Biology Theses and Dissertations
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Item STUDIES ON THE GNRH/GTH SYSTEM OF FEMALE STRIPED BASS (Marone saxatilis): EFFECTS OF GNRH AGONJST THERAPY AND COMPARISON OF REPRODUCTIVE ENDOCRINE PARAMETERS BETWEEN WILD AND CAPTIVE FISH(1999) Steven, Colin R.; Zohar, Yonathan; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)In the striped bass (Marone saxatilis), and many other commercially important fish species, captivity results in an inability to complete final oocyte maturation (FOM), ovu lation , and spawning. We hypothesize that this effect is mediated by a disruption of the hypothalamo-pituitary-gonadal (HPG) axis at the level of the gonadotropin -releasing hormones (GnRHs). To confirm this hypothesis research was conducted focused on three objectives: First, to complement the battery of assays previously developed for analysis of the GnRH/GtH system in striped bass, an RNAse protection assay was developed to measure specific expression of the three forms of GnRH in striped bass (salmon GnRH, chicken GnRH-If and seabream GnRH). Secondly, effects of GnRH agonist-induced ovulation on the HPG axis of captive striped bass was examined by comparison of several reproductive endocrine parameters between females sampled at four stages of oocyte development. Finally, differences were examined between the reproductive endocrine status of wild and captive female striped bass. We conclude that sbGnRH is the most important form for the preovulatory release of pituitary GtH-II in striped bass. We suggest that captive females synthesize levels of GnRH mRNA that are comparable to their wild counterparts, however fail to release adequate quantities of bioactive GnRH within the pituitary to stimulate completion of FOM. This data may indicate that regulation of sbGnRH in striped bass occurs via post-transcriptional/ translational mechanisms. Furthermore, the presence of salmon GnRH in the pituitaries of captive fema les may be indicative of a possible role for salmon GnRH in the regulation of FOM.Item Adenyl Cyclase and Its Relationship to Insect Diapause in the European Corn Borer, Ostrinia Nubilalis (Hubner)(1978) Gelman, Dale Berkman; Lockard, J. David; Hayes, Dora K.; Botany and Science Teaching; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)The purpose of this study was to determine if there is a link between adenyl cyclase activity and the diapause condition in the European corn borer, Ostrinia nubilalis. Insects inhabiting those latitudes where cold and warm seasons alternate with one another have evolved mechanisms which allow them to remain dormant (in a state of diapause) during the winter months of the year. Photoperiod, as well as temperature and humidity, has been shown to control the onset, maintenance and termination of insect diapause. In recent years, evidence supporting a role for the cyclic AMP system, including adenyl cyclase, as well as a role for one or more biogenic amines in the pathway between light reception and the neuroendocrine regulation of the insect life cycle and in the multitude of neuroendocrine pathways controlling insect growth and metamorphosis has been accumulating. In light of this evidence, it was decided to investigate the effects of two light regimens, short day (diapausing-inducing) and long day (pupation-inducing), on adenyl cyclase activity of various stages of fifth instar European corn borer larval heads, and to determine the effects of the biogenic amine neurotransmitters, norepinephrine, octopamine, and dopamine on this activity. Adenyl cyclase activity was measured by a modification of the method of Krishna, et al., (1968). A summary of the results follows. In head extracts of fifth instar European corn borer larvae reared under both long day and short day photoperiodic regimens, adenyl cyclase activity in the presence of sodium fluoride increased as the larvae progressed through early, middle and mature stages. In long day larval heads, activity decreased in late prepupae and reached a low in pharate pupae. In contrast, adenyl cyclase activity in short day larval heads peaked in early diapause and then returned to prediapause levels during late diapause. Norepinephrine significantly enhanced adenyl cyclase activity only in early diapause larval head extracts, while octopamine significantly enhanced adenyl cyclase activity in head extracts of late short day mature and early diapause larvae. Dopamine was ineffective as an activator. An analysis of the combined effect of neurotransmitter and developmental stage revealed that in general, a given neurotransmitter in combination with short day larval head extracts resulted in higher adenyl cyclase levels than that neurotransmitter in combination with long day head extracts.Item Interannual and Regional Patterns of Abundance, Growth, and Feeding Ecology of Larval Bay Anchovy (Anchoa Mitchilli) in Chesapeake Bay(2003) Auth, Toby D.; Houde, Edward D.; Marine Estaurine and Environmental Science Program; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Patterns in abundance, growth , and feeding by larval bay anchovy were examined in Chesapeake Bay from 1995-1999 to evaluate factors that contribute to variable recruitments of this abundant fish. The patterns were examined in relation to environmental factors, including hydrography and distributions of prey (zooplankton) and a probable predator (ctenophore). Larval abundances, sizes, feeding incidences, and growth rates varied annually and regionally. Averaged over five years, mean abundances in July decreased by almost two orders of magnitude from the mouth (38.l/m2) to the head (0.6/m) of the Bay, a long a declining salinity gradient. Yearly survey, bay-wide mean abundance varied nearly 10-fold; it was highest in 1998 (42. 7 /m2) and lowest in 1996 (4.6/m2). Feeding incidence was highest in 1998 (23%) and lowest in 1996 (9%), and varied regionally from 27% in the upper Bay to 13% in the mid Bay. Larvae fed predominantly during daylight. The most common prey ingested were copepod eggs and various life stages of calanoid copepods (primarily Acarlia Lonsa). Growth rates of larvae also differed annually and regionally. Mean growth rate was highest in 1998 (0.81 mm/d) and lowest in 1999 (0.68 mm/d), and varied regionally from 0.83 mm/d in the upper Bay to 0.71 mm/din the mid Bay. Zooplankton concentration was positively correlated with larval feeding incidence (r = +0.66) and growth rate (r = +0. 72). Larval feeding incidence was strongly correlated (r = +0.93) and summer larval abundance significantly correlated (r = +0.86) with fall recruitment of young-of-the-year bay anchovy.Item The Feeding Habits of the Toadfish (Opsanus Tau) Based on an Analysis of the Contents of the Stomach and Intestine(1951) Chrobot, Raymond J.; Littleford, Robert A.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Opsanus tau, (Linneaus) - the toadfish, inhabits a vast area along the Eastern Sea Coast of North America. It is found from the coast of Maine to the regions of the West Indies. North of Cape Cod, its occurrence is rather rare. As for the Chesapeake localities, according to previous records the toadfish lives in the muddy bottoms of the oyster regions of the Chesapeake Bay, around the mouth of the Potomac River, and elsewhere in the saltwater regions. Many specimens were collected from many localities around Annapolis, Maryland to the entrance of the Bay by Hildebrand and Schroeder (1927). Studies on the feeding habits of the toadfish have not been very extensive over the past years as reviewed in the literature. Little attention has been given to very detailed analyses of this type because of their lack of economic importance. (Hildebrand and Schroeder, 1927) in their mention of the toadfish state that its principal food appears to consist of crustaceans, with a combination of mollusks, or other fish. Small crabs among the crustaceans appeared most frequently in the food, although shrimp (and in the smaller individuals Amphipods) and Isopods also were present. Almost any kind of offal is eaten, and in places where garbage is thrown overboard, toadfish are almost always present in comparatively large numbers. (Linton, 1901) noted that the alimentary canal is chiefly filled with crustacean and molluscan remains and the bones and scales of fishes. He also noted finding a partly digested toadfish in the stomach of another. (Gudger, 1908) stated that their favorite food is young molting blue crab; any crustacean will do, however, or fish or almost any kind of offal. This investigation was concerned with the feeding habits of Opsanus tau in the Chesapeake Bay in the vicinity of Crisfield, Maryland. A somewhat detailed analysis was made in the determination of the specific type of food that was present in the comparison to what has previously been noted. In correlation with previous accounts of notations made on the feeding habits of the toadfish , a definite relation occurred between the analyses presented here with earlier findings.Item PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE, FOLLICLE STIMULATING HORMONE AND PROLACTIN IN OVARIECTOMIZED, HYSTERECTOMIZED AND INTACT SWINE(1974) Wilfinger, William Walter Jr; Brinkley, Howard J.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)In order to critically evaluate the temporal patterns of plasma luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL); blood samples were collected daily at 0600, 1200, 1800 and 2400 hrs from intact, sham, ovariectomized and hysterectomized Yorkshire sows via indwelling vena caval cannulae. The maximum preovulatory plasma LH concentration in the intact and sham operated swine (mean ±l SD, 7.06±2.40 ng/ml) was reached between 2400 hrs on the first day of estrus (day 0) and 0600 hrs on day 1. Preovulatory LH peaks averaged 28.75±4.76 hrs duration from initial rise from, and return to, a baseline concentration of 1.19±.25 ng/ml plasma. In addition to the preovulatory LH peak, an average of 8.75 luteal phase peaks was observed during each estrous cycle . Approximately 69.5% ·of the luteal phase peaks had an average duration of 12.65±1.79 hrs, an average maximum plasma concentration of 2.29±.55 ng/ml and occurred during days 2 to 17. The remaining luteal phase peaks reached a maximum concentration of 2.86±1.04 ng/ml and occurred during days 2 to 13. The average duration of these luteal phase peaks was 18.61± 3.49 hrs. The largest and most consistent plasma FSH peak in the intact and sham operated swine occurred between days 2 and 3. This postovulatory peak had a duration of 58.17±16.25 hrs and reached an average maximum concentration of 13.14±9.42 ng/ml before returning to a baseline of 4.76± 1.56 ng/ml plasma. The initial rise of the postovulatory FSH peak coincided with the initial rise of the preovulatory LH peak, but did not reach maximum concentration until 2.66±.45 days after the preovulatory LH peak had reached maximum concentration. In some animals, a luteal phase FSH peak occurred between days 8 to 14. The luteal phase FSH peaks had a duration of 18.09±5.36 hrs and an average maximum concentration of 9.76± 3.78 ng/ml plasma. An average of 2.58±1.08 plasma PRL peaks was observed between day 0 and day 2 of the estrous cycle in the intact and sham operated swine. These peaks averaged 20.54±4.02 hrs in duration and reached maximum concentrations of 11.49±2.97 ng/ml before returning to a baseline of 6.54± 1.29 ng/ml plasma. They reached their maximum concentration approximately 9.12±9.84 hrs after the maximum concentration of the preovulatory LH peak had been reached. Larger prolactin peaks occurred during the follicular phase of the estrous cycle. An average of 3.09±1.38 peaks occurred between days 14 and 19.· These peaks had an average duration of 18.98±3.30 hrs and reached a maximum concentration of 14.28±4.27 ng/ml plasma. Shortly after removal of the ovaries (6 to 8 hrs), baseline LH (2.2± .14 ng/ml) and FSH (12.20±2.90 ng/ml) plasma concentrations in the ovariectomized swine were significantly greater (P<.05) than those found in the intact and sham operated animals, but baseline prolactin concentrations (6.70±2.10 ng/ml) were not significantly different (P>.05) from the controls. The temporal patterns of maximum plasma concentrations associated with LH (3.47±.21 ng/ml), FSH (21.43±.82 ng/ml) and PRL (9.32±2.00 ng/ml) peaks were not similar among the ovariectomized animals. Baseline LH (1.12±.34 ng/ml), FSH (5.30±2.09 ng/ml) and PRL (6.05± 1.89 ng/ml) concentrations in the hysterectomized swine were not significantly different (P>.05) from the baseline concentrations in the intact and sham operated animals. Numerous plasma LH peaks (14.30±4.59) were observed during the 20-day collection period. These peaks averaged 19.50 ±1.49 hrs in duration and reached maximum concentrations of 2.63±.23 ng/ ml before returning to baseline. Plasma FSH and PRL peaks averaged 21.00 ±4.51 and 17,69±3.50 hrs in duration and reached maximum concentrations of 8.12±1.95 and 10.18±2.95 ng/ml before returning to baseline. Mean plasma LH concentrations in the intact, sham, ovariectomized and hysterectomized swine were significantly greater at the 2400 hr collections than at the 1800 hr collections. A critical assessment of plasma hormone concentrations is an essential prerequisite to a basic understanding of the physiological mechanisms governing the reproductive process. The descriptive data provided by this study will enable future investigators to design critical experiments to evaluate the physiological importance of these hormone fluctuations, thereby broadening our basic understanding of the mechanisms which govern the reproductive cycle.Item Differences facilitating the coexistence of two sympatric, orb-web spiders, Argiope aurantia Lucas and Argiope trifasciata (Forskal) (Araneidae, Araneae)(1977) Taub, Marilyn Lorraine; Morse, Douglass H.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Two closely-related, sympatric, orb-web spiders, Argiope aurantia and Argiope trifasciata, take prey which differ in size. In accordance with the often-assumed direct relationship between the size of predators and their prey, A. aurantia is larger than A. trifasciata at any single point in time, largely a result of their asynchronous reproductive cycles. The ratio of their sizes exceeds the 1.28 proposed by Hutchinson (1959) for coexistence. Vertical and horizontal differences in their use of the microhabitat also occur and may further reduce the overlap in their use of food or reduce the frequency of interspecific interactions. In this study, vertical stratification of webs occurred only late in the season, with A. aurantia higher than A. trifasciata. These results contrast with those of Enders (1974), probably due to different densities of the two species in our study areas. Experiments show that the differences in the size of prey taken by these Argiope spiders were due, in part, to dissimilarities in the filtering properties of their webs and to differences in the ability of the two species to capture prey of the same relative size. However, the differences were mainly due to the spiders' rejection of a large and different portion of the available prey.Item The Impact of Planktivory on the Life Histories of Estuarine Crabs(1986) Morgan, Steven G.; Reaka, Marjorie L.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Estuarine crabs commonly display two larval dispersal patterns in which larvae are either exported from or retained within estuaries. Explanations for the disparate dispersal patterns are that larvae differ in their susceptibility to predation, which is greater within the estuary than offshore, or in their physiological tolerances to the large temperature and salinity fluctuations of the estuary. Crab larvae which are exported from the estuary survived better in stressful temperature and salinity combinations than those which are retained, and thus the physiological stress hypothesis was rejected. However, exported larvae were more vulnerable to predation by fishes and invertebrates than were retained larvae. The long spines, large body sizes and behavioral responses of retained crab larvae were more effective at deterring predation by two fishes and eleven invertebrates in the laboratory, than were the short spines and small body sizes of exported larvae. Spines generally were more effective against planktivorous fishes than against invertebrates. Spines operated by effectively increasing the size of the larvae and their unpalatability to fishes. Behavioral observations revealed that fishes repeatedly attacked zoeae, but would quickly learn to avoid the noxious prey. The armor of crab larvae enabled them to survive attacks, and fishes repeatedly attempting to swallow long-spined crab larvae frequently would die. Spines did not assist in the flotation or stabilization of crab larvae. Electivities of the three predominant fishes sampled from the Newport River estuary, North Carolina, also were greater for exported than retained species of crab larvae. Predation by larval and juvenile fishes was greater upstream compared to downstream, and greater diurnally than nocturnally. By hatching on nocturnal high tides, larvae rapidly disperse downstream where the probability of predation diminishes. Semiterrestrial crabs hatch on nocturnal spring tides to prevent stranding in tidal creeks. Thus, the hatching rhythms and dispersal patterns of crabs appear to have evolved in concert to transport larvae into coastal waters where the risk of predation is reduced, or to retain larvae within estuaries depending upon the vulnerability of the larva to predation.Item Branched Chain Amino Acids: Requirements and Antagonism in the Male Broiler Chick(1987) Farran, Mohamad Talal; Thomas, Owen P.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Experiments were conducted to study the effect of feeding the branched-chain amino acids (BCAA), leucine (Leu), isoleucine (Ile) and valine (Val) to 7-21 day old male broiler chicks. Using the central composite rotatable design, the results of response surface regression analysis showed that optimum body weight gain (BWG) and feed conversion values (FC) would be obtained with dietary levels of 1.16, 0.81 and 0.90% for Leu, Ile and Val respectively. Chicks fed a Val deficient diet ad libitum exhibited a ricket-like condition which was characterized by a low Ca content in the bone. The value was 134 as compared to 156 and 172 mg/g dry bone for chicks fed a diet deficient in the three BCAAs and a Val supplemented diet respectively. similar results were obtained when equal amounts of the three diets were given to the birds by using pair feeding and force feeding techniques. Although birds fed the Val deficient diet and those pair fed the BCAA deficient diet had similar BWG, bone measurements (bone ash, dry bone, and bone Ca) were significantly lower (p < 0.05) for the Val deficient group. Serum ca (mg/dl) was not significantly different. Excretion of urinary ca, however, was enhanced by feeding a Val deficient diet as compared to the Val supplemented treatment suggesting that a proper ratio of the BCAAs may be required to form the bone matrix which serves as a base for mineral deposition. Feeding a Val deficient diet significantly (p < 0.05) lowered the protein content of the feathers. The value was 82.7% as compared to 85.0 and 88.0% for all BCAA deficient and Val supplemented diets respectively. Valine deficiency also changed the pattern of feather amino acids by increasing the levels of aspartic acid, glutamic acid, methionine, tyrosine, histidine and lysine. Cysteine level, however, was decreased. High dietary Leu(≥ 3.0%) depressed BWG and FC of ad libitum fed birds. When Ile and Val were simultaneously added to the diet the growth rate and FC were similar to the controls. The ketogenic property of Leu was tested by measuring β-OH-butyrate level in the plasma (mg/1) and found to be nonsignificant.Item The Influence of Calcium on the Distribution of the Ring-Necked Pheasant (Phasianus colchicus) in North America(1954) Dale, Frederick Harold; Littleford, Robert A.; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item Morphology and neuromuscular properties of chelae of decapod crustacean species from temperate and tropical populations(1986) Blundon, Jay Arthur; Vermeij, Gerrat J.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)...Both species of decapods showed no seasonal differences in chela muscle performance. Their ability to function over wide ranges of temperatures is undoubtly essential in their successful latitudinal distribution. The difference in the capacity of these two species to rapidly acclimate to cold temperatures is reflected in their natural habitats. C. sapidus lives in estuaries where large short term temperature fluctuations are common. M. mercenaria, a marine coastal subtidal dweller, lives where temperature fluctuations are smaller.