Some biological characteristics of the Far Eastern sea cucumber (Apostichopus japonicus) from the Severnaya Bay of the Slavyanka Gulf (Japan Sea)

Some of biological traits of the Far Eastern sea cucumber from the Severnaya Bay were examined in 2016 and 2017. Body length of sea cucumber individuals varied from 3.6 to 23.4 cm. Dermo-muscular bag weight was higher in 2017 (137.5 g). Individual ages were 1–4 years in 2016 and 1–5 years in 2017. Sex ratio was near 1:1 in 2016 and 2017. During the period of the research gonad index was maximal in June – 10.6%. Spawning began in the 2nd decade of June and finished in the 2nd decade of July.

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>

Multiyear trend in reproduction underpins interannual variation in gametogenic development of an Antarctic urchin

Ecosystems and their biota operate on cyclic rhythms, often entrained by predictable, small-scale changes in their natural environment. Recording and understanding these rhythms can detangle the effect of human induced shifts in the climate state from natural fluctuations. In this study, we assess long-term patterns of reproductive investment in the Antarctic sea urchin, Sterechinus neumayeri, in relation to changes in the environment to identify drivers of reproductive processes. Polar marine biota are sensitive to small changes in their environment and so serve as a barometer whose responses likely mirror effects that will be seen on a wider global scale in future climate change scenarios. Our results indicate that seasonal reproductive periodicity in the urchin is underpinned by a multiyear trend in reproductive investment beyond and in addition to, the previously reported 18–24 month gametogenic cycle. Our model provides evidence that annual reproductive investment could be regulated by an endogenous rhythm since environmental factors only accounted for a small proportion of the residual variation in gonad index. This research highlights a need for multiyear datasets and the combination of biological time series data with large-scale climate metrics that encapsulate multi-factorial climate state shifts, rather than using single explanatory variables to inform changes in biological processes.

Notes on the Reproductive Traits of Holothuria fuscogilva Cherbonnier, 1980 from Laguindingan, Misamis Oriental, Philippines

Reproductive traits of white teatfish Holothuria fuscogilva from Laguindingan, Misamis Oriental were investigated from February to July 2020. Gonad samples from 62 adult individuals weighing 1,240g to 5,800g were collected and examined macroscopically and microscopically to determine gonad morphology, sex ratio, gonad maturity, and gonad index. Gonads were composed of numerous branched tubules of varying lengths and frequency of bifurcations arising from the gonad basis. There was no significant variation in the ratio of male to female white teatfish (x2=2.32, α=0.05) and were mostly mature in May (weighing 1,750g–4,000g in males and 2,600g-3,900g in females) with relatively high gonad output. Information on gonad maturation is useful in the development of a successful breeding technology for this economically important sea cucumber species.

Variation in purple sea urchin (Strongylocentrotus purpuratus) morphological traits in relation to resource availability

Flexible resource investment is a risk sensitive reproductive strategy where individuals trade resources spent on reproduction for basic metabolic maintenance and survival. This study examined morphological variation in herbivorous sea urchin grazers across a mosaic landscape of macroalgae dominated habitats interspersed with patches of sea urchin barrens to determine whether sea urchins shift energy allocation in response to food limitation. Extensive underwater surveys of habitat attributes (e.g., sea urchin density, algae cover) were paired with detailed laboratory assays (e.g., sea urchin dissections) to determine how resource abundance affects energy allocation between reproductive capacity and body structure in the purple sea urchin, Strongylocentrotus purpuratus. We found that: (1) sea urchins had a more elongate jaw structure relative to body size in habitats void of macroalgae (i.e., barrens), (2) sea urchin reproductive capacity (i.e., gonad index) was lower in barrens and the barrens habitat was primarily comprised of encrusting algae, and (3) sea urchin jaw morphology (i.e., lantern index) and reproductive capacity (i.e., gonad index) were inversely related. These results suggest that sea urchins respond to macroalgae limited environments by shifting energy allocation between reproductive capacity and modifications of the foraging apparatus, which may explain the ability of sea urchins to acquire food in resource-limited environments.

Reproductive biology of the rayed pearl oyster (Pinctada imbricata radiata, Leach 1814) in Izmir Bay

The present study was carried out to determine gonadal stages and quality of pearl oyster meat (Pinctada imbricata radiata, Leach, 1814) in Izmir Bay (Turkey). Pearl oyster samples were collected from the study area at a depth of ~5 m between February 2013 and January 2014. The highest and lowest temperature was measured in July and January as 27°C and 14.2°C, respectively. The maximum chlorophyll a value of 4.640 μg l−1 was calculated in May and the lowest value of 1.009 μg l−1 was recorded in April. Individuals reached their first maturity in April. Spawning activity was observed from June to September and the gonad index (GI) was at the highest level during those months. The development was observed from April to February. The overall female to male ratio was 1.32:1 (p < 0.05) and it did not affect the GI (p > 0.05). There is a strong positive correlation between the GI and temperature (p < 0.05). The highest condition index (CI) was recorded in May as 12.31 ± 0.51, whereas the lowest one in January as 7.37 ± 0.22. As a result, this study revealed that the pearl oyster population in the region is characterized by high reproductive activity, especially during the summer months.

Effects of Ethinylestradiol (EE2) and an Organophosphorus Flame Retardant (TCPP) on Gonadal Maturation in the Sea Urchin, Paracentrotus lividus

The sea urchin (Paracentrotus lividus) was used to test the effects of one of the most abundant flame retardant additives for plastics, tris (1-chloro-2-propyl) phosphate (TCPP), and the synthetic hormone ethinylestradiol (EE2) on gametogenesis and gonad development of adults. With this aim, 403 individuals of both sexes were exposed to TCPP concentrations ranging from 0.2 to 10 µg/L, EE2 (0.01 µg/L), seawater and solvent controls for 7 and 28 days. EE2 and TCPP exposure did not cause histological damage in the gonads. Some evidence of estrogenic effects of TCPP within the µg/L range and EE2 within the ng/L range is reported. Females exposed to 1 µg/L TCPP for 7 days showed a significant increase in gonad development assessed as gametogenic stage, females exposed to 10 µg/L TCPP showed increased gonad development both in terms of weight (Gonad Index, GI, at both 7 and 28 days) and maturation (Pixelar Index, PI), and females exposed to 10 ng/L EE2 showed increased PI after 28 days exposure. Male sea urchins exposed to both TCPP and EE2 for 7 days showed increased frequencies of low development gonad stage. However, the patterns of response are affected by the high inter-individual variability, the differing initial stage of the gonad, as well as the dosage administered.