Ectopleura mayeri Petersen, 1990

Galea, Horia R., 2013, New additions to the shallow-water hydroids (Cnidaria: Hydrozoa) of the French Lesser Antilles: Martinique, Zootaxa 3686 (1), pp. 1-50 : 9-10

Ectopleura mayeri Petersen, 1990

(Pl. 1J, K; Fig. 2N–Q)

Ectopleura mayeri Petersen, 1990: 166 , fig. 22.―Var el a et al., 2010: 30. Ectopleura pacifica ― Calder, 1988: 53, fig. 41 (not Ectopleura pacifica Thornely, 1900 ).? Ectopleura minerva Mayer, 1900: 31 , pl. 16 fig. 38, pl. 37 fig. 125.

? Ectopleura sp. Fewkes, 1883: 85, pl. 1 fig. 11.

Material examined. Stn. 6, 28.i.2012, 10– 18 m, M088: fertile colony from sponge substrate, and newly liberated medusae (MHNG-INVE-82914). Stn. 7, 24.i.2012, 6 m, M017: small, fertile colony on seaweed (MHNG-INVE- 82912); M029: fertile colony on sponge (MHNG-INVE-82913).

Remarks. Petersen (1990) provides a sound description of this species, but to this, it can be added that the aboral tentacles are monilifiliform, with nematocysts uniformly spread on their aboral side, and scattered, rather smooth patches on their adoral side. The oral tentacles are provided with a terminal capitation, a continuous band of nematocysts on their aboral side, and 1–3 rough, adoral patches with crowded capsules.

Newly liberated medusae were obtained from living colonies. The umbrella is dome-shaped, 390–485 µm high, 240–340 µm wide, depending on its state of contraction/relaxation. The mesoglea is thin, the exumbrella is provided with eight longitudinal tracks of nematocysts, while no scattered capsules could be observed on its surface. There are four marginal bulbs, of which two of them give rise to two short, opposite, perradial tentacles with a terminal capitation. The manubrium is globular, about half the length of the subumbrellar cavity. Live medusae have a yellow-orange manubrium, the nematocysts tracks are green fluorescent, while the marginal bulbs and the tentacle capitations are milky white, due to the presence of crowded nematocysts (Pl. 1K).

The cnidome of this species (not previously reported) is given for both the polyp and the medusa bud. The former contains five capsules: 1) small, ovoid stenoteles, (5.8–6.4)×(4.5–5.0) µm, in both aboral and oral tentacles; 2) small, rounded stenoteles, (6.6–7.2)×(5.6–6.4) µm, in both aboral and oral tentacles; 3) large stenoteles, (10.6– 11.7)×(9.6–10.4) µm, in the oral tentacles; 4) desmonemes, (4.5–4.8)×(3.4–3.7) µm, in the aboral tentacles; 5) ovoid microbasic mastigophores, (8.5–9.8)×(4.2–4.5) µm, in both oral and aboral tentacles. The newly liberated medusa contains six capsules: 1) small, ovoid stenoteles, (6.4–6.6)×(4.8–5.0) µm, in the marginal bulbs; 2) small, rounded stenoteles, (6.1–6.4)×(5.0–5.4) µm, in the marginal bulbs; 3) large stenoteles, (8.2–9.0)×(7.7–8.2) µm, in the marginal bulbs and the exumbrellar tracks; 4) desmonemes, (5.0–5.3)×(3.4–3.7) µm, in the marginal bulbs; 5) anisorhizas, (7.4–8.0)×(6.6–7.2) µm, in the exumbrellar tracks; 6) microbasic mastigophores, (7.2–8.0)×(3.7–4.0) µm, in the exumbrellar tracks.

Both Calder (1988) and Petersen (1900) questioned the conspecificity of Ectopleura minerva Mayer, 1900 , only known from its medusa stage, and the present hydroid. Some of the colors reported by Mayer (1900), notably the greenish tinge of the bell, are equally found in the buds and the newly liberated medusae of E. mayeri (Pl. 1J, K). As in E. minerva , young medusae of E. mayeri bear only two opposite perradiar tentacles, and their number is not expected to increase with age, similarly to E. obypa Migotto & Marques, 1999 . It could thus logically be assumed that the hydroid E. mayeri and the medusa E. minerva are coterminous. Either rearing experiments or genetic comparison could test this assumption.

Geographical distribution. Bermuda ( Calder 1988, as E. pacifica ), Caribbean coast of Panama ( Calder & Kirkendale 2005), Cuba ( Varela et al. 2010), Guadeloupe (Galea, unpublished results), Martinique (present study). Ectopleura minerva is known from Bermuda and Florida ( Mayer 1900).