@article{honeycutt_deck_miller_severance_atkins_luckenbach_buckel_daniels_rice_borski_et al._2019, title={Warmer waters masculinize wild populations of a fish with temperature-dependent sex determination}, volume={9}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/s41598-019-42944-x}, DOI={10.1038/s41598-019-42944-x}, abstractNote={AbstractSouthern flounder (Paralichthys lethostigma) exhibit environmental sex determination (ESD), where environmental factors can influence phenotypic sex during early juvenile development but only in the presumed XX female genotype. Warm and cold temperatures masculinize fish with mid-range conditions producing at most 50% females. Due to sexually dimorphic growth, southern flounder fisheries are dependent upon larger females. Wild populations could be at risk of masculinization from ESD due to globally increasing water temperatures. We evaluated the effects of habitat and temperature on wild populations of juvenile southern flounder in North Carolina, USA. While northern habitats averaged temperatures near 23 °C and produced the greatest proportion of females, more southerly habitats exhibited warmer temperatures (>27 °C) and consistently produced male-biased sex ratios (up to 94% male). Rearing flounder in the laboratory under temperature regimes mimicking those of natural habitats recapitulated sex ratio differences observed across the wild populations, providing strong evidence that temperature is a key factor influencing sex ratios in nursery habitats. These studies provide evidence of habitat conditions interacting with ESD to affect a key demographic parameter in an economically important fishery. The temperature ranges that yield male-biased sex ratios are within the scope of predicted increases in ocean temperature under climate change.}, number={1}, journal={Scientific Reports}, publisher={Springer Nature}, author={Honeycutt, J. L. and Deck, C. A. and Miller, S. C. and Severance, M. E. and Atkins, E. B. and Luckenbach, J. A. and Buckel, J. A. and Daniels, H. V. and Rice, J. A. and Borski, R. J. and et al.}, year={2019}, month={Apr} } @article{tipsmark_luckenbach_madsen_kiilerich_borski_2008, title={Osmoregulation and expression of ion transport proteins and putative claudins in the gill of Southern Flounder (Paralichthys lethostigma)}, volume={150}, ISSN={["1531-4332"]}, DOI={10.1016/j.cbpa.2008.03.006}, abstractNote={The southern flounder is a euryhaline teleost that inhabits ocean, estuarine, and riverine environments. We investigated the osmoregulatory strategy of juvenile flounder by examining the time-course of homeostatic responses, hormone levels, and gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein expression after salinity challenge. Transfer of freshwater (FW)-acclimated flounder to sea water (SW) induced an increase in plasma osmolality and cortisol and a decrease in muscle water content, plasma insulin-like growth factor I (IGF-I) and hepatic IGF-I mRNA, all returning to control levels after 4 days. Gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein levels were elevated in response to SW after 4 days. Transfer of SW-acclimated flounder to FW reduced gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein, increased plasma IGF-I, but did not alter hepatic IGF-I mRNA or plasma cortisol levels. Gill claudin-3 and claudin-4 immunoreactive proteins were elevated in FW versus SW acclimated flounder. The study demonstrates that successful acclimation of southern flounder to SW or FW occurs after an initial crisis period and that the salinity adaptation process is associated with changes in branchial expression of ion transport and putative tight junction claudin proteins known to regulate epithelial permeability in mammalian vertebrates.}, number={3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY}, author={Tipsmark, Christian K. and Luckenbach, J. Adam and Madsen, Steffen S. and Kiilerich, Pia and Borski, Russell J.}, year={2008}, month={Jul}, pages={265–273} } @misc{luckenbach_borski_daniels_godwin_2009, title={Sex determination in flatfishes: Mechanisms and environmental influences}, volume={20}, ISSN={["1096-3634"]}, DOI={10.1016/j.semcdb.2008.12.002}, abstractNote={Flounder of the genus Paralichthys exhibit a unique mode of sex determination where both low and high temperatures induce male-skewed sex ratios, while intermediate temperatures produce a 1:1 sex ratio. Male differentiation is thus easily induced in genetic females creating a combination of genetic (GSD) and environmental sex determination (ESD). Since male flounder become reproductively fit at substantially smaller body sizes than females, temperature or other environmental variables that elicit lower growth rates may also influence sex differentiation toward male development. This review covers our current knowledge of sex determination and differentiation in flatfishes including possible adaptive significance of ESD and involvement of factors such as aromatase (cyp19).}, number={3}, journal={SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY}, author={Luckenbach, J. Adam and Borski, Russell J. and Daniels, Harry V. and Godwin, John}, year={2009}, month={May}, pages={256–263} } @article{morgan_murashige_woolridge_luckenbach_watanabe_borski_godwin_daniels_2006, title={Effective UV dose and pressure shock for induction of meiotic gynogenesis in southern flounder (Paralichthys lethostigma) using black sea bass (Centropristis striata) sperm}, volume={259}, ISSN={["0044-8486"]}, DOI={10.1016/j.aquaculture.2006.05.045}, abstractNote={Female southern flounder (Paralichthys lethostigma) grow 2–3 times larger than males. Therefore, all-female production will maximize profit potential for the culture of this species. We have developed protocols to produce all-female southern flounder through induction of meiotic gynogenesis with heterologous sperm of black sea bass (Centropristis striata). Experiments were conducted to establish these practical methods using a total of 40 spawns from 32 broodstock. The first set of experiments determined the UV dose that genetically inactivated black sea bass sperm, yet retained adequate motility for activation of flounder eggs. Milt from several black sea bass was diluted 1:10 with Ringer's solution and UV irradiated with doses ranging from 0–130 J/cm2. Two criteria were utilized to evaluate the UV irradiation effects: percentage of motile sperm and duration of sperm activity. Motility and duration of activity generally decreased with increases in UV dosage. At UV doses greater than or equal to 90 J/cm2, motility was < 1.5%. Fertilization rates were significantly lower at the highest UV dose of 130 J/cm2 but were not different for the other treatments. Hatch rate was highest at 70 J/cm2. A second set of experiments examined appropriate pressure shock protocols for retention of the 2nd polar body in southern flounder eggs after activation with black sea bass sperm. A pressure shock of 8500 psi was initiated at varying times of 1, 2, and 3 min post-fertilization and maintained for 6 min. Eggs that were handled similarly, but not pressure shocked, served as negative controls. Pressure shock applied at either 1 or 2 min post-fertilization resulted in higher rates of hatch and survival. Using these methods, six separate spawns produced offspring that survived through and beyond metamorphosis. The average fertility (± SEM) was 70.9 + 12.8%. Of the fertilized eggs, percentage hatch varied with pressure shock initiation times and ranged from 1.48 + 0.52% (1 min) to 0.61 + 0.11% (3 min). Gynogenetic flounder were sex-reversed to males by high temperature and, upon reaching maturity, expressed motile sperm that resulted in successful fertilization of flounder eggs. These results indicate that the use of UV irradiated sperm from black sea bass for activation of flounder eggs and pressure shock for polar body retention is an effective method to produce gynogenetic offspring.}, number={1-4}, journal={AQUACULTURE}, author={Morgan, Andrew J. and Murashige, Ryan and Woolridge, Christopher A. and Luckenbach, J. Adam and Watanabe, Wade O. and Borski, Russell J. and Godwin, John and Daniels, Harry V.}, year={2006}, month={Sep}, pages={290–299} } @article{tipsmark_luckenbach_madsen_borski_2007, title={IGF-I and branchial IGF receptor expression and localization during salinity acclimation in striped bass}, volume={292}, ISSN={["1522-1490"]}, DOI={10.1152/ajpregu.00915.2005}, abstractNote={The initial response of the IGF-I system and the expression and cellular localization of IGF type-I receptor (IGF-IR) were studied in the gill of a euryhaline teleost during salinity acclimation. Exposure of striped bass ( Morone saxatilis) to hyperosmotic and hypoosmotic challenges induced small, transitory (<24 h) deflections in hydromineral balance. Transfer from freshwater (FW) to seawater (SW) induced an initial decrease in plasma IGF-I levels after 24 h in both fed and fasted fish. There was an overall decrease in liver IGF-I mRNA levels after SW transfer, suggesting that decreased plasma levels may be due to a decline in hepatic IGF-I synthesis. No changes were observed in gill IGF-I mRNA, but SW transfer induced an increase in gill IGF-IR mRNA after 24 h. Transfer from SW to FW induced an increase in plasma IGF-I levels in fasted fish. In fed fish, no significant changes were observed in either plasma IGF-I, liver, or gill IGF-I mRNA, or gill IGF-IR mRNA levels. In a separate experiment, FW-acclimated fish were injected with saline or IGF-I prior to a 24-h SW challenge. Rapid regain of osmotic balance following SW transfer was hindered by IGF-I. Immunohistochemistry revealed for the first time in teleosts that IGF-IR and Na+-K+-ATPase are localized in putative chloride cells at the base of the lamellae, identifying these cells in the gill as a target for IGF-I and IGF-II. Overall the data suggest a hyperosmoregulatory role of IGF-I in this species.}, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Tipsmark, Christian Kolbaek and Luckenbach, John Adam and Madsen, Steffen Sondergaard and Borski, Russell John}, year={2007}, month={Jan}, pages={R535–R543} } @article{luckenbach_murashige_daniels_godwin_borski_2007, title={Temperature affects insulin-like growth factor I and growth of juvenile southern flounder, Paralichthys lethostigma}, volume={146}, ISSN={["1531-4332"]}, DOI={10.1016/j.cbpa.2006.09.024}, abstractNote={Temperature profoundly influences growth of heterothermic vertebrates. However, few studies have investigated the effects of temperature on growth and insulin-like growth factor I (IGF-I) in fishes. The aim of this study was to examine effects of temperature on growth and establish whether IGF-I may mediate growth at different temperatures in southern flounder, Paralichthys lethostigma. In two experiments, juvenile flounder were reared at 23 and 28 degrees C and growth was monitored for either 117 or 197 days. Growth was similar across treatments in both experiments until fish reached approximately 100 mm total length. Body size then diverged with fish at 23 degrees C ultimately growing 65-83% larger than those at 28 degrees C. Muscle IGF-I mRNA, plasma IGF-I, and hepatosomatic index (HSI) were significantly higher in flounder at 23 degrees C, whereas hepatic IGF-I mRNA abundance did not differ with treatment. Muscle IGF-I mRNA was correlated with HSI, while plasma IGF-I was correlated with body size, hepatic IGF-I mRNA, and HSI. These results demonstrate a strong effect of temperature on flounder growth and show that temperature-induced variation in growth is associated with differences in systemic IGF-I and local (i.e., muscle) IGF-I mRNA levels. The results also support the use of plasma IGF-I and HSI as indicators of flounder growth status.}, number={1}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY}, author={Luckenbach, J. Adam and Murashige, Ryan and Daniels, Hany V. and Godwin, John and Borski, Russell J.}, year={2007}, month={Jan}, pages={95–104} } @article{luckenbach_early_rowe_borski_daniels_godwin_2005, title={Aromatase cytochrome P450: Cloning, intron variation, and ontogeny of gene expression in southern flounder (Paralichthys lethostigma)}, volume={303A}, ISSN={["2471-5646"]}, DOI={10.1002/jez.a.198}, abstractNote={Aromatase cytochrome P450 (P450arom) is the enzyme complex responsible for conversion of androgens to estrogens in vertebrates. Consequently, in some fishes its activity appears critical to ovarian differentiation. Southern flounder (Paralichthys lethostigma) is a commercially important flatfish in which females grow larger than males and sex determination is temperature sensitive. Through cloning of the P450arom gene in ovary and quantitative reverse transcription-polymerase chain reaction, we developed a biomarker for early female differentiation in southern flounder. The deduced amino acid sequence for southern flounder P450arom is similar to other teleosts. Comparison of P450arom intron sequences from fish of different populations revealed substantial inter-individual variation. Adult ovary and spleen exhibited high levels of P450arom mRNA, while P450arom mRNA was only weakly detected in testes. Brain, liver, intestine, kidney, gill, muscle, and heart showed little or no P450arom mRNA expression. Gonads of wild and hatchery-produced juvenile flounder of sizes spanning the period of sex differentiation initially exhibited low levels of P450arom mRNA followed by increases in some individuals and bifurcation into two clearly segregated groups (i.e., putative males and females) beginning at approximately 65 mm in total length. Gonadal histology confirmed predictions of sex based on P450arom expression in juvenile flounder, demonstrating that the patterns of P450arom expression observed relate to sex-specific differentiation. This research represents a unique approach to assessing sex differentiation in a natural population, and a powerful technique for better understanding mechanisms of flounder sex determination and rapidly defining conditions for controlling sex for aquaculture.}, number={8}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY}, author={Luckenbach, JA and Early, LW and Rowe, AH and Borski, RJ and Daniels, HV and Godwin, J}, year={2005}, month={Aug}, pages={643–656} } @article{cruz_brown_luckenbach_picha_bolivar_borski_2006, title={Insulin-like growth factor-I cDNA cloning, gene expression and potential use as a growth rate indicator in Nile tilapia, Oreochromis niloticus}, volume={251}, ISSN={["1873-5622"]}, DOI={10.1016/j.aquaculture.2005.06.039}, abstractNote={IGF-I is a mitogenic polypeptide that is an important regulator of growth in fish. The potential of IGF-I mRNA abundance as a rapid growth indicator in the Nile tilapia, Oreochromis niloticus, was evaluated. Hepatic IGF-I cDNA was isolated and partially cloned. The partial sequence having 539 bases encodes for the signal peptide, mature protein and a portion of the E domain. The deduced 68 amino acid sequence for mature IGF-I showed 84–90% and 77–79% sequence identity with fish and mammalian counterparts, respectively. The deduced amino acid sequence for domains B and A was most conserved (93–97%) relative to other fishes. A sensitive TaqMan real time qRT-PCR assay for O. niloticus was developed based on the mature IGF-I peptide for measures of hepatic IGF-I mRNA levels. Hepatic IGF-I mRNA levels were found to be significantly correlated with growth rate of fish reared under different feeding regimes and temperature conditions. Higher feed consumption and water temperature produced faster-growing fish and increased hepatic IGF-I mRNA expression. These findings suggest that hepatic-derived IGF-I plays a key role in controlling growth in O. niloticus and indicates that IGF-I mRNA quantification could prove useful for the rapid assessment of growth rate in this species.}, number={2-4}, journal={AQUACULTURE}, author={Cruz, EMV and Brown, CL and Luckenbach, JA and Picha, ME and Bolivar, RB and Borski, RJ}, year={2006}, month={Feb}, pages={585–595} } @article{luckenbach_sullivan_2004, title={Effective GnRHa dose and gamete ratio for reproduction of southern flounder, Paralichthys lethostigma (Jordan and Gilbert 1884)}, volume={35}, ISSN={["1365-2109"]}, DOI={10.1111/j.1365-2109.2004.01168.x}, abstractNote={Aquaculture ResearchVolume 35, Issue 15 p. 1482-1486 Effective GnRHa dose and gamete ratio for reproduction of southern flounder, Paralichthys lethostigma (Jordan and Gilbert 1884) J Adam Luckenbach, J Adam Luckenbach Department of Zoology, North Carolina State University, Raleigh, NC, USASearch for more papers by this authorCraig V Sullivan, Craig V Sullivan Department of Zoology, North Carolina State University, Raleigh, NC, USASearch for more papers by this author J Adam Luckenbach, J Adam Luckenbach Department of Zoology, North Carolina State University, Raleigh, NC, USASearch for more papers by this authorCraig V Sullivan, Craig V Sullivan Department of Zoology, North Carolina State University, Raleigh, NC, USASearch for more papers by this author First published: 06 September 2004 https://doi.org/10.1111/j.1365-2109.2004.01168.xCitations: 3 Correspondence: C V Sullivan, Department of Zoology, North Carolina State University, Raleigh, NC 27695-7617, USA. E-mail: craig_sullivan@ncsu.edu Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume35, Issue15December 2004Pages 1482-1486 RelatedInformation}, number={15}, journal={AQUACULTURE RESEARCH}, author={Luckenbach, JA and Sullivan, CV}, year={2004}, month={Dec}, pages={1482–1486} } @article{luckenbach_godwin_daniels_beasley_sullivan_borski_2004, title={Induction of diploid gynogenesis in southern flounder (Paralichthys lethostigma) with homologous and heterologous sperm}, volume={237}, ISSN={["1873-5622"]}, DOI={10.1016/j.aquaculture.2004.05.005}, abstractNote={Effective methods for induction of diploid gynogenesis in North American flounder of the genus Paralichthys are needed to initiate monosex culture, which will allow growers to take advantage of the more rapid growth and larger size attained by females. To test methods for inducing diploid gynogenesis in southern flounder (Paralichthys lethostigma) using homologous sperm, four treatments, named for their expected outcome, were employed: haploid, diploid, triploid, and gynogenetic diploid. Diploid gynogenesis was induced by activating egg development with UV-irradiated flounder sperm (70 J/cm2) for 3–4 min in seawater, and then subjecting the eggs to cold shock in 0–2 °C seawater for 45–50 min. Cold shock was used to prevent extrusion of the second polar body. Control treatments omitted one or more of these steps to separately assess the effectiveness of UV irradiation and cold shock. Larvae were observed for physical abnormalities and then histologically processed for ploidy determination. Haploid larvae exhibited abnormal external morphology while diploid, gynogenetic diploid, and triploid larvae showed normal morphologies. Cross-sectional areas of erythrocyte nuclei were measured for larvae in each treatment group and significant differences were found. Nuclear areas for treatment groups corresponded to predicted ploidy (triploid>diploid>haploid) and did not differ between normal diploid controls and gynogenetic diploids. These results suggest that the procedures of sperm irradiation and egg cold shock successfully generated gynogenetic diploids. Due to the low volumes of semen produced by male flounder, and to eliminate any potential genetic contribution by homologous sperm, activation of flounder eggs with heterologous sperm was also investigated. Induction of diploid gynogenesis was successful when flounder eggs were fertilized with irradiated (50 J/cm2) sperm from striped mullet (Mugil cephalus), and then cold shocked. This work provides procedures for induction of diploid gynogenesis in southern flounder using homologous and heterologous sperm, and validates a method for verification of ploidy in larval fish.}, number={1-4}, journal={AQUACULTURE}, author={Luckenbach, JA and Godwin, J and Daniels, HV and Beasley, JM and Sullivan, CV and Borski, RJ}, year={2004}, month={Aug}, pages={499–516} } @article{godwin_luckenbach_borski_2003, title={Ecology meets endocrinology: environmental sex determination in fishes}, volume={5}, ISSN={["1525-142X"]}, DOI={10.1046/j.1525-142X.2003.03007.x}, abstractNote={Van Valen (1973) characterized evolution as the control of development by ecology. Sex determination in fishes provides some clear examples of this “control” in operation. Teleost fishes show a remarkable variety of sex determination and differentiation patterns. These range from systems in which sex is determined by sex chromosomes, as in birds and mammals, to simultaneous hermaphrodites that alternate spawning as a female and male on a second to second basis. This extraordinary flexibility may result from a combined lack of developmental constraint on reproductive structures in many lineages and selection for sexual lability in the face of environmental unpredictability. This review addresses environmental influences on sex determination and differentiation in fishes. There is a variety of documented environmental influences on sex determination (ESD) in fishes. We focus here on two classes of examples where the key environmental cues are of clear ecological relevance, the effects appear especially likely to be important as a normal part of the life history, and where there is evidence suggesting the sexual patterns observed represent adaptations that increase individual fitness. These classes are sex determination that is controlled by social interactions (behavioral sex determination [BSD]) (Crews 1993) and temperaturedependent sex determination (TSD). Sex determination controlled by social influences can occur before or after sexual maturation but appears to maximize the expected reproductive success of individuals in both cases. Here we first address BSD and then TSD in fishes. For each pattern of sex determination, we discuss selection pressures that appear to favor these patterns, examples of each, and what is known regarding the underlying physiological mechanisms. For more comprehensive and general reviews of patterns and mechanisms of sex determination in fishes, the reader is referred to several excellent reviews (Nakamura et al. 1998; Baroiller et al. 1999; Baroiller and D’Cotta 2001; Piferrer 2001). The major focus in studies of physiological mediation of teleost sex determination is what is referred to by endocrinologists as the hypothalamo-pituitary-gonadal (HPG) axis (Fig. 1). This axis consists primarily of hypothalamic neurosecretory neurons producing gonadotropin-releasing hormone (GnRH), gonadotropins produced in and released from the pituitary gland (GtH I and GtH II), and the gonad as the major site of steroid biosynthesis with its steroid metabolizing enzymes, steroid hormone receptors, and a variety of other proteins that mediate steroid hormone action. One steroid biosynthetic enzyme that has been a particularly fruitful focus in correlative and manipulative studies of vertebrate sex determination is cytochrome P-450 aromatase. This enzyme catalyzes the conversion of androgens to estrogens (primarily testosterone to estradiol-17 ). Aromatase expression correlates with female determination in a variety of vertebrates, and aromatasespecific antagonists can block female development in fishes, amphibians, reptiles, and birds (Elbrecht and Smith 1992; Lance and Bogart 1992; Crews et al. 1994; Wennstrom and Crews 1995; Kitano et al. 1999; D’Cotta et al. 2001). Estradiol-17 plays a central role in female reproductive physiology in fishes, whereas the androgen 11-ketotestosterone (11-KT) is crucial to gamete maturation and the expression of secondary sexual characteristics in males (Borg 1994; Brantley et al. 1993). Importantly, testosterone levels often do not differ between male and female fishes or are higher in females (Borg 1994). Because of the central role of aromatase in the biosynthesis of estrogens, it will be a focus in consideration of mechanisms by which environmental information leads to sex determination responses. More generally, our understanding of vertebrate sexual function indicates the HPG axis plays the key role in transducing environmental information into gonadal determination, differentiation, and maturation events. A general theme of this review is where and how this transduction may occur in the HPG axis.}, number={1}, journal={EVOLUTION & DEVELOPMENT}, author={Godwin, J and Luckenbach, JA and Borski, RJ}, year={2003}, pages={40–49} } @article{luckenbach_godwin_daniels_borski_2003, title={Gonadal differentiation and effects of temperature on sex determination in southern flounder (Paralichthys lethostigma)}, volume={216}, ISSN={["0044-8486"]}, DOI={10.1016/S0044-8486(02)00407-6}, abstractNote={Southern flounder (Paralichthys lethostigma) support valuable North American fisheries and show great promise for aquaculture. Because females grow faster and reach larger adult sizes than males, monosex culture of females is desirable for commercial operations. A detailed understanding of sexual development and its timing is critical to control sex and optimize culture. Structural and cellular sex-distinguishing markers were identified histologically, and then used to describe ovarian development in female and testicular development in male flounder. In presumptive ovaries of southern flounder, development of an ovarian cavity first occurs in fish ranging from 75 to 100 mm total length (TL). This is considerably delayed relative to that observed in the Japanese congener, Paralichthys olivaceus, where an ovarian cavity is seen in fish as small as 40 mm TL. The smallest southern flounder that possessed primary oocytes in the early perinucleolus stage was 115 mm TL. In presumptive testes, the formation of seminiferous tubules first occurs in fish of approximately 100 mm TL. Spermatogonia remained quiescent until most fish were over 100 mm TL. Overall, gonads from southern flounder greater than 120 mm TL commonly possess gonial cells undergoing meiosis, clearly differentiating sex. The effect of temperature on sex determination in southern flounder was addressed in a separate experiment. Juvenile southern flounder were grown at 18, 23, or 28°C for 245 days. High and low temperatures induced phenotypic sex reversal in juvenile southern flounder, producing a higher proportion of males (96% males at high temperature, P<0.001, 78% males at low temperature, P<0.01). Raising southern flounder at the midrange temperature held sex ratios close to 1:1. Sex ratios from these trials suggest that southern flounder possess a temperature-sensitive mechanism of sex determination similar to that shown for P. olivaceus, but possibly shifted towards warmer temperatures. These findings indicate that sex differentiation in southern flounder is distinguishable in most fish by 100–120 mm TL and that sex determination is sensitive to temperature. This information is critical to the development of strategies to maximize the number of faster-growing females for commercial flounder culture.}, number={1-4}, journal={AQUACULTURE}, author={Luckenbach, JA and Godwin, J and Daniels, HV and Borski, RJ}, year={2003}, month={Feb}, pages={315–327} } @article{luckenbach_godwin_daniels_borski_2002, title={Optimization of North American flounder culture: a controlled breeding scheme.}, volume={33}, number={1}, journal={World Aquaculture}, author={Luckenbach, J. A. and Godwin, J. and Daniels, H. V. and Borski, R. J.}, year={2002}, pages={40–4569} }