In the fruit fly, Drosophila melanogaster, a relatively uncharacterized developmental timepoint termed the mid-third instar transition (MIT) occurs during the third and final larval stage. While there are no obvious morphological changes that occur during the MIT, widespread changes in gene expression are thought to prepare the organism to enter metamorphosis. How these massive changes in gene expression are regulated and how they alter larval behaviour and physiology are unclear. Here, we examine tissue and developmental stage-specific transcriptome data generated as part of the ModEnCODE project to better understand how changes in gene expression at the MIT alter physiology in preparation for metamorphosis. Analysis of enriched binding motifs suggests that regulation of MIT genes is complex but is likely mediated, at least in part, by ecdysone. Our results also suggest that gene expression changes at the MIT likely prepare the larva for metamorphosis in numerous ways, including altering metabolism to help meet energetic demands, increasing glue protein production allowing pupae to adhere to surfaces and preparing the immune system to control the spread of microbes during histolysis of larval tissues. At the same time, changes in imaginal tissues support the proliferation and differentiation of cells characteristic of the metamorphic moult.
Studying the morphology of the male reproductive system is crucial for understanding the reproductive biology of insects, particularly pest species. This study aimed to characterize the male reproductive system of the strawberry beetle pest Coraebus elatus (Fabricius, 1787) using light and scanning electron microscopies. The results revealed that each testis contains six testis follicles, each displaying distinct stages of differentiation of germ cells. Fully developed sperm pass through the vas deferentia, lined with a single-layer cuboidal epithelium and a muscle layer. While the wall of the tubular accessory glands is lined with a single-layered cuboidal epithelium, the wall of the bean-shaped spermatophoral glands is surrounded by a pseudostratified columnar epithelium. These glands open into the ejaculatory duct which is surrounded by a single-layer cylindrical epithelium and a muscle layer. This study provides valuable data that will serve as a foundation for future research on the morphology and systematic.
Omphisa fuscidentalis is a univoltine moth whose larvae undergo an unusually prolonged diapause (similar to 9 months) inside bamboo internodes - a unique life-history trait that may shape its reproductive biology. Despite its ecological and economic importance as an edible insect, little is known about its reproductive system. This study presents the first detailed analysis of testis development and sperm ultrastructure across larval, prepupal, and adult stages using light, scanning electron, and transmission electron microscopy. We describe a novel transformation from paired testes with four follicles in larvae to a fused single testis with eight follicles in the prepupal stage. Furthermore, we document sperm dimorphism in detail, highlighting structural specializations in both eupyrene and apyrene spermatozoa. Noteworthy features include micronuclei formation during apyrene spermiogenesis, a dense cap in mature apyrene sperm, a shoe-sole-shaped mitochondrial derivative, and a developmental shift in eupyrene flagella from a hand-like to a sunshine-like configuration. These ultrastructural changes likely reflect adaptive strategies associated with diapause. By integrating multi-scale imaging, this work offers new insights into the reproductive development of O. fuscidentalis and provides a valuable reference for future comparative studies on sperm evolution and reproductive adaptations in insects with complex life cycles.
The breeding of Chinese mitten crabs (Eriocheir sinensis) commonly relies on large-sized broodstock; however, the genetic advantages and potential risks of this practice remain insufficiently evaluated. To investigate possible molecular deficiencies associated with large-sized parents, we conducted a comprehensive transcriptomic analysis during the breeding phase, focusing on offspring at key developmental stages (fertilized eggs and megalopae) and reproductive tissues of parents of different sizes (testes and accessory glands in males, ovaries in females). Our results revealed significant downregulation of pathways related to chitin synthesis and moulting cycles in offspring derived from large broodstock, with key genes including CDA1, Mco1, and FIBCD1. In addition, genes involved in sensory perception and neural development, such as CHST11, Celsr3, and EphA5, were consistently downregulated in the reproductive tissues of large-sized parents. In male accessory glands, large broodstock further exhibited reduced expression of genes associated with chromosome stability, including Hhex and PAX5. Enzyme activity assays (chitinase, carbonic anhydrase, acetylcholinesterase, and peroxidase) corroborated the transcriptomic patterns. Overall, our findings suggest that large-sized broodstock may carry latent genetic deficiencies affecting moulting, growth, neural function, and reproductive performance. This study provides a theoretical foundation for optimizing broodstock selection and advancing genetic breeding strategies in E. sinensis.
This study offers novel insights into oocyte development, ovarian maturation, size at sexual maturity, and the spawning season of the deep-water penaeid shrimp, Metapenaeopsis kyushuensis, collected from deep-water Kagoshima Bay, southern Japan. Additionally, through histological observation, we determined the most efficacious ovarian maturity indicator for this species among the gonadosomatic index, oocyte diameter, and the ovary-to-body width ratio. Histological analysis enabled us to categorize oocyte development in M. kyushuensis into seven stages and confirmed the absence of cortical crypts. We defined females as mature when their oocytes displayed signs of germinal vesicle breakdown or a migrating nucleus. The ratio of ovary-to-body width was identified as the most efficient index for evaluating maturity status. The minimum carapace length (CL) of the histologically confirmed mature females was 11.5 mm, whereas the CL at which 50% of females attained maturity was 13.7 mm. M. kyushuensis is a multiple spawner, with spawning occurring from April to January, peaking between June and September. The prolonged spawning season of M. kyushuensis was presumably influenced by deep-water environments and comparatively higher water temperatures year-round.
This study investigates male pedipalp chela dimorphism and its association with reproductive behaviour in the litter-dwelling scorpion, Tityus pusillus. Using geometric morphometrics, two distinct male morphotypes were identified based on pedipalp chela shape: robust and gracile. These morphotypes were associated with measurable variation in courtship behaviour aspects. Males with robust chelae performed a higher number of reproductive attempts and female manipulations than gracile-chela males, although these differences were not statistically significant. Notably, robust-chela males completed courtship significantly faster than gracile-chelae males (8.03 +/- 5.14 minutes vs. 18.40 +/- 13.84 minutes), measured as the time until mating successful conclusion. Both morphotypes exhibited similar reproductive success rates (37% and 31%, respectively). These results indicate that robust and gracile differ in courtship dynamics, particularly in courtship duration and patterns of female handling. Variation in female resistance during courtship may help explain why male reproductive behaviours vary. This study documents male chela dimorphism in T. pusillus and reports its correlation with variation in courtship behaviour.
The present study focused on characterising the sperm motility pattern in Mytilus galloprovincialis, among the most economically and ecologically important bivalve molluscs in European coastal areas, as a key step in developing sperm management protocols. To this aim, computer-assessed sperm motility parameters were evaluated as a function of time after activation and post-collection storage. In addition, the effect of combined low osmolality and pH on sperm motility was evaluated for the formulation of diluents capable of inhibiting sperm motility. Sperm motility parameters remained completely unchanged up to 60-80 min after activation, also when semen was activated after 6 h of cold incubation. All hypoosmotic solutions tested (100 to 600 mOsm) inhibited sperm motility, which could only be restored in the 600-mOsm inhibited samples, irrespective of the pH of the diluent. The ease of handling and long-lasting motility properties demonstrated by M. galloprovincialis spermatozoa may facilitate the application of technologies used in both hatcheries and laboratory research. In addition, the simply formulated diluent DI600 (2% NaCl, pH 7.7) can be considered a promising medium for the formulation of cryoprotective extenders or diluents for post-collection semen management.
Caenorhabditis (Nematoda) is a cosmopolitan genus, but little is known about the biology and ecology of many of its species. This study aims to describe the life cycle of Caenorhabditis tropicalis and discuss the implications of its life cycle in future experimental studies. The wild-type JU1428 strain of C. tropicalis was provided by the Caenorhabditis Genetics Center. The experiments were carried out at 25 degrees C in Nematoda growth medium seeded with the bacterium Escherichia coli (OP50 strain). Under these conditions, the egg hatching time was 11.3 h +/- 0.5, and the hatching rate was 70%. The body length of the individuals increased linearly until the first egg-laying. Caenorhabditis tropicalis underwent four moults and the first egg was laid by the hermaphrodites 48 h +/- 1 after the hatching of the initial eggs. The life cycle is short and quite similar to that of C. elegans. The easy cultivation, ability to self-fertilize, occupation of little space in the laboratory, short life cycle and easy acquisition from the Caenorhabditis Genetics Center or by isolating from the natural environment makes C. tropicalis a species of high potential as a model organism in experimental studies.
Anthropogenic activities are accelerating species dispersal, increasing the risk of biological invasions. The clinging jellyfish Gonionemus vertens, native to the North Pacific, has expanded into temperate coastal waters worldwide. This study documents its complex asexual life cycle and reports novel observations of binary fission and budding, in addition to frustule production. Regression analyses revealed significant relationships among life-history traits, including rapid polyp maturation, frustule bud production and subsequent polyp development. These findings indicate clonal growth occurs at a predictable rate under laboratory settings, with polyp densities exceeding 24,000 m-2. Such reproductive capacity may explain the large seasonal medusae populations, though few polyps have been detected in the field. These results highlight the need for further investigation into the ecology and life history of G. vertens populations to better understand their invasive potential.
Helicoverpa armigera (H & uuml;bner) is a major lepidopteran pest of chickpea, with its development and reproduction strongly influenced by temperature. This study examined the development, survival and reproduction of H. armigera reared on chickpea under constant temperatures ranging from 14 degrees C to 36 degrees C. Life table parameters were estimated along with linear and six non-linear thermal models to identify critical thresholds and heat requirements. Results showed that fecundity peaked at 27 degrees C (532 eggs/female) and declined at higher temperatures, while the intrinsic rate of increase (rm) was highest at 30 degrees C. Linear regression analysis estimated the lower temperature threshold (Tmin) for egg development at 7.71 degrees C, while Tmin for larval instars ranged from 4.19 degrees C to 10.52 degrees C. Embryonic development required 74.07 degree-days. Among the six non-linear temperature development models tested, the Lactin-2 model yielded the most biologically realistic estimates of Tmin, optimal temperature (Topt), and upper threshold (Tmax), and showed the best goodness-of-fit based on AIC and related statistics. These results provide reliable temperature-based developmental and phenological models for H. armigera on chickpea, supporting better prediction of pest population dynamics and more precise timing of integrated pest management under variable climatic conditions.
This study examined the sex ratio, size at gonadal maturity, breeding season and fecundity in crab, Leptodius exaratus, from an intertidal population along the Karachi coast. From January to December 2022, we collected specimens monthly from the Buleji rocky shore. We analysed 753 specimens, including 384 males and 369 females. The male-to-female ratio was 1:0.96. Fifty per cent of males and females reach gonadal maturity at 20.5 mm and 18.5 mm carapace width (CW), respectively. The smallest ovigerous crab had a CW of 16 mm. Female crabs were found to breed throughout the year, with a major peak in April when 60% of females were egg-bearing. The number of eggs per brood varied from 837 to 10,770. This study also compares the results with those of previous research on L. exaratus, highlighting differences in sex ratios and breeding seasons. Additionally, it examines the size at which 50% population attains gonadal maturity, which has not been previously reported in the literature, thereby deepening our understanding of this species' reproductive biology. These findings are vital for managing and conserving L. exaratus, as they enhance our understanding of its biology and help develop more effective conservation strategies.
The reproductive biology of Parapenaeus lanceolatus Kubo, 1949 (Crustacea, Decapoda, Penaeidae), was examined for the first time, focusing on oocyte development, ovarian maturation, size at sexual maturity, and spawning season using specimens collected from Kagoshima Bay in southern Japan. Histological analysis enabled the classification of oocyte development in P. lanceolatus into six distinct stages and confirmed the presence of cortical granules. Females were classified as mature when their oocytes exhibited cortical granules in the peripheral region or showed signs of germinal vesicle breakdown. The gonadosomatic index (GSI) was identified as a suitable metric for assessing maturity status in P. lanceolatus, with females having a GSI of >= 4% classified as mature. The minimum carapace length (CL) for histologically confirmed mature females was 21.6 mm, while the size at sexual maturity for P. lanceolatus was determined to be 22 mm CL. P. lanceolatus is a multiple spawning species, with the spawning season spanning from July to April. The primary peak in spawning activity occurs from September to October, accompanied by a shorter and less pronounced peak in April. Older individuals tend to spawn earlier in the spawning season, whereas first-time spawners typically spawn later in the season.
The deep-sea coral Desmophyllum pertusum is an important reef builder with high associated biodiversity. Oocyte sizes were investigated using samples from November and December in each of 2011, 2013, 2022 and 2023 from the Tisler Reef in Norway using histological methodology. Both previtellogenic and vitellogenic cohorts of oocytes coexisted within polyps, with the previtellogenic cohort of oocytes observed as early as late-November and a vitellogenic oocyte growth rate of similar to 1 mu m a day. This suggests a 14-16-month gametogenic cycle, longer than observed in other locations. Vitellogenesis of oocytes is predicted to coincide with the spring bloom in this region. The results of this study provide further understanding of the reproduction of Desmophyllum pertusum, specifically at the Tisler Reef.
Photoperiod plays a critical role in regulating growth and reproduction in aquatic species, yet its influence on juvenile giant freshwater prawn (Macrobrachium rosenbergii) is not well understood. A 56-day trial was conducted under three light regimes (0 L:24D, 12 L:12D and 24 L:0D) to assess survival, growth, and the expression of germ cell-related genes. Continuous light initially enhanced growth and survival but led to significant declines after day 28. Complete darkness reduced early survival but induced compensatory growth later. Balanced light-dark cycles (12 L:12D) maintained stable growth and survival and produced the highest vasa expression, suggesting improved support for reproductive development. Photoperiod also differentially regulated other genes: Fem-1C was strongly induced under continuous light, while RAD51 was suppressed. These findings highlight stage-specific photoperiod responses in juveniles, distinct from larval requirements, and demonstrate that moderate light-dark cycles are optimal for growth and germline gene regulation. This study provides a basis for photoperiod management strategies in prawn aquaculture.
Size at sexual maturity is a key population parameter, particularly in commercially important species. The traditional estimation methods require identifying mature individuals by physiological and/or morphometric sexual characters. In this study, we propose using linear regression model based on the relationship between the size at sexual maturity and maximum sizes of shrimps, lobsters, and crabs, as an alternative when traditional methods cannot be applied. Data of size at sexual maturity and maximum size were obtained from the scientific literature and ln-transformed. A total of 275 papers were reviewed covering 64 shrimp, 20 lobster, and 88 crab species. Linear regression analysis revealed a close to 1 positive slope and negative intercept values, with determination coefficient generally exceeding 0.80. Differences between reported values and our estimates were typically within 20%, though larger deviations occurred when maturity ratios fell outside 0.45-0.75 range. The proposed linear regression parameters offer a reliable alternative for estimating sexual maturity size when traditional methods are not feasible.
Temperature controls the timing of life-cycle events in marine animals, including the spawning and breeding periods. Environmental conditions change with latitude, impacting the fitness of populations across species' geographic range. This provides an opportunity to test the impacts of global climate changes through interactions with the breeding cycles of marine animals. Cingula trifasciata (J. Adams, 1800) is a very common rissoid gastropod in sheltered places in the lower half of the intertidal rocky shores, in the Northeast Atlantic and Mediterranean areas, including the Azores and Madeira archipelagos. Aiming to compare possible differences in the spawning period between the Azores and other regions related to sea-surface temperature, we studied the reproductive cycle of C. trifasciata in this archipelago over a one-year period. Our data show that the minimum size for reproduction is about 3 mm in shell length. Although this species has a preferred breeding season that extends from December to June, possibly July, and a spawning season from June to August, it seems to be able to reproduce throughout the year in the Azores Archipelago. This ability enhances the resilience of this species to global climate changes as it provides key ecological advantages and reproductive pre-adaptations to face glacial periods.
In situ spawning observations are important in understanding the reproductive ecology of marine organisms. Here, we report an opportunistic observation of the male spawning of the sea cucumber Pearsonothuria graeffei (Semper, 1868) on the coral reefs in southern Philippines. In situ sperm release was observed at 13:00 h (n = 1) and at 16:30-17:00 h (n = 3), 3 and 11 days after the full moon of May 2025, at two separate locations. These observations provide insights into the reproductive timing of the commercially and ecologically important sea cucumber species from the Philippines.
This study documented a spontaneous out-of-season spawning event of the purple sea urchin Heliocidaris crassispina in an indoor aquaculture laboratory maintained at 24.6 degrees C with a 12:12 light-dark cycle. On the afternoon of 8 January 2024, 3 days prior to the new moon, three female and four male sea urchins spontaneously spawned for 1.5 hours. This spawning event occurred 2 months earlier than the known spawning period of H. crassispina in Hong Kong. The eggs were successfully fertilised confirming gamete fertility. These findings provided additional insights into the timing and reproductive plasticity of H. crassispina in controlled environments, highlighting the potential of such indoor systems for broodstock conditioning and gamete production in sea urchin aquaculture. [GRAPHICS]
