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Email the author (Login required) Lymphoid organ system development and early window of immunological susceptibility in spotted rose snapper Lutjanus guttatus
Submited: 2025-10-01 10:56:49 | Published: 2026-04-30 21:53:19
DOI: https://doi.org/10.3856/vol54-issue2-fulltext-3545
Abstract
The lack of a lymphoid organ system in Lutjanus guttatus larvae may limit survival, the use of immunostimulants, and the implementation of vaccination during early juvenile stages. Identifying the timing of autologous immunoglobulin M (IgM) activity in lymphoid organs could improve progeny survival. Therefore, to examine maternal IgM depletion and the first IgM autologous production, samples were collected at multiple time points during the larval and early juvenile stages of L. guttatus development. The lymphoid organs (e.g. head kidney, spleen, gut-associated lymphoid tissue, and thymus) were described by histomorphology and immunohistochemistry, and we also analyzed the gene expression of immune-related markers. The primitive head kidney was evident at 2 days post-hatching (dph), the spleen and thymus appeared at 3 and 9 dph, respectively. Protection by IgM-dependent maternal transfer was depleted at 2 dph (1.8 mm total length, TL). The first IgM autologous production was detected in juveniles at 35 dph (15 mm TL), and an increase in immune-related gene expression was observed at 15 dph (~5.35 mm TL). This increased gene expression was associated with antigen-specific immune responses, such as helper T cell activity. L. guttatus presents an early window of immunological susceptibility (EWIS) during the larval period. Our data show how this window is covered by the innate response from 2 to 35 dph (1.8 to 15 mm TL). These findings represent essential knowledge for early immunostimulant or vaccination programs in L. guttatus culture schemes. Our results suggest that 35 dph (15 mm TL) may be the initial larval age-size for initiating vaccination programs at both experimental and commercial scales.
