Fish-Related Projects
University of Texas Marine Science Institute
Marine Fish Research Program
Recent and Ongoing Projects
(Staff: M. Smith, D. Sabath, I. McCarthy, M. Alvarez)
Scales for Ontogenetic Progress and Biological Clocks: This has been an
ongoing theme in Team Fuiman because of its obvious importance to many other
projects dealing with development in fishes, especially projects that attempt to
compare
species. The problem is to quantify the developmental state of a fish in such a
way that it can be compared the state of
another individual of the same or different species. Given the variety of
developmental programs exhibited by fishes and the
enormous range in developmental rates observed, this has been an especially
challenging topic. Nevertheless, we feel we have
made some progress.
Predation Mortality of Larval Fishes: Peril of the Unfit or the Unfortunate?: This collaboration with Jim Cowan (Dauphin Island Sea Lab, Alabama) is examining the question of whether predation mortality during early life is the result of chance encounters with predators or the predator evasion skills of the larvae. Laboratory assays measure survival skills of individual larvae to determine whether some individuals excel in several skills ("born athletes"). Laboratory results will be incorporated into an individual-based model and simulations will be performed to predict the survival of athletes and non athletes. These predictions will then be tested in field mesocosm trials.
Evaluation of endocrine disrupting chemical effects across multiple levels of biological organization: integration of physiology, behavior, and population dynamics in fishes: This is a collaboration with Peter Thomas and Kenny Rose (Louisiana State University). The aim of the proposed research is to estimate the impacts of several representative endocrine disrupting chemicals (EDCs) on Atlantic croaker (Micropogonias undulatus) populations in marine environments. The overall hypothesis that endocrinological, physiological, morphometric and behavioral biomarkers of reproductive and larva functions in individuals can be modeled to predict the effects of EDCs on croaker population dynamics will be examined by testing the following subhypothesis: (1) EDCs act during several critical reproductive and early life stages of croaker, (2) endocrinological, physiological, morphometric and behavioral responses are reliable predictors of EDC effects on these critical stages, (3) endpoints of critical reproductive and early life stages in individuals can be used to model population effects of EDCs. Specific objectives are to 1) determine the effects of the EDCs on biomarkers of gamete production and gonadal growth; 2) investigate the impacts of the representative EDCs on biomarkers of gamete maturation, fertilization success and larval survival; 3) assess the parental transfer of the EDCs to gametes and offspring; 4) determine the effects of parental exposure to the EDCs on ecological performance skills of larvae; 5) determine the influence of parental exposure to the EDCs on larva metabolism, growth, and development; 6) develop a suite of predictive computer models for scaling individual-level effects of EDCs to fish population response. This integrative, multidisciplinary study involves collaborations between three groups of researchers with expertise in reproductive physiology, endocrine toxicology, bioaccumulation of EDCs by parents and offspring, development, functional morphology, behavioral ecology, and individual-based bridge modeling and population modeling.
Individual
variability in growth rates of red drum (Sciaenops ocellatus) larvae- a
potential cause and behavioral consequences: Assessment of particular traits
that result in higher survival of individual larvae may be important for
predicting the future of a particular cohort. Michael Smith is examining three
such traits and their covariation: egg size, growth rate, and sensorimotor
performance. Individual red drum are reared from eggs to measure variability in
individual growth rates and potential covariation of growth rate with egg and
hatchling size. Then laboratory trials are used to examine the ontogeny of
sensorimotor performance and its covariation with individual growth rates and
egg size. These performance trials will include measurement of routine swimming,
burst responses to acoustic and visual stimuli, and escape behavior in the
presence of a predator. Ontogeny and variability in sensorimotor performance of
both field-collected and laboratory-reared red drum larvae are being studied.
Biomarkers of larva fitness in croaker exposed to pesticides: This is a collaborative project with Peter Thomas' lab. Dan Sabath is following up Cindy Faulkās thesis work using a collection of behavioral assays to determine whether parental exposure to a pesticide has ecologically significant sublethal effects on the larvae they produce. The assays measure foraging and antipredator behavior of Atlantic croaker larvae.
RNA:DNA ratio:
Can it be more than a growth index?: RNA:DNA ratios have been used as an
indicator of nutritional condition and recent growth of larval fishes. Although
it has been hypothesized that high RNA:DNA ratios could be correlated with
decreased mortality under natural conditions, few attempts have been made to
correlate this index with any functional (survival) benefit to individual
larvae. Michael Smith, in collaboration with Sharon Herzka (Joan Holtās lab),
are examining relationships between RNA:DNA ratios and sensorimotor performance.
Performance trials will include videotaping individual routine swimming and
responses to visual and acoustic stimuli.
Effects of temperature and salinity on the interaction between red drum
larvae and a piscine predator: Locomotor and physiological performance of
both predator and prey may be influenced by differences in temperature and
salinity, but the magnitude of the effects may differ for larvae and
larger fishes. This project examines the responsiveness and response
effectiveness of red drum larvae, and the capture success of larger pinfish
under 12 combinations of temperature and salinity to determine relative
importance of these two natural environmental variables to the predatory-prey
interaction.
Potential alarm pheromones in marine fishes: Most ostariophysian fishes (almost all freshwater) have behavioral alarm reactions to chemicals released from epidermal club cells of injured conspecifics. No marine ostariophysians have been tested for such responses. Michael Smith is recording activity levels of a marine ostariophysian, hardhead catfish (Arius felis), in the presence of conspecific skin-extract. Similar experiments are also being performed with the naked goby (Gobiosoma bosc) and darter goby (Gobionellus boleosoma).
Other Projects
Lee A. Fuiman
Weddell
Seal Foraging: Behavioral and Energetic Strategies for Hunting Beneath the
Antarctic Fast-Ice
The primary objective of this study is to investigate the behavioral and
energetic adaptations that enable Weddell seals (Leptonychotes weddellii) to
forage in the Antarctic fast- ice environment. To achieve this goal, we will
examine the underwater behavior, locomotor performance (swimming velocity,
stroke frequency, and three-dimensional movements) and energy metabolism of
Weddell seals during foraging dives. We will test hypotheses on general foraging
strategies, searching behavior, searching mechanics, modes of swimming,
metabolic costs of foraging, and foraging efficiency for different environmental
conditions and prey type.
Strategies
for Cost-Efficient Diving in Marine Mammals
Locomotor activity by diving marine mammals is accomplished while breath-holding
and often exceeds predicted aerobic capacities. Video sequences of freely diving
seals and whales wearing submersible cameras reveal a behavioral strategy that
improves energetic efficiency in these animals. Prolonged gliding (greater than
78% descent duration) occurred during dives exceeding 80 meters in depth.
Gliding was attributed to buoyancy changes with lung compression at depth. By
modifying locomotor patterns to take advantage of these physical changes,
Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This
energy-conserving strategy allows marine mammals to increase aerobic dive
duration and achieve remarkable depths despite limited oxygen availability when
submerged.
Research Update
Team Fuiman - Research Update
Two new people joined Team Fuiman this year. Maria C. Alvarez, winner of the
best poster at last yearās larval fish conference, joined us last summer (1999).
She received her masterās degree at Kyoto University, under Masaru Tanakaās
supervision. She will be working on the effects of environmental xenobiotics on
larval behavior and metabolism for her PhD degree.
Dr. Ian McCarthy came on board last October as a postdoctoral fellow. Ian
received his PhD in Dominic Houlihanās lab in Aberdeen University and most
recently worked at the Glasgow University Field Station on Loch Lomond. He
brings a keen interest in physiological processes to our lab and will be
examining contaminant effects on sciaenid larvae.
For the past few years there have been two main themes of work our lab. One is
the effect of several endocrine disrupting chemicals (EDCs) on a number of
species marine fish larvae. The second is dealing with the assessment of
individual variability in specific traits that might result in higher survival
of larvae as a possible clue for predicting the future of an entire cohort.
We have approached the first research topic in two ways. One is assessing the
effect of parental exposure to different pollutants on the behavioral and
physiological performance of their offspring. For this project we are working
with Atlantic croaker (Micropogonias undulatus). The hypothesis pursued here is
that because of the lipophilic nature of the EDCs tested, maternal exposure to
environmentally realistic levels of these chemicals via food will have an effect
on their progeny. Females loaded with contaminants will transfer significant
levels of these to the growing oocytes through the yolk. During the early larval
stages the yolk is absorbed and this is when the effects of the carried
xenobiotics can be observed. We believe that, although development might be
apparently normal, ecological survival skills will be impaired. For this
purpose, ecological performance, metabolism, growth and development of control
and contaminated larvae are measured. The performance trials include
measurements of routine swimming and burst responses to acoustic and visual
stimuli in order to evaluate their abilities to find food and evade predators.
As for the metabolism and growth evaluation, measurements on oxygen consumption,
RNA/DNA and protein turnover are planned.
Cindy Faulk's master's degree research (1997) showed that the performance of
larvae from parents exposed with DDT was significantly impaired and Dan Sabath's
master's research involves similar experiments using a parental DDE exposure.
Ian McCarthy and Maria C. Alvarez are analyzing the performance of PCB exposed
larvae. Following the same line of experiments, we will be performing studies on
the effects of methyl mercury and 4-nonylphenol parental exposures on larvae. So
far our results show that levels of pollutants considered "safe" do have a
profound effect on the survival skills of larvae.
As part of the study on the variation in traits of individual larvae (in
collaboration with Dr. James H. Cowan, Jr., University of South Alabama), we
were asking the question: "are survivors of a cohort of larval fishes
exceptional individuals in some way, or are they just lucky enough not to
encounter predators at a time in their development when they are highly
vulnerable to predation?" In the laboratory component, doctoral candidate
Michael Smith has been investigating the potential causes and behavioral
consequences of individual variability in growth rates of red drum larvae as
well as larva condition in terms of RNA/DNA ratios. His work can be summarized
as follows:
Michael is examining differences in behavioral performance between fast and slow
growing red drum larvae of the same size and ontogenetic stage. The measures
recorded include routine swimming and burst responses to acoustic and visual
stimuli. He has also performed these behavioral experiments on field-collected
red drum to see if laboratory-reared performance trials are representative of
the abilities of wild fish. The effect of cohort density on red drum growth
variability was examined by rearing red drum individually and in groups for
three weeks and comparing the variance in total lengths of the two treatments.
He found that lengths of individually-reared red drum decreased in variance
while lengths of group-reared larvae increased in variance over time (termed
growth depensation). A significant increase in size variability occurs between
7-15 days posthatching. This increase may have resulted from differential timing
of switching from rotifers to Artemia, but in trials in which only rotifers were
provided as a food source, the increase in variability still occurred. Michael
is also analyzing the variability in egg size. Individual red drum eggs are
measured and incubated until yolk absorption to examine the relationship between
egg and oil globule size (maternal effects) and size of larvae at time of first
feeding. In collaboration with Sharon Herzka (Joan Holtās lab), Michael is
examining relationships between RNA:DNA ratios and behavioral performance. These
behavioral experiments were done with both fast and slow growing red drum larvae
of the same size. Routine swimming speeds were greater for larvae with higher
RNA:DNA ratios, but this trend was only evident in slow growing larvae. While
there was a significant correlation between RNA:DNA and growth rate for slow
growing larvae, there was no significant relationship in fast growers. As a
complementary study, Michael is also developing an individually-based model to
simulate predation mortality on red drum larvae. Specifically, he is examining
three questions: How does individual variability in growth rates influence
survival? Can variability in individual escape performance effect larval
survival in model outcomes? How do temporal shifts in total length variance
influence larval survival?
In the field side of this project, we are working in collaboration with Jonathan
OāNeal (Jim Cowanās lab, University of South Alabama). Jonathan is undertaking
mesocosms experiments to compare the data obtained in the laboratory by Michael
Smith to a more environmentally realistic situation. He has been working on the
idea of growth rate as an indicator of better fitness in larvae. For this, he
raised concurrent cohorts of larvae that were approx. 10 days apart in age, and
waited for them to reach a specific size (approx. 8 mm). In this way the fastest
and the slowest growers (from the younger and older cohort, respectively) could
be tested in the same mesocosm experiment with a single predator fish. In this
experiments, a population of similar sized larvae with different growth rate
histories was tested. Estimates of instantaneous daily mortality of fast and
slow growers were obtained and compared to see if there was any significant
difference. These data are currently being analyzed and compared to results
obtained using individual based modeling to investigate longer-term cumulative
mortality that could not be obtained in the field. Currently, Jonathan is
attempting to screen larvae for particular behavioral traits (namely, routine
swimming speed), separate out fast and slow swimming larvae, and then follow the
same mesocosm procedure in order to see if this behavioral trait is an indicator
of better anti-predator skills leading to a higher probability of survival to
adulthood, as suggested by the laboratory results.
Grace Kilbane (an undergraduate intern from Loyola University) conducted
experiments to determine whether the spectral sensitivity of the red drum
scotopic visual system changed during the larval period. Her results confirmed
those of Brendan Delbos (an undergraduate intern from Southampton College), who
previously showed a dramatic improvement in overall sensitivity when rods began
to appear (Copeia 1998: 936-943). She also found that all stages of larval and
juvenile red drum were least sensitive to wavelengths of 640-630 nm (blues) and
most sensitive to wavelengths of 410-460 nm (reds). Grace doesn't think that's
whey they're called red drum.
Debbie Rosier (undergrad intern from University of Texas at San Antonio) is
conducting several comparative studies on the growth rates of Brachionus
plicatilis fed a number of commercially available rotifer feeds. The aim of her
research is to select the most suitable food to maximize the rotifer production
and rotifer quality in our laboratory.