Taxonomy & naming
Economidichthys mornosensis was described in 2026 by Jörg Freyhof, Matthias Geiger and Stamatis Zogaris in Zootaxa, as the newest species in the small genus Economidichthys, family Oxudercidae, subfamily Gobionellinae. Before this description the genus held two species, both narrow-range Greek endemics: Economidichthys pygmaeus and Economidichthys trichonis. The genus name honours Panos S. Economidis, the Greek ichthyologist whose foundational systematic work on Greek freshwater gobies (much of it with P.J. Miller, cited repeatedly in the description's own reference list) established the modern understanding of this fauna; the name combines his surname with the Greek ichthys ('fish'). The species epithet mornosensis attaches the Latin place-suffix -ensis to Mornos, the river whose delta and associated karst springs define the species' known range — 'of the Mornos.'
Molecular data comparing Economidichthys mornosensis against Economidichthys pygmaeus recovered a minimum uncorrected K2P genetic distance of 5.7% in the mitochondrial COI barcode region — a substantial split for two morphologically similar, geographically separate goby species, and part of what supports its recognition as distinct rather than as a population of E. pygmaeus.
Morphology
No standard length or full morphometric account was captured in the abstract-level source material available for this article; the complete description sits behind a journal subscription. The diagnosis rests on a combination of characters distinguishing it from its closest relative, E. pygmaeus: males of E. mornosensis carry a large black blotch on the first dorsal fin, the perianal organ is shorter, and the back is scaleless along the complete base of the second dorsal fin. The perianal organ itself is the hallmark anatomical feature of the genus Economidichthys as a whole — a distinctive dermal gland structure situated near the anus, first documented in the genus in 1987 and unique among European gobies to this small group of Greek endemics.
Habitat
The type locality is Chiliadou spring, about 1 mi west of the village of Monastiraki, within the Mornos River delta area of southwestern Greece. The Catalog of Fishes records the species' broader distribution as springs and spring-fed streams of the Mornos drainage. The original description's own keywords identify the species explicitly as a narrow-range endemic of Mediterranean wetlands — the cold, clear karst springs typical of the limestone geology of mainland Greece around the Gulf of Corinth, the same general habitat type documented for its relatives E. pygmaeus and E. trichonis elsewhere in western Greece.
Feeding
No dietary information has been documented for this species. Related gobies in the genus Economidichthys and the wider family Oxudercidae are generally benthic micropredators taking small invertebrates from spring and stream substrates; this is offered here only as a genus-level generality, not a confirmed observation for E. mornosensis.
Mating
No courtship or spawning behaviour has been documented for this species.
Breeding
No breeding record exists for this species, in the wild or in captivity. Small gobies of this general type typically spawn adhesive eggs in a sheltered cave or crevice site, with the male guarding the clutch until hatching; this is stated here only as a widespread gobiid pattern, not a confirmed observation for E. mornosensis.
In the aquarium
Economidichthys mornosensis has no aquarium trade history and there is no evidence it has entered the hobby; it was described in 2026 from a tiny, karst-spring-restricted range with no history in commerce. Given the describing authors' own assessment that it is a very narrow endemic potentially facing Critically Endangered status, and given the well-documented vulnerability of small Greek endemic gobies to habitat degradation and the introduction of non-native fishes, this is a species that should stay in the wild and be left to specialists and conservation researchers rather than collected for the trade.
Conservation
Economidichthys mornosensis has not been assessed on the IUCN Red List and is recorded here as Not Evaluated, being too recently described for formal review. The describing authors state directly in their abstract that the species is endemic to a very small area and is potentially Critically Endangered — a self-assessment worth taking seriously pending a formal Red List review. Its restriction to a single small karst spring system in the Mornos River delta leaves it inherently exposed to any disruption of local spring hydrology, from groundwater extraction to pollution or habitat modification around the type locality.