Molt Stage Research Articles

Effects of chronic hypercapnia and elevated temperature on the immune response of the spiny lobster, Jasus lalandii

The West Coast rock lobster (WCRL), Jasus lalandii, inhabits highly variable environments frequented by upwelling events, episodes of hypercapnia and large temperature variations. Coupled with the predicted threat of ocean acidification and temperature change for the coming centuries, the immune response in this crustacean will most likely be affected. We therefore tested the hypothesis that chronic exposure to hypercapnia and elevated seawater temperature will alter immune function of the WCRL. The chronic effects of four combinations of two stressors (seawater pCO2 and temperature) on the total number of circulating haemocytes (THC) as well as on the lobsters’ ability to clear (inactivate) an injected dose of Vibrio anguillarum from haemolymph circulation were assessed. Juvenile lobsters were held in normocapnic (pH 8.01) or hypercapnic (pH 7.34) conditions at two temperatures (15.6 and 18.9 °C) for 48 weeks (n = 30 lobster per treatment), after which a subsample of lobsters (n = 8/treatment), all at a similar moult stage, were selected from each treatment for the immune challenge. Baseline levels of haemocytes (THC ml−1) and bacteria (CFU ml−1) in their haemolymph were quantified 24 h prior to bacterial challenge. Lobsters were then challenged by injecting 4 × 104V. anguillarum per g body weight directly into the cardiac region of each lobster and circulating haemocyte and culturable bacteria were measured at 20 min post challenge. No significant differences in THC ml−1 (p < 0.05) were observed between any of the treatment groups prior to the bacterial challenge. However lobsters chronically exposed to a combination of hypercapnia and low temperature had significantly higher (p < 0.05) THCs post-challenge in comparison with lobsters chronically exposed to hypercapnia and high temperature. A significant interactive effect was recorded between temperature and pH for the post-challenge THC data (two-way ANOVA, p = 0.0025). Lobster were very efficient at rendering an injected dose of bacteria non-culturable, with more than 83% of the theoretical challenge dose (∼1.7 × 105Vibrio ml−1 haemolymph) inactivated within the first 10 min following injection. Although differences in the inactivation of V. anguillarum were observed between treatment groups, none of these differences were significant. Clearance efficiency was in the following order: Hypercapnia/low temperature > normocapnia/high temperature > normocapnia/low temperature > hypercapnia/high temperature. This study demonstrated that despite chronic exposure to combinations of reduced seawater pH and high temperature, the WCRL was still capable of rapidly rendering an injected dose of bacteria non-culturable.

Identification and comparative analysis of Eriocheir sinensis microRNA transcriptome from claw muscles related molting

Molting is a critical developmental process for crustaceans, during which the claw muscles undergo periodic atrophy and restoration. The regulatory mechanism of this special muscle reshuffle around ecdysis was not clear. To investigate the molecular mechanism underlying the muscle changes in crustaceans, we used Illumina/Solexa deep sequencing technology to sequence small RNA libraries prepared from claw muscles of Eriocheir sinensis in three molting stages (inter-molt C stage, later pre-molt D3–4 stage and post molt A–B stage). The sequencing resulted in 8,054,808, 9,944,487 and 10,202,589 high-quality clean reads, corresponding to 2767, 2676, and 2891 unique miRNAs for the A–B, C and D3–4 stage samples, respectively. Bioinformatic analyses identified 1485 mature miRNAs, among which 1392 miRNAs belong to 218 miRNA families and 93 miRNAs belong to unknown families. Altogether, 115 miRNAs were differentially expressed among the three molting stages, and they were clustered into 5 subclusters according to their expression patterns. GO and KEGG analysis revealed that the predicted targets of the differentially expressed miRNAs are particularly associated with gene expression, protein degradation and synthesis, muscle atrophy and development, post-embryonic morphogenesis, and anatomical structure development. Our findings suggest that the differentially expressed miRNAs and their target genes play important roles in growth and development of crab muscles induced by molting.

Moult-related reduction of aerobic scope in passerine birds.

It is well established that the nutrient and energy requirements of birds increase substantially during moult, but it is not known if these increased demands affect their aerobic capacity. We quantified the absolute aerobic scope of house and Spanish sparrows, Passer domesticus and P. hispaniolensis, respectively, before and during sequential stages of their moult period. The absolute aerobic scope (AAS) is the difference between maximum metabolic rate (MMR) during peak locomotor activities and minimum resting metabolic rate (RMRmin), thus representing the amount of aerobic power above that committed to maintenance needs available for other activities. As expected, RMRmin increased over the moult period by up to 40 and 63% in house and Spanish sparrows, respectively. Surprisingly, the maximum metabolic rates also decreased during moult in both species, declining as much as 25 and 38% compared with pre-moult values of house and Spanish sparrows, respectively. The concurrent changes in RMRmin and MMR during moult resulted in significant decreases in AAS, being up to 32 and 47% lower than pre-moult levels of house and Spanish sparrows, respectively, during moult stages having substantial feather replacement. We argue that the combination of reduced flight efficiency due to loss of wing feathers and reduced aerobic capacity places moulting birds at greater risk of predation. Such performance constraints likely contribute to most birds temporally separating moult from annual events requiring peak physiological capacity such as breeding and migration.

Flight feather moult in Western Marsh Harriers during autumn migration

BackgroundMost of long-distance migratory raptors suspend moult during migration but detailed information is patchy for most of the Palearctic species. The aim of this research is to verify if active moulting in migrating Western Marsh Harriers occurs and to quantify the extent of moulting along the season focusing on primary feathers.MethodsDuring a whole post-breeding migration at the Strait of Messina in Southern Italy, we gathered information about symmetrical flight feather moult from 221 adults by taking pictures of raptors passing at close range.ResultsWe found active moulting primaries during autumn migration in 48.4% of our samples. Slight differences on the extension and timing among sex classes were recorded during the season, with adult females showing a more advanced moult stage than adult males.ConclusionThe finding that the extension of the suspended moult was already defined in migratory individuals might be explained as an adaptation to minimize the energy required for moulting during migration.

Molt-dependent transcriptome analysis of claw muscles in Chinese mitten crab Eriocheir sinensis

Molting is a critical developmental process for crustaceans, during which the claw muscles undergo periodic atrophy and restoration. But the mechanism underlying this special muscle reshuffle around ecdysis is not yet thoroughly understood. To investigate the molecular mechanism underlying the muscle's reshuffle over the molting cycle of Chinese mitten crab Eriocheir sinensis. The Illumina high-throughput sequencing technique were used to sequence the transcriptome of the whole claw muscles from Chinese mitten crab Eriocheir sinensis in three molting stages (inter-molt C stage, pre-molt D3-4 and post-molt A-B stage); the de novo assembly, annotation and functional evaluation of the contigs were performed with bioinformatics tools. Totally 129,149 unigenes, 128,190 CDS, 33,770 SSRs and a large number of SNP sites were obtained, and 3700 and 12,771 differentially expressed genes (DEGs) were identified respectively in A-B and D3-4 stage compared with that in C stage. The identified DEGs were enriched to 746 and 1 408 GO terms respectively in A-B and D3-4 stage compared with C stage (p ≤ 0.05). KEGG pathway analysis showed that the DEGs were significantly enriched in 14 and 11 pathways in A-B vs C comparison and D3-4 vs C comparison (p ≤ 0.05), respectively. These DEGs are involved in several biological processes critical for the animal's growth and development, such as gene expression, protein synthesis, muscle development, new cuticle reconstruction, oxidation-reduction process and glycolytic process. The data generated in this study is the first transcriptomic resource from the muscles of Chinese mitten crab, which would facilitate to characterize key molecular processes underlying crab muscle's growth and development during the molting cycles.

20-Hydroxyecdysone regulates the transcription of the lysozyme via Broad-Complex Z2 gene in silkworm, Bombyx mori

Broad-Complex Z2 (Br-C Z2) is an ecdysone inducible transcription factor that regulates physiological, innate immune and developmental events in insects. Here, we identified an orthologue of Br-C Z2 from silkworm, Bombyx mori (BmBr-C Z2) to study its involvement in immune responses. The quantitative real-time PCR analysis revealed that BmBr-C Z2 was expressed ubiquitously in all tested tissues under normal physiological conditions. Further, developmental profile displayed that BmBr-C Z2 expression was detectable in different developmental stages, however the gene's expression was highest in the molting and pre-pupal stages. Administration of 20-hydroxyecdysone (20E) enhanced the expression levels of BmBr-C Z2 in hemocytes. The challenge with pathogens and pathogen associated molecular patterns (PAMPs) also upregulated the mRNA levels of BmBr-C Z2 in hemocytes when compared with the control. By contrast, the ectopic expression of BmBr-C Z2 remarkably increased the production of antimicrobial peptides, while the knock-down of this gene by double stranded RNA decreased their production. Dual-luciferase assay exhibited that BmBr-C Z2 induced the expression of lysozyme by directly binding to its promoter region. The treatment of Escherichia coli following the knock-down of BmBr-C Z2 strongly reduced the survival rate of silkworm larvae. These results suggest that BmBr-C Z2 plays an important biological role in the innate immune responses of silkworm by regulating immune-related genes.

Identification and RNAi-based function analysis of chitinase family genes in diamondback moth, Plutella xylostella.

Insect chitinases play a vital part in chitin degradation in exoskeletons and gut linings during the molting process, and therefore are considered potential targets for new insecticide designs or RNA interference (RNAi)-based pest management. Systematic functional analysis of chitinase genes has already been conducted in several insect pests, but not Plutella xylostella. In this study, 13 full-length chitinase transcripts were obtained in P. xylostella. Developmental and tissue-specific expression pattern analysis revealed that seven chitinase transcripts were periodically expressed during molting stage and mainly expressed in the integument or midgut, including PxCht3, PxCht5, PxCht6-2, PxCht7, PxCht8, PxCht10 and PxCht-h. RNAi-mediated knockdown of these specific expressed genes revealed that PxCht5 and PxCht10 were essential in larval molting, pupation and eclosion, and PxCht7 was indispensable only in eclosion. No significant effects were observed on insect survival or normal development when the rest chitinase transcripts were suppressed by RNAi. Our results indicated the function of P. xylostella chitinase family genes during the molting process, and may provide potential targets for RNAi-based management of P. xylostella. © 2018 Society of Chemical Industry.

Vrille is required for larval moulting and metamorphosis of Helicoverpa armigera (Lepidoptera: Noctuidae).

Vrille (Vri), a basic leucine zipper transcription factor, plays important roles in insect circadian clock regulation, tracheal development, proliferation, flight and metamorphosis. Here, Helicoverpa armigera was used as a model to investigate the role of Vri in larval moulting and metamorphosis. Sequence analysis results revealed that H.armigera Vri (HaVri) shares a high amino acid identity with other Lepidoptera Vri homologues. Spatial-temporal expression pattern data showed that HaVri expression was highly abundant in larval moulting and metamorphosis stages and was mainly expressed in the midgut and Malpighian tubule during metamorphosis. HaVri knockdown by RNA interference in the fourth-instar larvae prevented larval moulting, and HaVri knockdown in the fifth-instar larvae suppressed midgut remodelling and delayed or blocked metamorphosis. Further studies confirmed that 20-hydroxyecdysone (20E) activated HaVri expression via its heterodimer receptors, ecdysone receptor (EcRB1) and ultraspiracle protein (USP1), whereas methoprene [juvenile hormone analogue (JHA)] promoted HaVri expression via its intracellular receptor methoprene-tolerant (Met1). However, 20E and JHA can counteract each other in the activation of HaVri expression. Together, the present results suggested that HaVri was involved in larval moulting and metamorphosis and was regulated by 20E and JHA in H.armigera.

Postembryonic development of the Tri-spine Horseshoe Crab Tachypleus tridentatus (Merostomata: Xiphosura) in a nursery habitat in the Philippines

Populations of the Tri-spine Horseshoe Crab Tachypleus tridentatus have dramatically decreased over their distribution range and conservation efforts are now crucial. The implementation of appropriate management strategies and stock assessment rely on accurate growth-rate estimates. The postembryonic development of the species in the tropics, however, is not elucidated. To provide the information needed to assess the demographics of juvenile populations and to judge the status of T. tridentatus in the Philippines, we conducted a mark-recapture experiment in a nursery habitat on Palawan Island. The results obtained during the 10-month period provide the first consecutive data on the stepwise growth of the species in the Philippines and the first near comprehensive dataset collected within a single population of juveniles in the tropics. By analyzing size-frequency (prosomal width) distributions of 853 individuals and by using 94 juveniles that molted during the study, 13 molt stages were differentiated. Based on the intermolt periods of six instars, we estimated the growth curve of T. tridentatus following two models (non-linear and power function). The data support the assumption that growth continues year-round in the tropics and also indicate that the average age of mature male and female T. tridentatus in the Philippines ranges from three to four years. The agreement with a field study in Japan suggests that 14 postembryonic stages may be characteristic for the development of natural populations throughout the range of the species. Though more data are needed to validate these results, the study provides a sound baseline for future studies in the tropics.

Evaluating the impact of moulting and chilled storage of spermatophores on the integrity of plasma membrane, acrosome and DNA of black tiger prawn ( Penaeus monodon ) spermatozoa

To explore the impact of moulting and short-term chilled storage of spermatophores on the sperm quality for a commercially important penaeid prawn, spermatozoa of Penaeus monodon from early (B-C), middle (D0-1) and late (D2-3) moult stages were compared for sperm quality parameters relating to the structural integrity of plasma membrane (Viab%), acrosome (AR%) and DNA (SDF%) after being stored at 4°C for 0–26 days. The three different sperm extenders used for chilled storage included artificial lobster haemolymph (AH), calcium free saline (CS) and filtered seawater (FS); two storage conditions were applied either as a free sperm suspension or retained within the intact spermatophore. Results showed that (a) the lowest natural AR% was shown for B-C spermatozoa in CS whereas the highest levels were for B-C, D0-1 and D2-3 spermatozoa in FS and D2-3 spermatozoa in AH; (b) the calcium ionophore A23187 agent used in this study was able to increase the mean AR% by 6.22%; (c) the Viab% was significantly lower in CS than that in FS; (d) the SDF% significantly increased over the period of chilled storage for B-C and D0-1 spermatozoa, while the SDF% of D2-3 spermatozoa was initially elevated and did not change significantly over time; and (e) there was no difference in sperm quality between two storage conditions. This study has successfully demonstrated the moult-related variance in the percentages of acrosome-reacted and DNA-damaged spermatozoa, providing evidence of moult-related spermatophore renewal cycle in this species.

Expanding the traditional definition of molt-migration

ABSTRACT The occurrence of molt during migration, known as “molt-migration,” has increasingly received attention across many avian taxa since first being described in waterfowl in the 1960s. However, despite the many different types of molt stages and strategies, most, if not all, uses of the term “molt-migration” apply to the definitive prebasic molt of flight feathers in post-breeding adults, whereas fewer studies address migration for body-feather molts. Here, we argue that the current definition of molt-migration, as applied, is limited in focus relative to the diverse ways in which it can manifest in avian populations. We suggest a new, broader definition of molt-migration and highlight examples of molt-migration as traditionally defined, and the many examples that have not been defined as such. We propose a new, 2-tiered typology for defining different forms of molt-migration, based on (1) its progression relative to stationary portions of the annual cycle, and (2) the stage of molt involved. In ord...

Osmoregulation Pattern of Fingerling Vanname Shrimp (Litopenaeus vannamei) Rearing in Three Molt Stage Iso-Osmotic Media

Vanname shrimp (Litopenaeus vannamei) is one of euryhaline Crustacean that able to adapt to a wider range of salinities. The need of suitable media for a given size and molting stage of shrimp is a key factor of the success of shrimp culture. In order to ensure the success of fingerling Vanname shrimp (FVS) rearing, it is indispensable to provide suitable osmotic media for the molting process. This research was aimed to examine and determine isoosmotic media that complies with physiological process of FVS. The research was done in laboratory scale with Completely Randomized Design. FVS was acclimated to three salinities level i.e. 15-16 ‰ as the postmolt isosmotic media, 25-26 ‰ as the intermolt isosmotic media, and 29-30 ‰ as the premolt and molt isosmotic media with three replications. The result showed that in the media of 25-26 ‰, the osmotic work revealed the minimal level and it enhanced the growth rate without changing the amino acids composition in the shrimp body tissue.

Sexual dimorphism in adult Little Stints (Calidris minuta) revealed by DNA sexing and discriminant analysis.

BackgroundThe sex of an individual organism plays such an important role in its life cycle that researchers must know a bird’s sex to interpret key aspects of its biology. The sexes of dimorphic species can be easily distinguished, but sexing monomorphic bird species often requires expensive and time-consuming molecular methods. The Little Stint (Calidris minuta) is a numerous species, monomorphic in plumage but showing a small degree of reversed sexual size dimorphism. Females are larger than males but the ranges of their measurements overlap, making Little Stints difficult to sex in the field. Our aim was to develop reliable sexing criteria for Little Stints in different stages of primary moult during their stay on the non-breeding grounds in South Africa using DNA-sexed individuals and discriminant function analysis.MethodsWe caught 348 adult Little Stints in 2008–2016 on their non-breeding grounds at Barberspan Bird Sanctuary. To molecularly identify the birds’ sex we used P2/P8 primers and DNA isolated from blood samples collected in the field. We used Storer’s dimorphism index to assess the degree of sexual size dimorphism. Then we divided our sample into two groups: before or during and after primary moult. For each group we developed two functions: one using wing length only and the other a combination of morphometric features including wing, tarsus and total head length. Then we used a stepwise procedure to check which combination of measurements best discriminated sexes. To validate our result we used a jack-knife cross-validation procedure and Cohen-kappa statistics.ResultsAll the morphometric features we measured were bigger in DNA-sexed females than in males. Birds with fresh primaries had on average 2.3 mm longer wings than those with worn primaries. A discriminant function using wing length (D1) correctly sexed 78.8% of individuals before moult, and a stepwise analysis showed that a combination of wing length and tarsus (D2) correctly identified the sex of 82.7% of these birds. For birds with freshly moulted primaries a function using wing length (D3) correctly classified 83.4% of the individuals, and a stepwise analysis revealed that wing and total head length (D4) classified 84.7%.DiscussionSexual size differences in Little Stints might be linked to their phylogenetics and breeding biology. Females are bigger, which increases their fecundity; males are smaller, which increases their manoeuverability during display flights and hence their mating success. Little Stints show an extreme lack of breeding site fidelity so we did not expect a geographical cline in their biometrics. Sexing criteria available for Little Stints in the literature were developed using museum specimens, which often shrink, leading to misclassification of live birds. The sexing criteria we developed can be used for studies on Little Stints at their non-breeding grounds and on past data, but should be applied cautiously because of the overlapping ranges.

20-Hydroxyecdysone-upregulated proteases involved in Bombyx larval fat body destruction.

During insect larval-pupal metamorphosis, the obsolete larval organs and tissues undergo histolysis and programmed cell death to recycle cellular materials. It has been demonstrated that some cathepsins are essential for histolysis in larval tissues, but the process of tissue destruction is not well documented. Fat body, the homologous organ to mammalian liver and adipose tissue, goes through a distinct destruction process during larval-pupal transition. Herein, we found that most of the Bombyx proteases - including Bombyx cathepsin B (BmCatB) (BmCatLL-2), Bombyx cathepsin D (BmCatD), Bombyx cathepsin L like-1 (BmCatLL-1) and -2(BmCatLL-2), Bombyx fibroinase (BmBcp), Bombyx matrix metalloprotease (BmMmp), Bombyx A disintegrin and metalloproteinase with thrombospondin motifs 1 (BmAdamTS-1), Bombyx A disintegrin and metalloproteinase with thrombospondin motifs like (BmAdamTS L) and Bombyx cysteine protease inhibitor (Bmbcpi)- were expressed highly in fat body during feeding and metamorphosis, with a peak occurring during the nonfeeding moulting or prepupal stage, as well as being responsive to 20-hydroxyecdysone (20E). The aforementioned protease genes expression was upregulated by injection of 20E into the feeding larvae, while blocking 20E signalling transduction led to downregulation. Western blotting and immunofluorescent staining of BmCatB and BmBcp confirmed the coincident variation of their messenger RNA (mRNA) and protein level during the development and after the treatments. Moreover, BmCatB, BmBcp, BmMmp and BmAdamTS-1 RNA interference all led to blockage of larval fat body destruction. Taken together, we conclude that 20E regulates larval fat body destruction by upregulating related protease gene expression and protein levels during larval-pupal transition.

Age and sex differences in niche use at molt and its effect on plumage coloration characteristics in a bird.

Bird plumage is often very colorful and can communicate the quality of the bearer to conspecifics. These plumage-based signals of quality are composed of multiple pigments (e.g., melanin and carotenoids). Therefore, sex and age classes, which often show marked differences in plumage coloration, may have different dietary needs for the different plumage components and this might promote preferences for different dietary niches at different molting stages. However, no study has addressed the role that changes in niche use play in the expression of multiple component plumage signals in birds. We used stable isotope analysis to test the hypothesis that niche use is related to age and sex and to differently cultured plumage patches, yellow carotenoid-based and black melanin-based, in great tits Parus major. We recorded high niche overlap between plumage patches, although δ15N was higher in black than yellow plumage. Niche overlap was relatively low for age classes and relatively high for sex classes, and age classes showed a contrasting pattern of niche overlap between carotenoid- and melanin-based plumages. Moreover, δ13C, but not δ15N, had a significant negative relationship with carotenoid-based plumage, which was only apparent in juveniles. Taken together, our results demonstrate that niche use had a moderate influence on plumage coloration characteristics of great tit individuals, mostly associated with δ13C rather than with δ15N and with age rather than with sex. Therefore, our study is significant because it confirms the relevance of niche use during ornament production in free-living birds.

Egg size is independent of variation in pre-breeding feather corticosterone in Cassin’s auklets during favorable oceanographic conditions

The measurement of corticosterone levels in feathers (fCort) is gaining recognition as an effective means for describing links between stages of the annual cycle in birds. Many seabirds are especially good models for exploring these links, or carryover effects, due to their migratory behavior and reproductive investment in a single-egg clutch. Here, we measure fCort in Cassin’s auklet (Ptychoramphus aleuticus) breast feathers at two colonies in British Columbia during 2011, a year of favorable oceanographic conditions, and examine its relationship with egg size. These feathers are grown at sea during the late winter period, 1–2 months prior to egg laying. Assuming that fCort provides some measure of nutritional stress and hypothalamic-pituitary-adrenal axis activity during feather growth, we predicted that fCort would be positively correlated with egg size via increased support for foraging activity during the nutritionally demanding molt stage. We also analyzed the δ13C and δ15N stable isotope content of breast feathers, measures commonly used to characterize seabird diet composition. Contrary to prediction, neither fCort nor stable isotope ratios were good predictors of egg size. Our results appear to conflict with two previous studies on alcids in which fCort and stable isotopes showed clear links with egg size; however, both studies were conducted in years when oceanographic and foraging conditions were poor. Under these conditions, upregulation of corticosterone may be needed to mediate the energetic tradeoffs between self-maintenance and reproduction, supporting increased foraging effort and thus increasing both the likelihood of reproduction and large egg size. However, when foraging conditions are favorable, we suggest that such tradeoffs and associated physiological constraints are minimized and regulation of egg size may be effectively independent of circulating corticosterone levels and diet type.

Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina).

Southern elephant seals (Mirounga leonina) are known to move and aggregate while molting, but little is known about their behavior on land during this time. In this study, 60 adult females were monitored (23 with GPS tags) during four molting seasons, between 2012 and 2016 at Kerguelen Archipelago, Indian Ocean. Population surveys were recorded each year (N = 230 daily counts), and habitat use was analyzed in relation to the stage of the molt and local weather. Based on stage of molt, habitat use, and movements on land, we classified the molt of elephant seals into three phases: (1) a “search phase” at the initial stage of molt when grass and wallow habitats were used and characterized by greater mean distances travelled on land per day compared with the two other phases; (2) a “resident phase”: during initial and mid‐stage of molt when animals were found in grass and wallow habitats but with less distance moved on land; and (3) a “termination phase” at the final stage of molt where grass and beach habitats were occupied with no change in distances. Windchill and solar radiation influenced individual distances moved per day (mean 590 ± 237.0 m) at the mid‐ and final stage of molt such that animals travelled greater distances on days of low windchill or high solar radiation. Individual variation in distance moved and relative habitat use were also linked to body mass index (BMI) at arrival on the colony, as females with higher BMI moved less and preferred beach habitat. Moreover, the individual rate of molt increased with the use of wallows. Aggregation rate tended to be negatively correlated with distances moved. We therefore suggest that individuals face an energetic trade‐off while molting, balancing energy expenditure between movement and thermoregulation.

Can metamorphosis survival during larval development in spiny lobster Sagmariasus verreauxi be improved through quantitative genetic inheritance?

BackgroundOne of the major impediments to spiny lobster aquaculture is the high cost of hatchery production due to the long and complex larval cycle and poor survival during the many moult stages, especially at metamorphosis. We examined if the key trait of larval survival can be improved through selection by determining if genetic variance exists for this trait. Specifically, we report, for the first time, genetic parameters (heritability and correlations) for early survival rates recorded at five larval phases; early-phyllosoma stages (instars 1–6; S1), mid-phyllosoma stages (instars; 7–12; S2), late-phyllosoma stages (instars 13–17; S3), metamorphosis (S4) and puerulus stage (S5) in hatchery-reared spiny lobster Sagmariasus verreauxi.ResultsThe data were collected from a total of 235,060 larvae produced from 18 sires and 30 dams over nine years (2006 to 2014). Parentage of the offspring and full-sib families was verified using ten microsatellite markers. Analysis of variance components showed that the estimates of heritability for all the five phases of larval survival obtained from linear mixed model were generally similar to those obtained from threshold logistic generalised models (0.03–0.47 vs. 0.01–0.50). The heritability estimates for survival traits recorded in the early larval phases (S1 and S2) were higher than those estimated in later phases (S3, S4 and S5). The existence of the additive genetic component in larval survival traits indicate that they could be improved through selection. Both phenotypic and genetic correlations among the five survival measures studied were moderate to high and positive. The genetic associations between successive rearing periods were stronger than those that are further apart.ConclusionsOur estimates of heritability and genetic correlations reported here in a spiny lobster species indicate that improvement in the early survival especially during metamorphosis can be achieved through genetic selection in this highly economic value species.

Dissecting the role of Krüppel homolog 1 in the metamorphosis and female reproduction of the cotton bollworm, Helicoverpa armigera.

In insects, metamorphosis and reproduction are controlled by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Krüppel homolog 1 (Kr-h1), a transcription factor, is regarded as a JH-early inducible gene responsible for the repression of metamorphosis. However, the role of Kr-h1 in reproduction of holometabolic insects is relatively less understood. In this study, we studied the role of Kr-h1 in larvae-pupae transition and female reproduction in the major agricultural pest Helicoverpa armigera. Two HaKr-h1 isoforms (HaKr-h1α and HaKr-h1ß) were identified, with HaKr-h1α predominant in the cotton bollworm. In larvae, HaKr-h1 was predominately expressed in the epidermis and markedly up-regulated during the moult stage, whereas in adults HaKr-h1 was mainly expressed in females and the highest transcription was detected in the ovaries. Considering the function of hormones in larval metamorphosis, we examined the modulation of gene expression in response to hormones, which showed that HaKr-h1 was significantly induced by both JH analogue (JHA) and 20E. Knockdown of HaKr-h1 in fifth-instar larvae resulted in precocious metamorphosis from larvae to pupae. Moreover, a fluorescence immunoassay coupled with heterologous expression revealed that HaKr-h1 was localized in the nucleus of oocyte membrane. In female adults, depletion of HaKr-h1 severely repressed the transcription of vitellogenin, disrupted oocyte maturation and reduced the number of eggs laid, suggesting that HaKr-h1 is required for vitellogenesis and egg production in H.armigera. The present study provides insight into the roles of HaKr-h1 in JH-mediated reproduction and highlights HaKr-h1 as a target for suppression of lepidopteran pests.

Life History of Cambarus veteranus (Guyandotte River Crayfish); an imperiled West Virginia endemic

Cambarus veteranus Faxon, 1914 (Guyandotte River Crayfish), is an endangered, narrow endemic, residing in just two streams in the southern coalfields of West Virginia. A life history study was initiated for C. veteranus in Clear Fork of the Guyandotte River, Wyoming County, West Virginia to gather basic life history information needed for future conservation efforts. Monthly collections began June 2017 and will continue through June 2018. Two 400-meter stream reaches were designated as life history study sites with two different 100-meter sub-reaches sampled each month. Specimens, regardless of species, were collected, sexed, and molt stage determined. Preliminary results suggest an importance of water temperature on crayfish capture with December yielding considerably higher capture rates of C. veteranus relative to other species collected. Form I males are ever present and reach their highest density in early winter. Pre-glaired females reached their highest densities in October and December with glaired females present nearly every month. Thus far, a single ovigerous female has been found, bearing just two stage 4 juveniles. A molting event occurred between September and October with pre-molting individuals present in September and freshly molted individuals present in October. Providing life history information for C. veteranus will assist in conservation efforts and possible repatriation of C. veteranus in the future. Additionally, life history information for C. veteranus can be compared to closely related species that are often used as surrogates for C. veteranus in captive rearing studies.