An acoustic based approach to evaluate the effect of different diet lengths on feeding behavior of Litopenaeus vannamei

Studying shrimp feeding behavior is challenging and, traditionally, studies have been using direct visual observation or video recordings with image analysis under laboratory conditions. Passive acoustics monitoring (PAM) is a non-invasive approach to study feeding behavior of penaeids, as their mandibles emit clicking sounds during feed ingestion. Considering the wide variation available in shrimp diet lengths, our knowledge is still limited about their effects on feeding behavior. The present study was designed to use acoustics to evaluate the feeding behavior of Litopenaeus vannamei fed different diet lengths. A commercial pelleted diet with similar diameter (2.4 mm) and three different lengths was used as treatments “small” (2.35 mm), “medium” (4.26 mm) and “large” (8.42 mm). Three separate trials were performed with fastened shrimp (20 g), using omnidirectional hydrophones and external audio recorders. Our approach started with the characterization of the click acoustic parameters produced by three shrimps when fed the different diet lengths in anechoic chambers (15 L). We then analyze the number of clicks produced per pellet and duration of the clicking activity when shrimp fed a single pellet in individual tanks (1 L). Finally, the acoustic energy of feeding activity and feed consumption, as well as theirs relationship to predict feed intake was evaluated in aquaria (70 L) with five shrimps. The acoustic parameters of isolated clicks were not affected by the different diet lengths, however, doubling the length of the pellet resulted in doubling the number of clicks emitted during feeding activity. The duration of clicking activity per pellet indicated that small pellets are consumed 2.9 and 4.7 times faster than medium and large pellets, respectively. Furthermore, feeding acoustic energy of small pellets decreased rapidly after feed offer, as their faster consumption probably contributed to shrimps achieved satiety earlier than larger diets. Feed consumption was similar among diets length, but significantly correlated with the feeding acoustic energy emitted by L. vannamei, which is a breakthrough in feeding behavioral research. The results highlight the potential and possibilities of an acoustic approach to estimate feed consumption, as well as an alternative to traditional methods in feeding behavioral studies to improve efficiency of feed management.     

Comments on “Plantation development: Economic analysis of forest management in Fujian Province,China”

This short article reexamines Zhang et al., 2010 (Forest Policy and Economics 2010, 12, 223–230) who concluded that forest expansion in China will continue due to the high economic benefit of forest plantations. It is suggested that their conclusion rested on data mistakes and problematic calculation, and might be misleading. A more realistic calculation is made.     

大连市中心区声环境功能区划调整研究

在分析了大连市中心区声环境功能区划调整必要性的基础上,全面评估了现有区划实施效果,以问题为导向提出了区划调整的方法体系,并阐述了区划调整结果的可行性,为城市环境噪声管理和防治提供科学依据。     

探析大学图书馆期刊资源的开发利用

分析大学图书馆期刊开发和利用现状,解放思想、更新观念、优化馆藏期刊结构,多层次地开展信息服务,提高政治业务素质,能更好地发挥期刊的作用。     

Numerical simulation of deformations and forces of a floating fish cage collar in waves

The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar.     

Dihydrochalcones and homoisoflavanes from the red resin of Dracaena cochinchinensis (Chinese dragon's blood)

Two new dihydrochalcones, 4-hydroxy-2,4′-dimethoxydihydrochalcone (1) and 3,4′-dihydroxy-2,4,6-trimethoxydihydrochalcone (2), and a new homoisoflavane, 7,3′-dihydroxy-8,4′-dimethoxyhomoisoflavane (3), along with 12 known compounds (4–15), were isolated from the red resin of Dracaena cochinchinensis (Chinese dragon's blood). Their structures were assigned by a variety of spectroscopic techniques. Diversity of cleavage pathways were proposed for dihydrochalcones and homoisoflavanes based on the mass spectroscopic behaviors of those identified compounds using hybrid ion trap-time of flight mass spectrometry. All the compounds were evaluated for their inhibitory effects on nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophages, and compound 9 exhibited mild inhibition of NO production in this assay with IC₅₀ value of 50.3 μM.     

诺氟沙星在菲律宾蛤仔、海湾扇贝体内的残留和消除规律研究

首次报道了诺氟沙星在菲律宾蛤仔和海湾扇贝体内的残留和消除规律.在水温为(20 ±1) ℃的条件下,菲律宾蛤仔和海湾扇贝的混养系统中,以50 mg/L剂量连续10 d投喂诺氟沙星,取鳃、内脏团、闭壳肌等组织,进行反相高效液相色谱法测定其浓度.结果表明:诺氟沙星在3种组织中消除速率快慢不一,鳃为诺氟沙星残留的靶组织.其在菲...     

饥饿胁迫对虾夷扇贝几种免疫因子的影响

在(17±1)℃条件下,研究了壳长(8.83±0.52)cm的虾夷扇贝在不同饥饿时间(5、10、15、20、30 d)处理后,血液中血细胞总数、血细胞吞噬水平、酸性磷酸酶、过氧化物歧化酶的变化。结果表明,扇贝的血细胞总数随着饥饿时间的延长逐渐降低,饥饿20 d以上的扇贝血细胞数明显降低,与投喂组差异极显著(P<0.01),扇贝血细胞吞噬率和酸性磷酸酶活性呈现出先小幅上升后下降的趋势,饥饿253、0 d与投喂组差异显著(P<0.05),饥饿253、0 d的扇贝过氧化物歧化酶的活性有所升高,饥饿30d,与投喂组差异显著(P<0.05)。试验表明,饥饿超过20 d,扇贝的免疫系统受到较为严重的破坏。     

拟除虫菊酯和有机磷农药对三种扇贝稚贝的急性毒性效应

采用静水实验法测定拟除虫菊酯类和有机磷类农药对三种扇贝稚贝的急性毒性效应.结果表明:联苯菊酯对海湾扇贝、栉孔扇贝和虾夷扇贝稚贝24 h的LC50的分别为1.460、1.662和2.909 mg/L;辛琉磷对海湾扇贝、栉孔扇贝和虾夷扇贝稚贝24 h的LC50的分别44.598、182.167和39.334 μg/L;马拉...