首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 154 毫秒
1.
The introduced macroalga Sargassum muticum (Yendo) Fensholt is currently observed along the coasts of Brittany. From February 2003 till June 2004, variations in density, reproductive status, length and phenolic content were assessed at three sites. Seasonal variability of the density was pronounced at two exposed sites (Fort Bloqué and Pointe du Diable), but absent at the sheltered site (Callot), where the macroalga was observed year-round. Thalli were generally longer in Summer (up to 73.2 ± 2.7 cm at Fort Bloqué), and had reproductive receptacles from May to September at Pointe du Diable, though only from June to September in the other stations (Callot and Fort Bloqué). Phenolic content was maximal during the reproductive period, which could be interpreted as chemical protection of the receptacles. Finally the collected data were used to explain the persistence of S. muticum and its proliferation in Brittany.  相似文献   

2.
The effects of algal blooms on seaweeds have been rarely studied, although harmful algal blooms (HABs) are now normally regarded as worldwide incidents. In the present study, the effects of dense Karenia mikimotoi cells on the growth and photosynthesis of Hizikia fusiformis, a common and commercially cultivated macroalga in coastal waters of the East China Sea (ECS), were studied to understand the possible consequences when the mariculture encountered a dense harmful algal bloom. Furthermore, the counteraction of the latter on the growth and photosynthetic activities of K. mikimotoi was determined to evaluate the contribution of H. fusiformis commercial cultivation to environmental improvements. The results showed that the chlorophyll a (Chl a) contents, maximal photochemical efficiency (Fv/Fm) and relative electron transfer rate (rETR) of gas vesicles (specialized leaves), adult and young receptacles of H. fusiformis were all significantly (P < 0.05) inhibited compared with the mono-cultured ones. When compared with mono-cultured H. fusiformis (without K. mikimotoi), the Chl a contents in gas vesicles, adult and young receptacles decreased by 20.6%, 17.6% and 33.2% within 2 weeks. Correspondingly, the Fv/Fm decreased by 7.9%, 37.4% and 43.7%; the apparent photosynthetic efficiency (α) decreased by 9.4%, 47.1% and 48.3%; and rETR decreased by 19.5%, 52.6% and 68.2%, respectively. The Chl a concentration of the mono-cultured K. mikimotoi (without H. fusiformis) increased to 2247.97 μg l−1 from 958.11 μg l−1 within 14 d. Those of the co-cultivated ones (with H. fusiformis), however, increased to 1591.31 μg l−1 on the 8th day and then decreased rapidly to 254.99 (±37.73) μg l−1 after the next 6 days. Furthermore, compared with the mono-cultured K. mikimotoi cells, the Fv/Fm, α and rETRmax of co-cultivated ones decreased by 9.4%, 36.3% and 30.6%, respectively. The results indicated that the mature sporophytes of H. fusiformis were resistant to dense K. mikimotoi blooms and this resistance was organ-dependent as: gas vesicle > adult receptacles > young receptacles. On the other hand, commercial mariculture of H. fusiformis demonstrated the potential of preventing the occurrence of algal blooms.  相似文献   

3.
This study focuses on three factors that affect the survival of the lilac pyralid, Palpita nigropunctalis (Lepidoptera:Crambidae): (1) the effect of leaf toughness on survival rate to clarify the availability of leaves as food, (2) the effect of temperature on immature development to determine the lower thermal threshold, and (3) the effect of temperature on head capsule width to clarify whether head capsule width can be used to discriminate among field-collected larval instars. Larvae could develop on Osmanthus fragrans var. aurantiacus leaves collected in April, but not on leaves collected in June or September which were too tough to eat. More than 80% of the larvae on the leaves of Ligustrum lucidum, Ligustrum japonicum, Ligustrum obtusifolium and Syringa vulgaris completed development, regardless of the collection time. P. nigropunctalis completed development on L. lucidum at temperatures from 15 to 27.5 °C with a photoperiod of either 15 L:9D or 16 L:8D, but not at 30 °C, at which temperature no eggs hatched. The lower thermal threshold and thermal constant for total development from egg to adult were estimated at about 7 °C and 450–460 degree-days. Most of the larvae were 5-instar type larvae (passed through 5 instars) regardless of the temperature, but a few 6-instar type larvae (4 of 355) were noted at temperatures of 22.5 °C and higher. No overlap of the ranges of head capsule widths was detected for the 5-instar type larvae, indicating that head capsule width can be used to discriminate among field-collected larval instars.  相似文献   

4.
Campuloclinium macrocephalum (Less.) DC. is a perennial herb widely distributed in the New World, but introduced to South Africa, where it is commonly called “pompom weed”. This species is considered one of the most important weeds from Brazil and it has been included among the plant invaders of South Africa. Results of the meiotic and embryological analyses of six populations of C. macrocephalum are reported in this paper. The microsporogenesis analysis revealed five triploid (2n = 3x = 30) and one diploid (2n = 2x = 20) populations with a basic chromosome number x = 10. The diploid specimens showed regular meiotic behavior, but the triploid plants presented irregular chromosome pairing which result in the formation of univalents, bivalents and trivalents at diakinesis. In consequence, laggard chromosomes, unbalanced nuclei and micronuclei were observed in subsequent phases of meiosis. The embryological analysis showed that the triploid specimens of C. macrocephalum have embryo sac development from a nucellar cell (apospory), which indicates that these specimens are apomictic. Almost all cases of apomixis found in tribe Eupatorieae are diplosporous apomixis. Campuloclinium macrocephalum constitutes the second species of the tribe and the first of the genus with apospory as reproductive system. The aposporous apomixis combined with the presence of xylopodium would be two important factors responsible for the invasiveness of C. macrocephalum.  相似文献   

5.
《Small Ruminant Research》2008,74(1-3):122-126
Sixty-eight female and 4 male lambs of the Chios breed born in autumn (September–October) and 48 female and 4 male kids of the Damascus breed also born in autumn (November), were used to evaluate the effect of melatonin implants (Regulin®) on the initiation of the breeding season. For each species and sex, half of the animals were either left untreated to serve as controls (C) or received ear implants (females one and males two implants) of melatonin (MEL) in May (spring). Each C and MEL group of females was kept separately and away from males for 5 weeks after implantation and then, C and MEL males were joined with the respective groups for 45 (sheep) and 35 days (goats). Animals not conceiving during the early June–July breeding season, were mated again in September (natural breeding season). The reproductive performance and the 60-day milk yield of animals giving birth during the two seasons were compared. Early in the season (mid November–December), significantly more MEL than C ewes and goats gave birth (75.5% versus 23.5%, p < 0.01; 70.8% versus 37.5%, p < 0.05, respectively). For both species, most of the other characteristics examined were significantly affected by season, but not by treatment. Females giving birth early in the season were approximately 80 days younger at parturition and recorded a lower body weight at mating than those giving birth in the natural February–March season. In the first mating period, the animals mated and conceived had similar body weights to those not mated. The natural, compared with the early June–July mating season, was associated in sheep with higher litter weight at birth (7.0 kg versus 5.8 kg, p < 0.05) and in sheep and goats with a higher number (p < 0.05) of offspring born live (1.78 versus 1.38; 2.0 versus 1.61, respectively) and weaned (1.74 versus 1.36; 1.82 versus 1.35, respectively). Total litter size at birth and 60-day milk yield after weaning, were not significantly different between the two seasons. It could be concluded that melatonin implants administered during the last month of spring in autumn-born female Chios sheep and Damascus goats, advanced the initiation of their breeding season by about 80 days when joined with young males also treated with melatonin implants. The overall reproductive performance and milk yield of animals breeding early, was satisfactory and comparable to that of animals breeding in the natural breeding season.  相似文献   

6.
Secoisolariciresinol diglucosides (SDGs) (S,S)-SDG-1 (major isomer in flaxseed) and (R,R)-SDG-2 (minor isomer in flaxseed) were synthesized from vanillin via secoisolariciresinol (6) and glucosyl donor 7 through a concise route that involved chromatographic separation of diastereomeric diglucoside derivatives (S,S)-8 and (R,R)-9. Synthetic (S,S)-SDG-1 and (R,R)-SDG-2 exhibited potent antioxidant properties (EC50 = 292.17 ± 27.71 μM and 331.94 ± 21.21 μM, respectively), which compared well with that of natural (S,S)-SDG-1 (EC50 = 275.24 ± 13.15 μM). These values are significantly lower than those of ascorbic acid (EC50 = 1129.32 ± 88.79 μM) and α-tocopherol (EC50 = 944.62 ± 148.00 μM). Compounds (S,S)-SDG-1 and (R,R)-SDG-2 also demonstrated powerful scavenging activities against hydroxyl [natural (S,S)-SDG-1: 3.68 ± 0.27; synthetic (S,S)-SDG-1: 2.09 ± 0.16; synthetic (R,R)-SDG-2: 1.96 ± 0.27], peroxyl [natural (S,S)-SDG-1: 2.55 ± 0.11; synthetic (S,S)-SDG-1: 2.20 ± 0.10; synthetic (R,R)-SDG-2: 3.03 ± 0.04] and DPPH [natural (S,S)-SDG-1: EC50 = 83.94 ± 2.80 μM; synthetic (S,S)-SDG-1: EC50 = 157.54 ± 21.30 μM; synthetic (R,R)-SDG-2: EC50 = 123.63 ± 8.67 μM] radicals. These results confirm previous studies with naturally occurring (S,S)-SDG-1 and establish both (S,S)-SDG-1 and (R,R)-SDG-2 as potent antioxidants and free radical scavengers for potential in vivo use.  相似文献   

7.
The seasonal abundance of Palpita nigropunctalis larvae was studied on five oleaceous tree species in Ibaraki, central Japan, for two years. The larval population peaked on some tree species in both spring and autumn while it peaked on other tree species only in autumn. In bimodal populations, the spring peaks consisted of larvae infesting leaves, while the autumn peaks consisted of larvae infesting various tree parts (flowers, fruits and leaves). Larval development was longer and pupal weights were lower on Ligustrum lucidum fruits than on Ligustrum japonicum fruits. Thus, L. japonicum fruits were suitable for larval development in autumn. First-instar larvae appeared to occur three times per year (in late April to early May, mid to late September and early to mid October). Adults were observed from late March to early April, mid May to early June, and early September to mid November at the census sites, showing that P. nigropunctalis had three generations a year. The percentage of females having premature ovaries were 64.3 and 12.5% at 15 °C under 14-h and 15-h photophases, respectively, and 28.6 and 25% at 20 °C under the respective photophases. These temperatures and photoperiods are typical of those in May and June in the census sites. The ovaries of females collected in the field between late May and mid July were premature, in agreement with the laboratory experiments. The pupal duration was prolonged under the short photoperiod, especially at reduced temperatures. We discuss a possible life cycle of P. nigropunctalis in Ibaraki.  相似文献   

8.
A reproductive biology study of the spider crab Schizophrys aspera (H. Milne Edwards, 1834) was conducted in the Suez Canal from July 2012 to June 2013. The annual sex ratio (Male:Female) of S. aspera was female biased with values of 1:1.25. Out of the four ovarian development stages of this crab, two stages were observed in the Suez Canal throughout the whole year. The ovigerous crab’s carapace width varied from 28 to 52 mm. This crab species can spawn during most of the year in the canal water, with a peak during late spring and early winter. The fecundity of ovigerous females ranged between 2349 and 13600 eggs with a mean of 5494 ± 1486 eggs. Female crabs that reached sexual maturity exhibited a minimum carapace width varying between 22 and 46 mm, and fifty percentage of all ovigerous females showed a carapace width of 36 mm.  相似文献   

9.
This work assesses the impact of the use of chicken manure and irrigation water on the toxicological quality of Solanum macrocarpon, a highly appreciated vegetable. A control site in Glo-Djigbé, gardeners’ sites at Houéyiho, Fidjrossè, and Agongbomey were included in the study. Lead has been sought in the environment of S. macrocarpon culture by Atomic Absorption Spectrophotometry (AAS). Regarding the content of lead in the droppings, the averages in mg/kg varied between 0.696 and 3.618. The soil of Houéyiho (46.320 ± 0.651 mg/kg) was more contaminated with lead than that of the other sites. The irrigation water used in the study sites was slightly contaminated with lead with values ranging between 0.038 and 0.017 mg/L. Leaves taken from the control site, Glo-Djigbé were contaminated with lead with a value of 0.936 ± 0.070 mg/kg compared to those of Agongbomey, Houéyiho and Fidjrossè. The leaves of S. macrocarpon were contaminated with lead at significantly values higher than those imposed by the FAO (0.1 mg/kg). Consumption without precautions could expose people to diseases related to the accumulation of this metal.  相似文献   

10.
《Biological Control》2006,36(2):232-237
Adults of Trissolcus basalis and Telenomus podisi were stored either at 15 or 18 °C after their immature development had been completed at 18 or 25 °C. Longevity of the parasitoids in the storage temperatures was evaluated, as well as fecundity and longevity following their return to 25 °C after different periods in reproductive diapause. Temperature during immature development influenced female longevity and highest mean longevity was obtained for females that developed to the adult stage at 25 °C and then were stored at 15 °C (ca. 13 months for T. basalis and 10 months for Te. podisi). For adults of T. basalis that developed at 25 °C, storage periods of 120 or 180 days at 15 or 18 °C did not affect fecundity. The fecundity of T. basalis females that developed at 18 °C and were stored for 120 days at 15 or 18 °C was not affected; however, after remaining for 180 days, fecundity was reduced in ca. 30 and 50%, respectively. Storage of Te. podisi adults at 15 or 18 °C significantly reduced fecundity. It is concluded that adults of T. basalis can be stored in the adult stage at 15 or 18 °C between two soybean crop seasons for mass production purposes, aiming the biological control of stink bugs.  相似文献   

11.
《Aquatic Botany》2005,82(1):55-70
A study of the meadows of the invasive Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque was carried out over one year at Marseilles (Provence, France) where the alga is thriving, probably since 1994, in the cold waters of the north western Mediterranean Sea. At an early phase of colonisation, the C. racemosa meadow is characterized by a patchy distribution pattern. Several years are necessary to obtain a dense and continuous meadow. In one area colonized for more than 4 years, C. racemosa has developed a continuous meadow with wide seasonal variations. Maximum development was reached in autumn (biomass: 82 ± 3 g DW m−2; length of stolons: 1162 ± 86 m m−2; number of apices: 8360 ± 405 m−2; number of erect axes: 20955 ± 1499 m−2) and the minimum from winter to early spring (respectively, 0.3 ± 0.1 g DW m−2; 3 ± 1 m m−2; 220 ± 55 apices m−2; 35 ± 15 erect axes m−2). Seasonal variations in the growth rate were highly significant. The season of high growth lasted from June to October. The apical growth rate of a stolon reached a maximum of 7.5 ± 0.3 mm day−1 in early October, then began to decrease significantly from the end of October to December, before becoming nearly nil from January to early May. Annual net production rate expressed in terms of stolon length and biomass was estimated as 5801 m m−2 a−1 and 612 g DW m−2 a−1, respectively. During the growth period, the turnover rate of the C. racemosa stolons was estimated at from 25 to 46 days. The growth rate was closely correlated to the seawater temperature (R2 = 0.83), whereas no significant correlation was found between growth and irradiance. During the growth period, a decrease in temperature rapidly affects the growth rate, which soon recovers its earlier level when the temperature rises again. In winter, the growth rate decreased rapidly with the seasonal drop in the seawater temperature. Grazing by fish (Sarpa salpa and Boops boops) can also affect the growth rate from September to December by consumption of the erect axes and stolon apices, enhancing the ramification of stolons. Seasonal changes at Marseilles are much sharper than those reported for warmer Mediterranean localities (French Riviera, Italy, Croatia): in winter and early spring C. racemosa meadows decreased and locally disappeared, leaving a barren substrate. C. racemosa survives the lower winter seawater temperatures of the north-western Mediterranean Sea probably in the form of zygotes and/or small fragments (rhizoids, stolons, propagules).  相似文献   

12.
Clitostethus arcuatus is a major, cosmopolitan predator of some Aleyrodidae. Field collected adult beetles were reared in the laboratory on different diets: Siphoninus phillyreae eggs, Trialeurodes vaporariorum eggs, Sitotroga cerealella eggs, or an artificial diet consisting of honey, yeast, and pollen. All experiments were conducted at 25 ± 2 °C, 65 ± 5% RH and a photoperiod of 16:8 (L:D) h. Female and male C. arcuatus consumed a mean (± SE) of 61 ± 0.6 and 27 ± 0.9 T. vaporariorum eggs d? 1, respectively, and a mean of 56 ± 2.2 and 29 ± 1.1 S. phillyreae eggs d? 1, respectively. Significant differences were noted between sexes and between hosts consumed by female C. arcuatus. No feeding occurred on S. cerealella eggs. Although there was a significant difference between rates of oviposition due to diet, fertility rates on different diets did not show significant differences. The sex ratio of C. arcuatus (female:male) was 51.4:48.6, 55.2:44.8, and 54.6:45:4 when adults fed on T. vaporariorum, S. phillyreae, and artificial diet, respectively. These differences were not significantly different. Average longevity (± SE) was 66.4 ± 2.6, 54.9 ± 2.5; 77.3 ± 6.9, 67.5 ± 7.2; and 86.4 ± 4.5 70.3 ± 3.6 days for female and male C. arctuatus, respectively, on T. vaporariorum, S. phillyreae and artificial diet, respectively, with significant differences between sexes and diets. Although developmental duration on T. vaporariorum was longer than ash whitefly, this difference was not significant (mean 27.68 ± 0.31 and 25.09 ± 0.21 days for predators reared on T. vaporariorum and S. phillyreae, respectively). Given its longevity and fecundity on T. vaporariorum, C. arcuatus may be a good choice for mass release on glasshouse crops infected by greenhouse whitefly.  相似文献   

13.
The Julia Creek dunnart (Sminthopsis douglasi) is an endangered carnivorous marsupial belonging to the family Dasyuridae. This study investigated the oestrous cycle of this species in terms of its reproductive physiology and behaviour to explore more efficient methods of oestrus detection. Ten sexually mature captive female dunnarts were monitored daily at David Fleay Wildlife Park, Burleigh Heads, Australia, from mid September to late December 2006 for changes in urogenital cytology within the urine (0, 1+, 2+ and 3+), running wheel activity, body weight, uneaten food, faecal steroid metabolites (progesterone and oestradiol) and pouch development. Periods of increased running wheel activity were associated (p = 0.004) with an increase in the proportion of cornified urogenital epithelial cells found in the urine; periods of decreasing weight (p < 0.001) and uneaten food (p < 0.001) were also associated with changes in urogenital cytology but not to the point where they would be useful for oestrus detection. Between 60.3% and 92.0% of peak distances (confidence interval 95%) occurred when the epithelial cell index was 2+ or 3+. Only 15.5–37.5% of peak weights (CI: 95%) and 28.1–49.9% of incidences of uneaten food (CI: 95%) occurred when the epithelial cell index was 2+ or 3+. There was no significant difference in the mean length of the oestrous cycle when measured by urogenital cytology (mean ± SD: 25.0 ± 5.7 days; n = 20) or peak distance travelled (mean ± SD: 25.4 ± 5.7 days; n = 20). Changes in the concentration of oestradiol metabolites in Julia Creek Dunnart faeces were not useful in characterising the oestrous cycle. Wheel running activity declined markedly with increased faecal progestagen concentration. The majority of the pouch variables examined showed maximum development during the inter-oestrus period but as there was considerable variation between animals, the pouch was not considered a useful index of oestrus.  相似文献   

14.
《Aquatic Botany》2005,83(1):31-47
The expansion of Sargassum muticum in the Danish estuary Limfjorden between 1984 and 1997 was followed by a decrease in abundance of native perennial macroalgae such as Halidrys siliquosa. Although commonly associated with the expansion of exotic species, it is unknown whether such structural changes affect ecosystem properties such as the production and turnover of organic matter and associated nutrients. We hypothesized that S. muticum possesses ‘ephemeral’ traits relative to the species it has replaced, potentially leading to faster and more variable turnover of organic matter. The biomass dynamics of S. muticum and H. siliquosa was therefore compared in order to assess the potential effects of the expansion of Sargassum. The biomass of Sargassum was highly variable among seasons while that of Halidrys remained almost constant over the year. Sargassum grew faster than Halidrys and other perennial algae and the annual productivity was therefore high (P/B = 12 year−1) and exceeded that of Halidrys (P/B = 5 year−1) and most probably also that of other perennial algae in the system. The major grazer on macroalgae in Limfjorden, the sea urchin Psammechinus miliaris, preferred Sargassum to Halidrys, but estimated losses due to grazing were negligible for both species and most of the production may therefore enter the detritus pool. Detritus from Sargassum decomposed faster and more completely than detritus from Halidrys and other slow-growing perennial macrophytes. High productivity and fast decomposition suggest that the increasing dominance of S. muticum have increased turnover of organic matter and associated nutrients in Limfjorden and we suggest that the ecological effects of the invasion to some extent resemble those imposed by increasing dominance of ephemeral algae following eutrophication.  相似文献   

15.
《Journal of Asia》2020,23(4):942-949
The study focused on the ecological analysis of plant and soil nematode communities associated with vegetables-maize crop sequences in the eastern fringe of Kolkata at Dhapa from December 2011 to April 2014 at a monthly interval. Plant-parasitic nematodes like Pratylenchus zeae, Meloidogyne incognita, Hoplolaimus indicus, Helicotylenchus dihystera, Tylenchorhynchus brevilineatus, Rotylenchulus reniformis, and Criconemoides onoensis were observed in two major cropping sequences of chilli-amaranthus-maize-radish-cauliflower and amaranthus-maize-cabbage-chilli. Among them, R. reniformis was found to be the most prevalent genera with the highest relative prominence value (RPV) of 27.29 followed by P. zeae (20.30) and T. brevilineatus (16.70). The population dynamics of P. zeae revealed the lowest density of the nematode was recorded (26 per 200 cc of soil + 5 g of the root) in March and the highest (634) in September. The variation in the abundances of other PPNs was also noted, and that attributed to the crops in the crop sequence and weather conditions. Low numbers of R. reniformis was found in the maize rhizosphere. The saprozoic nematodes (SNs) maintained higher mean densities (1734/200 cc soil); they were recorded in high numbers in the rainy season as compared to other seasons. No significant differences in the Shannon diversity index (H′), evenness (J) were observed across the growing period. A significant relationship was found between nematode abundance and climatic variables observed. This study provides baseline information on nematodes associated with maize-based cropping system, population abundance, Mylonchulus-SNs relationships, and population fluctuation in response to environmental factors.  相似文献   

16.
Studies of epiphytic dinoflagellates in Peter the Great Bay, Sea of Japan in 2008–2011 revealed the presence of 13 species. Five of the species are known as potentially toxic: Amphidinium carterae, A. operculatum, Ostreopsis cf. ovata, O. cf. siamensis and Prorocentrum lima. The maximum species richness and abundance of epiphytic dinoflagellates were observed in autumn (from September to October). Ostreopsis spp. were most widely distributed and predominated, amounting to 99% of the total density of dinoflagellates. Multi-year seasonal dynamics of Ostreopsis spp. in Peter the Great Bay showed that these cells appear as epiphyton in August after maximum warming of surface waters (22–24 °С) and disappear in early November, when the water temperature decreases below 7 °С. Ostreopsis spp. proliferation occurred in September, when the water temperature was 17.2–21.0 °C. The highest densities of Ostreopsis spp. were recorded on September 9, 2010 on the rhodophyte Neorhodomela aculeata – 230 × 103 cells g−1 DW or 52 × 103 cells g−1 FW. The spatial distribution of epiphytic dinoflagellates was investigated in the near-shore areas of Peter the Great Bay during the second half of September 2010 to evaluate the role of hydrodynamic conditions. Epiphytic dinoflagellates were not found in sheltered sites having weak mixing hydrodynamics. However, the abundances of Ostreopsis spp. were significantly higher at sites having moderate turbulence compared to biotopes experiencing strong wave action. Densities of Ostreopsis spp. were not significantly different on macrophytes with branched thallus of all taxonomic divisions. However, the average cell densities of Ostreopsis spp. on green algae with branched thallus were significantly higher than on green algae having laminar thallus.  相似文献   

17.
The Ansell's mole-rat (Fukomys anselli, Bathyergidae) is a small-sized social subterranean rodent whose distribution is confined to the Lusaka area in Zambia. It is an established model species for various laboratory studies, but until now the knowledge of its biology under natural conditions has been limited. Here, we provide the first comprehensive natural history and ecological data on a free living population from Miombo woodland. The Ansell's mole-rat lives in groups of up to 13 individuals (mean 9.7 ± 2.5; N = 9 complete, fully established family groups) with a single breeding pair per group. The family groups occupy very large and complex burrow systems consisting of 0.5–2.8 km of tunnels (mean = 1.2 ± 0.6 km, N = 15), which are densely branched and reticulated especially around nests. Burrow systems of neighbouring family groups were often interconnected by a freely passable tunnel, which has never before been documented in any African mole-rats. Mole-rat food density in the study area was relatively low (10.0 ± 8.4 m?2) but its biomass was large (457 ± 889 g m?2). This, together with a relatively workable soil (cone resistance = 529 ± 26 N cm?2 at the end of June, with 10% soil humidity), indicates moderate ecological conditions, which disagrees with the aridity food-distribution hypothesis (AFDH) considering small body size and sociality in bathyergids adaptations to harsh environments.  相似文献   

18.
Progesterone (P4) is involved in the regulation of essential reproductive functions affecting the target cells through both nuclear progesterone receptors (PGRs) and membrane progesterone receptors. The aim of this study was to determine the mRNA and protein expression for PGRMC1, PGRMC2, SERBP1 and PGR within the bovine endometrium during the estrous cycle and the first trimester of pregnancy. There were no changes in PGRMC1 and PGRMC2 mRNA and protein expression during the estrous cycle, however, mRNA levels of PGRMC1 and PGRMC2 were increased (P < 0.001) in pregnant animals. SERBP1 mRNA expression was increased (P < 0.05), while the level of this protein was decreased (P < 0.05) on days 11–16 of the estrous cycle. The expression of PGR mRNA was higher (P < 0.01) on days 17–20 compared to days 6–10 and 11–16 of the estrous cycle and pregnancy. PGR-A and PGR-B protein levels were elevated on days 1–5 and 17–20 of the estrous cycle as compared to other stages of the cycle and during pregnancy. In conclusion, our results indicate that P4 may influence endometrial cells through both genomic and nongenomic way. This mechanism may contribute to the regulation of the estrous cycle and provide protection during pregnancy.  相似文献   

19.
《Cancer epidemiology》2014,38(1):62-65
Background: Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) associated with breast cancer risk. Some of these loci have unknown functional significance and may mediate the effects of hormonal exposures on breast cancer risk. We examined relationships between breast cancer susceptibility variants and menstrual/reproductive factors using data from two population-based studies. Methods: The first analysis was based on a sample of 1328 women age 20–74 who participated as controls in a case–control study of breast cancer conducted in three U.S. states. We evaluated the associations between age at menarche, age at natural menopause and the reproductive lifespan with 13 previously identified breast cancer variants. Associations were also examined with a genetic score created as the sum of at-risk alleles across the 13 variants. For validation, significant results were evaluated in a second dataset comprised 1353 women age 43–86 recruited as part of a cohort study in Wisconsin. Results: Neither the genetic score nor any of the 13 variants considered individually were associated with age at menarche or reproductive lifespan. Two SNPs were associated with age at natural menopause; every increase in the minor allele (A) of rs17468277 (CASP8) was associated with a 1.12 year decrease in menopause age (p = 0.02). The minor allele (G) of rs10941679 (5p12) was associated with a 1.01 year increase in age at natural menopause (p = 0.01). The results were not replicated in the validation cohort (B = −0.61, p = 0.14 and B = −0.01, p = .0.98, respectively). Conclusions: The evaluated variants and reproductive experiences may work through separate pathways to influence breast cancer risk.  相似文献   

20.
Lesser mulberry pyralid, Glyphodes pyloalis Walker, is a monophagous pest of mulberry and has recently been reported in northern Iran. The biology and life table of this pest were studied in controlled conditions (24 ± 1 °C, 75 ± 5% RH and 16:8 LD). Mortality rate, metamorphosis, appearance of adult insects and adult sex ratio were recorded daily. Data were analyzed based on an age-stage, two-sex life table. Developmental rate among individuals and between sexes were also considered. The developmental periods for the egg, first through fifth instar larvae, prepupae and pupae were 4.06 ± 0.03, 2.93 ± 0.03, 2.03 ± 0.02, 2.01 ± 0.01, 2.10 ± 0.03, 4.09 ± 0.03, 2.04 ± 0.02 and 9.7 ± 0.09 days, respectively. The mean total developmental period from egg to adult was 35.40 ± 0.37 days. The maximum adult longevity was 7 and 11 days for males and females, respectively. The pre-oviposition period lasted 2.14 ± 0.04 days. Laboratory observation showed that adults are nocturnal and female lay eggs at night. The intrinsic rate of increase (rm) and the finite rate of increase (λ) were 0.14 ± 0.005 d? 1 and 1.15 ± 0.01 d? 1. The net reproductive rate (R0), gross reproductive rate (GRR) and mean generation time (T) were 134.67 ± 20.6 female offspring, 294.71 ± 4.07 eggs/female and 34.44 ± 0.2 days, respectively. Life expectancy of freshly laid egg was 32.15 days.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号