Gastroblasta

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 : 11

? Gastroblasta sp.

( Fig. 3 E)

Material examined. Stn. 7, 23.i.2012, 6 m, M019: four fragments on Amphimedon compressa (Porifera) bearing numerous hydrothecae, but no gonothecae (MHNG-INVE-82920).

Description. Hydrothecal pedicels arising irregularly from within the inhalant pores of the sponge host; hydrorhiza deeply embedded in host's tissues. Pedicels annulated basally and distally, sometimes in between, protruding at 365–1700 µm above surface of sponge, diameter 80–105 µm; each carrying a hydrotheca distally. Hydrotheca campanulate with slightly diverging walls from base to rim, 505–620 µm high, 310–380 µm wide at aperture; subhydrothecal chamber rather tall, 90–120 µm high; diaphragm well marked, a ring of desmocytes above; margin with 9–10 wide, triangular, moderately high cusps with rounded tips. Hydranths with ca. 20 tentacles. Gonothecae absent.

Remarks. Clytia -like polyps of the genus Gastroblasta Keller, 1883 , living in symbiotic associations with sponges, are only known for G. r a f f a e l e i Lang, 1886 ( Gravili et al. 2007). The two remaining congeners, G. t i m i d a Keller, 1883 from the Red Sea, and G. o v a l i s ( Mayer, 1900) from Florida, are only known from their medusa stage. The present hydroid may represent the polyp of G. o v a l i s, though rearing experiments or genetic data are necessary to test this assertion.

Geographical distribution. The sole known record of this hydroid is from Martinique, while the medusa of G. ovalis occur from Florida ( Mayer 1900) to Brazil ( Vannucci 1949).

Figures

FIGURE 3. A, B: Clytia hemisphaerica (Linnaeus, 1767) ― hydro- (A) and gonotheca (B). C, D: Clytia noliformis (McCrady, 1859) ― hydro- (C) and gonotheca (D). E:? Gastroblasta sp. ― hydrotheca. F, G: Orthopyxis sargassicola (Nutting, 1915) ― hydro- (F) and gonotheca (G). H, I: Egmundella humilis Fraser, 1936 ― hydro- and nematothecae from samples M 231 (H) and M 007 (I). J – P: Relative sizes of the hydrothecae of the hebellids discussed in the text. J, Q, R: Anthohebella communis (Calder, 1991) ― hydrothecae (J, Q) and gonotheca with medusoid gonophore (R). K, S, T: Hebella dyssymetra Billard, 1933 ― hydrothecae. L, U – Y: Hebella scandens (Bale, 1888) ― hydrothecae (L, U); gonotheca seen laterally (V) and apically (X), showing the four-flapped operculum; gonophore (Y). M, Z: Hebella sp. 1 ― hydrotheca. N: Hebella sp. 2 ― hydrotheca. O: Hebella sp. 3 ― hydrotheca. P: Hebella sp. 4 ― hydrotheca. Scale bars: 200 µm (H, I, Z), 300 µm (A – E, S, T), 500 µm (Q, R, U – Y), 1 mm (F, G, J – P).