Macrorhynchia clarkei ( Nutting, 1900 )

Galea, Horia R., 2010, Additional shallow-water thecate hydroids (Cnidaria: Hydrozoa) from Guadeloupe and Les Saintes, French Lesser Antilles, Zootaxa 2570, pp. 1-40 : 32-33

Macrorhynchia clarkei ( Nutting, 1900)

(figs 1I, 8J–O)

Lytocarpus clarkei Nutting, 1900: 124 , pl. 32 figs 5–7.― Fraser, 1944: 416, pl. 92 fig. 406A–E.― Vervoort, 1959: 302, fig. 50A–C.― Vervoort, 1968: 80, fig. 37A, B.

Macrorhynchia clarkei ― Calder, 1997: 65, fig. 20C.

Nematophorus clarkei ― Ansín Agís et al., 2001: 104, fig. 47.― Vervoort, 2006: 263.

not Lytocarpus clarkei ― Bennitt, 1922: 254 [= Macrorhynchia allmani ( Nutting, 1900) ].

Material examined. Stn.19: 26.11.2009, 11 m—several sterile colonies to 15 cm high, removed from hard substrate (part as MHNG-INVE-68735).

Remarks. For a recent description of this species, see Ansín Agís et al. (2001). I agree with the arguments provided by Calder (1997), and consider the genus Nematophorus Clarke, 1879 as a synonym of Macrorhynchia Kirchenpauer, 1872 . The diagnosis of the latter has been emended to include species forming pseudo-corbulae ( Bouillon et al., 2006).

Perfectly cleared hydrothecae seen from above show that the mesial and lateral nematothecae could have their apertures either opened from apex to adaxial wall of hydrotheca (fig. 8N) or closed in the middle and open apically and at juncture with hydrothecal wall.

The rear pair of hydrothecal cusps is the widest and shallowest, and is almost fused to the lateral nematothecae, as seen in frontal view of hydrothecae (fig. 8M). There is a conspicuous mamelon on the basal part of the internode apophysis, bearing a large, nearly circular aperture (fig. 8J, K). There are generally two nematothecae per internode: the basalmost one is generally ovoid in shape and its aperture is directed to the same side as the apophysis, whereas the latero-superior nematotheca is generally triangular in shape (fig. 8J). I am able to confirm that the latter nematothecae apparently bear two latero-distal apertures when seen frontally (fig. 8O1), but there is actually only one when viewed from above (fig. 8O3); the distal part of the abaxial wall is inwardly rolled, looking as though it is fused to the internode behind. Transitions between the two shapes of internodal nematothecae may occur in the same specimen. Occasionally, a third ovoid nematotheca occurs between the basal and the latero-superior ones (fig. 8K); it can reach the mamelon and almost fuse with it, exhibiting two close-set, circular apertures, often of different sizes.

Caribbean records. Puerto Rico ( Fraser 1944), St. Thomas ( Vervoort 1968).

World distribution. Off La Havana, Cuba ( Nutting 1900; Fraser 1944), the Bahamas ( Nutting 1900), off Yucatan ( Fraser 1944), Cape Verde ( Vervoort 1959, Ansín Agís et al. 2001, Vervoort 2006).

FIGURE 8. A to F: Aglaophenia postdentata Billard, 1913 —basal part of cormoid (A); prosegment (B); stem internode with nematothecae and basal part of cladium (C); two cormidia (D); hydrotheca in frontal view showing marginal cusps (E); nematothecae (F)—lateral (F1), mesial (F2), associated to apophysis (F3), internodal (F4, F5). G to I: Aglaophenia rhynchocarpa Allman, 1877 —two cormidia (G); apical view of hydrotheca (H); corbula ribs in lateral view (I). J to O: Macrorhynchia clarkei ( Nutting, 1900) —two stem internodes with associated nematothecae and origin of cladia (J, K); hydrotheca in lateral (L), frontal (M), and apical (N) views; nematothecae (O)—double-sided nematotheca in frontal (O1) and apical (O3) views; single-sided nematotheca viewed frontally (O2). P: Macrorhynchia philippina Kirchenpauer, 1872 —hydrotheca. Scale bars: 50 µm (B, F, H, O); 100 µm (E, L, M, N, P); 200 µm (C, D, G, J, K); 400 µm (A, I).