated males in nature might bias the sex ratio of progeny in favor of sons. We determined the primary sex ratio of broods using a sex-linked molecular marker, the CHD gene on the W-chromosome. We found no relationship between the hormonal treatment of males and the primary or secondary sex ratios of offspring produced by their social mates. Sex ratio was also unrelated to breeding-season date, study year, male viability, or female age. While unlikely, it is possible that female juncos are not able to manipulate the primary sex ratio of their broods. More likely, possible benefits to female juncos of producing attractive sons may be small because: (1) attractive males do not necessarily have higher fitness, depending on the trade-offs involved for males; and (2) when such benefits exist, they may be outweighed for females by the costs of compensating for the reduced paternal care of attractive males.

 
Parental Activities That May Stimulate Their Late-Term Spiny Mice (Acomys cahirinus) Fetuses
Jill H. Menge, S.H. Simmonds & J.R. Alberts (Department of Psychology, IU)
ABSTRACT   Current conceptions regarding the impact of maternal behavior on fetal development are almost entirely derived from studies of species that give birth to altricial offspring, e.g. Norway rat (Rattus norvegicus). After about a 22-day gestation period, Norway rat offspring are born with relatively immature sensory and motor systems. Studies of the Norway rat have shown that the behavior of pregnant females compresses, vibrates, and accelerates fetuses. Prenatal stimulation has been found to facilitate the acquisition of independent respiration, accelerating onset of suckling, and establishing response patterns to maternal odors. Little is known about the effects of maternal behavior on fetal development in mammals that give birth to precocial offspring, e.g. spiny mouse (A. cahirinus). After about a 38-day gestation period, spiny mice are born with well-developed sensory and motor systems. To investigate the impacts of maternal behavior on fetuses with more advanced sensory and motor development, the activities of pregnant female spiny mice were described. We report our systematic observations of the activities of seven spiny mice (A. cahirinus), living with their pair-bonded mate under standardized laboratory conditions. The mice were marked to distinguish sex and their behavior was recorded continuously by timelapse videography. Frequency and duration of maternal locomotion, grooming, rearing, stirring, scratching, and resting as well as paternal grooming of the mothers abdomen were quantified for 4- and 2-days prior to parturition, as well as on the day of birth. We describe a profile of parental activity that may provide important stimulation to the perinatal spiny mouse pup.

 
Thermographic Analysis of Brown Adipose Tissue Activity in Infant Mice
Thalia B. Schlossberg & J. R. Alberts (Department of Psychology, IU)
ABSTRACT   Most studies of thermogenesis by brown adipose tissue (BAT) imply, by virtue of the experimental design and parameters, that BAT thermogenesis is a mechanism used in thermal emergencies as a final effort to protect body temperature. We exposed mouse pups to roughly sinusoidal fluctuations in ambient temperature (max range: 37C - 26C). Pups repeatedly activated and de-activated interscapular BAT thermogenesis as ambient temperature decreased and increased. Infrared thermography enabled us to visualize when and for how long pups of different ages are thermogenic. We suggest that BAT thermogenesis is not confined to emergency situations, but may be predominantly used when pups face more modest, normally-occurring variations in ambient temperature. We also observed that pups use BAT to regulate body temperatures while in the nest. We compared the BAT activity of age-matched single pups to groups. BAT thermogenesis is displayed by pups in huddles.