Food ingestion in juvenile cod estimated by inert lanthanide markers – effects of food particle size
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Abstract Development of formulated starter diets and improvement of diets for juvenile marine fish species are major challenges in aquaculture. The ingestion rate may be regarded as a parameter for evaluating whether a diet particle is available, recognized, of adequate size, palatable, and preferred by small fish. In this study, we evaluated the effect of food particle size (150–3425 μm) on ingestion rate in juvenile cod (36–826 mg wet weight). Lanthanide oxides were used as markers. Several mixtures of lanthanide marker-labelled diets were produced by combination of the mono-labelled size classes. Each combination was fed for one, four, or seven days to groups of juvenile cod in separate tanks. After termination by anaesthetic, the fish were collected, individually weighed, and frozen until analysis. The amount of lanthanides in the homogenized fish was measured by inductively coupled plasma-mass spectrometry (ICP-MS). There were no significant differences in ingestion of any of the markers when given in a mixture of mono-labelled particles. Thus, the markers Y2O3, La2O3, Nd2O3, Dy2O3, and Yb2O3 may be used as inert tools for evaluating diet ingestion. The total intake of dry diet was about 13 mg g−1 body weight. The particle size that caused the highest food intake was less than 1.2 mm in all experiments.Keywords:
Inert
Juvenile polyps are usually seen in children and have peculiar histological aspects. They are rarely seen in adults.165 polyps have been endoscopically removed in our institute. There were 5 ceses of juvenile polyps among them (about 3%). It was difficult to differenciate them from adenoma endoscopically, but was easy histologically.It is regarded as there are no differences between juvenile polyps in children and those in adults. But it is desirable to record the latter as "non-juvenile" juvenile polyp because of their rarity.In this paper we reported endoscopical and histological appearances of 5 "non-juvenile" juvenile polyps.
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One behavioral tactic that juvenile mammals can use to resolve conflict with adults is the reversion to behaviors of an earlier developmental stage. Therefore, we examined the appearance, body posture, and ontogenetic differences of submissive crouch behavior between juvenile male and female guanacos from birth to 9 months of age in Torres del Paine National Park, Chile. On average, submissive crouches appeared 73 days after birth, and juvenile males displayed them more frequently than did juvenile females. Juvenile males also displayed more extreme body postures during submissive crouches than did juvenile females. Sex, group size, and season significantly influenced a juvenile's likelihood of displaying a submissive crouch.
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The feasibility of using inert anodes in aluminum electrolysis cells is discussed in this paper on the basis of the following aspects: the theory of employing inert anodes in aluminum electrolysis cells, requirements for inert anodes, the studying progress of inert anodes and cell types suitable for inert anodes Advantages and shortcomings of various inert anode materials are also analyzed in this paper as well as the feasible researching direction
Inert
Inert gas
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The present paper dealt with that the cultured zooplankonts were proper as initial feed for juvenile Clarias lazera and growing feed for youth in the pond.The results showed that the body length of four days old juvenile increased to 3 cm and above after feed the zooplankonts for 13 days with a 23.2-30.3℃ water temperature.The survival rate of juvenile was more than 60%.The width of mouth of four days old juvenile was about 760-900 μm.The cladoceran,copepods and chironomids were mainly taken by juvenile at earlier stage of the growing period before 13 days old.When the age of juvenile grew up to fourteen days and above,they mainly took rotifers,juvenile aquatic insects and mix feed instead of cladocerans,copepods and chironamids.The feeding proportion of juvenile was more than 90%,the fullness degree of stomach of the most juvenile arrived to 3-5 degree with cladoceran,copepods and chironomids.There was a linear relation between body length and days age,and an exponential function was shown between body weight and days age,and the same function was also shown between body length and body weight.The growth speed of body length was constant,but the growth speed of body weight was acceleation.
Juvenile fish
Clarias
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Analysis of biometric data of juvenile sockeye salmon caught during the run to sea in the channel from Nachikinskoe Lake was carried out in order to clarify the question of the minimum possible number of sclerites on the scales to the 1st annual ring. For the first time, the study of the features of the scale structure of juvenile sockeye salmon of different ages was carried out. The differences revealed between groups of individuals of different age categories are highly reliable not only in weight and length, but also in the total circuli number in the freshwater zone and circuli number to the first annual ring (6.0 ± 0.1 in yearlings, 3.9 ± 0.3 in two-year-olds); physiological explanation for these differences is proposed. On the basis of the scleritograms constructed, a comparison of other features of the scale structure of the juvenile migrants of different ages was carried out. The key characteristics obtained are recommended as clarifying criteria in reading the freshwater age of juvenile sockeye salmon in Nachikinskoe Lake.
Age structure
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Survival estimates for juvenile birds are rarely empirically derived and have been typically estimated as some percentage of adult survival. In particular, little information is available on survival when juveniles are independent of parental care or whether juvenile survival is sex biased. Additionally, little information is available about behaviors of juvenile birds that might be relevant to their survival. From 2010 to 2013, we radio tracked 71 independent juvenile Black-capped Vireos (Vireo atricapilla) in central Texas to estimate their survival and to quantify their behaviors. Using a known-fate model in program MARK, we calculated overall survival during the independent period to be 57% (86% for females and 28% for males). Males moved farther between consecutive locations than females and movement patterns varied substantially among individuals. Both sexes were frequently seen in association with conspecifics and heterospecifics. Half the males we tracked were observed singing, both sexes made many types of vocalizations, and the frequency of vocalizations did not differ between sexes. Whether behavioral differences contributed to survival differences between males and females will require further research. Our results indicate juvenile mortality is likely important for the population dynamics of this species and emphasize the need for studies of juvenile survival across a range of species and regions.
Animal ecology
Paternal care
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