Homoeogammarus, SCHELLENBERG, 1937

Hou, Zhonge & Sket, Boris, 2016, A review of Gammaridae (Crustacea: Amphipoda): the family extent, its evolutionary history, and taxonomic redefinition of genera, Zoological Journal of the Linnean Society 176 (2), pp. 323-348 : 333-334

GENUS HOMOEOGAMMARUS SCHELLENBERG, 1937 B

Exceptions in morphology

There are a few details that hamper a clear picture of Homoeogammarus . Morphologically, five supposed member species are without (or nearly so) long setae on uropod III. In Homoeogammarus tibaldii ( Pinkster & Stock, 1970) , antenna II setae are ‘sometimes curled’ ( Pinkster, 1993), on article 4 densely set. In ‘ Laurogammarus ’ scutarensis (Schäferna, 1922) , the excretory cone is elongated. In ‘ Neogammarus ’ species, uropods I and II are slightly reduced and without lateral spines.

Type species

Gammarus simoni Chevreux, 1894 , described from Tunisia and Algeria.

Additional species

Molecularly (conditionally) proven ( Hou et al., 2014, as Mediterranean Echinogammarus and Dinaric Echinogammarus ) taxa are: (Mediterranean) Carinogammarus thoni Schäferna, 1922 , Gammarus pungens H. Milne Edwards, 1840 , Gammarus veneris Heller, 1865 , Ostiogammarus stammeri S. Karaman, 1931 , Carinogammarus scutarensis Schäferna, 1922 , Echinogammarus cyrtus Pinkster and Platvoet, 1986 , Echinogammarus platvoeti Pinkster, 1993 , Gammarus foxi Schellenberg, 1928 , Echinogammarus monomerus Stock, 1977 , Echinogammarus tibaldii Pinkster and Stock, 1970 , Neogammarus nudus Stock, 1971 ; (Dinaric) Gammarus cari S. Karaman, 1931 , Gammarus acarinatus S. Karaman, 1931 , and Ostiogammarus bosnensis S. Karaman, 1934 . The majority of the Echinogammarus pungens group, sensu Stock, 1968 , are probable members.

Distribution

Homoeogammarus spp. mainly inhabit fresh and brackish waters draining towards the Mediterranean sea(s). The genus is represented around the Black Sea only by the very euryecious Echinogammarus foxi . Its presence there and in the Euphrates may be a more recent invasion, similar to E. berilloni in the West. The placement of Gammarus olivii Milne Edwards, 1830 is debatable – it might also be present in the Atlantic, as supposed by Stock (1993), or belong to Marinogammarus , as supposed by Sexton & Spooner (1940).

Remarks

Homoeogammarus is an available name for the majority of the ‘ Echinogammarus ’ species designated ‘ Echinogammarus pungens group’ by Stock (1968) or ‘Mediterranean Echinogammarus ’ by Hou et al. (2014). Ostiogammarus S. Karaman, 1931 is unavailable because its author did not state the type species, whereas Stock (1968) and Barnard & Barnard (1983) awkwardly foisted upon it the same type species as for Echinogammarus . Schellenberg’s name Homoeogammarus was made available by Barnard & Barnard (1983), who selected the North African (and probably Lusitanian) G. (H.) simoni for the type species. This species appeared to be a member of the monophylum composed of all peri-Mediterranean ‘ Echinogammarus ’ species treated here, inhabiting brackish or fresh waters of the area, with the exclusion of the Black Sea and the area of the former Dinaric Lakes System ( sensu Harzhauser & Mandic, 2008 ). Homoeogammarus is a sister clade to the diverse Ponto- Caspian group of genera.

Karaman (1977b) already substantiated the synonymizing of Neogammarus Ruffo, 1937 with Echinogammarus . In our tree and amended system, Neogammarus nudus Stock, 1971 is clearly a member of Homoeogammarus . Similarly, the genus Laurogammarus (for Carinogammarus scutarensis Schäferna, 1922 ), characterized only by an elongated and curved conus excretorius ( Pinkster, 1993), may be abandoned and its only species retained as Homoeogammarus scutarensis (Schäferna, 1922) .

Homoeogammarus as conceived here is inevitably paraphyletic, as the mainly continental Dinaric group of species (dinarogammarids) fall morphologically within the Homoeogammarus and could not be morphologically defined as a practicable genus. On the other hand the very diverse Ponto-Caspian group, by taxonomical practice split into 33 genera ( Grabowski, 2014), cannot be merged with Homoeogammarus .