Psammogorgia arbuscula (Verrill, 1866)

Breedy, Odalisca & Guzman, Hector M., 2020, A revision of the genus Psammogorgia Verrill, 1868 (Cnidaria, Anthozoa, Octocorallia) in the tropical eastern Pacific Ocean, ZooKeys 961, pp. 1-30 : 1

Psammogorgia arbuscula (Verrill, 1866) Figures 2 , 3 , 4

Echinogorgia arbuscula Verrill, 1866: 329.

Psammogorgia arbuscula Verrill, 1868a: 414; 1868b: 414-415; not Nutting 1909: 719-720; Nutting 1910: 16; Kükenthal 1919: 236-237; Kükenthal 1924: 107; Bayer 1958: 44; Harden 1979: 114-116.

Psammogorgia arbuscula typica Kükenthal, 1924: 107.

Type material.

Lectotype (designated herein). YPM 573, dry, Pearl Islands, Gulf of Panamá, Panamá, F.H. Bradley, 1866-1867, no additional data.

Paralectotypes. YPM 573 a-h; MCZ 425B, MCZ 573 (part of YPM 573), MCZ 727, 728A-B (4916=YPM 1577), MCZ 4017-4019, MCZ 4021-4022, MCZ 4024, MCZ 4998 (=MCZ 728) same data as the lectotype. MCZ 7009, dry, Nicoya Gulf, Costa Rica, collected by pearl divers, J.A. Mc. Neil, 1866-1867, no additional data.

Type locality.

Pearl Islands, Panamá.

Diagnosis.

Colonies bushy, irregularly dichotomous. Stems short, slightly flattened, one to several stems emerging from a common holdfast. Branches and branchlets thin, rounded with long free ends in large colonies. Holdfasts encrusting with a thin layer of coenenchyme often with polyps. Coenenchyme of branches moderately thick and granulose. Coenenchymal sclerites: irregular spindles with acute or bifurcated ends, up to 0.30 mm long; warty and irregular radiates up to 0.13 mm long and some crosses. Calyces prominent and swollen, all around the branches, mostly closely placed in two or three longitudinal rows on each side of the branches. Calyces with thorny and irregular spindles and wart-clubs, up to 0.19 mm long, around the calyx rim. Anthocodial spindles up to 0.26 mm long, in collaret and points arrangements. Sclerites red and orange. Dry colonies red to red-orange, dark red when alive. Polyps bright yellow when alive.

Description.

(see also Verrill 1866, 1868b; Bayer 1956). The lectotype is a bushy, irregularly dichotomous dry colony, 12 cm long and 9.5 cm wide. The colony is of a red orange colour (Fig. 2A, B ). Nine stems arise from an oval encrusting holdfast which is ~ 4.5 cm in diameter (Fig. 2A ). The holdfast is covered by a thin layer of coenenchyme with polyps. Most of the stems are 3.0-3.2 mm in diameter bifurcating a few mm above the base, two of them raising up to 2 cm before subdividing in several branches 2-4 mm in diameter including calyces. The colony branches up to eight times. The branches emerge at angles of 45-90°, ascending parallel and slightly curved at the end. Terminal branchlets are 2.5-10 mm long (Fig. 2A ). The calyces are with rounded somewhat tapered tips. Calyces are closely arranged around the branches, mostly in 2-3 longitudinal rows on each side of the branches; somehow in quincunx (arrangements of five) as Verrill (1868b) mentioned (Fig. 2B ). The calyces are prominent, up to 1 mm tall and around 2 mm diameter, composed of eight marginal swollen lobes around the polyp apertures, which is evident when polyps are withdraw or in dry condition (Fig. 2B ). Calyces present a concentration of thorny, irregular spindles and wart-clubs around the borders. The coenenchyme is moderately thick, granulose and brittle in the dry lectotype. Coenenchymal sclerites are dark red, red, orange and of lighter hues (Fig. 2C ), and of different forms: irregular spindles with acute or bifurcated ends, some being slightly curved (Figs 2C , 3A ), 0.14-0.20 mm long and 0.06-0.07 mm wide. Warty radiates are 0.07-0.13 mm long and 0.065-0.085 mm wide (Fig. 3B ); and some warty crosses up to 0.11 mm by 0.1 mm. Wart-clubs are 0.09-0.18 mm long and 0.049-0.12 mm wide, variable in form and with a larger end expanded and covered with thorny warts (Fig. 3C ). They are concentrated at the calyx rims and the base of the anthocodia. The anthocodial armature is well developed. It is composed of spiny spindles arranged in a collaret and points, 0.13-0.17 mm long (0.20-0.26 mm long according to Verrill (1868b)) and 0.02-0.045 mm wide (Fig. 3D ); its flat spindles are with small tubercles and scattered warts.

Variability.

Most of the type material of the form typica of P. arbuscula is constituted of small colonies 5-15 cm long and 3-7 cm wide or fragments of colonies, the largest specimen being MCZ 7009 (28 cm long and 20 cm wide), with unbranched ends up to 15 cm long. Stems can reach up to 4 mm diameter, branches up to 3.5-3.8 mm in diameter and branchlets up to 2.0-2.6 mm in diameter. The sclerites content is consistent among the types. When alive, the colonies are dark red and the polyps are bright yellow ( Verrill 1868b) (Fig. 4 ).

Distribution.

Tropical eastern Pacific: Panamá, Costa Rica, Ecuador, México and El Salvador.

Remarks and comparison.

The Psammogorgia arbuscula typica is different in calyx structure, size of sclerites and colour from the varieties P. arbuscula var. dowii and P. arbuscula var. pallida (see Tables 1 , 2 ). These other varieties lack the prominent and swollen calyces present in P. arbuscula typica . Psammogorgia gracilis and Psammogorgia hookeri have prominent calyces however, there are many other differences that separate them from P. arbuscula (Tables 1 , 2 ). Psammogorgia gracilis has thinner and longer branchlets as well as shorter spindles, longer wart clubs, and shorter anthocodial sclerites (Tables 1 , 2 ). Psammogorgia hookeri has smaller bushy colonies with a typical coral red colour, different from the larger colonies of P. arbuscula . In general, P. hookeri has star-like sclerites absent in the later, and smaller sclerites than in P. arbuscula .

Bayer (1958) treated specimen MCZ 4022 as the holotype for the species however, Verrill did not designate a holotype. Verrill´s 1866 original description of Echinogorgia arbuscula is general, and he did not describe specimen MCZ 4022 specifically. We consider specimen YPM 573 more representative of the species and designate this as the lectotype to clearly establish the taxonomic status of P. arbuscula .

Figures

Figure 2. Psammogorgia arbuscula (Verrill, 1866) YPM 573 A colony B detail of branches C coenenchymal and anthocodial sclerites.

Figure 3. Psammogorgia arbuscula (Verrill, 1866) YPM 573 A spindles B radiates C wart clubs D anthocodial spindles.

Figure 4. Psammogorgia arbuscula (Verrill, 1866). A In situ colony, 13 m deep, Rocas Corcovado, Osa Peninsula, Costa Rica. Photograph: Manu San Felix, National Geographic Pristine Seas.