Dictyocladium reticulatum (Kirchenpauer, 1884), 2003

Galea, Horia R. & Schuchert, Peter, 2019, Some thecate hydroids (Cnidaria: Hydrozoa) from off New Caledonia collected during KANACONO and KANADEEP expeditions of the French Tropical Deep-Sea Benthos Program, European Journal of Taxonomy 562, pp. 1-70 : 42-46

Dictyocladium reticulatum (Kirchenpauer, 1884)

Fig. 15

Dictyocladium reticulatum – Vervoort & Watson 2003: 124 , figs 24E–G, 25A–C.

Material examined

PACIFIC OCEAN • a colony, 3.5× 3.5 cm, with female gonothecae; off New Caledonia, stn DW4725; 22°41′ S, 167°05′ E; 240–256 m; 20 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA 1402;voucher MHNG-INVE- 120831; MNHN-IK-2015-405 • four colonies, 2.7× 1.6 cm (without gonothecae), 2.7× 3.8 cm (with female gonothecae), 3 × 2.9 cm (with female gonothecae) and 4× 2.6 cm (with female gonothecae); same collecting data as for preceding; MNHN-IK-2015-405 • a colony, 2.5× 1.7 cm, without gonothecae; off New Caledonia, stn DW4741; 22°52′ S, 167°41′ E; 210 m; 23 Aug. 2016; KANACONO leg.; used as a whole for DNA extraction, DNA 1371; voucher MHNG- INVE- 120832; barcode identifier MK 073094 ; MNHN-IK-2015-406 • three colonies, 4.3× 1.7 cm (without gonothecae), 4× 3.5 cm (with female gonothecae), and 3× 3.3 cm (with female gonothecae, and carrying epizoic Synthecium colony); same collecting data as for preceding; MNHN-IK-2015-406 • four colonies without gonothecae, 4.5 × 4 cm, 1.5× 1 cm, 1.5 × 2 cm, and 2.5× 1 cm, respectively; off New Caledonia, stn CP4674; 22°48′ S, 167°29′ E; 311– 302 m; 13 Aug. 2016; KANACONO leg.; MNHN- IK-2015-407 • a fertile colony, 5.2× 5.5 cm; off New Caledonia, stn DW4743; 22°52′ S, 167°34′ E; 380– 340 m; 23 Aug. 2016; KANACONO leg.; MNHN-IK-2015-468 .

Remarks

The present material agrees in nearly all details with the description given by Vervoort & Watson (2003) of this species. However, some colonies have their stems and the basal part of their lower branches lightly but distinctly fascicled. In addition, examination of many gonothecae (from different colonies) seen in apical view showed that the external ridges are not always spirally arranged, as stated by Vervoort & Watson (2003), but they also form concentric ridges that are perfectly transverse in lateral view. All gonothecae agreed with the supposedly female ones described by these authors, but had up to 14 ridges in material MNHN-IK-2015-405 and up to 20 in material MNHN-IK-2015-406, although any other morphological difference could be noted (e.g., a slenderer appearance, as in the supposedly males described by these authors).

The 16S data (see Fig 20 and the ‘Molecular study’ section) strongly suggest that this species belongs to the Symplectoscyphidae , and not the Sertularidae in the sense of Maronna et al. (2016).

Distribution

Bass Strait, Tasmania ( Vervoort & Watson 2003), New Caledonia (present study).

Genus Symplectoscyphus Marktanner-Turneretscher, 1890

? Symplectoscyphus acutustriatus Galea , sp. nov.

urn:lsid:zoobank.org:act:DDBE1A82-BE69-405E-A1AD-E5093423E389

Figs 16A , 17 A–E; Tables 8–10

Diagnosis

Colonies erect, with up to 2.5 cm high, monosiphonic, sparingly-branched stems, divided into moderatelylong, geniculate, regular internodes by oblique nodes slanting in alternate directions. Branches with similar structure to that of the stems. Hydrothecae biseriate, alternate, coplanar, conical, adnate for ⅓ or less to the internode, surface distinctly ridged; ridges projecting apically as almost free frills; 7–8 ridges on free axadial wall, 8–10 on abaxial wall; up to seven submarginal, internal projections of the perisarc, present in basalmost hydrothecae, but missing elsewhere and, sometimes, in a whole colony. Gonothecae borne laterally on the stem internodes; elongated-ovoid, transversely ringed, aperture on top of short neck region.

Etymology

The specific name combines two Latin words ‘ ăcūtus, -a, -um ’, meaning ‘sharp’, and ‘ strĭātus , -a, -um ’, meaning ‘provided with striae’, to describe the particulars of the transverse ridges of the outer hydrothecal wall.

Material examined

Holotype

PACIFIC OCEAN • a small, fertile colony on limestone, composed of five stems up to 2 cm high, four of which bear one gonotheca each; off New Caledonia, stn DW4977; 19°46′ S, 158°30′ E; 280–304 m; 9 Sep. 2017; KANADEEP leg.; MNHN-IK-2015-460.

Paratype

PACIFIC OCEAN • a rather profuse, colony on dead gorgonian with stems up to 2.5 cm high, without gonothecae; off New Caledonia, stn DW4945; 25°22′S, 159°43′E; 130– 108 m; 4 Sep. 2017;KANADEEP leg.; two small stems were used for DNA extraction, DNA1388; voucher MHNG-INVE- 120849; barcode identifier MK 073102 ; MNHN-IK-2015-461 .

Additional material

PACIFIC OCEAN • a colony composed of several stems, up to 2 cm high, without gonothecae; off New Caledonia, stn DW5026; 20°22′ S, 158°40′ E; 360–410 m; 21 Sep. 2016; KANADEEP leg.; MNHN- IK-2015-446.

Description

Colonies arising from creeping, branching, anastomosing hydrorhiza. Stems erect, monosiphonic, up to 2.5 cm high, composed of a basal, smooth, ahydrothecate part, 3–7 mm long above origin from stolon, and a much longer, distal, hydrothecate part above; the latter divided into regular internodes by means of almost indistinct oblique nodes slanting in alternate directions; branching sparse, with up to three coplanar side branches given off laterally and irregularly from below the bases of some stem hydrothecae, on one or both sides of the stem; branches with similar structure to that of the stem. Internodes relatively short, distinctly geniculate, each bearing distally a hydrotheca; the latter alternate in position, the two rows being coplanar. Hydrothecae moderately-long, conical, adnate for ⅓ or less to the corresponding internodes; surface conspicuously ridged; ridges well-developed, projecting apically almost as free frills; there are 7–8 complete ridges encircling the hydrotheca distally, and up to 8-10 on the abaxial wall, the basalmost ones incomplete; there are seven intrathecal, submarginal projections of the perisarc, visible in the lower stem hydrothecae, but disappearing towards distal parts of the colony: two latero-adaxial, one abaxial, and two latero-abaxial. Gonotheca borne on stems and/or branches, given off laterally in middle of internode on side opposite to hydrotheca; large, piriform, transversely-ridged (12–14 ridges), tapering abruptly basally into indistinct pedicel, distally walls merging progressively; aperture apical, small, rounded, on short neck region with broadly polygonal perimeter, occasionally forming 3 indistinct projections of perisarc.

Remarks

The prominent ridges on the outer walls of the hydrothecae are distinctive. Only a few congeners are provided with transverse undulations or ridges (see Table 9 for comparison), but in none their development reaches the extent met with in S. acutustriatus sp. nov.

The internal, submarginal cusps are variably present among the hydrothecae belonging to the same stem (e.g., MNHN-IK-2015-460), and are even absent in stems of some colonies (e.g., MNHN-IK-2015-446). Only a few congeners have been shown to possess such structures, and their main distinguishing features are summarized in Table 10 .

The systematic position of this species is discussed in the ‘Molecular study’ section.

Distribution

Only known from off New Caledonia (present study).

Figures

Fig. 15. Dictyocladium reticulatim (Kirchenpauer, 1884). A–C. Colony fragment (A), hydrotheca (B), gonotheca (C), all from sample MNHN-IK-2015-405. Scale bars: A = 1 mm; B = 200 µm; C = 500 µm.

Fig. 20 (opposite page). 16S maximum likelihood phylogenetic tree of selected Leptothecata species obtained with PhyML(GTR+G+I model) and based on 622 aligned basepair positions of the mitochondrial 16S gene. Node-support values are bootstrap values of 100 pseudoreplicates (shown only if> 70%). Species treated in this study are in bold. Some family clades with sufficient bootstrap support discussed in the present study are highlighted in blue boxes. N.B.: Two species names were not used as given in GenBank (FJFJ550462 and FN424141), and the reasons are given in the Material and methods section.

Fig. 16. A.? Symplectoscyphus acutustriatus Galea, sp. nov., holotype colony, MNHN- IK-2015-460. — B.? Symplectoscyphus elongatulus Galea, sp. nov., holotype colony, MNHN- IK-2015-463. — C. Symplectoscyphus paulensis Stechow, 1923, colonies from sample MNHN- IK-2015-393. — D. Symplectoscyphus cf. tropicus (Hartlaub, 1901), colony from sample MNHN-IK-2015-394. — E. Tuberocaulus scorpioides (Vervoort, 1993) gen. et comb. nov., colony from sample MNHN-IK-2015-400. — F–G. Zygophylax niger Galea, sp. nov., holotype colony (F) and detail of its coppinia (G) from sample MNHN-IK-2015-478. Scale bars: A, G = 5 mm; B–E = 1 cm; F = 2 cm.

Fig. 17. A–E.? Symplectoscyphus acutustriatus Galea, sp. nov., portion of stem with side branch (A, from sample MNHN-IK-2015-460); hydrothecae without (B) and with (C) internal, submarginal cusps, aperture in apical view (D), portion of colony with gonotheca (E), all from sample MNHN- IK-2015-461. — F–G. Symplectoscyphus commensalis Vervoort, 1993, portion of colony with internodes and hydrothecae (F), gonotheca(G), both from sampleMNHN-IK-2015-399.— H–J.? Symplectoscyphus elongatulus Galea, sp. nov., portion of stem with proximal part of cladium (H), hydrotheca (I), apical view of aperture showing submarginal, intrathecal cusps (J), all from sample MNHN-IK-2015-463. — K–M. Symplectoscyphus paulensis Stechow, 1923, colony fragment (K), hydrotheca (L), gonotheca (M), all from sample MNHN-IK-2015-393. — N–O. Symplectoscyphus cf. tropicus (Hartlaub, 1901), portion of colony (N), hydrotheca (O), both from sample MNHN-IK-2015-394. Scale bars: A, H, K, N = 1 mm; B–C, E–G, I, L–M, O = 500 µm; D, J = 100 µm.