Juvenile scallops (<2 mm shell height) of three species (Placopecten magellanicus, Patinopecten yessoensis, Argopecten irradians) were fed mixed, unialgal cultures. Scallops were fed a total of six algal clones simultaneously and clearance rates were
monitored using flow cytometric techniques. In another experiment, scallops were presented with natural assemblages of particulate
matter as a food source. Data are presented on differences in clearance rates for the individual algal species as well as
size-related differences of algal clones, and uptake of chlorophyll vs. non-chlorophyll cells, both within and between scallop
species. Significant differences in clearance rates of individual algal species have been found within and between scallop
species. Particle selection does not appear to be based upon size alone and is apparently based on other characteristics of
the algae as well. The results demonstrate pre-ingestive sorting. 相似文献
In this study, we collected 709 specimens of the sharpbelly Hemiculter leucisculus from the Yuanjiang River at monthly intervals between May 2017 and January 2019. An increment was formed annually in the lapillar otoliths, with the formation of annuli occurring between May and August, and peaking in June. Fish spawned from April to October, with a peak period between May and June. The radius of the first annulus varied apparently among individuals, reflecting differences in the duration of the growth period prior to annulus formation owing to extended spawning seasons. Three types of first annulus observed could reflect differences in the periods when the fish were born. The age of sampled fish ranged from 0 to 4 years, among which 1- and 2-year age classes predominated. The mean standard length (SL) at age and growth rate of this population did not differ significantly from those of other native populations. Analysis of life history traits indicated no obvious correlation with either latitude or habitat, whereas SL distribution and age composition were found to vary along a latitudinal gradient. Furthermore, mean SL at age and growth rate showed differences between native and invasive populations. Relatively stable life history traits of this species may explain its dominant status in diverse ecosystems, with plasticity in terms of body size and growth contributing to its successful invasion of different habitats.
Probiotics have been widely used in aquaculture worldwide especially in China as antibiotics have been banned in aquaculture. In the present study, 27 potential strains were isolated from Rhynchocypris lagowskii Dybowski intestinal tract towards the assessment of their probiotic potential. Two potential probiotics were finally screened from the 27 candidate strains according to the results of enzyme-producing ability, in vitro against pathogens ability and antibiotic sensitivity test. The 2 potential probiotics were identified and confirmed on the basis of their colony morphology, biochemical characteristics, and 16S rRNA sequencing. The probiotic strains, LSG2-3–2 and LSG3-6, were identified to be Bacillus methylotrophicus and B. tequilensis, respectively. Further studies showed that LSG2-3–2 and LSG3-6 had excellent tolerance to high temperature (80℃), low pH (3–5), bile salts (0.3%), intestinal juice (10%), and gastric juice (0.5%). The adhesion rates of LSG2-3–2 and LSG3-6 in the in vitro intestinal mucosal adhesion model were 17.74% and 24.04%, respectively. Analysis of their bacteria surface adhesive proteins revealed that the lectins on the bacterial surface of LSG2-3–2 and LSG3-6 were mainly protein and glycoprotein properties, respectively. The adhesion receptor components in the mucus proteins of the two strains were all protein properties. The results of the inhibitory adhesion test indicated that LSG3-6 had a higher inhibitory effect on Aeromonas hydrophila and LSG2-3–2 had a better inhibitory effect on A. veronii. The biosafety assay confirmed that the isolates were not pathogenic to the host fish. Based on the presently observed characteristic features, it can be concluded that LSG2-3–2 (B. methylotrophicus) and LSG3-6 (B. tequilensis) retrieved from the digestive tract of R. lagowskii can be used for the healthy breeding and disease prevention of R. lagowskii.
