An optimized method for Nasonia germ-free rearing

A germ-free rearing system is a crucial method for host–microbiota interactions using Nasonia as a model system. The previous rearing media in 2012 introduced toxic factors like bleach and antibiotics, required significant effort and volume of media preparation, and the rearing protocols in 2012 and 2016 often resulted in embryos, larvae, and enclosing pupae drowning, underfed, or desiccating. In this work, we optimize the germ-free rearing media that excludes the toxic factors and provide a substrate for the developing animals to have constant access to media without the risk of drowning or desiccation. The new process resulted in an increase in full maturation of larvae to adults from 33 to 65%, with no effect on the rate of growth or final adult size. This significantly improves the applicability of germ-free rearing of Nasonia and potentially other parasitoids.

Applying computer vision to digitised natural history collections for climate change research: temperature-size responses in British butterflies

Natural history collections (NHCs) are invaluable resources for understanding biotic response to global change. Museums around the world are currently imaging specimens, capturing specimen data, and making them freely available online. In parallel to the digitisation effort, there have been great advancements in computer vision (CV): the computer trained automated recognition/detection, and measurement of features in digital images. Applying CV to digitised NHCs has the potential to greatly accelerate the use of NHCs for biotic response to global change research. In this paper, we apply CV to a very large, digitised collection to test hypotheses in an established area of biotic response to climate change research: temperature-size responses. We develop a CV pipeline (Mothra) and apply it to the NHM iCollections of British butterflies (>180,000 specimens). Mothra automatically detects the specimen in the image, sets the scale, measures wing features (e.g., forewing length), determines the orientation of the specimen (pinned ventrally or dorsally), and identifies the sex. We pair these measurements and meta-data with temperature records to test how adult size varies with temperature during the immature stages of species and to assess patterns of sexual-size dimorphism across species and families. Mothra accurately measures the forewing lengths of butterfly specimens and compared to manual baseline measurements, Mothra accurately determines sex and forewing lengths of butterfly specimens. Females are the larger sex in most species and an increase in adult body size with warm monthly temperatures during the late larval stages is the most common temperature size response. These results confirm suspected patterns and support hypotheses based on recent studies using a smaller dataset of manually measured specimens. We show that CV can be a powerful tool to efficiently and accurately extract phenotypic data from a very large collection of digital NHCs. In the future, CV will become widely applied to digital NHC collections to advance ecological and evolutionary research and to accelerate the use of NHCs for biotic response to global change research.

The Lesser Pacific Striped Octopus, Octopus chierchiae: An Emerging Laboratory Model

Cephalopods have the potential to become useful experimental models in various fields of science, particularly in neuroscience, physiology, and behavior. Their complex nervous systems, intricate color- and texture-changing body patterns, and problem-solving abilities have attracted the attention of the biological research community, while the high growth rates and short life cycles of some species render them suitable for laboratory culture. Octopus chierchiae is a small octopus native to the central Pacific coast of North America whose predictable reproduction, short time to maturity, small adult size, and ability to lay multiple egg clutches (iteroparity) make this species ideally suited to laboratory culture. Here we describe novel methods for multigenerational culture of O. chierchiae, with emphasis on enclosure designs, feeding regimes, and breeding management. O. chierchiae bred in the laboratory grow from a 3.5 mm mantle length at hatching to an adult mantle length of approximately 20–30 mm in 250–300 days, with 15 and 14% survivorship to over 400 days of age in first and second generations, respectively. O. chierchiae sexually matures at around 6 months of age and, unlike most octopus species, can lay multiple clutches of large, direct-developing eggs every ∼30–90 days. Based on these results, we propose that O. chierchiae possesses both the practical and biological features needed for a model octopus that can be cultured repeatedly to address a wide range of biological questions.

Tetraspanin Cd9b plays a role in fertility in zebrafish

In mice, CD9 expression on the egg is required for efficient sperm-egg fusion and no effects on ovulation or male fertility are observed in CD9 null animals. Here we show that cd9b KO zebrafish also appear to have fertility defects. In contrast to mice, fewer eggs were laid by cd9b KO zebrafish pairs and, of the eggs laid, a lower percentage were fertilised. In vitro fertilization (IVF) was used to demonstrate that factors such as courting behaviour, adult size and mate choice were not causing the unexpected decrease in clutch size. The decrease in egg numbers could be rescued by exchanging either cd9b KO partner, male or female, for a wildtype (WT) partner. However, the fertilisation defect could only be rescued by crossing a cd9b KO female with a WT male. Our results indicate that Cd9b has several roles in fish fertility, affecting both clutch size and egg fertilisation.

Population Ecology Studies on Infaunal Polychaetes of Pauatahanui Inlet

<p>Macrofaunal polychaete densities across a stable, fine-sand, intertidal flat in Pauatahanui Inlet were examined from a set of seasonal samples, 500 micron sieve processed, from a stratified transect pair. Density Patterns had shore-normal trends, despite apparently weak tidal-cycle environmental gradients. Zones of high abundance of common species persisted unchanged, but seasonal increase and decline occurred within them, with also some population redistribution attributable to differential mortality/recruitment, or possibly to migration. Correlation analysis did not detect interspecies relationships linked to the abundance and zonation of the common polychaetes, all deposit-feeders. The population dynamics of six species was investigated from the transect-pair seasonal samples, supplemented by subsequent more finely-sieved samples during dense recruitment periods. The maldanid Axiothella serrata had three identifiable age groups O, I, and II+, with I plus II+ density to about 550 m-2. The new O group began to appear in October-November, as aggregates below 3 cm sediment depth, believed to represent lecithotropic, direct-developing, siblings from egg masses of the II+ group. Juvenile setiger-total frequencies indicated synchronous adult spawning occurred at varying intervals during an approximate six month period. Peak density of dispersed, near-surface recruits reached 29 thousand m-2. Setiger-total was the most sensitive indicator of size and age in juveniles of up to about 15 setigers. Zonation patterns were age specific. The predominantly lower-shore capitellid, Heteromastus filiformis had a short summer spawning period with settlement ending before May, when population density was up to 10 thousand m-2. Merger of O group into the adult size range occurred in about one year, and probably first spawning was at the end of the second year, with life span of three years or more. The nereidid Nicon aestuariensis had I+ and older age groups at barely detectable densities. Spawning was probably in late summer although an O group, at about 500 m-2, was not detected until May. The spionid Scolecolepides benhami had apparently unchanging size structure and density (about 400 m-2 transect-wide); new settlement was not detected. High density occurred only in a narrow near-shore strip. Nicon aestuariensis also declined down-shore, but more gradually. The spionid Microspio sp. and capitellid Capitella sp. were short-lived, near-surface species, with apparently continuous recruitment from planktotrophic and direct-development respectively. A spring recruitment increase created at first a separate modal group of juveniles, and raised Microspio sp. density to 45 thousand m-2 and Capitella sp. to 7 thousand m-2. Capitella sp. declined in density downshore, but Microspio sp. was only weakly zoned. The common polychaetes had largely concordant density cycles with settlement (or peak settlement) spring-summer orientated, although 500 micron mesh processing detected the peak of surviving adults in autumn-winter. Pauatahanui polychaetes as an assemblage, life history traits, links between population structure and zonation, and problems in polychaete population studies are discussed.</p>

Population Ecology Studies on Infaunal Polychaetes of Pauatahanui Inlet

<p>Macrofaunal polychaete densities across a stable, fine-sand, intertidal flat in Pauatahanui Inlet were examined from a set of seasonal samples, 500 micron sieve processed, from a stratified transect pair. Density Patterns had shore-normal trends, despite apparently weak tidal-cycle environmental gradients. Zones of high abundance of common species persisted unchanged, but seasonal increase and decline occurred within them, with also some population redistribution attributable to differential mortality/recruitment, or possibly to migration. Correlation analysis did not detect interspecies relationships linked to the abundance and zonation of the common polychaetes, all deposit-feeders. The population dynamics of six species was investigated from the transect-pair seasonal samples, supplemented by subsequent more finely-sieved samples during dense recruitment periods. The maldanid Axiothella serrata had three identifiable age groups O, I, and II+, with I plus II+ density to about 550 m-2. The new O group began to appear in October-November, as aggregates below 3 cm sediment depth, believed to represent lecithotropic, direct-developing, siblings from egg masses of the II+ group. Juvenile setiger-total frequencies indicated synchronous adult spawning occurred at varying intervals during an approximate six month period. Peak density of dispersed, near-surface recruits reached 29 thousand m-2. Setiger-total was the most sensitive indicator of size and age in juveniles of up to about 15 setigers. Zonation patterns were age specific. The predominantly lower-shore capitellid, Heteromastus filiformis had a short summer spawning period with settlement ending before May, when population density was up to 10 thousand m-2. Merger of O group into the adult size range occurred in about one year, and probably first spawning was at the end of the second year, with life span of three years or more. The nereidid Nicon aestuariensis had I+ and older age groups at barely detectable densities. Spawning was probably in late summer although an O group, at about 500 m-2, was not detected until May. The spionid Scolecolepides benhami had apparently unchanging size structure and density (about 400 m-2 transect-wide); new settlement was not detected. High density occurred only in a narrow near-shore strip. Nicon aestuariensis also declined down-shore, but more gradually. The spionid Microspio sp. and capitellid Capitella sp. were short-lived, near-surface species, with apparently continuous recruitment from planktotrophic and direct-development respectively. A spring recruitment increase created at first a separate modal group of juveniles, and raised Microspio sp. density to 45 thousand m-2 and Capitella sp. to 7 thousand m-2. Capitella sp. declined in density downshore, but Microspio sp. was only weakly zoned. The common polychaetes had largely concordant density cycles with settlement (or peak settlement) spring-summer orientated, although 500 micron mesh processing detected the peak of surviving adults in autumn-winter. Pauatahanui polychaetes as an assemblage, life history traits, links between population structure and zonation, and problems in polychaete population studies are discussed.</p>

Relationships between the Pathogen Erysiphe alphitoides, the Phytophagous Mite Schizotetranychus garmani (Acari: Tetranychidae) and the Predatory Mite Euseius finlandicus (Acari: Phytoseiidae) in Oak

Food webs on forest trees include plant pathogens, arthropods, and their natural enemies. To increase the understanding of the impact of a plant pathogen on herbivore-natural enemy interactions, we studied the powdery mildew fungus Erysiphe alphitoides, the phytophagous mite Schizotetranychus garmani, and the predatory and mycophagous mite Euseius finlandicus in pedunculate oak (Quercus robur) leaves. In June, July and August of 2016, we assessed the severity of powdery mildew, mite population density and adult female mite size in 30 trees in three forests near Belgrade, Serbia. In August, the infection severity of E. alphitoides related positively to the population density of S. garmani and negatively to the body size of S. garmani females. Throughout the vegetative season, the infection severity of E. alphitoides related positively to the population density of E. finlandicus but not to its body size. The effect of E. alphitoides on the population density and adult size of S. garmani was not mediated by the population density of E. finlandicus, and vice versa. Interactions were consistent in all forests and varied with the summer month. Our findings indicate that E. alphitoides can influence the average body size and population densities of prey and predatory mites studied, irrespective of predator-prey relationships.

Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Adult aphid predators disperse across the landscape seasonally in search of prey aggregations that are patchily distributed and temporally variable. However, flight is energetically costly and consumes resources that could be invested in reproduction. Hippodamia convergens is an important aphid predator in North American cereal crops and other agricultural systems. Consumption of floral resources can enhance adult survival during periods of low prey availability and may improve reproductive success. We tested how an omnivorous adult diet containing floral resources (diluted honey and pulverized bee pollen) interacts with body size to influence reproduction and flight behavior compared to a prey-only diet. Two sizes of beetles were produced by controlling larval access to food—3 h daily access produced small beetles; ad libitum access produced large beetles with faster development. Reproductive performance was tracked for 18 days, and female flight activity was assayed via 3 h bouts of tethered flight. Diet composition and body size interacted to influence preoviposition period, with large females in prey-only treatments delaying oviposition the longest. The omnivorous adult diet improved 18-day fecundity relative to a prey-only diet, but egg fertility was unaffected. Adult size affected oviposition pattern, with small beetles laying smaller, but more numerous, clutches. Females flew up to 7 km in 6 h, but neither body size nor adult diet influenced flight distance, suggesting that all diet treatments generated energy reserves sufficient to power flights of short duration. However, pre-reproductive females flew &gt; 60% further than they did post-reproduction, likely due to the energetic costs of oviposition. Thus, access to pollen and nectar increased reproductive success and altered oviposition patterns in H. convergens, indicating the importance of floral resources in the agricultural landscape to conservation of this predator and its biological control services.

The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae)

The four described species of Danionella are tiny, transparent fishes that mature at sizes between 10–15 mm, and represent some of the most extreme cases of vertebrate progenesis known to date. The miniature adult size and larval appearance of Danionella, combined with a diverse behavioral repertoire linked to sound production by males, have established Danionella as an important model for neurophysiological studies. The external similarity between the different species of Danionella has offered an important challenge to taxonomic identification using traditional external characters, leading to confusion over the identity of the model species. Using combined morphological and molecular taxonomic approaches, we show here that the most extensively studied species of Danionella is not D. translucida, but represents an undescribed species, D. cerebrum n. sp. that is externally almost identical to D. translucida, but differs trenchantly in several internal characters. Molecular analyses confirm the distinctiveness of D. cerebrum and D. translucida and suggest that the two species are not even sister taxa. Analysis of the evolution of sexual dimorphisms associated with the Weberian apparatus reveals significant increases in complexity from the simpler condition found in D. dracula, to most complex conditions in D. cerebrum, D. mirifica and D. translucida.

No impact of biocontrol predator on development time or size of surviving Aedes albopictus under optimal nutritional availability

BackgroundCyclopoid copepods have been applied successfully to limit populations of highly invasive Aedes albopictus mosquitoes that can vector diseases, including chikungunya, dengue, yellow fever, and Zika, to humans. However, there is concern that changes in certain vector traits, induced by exposure to copepod predation, might increase the risk of disease transmission. In this study, we tested whether cyclopoid copepod predation has sublethal effects on the development time or adult size of Ae. albopictus under the scenario of an invasion in southeast England, which lies at the northern edge of the vector’s expanding global range.MethodsThird instar Ae. albopictus larvae, hereafter referred to as “focal individuals”, were placed in individual Petri dishes, each containing four newly-hatched Ae. albopictus larvae, which were counted, removed, and replaced daily. All focal individuals were provided with fish food ad libitum, and half were exposed to Megacyclops viridis copepod predators. The day of pupation was recorded for each focal individual, and the wing length of each focal adult was also measured.ResultsExposing late instar Ae. albopictus to predation decreased their chances of surviving to adulthood. Mortality of the focal individuals was 12.9% in the predator treatment, and 2.9% in the controls. Three focal larvae that died in the predator treatment showed signs of melanization, indicative of wounding. Among surviving Ae. albopictus, no significant difference in either pupation day or wing length was observed due to copepod predation.ConclusionsWe found that M. viridis predation on smaller Ae. albopictus larvae does not significantly affect the pupation day or adult size of surrounding larger larvae that are less vulnerable to copepod attacks. This study controlled for density effects on size by maintaining a constant number of newly-hatched prey larvae surrounding each focal larva. Those working to control Ae. albopictus populations in the field should be made aware that increased adult body size can occur if copepod biocontrol agents are applied at lower than necessary levels. The absence of a significant sublethal impact from M. viridis copepod predation on surviving later-stage larvae in this analysis supports the use of M. viridis as a biocontrol agent.Graphical abstract