Hydrogamasus littoralis (Canestrini & Canestrini, 1881)

Synonym: Gamasus littoralis Canestrini & Canestrini, 1881 (original designation)

Type material: Holotype: One specimen deposited at Instituto Sperimentale per la Zoologia Agraria (Castilho et al. 2016; GBIF 2022).

Type locality: Italy: Lido de Venezia (Canestrini & Canestrini 1881; Castilho et al. 2016; GBIF 2022).

Geographical distribution: Western Europe (GBIF 2022).

Distribution in Portugal: North: Leça da Palmeira, Cabo do Mundo, Vila Praia da Âncora, and Moledo beaches (Costa-Garcia 2018).

Ecological notes: Marine, intertidal, barnacle epibiont (Costa-Garcia 2018; Halbert 1920).

Remarks: This species is considered marine, however, its status as truly aquatic should be furtherly checked that it is an active species in all its life stages in water, as well as its breeding.