Gonad Yield Research Articles

Gametes and embryos of sea urchins (Paracentrotus lividus, Lmk., 1816) reared in confined conditions: their use in toxicity bioassays

Sea urchins of the species Paracentrotus lividus, collected along the Southern Adriatic coast at the end of their reproductive season, were reared in a recirculating aquarium under controlled temperature and feeding conditions in order to induce off-season maturation of gametes to be used in toxicity bioassays. After 14 weeks of rearing, the gonad index was calculated, histological analyses of the gonads were performed, their fertilisation ability was measured and the EC50 for copper in embryotoxicity bioassays was evaluated. The sperm motility pattern (based on the percentages of total motile and rapid sperm, together with sperm velocity parameters) was assessed using a computerised analyser. All specimens showed a significant increase in gonad yield with respect to field-collected animals and were in pre-spawning or spawning stages. The motility parameters, fertilisation ability and EC50 level of the collected gametes were comparable to those of field-matured specimens. In conclusion, the sea urchins reared under experimental conditions were characterised by faster gonad maturation than the field population, producing viable gametes and larvae whose biological response in toxicity bioassays was similar to that of field-reared specimens of P. lividus.

Estimates of heritabilities and genetic correlations for growth and gonad traits in the sea urchin Strongylocentrotus intermedius

The present study is the first estimate for the sea urchin, Strongylocentrotus intermedius, of genetic parameters for growth and gonad traits during the entire reproductive period. 2165–5764 sea urchins were sampled from 74 to 120 families at six different growth stages. Six hundred individuals were sampled from 20 randomly chosen families at harvest. Coefficients of variation for most growth and gonad traits were high (18.08–78.66%) suggesting a good variation foundation for breeding. Point estimate for heritabilities based on the sire components of variance were moderate to high for test height (0.24–0.39), test diameter (0.21–0.48) and body weight (0.16–0.49). Heritabilities of gonad wet weight, gonad index and gonad moisture at harvest were 0.17, 0.41 and 0.50 respectively (moderate or high). Gonad colour parameters, L* (lightness) and a* (redness) have a heritability of 0, while b* (yellowness) and colour difference ΔE1 and ΔE2 have very similar heritabilities of 0.2, 0.18 and 0.21 respectively. Heritabilities of β-carotene concentration and content were 0.89 and 0.44 respectively. The genetic correlations between the two measured traits ranged from −0.984 to 0.999. Gonad wet weight, L*, b*, β-carotene concentration and β-carotene content had significant positive genetic correlations with all the growth traits. However, gonad index, gonad moisture and colour differences ΔE1 and ΔE2 had significant negative genetic correlations with growth traits. The present study indicates that growth, gonad yield and most gonad quality traits could be improved by selection with moderate to high potential. Indirect selection should be applied on gonad traits using growth traits as secondary traits. The present study provides important theoretical guidance for future selective breeding programmes for S. intermedius.

Effects of diet and temperature on ingestion, absorption, assimilation, gonad yield, and gonad quality of the purple sea urchin ( Strongylocentrotus purpuratus)

Sea-urchin ingestion rate, absorption, gonad yield, and gonad quality can be influenced by a variety of factors, including food quantity, food quality, and various environmental conditions. We examined the combined effects of two factors (diet and temperature) on ingestion rate, absorption, assimilation efficiency, and gonad enhancement of the purple sea urchin, Strongylocentrotus purpuratus, over a 12-week period. Four diets [three kelp species ( Macrocystis integrifolia, Nereocystis luetkeana, and Saccharina latissima) and one prepared feed] and three temperatures (8.0 ± 0.4, 12.3 ± 0.3, and 16.2 ± 0.4 °C: mean ± SD) were tested in a completely crossed factorial design. Ingestion rate, gravimetric absorption, and assimilation efficiency of urchins fed the various diets were calculated at weeks 6 and 12. In addition, a number of gonad attributes were quantified at the beginning and end of the experiment including wet weight, percent water content, gonad index, texture, firmness, colour, and flavour. Ingestion rate, gravimetric absorption, and assimilation efficiency were generally significantly affected by both temperature and diet. Wet-weight ingestion rates were significantly higher with the three kelp treatments than with the prepared diet at both weeks 6 and 12. This particular dietary difference was not apparent, however, when ingestion rates were expressed on a dry-weight basis. The highest ingestion rates were recorded for animals held at 12 °C at week 6 and at 16 °C at week 12. Absorption rates and assimilation efficiencies were significantly higher at 16 °C than at 8 °C at week 6 and significantly higher at 16 °C than at the other two temperatures at week 12. Final gonad weight and gonad index were significantly greater in urchins fed the prepared diet than in those fed any of the three kelp species, with little difference among the kelp treatments. Final gonad weight was significantly affected by temperature, but this effect was dependent on diet; temperature had little impact on gonad weight (and index) in the three kelp treatments, but 12 and 16 °C produced significantly heavier gonads than 8 °C for urchins fed the prepared diet. Gonads of urchins fed kelps had more (significantly more in the case of M. integrifolia and N. luetkeana) water than those fed the prepared diet. Gonad colour, texture, and firmness were generally not significantly affected by temperature, diet, or the interaction of these two factors. Gonad flavour was generally (sometimes significantly) better in urchins fed the prepared diet than in those fed the three kelp species. Taking all the measured variables into consideration, we recommend that culture operations utilise a prepared diet at 12 °C to optimise gonad production of S. purpuratus.

A comparison of the effect of urchin size and diet on gonad yield and quality in the sea urchin Evechinus chloroticus Valenciennes

We compared the gonad-enhancing effects of two diets (NIWA and NIFA diets) in two size classes of sea urchins (Evechinus chloroticus): small and large urchins with a test diameter of 75.6 ± 1.2 mm and 93.8 ± 0.5 mm, weighing 174.8 ± 7.9 g and 315 ± 5.6 g, respectively. After eight weeks being fed prepared diets, urchin gonad index (GI) had significantly surpassed that of the initial and final samples of wild urchins. Urchins in the NIWA/small treatment had a larger GI than the NIFA/small and NIFA/large treatments. The NIWA/large treatment had a larger GI than the NIFA/large treatment. The overall percentage increase in GI for the NIWA/small, NIWA/large, NIFA/small and NIFA/large treatments were 183%, 135%, 132% and 85%, respectively. In terms of gonad colour (CIELAB), there were no significant differences in gonad redness (a*) or yellowness (b*) between experimental treatments, but there was a significant difference in gonad lightness (L*) with small urchins fed both diets having lighter-coloured gonads than the large urchins fed both diets. Sensory assessment of gonads revealed that gonads from small urchins fed both diets were rated as being of better colouration and more uniform in colour than gonads from large urchins. Gonads of urchins fed the NIFA diet were rated as being less bitter and of better overall taste than gonads from urchins fed the NIWA diet. This study shows that feeding prepared diets to E. chloroticus can significantly increase gonad yield but that different diets can affect the magnitude of GI increase and the taste of gonads, and that smaller urchins appear more suitable for gonad enhancement.

Effect of Protein Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins Strongylocentrotus droebachiensis

Abstract— An important aspect in the development of any aquaculture industry is the maximization of juvenile somatic growth (i.e., body growth) to reduce production time and increase the size of the final product. In this study, green sea urchins Strongylocentrotus clroebachiensis were fed a prepared diet from 4 December 1998 to 10 September 1999 (i.e., 280 d) in a laboratory to investigate the effect of protein source (soybean andlor fish), protein concentration (20,30,40, and 50% dry mass) and juvenile size (4-8 mm and 12-20 mm initial test diameter) on somatic growth. A natural diet of Laminwia longicrurus (i.e., kelp) was used as a reference. There was no difference in initial size among the treatments for either the smaller cohort 1 or the larger cohort 2 sea urchins (6.3 mm and 13.8 mm initial average test diameter, respectively) (P > 0.05 for all tests). After 280 d, the sea urchins fed kelp had an average size of 20.7 mm and 24.5 mm (cohort 1 and cohort 2, respectively). The final average sizes of the sea urchins fed the prepared diets, which did not relate to dietary protein concentrations andlor protein source, ranged from 13.2 mm to 16.2 mm (cohort 1) and from 20.4 mm to 22.9 mm (cohort 2), and were significantly smaller than the kelpfed sea urchins (P < 0.05 and P < 0.001, cohort 1 and cohort 2, respectively). All treatments experienced 95% survivorship or greater. Sea urchin size appears to affect growth rate when optimal conditions for growth are available (i.e., diet and water temperature). As water temperatures increased during the summer of 1999, the sea urchins in cohort 1 fed kelp had a significantly higher growth rate (0.069 dd) than the cohort 2 kelpfed sea urchins (0.052 dd) (P < 0.05). However, within each cohort, there were no significant difference in growth rate (P > 0.05) among the sea urchins fed prepared diets, suggesting sea urchins do not require high concentrations of dietary protein for superior growth, and that plant protein can substitute fish protein in sea urchin diets. Furthermore, the sea urchins fed the prepared diets had poorer test quality and larger gonad yields (13-22%) compared to the kelpfed sea urchins (4.2%) and a wild sample of sea urchins of similar size (4.0%). The results suggest that the sea urchins fed the prepared diets allocated more energy to gonad production, whereas those fed a natural diet allocated more energy toward test production. To address this gap, more research is required to identify the nutritional components required for test growth that were present in kelp, but appeared to be deficient in the prepared diets.

The reproductive response of the sea urchins Paracentrotus lividus (G.) and Psammechinus miliaris (L.) to a hyperproteinated macrophytic diet

The sea urchins Paracentrotus lividus and Psammechinus miliaris are submitted to the same environmental conditions in the Bay of Brest. The relationship between seasonal changes in food source quality and their gonad production was investigated in reproducing experimentally these conditions. In a first stage two macroalgae ( Palmaria palmata and Laminaria digitata) were tested. P. miliaris showed a stronger preference for P. palmata and over a year-long experiment both urchins progressively preferred P. palmata. Seasonal variations in the chemical composition of P. palmaria were observed in the Bay of Brest: total carbohydrates were important and the relative maximum (about 50%) was reached between February and August; the lipid level was low and had a relative maximum of about 1% in June and August. Total protein in P. palmaria was high compared to other seaweeds: the maximum value (25%) was observed in June, which was probably due to the maintenance of nitrogen nutrient in the bay. In the second stage of the study, seasonal changes in biochemical components of ingestion and absorption of the two sea urchins were followed in the laboratory using a monospecific diet of P. palmaria. The patterns of total carbohydrates and lipid absorption were very similar for both sea urchin species. Carbohydrates were absorbed strongly and uniformly, year round. Lipid absorption mimicked the lipid nutrient pattern in the food source. Only changes in protein absorption varied slightly between the two urchin species. Protein absorption was maximal for both species in February and June, but the quantity of absorbed protein was significantly higher in P. miliaris than in P. lividus during February. This increase was concomitant with protein storage in the sea urchin gonads, which peaked in February for P. miliaris and in June for P. lividus. P. lividus had a higher gonad production efficiency, based on gonad yield. The comparison between in situ data and the experimental results suggests that an algal diet more nitrogenous than the in situ algal food source would benefit the herbivorous P. lividus, rather than the more omnivorous species P. miliaris. Although P. milaris has been described as a species with large gonad production potential, P. lividus appears to be a more suitable species for echiniculture conditions.

Effect of different feed formulations on feed efficiency, gonad yield and gonad quality in the purple sea urchin Heliocidaris erythrogramma

The nutritive values of three pelleted prepared diets, based on animal (AP), vegetable (VP) and yeast protein (YP) were studied for the sea urchin Heliocidaris erythrogramma (Val.). Fresh macroalga Ulva australis was used as a natural control diet. Triplicate groups of five animals were fed one of the four diets ad libitum every second day for 85 days. Sea urchins fed pelleted feeds had significantly higher food consumption rates (dry basis) and significantly lower total and protein absorption efficiencies compared with the algal diet. The gonad yield and gonad production efficiency in sea urchins fed the natural diet were significantly higher compared with initial group (gonad yield only) and urchins fed animal and vegetable diets, but did not differ significantly from those of the animals fed the yeast diet. Percent protein and lipid in the gonads were not affected by the dietary source. The taste and smell of gonads were generally better in sea urchins collected from the wild or fed yeast and natural diets than in sea urchins fed animal and vegetable diets. The animal protein diet was the most stable in seawater while the yeast protein diet had the poorest water stability. The results of this study suggest that development of a more stable, single-cell, protein-based diet has a potential to promote gonad production of H. erythrogramma.

Effect of urchin size and diet on gonad yield and quality in the green sea urchin ( Strongylocentrotus droebachiensis)

A 6-week experiment (August 10 to September 21, 1999) was conducted to determine the effect of urchin size and diet on gonad enhancement of the green sea urchin Strongylocentrotus droebachiensis. Sea urchins were collected from the wild and divided into four size classes—30.0–39.9, 40.0–49.9, 50.0–59.9, and 60.0–73.0 mm test diameter—each size group being split into two dietary treatments [prepared feed or kelp ( Laminaria longicruris and/or Laminaria digitata)]. The experiment was a 4×2 completely crossed design. A number of gonad attributes were quantified at the beginning and end of the experiment including: wet weight, percent yield, percent water, colour, texture, firmness, and taste. The percent change of these variables over the 6-week period was calculated. Colour was assessed subjectively by eye using colour ratings and objectively with a reflected-light, fibre-optic spectrophotometer to generate CIE L* (lightness), a* (hue), and b* (chroma) values. Gonad taste was subjectively evaluated at the end of the experiment. Results from experimental sea urchins were compared and contrasted with those of wild specimens collected from the source population at the end of the experiment. Percent gonad yield at the end of the experiment and percent increase in percent gonad yield over the 6-week period was significantly greater in urchins fed the prepared diet than in those fed kelp. Percent gonad yield was highest in the 40.0–49.9 mm group, followed closely by the 50.0–59.9 and 30.0–39.9 mm size groups, whereas percent increase in percent gonad yield decreased with increasing urchin size. Gonad colour at the end of the experiment was significantly better in urchins fed the prepared diet than in those fed kelp (as judged by colour ratings, a*, and b*) and was better in smaller than larger individuals (as judged by colour ratings, L*, and a*). Percent change in gonad colour ratings decreased and percent change in L* and a* increased with increasing urchin size. Urchin size and feed type had no significant effect on gonad texture, but both factors significantly influenced gonad firmness and taste. Gonads of urchins fed the prepared diet were significantly softer and had significantly more water than those fed kelp. Gonad firmness and percent change in firmness increased with increasing urchin size. Kelp-fed individuals produced significantly better tasting gonads than those fed the prepared diet. The largest urchins produced the best tasting gonads of those fed kelp, but the smallest individuals had the best gonad taste of those fed the prepared diet. Overall, considering both gonad quantity and quality factors, sea urchins of 40.0–49.9 mm test size were deemed to be the most promising for gonad enhancement operations.

Optimizing Prepared Feed Ration for Gonad Production of the Green Sea Urchin Strongylocentrotus droebachiensis

AbstractAdult green sea urchins Strongylocentrotus droebachiensis were fed three different quantities (0.25, 0.50, 1.00% body weight/d) of a prepared feed during a 12‐wk experiment to determine the effect of food ration on gonad quantity and quality. A diet of kelp, Laminaria longicruris and/or L. digitata, fed at satiation (3% body weight/d) and urchins taken from the wild at the beginning and end of the experiment served as controls. Urchins fed prepared feed or kelp increased their percent gonad yield significantly over the experimental period. Affer 12 wk, individuals fed the prepared diet at 0.50 or 1.00% body weighffd had significantly higher percent gonad yields (mean ± SEM: 23.5 ± 0.6% and 23.4 ± 0.7%, respectively) than urchins fed at 0.25% body weight/d (18.0 ± 1.0%) or control animals given kelp (18.3 ± 0.8%). There was no significant difference in gonad yield between the 0.50 and 1.00% feeding levels. All feeding treatments had significantly higher percent gonad yields than urchins sampled from the wild at the end of the experiment that had recently spawned (2.8 ± 0.5%). There was no significant difference in gonad taste among urchins fed the prepared diet at 0.25% body weight/d, those given kelp, or those collected from the wild at the end of the experiment (good to very good ratings), but all of these treatments had significantly better tasting gonads than urchins given the prepared feed at 0.50 or 1.00% body weight/d (satisfactory ratings). Gonad taste rating of urchins fed a prepared diet was dependent on ration with greater feed amounts leading to worse tasting gonads (linear regression: r2= 0.68, P &lt; 0.01). Gonad color, texture, and firmness did not differ significantly among any of the feed ration treatments or kelp control. Results suggest that the best ration for prepared feed would be 0.50% body weightld since this would optimize gonad yield while minimizing feed costs. Further research on prepared feeds is required to optimize both gonad color and taste.

Effect of protein source ratio and protein concentration in prepared diets on gonad yield and quality of the green sea urchin, Strongylocentrotus droebachiensis

Adult green sea urchins ( Strongylocentrotus droebachiensis) were collected from the wild and held in laboratory tanks where they were fed a number of prepared diets or a control of kelp ( Laminaria longicruris and/or L. digitata) for a period of 12 weeks. Twelve different prepared diets were formulated in order to examine two experimental factors: (1) protein concentration at three different levels [19%, 24%, and 29% (percent dry weight of all dietary components)] and (2) protein source ratio at four different levels [rockweed meal, wheat meal, corn meal, soybean meal, fish meal in the following four ratios: 0:30:30:25:15, 15:20:20:35:10, 30:10:10:45:5, 45:0:0:55:0, respectively (percent dry weight of all meals)]. Each concentration was present at each source ratio in a completely crossed experimental design. Gonad colour, percent gonad water, and percent gonad yield of experimental urchins were determined approximately every week while gonad texture, firmness, and taste were subjectively evaluated at the end of the experiment. Results were contrasted with those of wild specimens collected from the source population at weeks 0 and 12 of the experiment. After 12 weeks, all prepared diets produced significantly higher percent gonad yields than kelp-fed urchins or wild controls, the best-prepared diet giving a mean weekly increase of 1.3% in percent yield. Percent gonad yield was not significantly affected by protein concentration, but was significantly affected by protein source ratio; the 15:20:20:35:10 diet gave significantly higher yields than the 0:30:30:25:15 or 45:0:0:55:0 diets (30:10:10:45:5 being intermediate). Gonad colour of urchins fed prepared diets was, generally, pale yellow/orange to yellow-brown/orange-brown at the end of the experiment and not significantly different from kelp-fed urchins or wild controls. Gonad colour was not significantly affected by protein source ratio, but was significantly affected by protein concentration; the 19% and 24% levels produced significantly better coloured gonads than the 29% level. At the end of the experiment, gonad texture of urchins fed prepared diets ranged from smooth to very smooth with distinct gonad segment halves while gonad firmness ranged from firm to very firm. Gonad texture and firmness of prepared diet treatments did not differ significantly from kelp-fed urchins or wild controls and neither protein concentration nor protein source ratio significantly affected gonad texture or firmness. At the end of the experiment, gonad taste of urchins fed prepared diets ranged from bitter to sweet with all prepared diets producing significantly worse tasting gonads than the kelp-fed urchins. Gonad taste was not significantly affected by protein source ratio nor protein concentration, but there was a general trend of worsening taste with increasing protein levels. Based on these results, a 19% protein concentration and a 15:20:20:35:10 (rockweed meal/wheat meal/corn meal/soybean meal/fish meal) protein source ratio are recommended for further dietary research.

Effect of binder type and concentration on prepared feed stability and gonad yield and quality of the green sea urchin, Strongylocentrotus droebachiensis

Adult green sea urchins, collected from the wild, were held in laboratory tanks and fed one of eight prepared feeds—varying solely in the type and concentration of binder used in the diet (i.e. gelatin, guar gum, sodium alginate, or corn starch each being present at 3% or 5% dry weight)—for a period of 12 weeks. Two control treatments, kelp and a commercially available salmon feed, were also included. Gonad colour, percent gonad water, and percent gonad yield of urchins in the 10 feeding treatments were determined approximately every week while gonad texture, firmness, and taste were subjectively evaluated at the end of the experiment. Results were contrasted with those of wild specimens collected from the source population at weeks 0, 4, and 12 of the experiment. Pellet coherence and amount of feed lost were examined in separate feed stability trials. After 12 weeks, all prepared feeds produced significantly higher percent gonad yields than kelp or wild controls. Binder type significantly affected percent gonad yield at week 9, the highest yield being attributed to feeds made with gelatin. By week 12, however, there were no significant differences in percent gonad yield among the different binders and this was attributed to yields reaching a physiological maximum. Binder concentration significantly affected percent gonad yield at the end of the experiment with the higher concentration producing greater yields. While gonad colour was significantly affected by binder type (starch producing better colour than any other binder), all prepared feeds generally produced gonads that were cream or tan in colour. This contrasted with kelp-fed or wild controls that typically had pale yellow or orange gonads. Binder concentration did not significantly affect gonad colour. While the texture of gonads from urchins fed prepared feeds was statistically similar to that of gonads taken from kelp-fed or wild individuals, firmness and taste were significantly poorer. Binder type and concentration did not significantly affect gonad texture, firmness, or taste. Feed stability was significantly affected by binder type (gelatin producing more stable pellets than any other binder), but not concentration. Amount of feed lost from pellets was not significantly affected by binder type or concentration, but this was most probably due to the fact that flow rates in the tanks were not sufficient to wash broken feed out of experimental units. Based on these results, gelatin is the binder recommended for use in further dietary experiments and commercial-scale feed operations.

Dental Granuloma

The establishment of a commercially sustainable aquaculture production of Paracentrotus lividus depends on the development of diets able to fulfil the species nutritional requirement and the production of market valuable roe. As dietary protein level and protein: energy ratio (P:E) are major limiting factors for sea urchin growth and gonad development, six isolipidic (≈ 7%) practical diets of increasing protein content (20, 25, 30, 35, 40 and 46 % dry matter, DM) and protein: energy ratios (P:E) (15, 18, 21, 24, 27 and 28 mg P/kJ) were fed to triplicate groups of adult sea urchins for 107 days to identify the dietary protein level and P:E able to promote the highest nutrient utilisation, best growth and gonad enhancement. The trial results showed that protein apparent digestibility coefficients ranged between 69 and 86 %, without significant differences among groups. Digestible energy intake and feed conversion ratio (FCR) decreased with increasing dietary protein levels and protein: energy ratios, whilst digestible protein intake remained similar in all groups. The retention and gain of protein and energy remained unaffected by dietary treatments, resulting in a specific growth rate of 0.3 % per day across treatments, and in a final body weight between 22 and 24 g. All diets significantly increased the gonadosomatic index (GSI) attaining 7.4–8.5%. Both GSI and gonad protein gain picked with a dietary P:E of 21 mg P/kJ (diet P30), whereas gonad protein content picked when P:E was 24 mg P/kJ (diet P35). These results, in association with the decreasing FCR with increasing dietary protein levels, suggest that diets with 30 % DM of protein and a P:E of 21 mg P/kJ are the most appropriate to promote both high somatic growth and high gonad yield in adult P. lividus.