Signification of the sexualizing substance produced by the sexualized planarians

Asexual worms of an exclusively fissiparous strain (the OH strain) of the planarian Dugesia ryukyuensis keep developing hermaphroditic reproductive organs and eventually undergo sexual reproduction instead of asexual reproduction, namely fission, if they are fed with sexually mature worms of an exclusively oviparous planarian, Bdellocephala brunnea, suggesting that the sexually mature worms has a sexualizing substance(s). The fully sexualized worms no longer need the feeding on sexual worms to maintain the sexuality. Here, we demonstrate that the sexualized worms produce enough of their own sexualizing substance similar to that contained in B. brunnea. In case of surgical ablation of the sexualized worms, the fragments with sexual organs regenerate to become sexual, while those without sexual organs, namely head fragments, regenerate to return to the asexual state. The asexual regenerants from the sexualized worms are also fully sexualized by being fed with B. brunnea. Additionally, it was reported that head region in sexually mature worms lacks the putative sexualizing substance necessary for complete sexualization (Sakurai, 1981). These results suggest that the fragments without sexual organ lack enough of an amount of the putative sexualizing substance and the sexuality is maintained by the sexualizing substance contained in the sexualized worms.     

Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex

Although polyploids are common among plants and some animals, polyploidization often causes reproductive failure. Triploids, in particular, are characterized by the problems of chromosomal pairing and segregation during meiosis, which may cause aneuploid gametes and results in sterility. Thus, they are generally considered to reproduce only asexually. In the case of the Platyhelminthes Dugesia ryukyuensis, populations with triploid karyotypes are normally found in nature as both fissiparous and oviparous triploids. Fissiparous triploids can also be experimentally sexualized if they are fed sexual planarians, developing both gonads and other reproductive organs. Fully sexualized worms begin reproducing by copulation rather than fission. In this study, we examined the genotypes of the offspring obtained by breeding sexualized triploids and found that the offspring inherited genes from both parents, i.e., they reproduced truly bisexually. Furthermore, meiotic chromosome behavior in triploid sexualized planarians differed significantly between male and female germ lines, in that female germ line cells remained triploid until prophase I, whereas male germ line cells appeared to become diploid before entry into meiosis. Oocytes at the late diplotene stage contained not only paired bivalents but also unpaired univalents that were suggested to produce diploid eggs if they remained in subsequent processes. Triploid planarians may therefore form euploid gametes by different meiotic systems in female and male germ lines and thus are be able to reproduce sexually in contrast to many other triploid organisms.     

Characterization of novel genes expressed specifically in the sexual organs of the planarian Dugesia ryukyuensis

The planarian Dugesia ryukyuensis reproduces both asexually (fissiparous) and sexually (oviparous) and can switch from the asexual mode to the sexual mode. By feeding with mature Bdellocephala brunnea oviparous worms, the fissiparous worms, which do not possess sexual organs, can be converted to fully sexualized worms in a process termed sexualization. As sexualization proceeds, the sexual organs are formed uniformly and five stages (stages 15) of the process have been identified histologically. In order to clarify the sexualization process, we attempted to isolate the genes expressed specifically at stage 5 by the differential display method. We isolated five genes expressed in the testis and two genes expressed in the yolk gland, which is an organ specific to sexualized worms. By BLAST search, one of the testis-specific genes was coded as testis-specific alpha-tubulin and two yolk gland-specific genes are similar to ribose-phosphate pyrophosphokinase I and F-box/SPRY-domain protein 1. Drs1, Drs2 and Drs3 were expressed in spermatocytes and spermatids from the early stage of spermatogenesis and Drs4 and Drs5 were expressed in spermatogonia, spermatocytes and spermatids. These genes are useful markers for elucidating the sexualization process.     

OOGAMOUS REPRODUCTION,WITH TWO‐STEP AUXOSPORULATION,IN THE CENTRIC DIATOM THALASSIOSIRA PUNCTIGERA (BACILLARIOPHYTA)1

Thalassiosira species are common components of marine planktonic communities worldwide and are used intensively as model experimental organisms. However, data on life cycles and sexuality within the genus are fragmentary. A clone of the cosmopolitan marine diatom Thalassiosira punctigera Cleve emend. Hasle was isolated from the North Sea and oogamous sexual reproduction was observed in culture. Cells approximately 45 μm and smaller became sexualized. Oogonia were produced preferentially and spermatogenesis was infrequent. Unfertilized oogonia always aborted and their development was apparently arrested at prophase of meiosis I. Further progression through meiosis and auxospore formation occurred only after a sperm had penetrated into the oocyte. Many cells of the new large‐celled generation (approximately 90–120 μm in size) immediately became sexualized again but only oogonia were produced. A few of the large oogonia became auxospores and produced initial cells 132–153 μm in diameter. The second step of auxosporulation probably involved fertilization of large‐celled oocytes by the sperm of the small‐celled spermatogonangia that were still present in the culture. An F₁ clone obtained after selfing within the small‐celled auxosporulation size range was investigated. Like the parent clone, the F₁ clone was homothallic but no auxosporulation was observed: spermatogonangia were unable to produce viable sperm, apparently because of inbreeding depression. Aggregation and interaction of oogonia were documented, and may be relevant for understanding the mechanisms of signaling and recognition between sexualized cells and the evolution of sexuality in pennate diatoms.     

EVOLUTIONARY LOSS OF LARVAL FEEDING: DEVELOPMENT,FORM AND FUNCTION IN A FACULTATIVELY FEEDING LARVA,BRISASTER LATIFRONS

Species with large eggs and nonfeeding larvae have evolved many times from ancestors with smaller eggs and feeding larvae in numerous groups of aquatic invertebrates and amphibians. This change in reproductive allocation and larval form is often accompanied by dramatic changes in development. Little is known of this transformation because the intermediate form (a facultatively feeding larva) is rare. Knowledge of facultatively feeding larvae may help explain the conditions under which nonfeeding larvae evolve. Two hypotheses concerning the evolutionary loss of larval feeding are as follows: (1) large eggs evolve before modifications in larval development, and (2) the intermediate form (facultatively feeding larva) is evolutionarily short-lived. I show that larvae of a heart urchin, Brisaster latifrons, are capable of feeding but do not require food to complete larval development. Food for larvae appears to have little effect on larval growth and development. The development, form, and suspension feeding mechanism of these larvae are similar to those of obligate-feeding larvae of other echinoids. Feeding rates of Brisaster larvae are similar to cooccurring, obligate-feeding echinoid larvae but are low relative to the large size of Brisaster larvae. The comparison shows that in Brisaster large egg size, independence from larval food, and relatively low feeding rate have evolved before the heterochronies and modified developmental mechanisms common in nonfeeding echinoid larvae. If it is general, the result suggests that hypotheses concerning the origin of nonfeeding larval development should be based on ecological factors that affect natural selection for large eggs, rather than on the evolution of heterochronies and developmental novelties in particular clades. I also discuss alternative hypotheses concerning the evolutionary persistence of facultative larval feeding as a reproductive strategy. These hypotheses could be tested against a phylogenetic hypothesis.     

Gyrodinium undulans Hulburt, a marine dinoflagellate feeding on the bloom-forming diatomOdontella aurita, and on copepod and rotifer eggs

The marine dinoflagellateGyrodinium undulans was discovered as a feeder on the planktonic diatomOdontella aurita. Every year, during winter and early spring, a certain percentage of cells of this bloom-forming diatom, in the Wadden Sea along the North Sea coast, was regularly found affected by the flagellate. Supplied with the food diatomO. aurita the dinoflagellate could be maintained successfully in clonal culture. The vegetative life cylce was studied, mainly by light microscopy on live material, with special regard to the mode of food uptake. Food is taken up by a so-called phagopod, emerging from the antapex of the flagellate. Only fluid or tiny prey material could be transported through the phagopod. Larger organelles like the chloroplasts ofOdontella are not ingested and are left behind in the diatom cell. Thereafter, the detached dinoflagellate reproduces by cell division, occasionally followed by a second division. As yet, stages of sexual reproduction and possible formation of resting cysts could not be recognized, neither from wild material nor from laboratory cultures. Palmelloid stages (sometimes with a delicate wall) occurring in ageing cultures may at least partly function as temporary resting stages. The winter speciesG. undulans strongly resemblesSyltodinium listii, a summer species feeding on copepod and rotifer eggs. Surprisingly, in a few cases this prey material was accepted byG. undulans as well, at least under culture conditions. When fed with copepod eggs, the dinoflagellate developed into a large trophont, giving rise thereafter by repeated binary fission to 4, 8 or 16 flagellates, as a result of a single feeding act. A re-examination of both species under simultaneous culture conditions is planned.     

三种瓢虫集团内捕食卵对初龄幼虫生长发育的影响

种内和种间捕食卵现象常见于对食蚜瓢虫的研究报道中。源自亚洲、入侵北美和欧洲的异色瓢虫(Harmonia axyridis)由于卵含有生物碱而被认为可能是威胁本土瓢虫生存的原因,但该推测只有在明确异色瓢虫在原产地是否对本土瓢虫具有类似负面影响后,才能确证。通过饲喂实验,旨在明确异色瓢虫在原产地是否对本土七星瓢虫(Coccinella septempunctata)和龟纹瓢虫(Propylea japonica)具有食卵负面作用,为揭示异色瓢虫入侵机理提供依据。实验中用蚜虫(对照)和3种瓢虫卵对瓢虫初孵1龄幼虫进行饲喂处理,观察幼虫生长发育指标。对瓢虫初龄幼虫存活表现的分析结果表明:(1)龟纹瓢虫初孵幼虫取食同种卵和七星瓢虫卵后存活至2龄的比率均高于取食异色瓢虫卵的近7倍;(2)七星瓢虫幼虫取食异色瓢虫卵未存活到2龄,但取食其他瓢虫卵和蚜虫后85%以上个体存活至2龄;(3)异色瓢虫初孵幼虫取食同种和其他2种瓢虫卵后有90%以上存活至2龄。龟纹瓢虫和七星瓢虫1龄幼虫取食异种卵比同种卵后的发育历期显著延长,但异色瓢虫并未表现出差异。龟纹瓢虫和异色瓢虫1龄幼虫取食同种和异种卵后的体增重相同,但七星瓢虫取食龟纹瓢虫卵后体增重比取食同种卵减小。研究结果说明,异色瓢虫卵对七星瓢虫和龟纹瓢虫初孵幼虫的生存具有负面影响,反之不然。所以,取食异色瓢虫卵本身并非是导致北美和欧洲本土瓢虫数量减少的原因。     

The dynamics of sexual phase in the marine diatom Pseudo‐nitzschia multistriata (Bacillariophyceae)

Sexual reproduction represents a fundamental phase in the life cycle of diatoms, linked to both the production of genotypic diversity and the formation of large‐sized initial cells. Only cells below a certain size threshold can be sexualized, but various environmental factors can modulate the success of sexual reproduction. We investigated the role of cell density and physiological conditions of parental strains in affecting the success and timing of sexual reproduction in the marine heterothallic diatom Pseudo‐nitzschia multistriata. We also studied the dynamics of the sexual phase in still conditions allowing cell sedimentation and in gently mixed conditions that keep cells in suspension. Our results showed that successful sexual reproduction can only be achieved when crossing parental strains in the exponential growth phase. Evidence was provided for the fact that sexual reproduction is a density‐dependent event and requires a threshold cell concentration to start, although this might vary considerably amongst strains. Moreover, the onset of the sexual phase was coupled to a marked reduction in growth of the vegetative parental cells. The crosses carried out in physically mixed conditions produced a significantly reduced number of sexual stages as compared to crosses in still conditions, showing that mixing impairs sexualization. The results of our experiments suggest that the signaling that triggers the sexual phase is favored when cells can accumulate, reducing the distance between them and facilitating contacts and/or the perception of chemical cues. Information on the progression of the sexual phase in laboratory conditions help understanding the conditions at which sex occurs in the natural environment.     

Extreme tolerance to environmental stress of sexual and parthenogenetic resting eggs of Eucypris virens (Crustacea,Ostracoda)

1. The freshwater ostracod (Ostracoda), Eucypris virens, is commonly found in European temporary pools, where its long‐term persistence completely relies on the build‐up of resting egg banks. Extreme tolerance of dormant eggs and seeds is widely assumed, but freshwater ostracod eggs are relatively poorly studied. The study of ostracod resting eggs is of particular relevance as it may yield the key to understanding the distribution of the sexes in many species capable of both sexual and asexual reproduction. 2. We assessed the tolerance of dried resting eggs produced by females originating from three populations with males and three all‐female E. virens populations. Hatching time and success was compared between control eggs and eggs exposed to one of seven ecologically relevant stressors: digestive enzymes, high salinity, deep freezing, hydration, UV‐B radiation, hypoxia and insecticide treatment. 3. None of the stressors reduced significantly the viability of either sexual or asexual eggs. When compared with the reproductive mode–specific controls, exposure to UV‐B radiation had a mild impact on the survival of sexual and asexual eggs (?16.8 and ?22.4%, respectively), but this was only significant for asexual eggs. These results point to an extreme tolerance of E. virens resting eggs and have important implications for the ecology and evolution of the species. 4. The timing of hatching was not affected by the stress treatment, except for UV‐B radiation. A marginally significant delay in hatching response was observed for UV‐B‐radiated eggs when compared to the overall mean, but this treatment effect was absent when compared with the reproductive mode–specific controls. 5. The populations with males produced eggs that hatched on average earlier (?1.5 days at 17 °C) and were more successful (+26%) than asexual eggs. Due to the limited number of populations and the population‐specific origin and age of the eggs, the possibility due to the differences in age and origin of the resting eggs, or to variations in local conditions, cannot be ruled out.     

Sexual dimorphism and food habits of the clingfish,Diademichthys lineatus,and its dependence on host sea urchin

Synopsis Stomach contents of the clingfish Diademichthys lineatus, 10–56 mm standard length, revealed changes in food habits with growth and sexual differences. Soon after settlement, D. lineatus obtained food from their host sea urchin (genus Diadema) and other associated symbionts. They became less dependent on the host with growth. The juveniles ate pedicellariae and sphaeridia of the host and commensal copepods, whereas the adult fish ate burrowing bivalves in corals as well as tube feet of their host and eggs of a commensal shrimp. The young fish were transitional in their food habits. The change in food habits of the fish coincided with behavioral changes; i.e. enlargement of home ranges and less dependency on the host. The adult females, having a longer snout, ate shrimp eggs and bivalves more frequently than the adult males, which ate tube feet of the host more often than the females did. Sexual difference in food habits was apparent after the sex of the fish became identifiable by comparing snout shapes. The polygynous mating system of this species suggests that conspicuous sexual dimorphism might have developed under sexual selection. However, niche partitioning of food is also likely to be related to this sexual dimorphism.     

Effect of cannibalism on predation,oviposition and longevity of the predacious mite,Agistemus exsertus Gonzalez (Acari: Stigmaeidae)

Cannibalism (intraspecific predation) on conspecific eggs was investigated in the predatory stigmaeid mite, Agistemus exsertus Gonzalez in the absence of eggs of Tetranychus urticae Koch (no-choice tests) and presence of three densities of prey eggs simultaneously (choice tests) in the laboratory. Data show that cannibalism occurs in immatures and adult females of the predator, which successfully developed and reproduced on conspecific eggs as an alternative prey in the absence of prey eggs. In no-choice tests, cannibalism rate on conspecific eggs by A. exsertus stages was significantly lower than the predation rate on T. urticae eggs. The predatory mite exhibited a marked decline in oviposition rate when preyed on conspecific eggs compared with feeding on prey eggs. The developmental duration and longevity of A. exsertus females were significantly longer 1.9 and 1.7 times, respectively, when fed on conspecific eggs than feeding on T. urticae eggs. The propensity of the predator towards cannibalism depends on the prey density, when T. urticae eggs and conspecific eggs are present simultaneously. Provision of increased densities of prey eggs significantly decreased cannibalism and predation by A. exsertus stages, which fed generally less on conspecific eggs than on T. urticae eggs in choice tests. The oviposition rate of the predator increased significantly, as the egg density of the prey increased. The developmental period and longevity of A. exsertus females showed significantly gradual shortness with increasing egg density of the prey.     

Early development of the rainbow darter,Etheostoma caeruleum,according to the theory of saltatory ontogeny

Synopsis The early development of rainbow darter, Etheostoma caeruleum, was examined from an ecological perspective. Steps and thresholds of ontogeny to completion of body squammation are defined, and related to environmental factors. Rainbow darter eggs are about 2 mm diameter, considerably larger than those of related logperch (Percina caprodes). The embryonic vitelline respiratory plexus is much more extensive. The pelagic interval characteristic of logperch and ancestral percids is eliminated and onset of exogenous feeding is delayed. The larger larvae of the rainbow darter can begin feeding directly on aquatic insects, and complete their life cycle in streams. Therefore, shifts in the timing of important thresholds (e.g. exogenous feeding) are ecologically important. Furthermore, early maturation and/or delayed bone and scale formation may be responsible for reductions in the lateralis system and scalation in this and other darter species.     

Feeding behavior ofEuseius stipulatus andTyphlodromus phialatus on the citrus red mitePanonychus citri [Acari: Phytoseiidae,Tetranychidae]

Observations were made on the feeding behavior of the two main phytoseiid species in Spanish Citrus orchards,Euseius stipulatus (Athias-Henriot) andTyphlodromus phialatus Athias-henriot. The experiences were carried out by rearing the predatory mites on excised orange leaves, and always with an excess of the prey the Citrus Red Mite (=CRM)Panonychus citri (McGregor). In experiments with all stages of CRM, the number of prey killed per hour was 5.12 and 2.00, the percentage of successful attacks, 58% and 21%, and the mean time spent feeding on each prey was 5.1 and 12.2 minutes for starving females ofE. stipulatus andT. phialatus respectively.E. stipulatus feeds on all stages of the prey except eggs, andT. philatus, on all stages, except males. Both species attack much less successfully females ofP. citri rather than immatures. In experiments with adult females and eggs ofP. citri as prey, the mean number of prey killed daily was 4.51 females forE. stipulatus, and 2.01 females and 2.12 eggs forT. philatus. Considering this killing rate and the number of eggs laid by the predators in the same period, it can be concluded thatE. stipulatus consumes only 30% of the content of the preys killed, whereasT. philatus consumes a percentage of prey variable between individuals and ranging from 40% to 100%. These differences in feeding behavior between the two species could partly explain differences in their efficiency as biocontrol agents ofP. citri observed in the field.      

Short-term changes in consumption and oviposition rates of Neoseiulus californicus strains (Acari: Phytoseiidae) after a diet shift

Short-term effects on consumption and oviposition rates of four strainsof Neoseiulus californicus (McGregor) after a diet shiftwere evaluated. The new feeding conditions experienced by the predators weresixfixed densities of eggs or protonymphs of Tetranychusurticae Koch placed on excised strawberry leaflet discs andmaintained under laboratory conditions (25±1°C,75–85% RH, 16L: 8D). The observations were made on the first and thefifthday of the experiment. The phytoseiids came from three long-term mass-rearedstrains fed on T. urticae, Dermatophagoides farinaeHughes,or Quercus spp. pollen, respectively. The fourth strainwascollected directly in a strawberry field. Time since diet transfer can be addedto the factors (i.e. feeding history and prey density) already known to affectthe functional and numerical responses of N. californicus,both when it feeds on prey eggs and protonymphs. If consumption rates wereaveraged over all strains and densities, 9.04 and 11.41 eggs, and 6.97 and 6.48protonymphs were consumed on the first and the fifth day, respectively. If thesame was done for oviposition rates, predators feeding on eggs produced 1.46and2.36 eggs/female/day, whereas predators feeding on protonymphs produced 1.35and2.29 eggs/female/day. Time had the greatest impact on the functional responseofthe strain that had previously fed on tetranychids, while an effect of time onthe numerical response was detectable in all strains.     

Nutritional implications for sexual cannibalism in a sexually dimorphic orb web spider

Models predicting mechanisms driving sexual cannibalism in spiders with sexual size dimorphism (SSD) often assume that spiders use post‐copulatory food to channel nutrients into eggs and fecundity is altered through changes in clutch size or egg mass. I tested these assumptions using an orb web spider with extreme SSD, Argiope keyserlingi. I fed mated female spiders prey of either high protein‐low energy or low protein‐high energy composition. I measured egg energy density; a measure of the relative volumes of yolk and albumen. I predicted that if A. keyserlingi increase their egg energy density upon feeding on prey of a specific nutrient composition, they could enhance their fecundity by investing in more energy dense eggs. However, if the egg energy densities are dissimilar to their post‐copulatory prey they must be drawing energy from their somatic reserves to invest in eggs. In a further experiment I allowed female spiders to mate with and cannibalize males to determine if cannibalism induces similar effects on egg energy density. Male spider protein energy ratio was measured and found to resemble the high protein‐low energy prey. I found disagreement between the composition of post‐copulatory food and eggs in both experiments. Additionally, spiders fed high protein‐low energy prey lost weight indicating that they draw on their energy reserves to invest in eggs. I thus concluded that spiders that feed on high protein‐low energy prey or on males increase their egg energy density and, possibly, fecundity. However, the nutrient content of the prey or males cannot provide for investment in eggs. The energy invested in eggs is drawn from somatic reserves, probably induced by an as yet undescribed physiological trigger.     

Biological Studies of the Pearl Spot Etroplus suratensis (Pisces,Cichlidae) from three Different Habitats in Sri Lanka

The morphometry, feeding habits and reproductive biology of Etroplus suratensis, an indigenous cichlid food fish, were studied for a period of one year on specimens from three different habitats in Sri Lanka. The morphometric studies implied that the length weight relationships are curvilinear. Macrophytic fragments formed the most important component of food, although detritus, diatoms, and animal matter are also ingested. First sexual maturity is attained in the length ranges 8.0-9.0 cm in females from brackish water habitats. Fecundity ranged from 700-3900 eggs in mature specimens. The wide range of the gonadosomatic index suggests that spawning occurs several times during the year.     

Reproductive mode and ovarian morphology regulation in chimeric planarians composed of asexual and sexual neoblasts

Planarians are comprised of populations with different reproductive strategies: exclusively innately asexual (AS), exclusively innately sexual (InS), and seasonally switching. AS worms can be sexualized experimentally by feeding them with minced InS worms, and the resultant worms are characterized as acquired sexual (AqS). Differences between InS and AqS worms are expected to provide important clues to the poorly understood mechanism underlying the regulation of their reproductive mode. Morphological differences were found between InS and AqS worm ovaries, and we showed that the pluripotent stem cells (neoblasts) from InS worms, but not those of AqS worms, have the capacity to initiate the sexual state autonomously via neoblast fraction transplantation. To compare their reproductive mode and ovarian morphology regulation, InS donor neoblast fractions were transplanted into non-lethally X-ray-irradiated AS recipients. All transplants showed stable chimerism and reproduced sexually, suggesting that InS worm neoblasts can initiate sexual state autonomously, even when coexisting with AS worm neoblasts. The chimeras formed extraordinarily large and supernumerary ovaries equivalent to AqS worms, which were not seen in InS worms, suggesting that regulation of ovarian morphology in AS worm-derived cells in response to endogenous sexualizing stimulation distinctly differs from that of InS worms.     

Egg Size, Intrinsic Competition, and Lethal Interference in the Parasitoids Encarsia pergandiella and Encarsia formosa

Recent population dynamic theory predicts that disruption of biological control may occur when one parasitoid species' superiority in intrinsic competition is associated with a lower ability to find and exploit hosts (i.e., ability in extrinsic competition). One might expect such a trade-off, for instance, if parasitoids with larger (and fewer) eggs are more likely to prevail in intrinsic competition than species with smaller (and more numerous) eggs. We tested the idea that relative egg size could be used to predict the outcome of intrinsic competition in two closely related endoparasitoids, Encarsia pergandiella Howard and Encarsia formosa Gahan. Contrary to expectation, the parasitoid species with smaller eggs, E. pergandiella, prevailed in intrinsic competition, regardless of the order that hosts were exposed to the two species. In a literature survey, we found four studies of competing pairs of endoparasitoid species for which: (a) egg size estimates were available and (b) one species was consistently superior in intrinsic competition. In three of the four studies, the small-egged species prevailed in intrinsic competition, as we also found. Although E. formosa lost in intrinsic competition, this species negatively affected E. pergandiella's progeny production by host feeding on and killing hosts containing E. pergandiella eggs. E. formosa females also host fed on conspecific-parasitized hosts. As a mechanism of both intra- and interspecific interference competition, host feeding on parasitized hosts contradicts assumptions about the nature of interference competition in existing population dynamics models.     

Comparative studies of predation among feral,commercially-purchased,and laboratory-reared predators

The predatory activities of commercially-purchased adult Hippodamia convergens Guérin-Méneville and two laboratory-reared strains of adult Geocoris punctipes (Say) were compared with their feral counterparts. In single prey choice feeding tests, commercially-purchased and feral H. convergens were provided copious amounts of silverleaf whitefly, Bemisia argentifolii Bellows & Perring adults or eggs of pink bollworm, Pectinophora gossypiella (Saunders). Commercially-purchased H. convergens devoured more pink bollworm eggs and at a faster rate than the feral H. convergens. In contrast, feral H. convergens consumed more adult whiteflies and at a faster rate than commercial H. convergens. In multiple feeding choice tests, two distinctly different laboratory-reared strains and feral G. punctipes were provided a cotton leaf disk containing copious amounts of silverleaf whitefly eggs, nymphs, and adults. Virtually no predation was observed on whitefly eggs, but both laboratory strains of G. punctipes fed on more whitefly nymphs and adults than the feral G. punctipes. Moreover, both of the laboratory strains had a significantly faster feeding rate on adult whiteflies and spent significantly less time feeding on plant tissue than the feral strain. These results suggest that the augmentative biological control candidates retained their ability to prey on these selected prey items, even after being displaced from their overwintering site (H. convergens) or being reared in captivity (G. punctipes) for over 40 generations. Handling editor: Patrick De Clercq. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by the USDA.     

Clavispora opuntiae and other yeasts associated with the mothSigelgaita sp. in the cactusPilosocereus arrabidae of Rio de Janeiro,Brazil

Summary Clavispora opuntiae was the prevalent yeast associated with the feeding sites ofSigelgaita sp. larvae in the cactusPilosocereus arrabidae. Also associated with this habitat wereCandida sonorensis, Pichia cactophila, Pichia barkeri, Candida sp. A,Geotrichum sp.,Geotrichum sericeum and the yeast like organismsPrototheca zopfii andAcremonium sp. Atypical yeast biotypes that may represent new species ofPichia, Sporopachydermia andCandida were isolated. Mating types ofClavispora opuntiae were at a ratio 70 h⁺ to 3 h^- and reduced levels of sporulation suggested low pressure for sexual reproduction in this habitat.Sigelgaita sp. probably was not an important vector forClavispora opuntiae because it was not isolated from an adult or eggs of this moth.