Diapause in the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent for tamarisk (Tamarix spp.)

The tamarisk leaf beetle, Diorhabda elongata Brullé deserticola Chen, was collected in northwestern China and has been released in the western United States to control tamarisk (Tamarix spp.). Characteristics of diapause and reproductive development in D. elongata were examined to improve management as a biocontrol agent. Under long days, 16:8 (L:D) h, males began to emit aggregation pheromone within 2-3 d of adult emergence, mating occurred, and females oviposited within 7 d of adult emergence. Under short days, 12:12 (L:D) h, males did not emit pheromone, mating did not occur, and both males and females entered reproductive diapause marked by inconspicuous gonads and hypertrophied fat body. Ovaries of diapausing females lacked vitellogenic oocytes, and the ovarioles were clear and narrow, whereas reproductive females had enlarged ovaries with two to three yellow oocytes per ovariole. Diapausing males had thin, transparent accessory glands and ejaculatory ducts, whereas reproductive males had thick white accessory glands and white opaque ejaculatory ducts. Sensitivity to diapause-inducing photoperiods extended into the adult stage. Reproductive females ceased oviposition, resorbed oocytes, and entered diapause when switched from long to short days. Diapause-destined insects ceased feeding and entered the leaf litter 10-20 d after adult emergence, whereas reproductive insects remained on the plants and fed for at least 30 d. Reproductive insects exhibited dispersal behaviors, such as attempted flights, whereas diapause-destined insects did not show dispersal behaviors. Information gained from these studies will be used to better manage populations in the field and to improve rearing and storage in the laboratory.     

EXPERIMENTAL DEMONSTRATION OF A POST-NUPTIAL REFRACTORY PERIOD IN THE TURTLE DOVE STREPTOPELIA TURTUR

Turtle Doves Streptopeliu turtur are shown to possess a typical post-nuptial period of pituitary refractoriness; during this time the neuro-endocrine apparatus is unresponsive to daylengths which at other seasons would result in gonad recrudescence. Males and females were collected in late summer when their gonads were regressing. Subjects were then held for 2.5 months on either 8-hour or 17-hour photoperiods by the end of which time their gonads had become uniformly fully regressed and inactive. All males were then given 3–5 months and females six months of exposure to 17-hour photoperiods. Only the gonads of subjects pretreated with short days responded with gametogenesis. All subjects (males and females) were moulting when caught and in addition had laid down heavy deposits of migratory fat by the half-way stage of the experiment. However, further moulting and feather growth was inhibited in those birds kept throughout on long summer days and their fat deposits were maintained. In contrast, treatment with a period of short days enabled the subsequent completion of moult and new feather growth and the loss of migratory fat coincident with gonad development. The results contrast with those obtained in previous experiments (Lofts, Murton & Westwood 1967) with the Woodpigeon, which lacks a refractory period. The reasons for the inter-specific differences are discussed and some endocrinological implications of the results considered.     

Historical aspects of protandrous sex change in the anemonefish Amphiprion melanopus (Pomacentridae, Teleostei)

Gonadal structure and cellular composition were examined in juveniles, males and females of the protandric hermaphrodite, Amphiprion melanopus. Functional sex change was experimentally induced in the field and gonad structure was histologically examined both qualitatively and quantitatively at 10, 20, 30 and 45 days after its initiation. Juvenile gonads consist primarily of immature ovarian tissue. Functional male gonads are ovotestes with co-existing mature spermatogenic tissue and immature ovarian tissue, while females possess only ovarian tissue. The initiation of sex change is marked by a rapid maturation of spermatogenic tissue and proliferation of putative oogonia. Gonads were essentially female by 20 days into sex change, but evidence of mature female function (marked by the initiation of vitellogenesis) was not observed until 45 days. Considerable variation between individuals was seen in quantitative measures of gonadal change in the early stages of sex change, but not in later stages. Progress in sex change as indicated by histological indicators was, however, consistent within stages. Duet systems for gamete transport changed from the male to the female form after all male tissue had been replaced.     

中国大鲵生殖腺胚后发育的形态学观察

为探寻中国大鲵(Andrias davidianus)生殖腺胚后发育的特点及规律,采用解剖学与组织学技术对其形态结构变化进行了观察.结果表明,大鲵的原始生殖腺开始出现于出膜28～49 d;出膜133～175 d时一些个体生殖腺内已初步分化出原始卵泡;出膜259 ～343 d时一些个体生殖腺内已初步分化出生精小叶;出膜427 d时,卵巢已明显分化为皮质与髓质,且髓质内出现了卵巢腔,精巢内生精小叶及其内的腔隙、精巢间质等分化已较为明显;出膜511 d时精巢分化为明显的生精小叶和非成熟小叶两个区域.本文认为,大鲵与其他无羊膜类原始生殖腺的分化一般发生在胚后阶段,而且雌性的分化时间早于雄性.     

Biology of the amphioxus,Branchiostoma belcheri in the Ariake Sea,Japan II. Reproduction

We investigated the reproduction of the amphioxus Branchiostoma belcheri in the southern Ariake Sea, Japan, from 1999 to 2002. Gonads were very small or almost absent from September to December and began to develop in January. Changes in the gonad length index indicated that spawning began in mid June, after the gonads had attained maximum size. Although most gametes were extruded during the first spawning, some remained in the gonads. Shrunken gonads were much smaller but contained gametes, and the second spawning occurred around 10 July. It was unclear whether all adults spawned twice, but a large proportion of individuals did. After the first spawning, both males and females lost 30% of their body weight. Most one-year-old individuals did not spawn, and the minimum size at maturity was ca. 20 mm. We found no termination of reproduction among very large individuals. The average number of gonads was significantly larger on the right side of the body (26.2 in males and 26.1 in females) than on the left side (24.0 in males and 23.5 in females). We found two hermaphrodites in a total of 11,184 specimens examined. Each had four or three ovaries among a total of 45 or 54 gonads.     

Juvenile body weight and gonad development in a diallel cross among lines of Japanese quail (Coturnix coturnix japonica)

Summary The influence of growth on the extent of heterosis for juvenile body weight and gonad development was studied in a diallel cross among two lines of Japanese quail differing in adult body size. A total of 1,096 birds (563 males and 533 females) was slaughtered between 25 and 49 days of age. Reciprocal cross differences were non-significant. Heterosis showed a curvilinear course with age peaking during early growth (body weight) and during sexual maturity (gonad percentage). Overall advanced physiological development of the crossbreds probably begins as early as during the embryonic stages and results in earlier sexual maturity. In females, heterosis for percentage gonads was biased strongly by the presence of a hard-shelled egg in the uterus.     

Sex differentiation and pubertal development of gonads in the viviparous mosquitofish, Gambusia affinis

The ontogenetic development of gonads from embryo to adult was observed histologically in the viviparous teleost, Gambusia affinis. Primordial germ cells (PGCs) appeared in the subendodermal space of the embryo 14 days before birth, and then transferred to the dorsal mesentery to form paired genital ridges 12 days before birth. The PGCs proliferated in the genital ridge, forming gonadal primordia 10 days before birth. All gonadal primordia differentiated to the ovary containing oocytes 2 days before birth, but then redifferentiated to the ovary and testis just after birth. This indicates that the mosquitofish is a juvenile hermaphroditic species. The characteristics of gonadal sex differentiation just after birth were enlargement of the oocytes in females, and invasion of somatic cells from the hilar region to an inner portion of the gonad in males. The paired ovary fused at the basal area 5 days after birth, then on the ventral and dorsal portions, developing into a single ovary 10 days after birth. During this time a single ovarian cavity was formed on the dorsal portion of the ovary. The paired testes fused only at the basal area and became a single testis having two main lobes 10 days after birth. The oocytes gradually developed and began vitellogenesis 100 days after birth, but did not reach maturation until 110 days after birth. Spermatogenic cells formed cysts at 20 days, began meiosis at 70 days, and matured to form sperm balls 90 days after birth. The male fish sexually matured earlier than the female.     

The autecology of the chub, Squalius cephalus (L.), of the River Lugg and the Afon Llynfi

(1) The pattern of absolute atid relative gonad growth during the life-span and the seasonal gotiad cycle were determined from monthly samples of chub taken from two tributaries of the Herefordshire Wye. (2) A marked change in the pattern of absolute gonad growth was thought to indicate the attainment of sexual maturity. This was found to occur synchronously with corresponding changes in the pattern of body growth described previously and was in agreement with the age at which a seasonal gonad cycle was detectable. (3) Sexual maturity was attained during the eighth year of life (7+) in female chub and in males from the Afon Llynfi, but most males from the River Lugg matured a year earlier. (4) The chub gonads continued to increase in relative size after the attainment of sexual maturity. This was more evident in female chub. (5) Seasonal changes in the gonad condition and weight were followed. Gonad maturation occurred during spring and the gonad mass increased rapidly just prior to spawning. (6) Spawning occurred during June.     

长颚斗蟋长翅和短翅型雄成虫营养物质的积累与分配差异

[目的]翅多型雄虫在繁殖方面的能量投入与雌虫相异,这种差异可能会导致雄虫飞行与繁殖权衡的生理机制发生改变.因此,本研究旨在探究翅二型长颚斗蟋Velarifictorus aspersus雄成虫在营养物质积累与分配方面是否存在飞行与繁殖的权衡关系.[方法]选取长颚斗蟋V.aspersus头幅相近的长翅和短翅型雄成虫,对羽...     

Evaluation of estrogenic effects of municipal effluents to the freshwater mussel Elliptio complanata

Municipal effluents are an important source of estrogens to the aquatic environment. The purpose of this study was to examine the estrogenicity of municipal effluents to the indigenous freshwater mussel, Elliptio complanata. First, estradiol-binding sites in gonad homogenates were characterized to determine the binding affinity and specificity of estrogens. Mussels were exposed to increasing concentrations of a municipal effluent for 96 h at 15 degrees C. In another experiment, mussels were placed in cages and submerged for 62 days at 1.5 km upstream and 5 km downstream of a municipal effluent plume in the St. Lawrence River. Mussels were harvested for assessment of vitellogenin-like proteins in the hemolymph and determination of total lipid, carbohydrate and protein in the gonad. The presence of specific estrogen-binding sites was found in both male and female gonads. Binding of estradiol to cytosol proteins reached saturation, yielding a dissociation constant of 0.4 nM. Vitellogenin (Vg) levels increased significantly in both the hemolymph and the gonad after exposure to the effluent. Moreover, females appeared to be more sensitive than males to producing Vg. Mussels exposed in situ to contaminated surface waters had higher levels of Vg at the downstream site, again, females had higher levels of Vg than did males. On the other hand, lipid and sugar levels in male gonads were significantly increased at the downstream site. Moreover, mussels at the downstream site had decreased shell growth length and increased total and soft tissue weights. We conclude that municipal effluents contain bio-available xenoestrogens at levels sufficient to elicit effects in freshwater mussels.     

Reproductive cycle and reproductive output of the sea urchin Loxechinus albus (Echinodermata: Echinoidea) from Beagle Channel, Tierra del Fuego, Argentina

Reproductive cycle, frequency and duration of spawning, energetic content of gonads, and reproductive output of the common green sea urchin Loxechinus albus were analyzed in the Beagle Channel (Tierra del Fuego) between May 2004 and May 2005. Gonad indices (GI, percentages of gonad mass in total body mass) were significantly higher in March, April, July, and August than in November and May, thus showing a negative correlation with the photoperiod. Highest GI values of mature individuals were observed in August, and spawning occurred from September to December. In females, the mass-specific energy content of gonads (ECG) was highest in spawned gonads and lowest in mature ones, while in males ECG values were higher in immature stage and lower in premature and mature stages. High ECG values can be explained by the abundance of nutritive phagocytes. Both ECG and total gonad energy content (TECG) were higher in females than in males. Mean reproductive output was 7.28% for females and 6.15% for males (expressed as the difference between mean GI of mature and spawned gonads) and 25.02 kJ for females and 19.26 kJ for males (expressed as the difference between mean TECG of mature and spawned gonads).     

Metal (Fe, Zn, Mn and Cu) levels in the Antarctic fish Notothenia coriiceps

During the 1994/1995 Antarctic summer 20 Antarctic cod (Notothenia coriiceps) of both sexes were collected at King George Island, South Shetland Islands, Antarctica, to determine the levels of Fe, Zn, Mn and Cu in muscle, liver, gonad and kidney. Metal levels were assessed using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) technique. The levels of Fe, Zn, Mn and Cu observed in both sexes of N. coriiceps were significantly lower in muscle tissue than in liver, kidney and gonad; the livers of males and gonads of females had the highest levels. The differences between the sexes were significant for Zn and Mn in gonads and for Cu in liver. Despite the modest size-range of the specimens, the Cu levels in liver, muscle and kidney were significantly inversely correlated with female mass (P < 0.05) as was gonad Cu level and male body length. Fe mainly presented the highest concentrations and Cu and Mn the lowest ones. Mean muscle metal levels are similar to those of hake, cod, herring and mackerel; however, the level of Fe was slightly higher. Accumulation may occur for Fe, Zn and Mn in liver, kidney and gonad, which have higher levels than those of most prey. Received: 21 October 1997 / Accepted: 1 February 1998     

Quantitative studies on the reproduction of black scallop,Chlamys varia (L.) from lanveoc area (Bay of Brest)

The values of gonad index calculated by the allometric relationships of dry gonad weight over dry body weight of the black scallop, Chlamys varia (L.), gave peak values for May and September during 1976 and 1977. Histological studies on gonads from natural populations and periodic biopsies of gonads from marked animals in experimental cages showed that, in addition to intermittent spawnings between May and September, two peak spawning periods were noteworthy. These were a partial spawning in May–June and a complete spawning in September–October. The energy spent as gametes for these two spawnings has been calculated for individual males and females in each age group of the population and the cost of spawning by the whole population has been estimated. The population spent more energy for spawning in 1977 (144.49 kcal/100 m²) than in 1976 (83.70 kcal/100 m²) and the reproductive effort of an average adult was 0.04 in 1976 and 0.10 in 1977.     

Effects of octylphenol and 17beta-estradiol on the gonads of guppies (Poecilia reticulata) exposed as adults via the water or as embryos via the mother

Endocrine disrupting alkylphenolic compounds have been found in the aquatic environment, and concern has arisen over the ability of these compounds to affect the reproductive system of fish. In this study, the effects of exposure to an environmentally relevant concentration of octylphenol or 17beta-estradiol on the gonad structure of fish were examined. Viviparous guppies (Poecilia reticulata) were exposed as adults via the water or as embryos via the mother to 26 microg/l octylphenol or 0.85 microg/l 17beta-estradiol (mean measured water concentrations). Histological examinations revealed effects of the exposures on the gonads of the fish exposed as adults. Indications of blocked spermatogonial mitosis were seen in the testis structure of adult males after exposure to octylphenol or 17beta-estradiol. The post-parturition ovaries of adult females exposed to 17beta-estradiol showed effects suggesting an inhibited yolk deposition. At the tested concentrations, exposure to octylphenol or 17beta-estradiol via the mother fish did not significantly affect the weight, length, gonopodium index or sex distribution of the offspring. However, histology revealed effects on the liver structure, suggesting some effect of maternal exposure to octylphenol or 17beta-estradiol. These findings indicate that although octylphenol and 17beta-estradiol affect the gonad structure of adult male and female guppies, these substances have no significant effects on the sexual differentiation of the embryos at the tested concentrations.     

Juvenile bisexuality in the red sea bream,Pagrus major

The histology of the gonad of the red sea bream,Pagrus major, was examined in order to study the early gonadal development, sexual maturation and sex ratio in a natural population. A total of 1,117 fish between the ages of 4 months and 8 years were examined. Gonads of 4-month-old fish were either sexually undifferentiated with a central cavity, or ovarian in form. Gonads of 12- and 18-month-old fish were ovaries or bisexual gonads, while those of 2-year-old fish were ovaries, bisexual gonads or testes. Fish aged between 3 and 8 years had ovaries or testes, except for a few bisexual gonads found in 3- and 4-year-old fish. The chronological appearance of females, hermaphrodites and males in that order, and histological evidence, suggested that the testis originates from the ovary via a bisexual gonad in the juvenile stage. The sex ratio of females to males at the age of 2 years and over was about 1:1, suggesting that hermaphroditic red sea bream appear in about 50% of the juvenile population. The sexual pattern in this species, therefore, is concluded to be gonochorism with a bisexual juvenile stage.     

Alternative male mating tactics of the substrate brooding cichlid Telmatochromis temporalis in Lake Tanganyika

Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against conspecific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.     

P450 aromatase expression in the temperature-sensitive sexual differentiation of salamander (Hynobius retardatus) gonads

Sex differentiation of gonads in amphibians is believed to be controlled genetically, but altered epigenetically or environmentally. When larvae of the salamander Hynobius retardatus were reared at defined temperatures from hatching to metamorphic stages, a high temperature (28 degrees C) induced exclusively female gonads (ovaries), whereas intermediate (20 and 23 degrees C) or lower (16 degrees C) temperatures produced a 1:1 sex ratio of the morphological gonads. The thermosensitive period was determined to be restricted from 15 to 30 days after hatching, just before or when sexual differentiation occurred. Hynobius P450 aromatase (P450arom) cDNA was isolated from adult gonads and the partial nucleotide or deduced amino acid sequences were determined, showing a high level of identity with various vertebrate species. The P450arom gene was expressed predominantly in the adult ovary and brain, weakly in testis, but not in other somatic organs. A typical sexual dimorphism in P450arom expression was detected in normally developing larvae by a quantitative competitive RT-PCR; strong expression in the female gonads but very weak in male gonads. The dimorphism was detected much earlier than the morphological sexual differentiation of the gonads. When larvae were reared at the female-producing temperature (28 degrees C), strong expression was detected in all the temperature-treated larvae, suggesting that P450arom was up-regulated, even in genetic males. Our results confirm the importance of the P450arom regulation in the sexual differentiation of gonads and demonstrate that an up-regulation of P450arom is involved in the process of temperature-sensitive sex reversal in this species.