Various extenders, containing potassium chloride, sodium chloride, glucose, sodium citrate, Ringer's solution, cow serum and milkfish serum were used to preserve milkfish (Chanos chanos) sperm at near-zero temperatures (0-4°C) and in liquid nitrogen (?196°C). Milkfish serum was a superior extender in both cases. After 5 days, comparatively good motility (> 30%) and fertilizing capacity (6.7-18.9%) were observed in the near-zero liquid samples, while in other extenders, sperm ceased to show motility after 2 days. The fertilization success of 4-5 days cryopreserved sperm averaged 67.5% (n = 2) with milkfish serum, 60.5% (n = 2) with 400 mM glucose, 58.0% (n = 2) with 150 mM sodium chloride, 41.2% (n = 1) with Ringer's solution and 31.9% (n = 2) with cow serum.

Crude extracts from various regions of the digestive tract of pond grown milkfish were tested forttheir ability to catalyze the hydrolysis of various carbohydrates. The most active carbohydrases were those involved in the hydrolysis of agr-glucosidic bonds. Maltose, trehalose, dextrin, starch and glycogen were rapidly hydrolyzed in the presence of crude extracts from the intestines and the pyloric caeca. High amylase activity was observed in extracts from the intestines, pancreas, pyloric caeca and liver. The intestinal amylase had optimum activity at pH 6.2 and at a temperature of about 50°C. It was active at a chloride concentration of 10 to 40 ppt. The amylase activity in the intestines consistently peaked daily at about noon when the milkfish gut was full. In contrast, enzyme activity was significantly lower at 0030 hrs when the gut was empty. These results are consistent with earlier observations that the milkfish is a daytime feeder and suggest further that intestinal amylase secretion is in phase with the feeding activity of the milkfish. Although the fishes used in this study fed mostly on the naturally occurring algae in the ponds, no cellulase activity was detected in any region of the digestive tract. Less active carbohydrases that were detected include a beta-glucosidase and beta-galactosidase, both of which were of limited substrate specificity.

Shore-caught milkfish fry (late postlarvae) and artificially-bred, laboratory-reared larvae (0-to 20-day old) were preserved in 5% and 10% freshwater-and/or seawater-formalin solutions after measuring their initial weights and/or lengths. The changes in length and weight were observed at regular intervals. Shrinkage in freshwater-formalin (FWF) was less than in seawater-formalin (SWF). The difference in 5% and 10% concentrations of the same solution was not significant. Wild fry showed a final shrinkage of 5.13% of the initial length in 5% SWF and 5.0 7% in 10% SWF. Shrinkage in laboratory-reared larvae varied from 5.09-8.35% according to the age and/or developmental stage, for the same preservation period of 14 days. In estimating the natural length of milkfish larvae preserved in 5-10% SWF, a 5% shrinkage must be considered. The specimens must be kept in the preservative for at least a week before measurement since it takes at least a week for shrinkage to stabilize. Nothing definite could be said, as yet, for the weight changes in milkfish larvae.

The present paper deals with the morphological development of the external genitalia of Penaeus monodon which will serve as a basis for future researches on the reproductive biology of this species. The petasma length is taken as the median linear distance between the anterior and posterior margins of the organ, and the thelycum length the linear distance between the anterior edge of the boss-like antero-median plate and the posterior margin of the lateral plates. A description is given of the metamorphosis of male and female genitalia of P. monodon.

The development of the optomotor reaction (OMR) in milkfish (Chanos chanos), from the larval, through the metamorphic, to the juvenile stage was observed. The period from the appearance of the pelvic fins until the complete disappearance of the finfold was named "metamorphic stage". While the larvae showed strong rheotactic responses, their OMR was somewhat weak. It was clear that the OMR underwent a big change through the metamorphic stage, and became strong and almost perfect in the juveniles.

Feeding of milkfish (Chanos chanos) larvae and juveniles on Artemia nauplii in captivity was observed. The retinae of the larvae were observed histologically. Milkfish larvae could not take food in the dark. The juveniles could take food in the dark although less efficiently than in the lighted condition. Vision thus seems to be the most important sense for the milkfish larvae since feding depends very much on it. The larvae were found to have already well-developed regionally differentated retinae with all elements present. Vision, evidently, is developed foremost among the senses.

The study was conducted to study the effects of single injections of Human Chorionic Gonadotropin (HCG) (Ayerst Laboratories, Inc) and Durandron Forte 250, a long-acting androgen preparation (N.V. Organon Oss, Holland), on sperm motility, vitality and density and on the consistency of milt in newly caught, wild, mature milkfish (Chanos chanos). There is an advantage in using Durandron Forte 250 in inducing thinning of milt in mature milkfish during the natural breeding season to facilitate fertilization of eggs. Aside from its long-lasting effect which minimizes handling of fish, it is much cheaper than HCG.

This is the first report in the world on the characters of the first zoea of Calappa philargius under laboratory conditions. The zoea has a rostral, a dorsal and a pair of lateral spines on the carapace. The average length of larvae from tip of rostral to tip of dorsal spine is 1.26 mm, width, including both lateral spines, 0.74 mm and that of distance between outer margins of eyes, 0.47 mm. There are a pair of lateral hooks on the second and third abdominal segments. There are four natatory hairs on the first and second maxillipeds. Spinal arrangements on the endopodites of the first and second maxillipeds from proximal to distal segment are 2-1-0-2-5 (or 4) and 1-1-4 (or 3), respectively. The number of inner setae on the telson is six (3+3).

This paper describes a method of constructing 12 mm thick ferocement buoys used as a floatation system in the culture of green mussels (Mytilus smaragdinus).

A female milkfish, captured at sea, was injected with two hormonal injections of acetone-dried salmon pituitary powder and human chorionic gonadotropin, plus Vitamin B complex. It was stripped, and produced 128,000 ripe eggs with an average diameter of 1.15 mm. Fertilization rate was 38% following artificial fertilization with milt from an uninjected male. A total of 36,000 larvae hatched (74% of fertile eggs) after 26–32 h at 34 ‰ salinity and 27–32°C. The newly hatched larvae measured 3.4 mm in mean total length and possessed a large yolk sac. The mouth of the larvae opened about 54 h after hatching. The larvae were fed with fertilized oyster eggs, rotifers, copepods, brine shrimp, flour and prepared feed, together with Chlorella. A critical period was between the 4th and 6th days with mortality over 80%. The larvae started increasing in length by Day 8, and had the appearance of the wild fry by Day 11. On Day 13 a pigmentation pattern developed and the biggest larva measured 10.0 mm. By Day 18 the larvae measured 12.5 mm, and 14.5 mm by Day 21. A total of 2,859 fry was obtained; the highest larval survival rate obtained from different experimental groups was 46.8%.