Controlled incubation supports baseline developmental and molecular comparability in cuttlefish (Sepia officinalis) embryos

Early life stages are increasingly used as biological sentinels in marine environmental research, yet the ecological valence of controlled systems is still poorly understood. Cephalopod embryos are commonly used to study developmental, physiological, and molecular responses to environmental stressors, but it remains unclear whether embryos incubated under controlled conditions exhibit developmental and molecular patterns comparable to those observed under field conditions. This study aimed to evaluate biometric parameters and gene expression patterns in common cuttlefish (Sepia officinalis) embryos incubated under natural environmental and controlled tank conditions to assess their baseline comparability within the investigated developmental window. Eggs from a single sampling area were collected and randomly divided into two groups: one was maintained in a tank-based incubation system, and the other was returned to the sampling area. Embryos from both groups were sampled 7 (T1) and 14 (T2) days after collection. Embryos’ weight and mantle length were recorded at each sampling time. PCR analysis evaluated the expression of genes associated with neural and visual system development, stress response, and oxygen transport. Results showed a stage- and time-specific difference in embryo weight was detected, whereas the other endpoints showed no consistent tank-specific alterations, providing preliminary support for the evaluation of tank-based incubation systems across different experimental contexts and developmental stages, including beyond hatching. These findings should nevertheless be interpreted cautiously and not as evidence of formal biological equivalence between controlled and field conditions.