Heritability of larval and juvenile growth for two stocks of Manila clam Ruditapes philippinarum

The heritability of larval and juvenile growth in natural and cultured populations of the Manila clam Ruditapes philippinarum was estimated using an unbalanced nested design and an artificial fertilization technique. A total of 33 full‐sib families and 10 half‐sib families were obtained from the natural population in Shihe (Dalian, Liaoning Province in the north‐eastern part of China), whereas 11 half‐sib families and 33 full‐sib families were generated from the cultured population in Putian (Fujian Province in the south‐eastern part of China). The offspring from each family were reared under the same hatchery and nursery conditions. Results from these studies led to estimates indicating a significantly greater influence due to the dam component compared with the sire component for both natural and cultured populations, which was mainly due to maternal effect. We found that the heritability estimates obtained from the intra‐group correlation of sire half‐sib were precise and unbiased. The narrow‐sense heritabilities of shell length for the Manila clam in the natural population (NP) at larval (at the age of 9 days) and juvenile (at the age of 30 days) stages were 0.22 ± 0.11 and 0.39 ± 0.14, respectively, whereas those in the cultured population (CP) were 0.17 ± 0.09 and 0.87 ± 0.24 respectively. The heritabilities of both NP and CP at 3 days were not significantly different from zero, and were ?0.03 for NP and ?0.14 for CP. These results suggest that selection should be highly effective in Manila clam, and that selecting either a natural or a cultured population for producing faster growing larvae and juveniles should be successful. Selective breeding could thus be used to develop high‐quality seed that would facilitate the development of a shorter culture cycle and higher yields.     

Heritability estimates for nutritional quality‐related traits of the Pacific oyster,Crassostrea gigas

Pacific oysters, Crassostrea gigas, are the most abundantly harvested shellfish in the world and are ecologically significant. The content of nutrients, including protein, glycogen, lipid, zinc (Zn), and selenium (Se), is important for oyster meat quality, but heritability estimates of such traits have rarely been reported. In this study, 64 full‐sib families were generated using a nested mating design. Finally, 18 full‐sib families, of which there were nine half‐sib families, with each containing 2 full‐sib families, were sampled for heritability estimates. The narrow‐sense heritabilities of glycogen, protein, lipid, Zn, and Se contents were 0.29 ± 0.02, 0.38 ± 0.02, 0.58 ± 0.08, 0.02 ± 0.02, and 0, respectively. Negative genetic correlations existed between both glycogen and protein content (?0.95 ± 0.004) and between lipid and protein content (?0.59 ± 0.05), whereas a positive correlation was observed between lipid and glycogen content (0.16 ± 0.06). Weak genetic and phenotypical correlations (r = 0–0.2) were observed between shell height and nutritional quality traits. These data demonstrated that glycogen, protein, and lipid content can be chosen in a selective breeding program, but glycogen and lipids cannot be selected together with protein. Furthermore, performing indirect selective breeding for quality traits by selecting traits related to growth is impossible. This study provides information for the development of breeding strategies for oyster quality traits.     

Genetic parameters of growth and survival in the Pacific oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is a representative bivalve mollusc that is widely cultured in the world and is the largest molluscan group cultured in China. In order to assess the feasibility of improving survival of C. gigas through genetic selection, the heritability and genetic correlations for growth and survival traits between different life stages were examined. Genetic parameters were estimated based on intraclass correlations of 49 full‐sib families (29 half‐sib families) in larvae (4 and 20 days after fertilization) and spat (140 days after fertilization) stages. The heritability for growth traits in larvae and spat was 0.30–0.86 and 0.53–0.59, respectively, and varied with ages. The heritability of survival was low in larvae (0.13 ± 0.05 and 0.17 ± 0.04, respectively for 4 and 20 days after fertilization) but medium (0.39 ± 0.07) in spat, suggesting that selection for increasing spat survival was feasible. The genetic correlation between growth traits within age was medium to high and positive (ranging from 0.47 to 0.96, respectively, between shell length (SL) and shell height (SH) at 20 days and between SL and SH at 140 days after fertilization), suggesting that selection to improve single growth trait will cause positive response in another growth traits in C. gigas. The genetic correlations between survival and growth traits at 140 days were low but positive (ranging from 0.23 to 0.27, respectively, between survival and SH and between survival and SL at 140 days after fertilization), suggesting that selection for survival may not have a negative response in growth. Overall, this study suggests that survival traits should be taken as improving target of next selection breeding programme in C. gigas.     

Heritability estimates for growth‐related traits in the Pacific oyster (Crassostrea gigas) using a molecular pedigree

Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed‐family approach has not been actively pursued. In this study, heritability for growth‐related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full‐factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full‐sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth‐related traits could be improved by exploiting additive genetic effects through selective breeding.     

Heritability for growth traits in giant freshwater prawn,Macrobrachium rosenbergii (de Mann 1879) based on best linear unbiased prediction methodology

In this study, heritability was estimated for growth‐related traits of giant freshwater prawn (Macrobrachium rosenbergii) before and after morphological sexual differentiation. Estimation was made on data from 16 full‐sib and eight half‐sib families. The variance estimation was performed using a univariate mixed linear animal model and variance components were analysed following an animal model using restricted maximum likelihood procedure using average information algorithm. Heritability estimates (h²) varied considerably with ages. At 2 months old, h²for carapace length (CL; 0.35±0.15) and body weight (BW; 0.26±0.13) were higher than those estimated at 5 months old, based on mixed sex data. However, when data were sorted by sex, h² calculated from data of females were higher than those of males for CL (0.26±0.16 vs. 0.10±0.06), BW (0.28±0.17 vs. 0.12±0.08), body length (0.40±0.17 vs. 0.11±0.07), total length (0.47±0.18 vs. 0.11±0.07) and claw length (0.29±0.16 vs. 0.03±0.04). The same trend was observed for traits at 6 months old in both bulk and individual rearing.     

Estimation of genetic parameters for growth traits in cultured clam Meretrix meretrix (Bivalvia: Veneridae) using the Bayesian method based on Gibbs sampling

The aim of this study was to estimate the genetic parameters of the growth performance of clam Meretrix meretrix. As part of the breeding programme, 25 full‐sib families nested within eight half‐sib families were produced, planted out and tested to assess the heritability of the total body weight (TW), shell length (SL), shell height (SH) and shell width (SW) at different growth stages. Method of analysis was implemented using the Bayesian method based on the Multiple Trait using Gibbs Sampling under Animal Model program, which was used to estimate the (co)variance components of the traits and conduct genetic analysis. A total of 25 full‐sib families, each with 30–35 individuals within family, were used for the analysis. Significant positive genetic and phenotypic correlations between SL, SW, SH and TW with each other were observed. The growth traits showed high‐magnitude heritabilities, with values ranging from 0.64 to 0.85, which indicates that these traits should respond to selection and therefore should be included in genetic improvement programmes.     

Efficacy of selection in sexually breeding Artemia (Artemia franciscana,Kellogg, 1906)

Bi‐directional selection for smaller naupliar size (SNS) and bigger naupliar size (BNS) was practiced to develop two divergent lines. The efficacy of bi‐directional mass selection in Artemia franciscana was evaluated by comparing the predicted genetic gains with the realized genetic gains. Two sets of predictions were made using two heritability estimates, e.g., the heritability estimate from full‐sib analysis (h²) and the estimate from regression of offspring on mid parent (b_op). Predictions with the full‐sib heritabilities were of very high magnitude as compared with predictions with b_op heritabilities. The predictions based on b_op were more or less in agreement with realized genetic gain, while the predictions with heritability estimates based on full‐sib analysis were much higher than the realized gains. Ratios of realized gain to predicted gain based on full‐sib heritabilities were 0.2302 and 0.2152, respectively, for males and females of the SNS line, and 0.0471 and 0.2248, respectively, for males and females of the BNS line. Ratios of realized gain to predicted gain based on b_op were 1.5348 and 0.6069 for males and females of the SNS line and 0.1028 and 0.9503 for males and females of the BNS line. Ratios of realized gain to predicted gain based on full‐sib heritability were of low magnitude in all the cases as the heritability estimates based on full‐sib analysis were inflated by non‐additive genetic variance. The ratios of realized gain to predicted gain based on b_op were high in both sexes of SNS and females of BNS, indicating high efficacy of selection as b_op includes only additive genetic variance. However, it was of low magnitude in BNS males. Thus, the heritability estimates based on regression of offspring on mid parent (b_op) are more reliable than that of heritability estimates based on full‐sib analysis (h²) for predicting the selection response in Artemia.     

深凹壳型香港牡蛎选育群体生长性状的遗传参数估计

为了培育壳型和生长性状优良的深凹壳型香港牡蛎新品系,以广东台山镇海湾野生香港牡蛎天然采苗的2龄养殖群体为基础群体,以壳型指数D为指标,按照10%留种率和1.755选择强度,利用截头法进行深凹壳型香港牡蛎的群体选育;分析了幼虫期、中间培养期、养成后期的选择反应、遗传获得和现实遗传力等遗传参数。结果发现,选择组的壳高和壳型指数D均大于对照组,遗传参数估算值随着个体的增大而增加。幼虫期,壳高的平均选择反应、平均遗传获得、平均现实遗传力分别为0.363±0.167、1.678%±0.416%、0.207±0.095,中间培养期分别0.639±0.115、7.618%±2.666%、0.364±0.065,养成后期分别为0.668±0.179、8.861%±3.072%、0.381±0.102。养成后期,壳型指数D的平均选择反应、平均遗传获得、平均现实遗传力分别为0.748±0.066、9.090%±0.565%、0.426±0.038。研究结果为培育深凹壳型、生长性能良好的香港牡蛎优良品种提供了实验依据和理论基础。     

Genetic parameters for resistance against Vibrio anguillarum in turbot Scophthalmus maximus

Genetic parameters for resistance to Vibrio anguillarum in Scophthalmus maximus were estimated using three different statistical models. Data were recorded from an experimental infection performed on 2,400 individuals from 30 full‐sib groups. Cross‐sectional linear model and cross‐sectional threshold probit model were used to analyse the test‐period survival; the cross‐sectional threshold logit models were used to analyse the test‐day survival. The heritability values estimated by cross‐sectional linear model (CSL), cross‐sectional threshold (probit) model (THRp) and cross‐sectional threshold (logit) model (THRl) were 0.202 ± 0.101, 0.296 ± 0.168 and 0.110 ± 0.023, respectively. The correlation coefficients between the full‐sib families’ estimated breeding values (EBVs) based on these three models were over 0.993. An almost identical ranking of families was generated using any of these models. Accuracy of selection using CSL, THRp and THRl models was 0.783, 0.789 and 0.801, respectively. Accuracy of selection based on the THRl model was higher than that based on CSL and THRp models.     

Genetic variation in the growth traits of straight-bred and crossbred black bream (Acanthopagrus butcheri Munro) at 90 days of age

The current slow growth rate of black bream (Acanthopagrus butcheri Munro) impedes their widespread commercial aquaculture across inland southern Australia. We report initial estimates of genetic variation for growth traits at 90 days of age from a diallel cross using two black bream populations. Standard length, total length, and wet weight varied significantly among lines and among half‐sib groups within lines. Differences among half‐sib groups explained 6.8% of the total variance in standard length, 8.3% in total length, and 7.1% in wet weight, giving estimated heritabilities over all lines of 0.27±0.11 for standard length, 0.33±0.13 for total length, and 0.28±0.12 for wet weight. There was no evidence for heterosis in any traits when straight‐bred and crossbred lines were compared. There were high phenotypic (r_P=0.95–0.98) and genetic (r_G=0.63–0.69) correlations among all growth traits.     

Heritabilities and genetic correlation of shell thickness and shell length growth in a mussel,Mytilus chilensis (Bivalvia:Mytilidae)

Shell thickness in mollusks is generally considered adaptive because of their effects on fitness. However, little is known about the genetic basis of shell thickness. This is important, because the response to selection and the subsequent adaptive microevolution of a trait, such as thickness is only possible when that trait exhibits additive genetic variation. Here, we estimated the narrow‐sense heritability (h²: ratio between additive genetic variance and phenotypic variance) for the traits ‘shell thickness’ and ‘shell length growth’ in a 34‐month‐old cohort of the mussel Mytilus chilensis obtained by using a half‐full sib design and grown in the field. Also, phenotypic and genetic correlations were estimated between both traits. We found that h² showed significant values for shell thickness (0.294 ± 0.194) and length (0.731 ± 0.379). The phenotypic correlation between both traits was positive and significant; however, the genetic correlation between these traits was not. These results suggest both traits can evolve adaptively by selection, but because these traits did not show genetic correlation, it is possible that selection pressure affecting one trait may not affect the other.     

Larval and post‐larval growth,spat production and off‐bottom cultivation of the smooth venus clam Chionista fluctifraga

Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off‐bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day^?1 during larval and post‐larval stages and 0.049 mm day^?1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off‐bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated.     

Divergent selection for shell length in two stocks of small abalone Haliotis diversicolor

To determine whether genetic improvement can be attained through a selective breeding programme, divergent selection for shell length was applied to two stocks of Haliotis diversicolor. Stock A was descended from the cross between males from a Japanese wild population and females from a Taiwan aquacultured population and Stock B was from the Taiwan cultured population, which had been successively cultured in mainland China for about 10 generations. The 10% largest and 10% smallest abalones for each of these two stocks were selected as parents for the large‐selected and small‐selected lines respectively. Equal numbers of abalone were randomly chosen from the two stocks to serve as parents for the control lines before the selection. The selected and control lines were reared under the same conditions at early juvenile, later juvenile and grow‐out stages. Stock A showed a significantly higher response to selection and realized heritability than Stock B (P<0.01). The large‐selected line of Stock A and Stock B grew 12.79% and 4.58% faster than their control lines on shell length respectively. The average realized heritability for shell length was 0.441±0.064 for Stock A and 0.113±0.013 for Stock B. Responses to selection were different at different ages in each stock and the body weights of the selected lines were significantly different from the control lines in both stocks at the grow‐out stage. Asymmetric responses to selection in the two directions were also observed in both stocks. Differences in response to selection and realized heritability between the two stocks are presumably due to genetic variability.     

长牡蛎壳金选育群体生长性状的选择效应

长牡蛎是一种世界性的养殖贝类,同时是我国最重要的经济贝类之一,壳色美观和快速生长是目前长牡蛎遗传育种的2个重要目标。2010年通过长牡蛎壳色性状的家系选育,获得了壳白、壳黑、壳金和壳紫4种壳色品系。实验以第二代壳金品系为基础群体,对长牡蛎壳金群体的生长性状进行定向选育,分析了长牡蛎壳金选育群体壳高性状的选择反应、遗传获得和现实遗传力。结果显示,养成阶段选择组的壳高均大于对照组,350日龄后表现出显著的生长优势;幼虫期,壳高性状的平均选择反应、遗传获得和现实遗传力分别为0.549±0.277、3.717%±2.611%和0.339±0.171,养成期分别为0.436±0.138、8.253%±1.014%和0.270±0.086。选择组的贝壳金黄色和外套膜金黄色比例分别提高了22%和10%。研究结果为长牡蛎壳金优良品系培育提供了重要基础资料。     

Phenotypic estimates and heritability values of Artemia franciscana

Artemia, in all stages of its life cycle, is suitable food for most diversified groups of aquatic animals. Although its size at different stages restricts its use as a food for some groups of fish, this problem can be overcome using selective breeding techniques. The formulation of any selective breeding programme calls for a proper understanding of the genetic architecture of the economically important traits of the population under study. Thus, heritability for certain important life history and reproductive traits was estimated in Artemia franciscana from the Great Salt Lake, Utah. In the present study, the sexwise heritability values for growth and reproduction traits were estimated using parent–offspring regression. The phenotypic parameters for the same traits are also recorded. The naupliar length was 487.0±2.0 and 490.6±1.8 μm for males and females, respectively, whereas the heritability values for naupliar length were 0.5851±0.2153 and 0.3766±0.1899 respectively. The length at 3 and 6 days of age were 1.87±0.03 and 4.10±0.08 mm, respectively, for males whereas 1.87±0.03 and 4.30±0.08 mm, respectively, for females. The heritability values for length at 3 and 6 days of age for males were 0.3272±0.3651 and 0.4965±0.2466, respectively, whereas the respective values for the females were 0.1167±0.3841 and 0.0222±0.2971. The estimates of length at first brood, pre‐reproductive period and number of offspring in first brood were 10.09±0.23 mm, 16.00±0.23 days and 53.57±1.37 days, respectively, whereas the heritability values for respective traits were 0.0403±0.1078, 0.3234±0.2874 and 0.3404±0.2202.     

The Larval Development,Metamorphosis and Juvenile Growth of the Turban Snail Lithopoma (Astraea) undosa (Wood, 1828) (Gastropoda:Turbinidae)

This work presents the embryonic, larval, and postlarval development of Lithopoma undosa (L. undosa) (20 ± 2 C and the effect of natural inducers on the larval metamorphosis. Embryonic development until hatching of the trochophore larva took 15 h. Early veliger larvae with well‐developed shell were after 24 h. At 48 h, the operculum was completely formed. Cephalic tentacles were visible after 72 h. Larvae reached competence 6 to 7 d after fertilization, and was characterized by the presence of branched cephalic tentacles. The effect of natural inducers was evaluated. The percentage of metamorphosis with diatoms and adult mucus was 94% and 58% respectively, differing from the 25% without inducer. When was repeated, the metamorphosis was 100%, and 16% with benthic diatoms. The initial mean size of the postlarvae was 0.316 ± 0.02 mm. After 264 d the juveniles had attained a mean size of 5.98 ± 0.16 mm. These results will not only be of use in the evaluation of the culture of L. undosa, but also in studies on the characterization of inducers.     

Comparison of experimental designs for estimating quantitative genetic parameters in fish

Four popular experimental designs for estimating variance components of additive genetic effects and (secondarily) dominance and maternal effects in fish (full‐sib families, half‐sib families, nested design and factorial design) were compared. The error variances of the estimators were formulated as functions of the true (hypothetical) values of genetic and environmental variances, depending on the experimental design considered, and whether the families were reared separately or mixed. Half‐sib families and rectangular (many sires×few dams) factorial design were most useful for the estimation of heritability. The nested design appeared much less adequate. The minimum experimental capacity for obtaining accurate estimates was 100 lots in separate rearing or 1000 fish in mixed rearing. A larger experimental capacity is required when dominance and maternal effects as well as heritability are to be estimated because these different estimations, requiring contradictory conditions, cannot be simultaneously optimized.     

Selection response and realized heritability for growth in three stocks of the Pacific oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

To estimate response to selection and realized heritability for shell height, a one-generation selection was performed in the Pacific oyster Crassostrea gigas using three stocks from China (stock C), Japan (stock J), and Korea (stock K). Applying about the same intensity of selection in the upward direction, three selected and three control lines were created, which were reared under the same environmental conditions at larvae, spat, and grow-out stages. Stock C and stock J showed significantly higher response to selection and realized heritability than stock K at spat and grow-out stages (P < 0.05). At harvest on day 360, the selected lines of stocks C, J, and K were 12.2, 12.2, and 7.9% larger than their control lines, respectively, for shell height. When averaged across the grow-out period, the genetic gain for stocks C, J, and K was 13.2 ± 1.2, 13.2 ± 1.0, and 7.2 ± 0.7%, respectively, and realized heritability was 0.334 ± 0.028, 0.402 ± 0.024 and 0.149 ± 0.027, respectively. The relatively high realized heritability estimate obtained for stock C and stock J indicates that there is genetic variation in the two stocks and that selective breeding by mass selection is very promising.     

Induced Spawning and Egg Quality Evaluation of Red Snapper, Lutjanus campechanus

Brood red snapper, Lutjanus campechanus, were captured from the wild and induced to ovulate by human chorionic gonadotropin (hCG) injection; eggs and sperm were manually stripped; and the eggs were artificially fertilized. Eggs were evaluated by the following egg quality parameters: buoyancy, fertilization, egg size, and oil globule size and number. The relationship of these egg quality parameters and brood characteristics (female size, fecundity, time of year, and response time to ovulation) to 36 h posthatch larval survival was considered. Injection of wild‐caught red snapper females with 1100 IU/kg of hCG resulted in 75% of the females ovulating. The average fecundity was 343,377 ± 30,805 eggs/kg, with a mean percent fertilization of 79.0 ± 1.74%. The mean percentage of floating eggs per spawn was 91.8 ± 1.75%. Mean egg diameter for floating eggs was 778.3 ± 2.09 μm, with a mean oil globule diameter of 117.5 ± 1.53 μm. Brood‐related characteristics were a better predictor of larval survival than postovulation egg characteristics. The percentage of floating eggs in a spawn was not correlated to larval survival. Spawns with eggs having a single oil globule had a similar larval survival as those eggs where multiple globules were common. No clear relationships were found for any one factor and larval survival, but rather a combination of factors was more predictive of survival, most notably spawn date, fecundity, and response time following hCG injection.     

Breeding and larval rearing of the camouflage grouper Epinephelus polyphekadion (Bleeker) in the hypersaline waters of the Red Sea coast of Saudi Arabia

This is the first report on the successful year-round natural spawning and larval rearing of Epinephelus polyphekadion (Bleeker) in captivity and under hypersaline water conditions of 42-43%₀ salinity in the Red Sea coast of Saudi Arabia. Although the fish spawned naturally once or twice a year during 1992-94 culture period, incorporation of cod-liver oil in the broodstock diet during the 1995 culture period enabled the fish to spawn continuously for 2-3 days in each month during March, April, May and August. The egg fertilization and hatching rates also increased during the 1995 spawning period. The egg fertilization rate varied from 90 to 100% with a mean of 96.5 ± 3.38%. The egg hatching rate varied from 70 to 95% with a mean of 83.1 ± 10.12%. The fertilized egg diameter averaged 757.3 ± 37.36 μm. There was a linear relation between the fertilized egg size and the egg hatching rate. The increase in the hatching rate relevant to the egg size was statistically significant (P < 0.01). The egg development time until hatching lasted for 19 h at 29°C. The newly hatched larval size ranged from 1.55-1.71 mm with a mean of 1.65 ± 0.052 mm in total length. The larval growth was slow in the early stages and the growth curve until metamorphosis showed a curvilinear pattern. Wide variations in larval size, range 22-47 mm with a mean of 33.40 ± 7.01 mm, were observed during the metamorphosis stage at day 50. No significant difference (P > 0.05) in growth and survival was observed between the larvae reared using white and grey coloured tanks. The larval survival up to metamorphosis was 1.6-4.7% with a mean of 2.98 ± 1.56% in the grey coloured tanks and 1.6-1.9% with a mean of 1.73 ± 0.16% in the white tanks. The results demonstrated the possibility of breeding E. polyphekadion under captive culture conditions. However, methods to improve the larval survival have to be pursued further for commercial farming of this species.