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.     

盘形振动上料器的一种系统模型和模拟

推导出一种盘形振动上料器的数学模型,在此基础上分析了固有频率、振型等动态性能,进行了系统参数计算。并利用动态分析软件ADAMS进行了建模仿真,可直观地研究零件的一致化排列过程和输送的速度。实践证明,利用这种模型进行盘形振动上料器的研制工作十分有效。     

A test of the individual feeding activity and food size preference in rainbow trout using demand feeders

Feeding activity and food size preferences were investigated in three groups of rainbow trout with initial weights ranging from 200 to 1000 g. Fish were given the option of releasing food from either of two demand feeding devices that contained either 6 mm or 9 mm food pellets. Individual biting activity (to activate release of food) was continuously monitored using specially designed passive integrated transponders (PIT-tags). In each of the groups, biting activity was strongly influenced by three individuals, which accounted for 70–85% of the total. Thus, high bite activity by few individuals indicates the development of social dominance hierarchies. There was no statistically significant correlation between number of bites and growth rate, indicating that the fish that operated the demand feeders did not gain any growth advantage. Trout that dominated the actuation of the feeders were found among both medium- and large-sized fish. There was no evidence of active food size selection, and the fish that most frequently operated the feeders defended one area of the tank rather than preferring the trigger that would have delivered food of the optimal size.     

Digestion of peptidic residues in humic substances by an alkali-stable and humic-acid-tolerant proteolytic activity in the gut of soil-feeding termites

Previous feeding experiments have shown that soil-feeding termites (Termitidae: Termitinae) preferentially mineralize the peptidic component of synthetic humic acids, but nothing was known about the mechanism involved in digestion. Here, we studied the hydrolysis of humus-stabilized peptides in gut extracts of Cubitermes orthognathus by measuring the release of radiolabel from ¹⁴C-peptide-labeled synthetic humic acids. Gut extracts exhibited proteolytic activity over a wide pH range (from 4 to 12) with a maximum at about pH 8. The highest activity was located in the gut section containing the midgut and the extremely alkaline (up to pH 12) mixed segment. Chemical hydrolysis at in situ pH (up to pH 12) was negligible. Proteolytic activity in the hindgut fluid was generally relatively low, but alkaline proteases dominated in the anterior hindgut. When compared to other alkaline proteases, the proteolytic activity of gut extracts had a higher alkali-stability and tolerance to humic acids than subtilisin and an alkaline protease of Streptomyces griseus. Gut extracts also hydrolyzed the peptidic component of synthetic humic acids more efficiently than the commercial enzymes. Together with previous results, this study strongly supports the hypothesis that soil-feeding termites mobilize and digest the peptidic component of organic nitrogen in soil humic substances by a combination of proteolytic activities and extreme alkalinity in their intestinal tract.     

Estimation of genetic parameters of feed intake and daily gain in Durocs using data from electronic swine feeders

Genetic parameters for daily feed intake (DFI, g/day) and daily gain (DG, g/day) were estimated using records of 1916 Duroc boars from electronic feeder stations. Management was limited and resulted in varied ranges of age and weight on test. Boars were housed in 102 pens, each equipped with one feeder, and allowed ad libitum feeding. Weekly averages of DFI and DG were used due to large variation in daily records. Six traits were defined as DFI and DG during 85–106 (period 1), 107–128 (period 2) and 129–150 days of age (period 3). A six‐trait model included age as a linear and a quadratic covariate for DFI and a linear covariate for DG with a fixed effect of year–week–pen and random effects of litter, additive genetic animal and permanent environmental animal. Variance components were estimated by a Bayesian approach using Gibbs sampling algorithm. Estimates of heritability for respective periods were 18%, 12% and 10% for DFI and 21%, 11% and 10% for DG. Genetic correlations between DFI and DG in the same period were 0.70, 0.73 and 0.32 for the respective periods. DFI and DG obtained from automatic feeders can be analysed to reveal variation across testing periods by using weekly averages when many monthly averages are incomplete.     

Effect of the presence of nectar feeders on the breeding success of Salvia mexicana and Salvia fulgens in a suburban park near México City

The use of nectar feeders has grown a lot as a result of people wanting to attract hummingbirds to their gardens. This has caused an increment in the density and diversity of these birds in urban and suburban habitats. The feeders not only represent a bonanza resource for hummingbirds but they can also result in reduced visitation to native plants. We experimentally assessed the effect of placing nectar feeders in the vicinity of two native plant species in a suburban area of Mexico City. The plants with feeders showed a reduced visitation rate and in one case (Salvia fulgens) produced fewer seeds than the controls. Salvia mexicana was not only visited by hummingbirds but it was also by bees that were not attracted to the feeders, probably resulting in the lack of effect on this plant. Native plants in urban and suburban habitats can be threatened by reduced visitation rates and reduced seed sets resulting from the use of feeders.     

Vertical distribution of nematodes in arable soil under grass (Festuca pratensis) and barley (Hordeum distichum)

Summary The connection between faunal composition and soil factors is discussed in this study on vertical distribution of soil nematodes under grass and barley. The investigation was undertaken on the field site of a Swedish integrated research project Ecology of Arable Land. The Role of Organisms in Nitrogen Cycling. Higher nematode number (7.6 × 10⁶ m^–2) and biomass (340 mg dry wt. m^–2) were found under a 4-year-old grass ley than under barley (5.0 × 10⁶ m^–2; biomass, 136 mg dry wt. m^–2). Plant feeders dominated under the grass ley (3.2 × 10⁶ m^–2 whereas under barley the bacterial feeders (2.4 × 10⁶ m^–2) were the most abundant feeding group. Number, biomass, mean individual size and various community parameters indicated a much better nutritive situation for the nematodes under grass than under barley. The vertical changes in the various parameters, including proportion of egg-carrying females, indicated an increasing food shortage for the nematode populations towards greater depths. In the top soil, predation could be an important factor in regulating nematode number.Dedicated to the late Prof. Dr. M.S. Ghilarov     

BRL饲细胞及血清浓度对体外小鼠精原干细胞的影响

分别以大鼠肝细胞(BRL)或小鼠胚胎成纤维细胞(STO)为饲养层．采用含5％、10％及20％胎牛血清的培养液，培养6日龄小鼠生精上皮细胞，研究饲养层和血清浓度对精原干细胞生物学行为的影响。结果表明：在培养的第1周内，2个及4个连成串的精原细胞合胞体数量明显增加，同时大多数精原细胞逐渐退化。培养1周后，大多数精原细胞经短暂的存活及分裂活动后退化消失，培养体系中仅保留下少量单个及由细胞间桥相连的双个及4个成串或成团的A型精原细胞。这些细胞在随后的培养过程中，不表现明显的分裂活动，呈圆球形，表达碱性磷酸酶。不同条件培养体系中的精原细胞及精原干细胞的生物学行为无明显不同，培养20～30d时均有少量精原干细胞存活。这说明BRL细胞能用作饲养层促进精原干细胞存活，但对其更新性增殖没有明显作用；培养液中高浓度胎牛血清对精原干细胞存活和增殖无明显影响，但能促进睾丸体细胞增殖。     

New sites expanding the “Sardinian cold‐water coral province” extension: A new potential cold‐water coral network?

相似文献   

Effects of fungivorous and predatory arthropods on nematodes and tardigrades in microcosms with coniferous forest soil

Effects of fungivorous and predatory soil arthropods on free-living nematodes and tardigrades were studied in a factorial microcosm experiment. A stepwise increase in faunal complexity was obtained by adding soil arthropods to defaunated humus samples from an irrigated+fertilized and an untreated stand of Scots pine. The effects were assessed after 103 and 201 days at 15°C and a soil moisture content of 50% water-holding capacity. The study showed that a diverse community of fungivorous arthropods (collembola and oribatid mites), present in numbers similar to those in the field, reduced the abundance of nematodes. A complete community of fungivorous and predatory arthropods (e.g., gamasides, spiders, and cantharid larvae) further strengthened this repressive effect. Certain nematode genera were more affected than others. Tardigrades seemed to be efficient predators on nematodes, but their numbers were, in turn, strongly reduced by predatory arthropods. Because predatory arthropods fed on both nematodes and their tardigrade predators, the impact of arthropod predators on nematode regulation was greater than it appeared to be on the basis of nematode numbers. Humus type also interacted with the other factors. Nematode numbers were initially higher in the untreated humus than in the irrigated+fertilized humus. However, because tardigrade populations increased only in the untreated humus, nematode numbers decreased more in this humus than in the irrigated+fertilized humus. The study demonstrates that nematode abundance can be regulated by a number of types of interacting predators.