Ripe Males Research Articles

Reproductive Phenology and Size Structure Characteristics of <i>Hypseleotris agilis</i> (Herre, 1927) in Lake Mainit, Philippines

Hypseleotris agilis locally known as Bugwan is a native species and one of the most abundant fishes of commercial value in Lake Mainit, Philippines. A total of 1,584 H. agilis from Lake Mainit near the mouth of Kalinawan and Puyo River were caught from May 2018 to February 2019 to determine the length-weight relationship (LWR), condition factor (K), gonadosomatic index (GSI) and hepatosomatic index (HSI) of this species. Positive allometric growth was observed for both sexes (b>3). Sex ratio indicated the dominance of males over females as much as 58.7%. The number of ripe males and gravid females was observed throughout the months of the collection, which indicates the ability of the fish species to spawn continuously throughout the year. Determination of GSI in both sexes showed higher values during November (males) and December (females). However, HSI values were relatively low during the spawning season, which would indicate the usage of energy for gonadal maturation. The K factor showed high values during the peak spawning months, directly proportional to GSI values. This study provides updated information for management and conservation of this important fishery resource in Lake Mainit.

Use of restored floodplains by fishes of the Middle Rio Grande, New Mexico, USA

AbstractNearly 1600 ha of habitat have been restored at 300 floodplain sites of the Middle Rio Grande (MRG), New Mexico, USA, as part of a cooperative effort of the Middle Rio Grande Endangered Species Collaborative Program to conserve the endangered Rio Grande silvery minnow (RGSM). These riverside sites are designed to inundate during spring run‐off and create ephemeral habitats for other aquatic and riparian species. This study of four restored floodplain sites in May–June 2017 found that of 14 fish species captured with fyke nets, common carp (41%), red shiner (32%), RGSM (16%) and white sucker (9%) dominated total numbers. Adult RGSM included 42% gravid females, 36% ripe males and 22% spent females, suggesting that this endangered species was spawning in and near these floodplains. Larval sampling also showed that restored sites and adjacent mainstem banklines were being used as nursery habitats, where RGSM larvae dominated six and nine species with 80% and 74% of total numbers, respectively. System‐wide proportions of RGSM larvae by phase suggest that larvae leave the floodplains and move to mainstem banklines beginning as late mesolarvae and metalarvae (14–22 days post‐hatch), and most depart by the juvenile stage. Altogether, 15 fish species were encountered in restored floodplain sites in 2017, compared to 16 species reported in concurrent annual mainstem monitoring. This study and others show that most fish species of the MRG move onto restored and natural floodplains equally in spring, and many use these habitats for spawning and as larval nurseries.

Reproductive Phenology and Size Structure Characteristics of <i>Hypseleotris agilis</i> (Herre, 1927) in Lake Mainit, Philippines

Hypseleotris agilis locally known as Bugwan is a native species and one of the most abundant fishes of commercial value in Lake Mainit, Philippines. A total of 1,584 H. agilis from Lake Mainit near the mouth of Kalinawan and Puyo River were caught from May 2018 to February 2019 to determine the length-weight relationship (LWR), condition factor (K), gonadosomatic index (GSI) and hepatosomatic index (HSI) of this species. Positive allometric growth was observed for both sexes (b>3). Sex ratio indicated the dominance of males over females as much as 58.7%. The number of ripe males and gravid females was observed throughout the months of the collection, which indicates the ability of the fish species to spawn continuously throughout the year. Determination of GSI in both sexes showed higher values during November (males) and December (females). However, HSI values were relatively low during the spawning season, which would indicate the usage of energy for gonadal maturation. The K factor showed high values during the peak spawning months, directly proportional to GSI values. This study provides updated information for management and conservation of this important fishery resource in Lake Mainit.

Life history, distribution and seasonal movements of a threatened South African endemic seabream, Chrysoblephus gibbiceps

The red stumpnose Chrysoblephus gibbiceps (Sparidae) is a South African endemic seabream that has been severely depleted by fishing. A total of 678 C. gibbiceps were sampled by line and trawl fishing for a study of their morphology, age, growth, reproduction and diet. In addition, catch records from three time-periods since 1897 were interrogated for distribution patterns and movement behaviour. The sex ratio was 1.5:1 in favour of males. The length–weight relationship, W = 9.32 × 10−5 LF2.811, indicates hypoallometric growth. The bulbous head of large males is a secondary sexual characteristic. A von Bertalanffy growth model was fitted to age data obtained using otolith analyses: LF = 429.9 × (1 – e−0.113(t – (−3.799)). The maximum recorded age was 48 years, which is among the highest in seabreams, though the species matures after only 3 years. The gonadosomatic index (GSI) of ripe females (4.5%) was comparatively low, and the two-month-long early-summer spawning season was short compared with that of other sympatric seabreams. The very low GSI of ripe males (1.6%) suggests courtship battles and polygamy. The species feeds over low-profile reefs and consolidated sediments. The principal prey are ophiuroids. Although its trophic level is 3.7, C. gibbiceps has a low-nutrition diet. Historical and current catch data confirm a distribution from Cape Point (southeastern Atlantic) to southern KwaZulu-Natal Province (western Indian Ocean). There is evidence for localised migratory patterns, now partly lost due to severe population depletion. Whereas protogyny and resident behaviour have been suggested as traits that render seabreams vulnerable to fishing pressure, C. gibbiceps is a shoaling gonochorist that has collapsed due to fishing.

Functional feminization of the Mexican snook (Centropomus poeyi) using 17β estradiol in the diet

The Mexican snook, Centropomus poeyi , supports an important fishery in southeastern Mexico. Due to its protandrous hermaphroditism, females may be especially sensitive to overfishing because they tend to be larger and selective removal has the potential to negatively affect natural populations, thus making urgent the need to contribute on management strategies for the species. The objective of this study was to produce batches of reproductive females at an early age and a small size by using 17β-estradiol (E2) in the diet. In two separate experiments, we fed fish 0, 10, 20, 30, 40, 50, or 60 mg of 17β-estradiol per kg of food for 60 days during gonadal differentiation. Fish fed with 50 and 60 mg of E2 per kg of food resulted in 100% feminization, while the control group (0 mg of E2) was 100% male. Three years after feminization, sex-reversed fish remained female, producing oocytes and were capable of spawning, while fish in the control group were ripe males with running milt. E2-treated groups were significantly larger (weight and length) than the control groups for up to six months after treatment, but the difference was undetectable at 300 days post-treatment. Survival was high in all treatments (100%). We obtained high percentages of functional females using dosages of 50 and 60 mg kg -1 of E2 for 60 days, with 80% of the induced fish spawning and producing fertilized eggs and larvae. The results obtained in this study provide opportunities for broodstock management and sex manipulation.

Age, growth, sex ratio, spawning season and fecundity of Capoeta razii from Sefidroud River in the southern Caspian Sea basin

Some aspects of reproductive biology of Capoeta razii , an endemic cyprinid species from the Sefid River in the southern Caspian Sea basin, were studied by monthly sampling throughout a year. Age, growth, sex ratio, spawning season, fecundity, gonado-somatic, modified gonado-somatic and Dobriyal indices were estimated. The sex ratio (F: M) was obtained as 1.00:2.63, and the percentage of males was greater than females. The mature males and females were longer than 88 and 148 mm in total length, and 1 + and 2 + in age, respectively. The spawning of C. razii took place from late May to late August when the water temperature was between 19.7 and 22.8 ◦ C. At the beginning of the reproduction period, the average gonado-somatic index values were 10.0% ranging from 4.03% to 15.90% in ripe females. The estimated gonadal indices showed that the ripe males were ready to spawn earlier than females. The average egg diameter was 0.99±0.65, ranging from 0.2 to 2.3 mm. The averages absolute and relative fecundity were 4386±2174 and 66.3±37.8, respectively. The absolute fecundity was significantly related to body weight and gonad weight.

Females exceed males in mercury concentrations of burbot Lota lota.

Examination of differences in contaminant concentrations between the sexes of fish, across several fish species, may show clues for important behavioral and physiological differences between the sexes. We determined whole-fish total mercury (Hg) concentrations of 25 male and 25 female adult burbot Lota lota captured in Lake Erie during summer 2011 and of 14 male and 18 female adult burbot captured in Great Slave Lake (Northwest Territories, Canada) during winter 2013. On average, females had 22% greater Hg concentrations than males. This difference was probably not due to a greater feeding rate by females because results from previous studies based on polychlorinated biphenyl determinations of these same burbot indicated that males fed at a substantially greater rate than females. Based on our determinations of Hg concentrations in the gonads and somatic tissue of 5 ripe females and 5 ripe males, this difference was not attributable to changes in Hg concentration immediately after spawning due to the release of gametes. Furthermore, bioenergetics modeling results from previous studies indicated that growth dilution would not explain any portion of this observed difference in Hg concentrations between the sexes. We therefore conclude that this difference was most likely due to a substantially faster rate of Hg elimination by males compared with females. Male burbot exhibit among the greatest gonadosomatic indices (GSIs) of all male fishes, with their testes accounting for between 10 and 15% of their body weight when the fish are in ripe condition. Androgens have been linked to enhanced Hg-elimination rates in other vertebrates. If androgen production is positively related to GSI, then male burbot would be expected to have among the greatest androgen levels of all fishes. Thus, we hypothesize that male burbot eliminate Hg from their bodies faster than most other male fishes and that this explains the greater Hg concentration in females compared with males.

Development of the brittle star Ophiothrix exigua Lyman, 1874 a species that bypasses early unique and typical planktotrophic ophiopluteus stages

The development of Ophiothrix exigua from spawning through metamorphosis was studied by light and scanning electron microscopy. When some ripe males and females were kept in the same container and subjected to cycles of temperature and light shock, males released sperm, and then, females spawned eggs. After release, spermatozoa survived for approximately 28 h at 24 °C. After fertilization, the egg surface changed from smooth to wrinkled, and then, the fertilized eggs produced polar bodies. After the wrinkles disappeared, the eggs started to cleave holoblastically and equally. The arrangement of blastomeres was irregular after the third cleavage. The embryonic surface developed a thick hyaline layer, and blastomeres were connected to each other by projections and filopodia. After the wrinkled blastula stage, embryos hatched and primary mesenchyme cell ingression occurred. At the initiation of gastrulation, embryos formed tetraradiate spicules and then became typical planktotrophic ophioplutei with four pairs of larval arms. The larvae developed coelomic pouches on their left and right sides, and the pouches divided into anterior and posterior parts. After the left anterior pouch formed a hydropolic lobe, the larvae resorbed all inner larval arms except for the posterolateral arms and then formed an adult rudiment. Finally, juveniles released the pair of posterolateral arms and completed metamorphosis. Our findings indicate that larval development (typical planktotrophic ophioplutei until metamorphosis) of O. exigua is similar to that of other Ophiothrix species, but early development is modified involving the formation of the wrinkled eggs and blastulae.

Occurrence, habitat, and movements of the endangered northern madtom (Noturus stigmosus) in the Detroit River, 2003–2011

The northern madtom (Noturus stigmosus or NOM) is a small catfish, native to North America. It is globally vulnerable and endangered in Canada, Ontario, and Michigan. In 1994 and 1996, it was found in the St. Clair River and in Lake St. Clair, respectively. However, it had not been found downstream in the Detroit River since 1978. We report catches of 304 NOM from 2003 to 2011 and describe their mud and sand habitats in the deep (10m), dark, Detroit River. We found adult NOM, including 3 ripe males (90–107mm SL) in head waters of the river near Belle Isle in Michigan waters, and both adult and 4 juvenile NOM (21–30mm SL) near Peche Island in Ontario waters. From 2009 to 2011, in the river's middle reach, we caught 7 adult NOM for the first time near Fighting Island in Ontario waters, but no NOM in the river's lower reach. Our mark–recapture results showed that within 6weeks, 2 adult NOM moved east 2.0km from Michigan waters near Belle Isle across the deep (10m) Fleming Channel of the Detroit River to Canadian waters near Peche Island. Analysis of annuli from pectoral spines of 7 dead NOM revealed that they live to at least 6years of age in the Detroit River. This is the first age data that we could find for a NOM population. Our findings extended our knowledge of habitat, reproductive ecology, age, and distribution of NOM in the Detroit River corridor.

Population size structure, growth and reproduction of the European anchovy (Engraulis encrasicolus, L.) in the Lagoon of Lesina (south-western Adriatic Sea, Italy)

1 - The purpose of this study was to describe the basic characteristics of the European anchovy occurring in the Lagoon of Lesina in order to increase our knowledge of the ecology of the species in a lagoon ecosystem. 2 - Samples were collected between May and November 2012 using fyke nets. A hundred individuals per sample were measured and weighed. Sex was determined and the fish gonads were macroscopically classified. Length-frequency histograms were obtained, and the length-weight relationships and condition factors were estimated. 3 - The results of this study showed that the anchovies caught in the Lagoon of Lesina were relatively small. The growth of anchovies in the lagoon was often positively allometric (b>3) and exponent b was frequently greater than the value estimated for specimens in the Adriatic Sea in the same months. 4 - The sex ratio of anchovies in this study was skewed towards females in almost all the sampling period. Macroscopic analysis of the gonads revealed that spawning took place during spring-summer, and it prolonged until October in the females. One peak of ripe females and males was observed in June and one in August-September. 5 - This study suggests that the anchovy population in the Lagoon of Lesina is probably composed of a large number of young individuals at the first maturity. Individual growth seems to be positively affected by the environmental conditions of the lagoon, which probably provide the anchovies with a substantial trophic advantage.

Reproductive traits of Gymnogeophagus labiatus (Teleostei, Cichlidae), in an upper stretch of Sinos river, Caraá, Brazil

This work describes the reproduction of Gymnogeophagus labiatus (Hensel, 1870) from an upper stretch of Sinos river, southern Brazil, based on the analysis of 174 males and 132 females captured in monthly samples taken from January to December 2007. Results showed that reproductive activity occur in spring and summer although ripe males were found along the year. The standard length of the smallest ripe male was 104.74 mm (Lt) and the smallest ripe female was 55.00 mm (Lt). There was a significant difference in total sex ratio, with 1.32 males to each female (χ2 = 5.76). Males were much more abundant in March (1.75 males: 1 female) and December (5 males: 1 female). Females were more abundant in the 62├77 mm interval (1 male: 2.36 female) while males were more abundant in the 77├92 mm size interval (2.57 males: 1 female). The largest length intervals were composed of only males. Mean absolute fecundity was 113.4 (± 31.24 sd) and mean relative fecundity was 0.0125 (± 0.0026 sd) oocytes/mg. In ripe ovaries, small-diameter oocytes were observed at high frequencies while larger ones occurred at lower frequencies. This pattern is common in fishes with asynchronous oocyte development. Characteristics of G. labiatus, such as low fecundity, asynchrony in oocyte development, multiple spawning, and its well-known parental care behavior, are consistent with an equilibrium strategy, as proposed for other cichlids.

Sexual Maturation and Milt Quality of the San Pedro Mártir Trout Using an Artificial Photoperiod

AbstractThe sexual maturation and milt quality of the San Pedro Mártir trout Oncorhynchus mykiss nelsoni (SPMT) were studied in captivity using an artificial photoperiod and a recirculating system that kept the water quality within the range recorded in the natural habitat of this subspecies. During the 21.8 months of the study, male SPMT reached the highest weight (379 ± 48 g [mean ± SD]) and total length (344 ± 19 mm) recorded for this type of trout. Male maturation was induced at 7.5 months. Eight ripe males (200–320 mm total length) were stripped by abdominal pressure to obtain milt on six occasions from January to April 2009, at intervals ranging from 2 to 4 weeks. Spermatozoa motility varied from 80% to 95%, with a maximum duration of 50–55 s. Milt volume ranged from 165 to 228 μL per organism, and spermatozoa concentration ranged from 235 × 106 to 4,772 × 106 cells/mL. The mean spermatozoa flagellum length was 33.17 μm, and head width and length were 2.14 and 2.72 μm, respectively. This work demonstrates that San Pedro Mártir trout can be maintained and induced to mature sexually in a recirculating system using artificial photoperiod and temperature control. This information can be useful in management and conservation programs for this endemic trout in Mexico.

Differentiated gonochorism in Nile perch Lates niloticus from Lake Victoria, Uganda

Gonadal development and structure were examined in 317 Nile perch, Lates niloticus, of 4 to 157 cm SL taken from Lake Victoria, Uganda, in 2005–2006. Macroscopic and histological investigation showed a differentiated gonochoristic pattern, with no juvenile intersexuality. Oogonial cells (9.8 ± 3.0 μm) developed through six distinct stages: chromatin nucleolar oocyte (16.2 ± 3.3 μm), perinucleolar oocyte (33.8 ± 12.1 μm), late perinucleolar oocyte (74.8 ± 16.5 μm), cortical alveolar oocyte (122.6 ± 38.8 μm), secondary oocyte (260.9 ± 61.2 μm) and tertiary oocyte (475.5 ± 70.7 μm). L. niloticus was found to be an asynchronous spawner. The collection of female brood fish for induced spawning should aim at fish with an oocyte size of 475.5 ± 70.7 μm. Four main developmental stages were identified in the testis: spermatogonia (A and B), primary and secondary spermatocytes, spermatids and spermatozoa. Testicular structure conformed to the lobular and cystic type. Copious amounts of sperm were exuded from ripe males when slight pressure was applied on the belly. Milt could therefore be obtained by stripping.

Reproductive cycle and size at first sexual maturity of Hexaplex trunculus (Gastropoda: Muricidae) in the Gulf of Gabès (southern Tunisia)

The reproductive cycle and size at first sexual maturity of the banded murex (Hexaplex trunculus) from the tidal areas of the Gulf of Gabès (southern Tunisia) were investigated from June 2007 to May 2008 through macroscopic analysis of the gonads and monthly variations in the general condition (K) and gonadosomatic indices (GSI). This muricid gastropod is gonochoristic (separate sexes throughout life) and lacks external sexual dimorphism. The overall sex-ratio of the population was significantly unbalanced, with a predominance of females (M:F = 1:1.6). The monthly variation in the gonad maturation stages, K and GSI revealed that H. trunculus has a yearly reproductive cycle, with both sexes showing a long period of gonadal activity and slightly asynchronous gametogenic cycle. Gametogenesis occurred during most of the year (11 out of 12 months examined) and almost every gametogenic stage was observed throughout the study period. Ripe males were found mainly from November to January, preceding the main period of gametic emission (between January and May). Ripe females occurred mainly from February to April, preceding the main spawning season (between April and May), apparently triggered by the increasing daylength and seawater temperature during this period (from 13.2 to 14.2 h and from 19.3 to 23.4°C, respectively). Both sexes displayed a relatively short resting phase (males: June—July; females: June—September), coincident with the highest daylength and seawater temperature during summer in the Gulf of Gabès. The first sexual maturity was reached at a smaller size in males (SL50 = 36.9 mm SL) than in females (SL50 = 50 50 40.3 mm SL). The information gathered in this study allowed preliminary management measures for the fishery to be proposed, including a closed season during the main spawning season (April—May) and the establishment of a minimum landing size (of at least 40 mm SL) for H. trunculus from the Gulf of Gabès.

ChemInform Abstract: Potential Sex Pheromone in Platynereis dumerilii. Identification and Synthesis.

Abstract 5-methyldecane ( 6a,b ) was extracted from ripe males of Platynereis dumerilii by using a closed loop stripping technique and identified by GC-MS and synthesis. This substance is a minor component of the pheromone bouquet and elicites an electrophysiological response in females of Platynereis dumerilii .

Der Kolibrisalmler Trochilocharax ornatus gen. et spec. nov. - ein neuer Salmler aus Peru (Teleostei: Characiformes: Characidae)

Trochilocharax ornatus gen. et spec. nov. – a new, small (up to 17.0 mm SL) characid fish from Peru is described. Presumably it has an internal insemination. The new genus and species is characterized by a naked, scaleless body. Only the sexually ripe males have a puoch scale like the members of the subfamilies Glandulocaudinae and Stevardiinae. The females and sexually immature specimens of both sexes have no scales. The puoch scale covers a convexity (a gland?), what indicates to an internal insemination. Further features are: D ii 7; A iv 22 – 24, seven (fourth to tenth) anal-fin rays with one relatively large hook in the anterior part of the fin; all other fins without hooks; maxilla long and narrow, with fi ve to eight conical teeth on the anterior part of the bone; praemaxilla and anterior part of lower jaw with irregularly distributed conical teeth, partly protruding out of the mouth. 34 – 35 (4 + 8 + 22 – 23) vertebrae. There is a remarkable sexual dimorphism and sexual dichromatism. The phylogenetical position of the genus is unknown. It belongs to the Stevardiinae but not to the Xenurobryconini, because there is no synapomorphy of the Xenurobryconini developed. For this reason a new tribus – Trochilocharacini trib. nov. – is created for the new genus Trochilocharax.

A new, dwarf species of Grammonus (Teleostei: Bythitidae) found off Vietnam

A new species of the viviparous fish genus Grammonus (Ophidiiformes: Bythitidae) is described, based on two ripe males, 32-55 mm SL. They were caught over a muddy bottom in a shrimp trawl at 70-119 m off Central Vietnam. A comparison with the nine hitherto described Grammonus species shows them to be clearly distinct from other species. Except for G. ater, G. minutus differs from all other species by having either more or fewer dorsal (75-76) and anal (54-55) fin rays. It differs from G. ater i.a. by having more pectoral fin rays (22-23 vs. 18-19).

Some reproductive traits of the Tristan klipfish, Bovichtus diacanthus (Carmichael 1819) (Notothenioidei: Bovichtidae) from Tristan da Cunha (South Atlantic)

The reproductive biology of the Tristan klipfish, Bovichtus diacanthus, was investigated by macroscopic and histological analyses of the gonads. Fish samples were collected in tide pools at Tristan da Cunha in July 2004. Most specimens of both sexes were developing, or sexually mature, with a gonadosomatic index (GSI) of 7.0–9.2% in females and 0.2–0.6% in males. Histologically, testes showed a random distribution of spermatogonia along the lobules, a condition defined as the unrestricted spermatogonial type. Ripe males exhibited lobules with all spermatogenic stages of development from spermatogonia to spermatozoa. In mature females, the ovarian follicles consisted of three main cohorts of oocytes of different sizes; the smaller one represented by previtellogenic oocytes of 15–150 μm and the other two by yolked oocytes measuring, respectively, 300–1000 and 800–1500 μm. The overlap between the stock of advanced yolked oocytes and the early yolked oocytes was low, decreasing progressively with final maturation. As a result, B. diacanthus was considered a batch spawner, with a spawning season extending from July to August onward. Batch fecundity, based on the most advanced yolked oocytes, was 2,047–8,317 mature oocytes/female, whereas the relative fecundity was 77–141 mature oocytes/g. In the light of the phyletically basal position of bovichtids in the suborder, the reproductive traits of B. diacanthus were compared with those previously described in other Antarctic and non-Antarctic notothenioids.

Sperm velocity influence paternity in the Atlantic cod (Gadus morhua L.)

Sperm competition is recognized as an important selective force in reproductive biology (Birkhead & M ller 1998) and it occurs when sperm from more than one male compete for fertilization of the ova (Parker 1970). Sperm competition has led to the evolution of adaptive sperm traits (Andersson 1994; Birkhead & M ller 1998), and several studies on ¢sh species have shown a strong positive correlation between fertilization or hatching rate and sperm motility (Kime,Van Look, Mcallister, Huyskens, Rurangwa & Ollevier 2001; Kupriyanova & Havenhand 2002; Gage, Macfarlane, Yeates, Ward, Searle & Parker 2004; Schulte-Hostedde & Burness 2005; Casselman, Schulte-Hostedde & Montgomerie 2006). However, in species with sperm competition, males not only need to be able to fertilize the eggs, but in addition, do better than the competing males to achieve fertilization. Although sperm competition is widespread among ¢sh species (Stockley, Gage, Parker & M ller 1997; Taborsky1998), few studies have examined the in£uence of diierent sperm traits on relative paternity when males compete for fertilization. The Atlantic cod (Gadus morhua L.) aggregate annually at spawning areas in spring, and spawning pairs are often joined by several satellite males that shed their sperm among the newly released eggs (Brawn 1961). In addition, multiple paternities per spawning bout are found in captivity (Hutchings, Bishop & Mcgregor-Shaw 1999; Rakitin, Ferguson & Trippel 1999). Thus, it seems likely that the Atlantic cod is naturally adapted to sperm competition. Wild-caught sexually mature adult Atlantic cod were trawl captured in the basin of Balsfjord (69119 0N, 19121 0E), Northern Norway, in April 2005. Four ripe males and ¢ve ripe females were randomly selected for the breeding experiment, and their gametes were collected by gently applying pressure to their abdomen after drying the ¢sh surface to avoid contaminating the samples. As each female produces millions of small eggs that are externally fertilized, we were able to conduct controlled in vitro fertilization while concurrently measuring sperm traits. Sperm from fourmales weremixed and shed over unfertilized eggs from ¢ve diierent females in an aqueous environment to which Atlantic cod is naturally adapted, in order to examinewhat sperm traits determine relative paternity. An aliquot (o0.12 mL) of undiluted milt placed on a cooled (approximately 5 1C) microscope slide with an 80-mm-deep chamber was used for spermmotility analyses. Sperm motility was induced in a one-step procedure by adding 4.5 mL seawater before applying the coverglass. A video camera (Sony XC-ST50CE, Sony, Tokyo, Japan) mounted on a negative phasecontrast microscope (Olympus CH30, Olympus, Tokyo, Japan) ( 10 objective) was used to record sperm activity from each male. Sperm swimming activity was recorded twice for eachmale and stored on MiniDV tapes. Computer-assisted spermanalysis was used to examine sperm motility in ¢sh, and a total of 2548 sperm cell trajectories were analysed using an HTM-CEROS sperm tracker (CEROS version 12; Hamilton Thorne Research, Beverly, MA, USA). The sperm analyser was set as follows: frame rate 50Hz; number of frames 25; minimumcontrast 9; andminimum cell size 8 pixels. Four qualitatively diierent Aquaculture Research, 2008, 39, 212^216 doi:10.1111/j.1365-2109.2007.01863.x

Cloning of FSH‐β, LH‐β and glycoprotein hormone α subunits in pejerrey Odontesthes bonariensis (Valenciennes): expression profile and relationship with GnRH expression and plasma sex steroid levels in male fish

Three cDNAs encoding pejerrey Odontesthes bonariensis follicle stimulating hormone‐β (FSH‐β), luteinizing hormone‐β (LH‐β) and glycoprotein‐α (GPH‐α) subunits were cloned and characterized. Gene expression of these subunits was analysed by real‐time polymerase chain reaction (PCR) and compared with the brain gene expression of endogenous gonadotropin‐releasing hormones (GnRHs): Pacific salmon GnRH (GnRH‐III), pejerrey GnRH (GnRH‐I) and chicken GnRH‐II (GnRH‐II) and plasma sex steroid levels in adult males. The nucleotide sequences of the FSH‐β, LH‐β and GPH‐α subunits are 466, 558 and 677 base pairs long, encoding for mature peptides of 102, 118 and 98 amino acids respectively. Maturing males had high expression of FSH‐β and GPH‐α subunits, and intermediate levels of LH‐β when compared with running ripe and spent stages. These animals had the lowest plasma testosterone (T) and 11‐ketosterone (11‐KT) values as well as low expression of sGnRH, cGnRH‐II and pjGnRH. Running ripe males had the lowest expression of FSH‐β and the highest expression of LH‐β and GPH‐α subunits, and of the three GnRH genes. At this stage, the highest values of T and 11‐KT were observed. Spent males showed low expression of the three gonadotropin (GtH) subunits, sGnRH, pjGnRH and low levels of T. At this stage, 11‐KT levels and cGnRH‐II expression showed a tendency to decrease but the values were not statistically significant (P < 0·05) to running ripe stage. The present results would suggest that T and 11‐KT modulate the expression of the FSH subunits. The expression of the anterior brain GnRH variants, sGnRH and pjGnRH is correlated with LH‐β expression and reinforce the importance of the forebrain GnRH variants on the regulation of pituitary function.