Project Title

Extraordinary Variation in Circadian Free-Running Periods Observed in Spiders Appears to be Limited to the Superfamily Araneoidea

Authors' Affiliations

Alexandria E. Shepherd, Department of Biology, College of Arts and Sciences, East Tennessee State University, Johnson City, TN. Thomas C. Jones, Department of Biology, College of Arts and Sciences, East Tennessee State University, Johnson City, TN. Darrell Moore, Department of Biology, College of Arts and Sciences, East Tennessee State University, Johnson City, TN.

Location

Culp Ballroom

Start Date

4-7-2022 9:00 AM

End Date

4-7-2022 12:00 PM

Poster Number

98

Faculty Sponsor’s Department

Biological Sciences

Name of Project's Faculty Sponsor

Thomas Jones

Additional Sponsors

Darrell Moore

Classification of First Author

Undergraduate Student

Competition Type

Competitive

Type

Poster Presentation

Project's Category

Circadian Rhythms

Abstract or Artist's Statement

Almost all organisms have approximately a 24-hour circadian rhythm that enables them to anticipate their environment’s daily rhythmicity. Anticipation increases their likelihood of success in foraging, reproduction, predation, and other life events. Therefore, a disruption of their endogenous clock results in detrimental physiological consequences that significantly impact organisms’ fitness. Surprisingly, we have found numerous spider species with free-running periods that deviate greatly from 24 hours. Free-running period (FRP) is a standard measurement of the period of an organism’s circadian rhythm found by measuring periodicity of behaviors or physiology under constant conditions (e.g., constant darkness and temperature). So far, these extreme spider FRPs have only been observed in the superfamily Araneoidea, but we have only limited sampling of species outside this clade. Therefore, we want to fill this data gap of non-araneoid spiders to deepen our understanding of the evolution of circadian clocks in spiders. Also, we will observe if significant deviation from 24 hours and wide variation in FRP are common to all spider species or are only characteristics of araneoid spiders. Here, we describe the FRPs of four non-araneoid spider species belonging to the RTA clade: Schizocosa avida, Phidippus audax, Agelenopsis pennsylvanica, and Mecaphesa celer. We detected significant free runs (mean + SD) at p<0.001 using Lomb-Scargle periodograms in three out of the four species: S. avida (23.84 ± 1.03 h); P. audax (22.67 ± 0.36 h); and A. pennsylvanica (23.97 ± 0.32 h). However, M. celer was found to be arrhythmic under constant conditions. These findings of near 24-hour FRPs with low deviation among the RTA species, along with previous data, strongly suggest that extreme FRPs are confined to the Araneoidea clade. Thus, we have phylogenetically localized a major evolutionary change in the circadian system of spiders occurring in the Araneoidea clade, approximately 170 million years ago.

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Apr 7th, 9:00 AM Apr 7th, 12:00 PM

Extraordinary Variation in Circadian Free-Running Periods Observed in Spiders Appears to be Limited to the Superfamily Araneoidea

Culp Ballroom

Almost all organisms have approximately a 24-hour circadian rhythm that enables them to anticipate their environment’s daily rhythmicity. Anticipation increases their likelihood of success in foraging, reproduction, predation, and other life events. Therefore, a disruption of their endogenous clock results in detrimental physiological consequences that significantly impact organisms’ fitness. Surprisingly, we have found numerous spider species with free-running periods that deviate greatly from 24 hours. Free-running period (FRP) is a standard measurement of the period of an organism’s circadian rhythm found by measuring periodicity of behaviors or physiology under constant conditions (e.g., constant darkness and temperature). So far, these extreme spider FRPs have only been observed in the superfamily Araneoidea, but we have only limited sampling of species outside this clade. Therefore, we want to fill this data gap of non-araneoid spiders to deepen our understanding of the evolution of circadian clocks in spiders. Also, we will observe if significant deviation from 24 hours and wide variation in FRP are common to all spider species or are only characteristics of araneoid spiders. Here, we describe the FRPs of four non-araneoid spider species belonging to the RTA clade: Schizocosa avida, Phidippus audax, Agelenopsis pennsylvanica, and Mecaphesa celer. We detected significant free runs (mean + SD) at p<0.001 using Lomb-Scargle periodograms in three out of the four species: S. avida (23.84 ± 1.03 h); P. audax (22.67 ± 0.36 h); and A. pennsylvanica (23.97 ± 0.32 h). However, M. celer was found to be arrhythmic under constant conditions. These findings of near 24-hour FRPs with low deviation among the RTA species, along with previous data, strongly suggest that extreme FRPs are confined to the Araneoidea clade. Thus, we have phylogenetically localized a major evolutionary change in the circadian system of spiders occurring in the Araneoidea clade, approximately 170 million years ago.