Effects of resource availability on the trade-off between seed and vegetative reproduction

Aims To explore whether the trade-off between seed and vegetative reproductive modes is flexible in environments with different amounts of available resources to maintain optimal behaviors.Methods A transition matrix model was established to determine the optimal trade-off between seed and vegetative reproduction in resources–variable habitats.Important findings The model predicts that plants allocate more resources to seed reproduction when available resources are scarce. With increasing resources, more vegetative propagules are produced. However, if resources keep increasing to a harmful level, plants would switch to seeds again.     

甘草有性生殖特性研究

本文利用扫描电子显微镜对乌拉尔甘草、光果甘草和胀果甘草花粉的超微结构进行观察;利用荧光显微镜确定乌拉尔甘草的授粉方式、花粉生活力和柱头活性以及授粉后受精时间。结果表明花粉超微结构为甘草的鉴别提供了一定的形态学依据;甘草的授粉方式属于闭花受精;花粉生活力在每天12:00时最强,去雄后超过四天的柱头已经不具备接受花粉的能力;对授粉后不同时间的雌蕊进行研究得出授粉后6h花粉管进入胚珠进行受精。本文主要对甘草的有性生殖特性进行了研究,为未来制定正确的选、育种策略提供理论依据。     

甘草有性生殖特性研究

本文利用扫描电子显微镜对乌拉尔甘草、光果甘草和胀果甘草花粉的超微结构进行观察;利用荧光显微镜确定乌拉尔甘草的授粉方式、花粉生活力和柱头活性以及授粉后受精时间。结果表明花粉超微结构为甘草的鉴别提供了一定的形态学依据;甘草的授粉方式属于闭花受精;花粉生活力在每天12:00时最强,去雄后超过四天的柱头已经不具备接受花粉的能力;对授粉后不同时间的雌蕊进行研究得出授粉后6h花粉管进入胚珠进行受精。本文主要对甘草的有性生殖特性进行了研究,为未来制定正确的选、育种策略提供理论依据。     

半夏的繁殖生物学研究

对“泰半夏”（Ｐｉｎｅｌｌｉａｔｅｒｎａｔａ（Ｔｈｕｎｂ．）Ｂｒｅｉｔ．）的块茎和珠芽栽培观察结果表明：（１）不同繁殖体的叶形和珠芽所发生的变化与实验用的播种材料有关,珠芽发生频率与叶形变化呈正相关;（２）半夏倒苗既是对不利环境条件的一种适应,也是一种有效的无性繁殖方式;（３）半夏有性繁殖是属于同株异花传粉类型,但与无性繁殖相比,有性繁殖在种质繁衍上仅起着次要作用。     

A Brief Report on the Chromosome Number of Neodiplogaster pinicola and Panagrellus redivivoides (Nematoda: Rhabditida)

Both Neodiplogaster pinicola and Panagrellus redivivoides reproduce amphimictically, with XO type of sex determination. In N. pinicola, primary spermatocytes have six bivalent chromosomes and one univalent; after two meiotic divisions, sperm are produced with either six or seven chromosomes. In primary oocytes, with seven bivalents, meiosis is initiated by entrance of a sperm. After two meiotic divisions, three polar nuclei are produced, and egg and sperm pronuclei fuse. Cleavage begins after the egg is laid. Males have a 2n number of 13 chromosomes; females, 14. In P. redivivoides, primary spermatocytes have four bivalents and one univalent. After two meiotic divisions, spermatids are produced with either four or five well separated chromosomes. In primary oocytes, the first maturation division is initiated after penetration of a sperm; after two meiotic divisions, each egg has five chromosomes. Cleavage begins immediately after fusion of egg and sperm pronuclei, and embryonic development and hatching occur within the uterus. Males have a 2n chromosome number of 9; females, 10.     

Commerson's dolphin (Cephalorhynchus commersonii): A discussion of the first live birth within a marine zoological park

Six adult Commerson's dolphins (Cephalorhynchus commersonii) have been housed at Sea World, San Diego, since 1983. Details of their husbandry at Sea World are briefly presented. Pregnancy was determined in one of the females by means of radioimmunoassay, following observations of copulation. Food consumption of the pregnant female decreased beginning 5 days prior to parturition and ceased entirely 6 hours prior to delivery. A single male calf, 55–65 cm in length and weighing 4.5–5.5 kg, was delivered after 35 minutes of labor. Details of the delivery, calf's appearance, suckling behavior, and early respiratory pattern are presented. Similarities between the birth of the Commerson's dolphin calf and previous births of bottlenosed dolphin (Tursiops truncatus) calves are discussed. The successful propagation of new species, such as Commerson's dolphins, permits documentation of the event with greater detail and accuracy than is possible in the wild. Details of growth and reproduction thus gained may provide information applicable to the natural history and proper management of the species in question.     

污染土壤生物恢复技术

污染土壤生物恢复技术张春桂许华夏姜晴楠（中国科学院沈阳应用生态研究所,１１００１５）ＢｉｏｒｅｍｅｄｉａｔｉｏｎｏｆＣｏｎｔａｍｉｎａｔｅｄＳｏｉｌ．ＺｈａｎｇＣｈｕｎｇｕｉ,ＸｕＨｕａｘｉａ,ＪｉａｎｇＱｉｎｇｎａｎ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐ...     

Presence of pregnant females of the Gorgona guitarfish,Pseudobatos prahli,in the Mexican tropical Pacific

Five specimens (four females and one male) of the Gorgona guitarfish, Pseudobatos prahli, were sighted during two dives carried out off the western Gulf of Tehuantepec. This document describes the reproductive condition of three adult females captured, two of which had uterine eggs, whereas one had embryos. The sighting and capture of specimens occurred during two Tehuano wind events; the authors, therefore, believe that variations in temperature and dissolved oxygen could have affected P. prahli, leading it to carry out temporal migrations towards coastal shallow waters.     

Modeling the impact of reproductive mode on masting

Masting is defined as the intermittent highly variable production of seed in a plant population. According to reproductive modes, that is, sexual and asexual reproduction, masting species can be separated into three groups, that is, (1) species, for example, bamboo, flower only once before they die; (2) species, for example, Fagus, reproduce sexually; and (3) species, for example, Stipa tenacissima, reproduce both sexually and asexually. Several theories have been proposed to explore the underlying mechanisms of masting. However, to our knowledge, no theory has been found to explain the mechanism of masting species that reproduce both sexually and asexually. Here we refine the Resource Budget Model by considering a trade‐off between sexual and asexual reproduction. Besides the depletion efficient (i.e., the ratio of the cost of seed setting and the cost of flowering), other factors, such as the annual remaining resource (i.e., the rest of the resource from the photosynthetic activity after allocating to growth and maintenance), the trade‐off between sexual and asexual reproduction, and the reproductive thresholds, also affect masting. Moreover, two potential reproductive strategies are found to explain the mechanisms: (1) When the annual remaining resource is relatively low, plants reproduce asexually and a part of the resource is accumulated as the cost of asexual reproduction is less than the annual remaining resource. Plants flower and set fruits once the accumulated resource exceeds the threshold of sexual reproduction; (2) when the annual remaining resource is relatively high, and the accumulated resource surpasses the threshold of sexual reproduction, masting occurs. Remarkably, under certain depletion efficient, more investigation in sexual reproduction will lead plants to reproduce periodically. Additionally, plants investigate less resource to reproduce periodically when depletion efficient keeps increasing as plants can reproduce efficiently. Overall, our study provides new insights into the interpretation of masting, especially for species that reproduce both sexually and asexually.     

Variability of uterine cervical anatomy in the white-tailed gnu (Connochaetes gnou)

Examination of the reproductive anatomy of six female white-tailed gnu revealed duplex uterus with varying degrees of cervical division. The division ranged from 36 to 100% of the length of the cervix, with one animal exhibiting double external ossa. This variability in reproductive anatomy could be important in artificial insemination or embryo transfer procedures in this species.     

Estimation of the relative importance of sexual and vegetative reproduction in the clonal woodland herb Anemone nemorosa

Anemone nemorosa is a perennial rhizomatous plant of European woodlands. The “probability of clonal identity” method estimated the relative proportion of sexual to vegetative reproduction in this species to be 4.4% from allozyme genotype distributions. This result is congruent with investigations on the germination, short-term demography, population genetics, and breeding system of this species, and supports the hypothesis that even low levels of seedling recruitment can maintain considerable intrapopulational genetic diversity. Received: 2 March 1998 / Accepted: 24 July 1998     

Reproduction of macrourids in the upper slope of the north-western Ionian Sea

Aspects of reproduction of macrourid fish in the north-western Ionian Sea are reported. Data were collected during 12 trawl surveys carried out between 1993 and 1995. Mature and running ripe females of Coelorhynchus coelorhynchus, Hymenocephalus italiens and Nezumia sclerorhynchus were found all year round. Mature females of Trachyrhynchus trachyrhynchus were found mainly in August.     

Mating patterns of first-generation hybrids of the roach, <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.), and the silver bream, <Emphasis Type="Italic">Blicca bjoerkna</Emphasis> (L.)

Mating patterns among first-generation hybrids of the roach, Rutilus rutilus, and the silver bream, Blicca bjoerkna, between hybrids or with parent-species males, have been investigated under experimental reproduction conditions. The results reveal that the level of sexual activity of these hybrids is high. Hybrid females mated simultaneously and successively with all types of male, resulting in fertilised eggs. Individual participation of roach males in mating was never observed, however.     

The breeding of great apes at the Jersey Wildlife Preservation Trust and a look into the future

Details of breeding orangutans and gorillas at the Jersey Wildlife Preservation Trust are reviewed, with special reference to the diversity of managerial requirements and reproductive parameters for the two species of great apes represented. The importance of recording and publishing as much data as possible to provide important guidelines for others involved with the same or related species in captivity, as well as such information contributing directly to conservation in the wild, is underlined. The Jersey Trust's involvement with cooperative and coordinated breeding programs for the two species on both a national and international basis is reported, and prospects for future long-term management strategies are outlined.     

Morphology of the female reproductive system and reproductive cycle of the mangrove land crab Ucides cordatus (L.) in the Baía de Antonina,Paraná, Brazil

Ucides cordatus is a species of considerable ecological and socioeconomic importance. The goal of this study is to contribute to the understanding of the reproduction biology of this species by describing the macroscopic anatomy, the histology of the female reproductive system and the reproductive cycle of U. cordatus. A total of 367 females were obtained from October of 2002 to March of 2005 during monthly collections in the Baía de Antonina, Paraná, Brazil. Specimens were submitted to necropsy and their reproductive systems (ovary and spermathecae) were analysed histologically. Permanent slides were stained with Harris' hematoxylin and eosin, Mallory's trichromic and the periodic acid‐Schiff reaction. Ovarian analysis allowed for the determination of five developmental stages based on the prevalence of oocytes in different phases of vitellogenesis. During stage V, when ovaries recover from spawning, the presence of oocytes in advanced stages of vitellogenesis was detected, suggesting that there could be more than one spawning in a single reproductive period. Females in stage IV were most common in the spring (November through February), whereas females with their egg mass exposed were most frequent from November through March. The reproductive period of U. cordatus in mangroves of the study region occurred from October to March. The reproductive events observed in the present study suggest that spermatophores acquired during copulation, which takes place during the ‘andada’, are only used in the reproductive period of the following year.     

Geographic parthenogenesis and the common tea‐tree stick insect of New Zealand

Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction.     

Morphological relationships and leukocyte influence on steroid production in the epigonal organ-ovary complex of the skate, Leucoraja erinacea

In elasmobranchs, a unique association exists between an immune tissue, the epigonal organ (EO), and the gonads. In this study, the histological and vascular relationships of the EO and ovarian follicles of the little skate, Leucoraja erinacea, were assessed. Perfusions of Evans blue dye and Batson's monomer showed a shared vascular pathway from the gonadal artery into the epigonal-ovary complex, with blood first entering the EO and then perfusing the ovarian follicles. Histological studies demonstrated direct cellular contact between epigonal leukocytes and the follicle wall (FW), as well as the presence of leukocytes between the steroidogenic theca and granulosa cells. In vitro analyses demonstrated that epigonal cells co-cultured with FW cells cause a dose-dependent inhibition of estrogen (E2) and testosterone (T) production. In contrast, conditioned media from epigonal leukocytes, stimulated or unstimulated with lipopolysaccharide (10 microg/ml), increase the production of E2 and T from FW cells of the ovaries. These studies provide a basis for further investigations of leukocyte secreted factors and cell contact modulation of follicular steroid production.     

A survey of the reproductive biology in Italian branchiopods

A survey of the most important aspects of the reproductive biology of Lepidurus apus lubbocki Brauer, 1873 (Notostraca) is presented. Gametogenesis, germ cell distribution, and somatic tract structure of the male gonad are studied by means of TEM and SEM. The most important data emerging from our observations is the total and widespread degeneration of the sperms. We discuss the real functionality of male germ cells, and the implications on sexuality and reproductive strategies. On the whole, present ultrastructural observations suggest that males of Lepidurus apus lubbocki are not functional. Therefore, we suggest that this form reproduces parthenogenetically as the functional female gonad lacks any associated testicular cells. For comparison, we analyzed the male portion of the hermaphroditic gonad of Triops longicaudatus (LeConte, 1846) from California. In this case functionallity of the testis lobes and sperm were readily apparent.     

Heterozygosity and fitness in a California population of the labyrinth spider Metepeira ventura (Araneae, Araneidae)

Abstract. The relationship between individual heterozygosity and characteristics likely to be associated with fitness was investigated in the labyrinth spider Metepeira ventura . Adult females and their egg sacs were collected at a coastal site in southern California, and three measures of bodily condition (carapace width, weight, residual index) and six measures of reproductive output (number of egg sacs, variation in egg number among sacs [coefficient of variation], total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were determined for each spider. The sample was polymorphic at three allozyme loci that were in Hardy–Weinberg equilibrium, and individual females were heterozygous at up to two of the three loci, forming three heterozygosity classes (0, 1, and 2). None of the bodily condition measures were significantly related to the number of heterozygous loci, while four of the reproductive output estimators (total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were significantly influenced by heterozygosity. In each significant case, values for class 2 females were less than those for class 0 and 1 females, whose values were usually more similar. Thus, while female bodily condition was comparable among classes, the most heterozygous females produced fewer total eggs and eggs per sac than their less heterozygous peers. The fact that females of M. ventura engage in a reproductive investment-number trade-off suggests that high-variability and low-variability females may be pursuing distinct reproductive strategies in the wild, with more heterozygous females being K -selected (smaller clutches, heavier eggs) and more homozygous females being r -selected (larger clutches, lighter eggs). Further investigation will be needed to assess more fully the fitness value of heterozygosity in M. ventura .     

Relative growth and morphological sexual maturity of the mangrove crab Aratus pisonii (H. Milne Edwards, 1837) (Decapoda,Brachyura, Sesarmidae) on the southern coast of the state of São Paulo,Brazil

Growth in crustaceans is characterized by ontogenetic differentiation during the development of their body structures, so studies on relative growth are widely applied in this group. In this study, the growth pattern of the body structures was verified through the analysis of relative growth, and then, morphological sexual maturity of the mangrove crab Aratus pisonii (H. Milne Edwards, 1837) was estimated. The carapace width (CW), cheliped propodus length (PL), cheliped propodus height (PH), propodus width (PW), abdomen width (AW), and first pleopod length (FPL) of the crabs were measured. The relationships that best showed changes in the allometric coefficient among demographic categories were FPL vs. CW for males and AW vs. CW for females. This study verified the increased size of the cheliped in terms of length, width, and height, which occurred mainly in adult males. This increase reflects the importance of this structure in the reproductive processes of A. pisonii. For females, the increase in abdomen growth reflects their reproductive potential, since it is a structure that provides protection for eggs.