Reproductive biology ofAwaous guamensis, an amphidromous Hawaiian goby

Synopsis Spawning season, size at first reproduction, oocyte maturation, and fecundity ofAwaous guamensis, an amphidromous Hawaiian goby, were studied from June 1989 through May 1991 in the Wainiha River, Kau'ai, Hawai'i. Female fish larger than 73 mm standard length (SL) had mature gonads from August through December in 1989 and 1990. Gonadosomatic index (GSI) values for mature females ranged from 0.2 to 14.5 during the spawning season. Male fish larger than 64 mm SL had elevated GSI values from June 1989 through December 1989 and from August 1990 through December 1990. Mature sperm were found in two male fish collected in January and February. GSI values for mature males ranged from less than 0.01 to 4.0 in the spawning season. Size-frequency distributions of measurements of vitellogenic oocyte diameters and microscopic observations of oocytes indicated this species has group-synchronous oocyte development. Ovarian maturation stages examined over a 29-month period suggest that members of the stock spawned at different times within the spawning season, although mass spawning events have been documented for this species. Estimates of clutch sizes from nests measured in situ were comparable to estimates of potential fecundity from in vitro examination of ovaries, and indicated that female fish deposited an entire clutch during a spawning event. No evidence for multiple spawning by an individual fish in a single season was found. However, microscopic observations of brown bodies in some ovaries suggested that individual fish probably spawn more than once in a lifetime.     

马先蒿属植物花冠分化与繁殖适应的研究进展

结合已有的研究报道和作者近年来的工作,对马先蒿属（Pedicularis）植物的花冠多样化成因与繁殖适应特性进行了总结和探讨。通过对该属4种进化花冠型的花器官发生和分化的研究发现,花部各器官在发生和发育初期基本一致,后期上唇形态的分化是导致成熟花形态结构产生较大差异的重要阶段。孢粉学研究认为,花冠类型与花粉萌发孔类型之间具有显著相关性;萌发沟的演化可能与繁殖适应有一定的关系。分子系统学研究表明,多样化的花冠类型在不同的谱系内经过若干次的独立进化而表现出了高度的平行演化（parallelism）。传粉生物学研究证实,该属植物花冠多样化与其主要传粉者熊蜂属（Bombus）昆虫的传粉行为存在较为密切的关系。具有相同（似）花冠类型的马先蒿可能被同种或不同种的熊蜂以相同的方式访问,但在花粉落置位置上存在显著差异,这可能有助于同域分布重叠的物种间在生殖上的机械隔离,而花冠的分化在一定程度上促进了新的物种形成。     

Asynchrony of DNA replication in the chromosomes of Luzula

Seedlings of Luzula purpurea (2n=6) were placed in contact with H³-thymidine for 30 minutes. After removal of the isotope the roots and leaf primordia were fixed at intervals between 0 and 14 hours. The percentage of labelled mitoses follows a very close curve in roots and leaf primordia. In both tissues the value of G₂ is approximately 3 to 4 hours and of S circa 8 hours. DNA replication in the chromosomes of L. purpurea is asynchronous. The discontinuous DNA synthesis discloses that Luzula chromosomes are composed of many segments replicating independently of each other. The results support a polycentric rather than a completely diffuse kinetochore system in this species.     

Authenticity and the Revitalization of Hawaiian

The process of language revitalization relies heavily on education in its broadest sense. That is, there must be a viable conduit for the transmission of communicative competence, and any individual who contributes to that process is an educator. This article deals with the responsibility of such educators with respect to the quality of the product they intend to transmit. In particular, they must address the issue of authenticity, especially in the case of Hawaiian in which the shift to English has almost run its full course. It is inevitable in efforts to recover and maintain a language in a community in which few competent speakers (experts) remain that competing opinions will arise as to the direction such efforts should take, each professing to be better informed than the other and each pointing to its link to traditional forms as verification of its authenticity.     

Nerve Cells and Insect Behavior--Studies on Crickets

Intraspecific acoustic communication during pair formation incrickets provides excellent material for neuroethological research.It permits analysis of a distinct behavior at its neuronal level.This top-down approach considers first the behavior in quantitativeterms, then searches for its computational rules (algorithms),and finally for neuronal implementations. The research described involves high resolution behavioral measurements,extra- and intracellular recordings, and marking and photoinactivationof single nerve cells. The research focuses on sound productionin male and phonotactic behavior in female crickets and itsunderlying neuronal basis. Segmental and plurisegmental organizationwithin the nervous system are examined as well as the validityof the single identified neuron approach. Neuroethological conceptssuch as central pattern generation, feedback control, commandneuron, and in particular, cellular correlates for sign stimuliused in conspecific song recognition and sound source localizationare discussed. Crickets are ideal insects for analyzing behavioralplasticity and the contributing nerve cells. This research continuesand extends the pioneering studies of the late Kenneth DavidRoeder on nerve cells and insect behavior by developing newtechniques in behavioral and single cell analysis.     

Asynchrony and Commitment to Die during Apoptosis

Time lapse video microscopy is used to study the chronology of morphological changes and commitment to die in individual PC12 cells after induction of apoptosis. Cell death is highly asynchronous occurring over a 2- to 3-day period following serum removal; however, all cells go through three characteristic morphological phases irrespective of the time they die following serum removal. During phase 1, which lasts from 2 to 44 h, cells maintain normal morphology. Phase 2 is characterized by plasma membrane bubbling which lasts from 10 min to 40 h. Phase 3 represents the active or execution phase of apoptosis and involves dynamic whole cell body blebbing. Phase 3/execution phase has a restricted duration, lasting 96 ± 5 min. At the end of the execution phase of apoptosis, cells die. The inherently asynchronous nature of cell death is still present in cells that are synchronized following mitosis. Daughter cells enter phase 2 synchronously but remain in phase 2 for varying periods and die at different times. Addition of serum 24–48 h after initiating apoptosis blocks death of 89% of cells in phase 1, 79% in phase 2, and 0% in phase 3. Serum rescue experiments are consistent with cells committing to die about 2–3 h prior to the onset of phase 3 (execution phase of apoptosis). These studies indicate that although apoptosis is an asynchronous process it can be defined in terms of reproducible morphological changes that can be used to place other events, such as the commitment to die, in a temporal sequence.     

Genetic Control of Acoustic Behavior in Crickets

Evidence is presented that acoustic behavior in field cricketsis under firm genetic control. The calling song of adult malesis highly stereotyped and species specific. Hybrids can be madeby crossing two species of Teleogryllus with dissimilar callingsongs. The calling songs of the hybrids are uniquely differentfrom that of either parental species, and in addition the songsof the two reciprocal hybrids are different from each other.Genetic control of song production is polygenic and multichromosomal;sex-linkage of some song determinants is also indicated. Femalephonoresponse to calling song was measured on a Y-maze. Speciesspecificity of phonoresponse was confirmed and in addition,hybrid females prefer hybrid song to either parental song. Thepossibility that calling song production in the male and itsreception in the female are genetically coupled is discussed.     

Reproductive Isolation with Little Genetic Divergence in Sympatric Populations of Brown Trout (SALMO TRUTTA)

Two reproductively isolated demes of brown trout coexist in a small Swedish mountain lake, Lake Bunnersj?rna. We electrophoretically examined 102 specimens from that lake for 27 enzymes encoded by 54 loci. The two demes are fixed for different alleles at a lactate dehydrogenase locus (LDH-1); statistically significant allele frequency differences at five other loci further support the complete lack of gene flow between these demes. There are significant differences in growth rates between fish in the two demes, but no further morphological differentiation h-s been detected.--In light of these findings, the genetic distance between these populations is surprisingly small (Nei's I = 0.975). These demes represent one of the least genetically divergent, reproductively isolated sympatric pair of vertebrate populations that have been identified. The results are discussed from both an evolutionary and ecological perspective.     

Where the Lake Meets the Sea: Strong Reproductive Isolation Is Associated with Adaptive Divergence between Lake Resident and Anadromous Three-Spined Sticklebacks

Contact zones between divergent forms of the same species are often characterised by high levels of phenotypic diversity over small geographic distances. What processes are involved in generating such high phenotypic diversity? One possibility is that introgression and recombination between divergent forms in contact zones results in greater phenotypic and genetic polymorphism. Alternatively, strong reproductive isolation between forms may maintain distinct phenotypes, preventing homogenisation by gene flow. Contact zones between divergent freshwater-resident and anadromous stickleback (Gasterosteus aculeatus L.) forms are numerous and common throughout the species distribution, offering an opportunity to examine these contrasting hypotheses in greater detail. This study reports on an interesting new contact zone located in a tidally influenced lake catchment in western Ireland, characterised by high polymorphism for lateral plate phenotypes. Using neutral and QTL-linked microsatellite markers, we tested whether the high diversity observed in this contact zone arose as a result of introgression or reproductive isolation between divergent forms: we found strong support for the latter hypothesis. Three phenotypic and genetic clusters were identified, consistent with two divergent resident forms and a distinct anadromous completely plated population that migrates in and out of the system. Given the strong neutral differentiation detected between all three morphotypes (mean F_ST = 0.12), we hypothesised that divergent selection between forms maintains reproductive isolation. We found a correlation between neutral genetic and adaptive genetic differentiation that support this. While strong associations between QTL linked markers and phenotypes were also observed in this wild population, our results support the suggestion that such associations may be more complex in some Atlantic populations compared to those in the Pacific. These findings provide an important foundation for future work investigating the dynamics of gene flow and adaptive divergence in this newly discovered stickleback contact zone.     

Crickets detect the genetic similarity of mating partners via cuticular hydrocarbons

Animals should decipher information about the genetic make‐up of conspecifics in order to enhance the fitness benefits associated with mate choice. Although there is increasing evidence to suggest that animals make genetically informed decisions about their mating partners, we understand relatively little about the sensory mechanisms informing these decisions. Here, we investigate whether cuticular hydrocarbons, chemical compounds found on the cuticle of most terrestrial arthropods, provide a means of discerning genetic similarity during mate choice in the cricket, Teleogryllus oceanicus. We found that individuals preferentially mated with partners who share more dissimilar cuticular hydrocarbon profiles and that similarity in cuticular hydrocarbon profiles between mating pairs correlated with their genetic similarity. Our results provide good evidence that cuticular hydrocarbon profiles offer a means of assessing genetic compatibility in T. oceanicus, enabling individuals to choose their most genetically suitable mate.     

Question of the Animal-Plant-Fungal Divergence

There has been a controversial issue in phylogenetic relationships among animals, fungi, and plants. Before Whittaker and Margulis (1) classified the fungi as a separate kingdom in their five-kingdom classification, fungi traditionally had been considered more closely related to plants than to animals. With the determination of the primary structures of small subunit rRNA and the proteins like actin and α-tubulin in various organisms, these sequences have been used to make molecular trees. Most of these studies show that fungi and animals are sister groups (2-4).     

Synchrony and Asynchrony in a Fully Stochastic Neural Network

We describe and analyze a model for a stochastic pulse-coupled neural network, in which the randomness in the model corresponds to synaptic failure and random external input. We show that the network can exhibit both synchronous and asynchronous behavior, and surprisingly, that there exists a range of parameters for which the network switches spontaneously between synchrony and asynchrony. We analyze the associated mean-field model and show that the switching parameter regime corresponds to a bistability in the mean field, and that the switches themselves correspond to rare events in the stochastic system.