Improvement of nutritional quality of cultured sobaity sea bream,Sparidentex hasta (Valenciennes) muscle by preharvest feeding of finisher feeds

A 6‐month long study was conducted to improve the nutritional quality of the cultured sobaity bream, Sparidentex hasta by feeding them finisher feeds containing high docosahexaenoic acid (DHA) at the last two months of the grow‐out stage so that the muscle DHA level be increased at par to the wild. A grow‐out feed used from the beginning until the end of the trial was considered as the control (Diet 1). Experimental diets 2 and 3 were formulated to contain 9.0% DHA (e.g. 1.68 g DHA/100 g feed) and 10.5% DHA (2.20 g DHA/100 g feed), by incorporating high DHA tuna oil into a sea bream grow‐out diet. For comparison, a commercial finisher feed (Diet 4) from Skretting, Italy was also used. The results of this study demonstrated that fish fed DHA enriched finisher diets resulted in significantly (p < .05) better growth, feed utilization and higher muscle eicosapentaenoic acid (EPA) and DHA content compared to those fed grow‐out diet. The muscle DHA and EPA of fish fed finisher diets were also higher than those of the whole year average DHA and EPA content of wild sobaity. An organoleptic evaluation showed no significant (p > .05) differences between sensory attributes of muscle from cultured and wild sea bream. The results of the study demonstrated that feeding finisher feed enriched with DHA at the later part of the grow‐out operation, the n‐3 PUFA levels of cultured sobaity can cost‐effectively be increased at par to the wild.     

Genetic diversity and population structure of spottedtail goby (Synechogobius ommaturus) based on AFLP analysis

Larval dispersal may have an important impact on genetic structure of benthic fishes. To examine population genetic structure of spottedtail goby Synechogobius ommaturus, samples from five different locations of China and Kunsan population in Korea were analyzed by using amplified fragment length polymorphism (AFLP) technology. A total of 253 bands were identified from 91 individuals by 5 primer combinations and the percentage of polymorphic bands was 43.87%. The average gene diversity was 0.0794 ± 0.1470 and Shannon’s information index was 0.1279 ± 0.2138. The pairwise F_st values ranged from 0.022 to 0.201. The results of AMOVA analysis indicated that 90.54% of the genetic variation contained within populations and 9.46% occurred among populations. The gene flow estimates (Nm) demonstrated that different gene flow existed among populations from 0.994 to 11.114. No significant genealogical branches or clusters were recognized on the UPGMA tree. The results support the hypothesis that larval dispersal ability can be responsible for the genetic diversity and population structuring.     

矛尾复虾虎鱼物种命名有效性探讨

利用形态学和遗传学方法探讨斑尾复虾虎鱼和矛尾复虾虎鱼的亲缘关系及矛尾复虾虎鱼物种有效性.研究结果显示:两种虾虎鱼在量度特征上存在极显著的差异,但分节特征不存在显著差异;与斑尾复虾虎鱼相比,矛尾复虾虎鱼头长相对较小,而尾鳍相对较长.对两种虾虎鱼的线粒体DNA控制区片段序列进行比较分析,得到两种虾虎鱼的遗传距离仅为0.006,与种内距离相当;NJ和MP法构建的系统树也显示两种虾虎鱼间亲缘关系很近,两种间不存在显著差异.综上,矛尾复虾虎鱼并非有效物种,应为斑尾复虾虎鱼的同种异名.     

Seasonal changes in serum steroid hormones in a protandrous teleost, the sobaity (Sparidentex hasta Valenciennes)

Serum concentrations of 11-ketotestosterone, 11β-hydroxytestosterone, testosterone, testoster-one glucuronide, oestradiol and 17,20β -dihydroxy-4-pregnen-3-one (17,20β -P) were measured in the sobaity at monthly intervals through their second breeding season. Concentrations of the 11-oxygenated androgens in the males and of oestradiol in the females peaked during the spawning season in January-February, while maximum levels of testosterone were found in the summer when these steroids were low. Testosterone glucuronide showed two peaks, one in the post-spawning period as oestradiol and the 11-oxygenated androgens were falling and the other coincident with the summer peak of testosterone. 17,20β -P was detectable in only one male and one female fish in February. Serum concentrations of 11-oxygenated androgens are more reliable than those of oestradiol for determining the sex of sobaity, and may also be used as indicators of the occurrence of sex reversal. The seasonal pattern of serum steroids correlated well with the changes of sexual status of the gonads during regression and recrudescence observed histologically and suggests that oestradiol may be involved in the sex inversion of this species.     

Identity and typification of Navicula hasta (Bacillariophyceae)

The name Navicula hasta is regularly applied to large, heavily silicified Navicula specimens with lanceolate outlines, protracted ends, and relatively coarse, radiate, and lineolate striae that are more irregularly spaced around the central area. As such, Navicula hasta has been reported from numerous localities such as brackish water fossil sediments, oligotrophic ancient lakes and postglacial lakes. When the data for distribution of Navicula hasta are summarized, this species appears to be geographically and temporally widespread with a broad range of ecologic tolerances. Published reports for size range show that diatomists during the last century have differing concepts of the species starting with the disagreement between the protologue and one of the figures given by Pantocsek. Furthermore, an informal ‘type’ of Navicula hasta reported in 1980 does not match the protologue and is not unambiguously based on material Pantocsek had in his hands when describing his new species. We studied published reports of Navicula hasta and investigated material reported to contain Navicula hasta and its allies from the type locality (Köpecz), one of the fossil deposits reported to contain N. hasta (Bodos) and from ancient and other younger lakes worldwide. From our analyses, we document the variation and underappreciated diversity within the Navicula hasta group and set the stage for formal recognition of new species in subsequent papers. Herein, we formally propose a lectotype from among the original illustrations and designate an epitype for Navicula hasta based on Pantocsek's Köpecz material. Additionally, two new species, Navicula krenneri spec. nov. and Navicula pseudohasta spec. nov. are described and a lectotype of Navicula superhasta Lange‐Bertalot and Metzeltin is proposed.