Velella velella ( Linnaeus, 1758 )

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 71-72

Velella velella ( Linnaeus, 1758)

Fig. 47

Medusa velella Linnaeus, 1758: 660 .

Velella pacifica .— Edmondson, 1933: 27; 1946: 28.– Reed, 1971: 49.

Velella velella .— Eldredge & Devaney, 1977: 107, fig. 1b.– Hoover, 1998: 23, fig.; 2006: 23, fig.

Type locality. “Habitat in Pelago. Loefling. In Mari Mediterraneo. Brander” ( Linnaeus 1758). The Mediterranean Sea may be taken as the type locality of the species ( Schuchert 2010).

Material examined. Pearl and Hermes Reef, Northwest Hawaiian Islands: iv.1927, nine colonies, all leftsailing forms, up to 4 cm long × 2.5 cm wide, coll. T. Dranga, BPBM D145 .– Maui : Makena, 1926, one colony, right-sailing form, 2.9 cm long × 1.8 cm wide, coll. J.K. Skinner, BPBM D146 .– Oahu : Wianae coast, 04.vi.1941, 1 specimen (dry), BPBM D237 .– Oahu : Kaneohe Bay, land side of Chinaman’s Hat Islet, 03.x.1971, two colonies, both right-sailing forms, 1.5 cm long × 0.7 cm wide, coll. D.M. Devaney, BPBM D453 .

Description. Hydroid colonies pleustonic, polymorphic, with soft mantle overlying an oval chitinous float. Upper surface of mantle with an erect, triangular sail reinforced internally by triangular extension of float; hydroids in two enantiomorphic forms, with sail of some oriented along the NW to SE diagonal and others oriented along the NE to SW diagonal when long axis of float positioned N and S. Lower surface with one long, broad, essentially tubular central gastrozooid, a medial ring of gonozooids, and a peripheral ring of dactylozooids. Gonozooids club-shaped, with nematocyst knobs scattered over body and arranged in a whorl at distal end. Dactylozooids tentacle-like in form, oval in cross section, lacking tentacles. Nematocyst reservoir elongate-oval, internal, between gastrozooid and float.

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

Remarks. Information on synonymy, cnidome, and development of Velella velella ( Linnaeus, 1758) has been summarized earlier ( Calder 1988). Further details on the biology of the species are summarized in Schuchert (2010).

The life cycle of V. velella is metagenetic, with both hydroid and medusa stages. From the research of Woltereck (1904, 1905) in the Mediterranean, early development occurs in deep water as a conaria larva. Very young conaria larvae have a rudimentary fluid-filled float, a mouth, and two tentacles. As development proceeds, an organ called the crimson cone appears, which secretes oil droplets as a means of flotation. Conaria rise to the surface and gradually metamorphose into rataria larvae having an air-filled float, developing zooids, and a nascent sail; meanwhile, the crimson cone is lost. With continued development, the rataria becomes the floating colony more immediately recognizable as V. velella .

There has been confusion over terminology applied to the dimorphic forms of Velella velella . Right-sailing and left-sailing types described here are as defined by Edwards (1966). Thus, with the longitudinal axis of the float oriented north and south, the sail runs from NW to SE in left-sailing forms and from NE to SW in right-sailing forms.

According to Edmondson (1933, 1946), Velella pacifica [ V. velella ] is frequently stranded on Hawaiian shores by strong winds. By contrast, Hoover (1998, 2006) noted that the species is uncommon in Hawaii. Colonies are deep blue in colour when alive.

Recorded distribution. Hawaii. No specific location given ( Edmondson 1933, 1946). Oahu, Kaneohe Bay ( Reed 1971). No location given ( Eldredge & Devaney 1977). Oahu: Kahuku ( Hoover 1998, 2006).

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