title: Optimising reproductive induction in yellowbelly flounder (Rhombosolea leporina): Evaluating GnRHa dosage and non-invasive gonadal assessment

authors: Colthorpe, Adam

subjects: aquaculture

abstract: This study investigates two complementary tools to address reproductive dysfunction in wild-caught yellowbelly flounder (Rhombosolea leporina), a key bottleneck in the species’ aquaculture development. First, the effects of varying doses of gonadotropin-releasing hormone analogue (GnRHa) on ovarian development and expression of gonadal cyp19a1a, a gene encoding aromatase, critical for 17β-estradiol synthesis were quantified at short-term timepoints. A single injection of 50 or 100 µg/kg induced transient upregulation of cyp19a1a by Day 1 post-treatment (log₂ fold-changes of +2.38 and +2.65, respectively), while the 25 µg/kg and control groups showed downregulation (−0.53 and −0.07) relative to Day 0 baselines. However, expression declined significantly in all groups by Day 5, including a drop in the 100 µg/kg group to −0.68 (p = 0.03), indicating a brief stimulatory window likely insufficient to sustain steroidogenic activity or promote meaningful oocyte development. These findings support the need for sustained-release hormone systems or improved broodstock staging to enhance treatment efficacy. 

Second, a novel, non-invasive Visual Gonadosomatic Index (VGSI) was evaluated to minimise handling stress while classifying reproductive condition and suitability for hormone treatment. Two metrics were developed using backlit imaging of the ventral gonads: gonad area relative to body area (Size GSI) and gonad length relative to body length (Length GSI). While neither metric correlated strongly with oocyte diameter or histological stage, Length GSI showed a modest but significant association with oocyte development (R² = 0.1937, p = 0.009), and both indices were positively associated with cyp19a1a expression (Size GSI: R² = 0.5045, p = 0.021; Length GSI: R² = 0.3408, p = 0.076). These results suggest VGSI may provide a coarse proxy for reproductive development, though further refinement and validation are required. 

Together, these findings represent the first report of ovarian cyp19a1a expression in R. leporina and lay the groundwork for integrated hormonal and imaging-based strategies to improve reproductive control in this culturally and economically significant flatfish.

text: Optimising reproductive induction in yellowbelly flounder (Rhombosolea leporina): Evaluating GnRHa dosage and non-invasive gonadal assessment This study investigates two complementary tools to address reproductive dysfunction in wild-caught yellowbelly flounder (Rhombosolea leporina), a key bottleneck in the species’ aquaculture development. First, the effects of varying doses of gonadotropin-releasing hormone analogue (GnRHa) on ovarian development and expression of gonadal cyp19a1a, a gene encoding aromatase, critical for 17β-estradiol synthesis were quantified at short-term timepoints. A single injection of 50 or 100 µg/kg induced transient upregulation of cyp19a1a by Day 1 post-treatment (log₂ fold-changes of +2.38 and +2.65, respectively), while the 25 µg/kg and control groups showed downregulation (−0.53 and −0.07) relative to Day 0 baselines. However, expression declined significantly in all groups by Day 5, including a drop in the 100 µg/kg group to −0.68 (p = 0.03), indicating a brief stimulatory window likely insufficient to sustain steroidogenic activity or promote meaningful oocyte development. These findings support the need for sustained-release hormone systems or improved broodstock staging to enhance treatment efficacy. 

Second, a novel, non-invasive Visual Gonadosomatic Index (VGSI) was evaluated to minimise handling stress while classifying reproductive condition and suitability for hormone treatment. Two metrics were developed using backlit imaging of the ventral gonads: gonad area relative to body area (Size GSI) and gonad length relative to body length (Length GSI). While neither metric correlated strongly with oocyte diameter or histological stage, Length GSI showed a modest but significant association with oocyte development (R² = 0.1937, p = 0.009), and both indices were positively associated with cyp19a1a expression (Size GSI: R² = 0.5045, p = 0.021; Length GSI: R² = 0.3408, p = 0.076). These results suggest VGSI may provide a coarse proxy for reproductive development, though further refinement and validation are required. 

Together, these findings represent the first report of ovarian cyp19a1a expression in R. leporina and lay the groundwork for integrated hormonal and imaging-based strategies to improve reproductive control in this culturally and economically significant flatfish.

year: 2025

title: Playing right: Some virtual wrongs are real wrongs

authors: Munn, Nicholas

abstract: Many computer games ask us to act in ways which would be morally unconscionable, were we to so act in the physical world. Within the game world, these actions are seen as unproblematic. As such, simple translations of concepts such as assault and murder from the physical to the virtual fail. Killing an opponent in World of Warcraft is not morally equivalent to killing someone in the physical world. However, this does not mean that virtual murder is impossible. Rather, the social reality of particular game-worlds is distinct from, but connected to, the social reality in which we operate in the physical world. In this paper, I examine the ways in which immoral conduct can occur in virtual environments. I discuss the particular problems of the ‘magic circle’ model of gaming in the context of online, massively interactive computer gaming as popularised by World of Warcraft, Rift, Aion. (Castronova 2005, Zimmerman 2012) The most important of these problems is perhaps the lack of distinction many participants in these worlds make between their avatars and themselves. (Lehdonvirta, 2010) This connection between the virtual and physical worlds enables us to generate a moral framework for guiding action within virtual worlds. With this background established, I argue that it is the subversion of game mechanics and intentions which generates the wrongness of particular types of action within virtual worlds.

text: Playing right: Some virtual wrongs are real wrongs Many computer games ask us to act in ways which would be morally unconscionable, were we to so act in the physical world. Within the game world, these actions are seen as unproblematic. As such, simple translations of concepts such as assault and murder from the physical to the virtual fail. Killing an opponent in World of Warcraft is not morally equivalent to killing someone in the physical world. However, this does not mean that virtual murder is impossible. Rather, the social reality of particular game-worlds is distinct from, but connected to, the social reality in which we operate in the physical world. In this paper, I examine the ways in which immoral conduct can occur in virtual environments. I discuss the particular problems of the ‘magic circle’ model of gaming in the context of online, massively interactive computer gaming as popularised by World of Warcraft, Rift, Aion. (Castronova 2005, Zimmerman 2012) The most important of these problems is perhaps the lack of distinction many participants in these worlds make between their avatars and themselves. (Lehdonvirta, 2010) This connection between the virtual and physical worlds enables us to generate a moral framework for guiding action within virtual worlds. With this background established, I argue that it is the subversion of game mechanics and intentions which generates the wrongness of particular types of action within virtual worlds.

year: 2019

title: The day ahead

authors: Webber, Warren

abstract: With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

text: The day ahead With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

year: 2013