Publications (3)4.72 Total impact
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Article: Differential and gonad stage-dependent roles of kisspeptin1 and kisspeptin2 in reproduction in the modern teleosts, morone species.
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ABSTRACT: Kisspeptin is an important regulator of reproduction in many vertebrates. The involvement of the two kisspeptins, Kiss1 and Kiss2, and their receptors, Gpr54-1 and Gpr54-2, in controlling reproduction was studied in the brains of the modern teleosts, striped and hybrid basses. In situ hybridization and laser capture microdissection followed by quantitative RT (QRT)-PCR detected coexpression of kiss1 and kiss2 in the hypothalamic nucleus of the lateral recess. Neurons expressing gpr54-1 and gpr54-2 were detected in several brain regions. In the preoptic area, gpr54-2 was colocalized in GnRH1 neurons while gpr54-1 was expressed in cells attached to GnRH1 fibers, indicating two different modes of GnRH1 regulation. The expression of all four genes was measured in the brains of males and females at different life stages using QRT-PCR. The levels of kiss1 and gpr54-1 mRNA, the latter being expressed in minute levels, were consistently lower than those of kiss2 and gpr54-2. While neither gene's expression increased at prepuberty, all were dramatically elevated in mature females. The levels of kiss2 mRNA increased also in mature males. Kiss1 peptide was less potent than Kiss2 in elevating plasma luteinizing hormone levels and in up-regulating gnrh1 and gpr54-2 expression in prepubertal hybrid bass in vivo. In contrast, during recrudescence, Kiss1 was more potent than Kiss2 in inducing luteinizing hormone release, and Kiss2 down-regulated gnrh1 and gpr54-2 expression. This is the first report in fish to demonstrate the alternating actions and the importance of both neuropeptides for reproduction. The organization of the kisspeptin system suggests a transitional evolutionary state between early to late evolving vertebrates.Biology of Reproduction 03/2012; 86(6):177. · 4.01 Impact Factor -
Article: Effects of Phase‐Shifted Photoperiod Regimes on Oocyte Growth and Hormonal Profiles in Female Striped Bass Morone saxatilis
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ABSTRACT: — The use of 12–mo long, but phase-shifted advanced and delayed photoperiod cycles in the regulation of the reproductive cycle was investigated in captive-reared female striped bass Morone saxatilis during the 3-yr study in an attempt to control the timing of sexual maturation under simulated photoperiod conditions. Phase-shifted photoperiod cycles did not induce a full shift in oogenesis during the first year cycles, but did in the following years. Spawning time, indicated by maximum oocyte diameters, was advanced up to 4 mo in females maintained under the phase-shifted advanced photoperiod, and delayed up to 4 mo when they exposed to the phase-shifted delayed photoperiod, compared to the natural spawning time in Spring (March-May). Phase-shifted photoperiod regimes shifted the profiles of plasma testosterone (T) and estradiol (E2), corresponding to the shift of oogenesis in the respective groups. Significant increases in T and E2 levels occurred during the vitellogenic phase, and these levels peaked before the occurrence of maximum oocyte diameters. The studies demonstrate that phase-shifted photoperiod regimes can be used to control oogenesis, and have implications for ensuring the year-round supply of mature female striped bass, particularly in domesticated striped bass.Journal of the World Aquaculture Society 04/2007; 33(3):358 - 368. · 0.71 Impact Factor -
Article: Large-scale juvenile production of the blue crab Callinectes sapidus
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ABSTRACT: Rearing experiments and mass production of blue crab Callinectes sapidus juveniles were carried out as the first step in a feasibility study of blue crab stock enhancement in the Chesapeake Bay. During February through September 2002, four culture cycles were conducted with C. sapidus seed obtained from photoperiod-manipulated broodstock. A feeding protocol for early life stages, as well as for juvenile crabs, was established based on microalgae, rotifers, Artemia nauplii, and off-the-shelf diets. Developmental patterns of the different life stages were studied and growth and development kinetic curves were established. The captive rearing process was divided into two phases: (1) zoea 1–zoea 8/megalopa and (2) zoea 8/megalopa to 15–30 mm crab juveniles. Each of the phases was accomplished in both open system and recirculated system (RS). Different larval (zoea 1) stocking densities were tested. Within the examined range (40–110 individuals/l), no negative correlation was found for high density. Maximum survival to the zoea 8/megalopa stage was 74% at 95 larvae/l and the average was 30%. Cannibalism was found to be the main cause for blue crab mortality during the second rearing phase. In an effort to reduce the prevalence of cannibalism, experiments providing different shelter substrates, performing size grading, and decreasing stocking density were conducted. During this phase (zoea 8/megalopa until C2–C4), 57% survival was obtained in mass production tanks, using a shelter substrate of snow fence nets and stocking tanks with 2.5 individuals/l. Increasing stocking density by 16-fold (39 individuals/l) and doubling the shelter density resulted in production of about 3000 juvenile crabs/m3, although the survival rate dropped to 7.5% (or 7.6-fold). Additional studies are suggested to determine the tradeoff between survival and crab output, which in turn will establish the economic feasibility of the rearing operations. Cumulatively in the four culturing cycles, 40,000 juveniles were produced, of which 25,000 were individually tagged and experimentally released to the wild. This study is the first to mass-produce both postlarvae and juvenile blue crabs in captivity.Aquaculture.
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2012
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University of Maryland, Baltimore County
Baltimore, MD, USA
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