Characterisation of glycoproteins in the secretory cells in the operculum of an Indian hill stream fish Garra lamta (Hamilton) (Cyprinidae, Cypriniformes)

Glycoproteins (GPs) elaborated by the secretory cells in the opercular epidermis (OE) and the epithelium lining the inner surface of the operculum (EISO), of an Indian hill stream fish Garra lamta have been analysed by means of a battery of histochemical methods. These included methods for the characterisation and simultaneous visualisation of GPs with oxidizable vicinal diols, O-acyl sugars, O-sulphate esters and sialic acid residues without O-acyl substitution or with O-acyl substitution at C7, C8 or C9. Results obtained in this study show that conventional periodic acid Schiff's and alcian blue based procedures are less sensitive and largely fail to identify different classes of GPs. In the OE the secretory cells involved in the synthesis of GPs are the epithelial cells, the mucous cells and the club cells. Based on the histochemical characterisation of GPs, the mucous cells are distinguished in to two types, Type A and Type B. The majority being of Type A. In the EISO, in contrast, the club cells are absent and most mucous cells belong to a third category, Type C. Type A and Type B mucous cells are few. GP classes synthesised by the secretory cells and released on the outer surface of the operculum, directly exposed to the environmental hazards show significant differences in their composition and concentration from those on, the relatively well protected, inner surface of the operculum. These are discussed in relation to the physiological significance of the GP classes with special reference to their role in lubrication, protection and inhibition of the invasion and proliferation of pathogenic micro-organisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in brain and pituitary GnRH levels during ovarian maturation in wild female Japanese flounder

To elucidate the role of gonadotropin-releasing hormone (GnRH) in gonadal maturation in wild female Japanese flounder Paralichthys olivaceus, we monitored changes in the levels of seabream GnRH (sbGnRH) in the olfactory bulb, telencephalon, hypothalamus, and pituitary during ovarian development together with changes in plasma levels of testosterone (T), estradiol-17β (E₂), and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP). Fish were caught offshore of the northern mainland of Japan in the Pacific Ocean at 3- to 4-week intervals between April and September by gill net. The netted fish were categorized into six groups based on ovarian stages: previtellogenic (April–early May), early yolk (April–late May), late yolk (late May–June), early spawning (June–August), late spawning (September), and termination (September) stages. The gonadosomatic index significantly increased from the previtellogenic to early spawning stages and decreased thereafter. In the olfactory bulb, no significant differences were observed in sbGnRH levels among the developmental stages. In contrast, sbGnRH levels in the telencephalon and hypothalamus were very high in the previtellogenic stage, lower in the early spawning stage, and relatively high in latter stages. sbGnRH levels in the pituitary were high in the previtellogenic stage and low in the early spawning stage. In addition, the relatively high levels of pituitary sbGnRH were found together with high plasma T, E₂, and DHP levels in fish in the late yolk stage. These results indicate that sbGnRH in the telencephalon, hypothalamus, and pituitary is involved in ovarian maturation and that sbGnRH may play an important role in the initiation of ovarian recrudescence in wild Japanese flounder.     

我国近海星康吉鳗群体的形态学、遗传学比较研究

结合形态学、遗传学的方法,分别对青岛近海(黄海)、舟山近海(东海)的星康吉鳗群体做了相关系统的研究。通过单因素方差分析、判别分析、主成分分析方法对两个星康吉鳗地理群体的9个可量性状进行形态学比较研究;基于线粒体DNA (mtDNA)序列进行遗传学分析研究。形态学研究结果显示,舟山海域的星康吉鳗肌肉中含有"I"形硬肌间骨,青岛海域星康吉鳗的肌肉中无硬肌间骨;单因素方差分析结果显示,两个群体的7个可量指标:肛长、头宽、吻长、口裂长、眼径长、背鳍前长和胸鳍长存在显著差异;在主成分分析中,基于前两个主成分绘制的散点图基本能够将两个星康吉鳗群体区分开来;判别分析结果显示,青岛、舟山两群体的判别准确率分别为100%和94.7%。3种多元统计分析结果均表明青岛、舟山两个星康吉鳗群体在外部形态上存在一定程度差异,但根据75%识别与划分规则,认为两组群体的形态学差异尚未达到亚种水平。遗传学研究表明,在所检测的mtDNA水平上两个星康吉鳗群体遗传多样性无明显差异,邻接系统发育树未呈现明显的谱系关系,遗传分化指数FST也显示两群体遗传差异小,遗传分化不显著,属同一种群。     

Multiple spawning and related variations in female reproductive parameters of amphidromous type ayu

Adult ayu Plecoglossus altivelis were sampled from the Nezugaseki River, Yamagata Prefecture to investigate the reproductive parameters and analyze their variations related to multiple spawning. Ovarian histology (mainly based on the occurrence of postovulatory follicles) indicated that female ayu can be divided into four groups, which are considered to correspond with unspawned, once spawned, twice spawned, and three (or more) times spawned individuals. Comprehensive analysis of the ovarian state with field surveys revealed that most of the female ayu achieve second spawning and that third spawning is very common in this river. Mean relative batch fecundity (RBF) for the second, third, and fourth spawning indicated 69, 42, and 22%, respectively, of the value for the first spawning, showing a decline with the number of spawning batches. Mean gonadosomatic index (GSI) values of non-ovulating fish showed a similar decline during the main spawning period (October). Condition factor (without gonads) during autumn also decreased with the number of batches spawned, suggesting that multiple spawning is achieved partly by transfer of body mass nutrients to the ovary. Size dependency in reproductive parameters such as occurrence of the multiple spawning, RBF values, and GSI values of the unspawned fish, was not evident except for GSI values in early September (generally during the early phases of ovarian development), when larger fish had larger GSI.     

怒江裂腹鱼鳃的显微和超微结构

通过光镜、扫描电镜及透射电镜技术,研究了怒江裂腹鱼(Schizothorax nukiangensis)鳃的组织结构和超微结构。结果表明,怒江裂腹鱼鳃基本结构与其他硬骨鱼相似,均由鳃耙、鳃弓、鳃丝以及鳃小片构成,且各部分具有不同的组织结构和细胞类型。扁平上皮细胞覆盖于整个鳃表面,其表面的纹路主要有3种类型,在鳃上不同的部位具有不同的结构和功能。线粒体密集细胞主要分布于鳃小片基部,仅有一种细胞类型,顶端膜内凹呈浅滩型,细胞内具有大量圆形的线粒体。怒江裂腹鱼鳃内扁平上皮细胞和线粒体密集细胞的形态结构与其在急流中游泳和摄食活动等生活习性相适应。本研究结果丰富了怒江裂腹鱼的基础生物学资料,并为阐明鱼类鳃的结构特征与其生活习性之间的关系提供参考。     

The relationship between plasma and ovarian levels of gonadal steroids in the repeat spawning marine fishesPagrus auratus (Sparidae) andChromis dispilus (Pomacentridae)

The relationship between plasma and ovarian levels of gonadal steroids was examined in two New Zealand fish species with multiple spawning cycles of differing length. Snapper (Pagrus auratus) have a daily cycle of oocyte development, ovulation and spawning, whereas demoiselles (Chromis dispilus) spawn over 2–3 days during a repeat spawning cycle of 7–9 days. Ovarian and plasma levels of the gonadal steroids 17β-estradiol (E₂), testosterone (T), 17-hydroxyprogesterone (17P) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in reproductively active fish captured from the wild. Ovarian levels of E₂, T and 17P changed in relation to spawning cycle and gonad stage in both snapper and demoiselles. E₂ and T levels were detectable at all times, but highest during vitellogenesis in both species. Cyclic changes of 17P occurred in both species, and levels appeared to depend on the rate of conversion of 17P to other hormones. No changes in ovarian levels of 17,20βP were detected in relation to stage of the spawning cycle in snapper; however, ovarian levels of 17,20βP were highest in demoiselles before spawning when fish undergoing final oocyte maturation predominated. Plasma levels of E₂ and T were strongly correlated with ovarian concentrations (r=0.850 and r=0.819 for E₂ and T respectively) in demoiselles but there was poor correlation between ovarian and plasma levels of 17P and 17,20βP (r=0.004 and 0.273 respectively), or between ovarian and plasma levels of E₂, T, 17P or 17,20βP of snapper (r=0.135, 0.277, 0.131 and 0.279). The poor correlation between plasma and ovarian levels of some steroid hormones suggests that plasma concentrations of steroids may not adequately reflect the reproductive status of the fish during short-term cyclic ovarian changes. It is suggested that this disparity is likely to be most marked in species with ovulatory periodicity of short duration.     

Fluctuations in gonadotropin and ovarian steroids during the annual cycle and spawning of the common carp

The main objective of the paper is to describe the annual changes in hormones associated with reproduction in the female carp under the conditions prevailing in the Israeli fish culture. Fish were sampled monthly throughout 1984; gonadosomatic index (GSI) was calculated and the diameter of ovarian follicles was measured. Gonadotropin (GTH) content in the pituitary and the circulating GTH, estradiol, testosterone and 17, 20-dihydroxy-4-pregnen-3-one (17, 20-P) were determined by specific radioimmunoassays. GTH, estradiol and testosterone showed a bimodal annual pattern. The late summer peak was associated with initial vitellogenesis while the peak in spring occurred just before spawning, which took place in April-May. A resting phase in ovarian activity was noted in June and July. The levels of 17, 20-P were very low compared with those occurring during spawning induction. The paper summarizes a previous study by our laboratory on the changes in circulating hormones, as related to oocyte stages, in female carp induced to spawn by a GTH-calibrated pituitary extract. This study associates the short but prominent peak in 17, 20-P with the presence of follicles with maturing oocytes in the ovary. A correlation was found between the percentage of oocytes with eccentric germinal vesicle initially present in ovarian biopsies of females carp and their spawning success after hypophysation. The paper describes simple means to ensure successful induction of spawning in carp by utilizing a calibrated pituitary extract and prior selection of females that would respond to the induction treatment.     

遗传选育对野生和养殖中华绒螯蟹蟹种形态学特征的影响

以野生和养殖蟹种及其选育后代作为研究对象,实验采用单因素方差分析、判别分析、主成分分析和聚类分析等方法对各组形态特征进行分析。结果显示,(1)野生和养殖群体原代(G0)雌雄个体分别有16和15个形态指标差异显著,而选育2代后36个形态学指标均无显著差异;(2)判别分析中野生和养殖G0的判别准确率高达93%~100%,而2群体G1和G2个体判别准确率仅为56.67%~76.67%,且G2判别率低于G1;(3)主成分散点图显示野生群体G0与G1、G2个体分别可以形成较集中的区域,而主成分分析难以区分养殖群体G0、G1和G2个体;(4)聚类分析将6种群蟹种分为2支,其中养殖群体G0、G1和G2与野生群体G1和G2聚为一支,而野生G0单独聚为一支。研究表明,长江野生和池塘养殖蟹种的形态学差异较大,但在选育过程中逐渐消失,最终与养殖群体趋于一致,因此形态学特征不能作为中华绒螯蟹良种选育的可靠指标。     

Annual reproductive cycle of the greasyback shrimp Metapenaeus ensis in Ise Bay,Japan

The greasyback shrimp Metapenaeus ensis is widely distributed along the coast of India and the West Pacific where it is an important fisheries species. We have examined seasonal changes in ovarian development, spermatogenesis, and mating of Me. ensis in histological studies and by external observations on specimens collected in Ise Bay, its northernmost habitat. Ovaries were found to be previtellogenic from February to May, with the first signs of development being the accumulation of yolk in oocytes in late May. Ovarian shadow ratios were high during the period late July to mid-September. The formation of cortical rods in the peripheries of oocytes and germinal vesicle breakdown were observed in ovaries from late June to September. Male shrimps had sperm in the testes during the period early June to early October, and female shrimps had spermatophores in spermatheca after early July. In late July, some post-spawn female shrimps had exogenous vitellogenic oocytes in their ovaries, indicating that ovarian development had been repeated in preparation for the next spawning. Ovarian shadow ratios, which were positively correlated with gonadosomatic indices and ovarian development, seem to be a useful marker to determine ovarian development. Our results indicate that mating in Me. ensis started in early July and that the spawning season ranged from July to September with more than two cycles of spawning in Ise Bay.

     

Ovarian re‐maturation following the first spawning in the Chinese mitten crab,Eriocheir sinensis (H. Milne‐Edwards)

The present study investigated the external and histological changes in the ovary and measured the gonadosomatic index (GSI) and hepatosomatic index (HSI) during the re‐maturation of the Chinese mitten crab Eriocheir sinensis. The results show that the ovarian re‐maturation cycle of this crab species can be divided into four stages, i.e. Stage I: the ovary had an X shape and appeared milky white or with a mottled buff colour, and the dominant gametocyte at the stage were oogonia (OG, 28.3%) and previtellogenic oocytes (PR, 31.6%); Stage II: the ovary appeared light yellow or tan in colour, dominated by endogenous vitellogeic oocytes (EN, 69.3%). The yolk globules of unreleased mature oocytes (MO) from the previous spawn were absorbed, leaving many vacuoles in the retrogressing MO; Stage III: the ovary appeared crimson red or deep purple, and although the main type of gametocyte was exogenous vitellogenic oocytes (EX), near‐mature oocytes (NO) could also be found in the late phase of the ovarian development stage; Stage IV: the ovary was ripe and filled with MO that contained large yolk globules. During the period of the second ovarian maturation cycle, the GSI increased significantly from the time just after the first spawning (P<0.01). However, although HSI appeared to decrease within days after spawning (DAS), no significant correlation was found between GSI and HSI or between HSI and DAS (P>0.05). Furthermore, the final GSI and the volume of MO of E. sinensis during the second maturation cycle were drastically lower than those of the first maturation cycle.     

黄芪多糖和当归多糖对维氏气单胞菌诱导鲫细胞凋亡的影响

为研究黄芪多糖(APS)和当归多糖(ASP)对维氏气单胞菌诱导鲫细胞凋亡的影响,实验设阴性对照组、阳性对照组,黄芪多糖组和当归多糖组,通过对鲫用维氏气单胞菌攻毒处理,用流式细胞仪测定血细胞的凋亡比例和细胞周期变化,并用荧光显微镜和透射电镜观察凋亡细胞的形态。结果显示,维氏气单胞菌攻毒后阳性对照组鲫血细胞的细胞凋亡率均极显著高于多糖组和阴性对照组;多糖组能显著降低鲫的细胞凋亡率且黄芪多糖组效果更显著;攻毒后鲫肝细胞和肾脏淋巴细胞出现染色质凝集、细胞核固缩边集和细胞空泡化及凋亡小体;同阴性对照组相比;维氏气单胞菌攻毒可以引起鲫血细胞周期中S/G2+M期细胞比例极显著下降,sub-G1极显著升高,抑制细胞分裂诱发凋亡;多糖组则G0/G1期细胞极显著降低,S/G2+M期细胞极显著升高,sub-G1极显著降低,促进细胞分裂抑制凋亡。黄芪多糖和当归多糖添加量在1%时能抑制维氏气单胞菌攻毒引起的细胞凋亡。     

Reproduction phase-related variations in the GnRH immunoreactive fibers in the pineal of the Indian major carp Cirrhinus mrigala (Ham.)

We studied GnRH immunoreactivity in the pineal gland of the Indian major carp Cirrhinus mrigala during different phases of reproductive cycle. In the resting phase (December–January), GnRH immunoreactive (-ir) fibers were organized as paired fascicles above the posterior commissure that ascend in the stalk and distribute widely in the pineal gland. The GnRH-ir fiber density significantly declined (P<0.001) during the preparatory phase (February–April) and the fibers disappeared thereafter. While no GnRH fibers were seen during the prespawning (May–June) and spawning (July–August), isolated GnRH-ir fibers reappeared in the postspawning phase. Since no GnRH cell bodies were detected in the pineal, these GnRH-ir fibers seem to be of central origin. The results reveal a distinct reciprocal relationship between the GnRH immunoreactivity in the pineal and the status of the ovarian maturity; the fibers appeared in the pineal only during the period of ovarian quiescence. While the functional significance of these cyclic changes in GnRH is yet to be determined, we suggest that the decapeptide may serve as a transmitter of central origin that modulates the activity of the pineal gland.     

Effect of dietary soybean lecithin on reproductive performance of Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) Broodstock

The effect of increasing levels of dietary phospholipids (PL) on the ovarian development and reproductive performance of Chinese mitten crab Eriocheir sinensis were investigated using four semipurified formulated diets supplemented with 0%, 1.2%, 2.4%, and 3.6% PL. Four groups of 40 females, with an average individual body weight of 95–120 g, were fed the experimental diets for a period of 7 months. Male crabs were introduced into the female rearing system in March, and mating, spawning, and egg hatching occurred in the following month. After 10 weeks of feeding, females fed the diet with 2.4% PL had a significantly higher gonadosomatic index (GSI) than females fed the diet with 0% PL, whereas females fed the diet with 1.2% PL had a significantly higher hepatic moisture content and lower hepatic lipid content than the other groups (P < 0.05). After mating, the spawning rate was higher among females fed diets with 3.6% and 2.4% PL (95% and 92%, respectively) compared with females fed diets with 0% and 1.2% PL (both 81%). The results showed that egg production (total number of eggs/female) and fecundity increased with increasing dietary PL level, with females fed diets with 0% and 1.2% PL supplementation having significantly lower values than females fed the diet with 3.6% PL (P < 0.05). In conclusion, our results suggest that dietary PL supplementation has a positive effect on ovarian development and reproductive performance of E. sinensis broodstock. Further study should aim to investigate the optimal PL level in the broodstock diet of E. sinensis in respect to offspring quality.     

Spawning frequency of the Tsushima Current subpopulation of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> off Kyushu,Japan

Female Japanese chub mackerel Scomber japonicus of the Tsushima Current subpopulation were collected during the spawning season from March to May 2001. A total of 137 adult females were caught between midnight and daybreak. A considerable number of fish displayed new postovulatory follicles (POF), whereas there was no evidence of germinal vesicle breakdown or hydrated oocytes in any of the fish collected. This suggests a daily spawning synchronicity toward midnight. To estimate the spawning frequency (S), the female reproductive state was classified into four criteria based on the degenerative stage of the POFs and the developmental stage of the oocytes. To stage the POFs according to age and determine the stage duration, ovaries from S. japonicus were induced to spawn in the laboratory and were sampled 0–72 h after ovulation at appropriate intervals. The average S, which is evaluated from four different indices, was 16.9%, corresponding to the average female chub mackerel spawned every 5.9 days (8.5 times) during the 50 days.     

Stereological Analysis of Blood Space and Tissue Types in the Pseudobranch of the Rainbow Trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

The teleost pseudobranch, a reduced mandibular gill arch, morphologically closely resembles a gill hemibranch. It consists of several filaments bearing numerous lamellae. The vascular system of the pseudobranch also matches that of a gill, with afferent and efferent filamental arteries and the lamellar blood space. Despite the pseudobranch’s gill-like appearance, however, a gas exchange function is excluded in many teleosts by overlying opercular epithelium, effectively eliminating diffusional exchange with the external medium. The physiological function of the pseudobranch is still unknown, though its conspicuously close association with the ocular choroid rete mirabile, a structure supporting elevated oxygen partial pressures in the eye, suggests a role related to the process of oxygen secretion into the eyes of teleosts. In this paper we present new stereological data on the pseudobranch of rainbow trout (average weight: 478 ± 114 g, x ± SD, n = 12). The total Cavalieri volume of the pseudobranch was 46.4 μl (97 μl kg⁻¹), consisting of lamellae 49%, connective tissue 43.8%, large blood vessels 4.5%, filamental cartilage 2.3%, and central venous sinus 1.3%. Lamellae were comprised of pillar and pseudobranchial cells 81%, blood space 12.3%, and lacunar tissue 6.4%. The inner surface of the blood space in the lamellae was 12.2 cm² (25.5 cm² kg⁻¹), and its volume was 2.81 μl (5.88 μl kg⁻¹). The results demonstrate the pseudobranch’s potential for physiological functions requiring a high surface area or surface-to-volume ratio, i.e. ion transfer, gas exchange and other regulatory processes. More detailed analysis of the function of the pseudobranch, however, has to remain subject of future morphological and physiological studies.     

Endocrine and gonadal changes during the annual reproductive cycle of the freshwater teleost,Stizostedion vitreum

The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E₂), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early- to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E₂ levels in females increased rapidly from low values in October (< 0.1 ng ml⁻¹) to peak levels of 3.7 ng ml⁻¹ in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E₂ levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml⁻¹ in November, and peaking again at 3.3 ng ml⁻¹ just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml⁻¹, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells) with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn) to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml⁻¹ by November, remained elevated throughout the winter, and peaked at 2.8 ng ml⁻¹ I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml⁻¹, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml⁻¹. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting fish to relatively simple environmental and hormonal treatments.     

Histological examination of final oocyte maturation and atresia in wild and domesticated Penaeus monodon (Fabricius) broodstock

Oocyte maturation and gonadosomatic index (GSI) of eyestalk ablated Penaeus monodon females collected from the wild and from two first‐generation domesticated lines were assessed. Frequency and diameter of the different oocytes, and the intensity of oocyte atresia, were compared among groups through histological assessments of the sections of the middle ovarian lobe. Digitized images from ovary sections were used to record the frequency and diameter of different oocyte types. Spawning performance of the three groups were expressed in terms of the percentage of females that spawned at least once (productive females), time from eyestalk ablation to first spawning (latency period) and the number of spawnings per female stocked. Final ovarian maturation was attained in all groups, as indicated by the presence of mature oocytes with cortical rods (cortical oocytes), dark‐green ovarian colour and high GSI values (5.83–6.86%). However, domesticated groups presented significant larger immature oocyte types (previtellogenic and yolky oocytes) and smaller cortical oocytes compared with wild females, indicating a reduced vitellogenic activity during final oocyte maturation. Additionally, the frequency of atresia was comparatively higher for both domesticated groups, which could be related to their inferior spawning performance. The implications of these results on the reproductive potential and development of domesticated P. monodon are discussed.     

Reproductive biology of the commercial sea cucumber <Emphasis Type="Italic">Holothuria spinifera</Emphasis> (Echinodermata: Holothuroidea) from Tuticorin,Tamil Nadu,India

The annual reproductive cycle of the commercial sea cucumber Holothuria spinifera was studied in Tuticorin, Tamil Nadu, India, from September 2000 to October 2001, by macroscopic and microscopic examination of gonad tubule, gonad index and histology of gametogenic stages, to determine the spawning pattern. The gonad consists of long tubules with uniform development. It does not confirm the progressive tubule recruitment model described for other holothurians. The maximum percentage of mature animals, gonad and fecundity indices, tubule length and diameter, with the observations on gonad histology, ascertained that H. spinifera had the peak gametogenic activity during September and October 2001 followed by a prolonged spawning period from November 2000–March 2001.     

Influence of the gametogenic cycle on the biochemical composition of the ovary of the great scallop

The oogenic cycle and biochemical composition of the ovary of raft-cultured great scallop (Pecten maximus) were studied during the period April 1990–July 1991. The ovary condition index (FGI) and stereological studies showed the existence of two principal spawning periods, winter and late spring-early summer. No sexual resting period was found. Oocyte lysis was high throughout the year. Ovarian lipid levels displayed a clear seasonal pattern linked to the gametogenic cycle. Total lipid (TL, 16–21% dry weight), acylglycerol (AG, 20–65% TL) and free sterol (FS, 2.8–6.4% TL) levels were, generally, higher in the ripe ovary and a decrease coincided with spawning. Protein (59–63% dry weight), glycogen (<3% dry weight) and phospholipid (PL, 26–35% TL) levels showed no clear seasonal trend. The TL and AG were a good index of ovarian sexual maturity. The TL % of dry weight) correlated well with the female gonad condition index (r _s = 0.779, p < 0.001), and AG (% f TL) correlated well with the mean oocyte diameter (r _s = 0.630, p < 0.01) and the female gonad condition index (r _s = 0.443, p < 0.05).     

Characterization of gonadotropic cells during continuous and seasonal spermatogenesis of two freshwater fish species: a histochemical and immunohistochemical study

This work describes gonadotropic (GtH) cells and their morphological and immunohistochemical changes during the spermatogenic cycle of Serrasalmus maculatus (continuous spermatogenesis) and Pimelodus maculatus (seasonal spermatogenesis). GtH cells, widely distributed in the proximal pars distalis of the adenohypophysis, were characterized as round-shaped cells with eccentric nucleus, and cytoplasm with basophilic secretory granules and a variable number of vacuoles for both species. Immunohistochemistry against β-follicle-stimulating hormone (Fsh) and β-luteinizing hormone (Lh) in adjacent sections showed two separated GtH-producing cell populations, and a third population where both GtHs are expressed in the same cell for both species. In the seasonal spermatogenesis of P. maculatus, GtH cells seemed to be more abundant during developing and spawning capable phases. In contrast, no cyclic changes were detected in the continuous spermatogenesis of S. maculatus, except for the strong immunoreaction for Fsh and Lh in males with intense spermiogenesis. We conclude that changes reported here might reflect the type of spermatogenic cycle (seasonal or continuous) which are under different regulatory mechanisms (environmental and internal cues) controlling the reproduction in these species.