Plumularia conjuncta Billard, 1913

Agís, José Ansín, Ramil, Fran & Calder, Dale R., 2016, One new genus and three new species of plumulariid hydroids (Cnidaria, Hydrozoa, Plumulariidae) from the western Pacific Ocean, with a re-examination of Plumularia insignis Allman, 1883 and related taxa, Zootaxa 4169 (1), pp. 57-86 : 83

Plumularia conjuncta Billard, 1913

( Fig. 15 ; Table 8)

Plumularia insignis var. conjuncta Billard, 1913: 49 , figs. 42‒43; Bedot, 1921: 28; Van Praët, 1979: 925.

Material examined. Plumularia insignis var. conjuncta , Holotype, ZMA. COEL.P.4051, Siboga Expedition St. 95. Sulu Islands, 5º43.5’ N, 119º40’E, 522 m, 26-06-1899: fragment 5 mm high, without gonothecae.

Schizoholotype , MNHN-IK-2012-16033, Siboga Expedition St. 95. Sulu Islands, 5º43.5’ N, 119º40’E, 522 m, 26-06-1899, one slide: L.1284, fragment of holotype, 1.5 mm long, with one hydrocladium and a detached hydrocladium; without gonothecae [reported as “ paratype ” by van Praët (1979): 925].

Distribution. The species is known only from the type locality, in the Sulu Islands, Indonesia, at a depth of 522 m.

Description. The holotype consists of a 5 mm fragment deposited in the Naturalis Biodiversity Center, Leiden (alcohol); the schizoholotype slide at the MNHN is a small piece of the same axis, with two hydrocladia.

Fragment of main axis or branch, probably apical, not divided into internodes, with eight apophyses directed alternately left and right in same plane; one nematotheca between two consecutive apophyses. Apophyses with two axillary nematothecae and with one well-developed mamelon on upper part. Hydrocladia with proximalmost internode ahydrothecate, with one nematotheca on basal part, borne on a small elevation. Remainder of hydrocladium composed mostly of hydrothecate internodes separated by oblique nodes; intermediate ahydrothecate internodes infrequent, on distalmost part of hydrocladium (last internodes). Hydrothecate internodes each with one hydrotheca and four nematothecae: one mesial inferior, two laterals and one unpaired distal. Hydrotheca tubular, adcauline wall fully adnate with slightly concave distal half, abcauline wall slightly sinuous, rim smooth, slightly tilted towards abcauline wall. Mesial inferior nematotheca on a small elevation, not reaching base of hydrotheca. Lateral nematothecae on a small apophysis, arising below hydrothecal margin. Distal unpaired nematotheca on an elevation, not reaching basal node of next hydrothecal internode. On distalmost part of hydrocladium, distal nematotheca sometimes appearing separate on a poorly differentiated ahydrothecate internode. All nematothecae bithalamic, movable. Basal internodes with 10‒12 annular thickenings: three basal, three to five behind and four distal to hydrotheca; distal internodes with three perisarcal rings in hydrothecate and two in ahydrothecate internodes.

Remarks. The holotype of Plumularia insignis var. conjuncta Billard, 1913 ; a small, sterile fragment only 5 mm long, is inadequate for accurate characterization of colony morphology and for determining how the colony might have been ramified. Nevertheless, differences are evident in its trophosome, mainly in hydrothecal morphology, which unmistakably distinguish Billard’s material from Plumularia insignis Allman, 1883 . We therefore recognize it as a distinct species, under the binomen Plumularia conjuncta Billard, 1913 .

ZMA. COEL.4051

First hydrocladial internode, length 150‒160 Hydrothecate and ahydrothecate internode, length 630‒710 Hydrothecate internode, length 530‒600 Ahydrothecate internode, length 140‒160 Diameter at node 50‒70 Hydrotheca

Abcauline wall, length 210‒250 Adcauline wall, length 240‒280 Diameter at rim 105‒110 Mesial nematotheca, length 70‒80 Diameter at rim 30‒40 Lateral nematotheca, length 85‒90 Diameter at rim 30‒40

Figures

FIGURE 15. Plumularia conjuncta Billard, 1913. Holotype of Plumularia insignis var. conjuncta Billard, 1913; A: fragment of axis with an apophysis and the first two internodes of a hydrocladium. B: detail of a hydrothecate internode from the middle of a hydrocladium. C: detail of distal part of a hydrocladium with a hydrothecate and an ahydrothecate internode. Scales a ‒ e: 0.1 mm.