Merga Hartlaub, 1913

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 26-27

Genus Merga Hartlaub, 1913

Merga Hartlaub, 1913: 249 .

Type species. Pandea violacea A. Agassiz & Mayer, 1899 [ Merga violacea ], by monotypy.

Diagnosis. Pandeid hydroids stolonal or with small, erect, and slightly branched cormoids, arising from a creeping hydrorhiza. Erect colonies with monosiphonic hydrocaulus. Perisarc filmy to firm, covering hydrorhiza, hydrocauli, hydrocladia, and pedicels, terminating near hydranth base or forming a pseudohydrotheca, not enveloping bases of tentacles. Hydranths club-shaped to fusiform; tentacles filiform, amphicoronate, in a distal whorl; hypostome conical to dome-shaped.

Gonophores where known free medusae, borne on hydrocauli or hydrorhiza. Medusae bell-shaped, with or without apical process; manubrium of moderate length, not twisted, cruciform in cross-section at base, perradial edges with mesenteries extending to radial canals, oral lips four, simple to slightly folded; radial canals four; marginal tentacles four, eight, or more, all filiform; rudimentary tentacle bulbs and tentaculae present or absent; ocelli present or absent; gonads adradial or interradial, smooth or granulate, on manubrium, not located on folds or pits of manubrial wall.

Remarks. Hartlaub (1913) established Merga to accommodate Pandea violacea A. Agassiz & Mayer, 1899 , a pandeid medusa having gonads without folds. By mid-20 th century four species were included in the genus ( Kramp 1961: 106–107, 444), and the number is currently nine ( Schuchert 2009). Most are known only as the medusa stage. Where described, hydroids are small and have few distinguishing morphological characters. The genus Merga has been reviewed and revised a number of times, most recently by Schuchert (1996, 2007) and Brinckmann-Voss & Arai (1998).