Hebella sp.

Calder, Dale R. & Faucci, Anuschka, 2021, Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands, Zootaxa 5085 (1), pp. 1-73 : 13-15

Hebella sp.

Fig. 4b

Voucher material. Midway Atoll, on a hydroid stem, 23 ix.2002, one colony, with two hydrothecae, 1.3 mm high, without gonothecae, ROMIZ B5493 .

Remarks. This hydroid could not confidently be assigned to any known species of the family Hebellidae Fraser, 1912 . Its characters are closest to those of the hebellid genera Hebella Allman, 1888 (type species: Hebella striata Allman, 1888 ) and Anthohebella Boero, Bouillon & Kubota, 1997 (type species: Lafoea parasitica Ciamician, 1880 ), purportedly distinguished by the morphology of their liberated gonophores. Although gonophores of H. striata are certainly medusoids or medusae ( Hartlaub 1905), their anatomy after liberation has yet to be described. Thus, the molecular phylogenetic relationship of H. striata and H. parasitica needs study to determine whether the two nominal genera they nomenclaturally typify are indeed distinct. The species examined here has therefore been provisionally assigned to Hebella . Given the absence of gonosomes, our specimen is best not dealt with as an undescribed species. It is different from a hydroid reported earlier by Calder (2020) from Oahu as Hebella sp. , identified above as Hebella furax Millard, 1957 , and the species it represents is new to Hawaii.

In having a distinct, annulated pedicel, a deeply campanulate to almost cylindrical hydrotheca, hydrothecal walls with modest transverse annulations, a strongly flaring hydrothecal rim, and a ring of thickened perisarc at the hydrothecal base, this species most closely resembles Hebella venusta ( Allman, 1877) . However, it differs in having fewer and less distinct annulations on the hydrothecal wall. Moreover, its hydrothecae are larger (ca. 1000 µm long × 400 µm wide) than those of H. venusta as measured by Calder (1991a: to 650 µm long × 300 µm wide) and Galea (2010: 470–545 µm long × 265–315 µm wide). In terms of biogeography, H. venusta may be endemic to the Atlantic Ocean; records of it from the Indian Ocean ( Ritchie 1910, as Lafoea venusta ) and the Red Sea ( Mergner & Wedler 1977) are regarded here as questionable.

In the molecular barcoding studies of Moura et al. (2012) and Maronna et al. (2016), H. venusta and A. parasitica have been shown to be very close. Gonothecae of the two also appear to be morphologically similar (Boero et al. 1997; Galea 2010), although the medusoid or medusa stage of H. venusta is unfortunately still unknown.

Reported Distribution. Hawaiian archipelago. First record.

Genus Hebellopsis Hadži, 1913

Figures

FIGURE 4. Hebellidae. a, Hebella furax Millard, 1957, hydrotheca, Midway Atoll, ROMIZ B5407. Scale equals 0.1 mm. b. Hebella sp., hydrotheca, pedicel, and stolon, Midway Atoll, ROMIZ B5493. Scale equals 0.2 mm. c, Hebellopsis scandens (Bale, 1888), hydrotheca and pedicel, Pearl & Hermes Atoll, ROMIZ B5413. Scale equals 0.1 mm. d, Hebellopsis sibogae Billard, 1942, hydrotheca and pedicel, Pearl & Hermes Atoll, ROMIZ B5410. Scales equal 0.1 mm. e, Hebellopsis sibogae Billard, 1942, hydrotheca and pedicel, Pearl & Hermes Atoll, ROMIZ B5411. Scale equal 0.1 mm. e,