Ecological separation by ecomorphology and swimming performance between two congeneric fish species

The high diversity of freshwater fish species reflects a great morphological plasticity. Understanding the relationship between swimming capacity, morphology and habitat use may be important to predict the chances of finding a species at an anthropized environment. The swimming capacity and morphological aspects of two sympatric species of Characidium, and for which spatial segregation in different hydraulic habitats is known, were compared in this study. Twenty-one individuals of Characidium fasciatum Reinhardt, 1867 and 23 individuals of Characidium cf. zebra Eigenmann, 1909 were captured and used for the evaluation of the swimming capacity and ecomorphological attributes. The swimming capacity of each species was obtained by measuring critical and relative velocities. A total of 12 ecomorphological attributes correlated with habitat use and swimming characteristics were also compared. The Mann-Whitney mean test showed that the swimming capacity of C. fasciatum was greater than that of C. cf. zebra, and the standard length of the individuals explained 12.42% of the variation in their capacity to withstand water flow. Both species were morphologically distinct in the relative length of the caudal peduncle, ventral flattening index and the relative area of the pectoral fin. The relative area of the pectoral fin alone accounted for 16.71% of the differences in the ability to resist the water flow and which were not explained by body length. Our results showed that two species differed in the ecomorphological space and in their swimming capacity, supporting the hypothesis that the greater the hydrodynamism, the better a fish is able to withstand the water flow, and that this capacity is correlated with the morphological characteristics linked to the swimming activity of the fish.

THE EFFECT OF ACUTE CONSUMPTION OF HYDROLYZED OILS ON SWIMMING CAPACITY ENDURANCE OF MICE (MUS MUSCULUS)

Objective: The aim of this study was to investigate the effect of hydrolyzed oils of different fatty acids composition on swimming capacity of mice.Methods:The oils used were Virgin Coconut oil (VCO) and Palm Kernel oil (PKO) as medium chain triglyceride (MCT) oils, Palm oil and Corn oil as long chain triglyceride (LCT) oils. Hydrolysis of the oil was performed with Rhizomucor miehei lipase enzyme. The mice were acclimatized and tested motoric to select the mice and divided into twenty groups, each group consisted of 5 mice. Each oil in the experiment were 0.1 ml, 0.2 ml, 0.4 ml/ 20 g BW, positive control was caffeine 13 mg/kg bw. Then, the mice were placed in a glass aquarium. Then swimming capacty endurance was measured.Results:.Non-hydrolyzed oils with dose of 0.1ml significantly induced swimming capacity of mice compared with negative control (distilled water) from 184.8 increased to 248.0 seconds by MCT oil, to 239.8 seconds by unsaturated LCT oil and to 214.8 seconds by saturated LCT oil. The hydrolyzed oils increased swimming capacity ± 65% by hydrolyzed MCT oils, ±54% by hydrolyzed unsaturated LCT oil and 21% by hydrolyzed saturated LCT oil. The hydrolyzed corn oil at high dose (0.4ml) was more effective to increase swimming capacity than saturated MCT (VCO and PKO) and LCT oil (palm oil).Conclusion:The results suggest that hydrolyzed MCT and LCT oils are more effective to increase swimming capacity than non-hydrolyzed.

THE EFFECT OF ACUTE CONSUMPTION OF HYDROLYZED OILS ON SWIMMING CAPACITY ENDURANCE OF MICE (MUS MUSCULUS)

Objective: The aim of this study was to investigate the effect of hydrolyzed oils of different fatty acids composition on swimming capacity of mice.Methods:The oils used were Virgin Coconut oil (VCO) and Palm Kernel oil (PKO) as medium chain triglyceride (MCT) oils, Palm oil and Corn oil as long chain triglyceride (LCT) oils. Hydrolysis of the oil was performed with Rhizomucor miehei lipase enzyme. The mice were acclimatized and tested motoric to select the mice and divided into twenty groups, each group consisted of 5 mice. Each oil in the experiment were 0.1 ml, 0.2 ml, 0.4 ml/ 20 g BW, positive control was caffeine 13 mg/kg bw. Then, the mice were placed in a glass aquarium. Then swimming capacty endurance was measured.Results:.Non-hydrolyzed oils with dose of 0.1ml significantly induced swimming capacity of mice compared with negative control (distilled water) from 184.8 increased to 248.0 seconds by MCT oil, to 239.8 seconds by unsaturated LCT oil and to 214.8 seconds by saturated LCT oil. The hydrolyzed oils increased swimming capacity ± 65% by hydrolyzed MCT oils, ±54% by hydrolyzed unsaturated LCT oil and 21% by hydrolyzed saturated LCT oil. The hydrolyzed corn oil at high dose (0.4ml) was more effective to increase swimming capacity than saturated MCT (VCO and PKO) and LCT oil (palm oil).Conclusion:The results suggest that hydrolyzed MCT and LCT oils are more effective to increase swimming capacity than non-hydrolyzed.

Guppies prefer to follow large (robot) leaders irrespective of own size

Body size is often assumed to determine how successful an individual can lead others with larger individuals being more likely to lead than smaller ones. However, direct evidence for such a relation is scarce. Furthermore, even if larger individuals are more likely to lead, body size correlates often with specific behavioral patterns (e.g., swimming capacity) and it is thus unclear whether larger individuals are more often followed than smaller ones because they are larger or because they behave in a certain way. To control for behavioral differences among differentially-sized leaders, we used biomimetic robotic fish – Robofish – of different sizes. Robofish is accepted as a conspecific by live guppies (Poecilia reticulata) and provides standardized behaviors irrespective of its size. We specifically asked whether larger leaders are preferentially followed when behavior is controlled for and whether the preferences of followers depend on their own body size or their risk taking behavior (‘boldness’). We found that live guppies followed larger Robofish leaders closer than smaller ones and this pattern was independent of the followers’ own body size as well as risk-taking behavior. This is the first study that shows a ‘bigger is better’ pattern in leadership in shoaling fish that is fully independent of behavioral differences between differentially-sized leaders and followers’ own size and personality.

Performance of a fish pass for multiple species: Scale model investigation

Artificial fish passes are often the most effective solution to restore the ecological continuity of a dammed river. Such a pass can be built for specifically targeted fish species, based on the existing knowledge on its swimming capacity and behaviour. Usually, a wider range of possible species are present in the river and may use the fish pass. In the present study, a vertical slot fish pass has been designed for salmonid fish (namely Atlantic salmon Salmo Salar). This fish pass layout was initially tested using a scale model where juvenile fish were introduced. The study has now been extended to other species, some of them having weaker swimming capacity: bleak (Alburnus alburnus); chub (Squalius cephalus); and bullhead (Cottus gobio). Fish behaviour in the pass was observed using PIT-tag and video. PIT-tag tracking enabled to characterise the capability of the fish to cross the whole fish pass. Video recording was used to analyse in more details the behaviour of the fish in a specific pool.