# Tissue-Specific Gene Expression of Digestive Tract Glands in Paroctopus digueti: Insights for Cephalopod Biology and Aquaculture

## TL;DR

This study explores the gene activity in the digestive glands of the Pacific pygmy octopus to understand its feeding and digestion processes, supporting its potential as a model species for research and aquaculture.

## Contribution

The study provides the first transcriptomic comparison of digestive tract glands in Paroctopus digueti, revealing their specialized functions.

## Key findings

- Anterior salivary glands are involved in neuroendocrine regulation through neuropeptide expression.
- Posterior salivary glands express proteases and toxins, supporting their role in extracellular digestion and venom production.
- Digestive glands show specialization in catabolism and immune defense via antimicrobial peptides.

## Abstract

Pacific pygmy octopus Paroctopus digueti is a small species that could become an important model for octopus biology and aquaculture. To better understand how it captures and digests food, we studied three main organs that synthesize and secrete digestive enzymes and functional molecules in the feeding process: the anterior and posterior salivary glands and the digestive gland. We discovered clear differences in their functions by analyzing the genes active in each tissue. In the anterior salivary glands, gene expression was associated with signaling pathways that could regulate feeding processes. Gene expression in the posterior salivary glands was associated with the release of digestive enzymes and toxins that may help paralyze prey. This means they participate in the first digestion and act as a venom gland. Gene expression in the digestive gland suggests specialization in breaking down the food into molecules, producing energy reserves, and protecting the animal with antimicrobial molecules. These findings show that each gland has a unique role, helping us to understand how octopuses feed and defend themselves from pathogens. Furthermore, these results support P. digueti as a valuable species for future research and aquaculture development.

Pacific pygmy octopus Paroctopus digueti is a promising model for cephalopod research and aquaculture; its feeding and nutritional biology remain poorly understood. The anterior salivary glands (ASG), posterior salivary glands (PSG), and digestive gland (DG) are central to these processes, but molecular comparisons are lacking. To address this gap, we performed a transcriptomic study to explore the enzymatic repertoire and functional specialization of these tissues. Total RNA was extracted from ASG, PSG, and DG of three pre-adult individuals collected in La Paz Bay, Mexico. RNA-Seq libraries were sequenced, and a non-redundant multi-tissue transcriptome was assembled. The ASG displayed high expression of neuropeptides, playing a role in neuroendocrine regulation. The PSG showed elevated protease expression, supporting its function in extracellular digestion, alongside toxins that reinforce its role as a venom gland. The DG was enriched in proteins linked to biomolecule catabolism and antimicrobial peptides, alluding to metabolic specialization and immune defense. These results were validated by qPCR, and target genes were also amplified in Octopus maya and O. hubbsorum, showing some similarities in expression patterns. Overall, our findings suggest strong glandular specialization in P. digueti, providing insights into cephalopod digestive physiology and supporting its value as a model species.