The starvation-induced ultrastructural modifications in the hepatocytes were reversed when Siganus guttatus resumed feeding on a suitable feed. The liver cells regained their structural integrity soonest when the fish was refed Chaetomorpha, whereas the other diets tested promoted inferior results or even caused deleterious effects. Prolonged feeding on sucrose provided insight on the nutritional orientation of this herbivorous fish. A 14-day starvation period resulted in the mobilization of fuel reserves indicated by a decrease and total loss of glycogen and lipids, respectively. Organelle morphology was slightly affected by the short-term fast, but was severely disturbed as the fish were deprived of food over prolonged periods . Severe starvation was demonstrated through the deformation of the nuclei and the swelling of the mitochondria. These findings provide support on the practicability of liver ultrastructural methods as supplementary tool in diagnosing the nutritional state of fish.

The pituitary gland of the milkfish, Chanos chanos, was studied at different stages of sexual maturation and spawning. Consecutive median sagittal sections were treated with a range of stains to demonstrate the different cell types and regions. The milkfish pituitary consists of a neural component, the neurohypophysis, and an epithelial component, the adenohypophysis, which in turn consists of three regions: the rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). However, unlike most teleosts, the pituitary gland of the milkfish is encased in a bony chamber, has dorsal and ventral lobes and extends anteriorly from its point of origin at the base of the brain. PAS (+) basophils are found in all regions of the adenohypophysis, but mostly in the proximal pars distalis. These cells undergo hypertrophy and hyperplasia during sexual maturation, shrinkage and degranulation during spawning.

The nutritive value of two species of earthworms, Eisenia foetida and Eudrilus euginae and the marine annelid, Nereis sp. in P. monodon juvenila diets was determined in two separate experiments. Percentage weight gain and survivla were higher with diets containing Eisenia foetida compared to those of diets with Nereis sp. Diets containing dried worm meal were also better compared to those with frozen worms incorporated in the "wet" form. Incorporation of earthworms at 10% level in the diets improved growth and survival when compared to a control diet. When 30% of Eudrilus euginae was used to replace fish meal in the diet, weight gain and survival of animals were higher compared to those of diets with fish meal.

Different Artemia cyst samples harvested from the San Francisco and the San Pablo Bay regions (California, U.S.A.), and suspect because of their poor nutritional performance in fish and crustacean farming, have been analysed for their chlorinated hydrocarbon and fatty acid content. These results have been correlated with survival, growth, and biomass production of larvae of the marine crustacean Mysidopsisbahia Molenock fed those different Artemia in a standard culture test. Differences in chlorinated hydrocarbon content do not correlate with differences in mysid culture performance. Fatty acid profiles reveal three groups of Artemia batches with high, intermediate, and low levels of the highly unsaturated fatty acid 20:5ω3. The production yield of the mysid larvae could be correlated with the relative level of the 20:5ω3 fatty acid in the Artemia nauplii.

A population of juvenile milkfish, C. chanos (Forsskaal) was studied in a small mangrove lagoon in Naburut Island, central Philippines. Several size groups of milkfish occurred in the lagoon as a result of its periodic connection with the sea. Body-weight to fork-length relation was: log W = - 5.2991 + 3.2388 log L, similar to that of pond-cultured specimens. In Naburut lagoon, juvenile milkfish take in primarily blue-green algae, as well as mangrove and seagrass debris, diatoms and detritus. The condition factor of fish caught during the day from May to Nov. stayed constant, indicating that lagoon conditions for growth in terms of food did not change markedly during the year. The monthly size-frequency distribution shows that juvenile milkfish in the lagoon grew at a rate of 7 to 9 mm \(wk^{-1}\) in 1979. Compared with pond-cultured specimens, their growth rate was lower during the first month but higher during the second month in the nursery. The limited area and depth of Naburut lagoon probably set the limit to the size of juvenile milkfish; these can be sustained there to just 150 to 180 mm fork length.

Captive Lates calcarifer broodstock at Tigbauan, Iloilo (Philippines) were implanted with cholesterol-based pellets of the LHRH analogue D-Trp⁶-desGly¹⁰-LHRH ethylamide or D-hArg(Et₂)⁶, Pro⁹-NHet-LHRH at doses between 9.0 and 23.5 μg/kg body weight. In May, one of ten LHRH-treated females released partially hydrated ova into the tank 4 days after implantation. In July, at least one (and probably four) of five LHRH-treated females spawned in the tank 2 days after implantation; 2.6 million hatchlings were collected. In August, both LHRH-treated females spawned in the tank 2 days after implantation; 978 000 hatchlings were collected. None of the sham-operated control fish spawned in any of the experiments. Captive Siganus guttatus broodstock implanted with silastic-based pellets of the LHRH analogue D-Nal (2)⁶LHRH spawned 1–2 days earlier than sham-operated controls.

Identification and examination of the physiological characteristics of Pseudomonas sp. isolated from fry of Sarotherodon niloticus (L.) was conducted. Based on morphological and biochemical tests, the bacterium was identified to be a strain closest to Pseudomonas fluorescens. In vitro physiological growth patterns at varying temperatures, NaCl concentrations, and pH were observed for a maximum of eleven days incubation while growth of the test bacterium into various water media were observed for a maximum of 148 days. Bacterial growth occurred between 10° to 41°C with optimum growth at 25° to 30°C. The bacterium tolerated NaCl concentrations of 0 to 50 ppt. Optimum growth, however, was obtained from 0 to 15 ppt. It was found that growth was possible only at pH 5.0 to 9.7. Optimum growth occurred at pH ranging from 5.7 to 8.4. Inoculation of the test bacterium into different freshwater media obtained from various sources resulted in growth and rapid multiplication. Viability was maintained throughout the 148 day incubation period. Growth in the brackishwater medium was observed only until 50 days. No growth was observed in the seawater medium.

1. Groups of rainbow trout (Salmo gairdneri) (mean weight 14 g) were given diets containing 0.8, 1.3, 2, 3, 4 or 6 g tryptophan/kg diet for 12 weeks. 2. By analysis of the growth results, the dietary requirement of tryptophan was found to be 2.5 g/kg diet (equivalent to 50 mg/kg biomass per d). 3. Carbon dioxide expired by trout following intraperitoneal injection of [¹⁴COOH]tryptophan contained little radioactivity when dietary tryptophan level was low but, above 2.0 g/kg diet, it increased rapidly with increasing dietary tryptophan level. The break point in the dose-response curve did not, however, coincide with that from the growth results. 4. Changes in concentrations of free tryptophan in blood and liver and activity of hepatic tryptophan pyrrolase (EC 1.13.11.11) in response to changes in dietary tryptophan concentration did not provide reliable indicators for quantifying dietary requirement. Unlike the situation in mammals, blood tryptophan was not protein-bound to any appreciable extent. Tryptophan pyrrolase of trout has properties which suggest it has no apoenzyme form. 5. In fish given adequate levels of tryptophan injected intraperitoneally with a tracer dose of [¹⁴COOH]tryptophan, 60% of the dose was incorporated into body protein within 1 d. The turnover of the label in this protein is very slow. 6. Those trout given diets deficient in tryptophan suffered from severe scoliosis and lordosis as well as having increased liver and kidney levels of calcium, magnesium, sodium and potassium.

The hepatocytes of milkfish (C. chanos) fry and fingerlings offered a variety of diets differ considerably as was shown by means of transmission electron microscopy. For fry it was shown that a 7 day starvation period results in a heavily altered hepatocyte ultrastructure but that even in this stadium fast regeneration was possible. Chlorella turned out to be the worst diet, among the artificial diets, the trout diet provoked the best regeneration. In fingerlings a prolonged starvation period was necessary to affect hepatocytes. In some cases considerable indications of liver cell degeneration were found after feeding certain diets for 2-3 months. Even dried lumut and lab-lab did not create optimal hepatocyte ultrastructure. Feeding with cod liver oil did not result in deposition of lipid droplets in the hepatocytes of fingerlings, what is in contrast to milkfish fry hepatocytes.

The effect of the rotifer, Brachionus plicatilis, grown on unialgal cultures of Isochrysis galbana, Tetraselmis sp. and Chlorella sp. on the hepatocytes of milkfish fry was evaluated by electron microscopy. Rotifers grown on the three different species of phytoplankton brought about different ultrastructural features in milkfish fry hepatocytes. Best results were obtained from fry reared on Isochrysis-fed rotifers. The use of marine Chlorella-fed rotifers as feed for fry resulted in the poorest hepatocyte ultrastructure, indicating that this was nutritionally the least adequate cultured food. None of the three diets, however, produced an optimal hepatocyte ultrastructure similar to that obtained by feeding the fry with a mixture of artificial feed and newly hatched Artemia nauplii.