SEMINAR: MBF602 STUDENT SEMINAR *TOMORROW* FRIDAY 4/20 @ 1pm---Samuel Loftus and Phillip Gillette

[Pam Harris <pharris@rsmas.miami.edu>]

MBF Student Seminar Series

 

Samuel Loftus

Advisor: Dr. Douglas Crawford

“Inter-individual variation in complex I activity in Fundulus heteroclitus along a steep thermocline.”

The first enzyme in the oxidative phosphorylation pathway, Complex I (CI, E.C.: 1.6.5.3), is a large heteromeric enzyme complex with 45 protein subunits.  CI translocates H+ ions across the mitochondrial inner membrane and thus the synthesis of ATP.  Among northern and southern populations of the teleost fish Fundulus heteroclitus, CI subunit genes have fixed amino acid substitutions and differences in oxidative metabolism among populations of F. heteroclitus.  Enzyme activity was measured in 121 individuals from 5 populations of F. heteroclitus and its sister taxa Fundulus grandis.  Within each population, CI activity is highly variable among individuals of F. heteroclitus (%CV among individual has a mean of 90% in the five F. heteroclitus populations), and the mean CI activity among populations is significantly different at the latitudinal extremes of the range.  Importantly, Complex I activity is more similar between F. heteroclitus from the southern most population and its sister taxa F. grandis than to northern populations of F. heteroclitus; suggesting evolutionary important differences.  Unexpectedly, activity is higher in southern populations than northern populations.  Mitochondrial density appears to partially compensate for decreased activity in northern individuals.  We suggest that some of variation in CI activity is genetically based, and is being influenced by directional selection.  Yet, this conclusion presents a conundrum:  how can there be so much variation in CI within a population if this variation is biologically important?

 

Phillip Gillette

Advisor: Dr. Andrew Baker

“Genetic variation in thermal tolerance in the coral Pocillopora damicornis and its effects on growth,

photosynthesis and survival”

Coral reef ecosystems worldwide are in decline as a result of climate change and other anthropogenic impacts. Prolonged exposure to extreme high (>32ºC) and low (<20ºC) temperatures typically leads to coral bleaching and/or mortality.  Different coral colonies often show variation in their response, but it is not yet clear whether these differences are the result of genetic factors. In an 8-week study, I investigated the effect of different temperature treatments (20, 26, 30 and 32ºC) on four different genotypes of Pocillopora damicornis, identified using microsatellites.  Corals grew fastest at control temperatures (26ºC, p<0.001), but this effect varied in strength across genotypes. There was 100% mortality by week 6 in the highest temperature (32ºC), and partial mortality of some genets in the 20ºC and 30ºC treatments by week 8.  Quantitative PCR analysis of the algal symbionts (Symbiodinium spp.) in these corals revealed genets 1, 2 and 4 were initially dominated by clade C, while genet 3 was dominated by clade D.  However, when exposed to 30ºC, all genets were dominated by clade D by day 62. Photosynthetic efficiency of symbionts also varied across temperatures and coral host genotype.  Together, these data suggest that coral genotypes vary in their thermal tolerance and growth rates, and that this variation is further influenced by the algal symbiont community. This information may help restoration efforts designed to increase the resilience of coral reefs to climate change by identifying coral genotypes best suited to the prevailing thermal environment.

 

Friday, April 20, 2012

1:00pm

RSMAS campus, S/A 103

Pamela Harris
Administrative Assistant
Marine Biology and Fisheries
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway/SLAB-118
Miami, FL 33149
(305) 421-4176
fax - (305) 421-4600
pharris@rsmas.miami.edu
http://www.rsmas.miami.edu/academics/divisions/marine-biology-fisheries/