Parent Colony Research Articles

Selective breeding enhances coral heat tolerance to marine heatwaves

Marine heatwaves are becoming more frequent, widespread and severe, causing mass coral bleaching and mortality. Natural adaptation may be insufficient to keep pace with climate warming, leading to calls for selective breeding interventions to enhance the ability of corals to survive such heatwaves, i.e., their heat tolerance. However, the heritability of this trait–a prerequisite for such approaches–remains unknown. We show that selecting parent colonies for high rather than low heat tolerance increased the tolerance of adult offspring (3–4-year-olds). This result held for the response to both 1-week +3.5 °C and 1-month +2.5 °C simulated marine heatwaves. In each case, narrow-sense heritability (h2) estimates are between 0.2 and 0.3, demonstrating a substantial genetic basis of heat tolerance. The phenotypic variability identified in this population could theoretically be leveraged to enhance heat tolerance by up to 1 °C-week within one generation. Concerningly, selective breeding for short-stress tolerance did not improve the ability of offspring to survive the long heat stress exposure. With no genetic correlation detected, these traits may be subject to independent genetic controls. Our finding on the heritability of coral heat tolerance indicates that selective breeding could be a viable tool to improve population resilience. Yet, the moderate levels of enhancement we found suggest that the effectiveness of such interventions also demands urgent climate action.

Shaping the tripartite symbiosis: are termite microbiome functions directed by the environmentally acquired fungal cultivar?

Microbiome assembly critically impacts the ability of hosts to access beneficial symbiont functions. Fungus-farming termites have co-evolved with a fungal cultivar as a primary food source and complex gut microbiomes, which collectively perform complementary degradation of plant biomass. A large subset of the bacterial community residing within termite guts are inherited (vertically transmitted) from parental colonies, while the fungal symbiont is, in most termite species, acquired from the environment (horizontally transmitted). It has remained unknown how the gut microbiota sustains incipient colonies prior to the acquisition of the fungal cultivar, and how, if at all, bacterial contributions are modulated by fungus garden establishment. Here, we test the latter by determining the composition and predicted functions of the gut microbiome using metabarcoding and shotgun metagenomics, respectively. We focus our functional predictions on bacterial carbohydrate-active enzyme and nitrogen cycling genes and verify compositional patterns of the former through enzyme activity assays. Our findings reveal that the vast majority of microbial functions are encoded in the inherited microbiome, and that the establishment of fungal gardens incurs only minor modulations of predicted bacterial capacities for carbohydrate and nitrogen metabolism. While we cannot rule out that other symbiont functions are gained post-fungus garden establishment, our findings suggest that fungus-farming termite hosts are equipped with a near-complete set of gut microbiome functions at the earliest stages of colony life. This inherited, incipient bacterial microbiome likely contributes to the high extent of functional specificity and coevolution observed between termite hosts, gut microbiomes, and the fungal cultivar.

Sediment source and dose influence the larval performance of the threatened coral Orbicella faveolata.

The effects of turbidity and sedimentation stress on early life stages of corals are poorly understood, particularly in Atlantic species. Dredging operations, beach nourishment, and other coastal construction activities can increase sedimentation and turbidity in nearby coral reef habitats and have the potential to negatively affect coral larval development and metamorphosis, reducing sexual reproduction success. In this study, we investigated the performance of larvae of the threatened Caribbean coral species Orbicella faveolata exposed to suspended sediments collected from a reef site in southeast Florida recently impacted by dredging (Port of Miami), and compared it to the performance of larvae exposed to sediments collected from the offshore, natal reef of the parent colonies. In a laboratory experiment, we tested whether low and high doses of each of these sediment types affected the survival, settlement, and respiration of coral larvae compared to a no-sediment control treatment. In addition, we analyzed the sediments used in the experiments with 16S rRNA gene amplicon sequencing to assess differences in the microbial communities present in the Port versus Reef sediments, and their potential impact on coral performance. Overall, only O. faveolata larvae exposed to the high-dose Port sediment treatment had significantly lower survival rates compared to the control treatment, suggesting an initial tolerance to elevated suspended sediments. However, significantly lower settlement rates were observed in both Port treatments (low- and high-dose) compared to the control treatment one week after exposure, suggesting strong latent effects. Sediments collected near the Port also contained different microbial communities than Reef sediments, and higher relative abundances of the bacteria Desulfobacterales, which has been associated with coral disease. We hypothesize that differences in microbial communities between the two sediments may be a contributing factor in explaining the observed differences in larval performance. Together, these results suggest that the settlement success and survival of O. faveolata larvae are more readily compromised by encountering port inlet sediments compared to reef sediments, with potentially important consequences for the recruitment success of this species in affected areas.

Trait‐dependent plasticity erodes rapidly with repeated intergenerational acclimation in an invasive agricultural pest

AbstractClimate change is associated with increased mean temperatures and amplitudes manifesting both acutely and chronically, triggering organism stress responses that confer fitness costs and/or benefits. The larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive postharvest agricultural pest. While host shift is its well‐known potential invasive mechanism, how repeated intergenerational stress environments may influence offspring phenotypes is largely unknown. We thus evaluated physiological and ecological performance of LGB following repeated intergenerational acute heat acclimation to insinuate its likely responses to projected increased bouts of heat stress associated with climate change. Parental colonies were acutely heat‐acclimated separately at 35°C and 38°C; 80% RH for 2 h in climate chambers and released onto sterilized maize grain at optimal conditions (32°C, 80% RH). The F1 progenies were, respectively, acclimated at the same conditions and incubated to F2 generation. We then evaluated physiological and ecological performance under optimal conditions across parental, F1 and F2 generations. Our results showed that plasticity was highly trait dependent, and that acclimation did not affect F1 and F2 critical thermal maxima, but did improve critical thermal minima. However, while acclimation improved heat knockdown time at F1, repeated acclimation significantly reduced heat knockdown times at F2, suggesting plasticity erosion with generational repeated acclimations. Acute acclimation negatively affected ecological performance of F1 generations although this was restored with repeated acclimation in F2 populations. Our results suggest that the LGB may inflict more economic damage with repeated heat stress due to generational adaptation to temperature stress. The results contribute to knowledge on pest forecasting modelling under changing climates and provides a framework for phytosanitary adjustments in heat treatment protocols for international grain trade.

Coral mariculture using abandoned abalone farming ponds in northeastern Taiwan

Stony corals are ecologically and economically important marine organisms. Coral aquaculture is essential to provide live coral materials for the marine ornamental trade, reef restoration programs, and environmental education. This study sought to establish coral farms in Taiwan. To culture corals, we adopted an abandoned abalone farming pond built along the northeastern coast of Taiwan, and investigated whether it is possible to propagate corals in this artificial environment. Stainless steel underwater tables were anchored to the pond floor, and fragments of Acropora tumida, Pocillopora damicornis, Stylophora pistillata, Favites pentagona, and Porites lobata were cultured on the tables for one year. Environmental factors in the pond were also monitored. The mean surface temperature was 23.07 °C, ranging from >30 °C in summer to 18 °C in winter. The mean salinity and pH were about 35 ppt and 8.14, respectively. Survivorship of these five species after one year ranged from 100% to 67%, with a 1.37–1.51-fold increase in weight and a 3.22–3.38-fold increase in area, demonstrating that although environmental factors fluctuate depending on the season and weather, long-term and stable asexual propagation of corals is feasible in the pond. For further optimization of culture conditions, the effects of initial fragment size for culture on subsequent survival and growth were investigated. Fragments of 3 sizes (1.5, 3.0, and 4.5 cm) were prepared from parental colonies of A. tumida, P. damicornis, and S. pistillata and cultured for 6 months by hanging them under the table. There were no significant differences in survivorship among these sizes. Differences were observed in biomass (weight) increase. In A. tumida, 3-cm fragments showed significantly more weight gain than other lengths, while 1.5-cm fragments showed a significant weight increase in P. damicornis. In S. pistillata, no significant difference in weight increase was observed among size groups, suggesting the necessity to optimize the initial fragment size for culture for each species before mass culture. Histological analysis showed that mature gametes were formed in some cultured corals, suggesting that sexual propagation may also be possible in the future. The established coral farm, which is culturing >4000 coral fragments now, will be able to support not only basic and applied coral research, but also sustainable reef development and marine ornamental trade.

Expression, purification, and characterization of self-assembly virus-like particles of capsid protein L1 HPV 52 in Pichia pastoris GS115

BackgroundCervical cancer caused by the human papillomavirus (HPV) is one of the most frequent malignances globally. HPV 52 is a high-risk cancer-causing genotype that has been identified as the most prevalent type in Indonesia. Virus-like particles (VLP)-based vaccinations against HPV infection could benefit from self-assembled VLP of L1 capsid protein. ResultThe recombinant HPV 52 L1 was expressed in Pichia pastoris on a shake-flask scale with 0.5% methanol induction in this study. The copy number was used to compare the expression level and stability. The colony that survived on a solid medium containing 2000 μg/ml of Zeocin was selected and cultured to express HPV 52 L1. DNA was extracted from the chosen colony, and the copy was determined using qPCR. HPV 52 L1 protein was then purified through fast performance liquid chromatography. Transmission electron microscopy (TEM) evaluation confirmed the VLP self-assembly. The genomic DNA remained intact after 100 generations of serial cultivation under no selective pressure medium conditions, and the protein produced was relatively stable. However, the band intensity was slightly lower than in the parental colony. In terms of copy number, a low copy transformant resulted in low expression but produced a highly stable recombinant clone. Eventually, the L1 protein expressed in Pichia pastoris can self-assemble into VLP. Therefore, recombinant HPV possesses a stable clone and the ability to self-assemble into VLP. ConclusionThe recombinant L1 HPV 52 protein is successfully expressed in P. pastoris within a size range of approximately 55 kDa and demonstrated favorable stability. The L1 protein expressed in Pichia pastoris successful self-assembled of HPV VLPs, thereby establishing their potential efficacy as a prophylactic vaccine.

Weight and protozoa number but not bacteria diversity are associated with successful pair formation of dealates in the Formosan subterranean termite, Coptotermes formosanus.

New colonies of Formosan subterranean termites are founded by monogamous pairs. During swarming season, alates (winged reproductives) leave their parental colony. After swarming, they drop to the ground, shed their wings, and male and female dealates find suitable nesting sites where they mate and become kings and queens of new colonies. The first generation of offspring is entirely dependent on the nutritional resources of the founder pair consisting of the fat and protein reserves of the dealates and their microbiota, which include the cellulose-digesting protozoa and diverse bacteria. Since termite kings and queens can live for decades, mate for life and colony success is linked to those initial resources, we hypothesized that gut microbiota of founders affect pair formation. To test this hypothesis, we collected pairs found in nest chambers and single male and female dealates from four swarm populations. The association of three factors (pairing status, sex of the dealates and population) with dealate weights, total protozoa, and protozoa Pseudotrichonympha grassii numbers in dealate hindguts was determined. In addition, Illumina 16S rRNA gene sequencing and the QIIME2 pipeline were used to determine the impact of those three factors on gut bacteria diversity of dealates. Here we report that pairing status was significantly affected by weight and total protozoa numbers, but not by P. grassii numbers and bacteria diversity. Weight and total protozoa numbers were higher in paired compared to single dealates. Males contained significantly higher P. grassii numbers and bacteria richness and marginally higher phylogenetic diversity despite having lower weights than females. In conclusion, this study showed that dealates with high body weight and protozoa numbers are more likely to pair and become colony founders, probably because of competitive advantage. The combined nutritional resources provided by body weight and protozoa symbionts of the parents are important for successful colony foundation and development.

Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides.

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm3) capable of generating an electron density of greater than 1013 cm-3 was constructed to produce reactive species (N2*, N2+, O, OH, and Hα) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

Separation aggression: A captive study on two Indian ant species, Camponotus compressus (Fabricius 1787) and Tetraponera rufonigra (Jerdon 1851) (Hymenoptera: Formicidae)

We studied the aggression reaction of two Indian ant species, Camponotus compressus and Tetraponera rufonigra, using both the species either as a resident and/or intruders to each other and to conspecifics in the ant box to observe whether or not they were showing the reaction towards conspecific and interspecific in the captivity at different time points of isolation from the parental colony. The study revealed a strong and positive correlation between the degree of aggression and the duration of remaining in isolation from the parental colony. A shorter aggression time was recorded during the short period of separation but with more time of isolation, the aggression time increased to a great extent. With time, the ants in the formicarium lost the original body odour, which caused the conspecific to become distant, and aggression followed. Conspecifics of non-parental colonies also exhibited aggression reaction in both the ant species under study, therefore, it can be stated that aggression could not only be due to the body odour dilution, rather there could be an additional factor. The gradual increase in the ambient temperature might play a role. During the change in season from winter to summer the ambient temperature was increasing and the ants were getting active and became more aggressive. We observed a differential aggression in the interspecific reaction and this may be due to the different genetic compositions between them. Keywords: Camponotus, Tetraponera, Ants

Coral affected by stony coral tissue loss disease can produce viable offspring.

Stony coral tissue loss disease (SCTLD) has caused high mortality of at least 25 coral species across the Caribbean, with Pseudodiploria strigosa being the second most affected species in the Mexican Caribbean. The resulting decreased abundance and colony density reduces the fertilization potential of SCTLD-susceptible species. Therefore, larval-based restoration could be of great benefit, though precautionary concerns about disease transmission may foster reluctance to implement this approach with SCTLD-susceptible species. We evaluated the performance of offspring obtained by crossing gametes of a healthy P. strigosa colony (100% apparently healthy tissue) with that of a colony affected by SCTLD (>50% tissue loss) and compared these with prior crosses between healthy parents. Fertilization and settlement were as high as prior crosses among healthy parents, and post-settlement survivorship over a year in outdoor tanks was 7.8%. After thirteen months, the diseased-parent recruits were outplanted to a degraded reef. Their survivorship was ∼44% and their growth rate was 0.365 mm ± 1.29 SD per month. This study shows that even diseased parent colonies can be effective in assisted sexual reproduction for the restoration of species affected by SCTLD.

Rampant asexual reproduction and limited dispersal in a mangrove population of the coral Porites divaricata.

Corals are critical to marine biodiversity. Reproduction and dispersal are key to their resilience, but rarely quantified in nature. Exploiting a unique system-a fully censused, longitudinally characterized, semi-isolated population inhabiting mangroves-we used 2bRAD sequencing to demonstrate that rampant asexual reproduction most likely via parthenogenesis and limited dispersal enable the persistence of a natural population of thin-finger coral (Porites divaricata). Unlike previous studies on coral dispersal, knowledge of colony age and location enabled us to identify plausible parent-offspring relationships within multiple clonal lineages and develop tightly constrained estimates of larval dispersal; the best-fitting model indicates dispersal is largely limited to a few metres from parent colonies. Our results explain why this species is adept at colonizing mangroves but suggest limited genetic diversity in mangrove populations and limited connectivity between mangroves and nearby reefs. As P. divaricata is gonochoristic, and parthenogenesis would be restricted to females (whereas fragmentation, which is presumably common in reef and seagrass habitats, is not), mangrove populations likely exhibit skewed sex ratios. These findings suggest that coral reproductive diversity can lead to distinctly different demographic outcomes in different habitats. Thus, coral conservation will require the protection of the entire coral habitat mosaic, and not just reefs.

Evidence of cospeciation between termites and their gut bacteria on a geological time scale.

Termites host diverse communities of gut microbes, including many bacterial lineages only found in this habitat. The bacteria endemic to termite guts are transmitted via two routes: a vertical route from parent colonies to daughter colonies and a horizontal route between colonies sometimes belonging to different termite species. The relative importance of both transmission routes in shaping the gut microbiota of termites remains unknown. Using bacterial marker genes derived from the gut metagenomes of 197 termites and one Cryptocercus cockroach, we show that bacteria endemic to termite guts are mostly transferred vertically. We identified 18 lineages of gut bacteria showing cophylogenetic patterns with termites over tens of millions of years. Horizontal transfer rates estimated for 16 bacterial lineages were within the range of those estimated for 15 mitochondrial genes, suggesting that horizontal transfers are uncommon and vertical transfers are the dominant transmission route in these lineages. Some of these associations probably date back more than 150 million years and are an order of magnitude older than the cophylogenetic patterns between mammalian hosts and their gut bacteria. Our results suggest that termites have cospeciated with their gut bacteria since first appearing in the geological record.

A caste differentiation mutant elucidates the evolution of socially parasitic ants

Most ant species have two distinct female castes-queens and workers-yet the developmental and genetic mechanisms that produce these alternative phenotypes remain poorly understood. Working with a clonal ant, we discovered a variant strain that expresses queen-like traits in individuals that would normally become workers. The variants show changes in morphology, behavior, and fitness that cause them to rely on workers in wild-type (WT) colonies for survival. Overall, they resemble the queens of many obligately parasitic ants that have evolutionarily lost the worker caste and live inside colonies of closely related hosts. The prevailing theory for the evolution of these workerless social parasites is that they evolve from reproductively isolated populations of facultative intermediates that acquire parasitic phenotypes in a stepwise fashion. However, empirical evidence for such facultative ancestors remains weak, and it is unclear how reproductive isolation could gradually arise in sympatry. In contrast, we isolated these variants just a few generations after they arose within their WT parent colony, implying that the complex phenotype reported here was induced in a single genetic step. This suggests that a single genetic module can decouple the coordinated mechanisms of caste development, allowing an obligately parasitic variant to arise directly from a free-living ancestor. Consistent with this hypothesis, the variants have lost one of the two alleles of a putative supergene that is heterozygous in WTs. These findings provide a plausible explanation for the evolution of ant social parasites and implicate new candidate molecular mechanisms for ant caste differentiation.

Honey bees reared in isolation adhere to normal age-related division of labor when reintroduced into a colony

Early social experiences during developmental life stages have been demonstrated to influence adult behavior in vertebrates and invertebrates. However, cooperative behaviors observed in social insects are often regarded as simple instinctual responses to positive and negative feedback. Here we test if rearing environment influences the resulting adult bee’s somewhat predictable progression through a series of age-related tasks (temporal polyethism). Honey bee larvae were reared either in their parental colony, or artificially in the laboratory. Newly emerged adults were individually identified and introduced into a single observation hive where their behavior was observed three times a day for 28 days. In vitro-reared bees were observed engaging in every behavior in which colony-reared bees engaged including: attending the queen, manipulating wax comb, defending the hive entrance, and foraging. Moreover, in vitro-reared bees appeared to be responding appropriately to colony-level cues that coordinate task allocation within age-related polyethism. However, in vitro-reared bees did suffer detectably reduced lifespans. Further research, potentially incorporating methods such as establishing colonies composed exclusively of in vitro-reared bees, would offer additional insight into the plasticity of honey bee behaviors.

Remarkable population structure in the tropical Atlantic lace corals Stylaster roseus (Pallas, 1766) and Stylaster blatteus (Boschma, 1961)

Biodiversity on coral reefs depends not only on primary reef-builders, but also on associated taxa that create microhabitats for other species. Hydrocorals of the genus Stylaster, commonly known as lace corals, form small branching colonies that enhance three-dimensional complexity on reefs and are known to support a variety of commensal species. Furthermore, the genus is highly speciose, further increasing biodiversity. Despite their important ecological roles, little is known about the evolutionary history and the intraspecific diversity and structure in these broadly distributed hydrocorals. Here, we assessed the phylogenetic relationships among Atlantic species in the genus Stylaster and examined the genetic structure of S. roseus in the Tropical Western Atlantic (Caribbean and Brazil) and of S. blatteus in the Tropical Eastern Atlantic (Africa), using DNA sequences from the 16S ribosomal gene. Time-calibrated phylogenetic analyses showed that S. roseus and S. blatteus diverged at ~ 24.6 Ma. A well-supported Brazilian clade within S. roseus indicates a possible cryptic species that diverged at ~ 11.6 Ma, consistent with the formation of the Amazon River at 9 Ma (Hoorn et al. in Glob Planet Change 153:51–65, 2017). Strong genetic structure was observed even over moderate distances, with ΦST values over all populations being 0.98 for S. roseus and 0.90 for S. blatteus. Nearly, all haplotypes were private (found in a single location) and diverged by many mutational steps from one another. In contrast, genetic diversity was low at the local scale for both species, with most sites showing no variation (a single haplotype). These results are coherent with the reproductive strategy of Stylasteridae, where larvae are brooded and are highly developed at the time of release, often settling near the parental colony. Limited dispersal coupled with possible clonal reproduction have likely contributed to the high levels of genetic differentiation observed here. Lace corals show unusual reproductive and population dynamics compared to other reef inhabiting cnidarians. Future work may reveal additional cryptic diversity in this poorly studied family.

Environments and Hosts Structure the Bacterial Microbiomes of Fungus-Gardening Ants and their Symbiotic Fungus Gardens.

The fungus gardening-ant system is considered a complex, multi-tiered symbiosis, as it is composed of ants, their fungus, and microorganisms associated with either ants or fungus. We examine the bacterial microbiome of Trachymyrmex septentrionalis and Mycetomoellerius turrifex ants and their symbiotic fungus gardens, using 16S rRNA Illumina sequencing, over a region spanning approximately 350km (east and central Texas). Typically, microorganisms can be acquired from a parent colony (vertical transmission) or from the environment (horizontal transmission). Because the symbiosis is characterized by co-dispersal of the ants and fungus, elements of both ant and fungus garden microbiome could be characterized by vertical transmission. The goals of this study were to explore how both the ant and fungus garden bacterial microbiome are acquired. The main findings were that different mechanisms appear to explain the structure the microbiomes of ants and their symbiotic fungus gardens. Ant associated microbiomes had a strong host ant signature, which could be indicative of vertical inheritance of the ant associated bacterial microbiome or an unknown mechanism of active uptake or screening. On the other hand, the bacterial microbiome of the fungus garden was more complex in that some bacterial taxa appear to be structured by the ant host species, whereas others by fungal lineage or the environment (geographic region). Thus bacteria in fungus gardens appear to be acquired both horizontally and vertically.

Genetic Variation in Heat Tolerance of the Coral Platygyra Daedalea Indicates Potential for Adaptation to Ocean Warming

Ocean warming represents the greatest threat to the persistence of reef ecosystems. Most coral populations are projected to experience temperatures above their current bleaching thresholds annually by 2050. Adaptation to higher temperatures is necessary if corals are to persist in a warming future. While many aspects of heat stress have been well studied, few data are available for predicting the capacity for adaptive cross-generational responses in corals. Consistent sets of heat tolerant genomic markers that reliably predict thermal tolerance have yet to be identified. To address this knowledge gap, we quantified the heritability and genetic variation associated with heat tolerance in Platygyra daedalea from the Great Barrier Reef. We tracked the survival of ten quantitative genetic crosses of larvae produced form six parental colonies in a heat tolerance selection experiment. We also identified allelic shifts in heat-selected (35°C) survivors compared with paired, non-selected controls (27°C). The narrow-sense heritability of survival under heat stress was 0.66 and a total of 1,069 single nucleotide polymorphisms (SNPs) were associated with different survival probabilities. While 148 SNPs were shared between several experimental crosses, no common SNPs were identified for all crosses, which suggests that specific combinations of many markers are responsible for heat tolerance. However, we found two regions that overlap with previously identified loci associated with heat tolerance in Persian Gulf populations of P. daedalea, which reinforces the importance of these markers for heat tolerance. These results illustrate the importance of high heritability and the complexity of the genomic architecture underpinning host heat tolerance. These findings suggest that this P. daedalea population has the genetic prerequisites for adaptation to increasing temperatures. This study also provides knowledge for the development of high throughput genomic tools which may screen for variation within and across populations to enhance adaptation through assisted gene flow and assisted migration.

Multiple Alr genes exhibit allorecognition-associated variation in the colonial cnidarian Hydractinia

The genetics of allorecognition has been studied extensively in inbred lines of Hydractinia symbiolongicarpus, in which genetic control is attributed mainly to the highly polymorphic loci allorecognition 1 (Alr1) and allorecognition 2 (Alr2), located within the Allorecognition Complex (ARC). While allelic variation at Alr1 and Alr2 can predict the phenotypes in inbred lines, these two loci do not entirely predict the allorecognition phenotypes in wild-type colonies and their progeny, suggesting the presence of additional uncharacterized genes that are involved in the regulation of allorecognition in this species. Comparative genomics analyses were used to identify coding sequence differences from assembled chromosomal intervals of the ARC and from genomic scaffold sequences between two incompatible H. symbiolongicarpus siblings from a backcross population. New immunoglobulin superfamily (Igsf) genes are reported for the ARC, where five of these genes are closely related to the Alr1 and Alr2 genes, suggesting the presence of multiple Alr-like genes within this complex. Complementary DNA sequence evidence revealed that the allelic polymorphism of eight Igsf genes is associated with allorecognition phenotypes in a backcross population of H. symbiolongicarpus, yet that association was not found between parental colonies and their offspring. Alternative splicing was found as a mechanism that contributes to the variability of these genes by changing putative activating receptors to inhibitory receptors or generating secreted isoforms of allorecognition proteins. Our findings demonstrate that allorecognition in H. symbiolongicarpus is a multigenic phenomenon controlled by genetic variation in at least eight genes in the ARC complex.

Effects of elevated temperature on reproduction and larval settlement in Leptastrea purpurea.

As global ocean temperatures continue to rise, severe declines in coral reef health and diversity are reported on a global scale. Recovery of coral reefs relies on reproduction and increased rates of successful recruitment, which can vary tremendously across coral species. We investigated the effects of increased temperatures in the environment of parental colonies on larval production, size, settlement and survival, in the heat-resistant coral Leptastrea purpurea in Guam. Thanks to two tank experiments (eleven and four weeks, respectively) conducted over two consecutive years we found that larvae released by heat-treated parents (30 °C) were significantly smaller in size but greater in number, had normal settlement behavior and increased post-settlement survival rates compared to those released by control parent colonies (28 °C). We conclude that changes in the environment of parental L. purpurea colonies trigger an anticipatory maternal effect which leads to the release of preconditioned larvae with an increased chance of survival.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00338-022-02241-y.

Formation of α-segregation and its impact on grain refinement in Ti-47.5Al-5Nb-2.5V-1Cr alloy

This paper presents a method for refining the coarse lamellar colonies in α-solidified TiAl alloys using α-segregation. The prerequisite of this method is control of the solidification rate. Isothermal holding at upper and/or middle of α phase region and control of cooling rate from α to (α+γ) phase region is also necessary for better refinement. In addition, the formation of α-segregation and characteristics of the refined lamellar colonies are studied. The results show that the formation of α-segregation is mainly related to the change of the phase transformation path caused by Al-depletion. Moreover, α-segregation is composed of two kinds of β phases, which can be distinguished by orientation relationship with matrix colony. Although the coarse colonies are refined, the refined colonies exhibit the same orientation as the parent colonies. Besides, the degree of α-segregation and the type of β phase will affect the local characteristics of the refined lamellar colonies.