Hydra sp.

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 44-45

Hydra sp.

Figs. 30, 31

Hydra .— Mumford, 1940: 243.

Hydra sp. — Bailey-Brock & Hayward, 1984: 199, fig. 1B.

Material examined. Kauai: AMFAC–Kekaha, from prawn ponds, associated with Hyalinella vaihiriae (Bryozoa) , viii.1982, several hundred polyps, to 1 mm high (preserved), many with buds, coll. J. Brock, BPBM (without collection number) .– Kauai: AMFAC– Kekaha, from prawn ponds, associated with Hyalinella vaihiriae (Bryozoa) , viii.1982, several polyps from sample above, to 1 mm high (preserved), many with buds, coll. J. Brock, ROMIZ B3831 .

Description. Hydroids solitary, with flattened basal disc; algal symbionts absent. Hydranths columnar to bulbous in preserved material, up to about 1 mm high, lacking perisarc, with a distal whorl of 5–7 filiform tentacles; hypostome flattened and usually indistinct. Contracted tentacles tapering distally, heavily armed with nematocysts. Many polyps with lateral buds arising from lower hydranth wall, often with more than one per individual; tentacles on buds formed synchronously.

Gonads not seen.

Nematocysts (Fig. 31).

desmonemes (6.0–6.7 µm long × 4.3–4.9 µm wide)

atrichous isorhizas (6.8–7.2 µm long × 3.0–4.0 µm wide)

holotrichous isorhizas (8.0–9.4 µm long × 3.9–4.3 µm wide)

stenoteles (10.0–15.8 µm long × 8.0–13.1 µm wide)

Remarks. In an overview of animal distributions on oceanic islands, Mumford (1940) noted that “ Hydra ” had been collected near the University of Hawaii and from other localities on the island of Oahu. Bailey-Brock & Hayward (1984) also discovered Hydra sp. in Hawaii, growing on the freshwater bryozoan Hyalinella vaihiriae Hastings, 1929 in prawn ponds on Kauai in 1982. The aquaculture farm where specimens were found was later closed and there have been no subsequent published reports of Hydra sp. from the Hawaiian Islands. Material from that source was deposited in collections at the Bishop Museum and was examined here. Many of the specimens were undergoing asexual budding, but no gonads were observed and identification to species was not possible from preserved material. From the morphology of the holotrichous isorhizas (Fig. 31d), however, the species appears to belong to a clade that includes H. vulgaris Pallas, 1766 and H. carnea L. Agassiz, 1850 , among others ( Hemmrich et al. 2007).

A species thought referable to Hydra Linnaeus, 1758 (described as a “pink hydra”) was collected from a stream on the Island of Hawaii in 2006 (Lucius Eldridge, pers. comm., 2 May 2006). No specimens from that discovery were found in collections at the Bishop Museum and nothing more is known here about the record .