Age Dependence of the Level ofcopia Retrotransposon Expression in the Testes of Drosophila melanogaster

Expression of the lacZ reporter gene controlled by various deletion derivatives of the regulatory region of the copia retrotransposon was studied in the testes of adult transgenic males of the Drosophila melanogaster y ¹ w ^67c23(2) strain at the age of 3, 6–9, 12–15, 18–21, and 24–27 days. When the construct contained the full-length regulatory region, which included the 5-long terminal repeat (LTR) and the 5-untranslated region (UTR), expression was the lowest in males aged 12–15 days and the highest in males aged 3 or 24–27 days. A similar V-shaped age dependence was previously observed for the copia transposition rate and RNA content in a strain with a high rate of copia transposition. Thus, the V-shaped age dependence of expression, which is unusual for Drosophila, proved to be characteristic of copiaregardless of its transposition rate. Deletion of the 5 or 3 end of the LTR, but not of the UTR, changed the age dependence of the level of reporter gene expression. In this case, expression was the highest in 3-day-old males and gradually decreased with age, as typical for many Drosophila genes. It was assumed that the 5- and 3-terminal regions of the copiaLTR contain regulatory elements responsible for the V-shaped age dependence of expression, while the expression level depends to a greater extent on the regulatory elements of UTR.     

Diet and daily ration of male and female caridean shrimp<Emphasis Type="Italic"> Nauticaris marionis</Emphasis> at the Prince Edward Archipelago

The feeding dynamics of males and females of the sequential protandric shrimp Nauticaris marionis were investigated in late austral summer (April) 2002. Results of gut content analysis indicated that N. marionis is an opportunistic feeder preying on a variety of prey, with a preference for detritus, benthic amphipods and gastropods. Overall, pelagic prey made only an insignificant contribution to diet, and was only taken by males. Females of N. marionis exhibited cannibalism, particularly in incubation containers. There was no diel pattern in the feeding activity of N. marionis. In-situ daily rations of males (carapace length <7 mm) and females (>7 mm) were equivalent to 10% and 5% of body dry weight, respectively.An erratum to this article can be found at     

Aspects of Reproductive Biology of the Scalloped Hammerhead Shark, Sphyrna Lewini, off Northeastern Brazil

Ninety four scalloped hammerhead sharks, Sphyrna lewini (53 females and 41 males) ranging in size from 121 to 321cm total length (TL), were collected from surface gillnetters operating off northeastern Brazil and throughout the southwestern equatorial Atlantic Ocean between January and December 1996. A common regression for TL and eviscerated weight (EW) was calculated as, logEW = –11.786 + 2.889 logTL. Females and males were categorised into reproductive stages (4 and 2, respectively) according to morphological changes in their gonads. Size at sexual maturity for females was estimated to be 240cm, while males appeared to mature at between 180 and 200cm. Gravid females had between 2 and 21 embryos or pups, varying in TL from 3 to 38cm. There was no relationship between maternal length and size of litter. Copulation and parturition appear to occur outside the sampled area and possibly closer to the coast. With the exception of slightly lower uterine and ovarian fecundities, the results support the few existing data on the reproductive cycle of S. lewini in other areas.     

Impact of the Regulatory Regions of Retrotransposon copia on the Level of Its Expression in Testes of Drosophila melanogaster

Expression of the lacZ reporter gene under the control of five deletion derivatives of the copia regulatory region including the 5 long terminal repeat (LTR) and the 5 untranslated region (UTR) was assayed in the testes of transgenic Drosophila melanogaster males (larvae and imago). The full-length copia regulatory region (LTR + UTR) ensured expression of the reporter gene in testes of both larvae and adult males. Deletion of UTR or 3 end of LTR increased lacZ expression in the testes, whereas deletion of the 5 end of LTR increased it. This indicated that a positive regulator ofcopia expression is at the 5 end of LTR and that negative regulators are at the 3 end of LTR and in UTR. The effects of the fragments of the copia regulatory region on reporter gene expression in the testes in vivo did not completely coincide with the effects observed earlier in cultured cells. We suggest that this difference is due to different regulation of expression of the fusion constructs integrated into chromatin as compared to their transient expression.     

Life history of Gambusia holbrooki (Pisces, Poeciliidae) in the Ebro delta (NE Iberian peninsula)

We studied age, growth and reproduction of an introduced poeciliid, Gambusia holbrooki (Agassiz, 1859), in the Ebro delta marshes. Maximum ages observed were 2⁺ in females and 0⁺ in males. Growth commenced in March and continued until September. Females reached greater sizes, had a higher rate of growth and lived longer than males. The largest sizes found were 63 mm versus 32 mm . Multiple spawning occurred throughout the reproductive cycle (from May to September). The average brood size per female reached its maximum in July in the parental cohort (86 embryos/) and in August in the offspring cohort (29 embryos/). After reproduction the parental cohort decreased drastically. The relationship between fecundity (F) and total length (mm) was calculated for each month of the reproductive period. Sex-ratio deviated significantly from unity.Viviparity, several broods and large larvae provide G. holbrooki with several advantages over oviparous species. The capacity to adjust its life history to a particular environment could explain the life history differences between those in the Ebro delta and other populations.     

First Field Studies of an Endangered South African seahorse, Hippocampus capensis

South Africa's endemic Knysna seahorse, Hippocampus capensis Boulenger 1900, is a rare example of a marine fish listed as Endangered by the IUCN because of its limited range and habitat vulnerability. It is restricted to four estuaries on the southern coast of South Africa. This study reports on its biology in the Knysna and Swartvlei estuaries, both of which are experiencing heavy coastal development. We found that H. capensis was distributed heterogeneously throughout the Knysna Estuary, with a mean density of 0.0089m^–2 and an estimated total population of 89000 seahorses (95% confidence interval: 30000–148000). H. capensis was found most frequently in low density vegetation stands (20% cover) and grasping Zostera capensis. Seahorse density was not otherwise correlated with habitat type or depth. The size of the area in which any particular seahorse was resighted did not differ between males and females. Adult sex ratios were skewed in most transects, with more males than females, but were even on a 10 by 10m focal study grid. Only three juveniles were sighted during the study. Both sexes were reproductively active but no greeting or courtship behaviours were observed. Males on the focal study grid were longer than females, and had shorter heads and longer tails, but were similar in colouration and skin filamentation. The level of threat to H. capensis and our limited knowledge of its biology mean that further scientific study is urgently needed to assist in developing sound management practices.     

An inducible change in state on the chromosomes of Sciara: Its effects on the genetic components of the X

Normally in Sciara males the sex chromosome constitution of the soma (X ^m O) differs from that of the germ line (X ^m X ^p ), the single X being of maternal origin. Males which are patroclinous for their sex-linked genes (X ^p O) are found regularly among the progeny of females heterozygous for any one of a number of X-translocations (X X ^t ). The patroclinous males are almost invariably completely sterile. In the present study a comparison is made of the patroclinous males derived from 5 different X-translocations in S. coprophila. The study includes data on the morphology and sexual behavior of the males as well as the cytology of the testis from late 4th instar through pupal life. The study is oriented towards the basic question of whether the paternally-derived X — normally destined to be eliminated — can function properly when it is retained. The comparative study supports our original suggestion that the patroclinous males arise from no-X eggs following 31 disjunction during oogenesis.Dedicated to Professor J. Seiler on the occasion of his 80th birthday.The studies reported here were supported by the National Science Foundation, grants GB-42 and GB 2857, and in part by Contract No. AT-(40-1)-2690 under the Division of Biology and Medicine, U. S. Atomic Energy Commission.     

Genetic regulation of glucose 6-phosphate dehydrogenase activity in Drosophila melanogaster

Studies on two variants of X-linked enzyme, G6PD, in several inbred and outbred strains of Drosophila melanogaster suggest that (1) there is dosage compensation at this locus; (2) males have 20–33% more activity than females, due to enzyme-deficient eggs in the latter; (3) outcrossing Drosophila strains results in a significant rise in G6PD specific activity in such a way as to suggest the presence of two or more nonlinked loci specific in their effect on G6PD activity (the effect is twice as great in males as it is in females); (4) there is less A enzyme than B enzyme activity/mg protein in males, but they are equal in females; (5) the presence or absence of X-linked regulators for G6PD could not be ascertained.Aided by National Institutes of Health grants HD 00004, HD00486, and GM 14155.     

Genetics,ontogeny, and testosterone inducibility of aldehyde oxidase isozymes in the mouse: Evidence for two genetic loci (Aox-1 and Aox-2) closely linked on chromosome 1

Null-activity and low-activity variants for the liver supernatant isozymes of aldehyde oxidase (designated AOX-1 and AOX-2) were observed in inbred strains and in Harwell linkage testing stocks of Mus musculus. The genetic loci determining the activity of these isozymes (designated Aox-1 and Aox-2, respectively) are closely linked on chromosome 1 near Id-1 (encoding the soluble isozyme of isocitrate dehydrogenase). Linkage data of Aox-1 with Id-1 and Dip-1 (encoding a kidney peptidase) demonstrated that this gene coincides with or is closely linked to Aox (Watson et al., 1972). Ontogenetic analyses demonstrated that liver AOX-1 appeared just before birth and increased in activity during postnatal development, whereas liver AOX-2 was observed only during postnatal development. Adult male livers exhibited higher AOX-1 and AOX-2 activities than adult female livers. Both isozymes were significantly reduced in activity by castration of adult males and increased following testosterone administration to castrated males and normal female mice.     

Hormone-induced vocal behavior and midbrain auditory sensitivity in the green treefrog,Hyla cinerea

Summary Twenty four castrated male, 6 intact male, and 11 intact female Hyla cinerea were injected subcutaneously with 25 g arginine-vasotocin (AVT) and induced to call 1 h later in response to the playback of a conspecific mating call. Eighteen castrated males and 8 intact females were implanted 5 mg androgen pellets for 3 weeks prior to the neuropeptide injection. Among castrated males, 6/9 testosterone (T) implanted, 4/9 dihydrotestosterone (DHT) implanted and 2/6 non implanted individuals produced calls after being administered AVT. 5/6 intact non implanted males and 6/8 T intact implanted females also called, and 3 intact non implanted females remained silent after the injection. Evoked calls had a mid-frequency spectral peak at about 1900 Hz which is absent in field-recorded mating calls of this species. Calls of implanted females and castrated non implanted males were shorter than those of castrated implanted and intact non implanted males. Audiograms measured before hormone implants showed dips of enhanced sensitivity at about 0.5, 0.9 and 3.0 kHz in males and females. After AVT injection, thresholds at frequencies within the 0.7–1.5 kHz range were increased in castrated males. Such reduction in sensitivity points to an inhibition of the auditory system during hormone induced vocal activation.Abbreviations AVT arginine-vasotocin - DHT dihydrotestosterone - T testosterone - TS torus semicircularis     

Feeding Behavior, Habitat Use, and Abundance of the Angelfish Holacanthus passer (Pomacanthidae) in the Southern Sea of Cortés

Feeding behavior and habitat use of the king angelfish, Holacanthus passer, was studied in the southern Sea of Cortés, México. H. passer fed on benthic communities (algae and sessile invertebrates) and in the water column (mainly feces from the damselfish Chromis atrilobata). Although there were not significant differences in feeding rate between sexes, coprophagy was more common in males, while grazing was more common in females. Spatial distribution of size classes followed a pattern of decreasing size with increasing depth. Feeding rate was significantly different among habitats: small females had a higher feeding rate on the bottom, big females and small males had similar feeding rates from the bottom to 3m above the bottom, and big males had higher feeding rates from 5m above the bottom to the surface. Habitat was clearly partitioned, and there was significant habitat overlap only between big females and small males. The abundance of H. passer was partly explained (34% of the total variance) by the abundance of the damselfish C. atrilobata. There was a clear trophic association between C. atrilobata schools and H. passer feeding damselfish feces in the water column. The sex ratio male:female of H. passer populations was >1 at several sites, an unusual pattern for a protogynous fish. The sex ratio on the H. passer water column stock was also biased towards males at most sites. Although there is a positive relationship between C. atrilobata abundance and H. passer, there are factors other than damselfish abundance which cause this dominance of males.     

Sexual selection at varying population densities in male field crickets,Gryllus veletis andG. pennsylvanicus

Male field crickets call and attract females or they silently search for females in the vicinity of calling males. At high population densities, fewer calling sites are available, defense of calling sites is costly, and an increased proportion of matings should result from searching behavior. To test these predictions, individually marked field crickets, Gryllus veletisand G. pennsylvanicus,were observed for 10 h nightly in large outdoor arenas at relatively high and low densities (2020 and 55, males and females). Data were gathered on body weight, calling duration, movement, and mating frequency for individual crickets. These observations showed that variance in male mating success was significantly greater at a low density in G. pennsylvanicus,and calling duration correlated with mating success at this density. Direct selection on a trait was estimated as the partial regression coefficient (selection gradient, ) and the total selection was estimated (direct and indirect selection on correlated traits) as the covariance (standardized intensity of selection, s) of the trait on the relative mating success. Direct selection favored increased movement at a high density in G. veletis,and direct and total selection favored increased calling duration at a low density in G. pennsylvanicus.Most other comparisons were not statistically significant. The data are discussed in terms of density-dependent fluctuations in sexual selection on correlated male traits.     

Sex chromosome pairing patterns in male mice of novel Sxr genotypes

The influence of the sex-reversal factor (Sxr) on X and Y chromosome pairing was examined by comparing males with novel and standard Sxr genotypes. The novel Sxr males were exceptional in carrying Sxr on their X rather than their Y chromosome, or homozygously on both their X and Y chromosomes, or on a Y chromosome of different origin to that on which the factor arose. Regardless of its chromosomal location, Sxr was found to elevate the frequency of X-Y separation. Univalent X and Y chromosomes were observed to undergo self-association in a variable proportion of spermatocytes of all Sxr-carrying males. There was a suggestion that chromosomal location of the factor could influence the frequency of univalent self-association. Our observations do not support the published hypothesis of Y self-pairing as the cause of the elevated rate of X-Y separation at pachytene in Sxr-carrying males. Rather, they suggest that heterozygosity due to the presence of Sxr in the XY pairing region may be sufficient to disrupt pairing and cause univalence, or alternatively, that Sxr is an inefficient promoter of X-Y pairing initiation.     

The consistency of quantitative genetic estimates in field and laboratory in the yellow dung fly

How consistent quantitative genetic estimates are across environments is unclear and under discussion. Heritability (h ²) estimates of hind tibia length (body size), development time and diapause induction in the yellow dung fly, Scathophaga stercoraria, generated with various methods in various environments are reported and compared. Estimates varied considerably within and among studies, but yielded good overall averages. The genetic correlations between the sexes for body size and development time were expectedly high (r(sex)=0.57–0.78) but clearly less than unity, implying independent evolution of both traits in males and females of this sexually dimorphic species. Genetic and environmental variance components increased in proportion at variable field relative to constant laboratory conditions, resulting in overall similar h ². Heritabilities for males and females were also similar, and h ² of the morphological trait hind tibia length was not necessarily greater than that of the two life history traits. Full-sib (broad-sense) estimates (h ²=0.7–1.1) were 2–3 times greater than half-sib and parent/offspring (narrow-sense) estimates (h ²=0–0.6). Common environment (i.e., among-container) variance averaged 38.3% (body size) and 16.8% (development time) of the broad-sense genetic variance in two laboratory studies. The broad-sense h ², therefore, may contain substantial amounts (12–50%) of dominance variance and/or variance due to maternal effects. A general conclusion emerging from this and similar studies appears to be that whether field and laboratory genetic estimates differ depends on the environment, trait and species under consideration.     

Experimentally elevated testosterone increases status signalling in male Greylag geese (<Emphasis Type="Italic">Anser anser</Emphasis>)

Testosterone modulates male vertebrates sexual and social behaviour. We experimentally investigated the testosterone-sensitive behaviours in male greylag geese (Anser anser) by implanting silastic tubes containing crystalline testosterone during the mating season (February; 5 implanted and 5 control males) and in the early winter (November; 7 and 7). Focal animals were part of a semi-tame, unrestrained flock with fully intact social relationships. Excreted testosterone and corticosterone immunoreactive metabolites (TM, BM) were determined by enzyme immunoassay. Individual faecal samples and behavioural protocols were collected daily over a period of 5 weeks, including 1 control week before implantation. In February, no significant behavioural effects of the supplemental testosterone were observed, which may be due to the naturally occurring high systemic androgen levels in spring. In November, however, implanted males had higher TM excretion rates and performed status signalling behaviour (beak up) more frequently than control males. No differences between implanted and control males were found with respect to BM, agonistic interactions or vigilance behaviour. Furthermore, during the second week after implantation, TM positively correlated with the frequency of beak up of implanted males, whilst their female partners were attacked with lower latency by other members of the flock than the females of control males. Hence, status signalling in greylag ganders seems to be testosterone-sensitive year-long and inappropriate status signalling of males may draw attacks towards their females.     

Morphological aspects of the hypothalamic-hypophyseal system

Summary Enzyme-histochemical methods were used to study the metabolic activity of specialized ependyma of the ventrolateral walls and floor of the third ventricle in young male and female rats during the critical period of sexual differentiation of the hypothalamus (one week after birth). Histochemical tests were conducted for glutamic dehydrogenase, lactic dehydrogenase, glucose-6-phosphate dehydrogenase, glycerophosphate dehydrogenase and NADH₂-dehydrogenase. Enzyme activity was judged by cytospectrophotometry. All the data were treated statistically.It was found that the specialized ependyma of the ventrolateral wall and floor of the third ventricle (median eminence) in rats differed in their enzyme behaviour in males and females during the critical period of sexual differentiation of the hypothalamus. At the level of the arcuate nucleus ( ²-tanycytes) and the medial part of the median eminence ( ²-tanycytes) the ependyma was characterized by similar indices of metabolic activity in males and females in the decisive terms of the critical period (days 3, 5, and 7). On day 5 metabolic activity of these cells was reduced both in the males and in the females. Prominent sexual differences in the intensity of the enzyme reactions studied were noted in the ependyma of the lateral parts of the median eminence ( ¹-tanycytes) in the critical period. On day 5 metabolic activity of ¹-tanycytes was reduced in males and increased in females. It is suggested that these differences are caused by the receptor nature of ¹-tanycytes and suggest their implication in the mechanisms of sexual differentiation of the hypothalamus.     

Sperm dysfunction in sex ratio males of Drosophila subobscura

Drosophila subobscura has 128 spermatids per cyst, enclosed by two cyst cells. At beginning of elongation in control males the spermatid nuclei surround the head cyst cell nucleus, in sex ratio males nuclei are found throughout the cyst. Spermatid nuclei can elongate in any position in the cyst. Nuclei can be eliminated during individualization or degenerate after individualization. The number of sperm in any wrong position in the cyst varies in control males from 0 to about ten, in sex ratio males from 0 to more than 50. Two cyst sizes are distinguishable. At beginning of elongation small cysts have homogeneously stained spherical nuclei which later on are rod like. Large cysts have granulated nuclei which at first become spindle shaped and then slender. The length of the DNA containing part of elongated sperm heads of the long class is about 33 m in sex ratio and control males. The small sperm heads are 15 m in sex ratio but 20 m in control males. The complete DNA-containing-sperm-length is about 10% less in short sperm and 5% less in long sperm of sex ratio males than in those of control. Sex ratio males have more cysts per testis than control males. In sex ratio we counted 53.8%, in control males 49.4% short cysts.The work was supported by the grants N.S.F. GB-43209 and NIH GM 21732 and the Schweizerischer Nationalfonds zur Foerderung der wissenschaftlichen Forschung grant Nr. 3.815.72.     

Further studies on the regulation of the Harderian glands of golden hamsters by the thyroid gland

Summary Long-term increased or decreased circulating levels of thyroid hormones significantly modify porphyrin concentrations and morphology in the Harderian glands of male and female hamsters. Administration of T₃ reduced porphyrin concentrations in females; this treatment or decreasing thyroid hormone levels with KClO₄ suppressed the post-castration rise of porphyrins in males. Hypophysectomy led to increased porphyrins in the Harderian glands of males; this rise was suppressed in hypophysectomized males by T₃ or T₄. In females, hypophysectomy reduced porphyrins which were further reduced by daily administration of T₃ or T₄. These modifications in the normal females were identical in castrated males. Mitotic activity in the Harderian glands of females was stimulated by KClO₄ and by hypophysectomy with or without exogenous T₃. In males, castration increased mitotic activity which was suppressed by T₃ and exacerbated by KClO₄. Increased mitotic activity seemingly follows loss of tissue mass. The data show that thyroid hormones act directly on the Harderian glands rather than indirectly through modification of TSH synthesis/release. Female type glands in males are a consequence of loss of gonadal androgens by castration, or by suppression or loss of thyroid hormones by hypophysectomy or by treatment with KClO₄. However, male type glands in females are the result of androgen treatment, and/or increased levels of thyroid hormones via reduced ambient temperatures or of photic input. We conclude that regulation of the Harderian gland appears to be different in the two sexes.Abbreviations T ₃ Triiodothyronine - T ₄ Thyroxine - TSH Thyroid Stimulating Hormone - KClO ₄ Potassium Perchlorate - h hours - ml milliliter - mg milligram - g gram - male - female - castrated male - AP hypophysectomized - CON Control - ALA delta aminole-vulenic acid - HG Harderian Gland     

The influence of horn and body size on the reproductive behavior of the horned rainbow scarab beetlePhanaeus difformis (Coleoptera: scarabaeidae)

The reproductive behavior of horned rainbow scarab beetles,Phanaeus difformis, was studied to determine the influence of morphological traits on intersexual and intrasexual interactions.Phanaeus difformis is a sexually dimorphic dung beetle in which males possess much larger horns than females, and males can be grouped into major and minor male morph categories based on horn size. Male-female pairs cooperated in nest construction and provisioning. In the laboratory, males of both morphs assisted females and were equally successful at copulating. However, in the field larger individuals had a pairing advantage due to greater success in intrasexual competition. Some males used an alternative mating tactic which involved sneaking copulations with paired females. In most cases the sneak male was smaller than the paired male.