Diversity and Distribution of the Order Tetraodontiformes in Spain: New Records, Biological Insights and Ecological Implications

This study documents the presence of two uncommon tetraodontiform fishes and reviews the occurrence of species from this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in the Atlantic waters off the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, while a specimen of Ephippion guttifer was captured in 2025 in the Ría de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of the two species. Histological reproductive analysis of the Ephippion guttifer specimen revealed a female in the spawning-capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. An updated comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations was compiled. Historically, a total of 26 species across five families have been reported in Spanish waters, with 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is included, providing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment.