Immature Males Research Articles

Growth and maturation of Atlantic salmon ( Salmo salar) populations with different grilse proportions under natural photoperiod and superimposed nighttime light

This study determined the influence of night illumination, superimposed on the natural photoperiod, upon growth performance in two different stocks of Atlantic salmon ( Salmo salar). One stock had been selected to yield a low proportion of grilse (fish that mature after one winter in the sea) and the second a high proportion of grilse. Growth based on weight gain, gender, and sexual maturity of 250 individually tagged postsmolts in each of four pens was analyzed using five Atlantic salmon groups; mature females and males, immature females and males, and precocious males (the earliest mature males that produce sperm), identified during and at the end of culture. Both stocks under natural photoperiod generally showed that mature females and males grew faster, followed by immature females and males, and followed by precocious males. Mature males in both stocks did better than their respective mature females and growth of immature males in the high grilse stock was similar to mature males during the last two months of rearing. Precocious males had variable growth, depending on population origin. In contrast, salmon groups in stocks subjected to nighttime light did not show growth disparity, and each group grew faster when compared to the same group under natural photoperiod, except for mature females and males from the low grilse stock. Percentage of maturation in the low grilse stock was low and not significantly different between natural photoperiod (21%) and nighttime light (16%) treatments, whereas the high grilse stock reached 87% and was significantly reduced to 56%, respectively. This reduction occurred in mature females and males, except precocious males, whose proportion remained similar in both treatments.

Schistosoma mansoni: SmLIMPETin, a member of a novel family of invertebrate-only regulatory proteins

Eukaryotic LIM domain proteins contain zinc finger forming motifs rich in cysteine and histidine that enable them to interact with other proteins. A cDNA clone isolated from an adult schistosome cDNA library revealed a sequence that coded for a novel class of proteins bearing 6 LIM domains and an N-terminal PET domain, SmLIMPETin. Phylogeny reconstruction of SmLIMPETin and comparison of its sequence to invertebrate homologues and to the vertebrate four-and-a-half LIM domains protein family (FHLs), uncovered a novel LIM domain protein family, the invertebrate LIM and PET domain protein family (LIMPETin). Northern blots, RT-PCR and Western blot showed that SmLIMPETin gene was less expressed in sexually mature adult females compared to sexually immature adult females and sexually mature and immature adult males, and not expressed in schistosomula.

Total calcium and inorganic phosphate in the blood plasma of farmed rainbow trout,Oncorhynchus mykiss

Reference (physiological) value intervals determined by the lower 2.5% and upper 97.5% quantiles were calculated for total calcium (Cat) and inorganic phosphate (P) in farmed rainbow trout, Oncorhynchus mykiss, at an age of 10–12 months in raceway culture. Total calcium levels were significantly (P≤0.0009) greater in males (2.63–4 mmol L−1, n=47, mean weight 359±142 g) than in immature females (2.48–3.97 mmol L−1, n=410, mean weight 400±145 g). The reference range for P in immature females and males was 3.09–9.32 mmol L−1 (n=467, mean weight 401±144 g). The distribution and density of the quantiles in the tested reference group were made possible by the use of histograms, which showed normal distributions for Cat in males but not for Cat and P in immature females and males, in which a sinistral asymmetry was found.

Xenografting of sheep testis tissue and isolated cells as a model for preservation of genetic material from endangered ungulates

Recovery of germ cells could be an option for preservation of the genetic pool of endangered animals. In immature males, xenografting of testis tissue provides the opportunity to recover sperm from these animals. In adult animals, xenografting has been less successful, but de novo morphogenesis of functional testis tissue from dissociated testis cells could be an alternative. To assess the potential use of these techniques in endangered bovid species, the domestic sheep was used as a model. Testes from 2-week-old lambs were grafted as tissue fragments or cell suspensions into nude mice. Grafts were recovered at 4, 8, 12 and 16 weeks post grafting. For isolated cells, two additional time points at 35 and 40 weeks after grafting were added. In addition, to analyse the possible effect of social stress among mice within a group on the development of the grafts, testis tissue grafts were recovered 13 weeks post grafting from mice housed individually and in groups. Complete spermatogenesis occurred in sheep testis xenografts at 12 weeks, similar to the situation in situ. Isolated sheep testis cells were able to reorganize and form functional testicular tissue de novo. Housing mice individually or in groups did not have any effect on the development of xenografts. Xenografting of testis tissue might be useful to obtain sperm from immature endangered ungulates that die prematurely. Testis tissue de novo morphogenesis from isolated cells could open interesting options to recover germ cells from mature males with impaired spermatogenesis.

Differential Development of Breeding Plumage in Adult and Second-Year Male RuffsPhilomachus pugnax

We studied the development of breeding plumage in 641 Ruff Philomachus pugnax males during spring in 2004–2006 in southern Belarus with special emphasis on the growth rate of ruff and tuft feathers, which are the most colourful and spectacular parts of the male plumage. During northward migration, male Ruffs arriving in the end of March or early April showed a mixture of winter and striped feathers. The first adults with fully developed breeding plumage were recorded in the last 10 days of April and the proportion of individuals with breeding plumage gradually increased through spring. However, individuals with at least traces of winter or striped plumage were caught during the whole study period. Birds did not shed the whole winter plumage at once, which is typical for Ruff males in western Europe. Immature (second year) birds were less advanced in developing breeding plumage than adults. Only 20% of all 55 trapped second-year males were in full breeding plumage. During the main migration period there were no annual differences in the growth rate of breeding plumage feathers. Ruff lengths increased 1.6 mm/day in adults and 1.5 mm/day in second-year males, whereas the tuft grew 1.1 mm/day in adults and 1.0 mm/day in immatures. Although growing rates of ruff and tuft feathers were similar in immatures and adults, immature males started to moult into breeding plumage later than adults, resulting in less developed breeding plumage when they departed to the breeding grounds. As second-year males had lower body mass and slower body mass increase than adults, it was proposed that energetic constraints during migration are the main reason of delayed moult into breeding plumage in immature birds.

Age, growth and reproduction of the barrelfish Hyperoglyphe perciformis (Mitchill) in the western North Atlantic

Otoliths (n = 847) and gonads (n = 817) were collected from barrelfish Hyperoglyphe perciformis that were captured by commercial fishermen in the waters off South Carolina and Georgia in 1995, 1997 and 2001–2006. Of the otoliths collected, 97% were aged successfully, and specimens sampled ranged from 5 to 85 years, with a median age of 12 years. The von Bertalanffy growth parameters yielded the equation: Lt= 857·8{1 − e−0·0985[t−(−8·95)]}, where Ltis fork length (LF) at time t. Through histological examination, 94% of the gonads assessed were assigned to a sex and reproductive class. Females spawned from September to May with a peak from November to January. Males spawned year round, but had a peak from September to April. The sex ratio (M:F) for this population was 1:1·34. The smallest mature female was 605 mm LF and the youngest immature female was 697 mm LF. Estimates of LF and age at 50% maturity (L50 and A50) for females were 660 mm LF (95% CI = 633–667 mm LF) and 6·08 years (95% CI = 3·50–7·27 years), respectively. The youngest mature male was 575 mm LF and the oldest immature male was 762 mm LF, and no estimates of L50 or A50 were made for males. It was determined that barrelfish exhibit the typical characteristics of long life span, slow growth and high age at maturity seen in other deepwater fishes, and that care should be taken to manage this species accordingly.

Olfactory Sex Attraction and Mating Behaviour in the Pine Sawyer Monochamus galloprovincialis (Coleoptera: Cerambycidae)

The pine sawyer Monochamus galloprovincialis Olivier (Coleoptera: Cerambycidae) is a vector of the pine wood nematode Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle. Male and females of this species have a kairomonal attraction to host volatiles and Ips semiochemicals. Once on the host tree, males and females copulate and oviposition occurs. Bioassays using Y-tube olfactometry revealed that females were attracted to volatile compounds produced by males, but not to volatiles produced by females. However, immature males did not seem to release attractants for mature females and immature females did not show any attraction for mature males. A experiment designed to know about mating behaviour in this specie revealed that most of the males encountered females while they were walking. In all pairs both sexes contacted with antennae before copulation, however, in some occasions copulation did not proceed just after antennal contact. On the contrary, in all pairs observed, the male licked the elytra of the female with his mouth palpi just before copulation (licking); immediately afterwards, the male grabbed the female with his forelegs and mounted her suggesting a chemically mediated mate recognition by males.

Metabolism of adrenal androgen and its impacts on prostate cancer after castration

Metabolism of adrenal androgen and its impacts on prostate cancer after castration

Ontogenetic and sexual variation in the coloration of the lacertid lizards Iberolacerta monticola and Podarcis bocagei. Do the females prefer the greener males?

AbstractChanges in the coloration of the lacertid lizards Iberolacerta monticola and Podarcis bocagei with age in populations from NW Spain are described. The onset of sexual maturity in P. bocagei males involves a change in the ventral (yellow) and dorsal (green) colorations, which is different from immature males (dorsally brownish in color). In I. monticola males, the ventral coloration also changes to a deep green when they reach maturity, while the dorsal coloration remains brownish as in the immature specimens. In this species, the green dorsal coloration is acquired gradually after maturity. Only the oldest individuals have a predominantly green dorsal coloration. The differences between the two species in the time males take to acquire the green dorsal coloration could be related to their different longevity. The coloring is acquired gradually in the most long-lived species (I. monticola). A field study was carried out on the behaviour of adult males of I. monticola during the reproductive period. The males with green dorsal coloration were seen to pair with females significantly more frequently than those with the brownish dorsal color. The increase in the green dorsal coloration (conspicuous) with the size and age of the males of this species would appear to have a clear function as an intersexual or intrasexual signal.

Male elimination in the honeybee

In a striking example of sex allocation modification, female social insect (hymenopteran) workers sometimes cannibalize a fraction of their colony’s immature males. The commonly cited explanation for this male elimination is that workers are in genetic conflict with the queen and are biasing the colony’s sex allocation in their favor. However, this behavior might allow workers to tailor their colony’s investment in reproduction to environmental conditions and therefore might play an important role even in the absence of queen‐worker conflict. So far, male elimination has been demonstrated only in species where the potential for queen‐worker conflict is high. Here we present experimental evidence for facultative male elimination in the honeybee, a species where queen‐worker conflict is expected to be minimal or absent because of multiple mating by the queen. We manipulated the abundance of older male brood in colonies and found that survival of younger male larvae was lower when we increased the abundance than when we decreased it. Survival of worker larvae was high across colony conditions. These results suggest that genetic conflict is not a necessary precondition for male elimination in social insect societies. Instead, male elimination might sometimes reflect adaptive adjustment of male reproductive function, potentially increasing colony efficiency in the interests of all colony members. Key words: cooperation, kin selection, male elimination, male reproductive function, queen‐worker conflict, sex allocation. [Behav Ecol]

Foraging Behavior of the Mealybug Parasitoid Anagyrus sp.nov. nr. sinope (Hymenoptera: Encyrtidae)

Anagyrus sp. nov. nr. sinope Noyes and Menezes (Hymenoptera: Encyrtidae) is a candidate biological control agent against the Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae). This study reported on the components of the oviposition behavior of Anagyrus sp. nov. nr. sinope in relation to 6 developmental stadia of P. madeirensis: crawlers, second-instar nymphs, third-instar immature females, third-instar immature males, prereproductive adult females, and ovipositing adult females. A behavioral sequence and a time budget were prepared for Anagyrus sp. nov. nr. sinope, indicating that the parasitoids foraging in a patch containing third-instar and prereproductive adult females had the highest probability to encounter and eventually parasitize a host. The parasitoids attacking third-instar and prereproductive adult females also spent the largest proportion of total foraging time in oviposition (67 and 69%, respectively) and had the longest handling time (997 and 655 sec per event, respectively). No third-instar immature males, which were wrapped in thick tests constructed of wax filaments, were parasitized by the parasitoids. Anagyrus sp. nov. nr. sinope did not avoid superparasitism. Parasitoids foraging in patches of third-instar and adult females had a higher self-superparasitism rate (27–33%) than crawlers and second-instar nymphs (8–14%). The clutch sizes in the superparasitized mealybugs were slightly larger than those in the mealybugs parasitized only once, but the difference was only significant in the ovipositing female P. madeirensis. Older and larger mealybugs exhibited more vigorous defensive behaviors by walking away and flipping abdomens. However, such behavioral defenses were not effective against the persistent parasitoids.

Population structure, distribution and abundance patterns of the patagonian smoothhound Mustelus schmitti Springer, 1939 (Chondrichthyes, Elasmobranchii, Triakidae) in the rio de La Plata and inner continental shelf , sw Atlantic ocean (34º30'-39º30'S)

A total number of 4824 Mustelus schmitti was sampled. Females ranged from 25 to 93 cm in spring and from 28 to 90 cm in summer. Males ranged from 34 to 82 and from 28 to 77 cm, respectively. Length composition of the population showed significant differences between spring and summer being females larger than males. Total length distribution did not show significant differences between cruises. Males density varied significantly between cruises while for the females no significant variation was observed. In the spring cruise, both sexes occurred at depths lower than 50 m. Females occurred in the whole area with adult occurrence only above 35°30'S. Mature males occurred throughout the area, immature males occurring in two trawls in Samborombón Bay. The summer cruise showed a discontinuous distribution of the species along the study area resulting in spatial segregation in two groups with immature females predominating in both of them.

Sexually mature and immature yearling male European ground squirrels: A comparison of behavioral and physiological parameters

Early puberty may increase lifetime reproductive success, but may also entail diverse costs. In male European ground squirrels ( Spermophilus citellus), age at sexual maturity varies among individuals. We compared sexually active and inactive yearling males under standardized conditions in outdoor enclosures. Non-reproductive yearling males hibernated significantly longer than mature males and emerged when the mating period had already started. Testosterone concentrations peaked in the precocious males during premating and mating, and were depressed in the non-reproductive individuals throughout the study period. Emergence body mass was similar in both groups, although sexually immature males were significantly heavier at the end of the active season. Additionally, non-reproductive yearlings grew faster than precocious individuals. Male–male aggression peaked during mating and the following 4 weeks. Intense aggressive interactions like chases and fights were mostly initiated by reproductive males and were directed towards mature competitors. Aggressive behavior in immature males was mainly expressed as spatial displacements. Non-agonistic interactions with females were only observed in sexually active males. Concentrations of fecal cortisol metabolites did not differ between the two male groups and were elevated in the second half of the active season. Leucocyte numbers were reduced during mating in mature males, whereas in immature animals, cell numbers did not change significantly. Our results indicate that early puberty in European ground squirrels involves lower growth rates, high intrasexual aggression, lower prehibernatory body mass, and probably worse immunological condition during mating.

Seeing red: morph-specific contest success and survival rates in a colour-polymorphic agamid lizard

Red coloration in multicoloured or polymorphic species has been associated with dominance in a number of case studies, including probability of winning in human sports. However, it is not clear at what stage during ontogeny the association between red and the probability of winning contests occurs (or being perceived as more threatening by a contradistinct rival), for example, at conception, early ontogeny or at maturation. We analysed such coloration effects in a polymorphic (red versus yellow) species of lizard, the Australian painted dragon, Ctenophorus pictus. Red males were more likely to win dyadic contests with yellow males when competing for receptive females. When contestants were repainted with a rival's colour, there was a more than 30-fold increase in contest duration. Furthermore, when we tested for red-enhanced contest success in immature males, red was still significantly associated with winning. Thus, the association between red coloration and dominance seems to be set long before a male is naturally involved in sexual contests and could be an innate response to aid facultative fight or submission decisions, particularly in young males. To assess in situ selective benefits of the polymorphism, we released males in polymorphic and monomorphic groups. Males from polymorphic groups survived better, implying that polymorphism among neighbouring territorial males in the wild results in selective benefits.

Dental structure of the Giant lantern shark Etmopterus baxteri (Chondrichthyes: Squaliformes) and its taxonomic implications

Dogfish sharks (Squaliformes) are a highly diverse group of neoselachians occurring in a wide range of marine environments and are common members of deep-sea faunas. The order Squaliformes comprises six families with approximately 98 extant species. The dentition of most squaliforms is characterized by a strong dignathic heterodonty and dental variation yielding a suite of potential tooth characters that could be used for taxonomic and systematic purposes. So far, no detailed study has been carried out to analyse the use of tooth morphologies in reconstructing the phylogeny of squaliforms. Also, the degree of characteristics of intraspecific variability of tooth morphologies is still unclear. Here, we analysed the dental differences between juveniles and adults and between the sexes of the Giant lantern shark, Etmopterus baxteri, and tested these dental characters for taxonomic purposes employing different statistical procedures. The results show that upper teeth of adult females and males differ morphologically in that those of females are bigger and display a lanceolate central cusp, whereas male specimens have thin and needle-like central cusps. Upper teeth of males have a higher number and a more pronounced variability of lateral cusplets than those of females. Moreover, an ontogenetic heterodonty might be developed in male specimens with sexually immature males displaying similar dental morphologies to those of adult females. Lower teeth, conversely, do not differ morphologically between the sexes. Results indicate that tooth morphologies of squaliform sharks bear high potential for phylogenetic purposes if tooth variations are considered, but have to be treated with care, if no variation is analysed.

ESTIMATING ANNUAL SURVIVAL IN SEXUALLY DIMORPHIC SPECIES FROM PROPORTIONS OF FIRST-YEAR BIRDS

We estimated the annual adult survival (S) of several species of temperate and tropical sexually dimorphic tanagers and manakins from the proportions of first-year and older individuals in museum collections. In the case of the sexually dimorphic species included here, young males through their first year resemble females and can be distinguished from older males. We assumed that the sex ratio among first-year birds is even and estimated the number of immature females (IF) in a sample as equal to the number of immature males (IM), using sex information on museum labels. The number of adult females (AF) is the total number of females (F) minus IF, and survival can be estimated by S = AF/F. We used a Monte Carlo resampling approach to estimate standard errors and 1% and 99% confidence limits on S for samples of size N, based on 1000 sets of N randomly drawn individuals and observed proportions of the F, IM, and AM classes. Estimates of annual survival (S) were 0.60-0.73 in four North American species of Piranga tanagers and 0.50 and 0.62 in two montane Central American species. Values of S in lowland species of Habia and Ramphocelus tanagers ranged between 0.68 and 0.82. Annual survival in Pipra manakins was 0.53-0.68, and values for two Manacus species were 0.69 and 0.70. Where estimates of apparent survival (phi) from capture-recapture studies were available, the two methods produced correlated results with a tendency for phi < S. Among tanagers, only Ramphocelus dimidiatus (0.82) and Piranga bidentata (0.50) stood out from the other species, for which S averaged 0.66 +/- 0.05 (SD). Annual survival rates of temperate and tropical species overlapped broadly in this analysis, reinforcing the conclusion that distinctive life-history traits of temperate vs. tropical species cannot be explained completely by the adjustment of reproductive investment in relation to adult survival and the expectation of future life.

Olfactory sensitivity to conspecific bile fluid and skin mucus in the European eel Anguilla anguilla (L.)

The present study assessed the olfactory potency of conspecific bile fluid and skin mucus in the European eel Anguilla anguilla by the electro‐olfactogram. Immature males showed high olfactory sensitivity to conspecific bile, giving large amplitude responses in a concentration‐dependent manner with estimated thresholds of detection of &lt;1:107 (n= 6). Mucus also proved to contain highly potent odorants with thresholds of detection of c. 1:106 (n= 6). Crude solid‐phase extraction of bile fluid (C‐18 and C‐2/ENV+ cartridges) showed that the majority of olfactory activity in bile fluid was contained in the eluate of C‐18 cartridges (n= 6). There were quantitative differences, however, between the sexes; female bile fluid had a higher proportion of activity in this fraction. Similar solid‐phase extraction of mucus showed that it contains a higher proportion of odorants in the C‐18 filtrate than bile fluid. Mucus from mature eels, however, had a higher proportion of olfactory activity in the eluate than immature fish (n= 6). Cross‐adaptation experiments suggest that there are qualitative differences in the odorants contained in bile and mucus depending on both the sex and state of sexual maturation of the donor (n= 6). These results are consistent with a role for chemical communication in the reproduction of the European eel and suggest that both bile and mucus are potential sources of the odorants involved.

A Male Sex Pheromone in a Scorpionfly

It has been postulated that males of a number of scorpionfly species produce sex pheromones. This is based on the observation that females often respond only to conspecific males when they evert their genital pouch, the proposed site of pheromone release. In this study, we prove that in Panorpa germanica (Mecoptera, Panorpidae), the eversion of a male's genital pouch is associated with the release of a volatile sex pheromone. In dual choice situations, females showed a high preference for 'calling' (males with everted genital pouch) over noncalling individuals. Volatiles emitted by males and females were collected and identified by coupled gas chromatography-mass spectrometry. Two aldehydes [(2E,6Z)-nona-2,6-dienal and (E)-non-2-enal] were characteristic of calling males but not of noncalling or immature males or females. Bioassays with synthetic compounds confirmed that the identified substances are attractive to females. To the best of our knowledge, this is the first identification of a sex pheromone in scorpionflies.

Sex‐biased dispersal in western lowland gorillas (Gorilla gorilla gorilla)

We explored two hypotheses related to potential differences between sexes in dispersal behaviour in western lowland gorillas (Gorilla gorilla gorilla). Direct observations suggest that immature females have more opportunities to move between breeding groups than immature males. The distribution of kin dyadic relationships within and between groups does not, however, support this hypothesis. At larger geographical scales, dispersal is likely to be easier for males than females because of the solitary phase most blackbacks experience before founding their own breeding group. However, previous work indicates that males settle preferentially close to male kin. By specifically tracing female and male lineages with mitochondrial and Y-chromosomal genetic markers, we found that male gorillas in the 6000 km2 area we surveyed form a single population whereas females are restricted to the individual sites we sampled and do not freely move around this area. These differences are more correctly described as differences in dispersal distances, rather than differences in dispersal rates between sexes (both sexes emigrate from their natal group in this species). Differences in resource competition and dispersal costs between female and male gorillas are compatible with the observed pattern, but more work is needed to understand if these ultimate causes are responsible for sex-biased dispersal distances in western lowland gorillas.

In vivo and in vitro effects of Rhizopus extract on body growth and steroid production in masu salmon, Oncorhynchus masou Brevoort

This study investigated the in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU) in masu salmon Oncorhynchus masou Brevoort. Underyearling fish were fed with RU for 16 months. Monthly changes in body growth, gonadal maturation and serum levels of sex steroids were monitored. Gonads were also incubated at 0, 1, 10, 100 and 1000 μg RU mL−1 Leibovitz's L-15 medium for 18 h. The levels of steroids in serum and cultured medium were measured. It was determined that RU-fed immature and mature males, when compared with control groups, showed significantly higher body growth during spring, summer and the spawning period. Similarly, immature RU-fed females showed significantly higher fork length and body weight in autumn, spring and summer. Furthermore, RU-fed males showed significantly higher levels of serum testosterone (T) and 11-ketotestosterone (11-KT) levels in the pre-spawning season, and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) in the spawning season. In vitro RU incubation of gonads showed a dose-dependent and significant increase in T, 11-KT, oestradiol-17β and DHP release in the medium. It appears that the causes of enhanced body growth and increased steroid production herein observed in salmonids are the physiologically active substances that may be present in the mycelium of the fungus.