Browsing by Subject "Callinectes sapidus"

Reactive oxygen species (ROS) are produced endogenously in all aerobes and are induced by environmental stressors. ROS oxidize and disable essential cellular components such as DNA, proteins, and lipid membranes. Exposure to metals, polycyclic aromatic hydrocarbons (PAHs), and some pesticides can induce oxidative stress in marine invertebrates. All aerobic organisms have a network of antioxidants and enzymes to quench ROS and prevent oxidative damage. This dissertation examines antioxidant and oxidative stress biomarkers in endemic molluscs and crabs from two natural extreme environments: deep-sea hydrothermal vents in the Lau and North Fiji Basin, and cold seeps in the Gulf of Mexico. In addition, the acute toxicity and sub-lethal effects of four insecticides and an herbicide are examined in the estuarine blue crab, Callinectes sapidus. Blue crabs are North Carolina's most important fishery species and are frequently found in agricultural drainage ditches, an example of an anthropogenic extreme environment.

Total glutathione, catalase, superoxide dismutase, and lipid peroxidation levels were of the same respective order of magnitude in the two vent gastropods, Alviniconcha sp. and Ifremeria nautilei, and vent mussel, Bathymodiolus brevior. These biomarkers activities were similar to those from previous reports on Mid-Atlantic Ridge mussels, except for ~100-fold higher lipid peroxidation levels among Lau molluscs. Principal component analysis (PCA) of mollusc tissue-specific biomarker levels grouped individuals by species rather than by site.

Biomarker levels in the seep mussels Bathymodiolus childressi, B. brooksi, and B. heckerae were similar across species except for elevated foot and gill cytosolic SOD in mussels from MC-640 compared to those from AC-645. PCA of seep mussel biomarker levels differentiated by species with B. childressi isolated from B. brooksi and B. heckerae. The addition of B. brevior biomarker data to the PCA showed them grouping around B. brooksi and B. heckerae. Bathymodiolus childressi is ancestral to the other species and contains only methanotrophic endosymbionts. Whether symbionts play a role in alleviating possible toxic conditions remains unknown.

Pesticides were acutely toxic to blue crabs in the order of Lambda-cyhalothrin > imidacloprid ≈ aldicarb > acephate ≈ Roundup® (glyphosate). Megalopae were almost always more sensitive to pesticides than early stage juveniles. Commercial formations of pesticides generally showed similar toxicity to active ingredients alone. Exposure to LC₂₀ levels of acephate, aldicarb, imidacloprid and Roundup significantly increased the frequency of juvenile mortality after molting. There was no significant change in total glutathione or lipid peroxidation of exposed megalopae. Lambda-cyhalothrin-, imidacloprid-, and aldicarb-based products have the potential to cause acute toxicity and molting-related mortality in shallow creeks and ditches.

This dissertation investigated spawning biology of female blue crabs, Callinectes sapidus. Females mate following the terminal molt and undertake a spawning migration seaward, producing multiple clutches of larvae. To examine lifetime reproductive potential of female crabs, individual crabs were confined in the field from terminal molt to death. Crabs produced up to 7 clutches over 1-2 spawning seasons and survived up to 394 d after the terminal molt. Time to first clutch and time between clutches were positively correlated with carapace width and best described by degree-days. Size at maturity was negatively correlated with water temperature on the day of the terminal molt. Most measurements of clutch quality and larval fitness were similar for all clutches. The percentage of embryos developing normally decreased 40% from clutch 1 to clutch 4 and clutch volume decreased 50% from clutch 1 to clutch 5. Thus, most of a crab's reproductive output is from the first few clutches.

Using swimming and abdominal pumping assays, the roles of pheromones in larval release and migratory behavior were investigated. Following delivery of egg extract, bradykinin (a pheromone mimic), and trypsin (an enzyme that generates peptide pheromones), ovigerous crabs responded with increased abdominal pumping, indicating that peptide pheromones stimulate larval release in blue crabs. Ovigerous crabs responded with increased swimming following delivery of egg extract, but not following delivery of a peptide pheromone mimic or an enzyme that produces peptide pheromones. These results suggest that some substance generated from the egg mass stimulates vertical swimming, but that peptides alone do not stimulate swimming. A blend of molecules, possibly including sugars, may be the cue that stimulates swimming behavior.

Endogenous rhythms in vertical swimming, a mechanism underlying migration in tidal estuaries, were examined in the laboratory under constant conditions in juvenile females, recently-molted females, and females with mature ovaries from Beaufort, NC. Rhythms were variable in each stage, though circatidal rhythms consistent with ebb tide transport were observed in juvenile females and recently-molted females. Crabs with mature ovaries typically swam around the time of high tide. Rhythms were also examined for ovigerous females collected from estuaries with three different tidal regimes: semi-diurnal, diurnal, and non-tidal. Crabs from the tidal estuaries had circatidal or circalunidian swimming rhythms with period lengths corresponding to the tidal period of their home estuary. Swimming occurred primarily on ebb tide. Crabs from the non-tidal estuary had a circadian rhythm of vertical swimming around the time of sunset. Such a rhythm has no obvious migratory significance and migration likely takes place though another mechanism.

Swimming behavior was also examined in the field in one non-tidal site and three tidal sites. Crabs were tethered in the field and swimming was monitored using archival pressure tags. Crabs tethered in the non-tidal site did not swim, possibly due to the lack of necessary environmental cues. Crabs at the tidal sites swam primarily on ebb tides. Swimming was greatest at the deepest site, which also had the strongest currents. This site is known to be a migratory area for spawning blue crabs. Decreased swimming behavior was observed at the two shallower sites, including one site that is known to be habitat for all stages of blue crabs. These results indicate that swimming behavior is variable among different areas in a single estuary. In areas where swimming is reduced, crabs may continue migrating seaward by walking or may spend additional time in that area to forage. Within each site, peak swimming generally occurred during the time of the most rapid decrease in water level, suggesting that hydrostatic pressure may serve as a cue for swimming.

Mark-recapture studies were conducted in three rivers (North River, South River, Adams Creek) in eastern North Carolina, and recently-molted female crabs were tagged to ensure a relatively constant time since molting. Most crabs traveled relatively short distances and were recaptured before producing a clutch of eggs. Individuals that moved substantial distances typically moved down-estuary. The Adams Creek canal, connecting Adams Creek with the Newport River estuary, functioned as a migratory corridor, as crabs from both Adams Creek and South River migrated down the canal, presumably using ebb tide transport. Many of the crabs that migrated down the canal into the Newport River were recaptured while ovigerous. Results of this study support the hypothesis that rapid long-distance migratory movements do not begin until production of the first clutch of eggs, though some down-estuary movement takes place by prior to production of the first clutch of eggs.

Female blue crabs mate following the terminal molt and begin moving seaward soon thereafter by walking and swimming. Once the appropriate salinity (> 22 ppt) is reached, the first clutch of eggs is produced and migration rate rapidly increases. Blue crab spawning biology should be similar throughout the range of the species. After taking latitudinal temperature variation and other local variables into account, results presented here should be applicable not only to blue crabs in North Carolina, but in other areas as well.