Porpita porpita ( Linnaeus, 1758 )

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 70-71

Porpita porpita ( Linnaeus, 1758)

Fig. 46

Medusa porpita Linnaeus, 1758: 659 .

Porpita pacifica .— Eldredge & Devaney, 1977: 107, fig. 2.— Hoover, 1998: 23, fig.; 2006: 23, fig.

Type locality. “Habitat in India ” ( Indian Ocean ) ( Linnaeus 1758) .

Material examined. Oahu: Lanikai Beach, shore, 22.vi.1972, low tide, one colony, 2.6 cm in diameter, coll. Frances Frazier, BPBM D452 .

Description. Hydroid colony pleustonic, polymorphic, with disc-shaped mantle overlying a chitinous float. Upper surface of mantle and float slightly concave, with scattered hollow papillae, central pore and peripheral stigmata indistinct; lower surface with one short, broad central gastrozooid, a medial ring of gonozooids, and a peripheral ring of dactylozooids, with most gonozooids and dactylozooids missing in present material. Gonozooids vermiform to club-shaped, with nematocyst knobs scattered over body and arranged in a whorl at distal end. Dactylozooids club-shaped, somewhat triangular in cross-section distally, with short capitate tentacles in three vertical rows over body and arranged in a whorl at distal end. Nematocyst reservoir disc-shaped, internal, between gastrozooid and float.

Gonophores free medusae, arising in clusters from base of gonozooids.

Remarks. The taxonomy of this hydrozoan was thoroughly reviewed by Bigelow (1911). While he recognized Porpita pacifica Lesson, 1826 as the valid name for the species in the Pacific Ocean, Moser (1925) and Totton (1954) have been followed here in considering it synonymous with P. porpita ( Linnaeus, 1758) . An account of the cnidome has been given in a previous report ( Calder 1988). Additional information on the species is given by Schuchert (2010).

The hydroid stage of Porpita porpita is a component of the open ocean pleuston, and specimens occasionally wash ashore in Hawaii ( Eldredge & Devaney 1977; Hoover 1998, 2006). Colonies are deep blue in colour when alive. Besides hydroid and medusa, the life cycle includes several juvenile stages, including a rataria “larva” and a young pleustonic hydroid stage.

Recorded distribution. Hawaii. Oahu: off the windward coast ( Eldredge & Devaney 1977, as Porpita pacifica ). Maui: Molokini Islet ( Hoover 1998, 2006, as Porpita pacifica ).

Worldwide. Circumglobal, tropical and temperate waters; pleustonic ( Calder 1988; Schuchert 2010).