Tilapia Larvae Research Articles

Role of thyroid hormones in tilapia larvae (Oreochromis mossambicus): I. Effects of the hormones and an antithyroid drug on yolk absorption, growth and development

Treatment of one-day old yolksac larvae of tilapia (Oreochromis mossambicus) by immersion in 0.05 ppm T4 or 0.01 ppm T3 significantly accelerated the differentiation and growth of all the fins, particularly pectoral and tail fins. Both the treatments also significantly accelerated yolk absorption and transition to free-swimming activity in the larvae. The treatments also significantly accelerated the growth of the larvae, with T3 at 0.01 ppm having a greater effect than T4 at 0.05 ppm. The yolk conversion efficiency was found not to be significantly affected by the hormone treatments but the treated larvae exhibited an increased heart beat, suggesting metabolic stimulation by the hormones.On the other hand, yolk absorption and free-swimming activity were significantly delayed in tilapia larvae immersed in 25 ppm solution of an antithyroid drug, phenylthiocarbamide (PTC). PTC also retarded the growth of the larvae. T4 (0.05 and 0.10 ppm) or T3 (0.01 and 0.02 ppm) therapy removed the PTC-inhibition,albeit not completely, suggesting that thyroid hormones are involved in the larval growth and development of tilapia.

Serum biochemical parameters are greatly correlated to haematologic findings and may serve as indicators of the proliferative activity in chronic myelomonocytic leukaemia (CMML) : F. López, G.F. Sanz, T. Vallespi, M. Torrabadella, M.C. del Cañizo, M. Guinot, D. Irriguible, A. Juliá, J.F. San Miguel, M.A. Sanz. Department of Haematology, Hospital La Fe, Valencia; Hospital Vall d'Hebron, Barcelona; and Hospital Clínico,

The purpose of this study was to test polyculture of Nile tilapia and the native Mayan cichlid, as an alternative production method of tilapia. The experiment had a 2 × 4 factorial design: the first factor was the population of tilapia (mixed-sex and 95% males) and the second factor was the proportion of Nile tilapia: Mayan cichlid (3:1, 5:1, 7:1 and 1:0). Proportion of 1:0 was tilapia monoculture. At stocking, tilapias were 11 weeks old and weighed 24.0 g and Mayan cichlids weighed 5.0 g. Recirculating water systems were used, with 24 fiberglass tanks 1 m3 with permanent water flow (7 L min− 1) and aeration. Each treatment had 3 replicates distributed randomly, and 24 fish were introduced in each tank (30 fish m− 3). The experiment lasted 21 weeks, until tilapia reached marketable size. Fish were fed with extruded formulated diets for tilapia (40% and 30% crude protein). Daily feeding rate was restricted to between 4% and 1.8% of the fish biomass. Temperature, DO and pH (28.0 ± 1.1 °C, 5.2 ± 1.2 mg L− 1 and 7.9 ± 0.2) were within the appropriate ranges for growth, and TAN, nitrites and total alkalinity (0.29 ± 0.22 mg L− 1, 0.04 ± 0.03 mg L− 1 and 238 ± 27 mg L− 1) were within safe ranges. Average survival was high (99%) and no differences were found between populations and among proportions. Nile tilapia Stirling strain showed early (45 g after 3 experimental weeks) sexual maturation and growth dimorphism. Significantly better total yield, FCR and final tilapia body weight were obtained in the 95% male population (9.26 kg m− 3, 1.39 and 383 g) than in the mixed-sex population (7.70 kg m− 3, 1.52 and 315 g). The presence of the Mayan cichlid did not affect tilapia performance. The final weight of Mayan cichlid was significantly higher in the mixed-sex tilapia population (45.9 g) than in the 95% male population (34.4 g). Mayan cichlid growth was inversely proportional to its density, with final weights of 45.5 g, 39.0 g and 34.3 g (7:1 > 5:1 > 3:1). The differences in Mayan cichlid growth are associated with intraspecific competition for available tilapia larvae. Mouth brooding tilapia females with eggs or larvae were observed in both tilapia populations and in all proportions. When fish were weighed some tilapia females released their larvae in the tanks, and both Mayan cichlid and tilapia males were observed preying on them.

Immunocytochemical identification of prolactin cells in the pituitary gland of tilapia larvae (Oreochromis mossambicus: Teleostei)

Using an antiserum to highly purified chum salmon prolactin, prolactin cells were identified in the putative rostral pars distalis of newly hatched tilapia larvae (Oreochromis mossambicus) by the immunogold method for the electron microscope. In the putative rostral pars distalis, some cells had another kind of secretory granule which was much less numerous, much smaller in size, and without immunoreactivity to salmon prolactin antiserum. Controls incubated with salmon prolactin-preabsorbed antiserum or normal serum showed no immunoreactive cells, confirming the specificity of the antiserum. The possible role of prolactin in the osmoregulation of tilapia larvae is discussed.

Putative role of adenohypophysis in the osmoregulation of tilapia larvae ( Oreochromis mossambicus; Teleostei): An ultrastructure study

Ultrastructure of the secretory cells in the adenohypophysis of tilapia ( Oreochromis mossambicus) larvae hatched in fresh water or sea water was compared. Adenohypophysis of newly hatched larvae of tilapia is a short columnar body attached to the ventral floor of the diencephalon. The adenohypophysis is at its early differentiation stage, i.e., various types of secretory cells are still undistinguishable. Only part of the cells in the putative rostral pars distalis look like typical endocrine cells, containing well-developed rough endoplasmic reticulum, Golgi apparatus, and numerous secretory granules. The average size of secretory granules in freshwater-hatched larvae is significantly larger than those in seawater-hatched larvae (12,936 ± 2854 nm 2, N = 11 vs 3375 ± 810 nm 2, N = 10), suggesting some role of adenohypophysis in the osmoregulation of the early developmental stage of teleosts.

Developmental dynamic in synaptic ribbons of retinal receptor cells (Tilapia, Xenopus)

In the cichlid teleost Tilapia leucosticta, the origin and linear development of synaptic ribbons in retinal receptor cells have been studied. First ribbons are invariably found close to their future synaptic sites between two dendritic invaginations. They are then clearly shorter than at later stages and appear bifurcate, or of bulb or drop shape. From these precursors typical ribbons rapidly develop, and these vary considerably in length. From a shift in length distribution, a main growth phase can be ddetected which takes place at the time when the retina first becomes functional. Similar observations were made in Xenopus. Placing Tilapia larvae in conditions of 24 h continuous light had no effect on ribbon growth, while 24 h of continuous darkness resulted in a prevalence of shorter ribbons. Thus the growth of synaptic ribbons in the course of retinal development appears to be subject to modification by environmental light conditions.

Investigations of the toxic effects of Bayer 73 (Bayluscid WP) on eggs and yolk-sac larvae of Tilapia leucosticta (Cichlidae).

The toxic effect of Bayer 73 on larvae ofTilapia leucosticta shows a sharp increase from the day of hatching to the end of the yolk-sac stage. Different degrees of deformity appear in the course of development.