Pseudoplumaria marocana ( Billard, 1930 )

Altuna, Álvaro, 2012, New records of bathyal Leptolida (Cnidaria: Hydrozoa: Leptothecata) from the Bay of Biscay and the northwestern Iberian Peninsula (northeastern Atlantic), Zootaxa 3565, pp. 1-17 : 9-11

Pseudoplumaria marocana ( Billard, 1930)

(fig. 4A–D, table 4)

Plumularia marocana Billard, 1930: 79 , fig. 1.— Patriti, 1970: 54, fig. 76.—Van Präet, 1979: 926, fig. 99.— Ramil & Vervoort, 1992a: 186, fig. 48b–d, 49a–b.

Polyplumaria flabellata: Gili et al. 1989 (pro parte): 91, fig. 19.

Pseudoplumaria marocana: Ramil & Vervoort, 1992b: 491 , fig. 3.— Medel & Vervoort, 1995: 63, fig. 27–28.— Ramil et al. 1998b: 38.— Ansín Agís et al. 2001: 253, fig. 95.— Bouillon et al. 2004: 148, fig. 79M–P.— Bouillon et al. 2006: 324, fig. 152H.— Altuna, 2010: 24.

Material examined. DEMERSALES 2009, 0 1.10.2009, station L42, 44.0719ºN – 08.5766ºW, 711 m, one large colony and a ramified fragment 8.5 cm long. No gonosome.

Description. Colony 20.0 cm high and 18.5 cm wide, deep brown, stiffly erect, pinnate, formed by a wide and conical hydrorhizal mass 2.5 cm high with numerous fibres adhering to the substrate, that supports a polysiphonic stem; stem rigid, thick, 17.5 cm high and 2.4 mm wide proximally. Ramification profuse, up to the fourth order. Branches stiff, opposite, long, polysiphonic for most of their length, tapering distally. Main tube on front of stem and branches, divided into internodes of variable length by more or less clear straight nodes. Accessory tubules parallel, with numerous bithalamic nematothecae. Internodes with 1–6 short apophyses directed left and right, and scarce nematothecae, one of them normally close to the basal node. Apophyses with an apparent conical mamelon (185–210 µm wide, 135–164 µm high) on its upper side, and two small lateral bithalamic nematothecae.

Hydrocladia abundant all over colony, given off at acute angles from apophyses of main tube, and slightly curved towards abcauline side. First internode athecate, with a straight proximal node and another oblique distal, and one bithalamic nematotheca poorly developed on its lower third. Rest of hydrocladium formed by a succession of thecate internodes with oblique nodes. Thecate internodes with one hydrotheca in the lower two-thirds, and four nematothecae.

Hydrothecae thin walled, deep, adnate for one-third of their adcauline side, with parallel to slightly divergent walls; rim even, slightly everted. Aperture circular, oblique to internodal length axis. Nematothecae bithalamic or reduced; one mesial inferior bithalamic and immovable; another small, axillary, reduced and scale-like. The remaining two are symmetric lateral, bithalamic, moveable and occur on short apophyses.

Gonosome not seen.

Remarks. The genus Pseudoplumaria Ramil & Vervoort, 1992b comprises two species, P. m a ro c a n a and P. sabinae Ramil & Vervoort, 1992b . For some authors, these species belong to the family Plumulariidae due to their reduction of the hydrothecae ( Schuchert 1997: 7); for others, they should be included in the family Halopterididae together with Polyplumaria G. O. Sars, 1874 ( Calder 1997; Bouillon et al. 2006), a point of view that has been followed herein.

The mamelon on the upper surface of the apophyses is very apparent (fig. 4C), and has been considered an atrophied hydrotheca ( Billard 1930; Van Präet 1979). This structure is identical to the one depicted by Bedot (1921, pl. 1, fig. 10–11) in Polyplumaria billardi var. deloni, Bedot, 1921 , a variety known from Morocco that could be a synonym of Pseudoplumaria marocana as suggested by Ansín Agís et al. (2001).

The colony examined is large and similar to the largest colonies known so far, with up to fourth order branching. Van Präet (1979) mentioned colonies up to 22 cm high in material studied by Billard (1930) from Morocco, the same size quoted by Medel & Vervoort (1995) in material from the Strait of Gibraltar. The colonies have a characteristic morphology due to their abundant ramification, long branches, and densely disposed hydrocladia. However, the species can be confused at first sight with Polyplumaria flabellata G. O. Sars, 1874 , a common hydroid in the southern sector of the bay of Biscay.

Billard (1930), Ramil & Vervoort (1992a), and Ansín Agís et al. (2001) report two nematothecae on the hydrocladial apophyses. Medel & Vervoort (1995) mention three surrounding the mamelon, one of them being hard to see. The material examined has only two.

Gonosome described by Ramil & Vervoort (1992b).

Distribution. Pseudoplumaria marocana is an uncommon hydroid with the type locality at 32º33’N – 09º33’W (see Billard 1930, 110 m) and a distribution that was revised by Ansín Agís et al. (2001). There are records from Guinea Bissau ( Gili et al., 1989 as Polyplumaria flabellata in part) to a station south-west of Cape San Vicente in southern Portugal ( Ramil & Vervoort 1992a), including the Strait of Gibraltar ( Medel & Vervoort 1995), Ampére Bank ( Ramil & Vervoort 1992b; Ramil et al. 1998), off Morocco where it seems to be locally common ( Billard 1930; Ramil & Vervoort 1992a, 1992b), and off Mauritania ( Ansín Agís et al. 2001). Its presence in the north of Spain extends its distribution considerably, being also the northernmost record for the species.

Pseudoplumaria marocana is eurybathic, and inhabits a bathymetric range from 27 m ( Medel & Vervoort 1995, Strait of Gibraltar) to 1378 m ( Ramil & Vervoort 1992a, b). The present record is from 711 m depth. This wide range demonstrates a high tolerance to changes in environmental factors.