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Discus (Symphysodon spp.), a valuable ornamental species (mean initial weight 4.40–4.65 g) were fed five isoenergetic (gross energy: 200–209 kJ g–1), semipurified diets (casein, gelatine and Danish fish meal as protein sources) twice a day to satiation for 12 weeks. Five levels of protein were evaluated (350, 400, 450, 500 and 550 g kg–1 diet) and each fed to four replicates. Growth rate increased significantly with protein level up to 500 g kg–1 diet and then decreased. Feed conversion rates (FCRs) ranged from 2.2 to 3.8, varying inversely with observed growth rate. A similar trend was also observed in the efficiency of protein utilization (PER). Analysis of dose (protein level)‐response (growth rate) with second order polynomial regression suggested a requirement of 449–501 g kg–1.

Epidermal structures of three species of Periophthalmus (Ps.) and two species of Periophthalmodon (Pn.) were investigated in relation to their lifestyle. All species of both genera lack a dermal bulge, which species of other two oxudercine genera, Boleophthalmus and Scartelaos, have in their epidermis. In Periophthalmus and Periophthalmodon species, which are highly terrestrial, the middle cells are well developed in the epidermis and the capillaries are distributed in the surface of the epidermis on the head and dorsal body. In Periophthalmus species and Pn. septemradiatus, the capillaries and blood vessels are also distributed in the epidermis of the abdomen, superficially in Ps. modestus and deeply in other species. In Ps. modestus, the capillaries are also densely distributed on the surface of the epidermis in the caudal area, whereas in other species, the epidermal capillaries and blood vessels of this area are located deep with a very low density. In Pn. schlosseri, the epidermal capillaries are not found in either the abdominal area or caudal area. A comparison of the distribution of epidermal capillaries among Boleophthalmus, Periophthalmodon, Periophthalmus, and Scartelaos species revealed that the skin makes a larger contribution to respiration in the species having a more terrestrial lifestyle. Goblet mucous cells are completely lacking in Periophthalmus species, whereas slimelike materials were often found on the skin surface of Periophthalmus species. This finding suggests that Periophthalmus species have some unknown mechanism for producing mucus. In Pn. schlosseri, exposure of the dense capillary net on the surface of the head is likely to increase cutaneous respiration, but it also makes the fish an attractive target of bloodsucking insects.

Abstract. Many species of chironomids undergo their immature development in habitats that rapidly change in suitability, such as rain pools, phytotelmata, freshly filled ponds or soil layers that seasonally dry out. Strategies for the utilization of these habitats can be divided into two groups: i) physiological or behavioral adaptations of larvae, which enable them to survive unsuitable conditions (in situ resistance) or ii) repeated recolonization of temporarily suitable habitats. In situ resistance, includes desiccation or frost resis tance, often in combination with cocoon building and migration of larvae into the sediment. Generally, the species that use the recolonization strategy tend to be better at migration and have a higher fertility and shorter development. Recolonization may include only temporary habitats or temporary habitats and some more stable habitats as well.