The Old Family Clock: Exploring Heritability of Chronotype in the Common House Spider Parasteatoda tepidariorum

Authors' Affiliations

Caitlin R Jones, Department of Biological Science, College of Arts and Sciences, East Tennessee State University, Johnson City, TN. Jessica Petko, Biology Department, Penn State York, York, PA. Darrell Moore, Department of Biological Science, College of Arts and Sciences, East Tennessee State University, Johnson City, TN. Thomas C Jones, Department of Biological Science, College of Arts and Sciences, East Tennessee State University, Johnson City, TN.

Location

Culp Center Ballroom

Start Date

4-25-2023 9:00 AM

End Date

4-25-2023 11:00 AM

Poster Number

28

Faculty Sponsor’s Department

Biological Sciences

Name of Project's Faculty Sponsor

Thomas Jones

Classification of First Author

Graduate Student-Master’s

Competition Type

Competitive

Type

Poster Presentation

Project's Category

Circadian Rhythms

Abstract or Artist's Statement

Circadian rhythms are nearly ubiquitous and are responsible for timing biological processes and allowing for anticipation of regular changes in the environment. The internal clocks of most organisms have a period very close to 24 hours with little variation. Spiders, however, do not seem to follow this pattern. Both the fastest (18 hours) and slowest (29 hours) naturally-occurring clocks are found in spiders, and variation within a species can be orders of magnitude larger than that of previously studied animals. Circadian rhythms are assumed to be adaptive, yet little is known about their heritability in arthropods. Heritability is defined as the amount of phenotypic variation that can be attributed to genetic variation passed down from parent to offspring. Phenotype can be influenced by many complex factors including environmental effects, dominance of genetic sequences, and gene interactions. Because of these influences, the phenotypic characteristics of an individual can vary greatly, and it is often difficult to precisely identify what is truly heritable. Using spiders as a model system, we can exploit the extreme variation in circadian rhythms to investigate the potential contribution from heritability. Strong heritability would suggest that wide variation in circadian rhythms likely reflects high genetic variability in the species. Alternatively, the environment may have a greater contribution in this variation relative to the effects of heritability. To test this, we chose Parasteatoda tepidariorum, a common cobweb spider with a relatively short circadian period of 21.7 hours and intraspecific variation of more than 4 hours. To estimate the heritability of circadian rhythm, adult females were gathered with accompanying egg cases, and juveniles were raised from those cases. Six fundamental parameters of circadian rhythms were measured from the locomotor activity of adults and juveniles. Of those six, only one parameter differed between adults and juveniles: the onset of locomotor activity during the first five days when light cycles were present (Mann-Whitney U= 1814, p= 0.04). When all six circadian parameters were compared by regression of adults to respective offspring, none showed significant correlation. This indicates that variation in circadian rhythms was likely not caused by parental genetics, and that environmental factors, such as artificial light at night, may be the source of the extreme circadian rhythms seen in spiders. Another possible cause for this variation may be the presence of weak molecular circadian oscillators that are more sensitive to environmental factors than those in most other circadian systems.

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Apr 25th, 9:00 AM Apr 25th, 11:00 AM

The Old Family Clock: Exploring Heritability of Chronotype in the Common House Spider Parasteatoda tepidariorum

Culp Center Ballroom

Circadian rhythms are nearly ubiquitous and are responsible for timing biological processes and allowing for anticipation of regular changes in the environment. The internal clocks of most organisms have a period very close to 24 hours with little variation. Spiders, however, do not seem to follow this pattern. Both the fastest (18 hours) and slowest (29 hours) naturally-occurring clocks are found in spiders, and variation within a species can be orders of magnitude larger than that of previously studied animals. Circadian rhythms are assumed to be adaptive, yet little is known about their heritability in arthropods. Heritability is defined as the amount of phenotypic variation that can be attributed to genetic variation passed down from parent to offspring. Phenotype can be influenced by many complex factors including environmental effects, dominance of genetic sequences, and gene interactions. Because of these influences, the phenotypic characteristics of an individual can vary greatly, and it is often difficult to precisely identify what is truly heritable. Using spiders as a model system, we can exploit the extreme variation in circadian rhythms to investigate the potential contribution from heritability. Strong heritability would suggest that wide variation in circadian rhythms likely reflects high genetic variability in the species. Alternatively, the environment may have a greater contribution in this variation relative to the effects of heritability. To test this, we chose Parasteatoda tepidariorum, a common cobweb spider with a relatively short circadian period of 21.7 hours and intraspecific variation of more than 4 hours. To estimate the heritability of circadian rhythm, adult females were gathered with accompanying egg cases, and juveniles were raised from those cases. Six fundamental parameters of circadian rhythms were measured from the locomotor activity of adults and juveniles. Of those six, only one parameter differed between adults and juveniles: the onset of locomotor activity during the first five days when light cycles were present (Mann-Whitney U= 1814, p= 0.04). When all six circadian parameters were compared by regression of adults to respective offspring, none showed significant correlation. This indicates that variation in circadian rhythms was likely not caused by parental genetics, and that environmental factors, such as artificial light at night, may be the source of the extreme circadian rhythms seen in spiders. Another possible cause for this variation may be the presence of weak molecular circadian oscillators that are more sensitive to environmental factors than those in most other circadian systems.