Victor Devlaming

On the use of the gonosomatic index

Abstract 1. 1. Using data collected from two teleostean fish species the assumptions of the gonosomatic index (GSI) were examined primarily by regression analysis and analysis of covariance. 2. 2. Standard length of the fish and standard length cubed can have a higher degree of correlation with ovarian weight as compared to body weight. Therefore, an ovarian weight-body weight ratio is not always the best way of expressing a gonadal index. 3. 3. When ovarian weight is regressed on some expression of body size, intercepts of the regression equations have a non-zero intercept. Furthermore, intercepts of regression equations from fish in different ovarian development stages are not always statistically homogenous. These findings are inconsistent with the GSI assumption of a zero intercept. 4. 4. The relationship of ovarian weight to body size changes with the stage of oocyte development. Thus, the GSI is an inaccurate means of comparing gonadal activity between experimental groups. 5. 5. When independent and dependent variables are subjected to log transformations, the relationship of ovarian weight to body size is less likely to vary with stage of oocyte development. Thus, expressing ovarian weight as an exponential function of some measure of body size may provide a more appropriate gonadal index. 6. 6. The analyses presented disclose that the GSI is not an accurate indicator of gonadal activity.

Dynamics of oocyte development and related changes in serum estradiol-17β, yolk precursor, and lipid levels in the teleostean fish, Leptocottus armatus

Abstract 1. 1. The dynamics of ovarian development in Leptocottus armatus were studied. Seasonal changes of serum estradiol-17β, serum vitellogenin, serum total lipids and visceral lipid reserves were monitored. 2. 2. Two to four distinct size classes (clutches) of oocytes occurred in the ovary preceding and during the spawning period. One of these clutches contained oocytes in the vitellogenic or post-vitellogenic phase, a second clutch contained oocytes “arrested” in the cortical alveoli stage and a third clutch contained non-yolky oocytes. Only one clutch was oviposited in the annual spawning season. 3. 3. Estradiol levels increased coincident with the appearance of yolky oocytes in the ovary. Serum estrogen levels were highest during the period of ovulation and spawning. During the spawning period estradiol titers were not significantly correlated with oocyte size or gonosomatic index. 4. 4. Serum vitellogenin levels increased in parallel with oocyte size and estradiol titers. Vitellogenin levels were relatively low during the early portion of the spawning period, becoming elevated again towards the end of the spawning period. In concordance with ovarian regression, serum vitellogenin levels declined and remained low during the ovarian quiescence phase. Neither GSI nor serum estradiol titers correlated significantly with vitellogenin levels. 5. 5. With initiation of ovarian recrudescence visceral lipid reserves began to decline and continued to decline through the vitellogenic and spawning phases. Visceral lipid reserves were inversely correlated with ovarian GSI. Serum lipid levels were high during ovarian recrudescence, remaining elevated through the spawning period. During the phase of ovarian quiescence serum lipid levels were low and visceral lipid reserves were high. Visceral lipid reserves showed an inverse correlation to serum estradiol titers.

Aspects of embryo nutrition and excretion among viviparous embiotocid teleosts: Potential endocrine involvements

1. 1. Embryos of the viviparous embiotocid fishes develop free within the ovarian cavity from small eggs for approximately 6 months. The biochemical composition of ovarian fluid was determined and compared to serum constituents in three embiotocid species during the gestation phase. 2. 2. SDS-gel electrophoresis data showed that ovarian fluid collected from female Cymatogaster aggregata during late gestation was essentially devoid of serum peptides, but contained peptides absent from maternal serum. The ovarian fluid peptides are probably derived from the ovarian epithelial lining. 3. 3. Pregnant female ovarian fluid contained large quantities of urea, whereas the maternal serum was devoid of this metabolite. This suggests that embiotocid embryos, but not adults, produce urea as a nitrogenous waste: furthermore, ovarian membranes must be relatively impermeable to urea. 4. 4. Amino acids in the ovarian fluid of Cymatogaster basically correspond to those in maternal serum. but were, in most cases, at lower levels. Although absent from serum, phosphoethanolamine was present at high levels in the ovarian fluid of pregnant Cymatogaster, but not Hyslerocarpus Irciski, during late gestation. 5. 5. The principal amino compound, exclusive of urea, in the ovarian fluid of Hysterocarpus and Micrometrus minimus was taurine. Serum levels of glutamine, ethanolamine and taurine were elevated in pregnant embiotocids. 6. 6. Lipid levels were also elevated in maternal serum during late pregnancy. Precluding phospholipids, the concentration of lipids in ovarian fluids was considerably lower than in maternal serum. 7. 7. In Cymatngtisler and Hysterocarpus serum progesterone and estradiol levels were comparatively low during gestation, posing some doubt as to the significance of these steroids in maintenance of pregnancy. 8. 8. The possibility that embiotocids produce an estrogen-dependent, vitellogenin-like protein was examined. Studies with Cymatogaster and Hysterocarpus indicated that the embiotocids may be the only teleostean family yet known which do not produce a vitellogenin-like protein.

Pinealectomy and melatonin effects on daily variations of the hypothalamic serotonergic system in the goldfish

Abstract 1. 1. Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a 16L/8D, 20°C regime but were not found in fish kept on an 8L/16D, 20°C regime. 2. 2. Pinealectomy had a significant effect on hypothalamic serotonin content and serotonergic activity in fish exposed to the long, but not short, photoperiod. 3. 3. Melatonin administration to control animals (100 μg per day for 10 days) modified the day-night variations of hypothalamic serotonin content and serotonergic activity regardless of photoperiod. 4. 4. The effects of melatonin on hypothalamic serotonin content in pinealectomized animals were dependent upon the photoperiod regime, whereas effects on serotonergic activity were not. 5. 5. It is concluded that the goldfish pineal organ and melatonin may play a role in hypothalamic adjustments to changing photoperiods.

Effects of clomiphene citrate, a nonsteroidal antiestrogen, on brain monoaminergic mechanisms in female goldfish, Carassius auratus

The antiestrogen, clomiphene citrate ( Merrell -National Laboratories) was administered to female goldfish in order to test the hypothesis that this drug may act on brain monoaminergic mechanisms. Brain monoamine oxidase (MAO) activity and hypothalamic serotonin (5-HT) content were measured fluorometrically after i.p. administration of 0, 5 or 25 micrograms clomiphene citrate/g body wt. Brain MAO activity was significantly inhibited by the high dose of clomiphene citrate, whereas hypothalamic 5-HT content was significantly elevated by both low and high doses of the antiestrogen. These data support the idea that brain monoamines in teleost fish are influenced by estrogen feedback mechanisms which can be blocked by clomiphene citrate.