Aglaophenia rhynchocarpa Allman, 1877

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 : 35-38

Aglaophenia rhynchocarpa Allman, 1877

(Plate 3; Fig. 9)

Aglaophenia rhynchocarpa Allman, 1877: 40 , pl. 23 figs 5–8.― Nutting, 1895: 89; 1900: 90, pl. 18 figs 1, 2.― Wallace, 1909: 137.― Nutting, 1919: 115.― Fraser, 1944: 387, pl. 84 fig. 377.― Vervoort, 1968: 73, fig. 34.― Bogle, 1975: 59, fig. 3.― Calder, 1997: 59, fig. 18.― Galea, 2010a: 31 , figs 1K, 8G–I.― Calder, 2013: 48 , fig. 14C.

? Aglaophenia gracillima Fewkes, 1881: 131 , pl. 3 figs 6, 8.― Nutting, 1900: 103, pl. 23 figs 6–8.― Fraser, 1944: 376, pl. 81 fig. 365.

Aglaophenia cylindrata Versluys, 1899: 49 , figs 19–21.― Jäderholm, 1903: 297, pl. 14 fig. 2.―Ritchie, 1909: 261.― Bennitt, 1922: 252.― Fraser, 1944: 370, pl. 80 fig. 360.

Aglaophenia rathbuni Nutting, 1900: 101 , pl. 22 figs 4–6.

Aglaophenia insolens Fraser, 1943: 81 , pl. 19 fig. 13; 1944: 377, pl. 82 fig. 367.

Material examined. Stn. 1, 18.ii.2012, 13 m, M214: numerous plumes, up to 5.5 cm high, some with female corbulae, epizoic on sponge (MHNG-INVE-82883). Stn. 3, 19.ii.2012, 10– 15 m, M230: numerous plumes, up to 9 cm high, some bearing male or female corbulae, epizoic on sponge and Thyroscyphus marginatus (MHNG-INVE- 82884). Stn. 5, 08.ii.2012, 2– 3 m, M159: numerous sterile plumes, up to 4 cm high, epizoic on sponge and T. marginatus (MHNG-INVE-82917). Stn. 6, 28.i.2012, 10– 18 m, M093: several plumes, up to 5 cm high, a couple of them with male corbulae, epizoic on sponge and T. marginatus (MHNG-INVE-82882). Stn. 8, 25.i.2012, 12– 15 m, M052: numerous plumes, up to 4.5 cm high, some with male corbulae (MHNG-INVE-82878); M054: numerous plumes, up to 8 cm high, some with female corbulae, epizoic on sponge (MHNG-INVE-82879); M057: numerous plumes, up to 7.5 cm high, some with female corbulae, epizoic on sponge and T. marginatus ( Allman, 1877) (MHNG-INVE-82880); 27.i.2012, 9– 15 m, M068: numerous plumes, up to 12 cm high, some with female corbulae, epizoic on sponge and T. marginatus (MHNG-INVE-82881). Additional material examined: Guadeloupe, Stn 14. 8, 05.xii.2009, 17 m, HRG-0582: fertile (male) colony on limestone.

Remarks. The nodes of the stem are indistinct, each "internode" carrying the following: 1) a latero-distal apophysis supporting a cladium (Fig. 9D1); 2) a mamelon at the base of the apophysis, provided with a reduced, cone-shaped nematotheca, with small, rounded aperture (Fig. 9D, E, arrowheads); 3) a pair of nematothecae flanking each side of the apophysis; each nematotheca is provided with two apertures: a rather small, rounded, lateral one, and a wide, ovoid, situated posteriorily in the axil formed by the nematotheca and the stem internode (Fig. 9F); 4) one (Fig. 9E) or two (Fig. 9D) additional nematothecae below the apophysis, these generally provided with a small, rounded, frontal aperture (Fig. 9G), rarely with two (Fig. 9H), as well as with a large, ovoid aperture on the posterior side of the theca (better seen in lateral view, Fig. 9G2).

There are notable differences in the spacing of cladia (Fig. 9A), depending on the number of nematothecae (one or two) carried on by the stem internodes, their position with respect to the length of the internode and, implicitly, their proximity with the cladial apophyses. The specimens from Guadeloupe described earlier by myself ( Galea 2010a) were compared to the present material from Martinique. It appears that cormoids of the former exhibit the most approximated cladia, which are only 515–645 µm distant (Fig. 9A4). Their stem internodes always carry a single nematotheca that is almost fused to the base of the cladial apophysis (Fig. 9E). In sample M159, the cladia are 645–715 µm distant (Fig. 9A3), and recall the material from Guadeloupe. In contrast, the sample M068 has cormoids with stem internodes that carry one, occasionally two, nematothecae; the proximal one is situated in the middle of the internode, while the second is almost fused to the apophysis, producing a spacing between the cladia of 950–1170 µm (Fig. 9A2). An extreme situation is met with in sample M093, whose cladia are 1300–1465 µm distant (Fig. 9A1). Their stem internodes carry generally two nematothecae, more rarely only one; these are equidistantly spaced along the internode (Fig. 9D1), occasionally with the superior nematotheca very close to the apophysis (Fig. 9D2).

FIGURE 9. A–L: Aglaophenia rhynchocarpa Allman, 1877 ―four cormoids showing different spacing of cladia in specimens from Martinique [samples M093 (A1), M068 (A2), and M159 (A3)] and Guadeloupe (A4); differences in length of cormidia between specimens from Martinique (B1) and Guadeloupe (B2); hydrotheca in lateral (C1), frontal (C2), and apical (C3) views; stem internode from sample M093 in frontal (D1) and lateral (D2) views, compared to specimen from Guadeloupe (E, lateral view); pair of nematothecae flanking the stem apophyses (F); stem nematotheca in frontal (G1) and lateral (G2) views, note single frontal aperture; stem nematothecae in specimen from Guadeloupe in frontal (H1, H2) and lateral (H3) views, note the pair of lateral apertures; basal part of a female corbula in lateral view (I); detail of a male (J) and a female (K) corbula; unpaired costa (L). Scale bars: 100 µm (F–H), 200 µm (C–E), 300 µm (B, I–L), 1 cm (A).

PLATE 3. Aglaophenia rhynchocarpa Allman, 1877 ―male (A) and female (G) corbulae; overview of the central (B) and distal (C) parts of a male corbula; lateral (D) and dorsal (E, F) views of a male corbula showing the pair of basal nematothecae flanking the lateral spikes; ventral and lateral views of a female corbula showing the lateral spikes (H, J) and the costae (I).

Corbulae of this species occur in many of the specimens from Martinique. They show a conspicuous sexual dimorphism, with the males (Plate 3A) being longer (6.5 vs. 3.0 mm) and more slender than the females (Plate 3B), as well as more flattened dorso-ventrally. Each corbula is composed of a basal hydrotheca and a non-segmented rachis (Plate 3D–F) bearing alternately up to 18 (in males) or 10 (in females) spike-like processes, each of which carrying a costa (Plate 3I, J; Fig. 9I). Each process bears two basal nematothecae at its origin from rachis (one to each side, Plate 3D–F), as well as 2–3 (in males, Fig. 9J) or 3–4 (in female, Fig. 9K) nematothecae on its trunk (Plate 3C, H, J). The costae are given off upwardly from the bases of the lateral processes of the rachis, and are broad, leaf-like structures, arching over the gonothecae (Plate 3I). Each costa is composed of two, occasionally three, fronto-distal nematothecae in males (Fig. 9J), and 5 in females (Fig. 9K). Unpaired, irregularly placed costae (one, exceptionally two per corbula), bearing numerous nematothecae, mostly on one side, are occasionally found in the female corbulae (Fig. 9L). All nematothecae are tubular to globular, and are provided with two apertures, one rounded and terminal, the other large and ovoid, situated on a side of the theca.

Except for the larger size of the thecae in the material from Martinique (Fig. 9B1), compared to the specimens from Guadeloupe (Fig. 9B2), there are no other significant differences among the colonies, though the extreme habits exhibited by some cormoids (compare Fig. 9A1 and 9A4), give the impression that macroscopically we are dealing with different species.

I follow Bogle (1975) who, after examining the types of A. rathbuni Nutting, 1900 and A. insolens Fraser, 1943 , reached the conclusion that both are coterminous, and hypothesized that the former is merely a variant of A. rhynchocarpa . I equally agree with Vervoort (1968), who included A. cylindrata Versluys, 1899 into its synonymy.

In addition, Aglaophenia gracillima Fewkes, 1881 , a deep-water species whose type locality is Martinique, shows striking resemblances with Allman's species, the latter being omnipresent at all shallow-water stations inspected during the present study. The account by Fewkes is rather succinct and his illustrations are sketchy, but type material was reexamined by Nutting (1900), who provided a more detailed description and better illustrations. The sole distinguishing character between A. gracillima and A. rhynchocarpa is found in the extreme hypertrophy of the hydrothecal carina and, to a lesser extent, of the median cusp in the former nominal species. Bogle (1975), upon examination of her GERDA material assigned to Allman's species, noted the following: "Median tooth very variable in size and occasionally greatly enlarged. […] Strength of carina variable." In addition, the corbula illustrated by Nutting (1900) for A. gracillima strongly recalls the female corbula in specimens from Martinique, with the sole exception concerning the increased number of hydrothecae (3 of these are figured by Nutting) at the base of the modified cladium. Given the data available at present, it would be too early to conclude on a possible conspecificity between the two nominal species, but the finding of additional material corresponding to the phenotype of A. gracillima will certainly allow estimating its degree of intraspecific variation.

Geographical distribution. Bogle (1975) indicated that the species extends from Bermuda in the North, to Barbados in the South, the Yucatan Channel in the West, and the Lesser Antilles in the East. To this, it should be added the record by Nutting (1900, as A. rathbuni ), which extends its latitudinal range of distribution to Brazil.