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Sargent Lab - Research

Current Projects

Courtship and Mate Choice in Fishes:
Integrating Behavioral and Visual Ecology

A male Limia perugiae, above left, courting a female, below right.

This project focuses on the interaction between male breeding coloration as honest signals and female choice, within the constraints of the visual ecology of the species in question. Current projects focus on two species of poeciliid fishes, Perugia's Limia (Limia perugiae) and the guppy (Poecilia reticulata). 

Representative Publications:

Rush, VN, McKinnon, JS, Abney, MA & Sargent, RC, 2003. Reflectance spectra from free-swimming sticklebacks (Gasterosteus): Social context and eye-jaw contrast. Behaviour, 140:1003-1019. (pdf

Sargent, RC, Rush, VN, Wisenden, BD & Yan, HY, 1998. Courtship and mate choice in fishes: integrating behavioral and sensory ecology. American Zoologist, 38:82-96. (pdf)


Condition Indicators in the Limiting Sex

A female convict cichlid, Archocentrus nigrofasciatum. The orange coloration generally is not expressed in males.

This project focuses on the functional significance of female breeding coloration in the convict cichlid, Archocentrus nigrofasciatum. Preliminary data suggest that this coloration may correlate with female fecundity, and possibly energy reserves. Current experiments are examining how male and female convict cichlids respond to female breeding coloration. Future projects will examine female signaling in poeciliid fishes. This project began as Kasi Jackson's doctoral dissertation.

Representative Publications:

Jackson, JK, Brown, AL, Lloyd, TK, Orsborne, T, & Sargent, RC, In preparation. Effects of diet on female breeding coloration in the convict cichlid, Archocentrus nigrofasciatum


Interactions Between
Intersexual & Intrasexual Conflict
A female western mosquitofish, Gambusia affinis.

This project focuses on the interaction between male sexual harassment of females, and female dominance hierarchies in the mosquitofish, Gambusia affinis. Previous work found that female density dependence can swamp the negative effects of male harassment, such that females have higher fecundity and growth at high male and low female density, despite experiencing higher rates of male harassment under these conditions (Smith & Sargent 2006). Preliminary data suggest that females have size dependent dominance hierarchies, that males preferentially harass larger females, and that male harassment can reverse the size dependent effects of female dominance on growth in subordinate females. This project began as Chad Smith's masters thesis. Current experiments include using microsatellite DNA markers to test hypotheses on potential genetic benefits of multiple mating.

Representative Publications:

Smith, CC & Sargent, RC, 2006. Female fitness declines with increasing female density but not male harassment in the western mosquitofish, Gambusia affinis. Animal Behaviour 71:401-407. (pdf)

Smith, CC, 2007. Independent effects of male and female density on sexual harassment, female fitness, and male competition for mates in the western mosquitofish. Behavioral Ecology and Sociobiology 61:1349-1358.(pdf)



Egg Trading in Simultaneous Hermphrodites

Chalk bass, Serranus tortugarum.

This project is the doctoral dissertation research of Mary Hart, who is co-advised by Phil Crowley and Craig Sargent. This project examines how "streaking" (i.e. stolen fertilizations from extra-pair fish) effects the cooperation between partners who take turns playing male and female roles, alternately releasing eggs and sperm. This project also examines how ecological variables such as predation risk and population density effect streaking and the degree of cooperation within pairs.

Representative Publications:

Crowley, PH, T Cottrell, T Garcia, M Hatch, RC Sargent, BJ Stokes, and JM White 1998. Solving the complementarity dilemma: Evolving strategies for simultaneous hermaphroditism. Journal of Theoretical Biology, 195:13-26. (pdf

Hart, MK, Kratter, AW, Svoboda, A-M, Lawrence, CL, Sargent, RC and Crowley, PH. 2010. Sex allocation in a group-living simultaneous hermaphrodite: effects of density at two different spatial scales. Evolutionary Ecology Research, 12:189-202 (pdf)


Meditation, Sleep & Performance

Mediation in the O'Hara Lab
(left to right: Bruce O'Hara, Prashant Kaul, Ling Liu)

This project is the doctoral dissertation research of Prashant Kaul, who is co-advised by Bruce O'Hara and Craig Sargent. This project addresses the interaction between sleep, meditation and performance. One question is whether meditation can pay off sleep debt, as has been claimed by some practitioners. Another question, is whether meditation improves performance on tasks that are sensitive to sleep debt, such as reaction time on a Psychomotor Vigilance Task (PVT). Our data indicate that meditation provides at least a short term enhancement on PVT performance in both rested and sleep-deprived meditators, in both novice meditators trained at the University of Kentucky and experienced meditators in India. Data from experienced meditators in India also suggest that meditation may be able to replace a portion of sleep time, but cannot totally replace sleep. 

Representative Publications:

Kaul, P, Passafiume, J, Sargent, C & O'Hara, B. 2010. Meditation acutely improves psychomotor vigilance, and may decrease sleep need. Behavioral and Brain Functions 2010, 6:47 (29 July 2010) (pdf)



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