Jennifer Hand
Research Summary:
I investigated hatching efficiency (HE) and hatchling growth during July through September of 2006 of an exotic population of P. insularum in Horsepen Bayou, Texas. The specific objectives of my project were to (1) determine egg clutch HE (2) examine the influence of temperature on egg clutch HE (3) compare egg clutch HE in Horsepen Bayou to HE data obtained from laboratory based studies and (4) investigate the effects of salinity on the growth and development of hatchlings in Horsepen Bayou.
To determine HE in the field, I constructed a device that enclosed
egg clutches on vegetation enabling them to be counted after hatching.
To examine the influence of temperature on HE, I sheltered half of the
egg clutches with shade cloth. I hypothesized that higher temperatures
would yield higher HE values, and that HE in the field would be higher
than values obtained from HE studies conducted under lab conditions.
Overall, mean egg clutch HE in the field was 70.7% ± 25.5% SD, twice as high as reported laboratory studies (31.4% ± 34.9% SD). Furthermore, egg clutches that were sheltered had a significantly lower HE (63.1% ± 28.5% SD versus 78.4% ± 19.9%
SD).
To investigate the effects of salinity on hatchling growth, I constructed
traps to contain live hatchlings at three different sites in the bayou
for six weeks. I measured snail operculum width to quantify growth. I
hypothesized that hatchlings exposed to higher salinity ranges would
grow less than those exposed to lower salinity ranges. Unexpectedly,
mean snail operculum width was the largest ( 8.1 mm ± 1.3 mm SD) at the high salinity site near the mouth (up to 6 ppt), and the least (2.2 mm ± 0.17
mm SD) at the low salinity site further upstream (typically 0 ppt). I
believe this anomaly resulted from sediment differences between the study
sites.
My research project provided the first examination of egg clutch HE and hatchling growth for P. insularum in the field. Knowledge gained from this research could aid in population estimates in future studies. Information on the basic biology of this species and its reproductive output could also provide insight into effective management strategies.
Where I've been and Where I'm going:
I gained invaluable experience during my research through coordinating
and conducting a large project on my own, statistical analyses, and field
techniques. However, one of the most essential aspects of my project
involved collaboration. I would not have been able to accomplish my research
goals without working with all types of individuals and groups ( e.g.,
universities such as Southwestern, state agencies, a non-profit organization,
co-workers, etc.).
I completed my Master of Science in Environmental Biology at the University
of Houston Æ Clear Lake in December of 2006. I currently work at NASA
(JSC in Houston) in the Toxicology Division.
Feel free to email me