Induced spawning of grey mullet Mugil cephalus L. with fractionated salmon pituitary extract

The efficacy of fractionated salmon pituitary gonadotropin as a spawning agent in Mugil cephalus L. was tested. Natural spawning was induced in all females with a total dose of 11.9–20.9 μg/g body wt. Spawning dose varied inversely with initial mean egg diameters of recipient females. A 'critical' mean egg diameter of 650–700 μ was observed to precede the hormone dose that induced spawning. A 'priming' effect was observed following the initial injection and is discussed. The 'latency period' was determined to be 10–15 h; fecundity was estimated at 648 eggs/g body wt. Courtship, spawning and fertilization occurred naturally with uninjected males.     

Gonadal hydration response and major electrolyte levels in serum and seminal fluid of Puntius gonionotus (Teleostei) injected with the fractionated fish pituitary extract

Fractions of the pituitary extracts which were successfully used for induced spawning of certain carps have been tested in the present investigation to assess the gonadal hydration response in Lampam jawa Puntius gonionotus . The levels of major ions in the serum and seminal fluid were determined to see if there is any obvious change following the treatment. The gonadal hydration response was induced only by the injection of the second fraction, which fraction was thought to contain the gonadotropin or a gonadotropin releasing factor. A possible role of gonadotropin in osmoregulation has been indicated.     

Sex steroid levels,oocyte maturation and spawning performance in Waigieu seaperch (Psammoperca waigiensis) exposed to thyroxin,human chorionic gonadotropin,luteinizing hormone releasing hormone and carp pituitary extract

In the present study, we have investigated the sex steroid hormone levels, oocyte maturation and spawning performance in Waigieu seaperch (Psammoperca waigiensis) exposed to different doses (0, (control), 0.05, 0.25 and 0.5 mg/kg fish) of thyroxin (T₄) both through diet (continuously) and injection (single injection). In addition, we also studied plasma steroid hormone levels and spawning performances in female fish injected with a single dose of D-Ala⁶, Pro⁹-Net-mGnRH (LHRHa: 50 µg/kg), human chronic gonadotropin (HCG: 1,500 IU/kg) and carp pituitary extract (CPE: 10 mg/kg). In all experiments, samples were collected at 0, 6, 12, 24 and 48 h after exposure. T4 exposure via dietary route produced differential and enhanced effects, compared with when the compound was injected to the broodstock. A significant association between exposure to dietary T4, elevated plasma steroid hormone levels, maturation-, spawning-, fertilization- and hatching rate, egg diameter, embryogenesis and larval growth were observed. Interestingly, we observed that broodstock groups fed with T4 doses spawned 20 days earlier than the control group. Thus, we propose that these differences may be attributed to higher systemic availability of T4 due to dietary exposure that is easily transferable to eggs and embryos, as opposed to injection that require absorption to increase bioavailability. Furthermore, our results show that LHRHa, CPE and HCG produced significant increase in spawning rate, but significantly reduced fertilization- and hatching rates. Waigieu seaperch is a new candidate for marine aquaculture in Vietnam and relatively little is known about the reproductive biology and endocrinology of this species. Therefore, the present study forms an integral basis for understanding the reproductive endocrinology of a tropical marine finfish with increasing aquaculture prospects and may also contribute in the development of sustainable aquaculture of this species in a developing country such as Vietnam.     

Dry-season spawning in a cyprinid fish of southern India

Synopsis A population of the S. Indian cyprinid fishBarbus melanampyx was sampled monthly through 24 months. Seasonal cycles of the gonado-somatic index (GSI), ovarian stages, male breeding tubercles, spawning behaviour and population structure were assessed. These fish breed strictly seasonally during the main dry period: December/January through April. Comparison with other Barbus species of the same general region led to the conclusion that the patterns of reproductive investment ofB. melanampyx are similar to those of perennial species, and different from those of wet-season spawners. The reasons for this rather unexpected result were found in the more constant conditions prevailing during a dry season as compared to the monsoon. It was argued thatB. melanampyx and the species spawning perennially are in effect small-brood spawners, rather than partial spawners.     

Follicular dynamics in mares treated with an equine pituitary extract

The follicular dynamics of 112 mares treated with an equine pituitary extract were studied. Follicles >10 mm in diameter at day 15 post-ovulation appeared to represent the follicles which were induced with pituitary extract to grow and ovulate. This was shown by the greater number of >10 mm follicles in mares which subsequently had higher ovulation rates and by the subsequent decrease in number of small follicles (<20 mm) which corresponded with the increase in number of large follicles (>/=20 mm). The difference in diameter (mm) between the largest and second largest follicle on day 15 post-ovulation was greater (P<0.05) for extract-treated mares which subsequently had single ovulations than for extract-treated mares which subsequently had multiple ovulations (7.7 +/-1.5 vs 2.8 +/-0.6). The observed ratio of bilateral to unilateral multiple ovulations was not different (P>0.1) from the expected ratio which was calculated on the assumption that side of ovulation occurred independently (59:19 vs 62:16, observed vs expected).     

Saline acclimation of striped mojarra <Emphasis Type=Italic>Eugerres plumieri</Emphasis> (Cuvier 1830) and optimal dosage of carp pituitary extract (CPE) to induce spawning

The main objective of the current study was to determine an optimal dosage of commercial carp pituitary extract (CPE) of the conventional heteroplastic hypophysation technique to induce spawning in the wild caught striped mojarra broodstock Eugerres plumieri under laboratory conditions. We also describe trials testing saline acclimation regimes (changes from 10‰ to 30‰) prior to hormonal induction. For saline acclimation, three treatments were performed: first and second treatments began 1-day after conditioning of broodstock fish with a total duration of the saline changes lasting 1-day and 2-days, respectively. The third treatment began 30-days after conditioning with a 7-day saline regime. After reaching 30‰, all fish from the first and second treatments died after the fourth and ninth days, respectively; while the fishes in the third treatment survived more than two years. These fish remain on public exhibit in the “Mundo Marino” Aquarium, Santa Marta, Colombia. Four treatments of hormonal induction were tested on females using a total concentration of 5-mg of CPE per kg of body weight: first, second and third treatments were applied in two hormonal doses that corresponded to 10%–90%, 30%–70% and 40%–60%, respectively, with time intervals between doses of 14-h for the first and second treatment and of 12-h for the third treatment. The fourth treatment was applied in four hormonal doses that it corresponded to 20%–20%–30%–30% with 12-h time intervals between doses. Only the fishes of the fourth treatment resisted the induction, continued to live and reached spawning artificially. Water temperature remained at 28 ± 1°C and at 30‰ salinity during the study. The “dry” method of fertilization was used. The fertilized eggs were incubated at 30‰ and 35‰ salinities. These eggs reached the Morula early stage, but were later attacked by protozoan. These results suggest that fast changes of saline and limited hormonal dosages do not offer effective results in Eugerres plumieri. This work provided fundamental procedures for the culture and maintenance of live broodstock for striped mojarra in saltwater and/or coastal lagoon habitats and provides an effective and viable dosage of CPE for artificial spawning and commercial production in this species.     

Recent trends in research on induced spawning of fish in aquaculture

Since 1973, the treatment of sexually mature fish with brain hormones (i. e. neurohormones) in order to induce spawning activity has gradually been replacing the hypophysation, although the latter is still widely used. Some brain-hormone analogues have a hightened spawning-inducing effect. Since the discovery that dopamine inhibits gonadotropic hormone release, dopamine antagonists—pimozide or domperidone—are injected before or together with brain-hormone analogues. This double treatment, i. e. the suppression of dopamine inhibition followed by neurohormone stimulation, has become a current technique in aquaculture. The discovery of the pulsatile release of gonadotropic hormone from the pituitary hints at the possibility of using techniques in which exogenous hormones are injected in pulses. In the past few years, induction of spawning through the control of photoperiod and/or temperature has become increasingly important.     

Hypoxia inhibits fish spawning via LH-dependent final oocyte maturation

To evaluate the effects of long term hypoxia exposure on fish spawning, mature common carp, Cyprinus carpio carpio (Linnaeus) were subjected to either normoxia (7.4+/-0.2 mgO(2)mg O(2) L(-1)) or hypoxia (1.0+/-0.2 mgO(2)O(2) L(-1)) for more than two months. Gonadosomatic index (GSI), and concentrations of serum luteinizing hormone (LH), testosterone (T), and estroldiol (E2) were measured and gonad histology examined. Hypoxia inhibits fish spawning even though the gonad and oocytes developed under hypoxia exposure. LH levels of female carp were significantly decreased upon chronic exposure to hypoxia, and the final oocyte maturation in hypoxic females was significantly retarded. The results indicated that hypoxia may inhibit fish spawning through LH-dependent final oocyte maturation. In addition, no courtship was observed in hypoxic males. In conclusion, hypoxia impairs fish ovulation and, therefore, spawning and reproduction. LH levels were reduced leading to a failure of oocyte maturation. This, along with a lack of courtship by males may be the major mechanisms involved in hypoxic inhibition of reproduction in carp.     

Superovulation of cattle with equine pituitary extract and porcine ESH

Superovulation has been practiced in cattle for more than 50 years but the results have been highly variable. Scientists at six locations compared a horse pituitary extract (HAP) with a single batch of porcine FSH (pFSH) to determine the efficacy of these hormones to induce superovulation and to test for variability in the superovulatory response. Acetone-dried equine pituitaries were suspended in 40% ethanol containing 6% ammonium acetate, and the supernatant was mixed with 2.5 volumes of cold ethanol. The resulting precipitate was washed with cold ether and dried. Total doses of 18 mg of HAP and 36 mg of pFSH were injected intramuscularly (i.m.) over 4 days, two injections per day, and prostaglandin (PGF(2)alpha; 25 mg, i.m.) was administered on Day 3. Injections were begun on Days 6 to 13 of the estrous cycle. The overall ovulation rates (mean +/- SEM) for HAP and FSH were 8.8 +/- 0.7 and 15.1 +/- 1.0, respectively (n=231; P<0.01). Location interacted (P<0.01) with the type of gonadotropin for the ovulation rate. When expressed as a proportion of the number of corpora lutea, the total number of embryos recovered was greater (P=0.03) for pFSH than for HAP, but there was no difference in the number of Quality 1 and 2 embryos. The results show that HAP can induce a satisfactory superovulatory response, but there was no evidence of reduced variability of response to HAP compared with pFSH.     

Combined stain for fish pituitary.

A new combined stain is described for the study of cell types in the fish pituitary. Tissues are prepared by fixing in formol-sublimate and then embedded in paraffin wax. Tissue is sectioned at 5 micron and than stained sequentially with performic acid-alcian blue, periodic acid-Schiff, orange G, and acid fuchsin. As a result of this procedure acidophils stain as follows: lactotropes, red; corticotropes, light pink; melanotropes, bright pink; and somatotropes, orange. Cyanophils stain either magenta red (gonadotropes) or blue (thyrotropes). Neurosecretory material and the fibers of the pars nervosa which penetrate the pars intermedia stain light blue.     

Induced spawning of the striped mullet Mugil cephatus L.

The response of adult mullet to artificial hypophysalion, immediately before the onset of the spawning migration was studied. Both males and females received intraperitoneal injec-tions of mullet or salmon pituitary homogenates wth ACTH or Synahorin (APE+HCG) three times per week for 12 days. At the outset, conlrol females were in the tertiary yolkstage with a low mean GSI of 7.6, while males gave thick, non-dispersing milt. Two of fourfemales receiving one salmon pituitary plus 25 RU Synahorin per injection spawnedspontaneously in laboratory aquaria. Released eggs were buoyant, well formed and had a mean diameter of 570μm. Egg fertility could not be ascertained due to protracted contact with sea water. Spawned females extruded a meinbranous tissue 'plug' from the cloaca1 region which was subsequently retracted. The remaining experimental females were refractory to treatment and histological examination of the ovaries revealed a predominance of atretic oocytes. All males were refractory to treatment and milt hydration was not achieved. It is suggested that induction of early spawning is possible especially with higher doses of pituitary homogenates and Synahorin. [Oceanic lnstitute Contribution No, 62 Sea Grant Program, GH-76].     

Unexpected panmixia in a long-lived, deep-sea fish with well-defined spawning habitat and relatively low fecundity

The marine environment presents particular challenges for our understanding of the factors that determine gene flow and consequent population structure. For marine fish, various aspects of life history have been considered important in an environment with few physical barriers, but dominated by current patterns, often varying with depth. These factors include the abundance and longevity of larval stages, typically more susceptible to movement along current paths. It also includes adult body size, fecundity and longevity with ' r -selected' species typically thought capable of greater gene flow and consequent panmixia. Here we investigate the population genetics of the orange roughy ( Hoplostethus atlanticus ), a clearly ' K -selected' species with habitat dependence on sea mounts for spawning, relatively large body size, a brief larval stage and relatively low fecundity. We used 14 polymorphic microsatellite loci to test the hypothesis that these characteristics will result in philopatry and genetic structure in the Atlantic Ocean. We discuss possible evolutionary mechanisms that could explain the results, which show the opposite pattern, with effective panmixia across thousands of kilometres in the North Atlantic.     

Body morphology of crucian carp Carassius carassius in lakes with or without piscivorous fish

Crucian carp Carassius carassius was sampled during 1993 and 1994 in 21 lakes and ponds in east Norway In 10 of these lakes and ponds no piscivorous fish species was present, and in the remaining 11 lakes and ponds predators such as perch Perca fluvtalilis. pike Esox lucius, and trout Salmo trutta were common In general, crucian carp was larger in the lakes with predators than in those without predators The relative body depth (body height/body length) of crucian carp was significantly deeper in populations sympatric with predators (mean 0 358), compared to allopatric populations (mean 0 286) The variation in relative body depth was larger among the sympatric populations than among the allopatric populations The observed difference in relative body depth may be due to 1) predator induced changes m body morphology, 2) increased growth rates in lakes containing predator due to reduced intraspecific competition, and 3) size-selective predation