Summary 1.As a first approximation, whole-body metabolic rate can be considered as the sum of metabolic rates of constituent cells. Yet, among several current explanations of metabolic rate scaling, only two explicitly invoke cell architecture of organisms: (1) the Metabolic Theory of Ecology, which predicts size invariance of metabolically active cells, such as erythrocytes and (2) the cell metabolism hypothesis postulating partial dependence of metabolic scaling on the cell size (CS), which is mediated by nucleus ⁄ genome size variation.2. Here, we tested (1) and (2) by comparing standard metabolic rate (SMR), erythrocyte size (used as a proxy of CS) and nucleus size (NS) between diploid and triploid individuals of a small fish (body mass of c. 3 g) belonging to the Cobitis taenia hybrid complex. 3. We demonstrated a positive correlation of CS with genome ⁄ nucleus size and an inverse relationship between those traits and SMR. SMR scaled to body mass with a 0AE92 ± 0AE05 exponent, which significantly differed from the ¾ value, while CS scaled with body mass with an allometric exponent of 0AE05 ± 0AE007, which significantly differed from 0. Ploidy level explained c. 85% of CS variation. 4. Our results provide empirical support for CS and genome ⁄ nucleus size being important determinants of metabolic rate variation and consequently, its allometric scaling. They call attention to the significance of a long-neglected integration of cellular and organismal perspectives in studies of body size-metabolic rate relationships and their consequences for energy utilization in the wild.

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Wild spawners of common bream, Abramis brama, were caught in the Kortowskie Lake (north Poland) and transported to a hatchery for artificial spawning. Fish were hormonally induced using GnRH analogue combined with metoclopramide (ovopel). The results of bream reproduction in captivity were compared with fish treated with the combination of hCG and CPE and with control group injected saline. Males from treated groups produced significantly more milt (over 4.3 ml/kg vs. 2.1) of better qualities: spermatozoon concentration (over 9.3 × 10 9 vs. 6.8) and motility (over 85% vs. 62). Females from the control group did not spawn whereas those from hormonally induced groups ovulated: 62% after CPE treatment and 100% after GnRHa treatment. Generally, the fish after ovopel stimulation showed the best hatchery parameters.

Induced spawning in bream, Abramis brama (L), was studied using acetone‐dried common carp pituitary (CP) and bream pituitary (BP) with or without the addition of human chorionic gonadotrophin (hCG). The total dose administered to fish was of 5.0 mg kg−1 BP or 4.0 mg kg−1 CP with or without 2000‐2200 IU hCG kg−1 for females and 2.5 mg kg−1 BP or 2.0 mg kg−1 CP with or without 1000–1100 IU HCG kg−1 for males. In all male treated groups 100% of spermiation was observed: in females the most effective method was a triple injection with hCG and carp pituitary, resulting in 79% of females ovulated (over 68% of eyed eggs). Biological quality of eggs, expressed as a percentage of eyed eggs, was negatively correlated with time elapsing between resolving (final) injection and ovulation. Spawning success, expressed as a value of Se (spawning effectiveness coefficient), was higher in fish treated with triple injection.