D-galactose, a common component of staple foods, induces oxidative stress and inflammageing when taken in excess, making it a widely used model for ageing studies. However, its dose-dependent effects on early life development remain poorly characterized, particularly whether low-dose beneficial effects exist at early adulthood following drug withdrawal. This study assessed the dose-dependent impact of D-galactose on life history traits, behaviour, and redox homeostasis in D. melanogaster, determining whether developmental exposure (confined to pre-eclosion) produces alterations in early adulthood. Eggs were exposed throughout development to distilled water (control) or D-galactose (10, 20, or 25 mg/g). Treatment ended at eclosion; adults were maintained on untreated food. Larval behaviour, pupation, eclosion, and adult locomotor performance (day five) were assessed. Biochemical analyses (thiols, H₂O₂, nitric oxide, MAO-B activity) were conducted on five-day-old adults. The 10 mg/g dose significantly improved pupation (p < 0.001), eclosion (p < 0.05), larval feeding (p < 0.05), and crawling (p = 0.01). In five-day-old adults, this low dose decreased H₂O₂ (p < 0.001) and increased total and non-protein thiols (p < 0.001), indicating redox modulation despite drug withdrawal. The 25 mg/g dose impaired pupation, elevated H₂O₂ and nitrite/nitrate (p < 0.001), and reduced thiols. Adult climbing activity was unaffected across all groups (p > 0.05), revealing dissociation between redox changes and behavioural outcomes. D-galactose exerts dose-dependent biphasic effects. The low dose was associated with beneficial developmental effects and redox changes consistent with a hormetic response, while higher doses induced oxidative/nitrosative stress and impairment. The absence of corresponding enhancement in adult behaviour despite altered redox status highlights a biochemical-functional dissociation following developmental exposure.
The objective of this study was to histologically record the ontogenetic changes in the stomach and hepatopancreas of two sesarmid species, Episesarma singaporense and E. versicolor, studied from the zoeal stage 1 to the crab stage. Specimens of ovigerous females were collected from a hatchery site and all stages (zoea 1 to crab) were processed using the morphology and histological method through semithin section. The results of histological analysis of the digestive system were largely organized within the body and showed a complex organization. The distinction between cardiac and pyloric stomachs in both species was unclear in the zoeal 1 and 2 stages but became evident in zoeal stages 3 and 4. All stomach structures in the megalopa and crab stages, especially the well-developed lateral teeth in the cardiac stomach, were clearer than they were in the zoeal stages. The same development was observed in the hepatopancreas that was fully developed by the zoeal 3 stage and became more intricately branched and larger in later stages. This development is an indicator of larval and later feeding activity, which provides information for aquaculture of two sesarmid species.
A central question in developmental biology is how organs acquire their final shape. Since a conserved organ might form through distinct steps, even within animals belonging to the same class, comparative studies are needed to reveal conserved or unique principles. Sea stars are a useful system to investigate how organs develop their specific structure across various species. This species-rich and diverse class of animals provide embryos that can be easily cultured in large numbers and are optically clear, which allows morphogenesis to be observed live. All sea star larvae develop a coelom: a hollow tube that fills the body cavity. We recently named it the “hydro-vascular organ” (HVO), as most of this organ will form the adult water-vascular system after metamorphosis. Understanding the distinct steps that drive HVO development across species requires comparative studies, but detailed characterizations of embryonic and larval stages have been reported for only a few representatives of asteroidea. Here we use brightfield microscopy and live imaging to document for the first time the development of Asterias forbesi, an ecologically important species that lacks a detailed description of embryonic and larval stages. Leveraging the optical clarity of these larvae, we defined distinct stages of HVO morphogenesis. To understand whether the same organ forms through shared steps across different species, we compare A. forbesi HVO development with sea stars from two other orders, Patiria minata and Astropecten aranciacus.
In spiralians, the relationship between early cleavage patterns and the establishment of the juvenile body plan remains one of the central questions. In the oligochaete Tubifex tubifex, the micromeres other than 2d and 4d are bilaterally symmetrically arranged in an arc-shaped assemblage that surrounds the anterior side of the large 2d micromere. The bilateral configuration of the micromeres in Tubifex is distinct from the radially symmetric micromere arrangement in other spiralians. To address the possibility that the bilaterally symmetric arrangement of the micromeres contributes to establishing bilateral symmetry in Tubifex embryos, we mapped micromere fate using DiI as a lineage tracer. The developmental fates of all the micromeres except 2b, 2d, 3b, and 4d were examined. The results showed that the micromeres in T. tubifex embryos lineage-specifically contribute to the head epidermis, cerebral ganglion, buccal cavity, pharynx, oesophagus, and yolk sac ectoderm, comprising the dorsal temporary epithelium and ventral/ventrolateral epidermis, of the juvenile. The micromeres, except for 1c, 1d, and 2c, contributed to a single structure (tissue or organ) of the juvenile. T. tubifex shares most of these micromere-specific structures with other annelids, such as Helobdella, Capitella, and Platynereis. There are two exceptions. One is the temporary epithelium derived from 1c and 1d, which is clitellate-specific; the other is the ventral epidermis derived from 3c and 3d, which is species-specific. The present results showed that the micromeres located to the left of the midline at the 22-cell stage generate the left side of the embryo in terms of tissues and organs, and those located to the right of the midline give rise to the right side of the embryo based on the position of individual micromeres relative to the (future) midline. The pattern of micromere contribution to the left and right sides of the Tubifex embryo is almost identical to that in other spiralians. These results imply that in T. tubifex, the bilateral juvenile body plan is set up by the early cleavage pattern.
The homeobox gene engrailed is a multifunctional regulator with diverse developmental roles across Bilateria, ranging from epithelial boundary formation and neural regionalization to lineage-specific innovations such as arthropod segmentation and molluscan shell-field patterning. Despite this broad functional repertoire, its deployment within Gnathifera has remained largely unknown. Here, I characterize the genomic architecture, protein structure, orthology, and embryonic expression of the single engrailed gene in the monogonont rotifer Brachionus manjavacas. Phylogenetic analyses recover the sequence within the protostome engrailed clade, confirming its orthology. The gene retains the full canonical bilaterian motif complement, including EH1, EH2, the homeodomain (EH4), and the C-terminal EH5 region, and exhibits an intron within EH2 whose position and phase are invariant across protostomes and deuterostomes, indicating deep evolutionary conservation despite extreme variation in intron length among taxa. Embryonic in situ hybridization and immunofluorescence staining reveal a distinctly noncanonical expression pattern. Instead of segmental or ectodermal boundary stripes, engrailed is localized to the protonephridial terminal organs, canal cells, and Huxley’s anastomose (a characteristic interconnection within the protonephridial canal system), and appears transiently in two neurons of the developing foot. These domains display epithelial, ciliary, and neural characteristics, consistent with multifunctional cell identities typical of rotifers. Comparative analysis across Metazoa shows that engrailed expression broadly converges on epithelial and neural boundary contexts, suggesting that such local boundary-type functions may represent the ancestral deployment of the gene. Together, these findings broaden the known developmental repertoire of engrailed and highlight the value of rotifers for comparative studies of bilaterian gene function.
