Diphasia saharica, Gil & Ramil, 2017

Gil, Marta & Ramil, Fran, 2017, The genus Diphasia L. Agassiz, 1862 (Cnidaria, Hydrozoa) in Northwest Africa, Zootaxa 4363 (3), pp. 301-349 : 322-326

Diphasia saharica n. sp.

( Figs. 10–12 ; Tables 5, 6)

Material examined. Western Sahara. CCLME-1110, stn BT213, 26º15´53"– 26º14´42"N, 14º50´21"– 14º51´30"W, 371– 363 m, 28-XI-2011: one colony, 203 mm high with female gonothecae is the holotype ( MNCN 2.03 /679).

MAROC-0611, stn MO225, 22º43´25"–22º45´24"N, 17º16´13"–17º13´24"W, 698– 604 m, 24-XI-2006: single colony 39 mm high, no gonothecae.

MAROC-0611, stn MO248, 23º26´25"–23º29´26"N, 16º59´21"–16º58´29"W, 239– 232 m, 30-XI-2006: single colony 122 mm high, no gonothecae.

MAROC-0611, stn MO251, 23º56´12"–23º53´31"N, 17º02´15"–17º04´07"W, 1055– 1052 m, 2-XII-2006: single colony 100 mm high, no gonothecae.

CCLME-1110, stn BT202, 25º35´29"–25º36´53"N, 15º47´33"–15º46´43"W, 263–268 m, 21-XI-2011: single colony 135 mm high, with female gonothecae, paratype (CFM-IEOMA-6216).

CCLME-1110, stn BT205, 25º10´01"–25º11´17"N, 14º51´53"–14º52´07"W, 43–45 m, 27-XI-2011: two colonies, 138 and 255 mm high with male gonothecae, one attached to Mesalia opalina , paratypes (MNCN 2.03/ 680; LZM-01419).

CCLME-1110, stn BT208, 25º49´42"– 25º49´04"N, 15º27´28"– 15º29´07"W, 350–355 m, 27-XI-2011: three colonies 104–230 mm high, two colonies with male gonothecae, paratypes (MNHN-IK- 2014-2198; RMNH. COEL.42267; LZM-01975).

Morocco. CCLME-1205, stn BT576, 35º27´39"– 35º29´11"N, 6º24´35"– 6º24´11"W, 136– 132 m, 13-VII-2012: single colony 307 mm high, no gonothecae.

CCLME-1205, stn BT577, 35º24´00"–35º25´32"N, 6º12´07"–6º11´52"W, 79–84 m, 13-VII-2012: single colony 230 mm high, no gonothecae.

CCLME-1205, stn BT580, 35º15´13"–35º12´54"N, 6º45´05"–6º45´01"W, 570–574 m, 14-VII-2012: single colony 240 mm high, no gonothecae.

Additional material. RMNH.COEL.26176, BALGIM expedition, stn DW50, 35º52.7’N, 06º31.9’W, 518–523 m, 03-VI-1984, Diphasia sp.: one slide with a sterile fragment 35 mm high.

LMZ-160, BALGIM expedition, stn DW114, 35º45.5´N, 06º04.2´W, 150 m, 11-VI-1984, Diphasia sp.: one hydrocladium of 15 mm high.

Etymology. The specific name saharica refers to the Sahara coast, where this species was found for the first time.

Biology. Diphasia saharica seems to colonize both soft and hard substrata. Some colonies showed their hydrorhiza modified as a tuft of perisarcal fibers adapted to anchor the colony to sandy or muddy bottoms; however, one colony was found attached to the shell of the prosobranch Mesalia opalina (Adams & Reeve in Reeve 1849) .

Fertile material recorded in November.

Distribution. This species has been recorded in the Western Sahara and Morocco coast between a depth of 43 and 1055 m.

Description. Colonies erect, composed of a monosiphonic and ramified “false axis” resulting from the sympodial growth of the colony. The branches, alternately directed right and left, form a scorpioid sympodium (fig. 10A). Axis and lateral branches generally not segmented, but some isolated transverse nodes were observed in the most distal part of the branches. Both false axis and branches supporting hydrocladia pinnately arranged in the same plane. Between two consecutive hydrocladia, one and two pairs of hydrothecae are alternatively present (fig. 11A), resulting in the separation of three pairs of hydrothecae between two consecutive hydrocladia on the same side. Hydrocladia segmented by straight nodes into internodes provided with a variable number of pairs of hydrothecae.

Hydrothecae tubular, biseriate and placed in opposite or sub-opposite pairs on the false axis, lateral branches and hydrocladia. Adcauline wall 1/2 to 2/3 adnate; free part curved upwards and almost straight or slightly convex. Abcauline wall concave and without internal tooth. Hydrothecal rim smooth with an adcaulinar sinus; aperture tilted towards the abcauline side and closed by an operculum attached to the adcauline sinus (figs. 10B, 11B). Renovations are frequent and numerous, considerably enlarging the free part of the hydrothecae (fig. 12B, D).

Female and male gonothecae borne in separate colonies inserted under hydrothecal bases on a small apophysis and disposed perpendicularly to the hydrocladia. Female gonothecae long, oval and narrowing towards the base; distal half with four longitudinal ribs, each one with two or three blunt spines whose morphology and length could be variable. Additional spines between the ribs can be observed on the top of the gonothecae. Apical part of the gonotheca with a well-developed marsupium communicated with the proximal gonothecal cavity by a circular aperture; two lateral funnels originating from both sides of the marsupium reach the gonothecal wall, forming a pair of lateral openings (fig. 10C–D). The larvae develop inside the marsupium and leave the gonothecae through these holes. In some cases, empty female gonothecae and marsupium showed an apical aperture (fig. 12A). This apical aperture seems to also contribute to the liberation process of the larvae, at least in the older gonothecae. Developing eggs were visible in the basal cavity or inside the marsupium.

Male gonothecae with a narrow base and widening at the distal part, which is quadrangular in the cross-section with four little developed and slightly curved spines, one at each corner and surrounding a central aperture located at the end of a conical elevation. Inside the gonothecae, a mass of developing spermatocytes were observed (fig. 11C–D).

Remarks. Diphasia saharica also belongs to the Diphasia margareta group on the basis of the general morphology of the female gonothecae. Nevertheless, it differs from D. margareta because of the presence of additional spines between the external ridges on the female gonothecae, lower development of the spines in the male gonothecae and the habitus of the colony that forms a scorpioid sympodium. In addition, the hydrothecae of Diphasia saharica n. sp. lacks an internal ledge in the abcauline wall. All these differences approach this species to Diphasia leonisae n. sp., but both species differ clearly on the basis of the morphology of the male gonothecae: laterally compressed and several apical apertures in the first species, and quadrangular cross-section with only one central aperture in the second species.

The morphology of the hydrothecae resembles that of the material described by Ramil & Vervoort (1992) as Diphasia sp. collected off Cape Spartel, northern Morocco. However, in this case, the measurements of the hydrothecae are higher (see Tables 5, 6) and the colonies were sterile, which prevented us from including this material within Diphasia saharica n. sp.

CCLME-1110 CCLME-1110 Stn BT213 Stn BT205 BALGIM BALGIM

Stn DW114 Stn DW50

( Ramil & Vervoort 1992) RMNH.COEL.26176

Figures

FIGURE10. Diphasia saharica n. sp. A–D, stn BT213; A, colony;B, part of hydrocladium; C–D, female gonothecae.Scales: a, 5 cm; b–d, 1 mm.

FIGURE 11. Diphasia saharica n. sp. A–D, stn BT205; A, part of axis with insertions of hydrocladia; B, two pairs of hydrothecae from hydrocladium; C–D, male gonothecae.Scales:a–d, 0.5 mm.

FIGURE 12. Diphasia saharica n. sp. A–B, stn BT202; A, female gonothecae with aperture distal; B, part of hydrocladium. C–D, stn BT580; C, part of hydrocladium; D, part of hydrocladium. Scales:a–d, 0.5 mm.