The Effects of Environmental Factors and Husbandry Techniques on Roe Enhancement of the New Zealand Sea Urchin, Evechinus chloroticus

<p>The roe of sea urchins (Echinodermata: echinoidea) is a prized seafood in a number of countries around the world, including New Zealand. Increasing fishing pressure on world sea urchin stocks has failed to meet demand. This has led to increasing worldwide interest in roe enhancement of sea urchins. In New Zealand kina (Evechinus chloroticus) have also been heavily fished. However, there are large numbers of poor quality (low gonad index or GI) kina found in kina barrens which are uneconomic to harvest due to low returns. The primary aim of this research was to identify the key holding and environmental conditions for roe enhancement of E. chloroticus to assist in the development of a roe enhancement industry for E. chloroticus to utilise this resource. A series of experiments testing the optimal holding conditions for E. chloroticus in both land- and sea-based holding systems showed that culture depth (3 and 6 m) and removal of the urchins from the water three times per week had no significant effect on gonad growth or urchin mortality. However, exposing E. chloroticus to increased water movement resulted in significantly greater gonad growth in 12 weeks. Increasing water movement is believed to increase the available dissolved oxygen and facilitate the removal of metabolites from around the urchins. Gonad development was not negatively impacted at the maximum stock density tested (6 kg urchin m-2 of internal surface area) and this density is recommended. There are significantly lower running and maintenance costs when E. chloroticus are enhanced in sea-based compared to land-based systems but a full economic analysis is required to assess which is likely to be the more economical option for future roe enhancement. A period of 9 to 12 weeks appears to be the optimal period for roe enhancement in terms of the maximum increase in GI in the shortest time period. Repeated experiments over a 12 month period showed that food availability was the primary driver of roe enhancement (i.e. increase in gonad size) in E. chloroticus. This is followed by seawater temperature, which drives much of the seasonal variation in the gonad size that is observed in wild urchins. This is likely to be due to increased food consumption at higher temperatures. The reproductive stage of E. chloroticus had very little effect on the increase in gonad size of enhanced urchins other than in autumn when gonad growth was slightly lower than in all other seasons. Optimal gonad growth in this study was obtained at 18oC, which was the highest temperature tested. Higher temperatures also resulted in an increase in the rate of progress of the gametogenic cycle of E. chloroticus whilst lower temperatures tended to slow the rate of progress. The effects of temperature on gonad growth (i.e. increased growth at higher temperatures) were consistent across seasons. Photoperiod had minimal effect on gonad growth and the reproductive stage of the urchins over periods of 12 weeks. Photoperiod may still affect gametogenesis of E. chloroticus over longer periods. Low GI kina appear to be capable of significantly larger increases in GI in 10-week periods than high GI kina, as a result of their higher tolerance to stress. This thesis has contributed to improving the technical and economic feasibility of roe enhancement of kina (E. chloroticus) in New Zealand.</p>

The Effects of Environmental Factors and Husbandry Techniques on Roe Enhancement of the New Zealand Sea Urchin, Evechinus chloroticus

<p>The roe of sea urchins (Echinodermata: echinoidea) is a prized seafood in a number of countries around the world, including New Zealand. Increasing fishing pressure on world sea urchin stocks has failed to meet demand. This has led to increasing worldwide interest in roe enhancement of sea urchins. In New Zealand kina (Evechinus chloroticus) have also been heavily fished. However, there are large numbers of poor quality (low gonad index or GI) kina found in kina barrens which are uneconomic to harvest due to low returns. The primary aim of this research was to identify the key holding and environmental conditions for roe enhancement of E. chloroticus to assist in the development of a roe enhancement industry for E. chloroticus to utilise this resource. A series of experiments testing the optimal holding conditions for E. chloroticus in both land- and sea-based holding systems showed that culture depth (3 and 6 m) and removal of the urchins from the water three times per week had no significant effect on gonad growth or urchin mortality. However, exposing E. chloroticus to increased water movement resulted in significantly greater gonad growth in 12 weeks. Increasing water movement is believed to increase the available dissolved oxygen and facilitate the removal of metabolites from around the urchins. Gonad development was not negatively impacted at the maximum stock density tested (6 kg urchin m-2 of internal surface area) and this density is recommended. There are significantly lower running and maintenance costs when E. chloroticus are enhanced in sea-based compared to land-based systems but a full economic analysis is required to assess which is likely to be the more economical option for future roe enhancement. A period of 9 to 12 weeks appears to be the optimal period for roe enhancement in terms of the maximum increase in GI in the shortest time period. Repeated experiments over a 12 month period showed that food availability was the primary driver of roe enhancement (i.e. increase in gonad size) in E. chloroticus. This is followed by seawater temperature, which drives much of the seasonal variation in the gonad size that is observed in wild urchins. This is likely to be due to increased food consumption at higher temperatures. The reproductive stage of E. chloroticus had very little effect on the increase in gonad size of enhanced urchins other than in autumn when gonad growth was slightly lower than in all other seasons. Optimal gonad growth in this study was obtained at 18oC, which was the highest temperature tested. Higher temperatures also resulted in an increase in the rate of progress of the gametogenic cycle of E. chloroticus whilst lower temperatures tended to slow the rate of progress. The effects of temperature on gonad growth (i.e. increased growth at higher temperatures) were consistent across seasons. Photoperiod had minimal effect on gonad growth and the reproductive stage of the urchins over periods of 12 weeks. Photoperiod may still affect gametogenesis of E. chloroticus over longer periods. Low GI kina appear to be capable of significantly larger increases in GI in 10-week periods than high GI kina, as a result of their higher tolerance to stress. This thesis has contributed to improving the technical and economic feasibility of roe enhancement of kina (E. chloroticus) in New Zealand.</p>

Gonad Size Measured by Ultrasound to Assign Stage of Maturity in Burbot

Gonad size (diameter and circumference) measured by ultrasound was assessed as a metric to assign stage of maturity in Burbot Lota lota from Lake Roosevelt, Washington. Paired gonad tissue and ultrasound measurements were collected monthly from November 2017 to March 2018. Gonad tissue was processed for histological analysis to confirm stage of maturity. Gonad diameter and circumference were measured by ultrasound. Excised gonad diameter (i.e., true gonad diameter) was measured by digital calipers, and excised gonad circumference (i.e., true gonad circumference) was measured by a measuring tape. All late vitellogenic (stage 6) ovaries measured by ultrasound had a diameter greater than 3.90 cm, suggesting a value of 3.90 cm or greater may be used to characterize females capable of spawning in the current reproductive cycle. One mid-spermatogenic (stage 3) and all ripe (stage 4) testes were too large to be measured and assigned diameter of 5.11 cm, the maximum value capable of being measured by our ultrasound transducer. A value of 5.11 cm or greater may be used to characterize males capable of spawning in the current reproductive cycle. Testis circumference measured by ultrasound is not reported because some testes were wider than the ultrasound transducer and could not be measured. Measurements of testis diameter did not differ between measurement methods (ultrasound vs. true), but ultrasound measurements of ovary diameter and circumference were higher than true measurements. We attributed the difference between measurement methods to flattening of ovary while applying the ultrasound transducer. Gonad diameter and circumference measured by ultrasound were highly correlated with gonadosomatic index and ovarian follicle diameter indicating gonad size measured by ultrasound is an appropriate index of gonad development in Burbot.

Reduced lactate dehydrogenase activity in the heart and suppressed sex hormone levels are associated with female-biased mortality during thermal stress in Pacific salmon

ABSTRACTFemale-biased mortality has been repeatedly reported in Pacific salmon during their upriver migration in both field studies and laboratory holding experiments, especially in the presence of multiple environmental stressors, including thermal stress. Here, we used coho salmon (Oncorhynchus kisutch) to test whether females exposed to elevated water temperatures (18°C) (i) suppress circulating sex hormones (testosterone, 11-ketotestosterone and estradiol), owing to elevated cortisol levels, (ii) have higher activities of enzymes supporting anaerobic metabolism (e.g. lactate dehydrogenase, LDH), (iii) have lower activities of enzymes driving oxidative metabolism (e.g. citrate synthase, CS) in skeletal and cardiac muscle, and (iv) have more oxidative stress damage and reduced capacity for antioxidant defense [lower catalase (CAT) activity]. We found no evidence that a higher susceptibility to oxidative stress contributes to female-biased mortality at warm temperatures. We did, however, find that females had significantly lower cardiac LDH and that 18°C significantly reduced plasma levels of testosterone and estradiol, especially in females. We also found that relative gonad size was significantly lower in the 18°C treatment regardless of sex, whereas relative liver size was significantly lower in females held at 18°C. Further, relative spleen size was significantly elevated in the 18°C treatments across both sexes, with larger warm-induced increases in females. Our results suggest that males may better tolerate bouts of cardiac hypoxia at high temperature, and that thermal stress may also disrupt testosterone- and estradiol-mediated protein catabolism, and the immune response (larger spleens), in migratory female salmon.

Asymmetries in reproductive anatomy: insights from promiscuous songbirds

Directional asymmetry in gonad size is commonly observed in vertebrates and is particularly pronounced in birds, where the left testis is frequently larger than the right. The adaptive significance of directional asymmetry in testis size is poorly understood, and whether it extends beyond the testes (i.e. side-correspondent asymmetry along the reproductive tract) has rarely been considered. Using the Maluridae, a songbird family exhibiting variation in levels of sperm competition and directional testis asymmetry, yet similar in ecology and life history, we investigated the relative roles of side-correspondence and sperm competition on male reproductive tract asymmetry at both inter- and intraspecific levels. We found some evidence for side-correspondent asymmetry. Additionally, sperm competition influenced directional asymmetry at each end of the reproductive tract: species experiencing higher levels of sperm competition had a relatively larger right testis and relatively more sperm in the right seminal glomerus. Within red-backed fairy-wrens (Malurus melanocephalus), auxiliary males had relatively more sperm in the left seminal glomerus, in contrast to a right-bias asymmetry throughout the reproductive tract in breeding males. Given that the number of sperm is important for competitive fertilization success, our results suggest that sperm competition shapes reproductive asymmetries beyond testis size, with likely functional consequences for male reproductive success.

ASPEK BIOLOGI REPRODUKSI IKAN LAYANG (Decapterus russelli) DAN IKAN BANYAR (Rastrelliger kanagurta) YANG DIDARATKAN DI REMBANG, JAWA TENGAH

Ikan layang (Decapterus russelli) dan banyar (Rastrelliger kanagurta) merupakan dua jenis ikan hasil tangkapan dominan kapal mini purse seine yang didaratkan di Rembang. Aspek biologi ikan layang dan banyar yang diteliti, meliputi sebaran ukuran panjang, perbandingan jenis kelamin, tingkat kematangan gonad dan ukuran pertama kali matang gonad pada tahun 2007. Ukuran yang dominan tertangkap untuk ikan layang 18-18,9 cm, sedangkan untuk ikan banyar 21-21,9 cm. Ikan layang dan banyar yang berkelamin jantan lebih banyak tertangkap pada ukuran lebih kecil daripada ikan yang berkelamin betina. Spesies ikan layang menunjukan bahwa ikan yang dalam kondisi matang (mature) lebih banyak ditemukan pada ikan yang berjenis kelamin betina, sedangkan spesies ikan banyar yang mempunyai tingkat kematangan gonad I, II, III, dan IV lebih banyak ditemukan pada spesies ikanyang berjenis kelamin jantan. Spesies ikan banyar yang mempunyai tingkat kematangan gonad V lebih banyak ditemukan pada spesies yang berjenis kelamin betina. Ukuran pertama kali matang gonad untuk ikan layang betina 18,97 cm dan untuk yang jantan 21,2 cm. Jenis ikan banyar berkelaminbetina ukuran pertama kali matang gonad 20,37 cm, sedangkan yang jantan 20,87 cm. Scad fish (Decapterus russelli) and mackerel (Rastrelliger kanagurta) are two species of dominant caught by boat mini purse seine landed in Rembang. Biological aspects of and mackerel examined are the size of the length, the difference in sex, level of maturity, and gonad size of first time The dominant size caught for scad was 18-18.9 cm, while for mackerel was 21-21.9 cm. Male fishes of scad and mackerel were mostly caught in the smaller size compared to the size of female. Matured of gonad was mostly found in the female of scad fish. While in the female mackerel species having gonad maturity level of 1, 2, 3, and 4 was mostly found in male sex. Mackerel species having 5th stage of gonad maturity was mostly found in the female sex. First time of gonad matured in female scad was in size of 18.97 cm and for a male was 21.2 cm. While in female mackerel, the first time of gonad matured was 20.37 cm and for a male one was 21.2 cm.

Long-term effect of yolk carotenoid levels on testis size in a precocial bird

Conditions experienced during prenatal development can have long-lasting organizational effects on offspring. Maternal carotenoids deposited in the eggs of birds and other oviparous species play an important role during fast embryonic growth and chick development through their antioxidant properties. However, the long-term consequences of variation in maternal carotenoid transfer for the offspring have seldom been considered. Since plasma carotenoid levels at adulthood are known to influence testis size and yolk carotenoid levels influence the ability to extract carotenoids later in life, we hypothesized that maternally transmitted carotenoids might influence gonad size at adulthood. Here, we showed that male Japanese quail ( Coturnix japonica ) originating from a carotenoid-enriched egg had smaller testes than control individuals at adulthood. This result shows that yolk carotenoids have long-term organizational effects. In addition, given that carotenoid intake at sexual maturity increases sperm quality and that a decreased testis size is associated with a lower sperm production, we propose that carotenoid exposure during embryo development might influence a trade-off between ejaculate size and sperm quality.

Infection ecology of Philometra ovata (Nematoda: Philometridae) in a wild European minnow (Phoxinus phoxinus) population in Finland

SUMMARYSeasonal life cycle of body cavity dwelling (BCD) Philometra ovata (Nematoda: Philometridae) has been reported in southern and central European countries, but its swim bladder dwelling (SBD) stage and northern populations have remained unstudied. In this study, we investigated the seasonal life cycle and infection ecology of P. ovata in both swim bladder and body cavity in the European minnow (Phoxinus phoxinus) in Finland. The larval P. ovata infected the swim bladder of minnows mainly in August. Female SBD P. ovata emigrated to body cavity mostly in September, grew to their full size by the end of the next June, and evacuated from minnows in July. In addition, female SBD P. ovata retarding their development and staying in swim bladder were found commonly in minnows, thus the mean monthly prevalence (6·7 ± 3·9%) and mean intensity (1·4 ± 0·8) of BCD P. ovata was lower than that of SBD P. ovata (37·8 ± 15·1% and 2·0 ± 1·5, respectively). Finally, despite the large size of BCD individuals, infection of P. ovata did not impair body condition and relative gonad size of minnows, but increased the mortality and caused physical damages in their hosts during the evacuation period.