Gonadal Development Cycle Research Articles

Expression pattern of the vitellogenin gene in the zhikong scallop, Chlamys farreri, during ontogenesis

Vitellogenin (VTG), the precursor to yolk protein vitellins (Vn), has been widely studied in oviparous animals. However, information about VTG expression during ontogenesis is limited. In this study, we investigate the developmental expression pattern of the zhikong scallop gene, Chlamys farreri vitellogenin (Cf-vtg), using in situ hybridization and real-time RT-PCR techniques. The Cf-vtg mRNA was detected in unfertilized eggs, fertilized eggs, embryos and early-stage larvae, indicating a maternally supplied Cf-vtg. It was located restrictively in D-shaped larvae, and its concentration declined at the gastrula stage and approximated zero from umbo-larva to juveniles of 4–6 mm shell height. However, it was expressed distinctly again in the hepatopancreas of both males and females with shell heights from 7 to 12 mm and in the ovary during the first gonadal development cycle. This report provides experimental evidence of the expression pattern of vtg with the maternal supplication, the hepatopancreas and male expression in C. farreri.

Reproductive Strategies of the Eastern OysterCrassostrea virginica(Gmelin 1791) in Tropical Lagoons of the Mexican Gulf of Mexico

The oyster fishery is 1 of the most important coastal fisheries in Mexico. Management is based on a minimum legal size of 80 mm and several seasonal bans that vary along the coast of the Gulf of Mexico. We describe the gonad development cycle of Crassostrea virginica (Gmelin 1791) along the Mexican coast of the Gulf of Mexico for 5 lagoons for the years 2000 and 2004, between latitudes 2141'16.75'' N and 1823'51.08'' N. Significant differences in duration and intensity were observed among reproductive stages associated with different environmental conditions. Gametogenesis and mature stages correlated positively with temperature and total chlorophyll, respectively. Spawning correlated negatively with salinity in both years. Maturity correlated positively with total chlorophyll levels. The reproductive stages varied from seasonal, a few months, to continuous throughout the year. Recovery, expressed as the number of organisms in postspawning and resting stages, was fast for populations that presented constant gametogenesis and spawning, with less than 50% of the population in postspawning and resting stages. Environmental fluctuations in total chlorophyll are the regulating factors for gametogenic activity, rather than latitudinal temperature variations. This makes monitoring environmental conditions in the lagoons or gonad development a necessity to predict reproduction and recruitment for proper management of the oyster resource.

Reproductive strategy of Psectrogaster rhomboides Eigenmann & Eigenmann, 1889, a freshwater fish from Northeastern Brazil

Several environmental parameters related to the spawning season of the freshwater fish, Psectrogaster rhomboides were identified. The hypothesis predicts synchrony of the spawning season with the rainy period, presenting a seasonal reproductive strategy. This study investigated the total body length and body mass, sex ratio, body size at first sexual maturity, gonadosomatic index, condition factor, fecundity and reproductive period of P. rhomboides in the natural environment. Twelve monthly samplings (mean n = 20) were carried out from March 2009 to February 2010. Fish were captured using 4 cm diameter cast nets and environmental parameters such as rainfall, temperature, dissolved oxygen concentration, pH and electrical conductivity of the water were registered. The sampled population of P. rhomboides (n = 444) showed a sex ratio of 1 : 1. Females attained first sexual maturity at 15 cm total length and males at 15.3 cm total length. Spawning occurred from March to May, with high gonadosomatic index values during the rainy season. This species is a total spawner, with a mean fecundity of 6188 (±367) mature oocytes. P. rhomboides presents a seasonal reproductive strategy, providing a population increase and exploitation of the environmental resources during the rainy period. Rainfall (196.5 ± 4.9 mm) and the concentration of dissolved oxygen (7.82 ± 0.7018 mg L−1) were influential factors during the spawning season. Gonadosomatic index and the condition factor were negatively correlated during the gonadal development cycle of this species. The monthly gonadosomatic index values show that spawning begins when the rainy season is at its maximum and ends synchronously (females r = 0.9171; males r = 0.889) with the end of the rainy season.

Prior Experience with Photostimulation Enhances Photo-Induced Reproductive Response in Female House Finches

In vertebrates, reproductive output often increases with age. Unlike older birds, first-year photoperiodic birds lack experience with the reproductively stimulatory effects of long day lengths (photostimulation). We examined whether age-related differences in annual reproductive development could be partially attributed to previous experience with photostimulation in the photoperiodic house finch (Carpodacus mexicanus). By manipulating photoperiod, we generated 2 groups of first-year females: a photo-experienced group that underwent 1 photoperiodically induced cycle of gonadal development and regression and a photo-naïve group exposed to long days since hatch. We transferred both groups from long to short days and then photostimulated and exposed them to male birdsong prior to sacrifice. Following concurrent photostimulation, both groups exhibited similar plasma luteinizing hormone surges and hypothalamic vasoactive intestinal polypeptide immunoreactivity. In contrast, hypothalamic gonadotropin-releasing hormone immunoreactivity and circulating vitellogenin levels were higher in photo-experienced birds, and yolk deposition occurred in only 2 females, both of which were photo-experienced. Our results demonstrate that photo-experience enhances some aspects of early photo-induced reproductive development and raise the hypothesis that photo-experience may account for at least some age-related variation in reproductive output.

Lipid-based indicators of nutritional condition in juvenile sole Solea solea

Effects of the feeding level on juvenile Solea solea (Linnaeus, 1758) lipid-related indicators of nutritional condition were assessed in a 25-day trial experiment. Morphometric indices (K and HSI), liver lipid content and fatty acids (FA) clusters were good indicators of the feeding level, while individual FA showed highly dynamic variation patterns. Additionally, liver indices were more sensitive to feeding stress than were muscle measurements. HSI determination (and K) is fairly straightforward, with lower costs and simple procedures. Nevertheless, liver lipid content is also an important indicator of the feeding level and constitutes a direct measurement of food utilization and energy storage capacity. The individual variability and complex dynamics of FA with the feeding level are disadvantageous for use in FA analysis even for early-warning signals of feed limitation. Overall, S. solea nutritional condition can be suitably assessed by morphometric indices and lipid content, especially considering liver measurements (HSI and liver lipid content), provided that the fish development stage is accounted for (i.e. gonad development and reproductive cycle).

Life cycle of a small endemic goby Economidichthys pygmaeus (Family: Gobiidae) in Lake Pamvotis, northwestern Greece

Summary The life history tactics of the small endemic freshwater goby Economidichhtys pygmaeus were examined in a Mediterranean shallow lake located in the northwestern part of Greece (Lake Pamvotis). The purpose of the study was to define the population structure, growth, length at sexual maturity, sex ratio, annual cycle of gonad development, spawning characteristics and fecundity. Fish samples were collected using a hand net from October 2006 to September 2007. The fish grew rapidly in summer after hatching, matured after their first winter, and bred from February to June. The length frequency distribution indicated the appearance of two cohorts per year. Juveniles occurred in samples from April to September. Maturity length (ML50) of males and females were estimated to be 23.54 and 23.28 mm TL, respectively. Sexual dimorphism related to the male caudal fin was observed and males grew to greater lengths than females. The overall ratio of males to females was 1:1.35. Spawning was from February to June. Ripe females appeared to be multiple spawners, with oocytes at different stages of development. Size of oocytes changed during maturation and increased in diameter from about 0.125 to more than 0.9 mm. Absolute fecundity was positively related to TL and TW and varied between 59 and 309 eggs. After reproduction, the number of parental individuals decreased.

Temporal Dynamics of Reproduction of the Neotropical Fish,Crenicichla menezesi(Perciformes: Cichlidae)

The reproductive biology and the gonadal development cycle of the Neotropical cichlid fish, Crenicichla menezesi, is described. This species exhibits sexual dimorphism only during the spawning season. First sexual maturity of females is attained earlier than the males. Both macroscopic and histological investigations of ovaries and testes revealed four stages of gonadal maturation. Mean batch fecundity of females was 372 (±10,41) of mature oocytes. This species is a partial spawner, with an extended spawning period. Monthly values of GSI and the condition factor are negatively correlated during the gonadal development cycle of this species.

Features of reproduction of whitefishes

Based on features of reproduction, whitefishes (Coregonidae) differ from salmonids (Salmonidae) and graylings (Thymallidae). They differ from other salmonid fishes (Salmoniformes) in the following characteristics: they spawn, as a rule, during fall and winter; they do not construct spawning redds; their eggs are not protected; and substantial egg mortality is compensated by a high fecundity. The eggs of several whitefish species can develop in the conditions of “pagon” (within the ice). The main reasons for egg mortality at riverine spawning grounds are as follows: abnormalities during fertilization and development of the embryo, predation on the eggs, parasitic deceases, freezing of spawning grounds, and drift of the eggs from the spawning grounds. In addition (in the lakes), egg mortality can be caused by a deficit of oxygen, siltation, acidulation, and pollution of water. The survival of eggs of whitefishes in the Ural tributaries of the Lower Ob River in different years ranges from 0 to 93%. At a stable environment, the age of sexual maturation is connected with a certain body size of the fish. In the northern water bodies, the cycle of gonadal development can reach more than 1 year. Pollution of water by heavy metals, oil, and toxicants leads to serious anomalies of the reproductive system and to decreasing reproductive potential of the stocks.

Exposure to 17α-ethynylestradiol causes dose and temporally dependent changes in intersex, females and vitellogenin production in the Sydney rock oyster

Although mounting evidence suggests exposure to estrogenic contaminants increases vitellogenin production in molluscs, demonstration of dose-response relationships and knowledge of the temporal nature of the vitellogenin response with continual exposure is currently lacking for biomarker utility. To address this knowledge gap, adult Sydney rock oysters, Saccostrea glomerata, were exposed to a range of environmentally relevant concentrations of 17α-ethynylestradiol (EE2) (0, 6.25, 12.5, 25 or 50 ng/l) in seawater under laboratory conditions. Vitellogenin induction and gonadal development was assessed following 4, 21 and 49 days exposure to EE2. Vitellogenin was found to increase in a dose dependent manner with EE2 exposure for females (4 and 49 days) and males (4 and 21 days). Histological examination of gonads revealed a number of individuals exhibited intersex (ovotestis) in 50 ng/l EE2 (after 21 days) and in 6.25 and 12.5 ng/l EE2 (after 49 days). Furthermore, a significant shift towards females was observed following 49 days exposure at 50 ng/l EE2 suggesting estrogenic exposure is capable of facilitating a progression for protandric males from male-intersex-female gametal status. Increases in female vitellogenin (4 days) were predictive of later increases in female developmental stages at 21 days and increases in oocyte area following 49 days. Male vitellogenin (4 days) was predictive of decreased male percentages and lower male developmental stages at 49 days. Vitellogenin in S. glomerata is a predictive biomarker of estrogenic exposure and effect if sampled soon after exposure and at the commencement of a gonadal development cycle.

Gonad Maturation Cycle of the Sea Urchin Strongylocentrotus nudus Population Inhabiting an Artificial Seaweed Forest, Samchuk, Korea

We determined the seasonal gonad maturation in Strongylocentrotus nudus sea urchins inhabiting an artificially enhanced seaweed forest along the Samchuk Coast of Korea from April 2006 to March 2007. A total of 30 sea urchins per month were collected from the study area, and gonadosomatic index (GSI), gonad index (GI), egg diameter, and RNA/DNA variation were measured for each specimen. GSI values of female and male urchins achieved maximums of 17.6 and 17.0, respectively, in June. Based on histological studies, maximum GI values occurred in July (4.6 for females and 4.8 for males). A mean ovarian egg diameter of <TEX>$73.7\;\pm\;14.2\;{\mu}m$</TEX> was measured in August; during the main spawning period in September, mean egg diameter reached a maximum of <TEX>$74.2\;\pm\;17.8\;{\mu}m$</TEX>. The RNA/DNA ratio and RNA content for both males and females showed a distinct peak during the ripe stage in July, but another peak occurred in the spring season from March to April, when urchins deposit protein into the nutritive phagocytes of immature gonads prior to gametogenesis. The reproductive cycle of S. nudus is divided into five stages: early active (December-May), late active (March-July), ripe (July-September), spent and degenerative (August-November), and inactive (October-February). Our continuous removal of sea urchins from the study area did not influence the reproductive cycle, as populations quickly recovered, and achieved normal gonad development cycle in the site.

Age, growth, reproduction and diet of the Flatsnout Goby, Neogobius platyrostris (Pallas, 1814), on the south-eastern Black Sea Coast of Turkey

Information is given on the age structure and growth, length at first maturity, annual cycle of gonad development and diet of the Flatsnout Goby, Neogobius platyrostris (Pallas, 1814), in the Black Sea of Turkey. The maximum age was found to be 5 and 6 years for males and females, respectively. The von Bertalanffy growth parameters were estimated from the mean age-length data for males and females (males: L ∞=21.7 cm; females: L ∞=16.3 cm) and the growth performance indices were calculated for males φ’=4.21 and for females φ’=4.03. The estimated length at first maturity was 9.29 and 7.50 cm for males and females, respectively. The spawning season was between March and June. Total fecundity ranged from 103 to 990, with an average of 553±82 ripe eggs/fish. The Flatsnout Goby feeds on a wide variety of prey items, particularly on Gammaridae, Brachyura, Pisces and Isopoda.

Biological Characteristics of Rock Goby, &lt;I&gt;Gobius Paganellus&lt;/I&gt; (Actinopterygii: Perciformes: Gobiidae), in the South-Eastern Black Sea

Background. Gobius paganellus L. is one of the most common gobiid fish in the south-eastern Black Sea. The aim of present study is to provide information on age structure and growth, length at sexual maturity, annual cycle of gonad development, and diet of rock goby in the south-eastern Black Sea. Materials and methods. One hundred seventy-five specimens of G. paganellus were sampled from two stations in the province of Rize, south-eastern Black Sea. Samplings were performed by free diving using spear gun and hand net at night time. Specimens were dissected and sagittal otoliths, stomachs, livers, and gonads were removed. Otoliths were cleaned, immersed in glycerol, and examined on black background using reflected light at low magnification to determine age. Mean size at sexual maturity (L50) (i.e., size at which 50% of fish are mature) was estimated for males and females by fitting the logistic Gompertz function to the proportion of mature fish per cm size-class. The gonadosomatic index, seminal vesicle somatic index, and hepatosomatic index were calculated on monthly basis. The quantitative importance of different prey in the diet was assessed by calculating the frequency of occurrence, the percentage number, and the percentage mass of prey. The main food index (IMF) was calculated to combine the three used methods (IMF = (0.5 (%F + %N) %W)0.5). Results. The maximum age was estimated to be 7 and 6 years for males and females, respectively. The von Bertalanffy growth parameters was estimated from the mean age-length data for males and females (males: L&infin; = 13.1 cm, k = 0.34, to= &ndash;0.11; females: L&infin; = 18.2 cm, k = 0.18, to= &ndash;0.07). The estimated length at sexual maturity was 5.20 and 5.50 cm for males and females, respectively. The spawning season was between March and May. Total fecundity ranged from 1550 to 5839 eggs/female, with an average of 4322 &plusmn; 1109 eggs per female. The rock goby feeds on a wide variety of prey items, particularly on gammarids, brachyurans, natantians, bivalves, isopods, and fish. Conclusion. Growth rate (K) and growth performance index (&phi;&rsquo;), length at sexual maturity, fecundity and feeding habits of Black Sea rock goby differ from Atlantic populations.

Reproductive features and gonad development cycle of the soft bottom-gravel gorgonian Leptogorgia sarmentosa (Esper, 1791) in the NW Mediterranean Sea

Leptogorgia sarmentosa (Cnidaria: Octocorallia) is a common soft bottom-gravel gorgonian in the northwestern Mediterranean Sea. This study examined the annual reproductive cycle of a L. sarmentosa. population at a depth of 30 m, and further determined the sex ratio, the intra-colonial gonadal output variability and the age at first reproduction. L. sarmentosa was gonochoric and the population studied was characterized by a sex ratio slightly biased towards female colonies (1 male:1.6 female). Secondary branches had higher polyp fertility (number of gonads per polyp) compared to primary branches, but because of the number of polyps on the former, most of the sexual effort was actually contributed by the primary branches, as in other gorgonian species. Male colonies became fertile above a height of 21 cm, but female colonies had gonads even in the 1–10 cm height class. Spawning occurred between late August and early September, although there was no direct observation of broadcast spawning or surface brooder strategy. The maximum gonad size was 550 μm in males and 500 μm in females, with a mean diameter of 270 μm for spermaries, and 190 μm for eggs. The number of gonads per polyp prior to spawning reached 4–5 spermaries polyp!1 in male colonies, and 3–4 eggs polyp!1 in female colonies. Spawning did not appear to be synchronized with the full moon. L. sarmentosa appeared to have a different reproductive strategy to other Mediterranean gorgonians (living on hard bottom substrata), probably because of its different habitat preferences and biological (morphology, diet, prey capture rates, growth, biochemical levels) features.

Reproductive biology of the Japanese mantis shrimp Oratosquilla oratoria (Crustacea Stomatopoda): Annual cycle of gonadal development and copulation

We investigated the reproductive biology of the stomatopod Oratosquilla oratoria for both males and females of different size classes. Samples were collected from Tokyo Bay, Japan, by monthly bottom trawl surveys from May 2004 to October 2005. Histological examinations of testis, vas deferens, and penis for males and ovary and seminal receptacle for females were conducted. Males attained sexual maturity at a smaller body size (between 4 and 5 cm body length [BL]) than did females (BL > 7 cm). Although there were significant changes in the developmental stage of the testis between months, medium- to large-sized males (BL ≥ 7 cm) stored sperm in the vas deferens and penis throughout the year, indicating year-round functional maturity of the males. On the other hand, females showed clear seasonal patterns in ovarian maturation. Mature females were found between March and September. The early (May–June) and late (July–September) spawning peaks involved large (BL ≥ 10 cm) and medium (7 ≤ BL < 10 cm) size classes of females, respectively, confirming a similar trend shown by previous studies for size-related seasonal patterns in ovarian maturation. In addition, sperm was found in the seminal receptacle concurrent with ovarian maturation, suggesting that the timing of the onset of copulation is regulated by the sexual receptivity of females. This study is the first to reveal this size-related reproductive pattern in both sexes in the Stomatopoda.

한국 서해안 꽃게, Portunus trituberculatus (Miers, 1876)의 난 성숙과 산란

The gonad maturation and spawning of blue crab, Portunus trituberculatus (Miers, 1876) using samples caught by trammer net in the western coast of Korea from January to December. The gonadosomatic index (GSI) showed the highest value of 15.0 in June and lowest value of 1.29 in August. Hepatosomatic index (HSI) showed the lowest in the spawning season from June to July. Thereafter, from August the value started to increase to 5.77 in December, showing an adverse trend against GSI. In the histological studies of the female reproductive organ, the gonad filled with primary oocytes from January to February and secondary oocytes in May. The female gonads mature from June, and mature and immature groups could be distinguished from December to February or March. In August, female developed another cycle of gonad development, showing new primary oocytes in the gonads again. Some of female crabs had receptaculum filled with already active sperm cells in it from March to May. In the time of August to September, almost all the females had the sperm sacs in the receptaculum. From the result, the coupling period estimated from August to September. Total RNA and DNA values of the crabs were highest in May (2.51, <TEX>$0.57{\mu}g/mg$</TEX>). The DNA value remained unchanged except for the value in May (<TEX>$0.09-0.13{\mu}g/mg$</TEX>). while RNA value was lowest in January (<TEX>$1.08{\mu}g/mg$</TEX>). The RAN/DNA ratio was the lowest (6.23%) in May and highest (18.05%) in July. The value of correlations coefficient between body weight and fecundity of the crabs was higher that of between carapace width and fecundity.

Size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri (Pallas, 1770), in Malaysian waters

The size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri, was studied in the inter-tidal mudflat of a mangrove swamp along a 0.4–0.6 × 5 km stretch of the Sepang coastal waters, Selangor Malaysia. The size ranges of the giant mudskipper specimens caught in the study area were between 10–27.5 cm TL (20.6 ± 3.1 cm) for males and 14.5–28.5 cm TL (21.9 ± 2.3 cm) for females. Male to female sex ratio during the study was 1 : 1.1. The estimated von Bertalanffy growth parameters were L∞ = 29 cm and K = 1.4 year−1, with a growth performance index of Ø′ = 3.1. Otolith microstructure analysis revealed a strong correlation (Female: r = 0.920, n = 35; Male: r = 0.943, n = 41, P < 0.05) between the number of daily rings (number of days old) over the respective size ranges of male (8.5–19.5 cm SL) and female fish (11.8–22.3 cm SL). Four maturity stages were described to follow gonadal development based on external features; these stages were further validated through histological examination of the ovary and oocyte diameter measurements. The gonadal development cycle of P. schlosseri was asynchronous, as marked by the random mixture of early stages oocytes (diameter: 70.7 ± 14.9 μm) to matured stages (356.9 ± 20.2 μm), and had a prolonged spawning season extending from June to October. Monthly fluctuation of the gonadosomatic and hepatosomatic indices for this species was highly correlated (r = 0.126, P < 0.05).

Cycle of gonadal development in Eunicella singularis (Cnidaria: Octocorallia): trends in sexual reproduction in gorgonians

Abstract. Eunicella singularis is a gorgonian species whose members are abundant in hard‐bottom sublittoral communities of the Mediterranean Sea. The reproductive biology in this species has been examined to better understand the ability in this species to recover from recent mass mortality events. Eunicella singularis is a stable, gonochoric, iteroparous species that reproduces annually and exhibits a seasonal pattern of gametogenesis characterized by a single annual maturation of the gametes. The sex ratio did not significantly differ from 1:1. Oogenesis lasted 13–17 months, beginning between February and June, and ending with the release of 0.7 planula larvae per polyp between late May and July of the following year. The diameter of mature oocytes ranged 450–860 μm. Spermatogenesis was much shorter than oogenesis and occurred over 5–6 months. Gonadal production of both sexes increased in spring and culminated with the spawning of male colonies in late May–June. Fertilization of oocytes and development of the planula larvae occurred within the polyps of female colonies. Planula release was observed in June and July. The patterns emerging from this and previous studies on sexual reproduction of Mediterranean gorgonians suggest that investment in gonad development appears to be related to resource availability.

Gonadal development and spawning cycle in the digynic hermaphrodite sharpsnout seabream Diplodus puntazzo (Sparidae) off the Canary Islands, northwest of Africa

Summary Diplodus puntazzo is a species characterized by a rudimentary hermaphroditism, with a low level of protandry. The study found that the overall sex ratio was one male to 2.03 females, diverging significantly from 1 : 1, and that there was a ratio of one male to 0.11 transitional fish. The sex ratio varied with season: during the reproductive period the ratio was 1 : 1.86 (male : female), significantly lower than in the non-reproductive period in which the sex ratio was approximately 1 : 2.26. Both sexes had similar size distributions; however, females were predominant in all size intervals, especially in the larger ones. No significant difference in mean total length (TL) between females (330 mm), males (319 mm) or transitionals (321 mm) was found. The smallest functional female and male analysed were 159 and 157 mm TL, and the largest were 520 and 510 mm TL, respectively. No significant difference in length at first level of maturity, attained at the second year of life, was found between males (281 mm) and females (292 mm), respectively. A protracted spawning season was identified for the species: from September to February, with a peak in November. GSI values followed the same pattern for males and females, with values of females being similar to those of males; the highest values occurred between September and December, with a maximum in November. Occurrence of transitional fish was significantly higher during the month with highest values of GSI than in the resting period. The study found that vitellogenesis did not begin synchronously for all females, and the simultaneous presence of oocytes in all stages of development indicated an asynchronous mode of ovarian development. The presence of postovulatory, together with tertiary yolk vesicle oocytes, indicated that the species is a multiple spawner.

Reproductive biology of the striped goby, &lt;i&gt;Gobius vittatus&lt;/i&gt; (Gobiidae) in the northern Adriatic Sea

The striped goby, Gobius vittatus Vinciguerra, 1883 is a Mediterranean gobiid species considered to be rare and lacking in data on its reproduction. Sex ratio, length and age at first maturity, annual cycle of gonad development, spawning period and fecundity of G. vittatus were studied on 704 specimens collected by SCUBA diving in the northern Adriatic Sea (Kvarner area) from April 2001 to March 2002. The monthly sex ratio did not differ significantly, except during the spawning season, when it was strongly biased in favour of females. The estimated length at first maturity was 32.8 and 35.4 mm for females and males, respectively. In both sexes gonad development started in the first year of life. All specimens were mature by the third year. The spawning season was from April to July. Total fecundity ranged from 560 to 3045, with an average of 1426 ± 89 ripe eggs/fish. The simultaneous presence of three clearly distinct sizes of oocytes in ripe ovaries indicate that this species is a multiple spawner.

Fator de condição e aspectos reprodutivos de fêmeas de &lt;em&gt;Pimelodella&lt;/em&gt; cf. &lt;em&gt;gracilis&lt;/em&gt; (Osteichthyes, Siluriformes, Pimelodidae) no rio Amambai, de Mato Grosso do Sul

The aim of this study is to describe the seasonal variations of condition factor and of the gonadal development cycle of Pimelodella cf. gracilis in Amambai River (MS, Brazil). The length and weight of 232 individuals were measured to calculate the Allometric Condition Factor. For the females (n=162), we also obtained the ovarian weight and the gonadal maturity stages in order to calculate the GSI and the relative frequency (%) of this stages at each season of the year. Results indicate that the highest GSI values were registered in spring and summer. Thus, we concluded that the spawning season of this species occurs between October and April. However, it was not possible to identify more precisely when this event occurs. The highest values of condition factor were observed in summer, as a probable consequence of the more intensive feeding activity that individuals demonstrate during the spring.