Resource allocation in yolk-feeding fish

Abstract

An insight is made into the main processes that occur in fish during endogenous feeding period. The ways in which yolk absorption rate can be measured are evaluated. Essential amino acids and polyunsaturated fatty acids are preferentially retained for incorporation into body tissue. Profound physiological and anatomical changes in yolk and a sequence of slow, fast, and a second period of slow absorption occur during the endogenous feeding period. Attempts to quantify the ontogenetic sequence are reviewed. Various methods of body size assessment are compared, and sources of bias in individual and population growth estimates are discussed. Several calorimetric methods are compared of which direct calorimetry using an oxygen bomb is the reference method. An advanced elemental analysis (CHNS) is a reliable technique that is adequate for early stages. Indices of growth potential are reviewed including a comparison of different measures, models and approaches used to estimate growth. Changes in body hydration, caloric value, content of lipids, protein, free amino acids (FAA) and minerals, and in content of RNA and DNA occur in early ontogeny. Ways to quantify metabolic rate are identified. Mean relative respiration rate of initial egg before activation is very low, about 20 mm 3 g À1 h À1 . Ontogenetic sequence in absolute metabolic rate of fish embryos and yolk-feeding larvae involves an increase through hatching to a peak at the time of first feeding ability, and a decrease under starvation. Models predicting the relationship between oxygen consumption and age in yolk-feeding fish are reviewed. Sequence of metabolic fuels begins with use of small molecules as carbohydrates, soon switched to FAA. Later lipids are progressively used, they provide energy for swimming activity. After yolk depletion body protein-bound amino acids are mobilised. In this review I focused on the major environmental variables as temperature, oxygen, salinity, pH, toxic xenobiotics, light, UV radiation, magnetic field and substrate, along with intrinsic factors as egg or body size, sex and genetic factors. A question was posed on how the extrinsic and intrinsic factors determine yolk absorption, growth and metabolic rates in yolk-feeding fish. Special attention is devoted to fish body size attained exclusively on yolk. A considerable variety of body size responses to temperature was found, for which several explanations are forwarded. Methodological progress made recently is characterised and the most conspicious advances in understanding of fish early life history are highlighted. Information derived from these studies can be used in management of fish populations in the field and to optimise activities in aquaculture.

Influence of spawning procedure on gametes fertilization success in Salminus hilarii Valenciennes, 1850 (Teleostei: Characidae): Implications for the conservation of this species

“…These studies can characterize the most important events during development, such as the total consumption of the yolk sac, the appearance of internal and external structures, mouth opening, and other characteristics (Sato et al, 1998;Nakatani et al, 2001;Sato et al, 2003;Borçato et al, 2004;Kamler, 2008). For carnivorous species, the exact timing of the mouth opening is important to indicate the time that the animal, until then considered to be within a closed system, enters into an open system, and therefore begins exogenous food intake.…”

The evolutionary puzzle of egg size, oxygenation and parental care in aquatic environments

“…First, under hypoxia, tissue differentiation rates can retard development, so that embryos from males kept in hypoxia may be at earlier stages of development resulting in smaller sizes [67,68]. Second, development may progress at similar rates but embryos are smaller due to less efficient anaerobic metabolic processes [69,70]. Third, quality of parental care (for instance, nutrients provided) may differ in normal and low O 2 conditions owing to the physiological stress imposed by hypoxia on the caring parent, affecting the Table 3.…”

First feeding and subsequent growth performances in piscivorous larvae of Chinese perch Siniperca chuatsi (Perciforms: Sinipercidae)

“…Effects of first feeding time on larval growth performance During endogenous feeding period, larvae may decrease absolute metabolic rate and show depressed growth under starvation, even before final yolk absorption (Kamler 2008). The results showed that larval growth of Chinese perch was sensitive to the timing of first feeding.…”

“…This might be due to the following three main reasons. First, the absolute metabolic rate has increased to a peak at the time of first feeding (Kamler 2008). Second, the digestive systems of Chinese perch larvae become functional immediately after first feeding (Wu et al 2007).…”