The role of male accessory-gland substance on female reproduction with some observations of spermatogenesis in the stable fly

The bulbous tubular portion of the median ejaculatory duct functions as the accessory gland in the male stable fly, Stomoxys calcitrans. The gland started to enlarge after emergence when the fly was fed on sugar-water or blood. Implants of accessory glands from sugar-water or blood-fed males were effective in stimulating oviposition in virgin females. The injection into females of accessory-gland extracts from males fed blood prevented insemination; this extract was effective in concentration as low as 0.25 gland per female. Accessory-gland extracts from sugar-water fed males were only partially effective in preventing female insemination. However, the accessory-gland extracts of male stable flies had little effect on insemination when injected into three other species of female dipterans.Spermatogenesis was completed by the time of emergence, or shortly thereafter, a process independent of blood feeding. Three types of spermatids were identified, forming a continuum of spermiogenesis stages. Fat, fusiform spermatozoa elongated to become thin, elongate and mature spermatozoa.     

Morphological and cytological investigations ofUlothrix zonata and taxonomy of the related species

The present communication deals with the observations made on the morphology, reproduction and cytology ofUlothrix zonata (Weber & Mohr)Kütz. in culture. The alga displays a remarkable phenotypic plasticity in nature as well as in culture. The present study provides additional evidence of karyology in support ofLokhorst andVroman's treatment ofU. zonata which merges a number of earlier described species in it. The cytological details and chromosome number (n = 10) determined for the Indian isolates ofU. zonata agree with those ofSarma for the British material.NBRI Research Publication No. 63 (N.S.)     

About a transmissible influence through several generations in a clone of the rotifer notommata copeus EHR

Over ten years, the individuals of an orthoclone of Notommata copeus gradually lost their sensitivity to photoperiod. This loss is transmissible but reversible in three generations. It is endogenous but not chromosomal. The hypothesis is forwarded that it is induced by external factors, and quite possibly crowding.     

Effect of food limitation on food consumption and reproductive allocation by adult milkweed bugs, Oncopeltus fasciatus

Male/female pairs of adult milkweed bugs, Oncopeltus faciatus were offered reduced food rations (100 mg milkweed seeds/week, 50 mg seeds/week, and 25 mg seeds/week) at 232C, 14L : 10D photoperiod. The high rate of food consumption normally occurring during the teneral period (first 8 days posteclosion) and subsequent food consumption were reduced on both reduced rations. Initial fresh weight was lost by bugs on both reduced rations and their weekly fresh body weight tended to remain less than bugs on the 100 mg seeds/week ration.Normal onset of egg production (about 3 weeks posteclosion) was delayed 6 weeks and normal length of a female's life (13–14 weeks) was increased 7–8 weeks on the 25 mg seeds/week ration. Rate of egg production exhibited a linear decrease with decrease in food ration on both reduced rations due to an increased interclutch interval, while fresh egg weight, duration of egg stage, number of eggs/clutch and percentage of clutches containing fertile eggs were little affected.Gross egg production efficiency (efficiency of conversion of ingested food into eggs = dry mg egg production × 100/dry mg food ingested) was high on both the 100 and 50 mg seeds/week rations (27.9% and 21.1%, respectively) and low (7.7%) on the 25 mg seeds/week ration. These data are discussed in the context of the reciprocal interaction between nutrient intake and egg production.     

Ecdysterone antagonism,mimicry, and synergism of juvenile hormone action on the Monarch butterfly reproductive tract

Previous research on Monarch butterflies has shown that juvenile hormone (JH) stimulates the development of the ovary and certain reproductive glands of both sexes. Ecdysterone injections into intact Monarchs demonstrate that low doses of this hormone inhibit ovarian development, and higher doses stimulate the male and female reproductive glands. In addition, experiments using neckligatured adults show that ecdysterone stimulates the reproductive glands of both sexes, in the apparent absence of JH, with the most pronounced effect being observed on the female colleterial gland. Other studies with neck-ligatured animals demonstrate that ecdysterone also synergizes with JH on the female gland and all three male glands. The feasibility of using Monarch reproductive glands for studies on the mode of action and interaction of JH and ecdysterone, and the possibility of a rôle of ecdysterone in the normal regulation of Monarch oögenesis, are discussed.     

连翘花的结构与繁育系统研究

通过定株观察、解剖和人工套袋交叉授粉试验对连翘花的生长发育和繁殖系统进行研究.结果表明:(1)连翘具有2种避免自交的方式,雌雄异位和雌雄异熟.其雌雄异位表现为长雄蕊短雌蕊花型和短雄蕊长雌蕊花型;雌雄异熟表现为长雄蕊短雌蕊花型为雄蕊先于雌蕊成熟,短雄蕊长雌蕊花型表现为雌蕊先于雄蕊成熟.(2)连翘花P/O值测定和户外套袋交叉授粉试验显示,P/O值为2 000±300;不同类型花的异花授粉结果率在50.64%~80.32%,其中短型花的花粉授到长型花柱头的结果率最高,达80.32%,而长型花和短型花的同型花授粉结果率分别为2.92%和34.15%,表明连翘的异花授粉结果率高于自花授粉,以异交为主,其繁育系统属兼性异交.研究结果认为,连翘雌雄异位和雌雄异熟是其自然结果率低下的主要原因,为进一步探讨连翘在木犀科中的系统进化提供了生殖生态学的依据.     

辽宁和江苏两省杂草稻植物性状多样性

辽宁和江苏两省是我国杂草稻(Oryza sativa f. spontanea)发生最为严重的地区之一, 为明确两省杂草稻识别特征和类型, 我们在两省14个市29个样点采集样品, 与当地栽培水稻品种一并在南京种植, 观测了营养生长期和生殖生长期的23个植物性状。结果表明, 两省杂草稻在营养生长期的1月株高、1月和2月分蘖数, 在生殖生长期的果皮色、谷粒长/宽比、百粒重、落粒性、秆硬度、剑叶宽、剑叶长、有效穗数、50%黄熟、50%黄熟–50%抽穗和全黄熟等性状与相应的当地栽培稻存在差异;主成分1和主成分2组成的二维散点图(累计贡献率达43.24%)也显示出两省杂草稻间以及与栽培稻间的差异性。采用欧氏距离对两省杂草稻进行系统聚类可以将杂草稻分为籼型和粳型。其中辽宁省杂草稻全部聚在粳型类群中, 它们又可细分为两类; 江苏省杂草稻既有粳型, 又有籼型, 其中粳型与辽宁省杂草稻聚在粳型类群中, 籼型又可分为3类。这6个类群分别具有如下突出特点: 第1类为强落粒、粒轻、秆矮、早熟、偏粳等; 第2类为无芒、穗多、强休眠、剑叶窄、偏粳等; 第3类为长芒、弱分蘖、穗少、弱落粒、偏粳等; 第4类为硬秆、剑叶宽、迟熟、强休眠、偏籼等; 第5类为红果皮、粒长、软秆、粒重、偏籼等; 第6类为无芒、株高、穗长、剑叶长、偏籼等。上述杂草稻的形态学指标和类型的研究将为两省开展杂草稻危害防治工作提供理论依据。     

Seasonal changes in condition, nutrition, gonad maturation and energy content in barbel, Barbus sclateri, inhabiting a fluctuating river

The objective of this study was to investigate the seasonal cycle of condition, nutrition and gonad development, as well as the magnitude of seasonal variations in energy content of somatic and gonad tissues in juveniles, males and females of Sclater's barbel, Barbus sclateri, from the upper Guadalete River (south Spain). The influence of reproductive cycle on somatic changes was also investigated and discussed. Measurements of condition factor (K), somatic index (SI), gonadosomatic index (GSI) and somatic and gonad energy content (J g^-1 dw) were made in individual specimens taken from the Guadalete River monthly for 12 months. This freshwater ecosystem is characterised by strong seasonal fluctuations in water and flow level, temperature and food supply. It was found that in general juveniles, males and females of barbel exhibited a similar condition, nutrition and somatic energy cycle throughout the year, with the highest values in spring and the lowest in summer. Depletion of K, SI and somatic energy storage from spring until mid-summer seems to be associated with high metabolic demands during this period, and in adult fish also with spawning-related activity. The gonad index and energy content of the gonad were the highest in April and the lowest in summer for both sexes. Spawning took place during late spring – early summer, with fish quiescent by mid summer. The energy required for ovarian development (3970 J g^-1 dw) was greater than the one for testes development (2763 J g^-1 dw). Data on gonad energy content indicated a period (March to April) of intense energy accumulation (64% males and 37% females) which was related to the decline in the average somatic energy content in males and females. The somatic energy content was linearly related to K and SI. In the same way, GSI correlated positively with gonad energy. Linear trends were found between somatic parameters (K, SI and energy content) and gonad parameters (GSI and energy content). This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive efficiency and shade avoidance plasticity under simulated competition

Plant strategy and life‐history theories make different predictions about reproductive efficiency under competition. While strategy theory suggests under intense competition iteroparous perennial plants delay reproduction and semelparous annuals reproduce quickly, life‐history theory predicts both annual and perennial plants increase resource allocation to reproduction under intense competition. We tested (1) how simulated competition influences reproductive efficiency and competitive ability (CA) of different plant life histories and growth forms; (2) whether life history or growth form is associated with CA; (3) whether shade avoidance plasticity is connected to reproductive efficiency under simulated competition. We examined plastic responses of 11 herbaceous species representing different life histories and growth forms to simulated competition (spectral shade). We found that both annual and perennial plants invested more to reproduction under simulated competition in accordance with life‐history theory predictions. There was no significant difference between competitive abilities of different life histories, but across growth forms, erect species expressed greater CA (in terms of leaf number) than other growth forms. We also found that shade avoidance plasticity can increase the reproductive efficiency by capitalizing on the early life resource acquisition and conversion of these resources into reproduction. Therefore, we suggest that a reassessment of the interpretation of shade avoidance plasticity is necessary by revealing its role in reproduction, not only in competition of plants.     

强壮水螅的特征及其与寡水螅的种间差别问题

一种广泛分布于黑龙江省的大型具柄水螅被暂定为强壮水螅Hydra robusta(IT(?) 1947)。这一中国品系与IT(?)(1947)在日本报告的新种主要特征相同,包括具有精巢乳头。只是精巢乳头不稳定。在实验室条件下第一次有性生殖时每个雄体都发生精巢乳头,但第二次有性生殖时,同一群的后代可全部失去精巢乳头。这是介于强壮水螅与寡水螅Hydra oligactis Pallas(1766)之间的中间性状。从而导致作者做出结论,认为过去其他学者所主张的,以精巢乳头的有无做为鉴别特征来区分强壮水螅和寡水螅是不可靠的。因此,本文又检验了此种水螅的体细胞染色体,证明2n=30,其中第二对染色体上有明显近中位置的次缢痕,最小染色体的长度为最大染色体长度的二分之一以上。这些可做为此种水蝗的鉴别特征。对Niiyama(1944)和Datta(1970)在寡水螅上所做的染色体研究也做了比较及讨论。