Achelous

Distinguished from other portunid genera by combination of hexagonal carapace with nine anterolateral teeth, four-lobed frontal margin, and natatory fifth pereiopod. Separation from closely related genus Portunus requires examination of carapace dentition and male gonopod morphology. A. hastatus specifically identified by markedly elongate ninth anterolateral tooth.

Swimming crabs with broadly hexagonal carapace bearing nine anterolateral teeth, with the ninth tooth markedly elongate in some species. Frontal margin four-lobed. Chelipeds robust with slender fingers. Fifth pereiopod modified as natatory paddle, characteristic of Portunidae. Carapace surface typically granulated or spiny; A. spinimanus exhibits spiny chelipeds as indicated by its specific epithet.

Marine coastal environments, primarily bays and continental shelf waters. Sediment type influences distribution patterns, with species showing preferences for particular substrate compositions. Depth ranges vary by species; A. spinimanus most abundant at 15-20m depths in southeastern Brazil, while A. hastatus recorded at 6m depth off Tenerife. Associated with varying water masses including Coastal Water, Tropical Water, and South Atlantic Central Water.

Widespread in Atlantic Ocean and adjacent seas. A. hastatus with Atlantic-Mediterranean distribution, Spain and Canary Islands representing primary strongholds. A. spinimanus restricted to southeastern Brazil. A. affinis distributed in Eastern Tropical Pacific. Genus shows broad biogeographic range across tropical and subtropical waters.

Activity patterns influenced by seasonal water mass intrusions; South Atlantic Central Water (SACW) seasonal intrusion affects spatiotemporal distribution in southeastern Brazil populations.

Scavenging and predatory feeding observed; A. hastatus documented scavenging on vertebrate remains in nocturnal foraging aggregations.

Complex life cycle with planktonic larval stages typical of decapod crustaceans, followed by benthic juvenile and adult phases. Age and sexual segregation documented in A. spinimanus, with different habitat use patterns between juveniles and adults. Maturity stages show differential distribution patterns.

Nocturnal foraging activity documented in A. hastatus. Gregarious feeding behavior observed, with multi-individual aggregations at food sources. Swimming capability via natatory fifth pereiopods allows active movement through water column. Some species show stenotopic habitat preferences.

Predator and scavenger in benthic marine food webs. Fishery resource subject to harvesting pressure; abundance patterns potentially influenced by fishing exclusion in protected areas. Role in nutrient cycling through scavenging activity.

Commercial fishery resource, particularly A. spinimanus in Brazil. Potential for competitive interactions with other harvested portunids such as Callinectes danae. No documented medical significance for genus, distinct from unrelated venomous moth genus Lonomia (which includes species L. achelous, named after the mythological figure, not this crab genus).

• PortunusClosely related genus within Portunidae; separation requires detailed examination of carapace dentition and male gonopod structure
• CallinectesSympatric portunid genus with overlapping distribution and ecological niche; potential competitive interactions suggested but unconfirmed

Genus name Achelous derives from Greek mythology (river deity), causing potential confusion with unrelated biological entities named after the same mythological figure, such as the moth species Lonomia achelous. No taxonomic or biological relationship exists between the crab genus Achelous and these other namesakes.

• Portunidae
• swimming crab
• marine
• Decapoda
• Brachyura
• fishery resource
• benthic
• nocturnal forager

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Up Close and Personal With Venomous Moths
• Ovid Underwater: Environmental Dialectics at Achelous’ Banquet
• Peer Review #3 of "Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil (v0.1)"
• Peer Review #1 of "Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil (v0.1)"
• Peer Review #2 of "Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil (v0.1)"
• On the Distribution of Portunus (Achelous) Affinis and Euphylax Dovii (Decapoda Brachyura, Portunidae) in the Eastern Tropical Pacific 1)
• Peer Review #2 of "Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil (v0.2)"
• Morphological and ecological notes on the swimming crab Achelous hastatus (Linnaeus, 1767) (Family: Portunidae ), from Tenerife, Canary Islands (NE Atlantic)
• Peer Review #3 of "Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil (v0.2)"