Reproduction Strategy of the Deep-sea Hermit Crabs Pagurus alatus and Pagurus excavatus of the Central-Western Mediterranean Sea

Some aspects of the reproductive biology of two hermit crabs Pagurus alatus (Fabricius, 1775) and P. excavatus (Herbst, 1791) were studied. Specimens were collected monthly from April 2000 to March 2001 on the continental shelf and the upper-middle slope off the Southwestern coasts of Sardinia, in the central-western Mediterranean Sea. Crab size (minimum and maximum shield length) was 1.7 and 9.5 mm for 1150 females of P. alatus; 4.0 and 10.4 mm for 347 females of P. excavatus, respectively. Females of P. alatus with ripe ovaries were only found in February-April and ovigerous females were observed throughout the year except in March, with the highest incidence in summer. Females of P. excavatus with fully developed ovaries were collected during all months of the year reaching a peak from April to June. Ovigerous females of P. excavatus occurred throughout the year and the main spawning period occurred in March and April. Fecundity of both species was calculated to assess seasonal variation of reproductive intensity and was positively correlated with the size of the individuals. Monthly fecundity did not reveal significant differences in P. alatus ovigerous females, whereas P. excavatus exhibited significant differences in monthly fecundity depending on the time of year. Difference in fecundity among P. alatus and P. excavatus can be related to the size of the ovigerous females and species of hermit crab, but their different reproductive strategies suggest that they are specifically related to different environmental conditions.     

Sexual reproduction and crossing barriers in white pines: the case between <Emphasis Type="Italic">Pinus lambertiana</Emphasis> (sugar pine) and <Emphasis Type="Italic">P. monticola</Emphasis> (western white pine)

The sexual reproductive process in Pinus lambertiana has not been completely described, and previous attempts to generate hybrids with Pinus monticola and other North American pines have not been successful. The nature of incompatibility barriers between P. lambertiana and P. monticola is unknown. This needs to be understood if strategies are to be developed to overcome the said barriers. In this paper, development on interspecific crosses is compared with that on intraspecific crosses on the same parent trees. Pollen grains of both species germinated on the nucellus of both species within a week after pollination. Seed cone receptivity in P. lambertiana came approximately 2 weeks after receptivity in P. monticola, and this delay was perpetuated throughout ovule development in the first year of the reproductive process. Development of the second-year seed cones proceeded more gradually in P. lambertiana. However, seed cones reached maturity only for P. monticola x P. lambertiana. In both crosses, the barriers to hybridization occurred during the second year of the reproductive process. With the P. lambertiana as the seed parent, it was manifested through the failure of the megaspores at the free-nuclear stage to resume development. When P. monticola was used as the seed parent, the male and female gametes failed to fuse. Our results clearly show that the barriers to hybridization in these species occur before or at fertilization. However, the exact mechanisms behind these are still unknown. Based on the results of this study, we present several strategies to bypass the developmental barriers and possibly produce hybrid progenies.     

Reproductive biology of twoPrunus species (Rosaceae) in the Northwest Iberian Peninsula

We studied the reproductive biology ofPrunus spinosa andPrunus mahaleb (Prunoideae, Rosaceae) in the northwest Iberian Peninsula. The two species flowered at the same time (peaking on March 9 and 11, respectively in 1990) but differ significantly in their fruit maturation times. Nectar volume peaked in the early morning in both species, and was ten times greater inP. spinosa than inP. mahaleb. Neither species shows apomixis, nor does fruit-set occur if pollinators are excluded. In both species self-pollination resulted in fewer fruits than open pollination. The principal pollinators belong to theApidae family (79% and 63% of visits toP. spinosa andP. mahaleb, respectively). Results are compared with those for other rosaceous plants with fleshy fruits.     

An evaluation of species relationships in the Porphyra perforata complex (Bangiales,Rhodophyta) using starch gel electrophoresis

Traditional morphological features have formed the basis for distinguishing species of Porphyra. Among these features are number of cell layers, number of chloroplasts per cell, arrangement of reproductive structures on the thallus, and overall morphology. Chromosome number and chromosome morphology have helped corroborate some species identities. A survey of northeast Pacific species of Porphyra using starch gel electrophoresis of 15 soluble proteins has shown that electrophoretic banding patterns provide a reliable diagnostic tool for species identification. Data from starch gel electrophoresis are presented to confirm the identities of species formerly associated with the Porphyra perforata species-complex in British Columbia and northern Washington. Porphyra abbottae, P. fallax, P. kanakaensis, and P. torta are recognized as distinct species, and Porphyra sanjuanensis is synonymized with P. perforata.     

Spawning behavior and reproductive isolation of two species ofPseudolabrus

The reproductive behavior of two wrasses,Pseudolabrus eoethinus (Richardson, 1846) andP. sieboldi Mabuchi & Nakabo, 1997, was studied on a rocky coast in Shikoku, Japan, where the two species occur sympatrically. In the study area, individual males of each species established mating territories within which pair spawnings occurred. Pair spawnings were observed only between conspecifics, indicating that the two coexisting species were reproductively isolated. Both species usually spawned during the afternoon in early winter and had similar reproductive behavior. Although habitat, temporal and behavioral isolation mechanisms were not apparent, reproductive isolation seemed to occur via premating isolation through visual recognition of conspecific mates because the two species differed in body size and coloration. On one occasion a maleP. sieboldi was observed to perform streaking behavior to join a spawning pair ofP. eoethinus. Thus, postmating isolation between the two species is also discussed.     

Life-history traits of the six Panonychus species from Japan (Acari: Tetranychidae)

Six species of the genus Panonychus are known from Japan. Life-history parameters of all six species were investigated at 25 °C, and for three species two strains of different geographical origin were included. The intrinsic rate of natural increase (r _m ) ranged from 0.172/day for the P. osmanthi albino strain to 0.209/day for P. citri, while the net reproductive rate (R ₀) varied from 23.98 in the thelytokous species P. thelytokus to 46.61 in P. citri. Both values were higher in the polyphagous species (P. ulmi, P. mori and P. citri), which are considered crop pests, than those in the oligophagous species (P. thelytokus and P. osmanthi), considered non-pests. The only exception was P. bambusicola, an oligophagous non-pest species with R ₀- and r _m -values closely resembling those of the three polyphagous species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breeding system of the subantarctic plant species Pringlea antiscorbutica R. Br. and search for potential insect pollinators in the Kerguelen Islands

The reproductive biology of Pringlea antiscorbutica R. Br. (Brassicaceae), an endemic species from the southern Indian Ocean islands, is investigated here. Controlled crosses were performed between plants grown in a common garden on the Kerguelen Islands. Searching for potential insect pollinators, we investigated the flying ability of all insects known from the Kerguelen Islands. We showed evidence for self-compatibility, low pollen limitation in the absence of a biotic pollen vector and slight selfing depression in P. antiscorbutica. The insects present on the islands are mostly wingless and are not likely to be efficient pollinators of this species. Since P. antiscorbutica shows morphological adaptations to insect pollination despite the absence of pollinators in its present range, we conclude that this species recently evolved from insect pollination to wind and/or autonomous pollination.     

Interspecific pollen transfer as a mechanism of competition: Consequences of foreign pollen contamination for seed set in the alpine wildflower,Polemonium viscosum

Summary Earlier studies showed that under natural conditions foreign pollen receipt is correlated with loss of seed set in populations of P. viscosum. Here, we report on experimental pollinations using foreign pollen from two co-flowering species that share pollinators with P. viscosum. Experiments were designed to ascertain whether improper pollen transfer causes reduced seed set under controlled conditions and, if so, to determine the stage at which interference occurs. In flowers pre-treated by pollination with either Mertensia or Castilleja pollen, adherence of subsequently deposited conspecific pollen grains was unaffected. However, conspecific grains had significantly lower germination and ovule fertilization success in flowers receiving foreign pollen than in controls. These results suggest that pollinator infidelity in high alpine plant communities can reduce female reproductive success of P. viscosum by inhibiting the performance of conspecific pollen grains. Negative effects of Mertensia and Castilleja pollen were comparable despite large interspecific differences in pollen grain morphology. Accordingly, susceptibility to foreign pollen interference appears to be an intrinsic property of P. viscosum that is not dependent on the unique structural properties of pollen produced by competitive species.     

竹亚科单枝竹属芸香竹花枝和花特征补充描述

繁殖器官在竹类植物的分类学研究中具有重要意义,研究组在广西马山县观察到竹亚科单枝竹属芸香竹正在开花,该文根据观察到的开花状况和采集到的标本解剖观察结果,对其花枝和繁殖器官特征做了详细的中文及拉丁文补充描述。经对比芸香竹与属内已知繁殖器官结构的单枝竹和小花单枝竹的繁殖器官,3个竹种有相同的繁殖器官结构特征,但在小花数目和大小等方面具有差异。繁殖器官比较表明该属竹种的繁殖器官对喀斯特地貌环境有特殊的适应性,也支持依据营养器官差异划分为3个独立竹种。     

Distribution of sawfishes (Pristidae) in the Queensland Gulf of Carpentaria,Australia, with notes on sawfish ecology

Synopsis Pristis microdon, P. zijsron, P. clavata and Anoxypristis cuspidata are distributed throughout the Queensland section of the Gulf of Carpentaria, Australia. In a survey of the four species, Anoxypristis cuspidata was the most abundant and was recorded in both the inshore and offshore set net fisheries. The size distribution and catch locations of A. cuspidata suggest that the inshore area to a depth of 10 m may be the preferred habitat for juveniles of this species, while adults primarily occur offshore. Pristis microdon, P. zijsron and P. clavata were recorded only in the inshore fishery with catches dominated by immature animals. Pristis microdon was caught in the inshore fishery late in the monsoonal wet season (February to April) and inhabited both freshwater and estuarine environments. Pristis zijsron occurred only on the sand and mud flats outside river mouths whilst P. clavata inhabited both the sand and mud flats and upstream estuarine habitats. Observations on reproductive staging and the capture of neonate specimens suggest that in all four pristids, pupping occurred through the wet season until the beginning of the dry season in May. A seasonal set net closure for the barramundi, Lates calcarifer and shark fisheries, which has been in place since 1980 in Queensland Gulf waters, therefore offers a measure of protection to breeding female sawfish and their offspring.     

Competition and parasitism in the native White Clawed Crayfish Austropotamobius pallipes and the invasive Signal Crayfish Pacifastacus leniusculus in the UK

Many crayfish species have been introduced to novel habitats worldwide, often threatening extinction of native species. Here we investigate competitive interactions and parasite infections in the native Austropotamobius pallipes and the invasive Pacifastacus leniusculus from single and mixed species populations in the UK. We found A. pallipes individuals to be significantly smaller in mixed compared to single species populations; conversely P. leniusculus individuals were larger in mixed than in single species populations. Our data provide no support for reproductive interference as a mechanism of competitive displacement and instead suggest competitive exclusion of A. pallipes from refuges by P. leniusculus leading to differential predation. We screened 52 P. leniusculus and 12 A. pallipes for microsporidian infection using PCR. We present the first molecular confirmation of Thelohania contejeani in the native A. pallipes; in addition, we provide the first evidence for T. contejeani in the invasive P. leniusculus. Three novel parasite sequences were also isolated from P. leniusculus with an overall prevalence of microsporidian infection of 38% within this species; we discuss the identity of and the similarity between these three novel sequences. We also screened a subset of fifteen P. leniusculus and three A. pallipes for Aphanomyces astaci, the causative agent of crayfish plague and for the protistan crayfish parasite Psorospermium haeckeli. We found no evidence for infection by either agent in any of the crayfish screened. The high prevalence of microsporidian parasites and occurrence of shared T. contejeani infection lead us to propose that future studies should consider the impact of these parasites on native and invasive host fitness and their potential effects upon the dynamics of native-invader systems.     

Genetics of flower size and nectar volume in Petunia pollination syndromes

The two related Petunia species, P. axillaris and P. integrifolia, are sympatric at various locations in South America but do not hybridise. Divergent pollinator preferences are believed to be in part responsible for their reproductive isolation. The volume of nectar produced and several components of flower morphology might contribute to pollinator-dependant reproductive isolation. In this study, we aimed to identify the genetic changes underlying the quantitative differences observed between these two Petunia species in flower size and nectar volume. We mapped quantitative trait loci (QTL) responsible for the different phenotypes of P. axillaris and P. integrifolia in an inter-specific backcross population. QTL of small to moderate effect control the differences in flower size and volume of nectar. In addition, we observed strong suppression of meiotic recombination in Petunia, even between closely related species, which precluded a fine resolution of QTL mapping. Thus, our data suggest that flower size and nectar volume are highly polygenic. They are likely to have evolved gradually through pollinator-mediated adaptation or reinforcement, and are not likely to have been primary factors in early steps of pollinator isolation of P. axillaris and P. integrifolia.     

不同生境下景宁玉兰灌丛萌株形态及其生殖特征

景宁玉兰是萌生能力很强的灌木树种,为了解不同生境下景宁玉兰萌枝形态及其生殖特征,选择了灌丛(SH)、黄山松林(PTF)、落叶阔叶林(DBF)、杉木林(CLF)和林缘(FE)等5种坡向一致的生境类型,通过典型样地调查,比较分析了5种不同生境下景宁玉兰萌枝数量、大小、高度、枝系、开花及结实等性状。结果表明:(1)景宁玉兰在黄山松林下的分布密度最高,但5种生境下景宁玉兰每丛的萌枝数量没有差异,每丛最大萌枝基径对每丛萌枝数有一定影响,但最大萌枝高度与每丛萌枝数没有关系。在所有调查的景宁玉兰居群中,大于2根以上萌枝的灌丛达82.5%,说明萌生更新在种群繁衍中发挥着重要作用。(2)在落叶阔叶林下的萌枝基径显著小于其他生境(P0.05),黄山松林下一级枝粗度和长度显著小于其他生境(P0.05);灌丛中的总分枝率和逐步分枝率最高,灌丛和林缘生境的逐步分枝率(SBR2:3)高于其他生境。(3)生殖萌枝基径(r=0.320,P0.05)和高度(r=0.349,P0.05)与花量均呈显著正相关关系。杉木林下景宁玉兰生殖萌枝的花量显著高于黄山松林、落叶阔叶林和林缘生境(P0.05)。虽然黄山松林下景宁玉兰萌枝开花率及开花萌枝比例最低,但其果实大小、单果种子粒数及每丛结实率却较高(P0.05),(4)景宁玉兰对环境变化极为敏感,生境类型和海拔对萌枝形态和生殖性状均有一定影响。研究表明,景宁玉兰萌生特征主要受其内在生物学特性所控制,而萌枝形态及生殖特征则与其所处环境条件更为密切。     

Comparative analysis of the reproductive biology of two Peristenus species (Hymenoptera: Braconidae), biological control agents of Lygus plant bugs (Hemiptera: Miridae)

Peristenus digoneutis Loan and Peristenus stygicus Loan, parasitoids of the European tarnished plant bug Lygus rugulipennis Poppius, are established in the United States for biological control of native North American Lygus species, and are being considered for deliberate release in Canada. High lifetime fecundity of parasitoids is considered a desirable attribute of biological control agents and therefore, an understanding of parasitoid reproductive biology is required. In the present study, the potential lifetime fecundity of both agents was compared under laboratory conditions to estimate the potential impact of Peristenus species on Lygus. Synovigenic P. digoneutis and P. stygicus females oviposited most actively in the first two weeks of their lifetime, with a maximum average daily oviposition rate after five days. The maximum number of eggs laid per day was 83 eggs for P. stygicus, and 36 eggs for P. digoneutis. P. digoneutis has an average potential lifetime fecundity of 385 ± 35 SE eggs produced over 22 ± 3 SE days. In contrast, P. stygicus females have a 50% higher mean potential lifetime fecundity reaching 782 ± 65 SE eggs over 28 ± 1 SE days. A positive correlation between lifetime fecundity and body size was found only for P. stygicus, and both species showed a significant relationship between lifetime fecundity and oviposition period. The present study demonstrates that the fecundity of P. digoneutis and P. stygicus is considerably higher than previously reported. Based on these findings, P. stygicus appears to be the most effective biological control agent for Lygus lineolaris (Palisot de Beauvois) when only fecundity is taken into consideration.     

Inter-Specific Differences in Cotton for Nutrient Partitioning from Subtending Leaves to Reproductive Parts at Various Developmental Stages: Consequences for Fruit Growth and Yield

A field study was carried out to unravel the inter-specific differences in cotton for the partitioning of N, P, K, S, Ca, Mg, Na and Cl from the subtending leaves to the reproductive parts of Gossypium hirsutum, G. barbadense and G. arboreum at various developmental stages. Results revealed significant differences among the species for the various parameters studied. Overall there was a greater fresh and dry matter yield of various reproductive parts and subtending leaves of G. hirsutum and G. barbadense than G. arboreum, although the leaf photosynthetic rate was similar. Age-dependent increase in leaf area/leaf mass ratio indicated a greater partitioning of earlier acquired assimilates to the growth of reproductive parts. Results indicated greater partitioning of N, P, S and Ca during later reproductive growth (from boll production to its opening) in G. hirsutum and G. barbadense but during earlier reproductive growth in G. arboreum (from bud up to flower formation) as was evident by decreased subtending leaf/reproductive parts ratio. It is concluded that better N, P, S and Ca partitioning ability of G. hirsutum and G. barbadense at the onset of boll development played a major role in the better yield and good quality fiber characteristics. This revised version was published online in July 2006 with corrections to the Cover Date.     

牛耳朵传粉生物学研究

苦苣苔科(Gesneriaceae)报春苣苔属(Primulina Hance)是一个近年来备受关注的类群,其纷繁复杂的物种多样性和属下种间的特有分布引起了分类学家和植物学研究者的极大兴趣。该属除了极少数的物种如牛耳朵[(Primulina eburnea (Hance) Y. Z. Wang)]以外,绝大部分的物种为狭域分布或地方特有种,其分布范围很窄。为了揭示牛耳朵的传粉生物学和繁育系统对其生殖过程和拓殖能力的影响机制,作者系统地研究了牛耳朵的开花物候、花粉与柱头活性、访花昆虫的种类和访花行为、花粉胚珠比、OCI指数和套袋实验结实率,探究其传粉等生殖过程对牛耳朵的广布是否有正面影响。结果表明:牛耳朵的自然花期是3—5月,全花期约45 d,其中盛花期约20 d,单花期6～8 d;开花后1～2 d花粉活力最强,开花前柱头没有可授性;花粉胚珠比为537;杂交指数为5;去雌套袋、去雄套袋均无法结实,说明本种不存在无融合生殖;与自然授粉相比,自花授粉结实率略低,异花授粉结实率略高,说明自交亲和;牛耳朵的主要传粉者是花条蜂(Anthophora florea)和熊蜂(Bombus sp.)。花蜜产量较高、花粉量较大、花粉活力较强等特点,有利于牛耳朵完成传粉和结实的整个繁殖过程。因此,这一结果显然有利于牛耳朵的拓殖进而广布在我国华南至西南地区的喀斯特地区。     

牛耳朵传粉生物学研究

苦苣苔科(Gesneriaceae)报春苣苔属(Primulina Hance)是一个近年来备受关注的类群,其纷繁复杂的物种多样性和属下种间的特有分布引起了分类学家和植物学研究者的极大兴趣。该属除了极少数的物种如牛耳朵[(Primulina eburnea(Hance)Y. Z. Wang)]以外,绝大部分的物种为狭域分布或地方特有种,其分布范围很窄。为了揭示牛耳朵的传粉生物学和繁育系统对其生殖过程和拓殖能力的影响机制,作者系统地研究了牛耳朵的开花物候、花粉与柱头活性、访花昆虫的种类和访花行为、花粉胚珠比、OCI指数和套袋实验结实率,探究其传粉等生殖过程对牛耳朵的广布是否有正面影响。结果表明:牛耳朵的自然花期是3—5月,全花期约45 d,其中盛花期约20 d,单花期6～8 d; 开花后1～2 d花粉活力最强,开花前柱头没有可授性; 花粉胚珠比为537; 杂交指数为5; 去雌套袋、去雄套袋均无法结实,说明本种不存在无融合生殖; 与自然授粉相比,自花授粉结实率略低,异花授粉结实率略高,说明自交亲和; 牛耳朵的主要传粉者是花条蜂(Anthophora florea)和熊蜂(Bombus sp.)。花蜜产量较高、花粉量较大、花粉活力较强等特点,有利于牛耳朵完成传粉和结实的整个繁殖过程。因此,这一结果显然有利于牛耳朵的拓殖进而广布在我国华南至西南地区的喀斯特地区。     

The interspecific hybrid Petunia parodii × P. inflata and its relevance to somatic hybridization in the genus Petunia

Summary Attempts at the reciprocal cross between Petunia parodii and P. inflata using standard emasculation and pollination techniques failed. Limited pollen tube growth down the style in reciprocal crosses led to reproductive isolation between the self-compatible P. parodii and self-incompatible P. inflata. The interspecific hybrid was successfully produced by bud-pollination of P. parodii with P. inflata as the male parent in 22 percent of attempts, but not in the opposite direction. In vitro pollination of P. parodii ovaries with P. inflata pollen also produced hybrids. The small size of the ovary made it technically impossible to use P. inflata as the female parent for in vitro pollination. The interspecific hybrids were intermediate, as compared to the two parents, for six of the seven plant and flower characters measured. Furthermore, the hybrids had high pollen fertility, set abundant seed upon self-pollination, and readily inter-crossed with the parental species. The results are consistent with a high degree of chromosomal homology in the parental species and with minor genetic divergency leading to reproductive isolation that is pre-zygotic in nature. Overcoming the barriers to cross-incompatibility by practical techniques resulted in fertile interspecific hybrids that segregated for parental characters. The potential value of employing the parental species in somatic hybridization experiments is discussed.Michigan Agricultural Experiment Station Journal Article No. 8404     

The reproductive biology of Pellonula afzeliusi Johnels,and Sierrathrissa leonensis thys Audenaerde in Lake Kainji,Nigeria

Aspects of the reproductive biology of the two species of clupeids known to occur in Lake Kainji, Pellonula afzeliusi Johnels and Sierrathrissa leonensis Thys Van Den Audenaerde were studied for a period of twenty eight months. Mature individuals were found in both species all the year round but with a prolonged peak of activity from December to May, more distinct in P. afzeliusi than in S. leonensis.There were no significant length differences between mature males and females in both species. The smallest mature individuals were 28 mm standard length female; 27 mm standard length male in P. afzeliusi, while the corresponding figures for S. leonensis were 18 mm standard length female and 19 mm standard length male.No sexual dimorphism was observed. There was a simple correlation between fecundity and fish standard body length as well as weight in both species.     

A laboratory study on the demography and competition of three species of littoral cladocerans from Lake Huetzalin,Xochimilco, Mexico

Lake Huetzalin (Xochimilco) is a shallow waterbody in Mexico City with a dominance of the littoral cladocerans Simocephalus vetulus, Alona rectangula, and Pleuroxus aduncus. Here, we present data on the life table and population dynamics of these three cladoceran species on two types of diets (alga Scenedesmus acutus and detritus). We also analyzed the effect of competition on population growth using Scenedesmus, which proved to be the better diet than detritus. We hypothesize that feces of the larger cladoceran species (S. vetulus) could be a food source for the smaller taxa (A. rectangula and P. aduncus). Experiments were conducted in 100 ml beakers with 50 ml of medium in each at a temperature of 23 ± 1°C. We studied the demography of three test species using two food types with four replicates for each treatment in the life table experiments. Based on the data thus obtained we further studied the competition between the cladocerans on a diet of Scenedesmus. The maximal growth rates obtained for P. aduncus, S. vetulus, and A. rectangula fed Scenedesmus acutus were: 0.1, 0.3, and 0.5 d⁻¹, respectively. Among the test species, S. vetulus had the highest survivorship of 77 days when cultured on detritus and P. aduncus the lowest of 20 days on Scenedesmus. The gross reproductive rate (offspring female⁻¹ lifespan⁻¹) ranged from 6 neonates in Pleuroxus to 160 in Simocephalus per female. From the competition experiments conducted using alga as the diet, we observed that A. rectangula and, especially P. aduncus, had higher growth rates in the presence of S. vetulus than in the controls. This facilitation could be one of the reasons for higher species diversity in the littoral of water bodies.