ONTOGENY OF THE PSEUDOHERMAPHRODITIC REPRODUCTIVE SYSTEM IN NASSARIUS VIBEX (GASTROPODA: BUCCINIDAE: NASSARIINAE)

Pseudohermaphroditism or imposex is an abnormality of the gastropodreproductive system caused by the effects of an environmentalpollutant, tributyltin, in which parts of the male reproductivetract develop in females. In this study, the post-larval developmentof the reproductive system in pseudohermaphroditic male andfemale Nassarius vibex was investigated relative to normal developmentto determine how and when the abnormalities associated withpseudohermaphroditism develop. Two populations of N. vibex were compared:one exhibiting normal development, and one in which the animalswere effected by pseudohermaphroditism. In the affected N. vibexpopulation, a penis and anterior spermiduct developed very earlyin ontogeny in both males and females. Normal reproductive systemdevelopment was affected in some females, evidenced by fusion ofthe induced spermiduct and anterior oviduct, or by abnormaloviduct development. Several males displayed precocious maturationof the gonad in addition to early development of the anteriorspermiduct and penis. (Received 25 April 2000; accepted 1 July 2000)     

CALCIUM PHOSPHATE GRANULES IN THE REPRODUCTIVE SYSTEM OF OXYCHILUS ATLANTICUS (GASTROPODA: PULMONATA)

The presence of connective interstitial cells in the wall ofseveral organs of the distal reproductive system in Oxychilus atlanticusis described by means of scanning electron microscopy (SEM).Connective interstitial cells extend from the distal part of thevas deferens to the penis, being the dominant cell type of large portionsof the epiphallus as well as in the whole penial caecum (=flagellum).These cells are highly mineralized and are characterized bythe presence of large amounts of solid spherules (up to 4 mmin diameter) in their cytoplasm. A semi-quantitative evaluationby X-ray microanalysis demonstrates that calcium and phosphorusare the main elements of the spherules. Their function is unknown,but they could aid in copulation or they could assist the survivalof the transferred spermatozoa. (Received 7 June 1999; accepted 8 September 1999)     

脉红螺Rapana venosa(Valenciennes)生殖系统的组织解剖学研究

脉红螺为雌雄异体。雄性生殖系统包括8部分:精巢、输精小管、贮精囊、输精管、前列腺、输精管外套段Ⅰ、输精管外套段Ⅱ和阴茎。雌性生殖系统包括7部分:卵巢、输卵小管、输卵管Ⅰ段、纳精囊、输卵管Ⅱ段、蛋白腺和产卵器。 脉红螺精子形成过程中有精子细胞团形成。精子线形,由头段、中段和尾段构成。头段核基部内凹形成倒“U”形管;中段有丝状线粒体鞘,螺旋缠绕轴丝;尾段由9条粗纤维包围‘9+2’型轴丝构成。 本文亦对前列腺、蛋白腺及蛋白质卵黄粒等的超微结构作了观察。     

THE ONTOGENY OF THE PLEUREMBOLIC PROBOSCIS IN NUCELLA LAPILLUS (GASTROPODA: MURICIDAE)

The ontogeny of the proboscis in Nucclla lapillus was investigatedusing light and scanning electron microscopy. The proboscis develops by elongation of the body wall surroundingthe mouth, whilst the rhynchocoel is formed by imagination ofthe body wall surrounding the proboscis. Elongation of the snoutduring development of the proboscis results in the anteriormovement of the anterior oesophagus and part of the mid-oesophagus(the valve of Leiblein) which is drawn through the circum-oesophagealnerve ring. The acinous salivary glands and the radular sacalso come to lie anterior to the nerve ring. The mid-oesophagealgland of Leiblein and the glandular dorsal folds are not drawnthrough the nerve ring, and develop behind it. The anterioroesophagus elongates at a later stage of development to producethe oesophageal length required for extension of the adult proboscis.Modifications to this sequence of events, or changes in therate of growth of the various parts of the foregut, might accountfor the differences between the neogastropod and neotaenioglossanpleurembolic proboscis. The intraembolic proboscis found inthe Conoidea and the Pseudolivoidea may have been derived viaa modification of the developmental sequence which producesthe muricoidean pleurembolic proboscis. (Received 10 May 1996; accepted 15 August 1996)     

THE ESTUARINE MUD SNAIL, NASSARIUS OBSOLETUS: ABNORMALITIES IN THE REPRODUCTIVE SYSTEM

Females of the dioecious snail Nassarius obsoletus may havethree male characteristics: a penis, a vas deferens, and theconvolution of a normally straight gonadial oviduct to resemblea stunted mimic of the vesicula seminalis in the male. The firstcharacteristic is the most common and the last is the leastcommon. Collectively these characteristics were called imposex.A system for evaluating its frequency of occurrence and intensityof expression was developed. The frequency and intensity ofimposex was similar among different age groupings of snails,though there may be a trend towards less imposex in juveniles.The differences in the frequency and intensity of imposex betweengroups of parasitized and unparasitized females were very small.In males the reduction of penis size due to parasites was muchlarger. This pattern ofimposition of male characteristics onfemales is a new syndrome which does not resemble reported formsof hermaphroditism or pseudohermaphroditism related to age orparasitism. ^*Current address: Community Health Program, Electric Power ResearchInstitute, P.O. Box 10412, Palo-Alto, California 94303, U.S.A. (Received 28 August 1979;     

南海织纹螺属三新纪录(腹足纲,织纹螺科)

在整理分类近年来在海南岛和南沙群岛采集的织纹螺科标本时,鉴定出属于织纹螺属的3个中国新纪录种:1)巴氏织纹螺Nassarius (Zeuxis)barsdelli(Ladd,1976);2)蛛形织纹螺Nassarius(Zeuxis)algidus(Reeve,1853);3)杰克逊织纹螺Nassarius(Niotha)jacksonianus(Quoy & Gaimard,1833).3新纪录种分属于Zeuxis 和Niotha两亚属,它们主要生活于潮间带至浅海或百余米水深的泥质沙或沙质海底.     

BREEDING SYSTEM EVOLUTION IN LEAVENWORTHIA: BREEDING SYSTEM VARIATION AND REPRODUCTIVE SUCCESS IN NATURAL POPULATIONS OF LEAVENWORTHIA CRASSA (CRUCIFERAE)

Populations of Leavenworthia crassa (Cruciferae) studied for 3 years exhibited among- and within-population genetic variation for a suite of floral and reproductive traits (flower width, petal length, anther position, ability to set seeds in the absence of pollinators, time to first flowering) associated with breeding system. We used electrophoretic markers to show that a population with small, monomorphically colored flowers with introrse anthers had a significantly lower outcrossing rate (t = 0.03) than did a population with larger, polymorphically colored flowers with extrorse anthers (t = 0.33). In the more-outcrossing population the correlation between higher maternal plant outcrossing rate and the suite of six traits approached significance (P < 0.067), with greater petal size, greater flower width, and reduced ability to set seeds in the absence of pollinators contributing significantly. Plants in selfing populations had a generally higher reproductive success, with a higher number of flowers per plant, a smaller proportion of unfertilized ovules, a smaller proportion of fertilized ovules aborted, a higher rate of fruit set, and overall a larger number of seeds matured than did plants from the more outcrossing populations. Pollen limitation did not appear to account for lower reproductive success in outcrossing populations. Resource limitation did not differ substantially between populations. However, within-ovary patterns of fertilization, abortion, and seed weight were significantly less random in outcrossing populations than in selfing populations, suggesting that differential gamete and embryo success may be responsible for lower reproductive success in outcrossing populations.     

耳河螺生殖器官和精子的形态学研究

耳河螺「Ｒｉｖｕｌａｒｉａ ａｕｒｉｃｕｌａｔａ （Ｍａｒｔｅｎｓ）」为雌雄异体。雄性生殖器官由精巢,输精小管,贮精囊,输精管,前列腺和阴茎组成。精巢内有精子,精子有典型精子和非典型精子两种。扫描电镜下,典型精子头部呈螺旋状,尾端只有一根较粗壮;非典型精子头部和中部为棒状,尾部呈扫帚状,由８－１５根鞭毛组成。     

THE QUADRIPOLAR MICROTUBULE SYSTEM AND MEIOTIC SPINDLE ONTOGENY IN HORNWORTS (BRYOPHYTA: ANTHOCEROTAE)

Ontogeny of the meiotic spindle in hornworts was studied by light microscopy of live materials, transmission electron microscopy, and indirect immunofluorescence microscopy. As in monoplastidic meiosis of mosses and Isoetes, the single plastid divides twice, and the four resultant plastids migrate into the future spore domains where they organize a quadripolar microtubule system (QMS). Additionally, a unique axial microtubule system (AMS) was found to parallel the plastid isthmus at each division in meiosis, much as in the single plastid division of mitosis. This finding is used to make a novel comparison of mitotic and meiotic spindle development. The AMS contributes directly to development of the mitotic spindle, whereas ontogeny of the meiotic spindle is more complex. Nuclear division in meiosis is delayed until after the second plastid division; the first AMS disappears without spindle formation, and the two AMSs of the second plastid division contribute to development of the QMS. Proliferation of microtubules at each plastid results in the QMS consisting of four cones of microtubules interconnecting the plastids and surrounding the nucleus. The QMS contributes to the development of a functionally bipolar spindle. The meiotic spindle is comparable to a merger of two mitotic spindles. However, the first division spindle does not terminate in what would be the poles of mitosis; instead the poles converge to orient the spindle axis midway between pairs of non-sister plastids.     

基于16S rRNA基因序列对织纹螺属的分子系统学分析

研究利用线粒体16S rRNA基因序列片段,对织纹螺属6亚属11种动物进行分子系统学分析。结果显示,种内遗传距离(0～0.007)与种间遗传距离(0.019～0.088)无重叠,这表明线粒体16S rRNA基因能较好地反映织纹螺种间的亲缘关系; 而亚属内遗传距离(0.018～0.031)与亚属间遗传距离(0.028～0.083)存在重叠,表明线粒体16S rRNA基因不能对一些贝壳形态相似的亚属进行区分。同时,确定了疑难种灰白织纹螺Nassarius(Zeuxis)canaliculatum的分类地位,并与相似种西格织纹螺N.(Z.)siquijorensis进行了对比; 确认了秀丽织纹螺Nassarius(Hima)festivus应属于Hima亚属;建议保留单型亚属Varicinassa的有效性。     

COMPARATIVE FITNESS AND REPRODUCTIVE ISOLATION BETWEEN TWO BULINUS GLOBOSUS(GASTROPODA: PLANORBIDAE) POPULATIONS

Bulinus globosus, an intermediate host of schisto-somes, isa self-fertile hermaphrodite species whose regular mating systemis cross-fertilization. Fitness of selfing individuals originatingfrom two geographically remote populations (Elevi, Ivory Coast;Daikaina, Niger) was scored. Individuals were then paired eitherwith individuals from their own population, or with individualsfrom the other population. Electrophoretic analysis showed thatpairing ‘female’ Elevi and ‘male’ Daikainaindividuals results in only a low level of outcrossing, whereasthe reverse pairings produced almost only outcrossed offspring.This could reflect unilateral partial isolation between thetwo populations. However, analysis of fitness values withinand among groups of self-fertilizing and cross-fertilizing individuals,as well as electrophoretic data, suggest that selfing (or partialselfing) is the regular mating system in Elevi. Such experimentsare relevant to the biological control of schistosiomasis byintroducing resistant snails from allopatric populations, becausethey allow an assessment of the fate of introduced resistantgenes. (Received 30 December 1991; accepted 13 March 1992)     

温度对白斑隐蛛个体发育和生殖行为的影响

白斑隐蛛在湖北省以成蛛和幼蛛混合群体越冬,全年可完成3代。3代平均发育历期:雌蛛分别为69.13d、71.80d和76.40d,雄蛛为67.30d、61.39d和69.45d。成蛛寿命一般70～90d,其寿命长短与温度呈负相关。发育起点温度、胚胎期为15.88℃;雌蛛全幼蛛期为13.71℃,雄蛛为14.51℃;全世代为13.69℃。有效积温、胚胎期为128.60日度;雌蛛的全幼蛛期为654.21日度,雄蛛全幼蛛期为655.87日度;全世代为818.67日度。抗高温能力较强,胚胎的最适温度是37℃;幼蛛期是35℃。25～30℃为产卵率最高温区。产卵袋最适温区是20℃～35℃之间,其中以30℃产卵袋数最多。产卵间隔在20℃～35℃温区内,与温度呈负相关。在15℃～35℃温区内,温度对卵袋含卵量影响不大,但超过35℃就显著减少。20℃～30℃为单雌产卵量最高温区,高温(35℃以上)可出现无效卵袋。在正常情况下,卵的孵化率达90％以上。     

MATING SYSTEM ANALYSIS USING PROTEIN ELECTROPHORESIS IN THE SELF-FERTILE HERMAPHRODITE SPECIES BULINUS TRUNCATUS (GASTROPODA: PLANORBIDAE)

Uniparental reproduction in the tetraploid hermaphrodite speciesBulinus truncatus has been suggested to occur via self-fertilization,on the basis of cytological and genetic studies. However, recentanalyses of population genetic structure by protein electrophoresisindicated the occurrence of multi-banded phenotypes referredto as ‘fixed hetero-zygosity’. Although intrapopulationand geographical variation of multibanded phenotypes occur,many populations bear only one type of such patterns. This ledto the suggestion that parthenogenesis may well be the matingsyste in B. truncatus. However, such fixed heterozygosity patternsare expected in some tetraploid species in which double disomicinheritance of alleles occurs. It is therefore not possibleto determine from population genetic structure analysis alonewhether segregation occurs or not. Here, we investigate thestability of such patterns over one generation of uniparentalreproduction among four populations. We also present resultsof crossing experiments between individuals from two populations,using two diagnostic loci to analyse their offspring. Our resultsclearly indicate Mendelian segregation of alleles, and confirmsexual reproduction by self-fertilization and cross-fertilization.We interpret the multibanded patterns observed in populationsas the product of both diploid loci of the tetraploid genomewhen they are monomorphic for different alleles. Our study alsoallows us to suggest that partial selfing may be the regularmating system in B. truncatus. (Received 12 February 1992; accepted 7 September 1992)     

ORGANIZATION AND ONTOGENY OF THE VASCULAR SYSTEM IN THE PETIOLE OF EASTERN COTTONWOOD

The topologic arrangement of petiolar bundles varies within the length of the cottonwood petiole. Each petiolar bundle is formed by the subdivision and aggregation of acropetally differentiating subsidiary bundles in a predictable pattern. The subsidiary bundles provide vascular continuity between the stem and specific portions of the leaf lamina. Spot-labeling of individual veins with ¹⁴CO₂, freeze substitution, and microautoradiography were used to establish the relation between the secondary veins of the lamina and the vasculature of the petiole. Within the petiole vasculature each subsidiary bundle was continuous with a specific portion of the lamina and seemed to have a separate function. Subsidiary bundles continuous with the central leaf trace were closely related functionally to the tip region of the lamina, while the subsidiary bundles continuous with the lateral leaf traces were functionally related to the middle and basal portions of the lamina.     

STRUCTURE AND ONTOGENY OF LATICIFERS IN CICHORIUM INTYBUS (COMPOSITAE)

The branched anastomosed laticifer system in the primary body of Cichorium intybus L. originates in embryos from files of laticiferous members at the boundary between phloic procambium and ground meristem. Upon seed germination, laticiferous members develop perforations in the end walls which become entirely resorbed. Perforations also develop in the longitudinal walls of contiguous laticiferous members and from lateral connections between developing laticifer branches. Additional laticiferous members originate as procambium differentiation proceeds, and their differentiation follows a continuous acropetal sequence in leaf primordia of the plumule. In roots, laticifers closely associated with sieve tubes in the secondary phloem originate from derivatives of fusiform initials in the vascular cambium. These laticifers develop wall perforations and in a mature condition resemble laticifers in the primary body. As the girth of the root increases, laticifers toward the periphery, unlike associated sieve tubes, resist crushing and obliteration. Laticifers vary in width from about 4 to 22 μm; the widest ones occur in involucral bracts and the narrowest ones in florets. There was no evidence that intrusive growth occurs during development of the laticifer system, although such growth may occur during development of occasional branches which extend through ground tissue independent of phloem and terminate in contact with the epidermis. Presence of amorphous callose deposits is related to aging of laticifers and mechanical injury.