Corydendrium corrugatum Nutting, 1905

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 10-11

Corydendrium corrugatum Nutting, 1905

Figs. 1 , 2

Corydendrium corrugatum Nutting, 1905: 941 , pl. 2, fig. 2, pl. 7, figs. 5–7.— Calder, 2004: 20.

Type locality. Hawaii: “south of…Oahu, 319 fathoms” (583 m) ( Nutting 1905). This station was actually south of Molokai, not Oahu .

Material examined. Molokai: Albatross Stn. 3828, off south coast, 583 m, 01.iv.1902, one fragmentary colony, about 15 cm high, without gonophores, USNM 22150 [LECTOTYPE; bottle also contains an antipatharian overgrown by an operculate hydroid].–Molokai: Albatross Stn. 3828, off south coast, 583 m, 01.iv.1902, seven colony fragments, up to 9 cm high, without gonophores, USNM 52582 [PARALECTO- TYPE; bottle also contains an antipatharian and a lafoeid hydroid].–Maui: Albatross Stn. 4077, off northeast coast, 99 fm (181 m), 21.vii.1902, several colony fragments, largest fragment 2.9 cm high, with poorly preserved hydranths, without gonophores, USNM 22171 [PARALECTOTYPE; this material, identified as Corydendrium corrugatum , labelled “cotype,” and mentioned by Nutting (1905) under the distribution of that species, is referable instead to Balella mirabilis ( Nutting, 1905) ].–Oahu: Waianae, on Mahi wreck, 60–90 ft (18–27 m), 05.xi.2003, one colony fragment, 6 cm high, without gonophores, coll. S. L. Coles, BPBM (without collection number).–Oahu: Waianae, on Mahi wreck, 60–90 ft (18–27 m), 05.xi.2003, one colony fragment, 5.5 cm high, without gonophores (cormoids of Monotheca sp. also present), coll. S. L. Coles, ROMIZ B3819.

Description. Hydroids with erect, robust colonies up to about 15 cm high, arising from a tangled mass of creeping hydrorhizal fibres. Hydrocaulus strongly polysiphonic, up to 6–7 mm thick basally, twisted and rootlike in shape, irregularly branched; larger branches polysiphonic and resembling hydrocaulus; smaller, more distal branches tending to be curved, adnate for part of their length to hydrocaulus or to hydrocladia from which they arise, sometimes with a constriction near base, polysiphonic basally, becoming monosiphonic at distal extremity; anterior surface of smaller branches giving off hydrophore-like ultimate branchlets reaching to base of hydranths; ultimate branchlets of varied length but mostly short, alternate, relatively close, adnate to their supporting branch, not annulated but with variably developed concentric wrinkles over much or all of free distal part. Perisarc of moderate thickness, sometimes with wrinkles but mostly smooth except on ultimate branchlets, brown in older parts of colony, becoming straw-coloured distally. Hydranths clavate, retractable into perisarcal sheath of pedicel, about 0.8 mm long, with filiform tentacles scattered over distal half or more of hydranth; tentacles numerous,> 20 in number; hypostome elongate to dome-shaped, crater-shaped when wide open.

Gonophores not seen.

Remarks. Corydendrium corrugatum Nutting, 1905 was originally described from bathyal waters off Hawaii. Hydroids were distinguished by Nutting (1905) from those of C. parasiticum ( Linnaeus, 1767) in having a thicker and more rigid hydrocaulus, and in having distinct and decidedly corrugated hydrophores. The species, provisionally recognised as valid here, has also been reported (or tentatively reported) from Indonesia ( Schuchert 2003; Di Camillo et al. 2008). Also resembling C. corrugatum are hydroids identified as C. parasiticum from the Amakusa Islands ( Hirohito 1969) and Sagami Bay ( Hirohito 1988), Japan, and from northern Australia ( Watson 1999: fig. 2). Records from the western Pacific are from much shallower water (<50 m) than the original material from Hawaii.

Nutting (1905) did not designate a holotype for this species. Syntype material from south of Molokai (USNM 22150, USNM 52582) and from northeast of Maui (USNM 22171) exists in the NMNH. A sample from Albatross Station 4135, near Kauai (USNM 22172), has also been listed and marked as type material (it contains a label marked “cotype”) of the species, but it was not mentioned by Nutting (1905) and is not considered type material here. In fact, hydroids in both USNM 22171 and USNM 22172, re-examined here, are referable to Balella mirabilis Nutting, 1905 and not C. corrugatum . To clarify application of the name to a taxon, a large colony from off the south coast of Molokai (USNM 22150) is designated as lectotype of C. corrugatum , and colony fragments in another lot from the same station (USNM 52582) comprise paralectotype material. Alhough the paralectotype contains the hydroid fragment illustrated in Nutting’s (1905) Plate II, fig. 2, the lectotype colony is larger and overall a better representative of the species in my opinion.

The relationship between Corydendrium corrugatum and C. parasiticum is open to question. Some corrugations were evident on ultimate branchlets in all hydroids of this genus from Hawaii. It appeared to be more strongly developed in those assigned to C. corrugatum , but the difference was not absolute. Two species were recognized here based as much on bathymetry (with C. parasiticum in shallow inshore waters and C. corrugatum at greater depths) as on the degree of corrugation evident on the ultimate branchlets. Differences in a character such as the robustness of the hydrocaulus, noted by Nutting (1905), would seem to be variable and of limited value in differentiating the two.

Reported distribution. Hawaii. Albatross Stn. 3828, south of Molokai , (583 m); Albatross Stn. 4077, “northeast coast of … Maui, 99 fathoms” (181 m) ( Nutting 1905) .

Worldwide. Hawaii; (?) Indonesia; (?) Japan; (?) Australia; 16–583 m ( Hirohito 1969, as C. parasiticum ; Watson 1999, as C. parasiticum ; Schuchert 2003; Di Camillo et al. 2008).

Figures

FIGURE 1. Corydendrium corrugatum: part of hydrocaulus, hydranths lacking, ROMIZ B3819. Scale equals 0.5 mm.