Therenia cryptooecium, Berning & Tilbrook & Rosso, 2008

Berning, Björn, Tilbrook, Kevin J. & Rosso, Antonietta, 2008, Revision of the north-eastern Atlantic and Mediterranean species of the genera Herentia and Therenia (Bryozoa: Cheilostomata), Journal of Natural History (J. Nat. Hist.) 42 (21 - 22), pp. 1509-1547 : 1528-1533

Therenia cryptooecium new species

( Figure 5 )

Escharina porosa: Cook 1985, p. 165 , Plate 16, Figures E, F.

Differential diagnosis

T. cryptooecium differs from all other species in the extremely dense perforation of its frontal shield and in its ooecium, which is almost completely immersed.

It is furthermore distinguished from T. porosa in its wider sinus and in the thickened rim framing only the distolateral orifice margin in autozooecia ( T. porosa has a narrower and distally raised peristome that completely encircles the orifice).

Besides the differences given above, T. cryptooecium is distinguished from T. rosei n. sp. due to its wider sinus in ovicellate zooecia, and its narrower band of calcification framing the ooecial aperture.

In contrast to T. peristomata n. sp. it has a flat frontal surface, a thickened rim merely framing the distolateral orifice margin, condyles that project medially beyond the shoulders of the sinus, a very narrow band of calcification framing the distolateral ooecial aperture, an avicularium with a much broader and kidneyshaped rostrum, and a crossbar that lacks a columella.

Etymology

For its hidden (Greek: kryptos) ooecium.

Material examined

Holotype: NHM 1972.1.2.16A, off Tema, Ghana, figured by Cook (1985, Plate 16, Figures E, F) . Paratype: NHM 1972.1.2.16B, off Tema , Ghana, 30–40 m. Additional material: NHM 1972.1.2.16pt, off Tema , Ghana, 30–40 m.

Measurements

ZL 620¡63, 548–796 (1, 14); ZW 480¡65, 378–624 (1, 14); OL 136¡9, 119–149 (1, 17); OW 140¡7, 127–152 (1, 17); ApL 157, 155–159 (1, 3); ApW 159, 153–163 (1, 3); AL 142¡13, 115–167 (1, 16); AW 122¡14, 106–147 (1, 16); PD 20¡2, 16–23 (1, 12).

Description

Colony encrusting unilaminar, multiserial. Zooecia rhomboid, hexagonal or polygonal, separated by shallow grooves or a slightly raised suture; frontal wall flat, closely and regularly perforated by numerous small pseudopores, and with few (two to five) large marginal areolar pores, one of these situated directly proximolateral to orifice margin opposite to avicularium. Orifice dimorphic with a deeply immersed shelf along the distolateral margin, proximolaterally framed by a smooth narrow band of gymnocystal calcification; primary orifice about as wide as long and widest just distal to mid-distance, anter three-quarters of a transverse ellipse, proximal border straight, sinus U-shaped with rather square shoulders, occupying about half of proximal margin, two slightly immersed, thick, straight and tapering condyles pointing medially, projecting beyond the shoulders of the sinus and occasionally approaching each other, distolateral orifice border bounded by a raised and curved rim of thick calcification sloping towards orifice; aperture in ovicellate zooecia of similar shape but larger, condyles shorter, not projecting beyond sinus, distolateral margin relatively narrow and flat.

Ooecium completely immersed by distal zooecium, not visible at colony surface.

Avicularium situated directly proximolateral to orifice on either left or right side, in distal pseudoporous chamber, which is level with, and often not clearly demarcated from, frontal shield of zooecium apart from one or two areolar pores at lateral and/or proximolateral margin; rostrum a suborbicular to kidney-shaped, broad, sloping band, laterally or distolaterally oriented; crossbar complete, without columella, thick, extending fairly deep into cystid, square-edged and twisted along its axis; proximal opesium bounded by an immersed convex shelf of calcification extending towards crossbar from proximal rostrum margin.

An ancestrula or early astogenetic stages of colony growth were not observed.

Remarks

The type material of T. cryptooecium is from Ghana and was described and figured by Cook (1985, p. 165, Plate 16, Figures E, F). Whether any or all of the material reported as T. porosa by Cook (1968, p. 195) from Guinea and the Canary Islands is conspecific with T. cryptooecium or the other species introduced here cannot be proven at present because the respective material is housed in different collections, which could not be studied during this project.

Cook (1985, p. 166) frequently observed T. cryptooecium to encrust the agglutinating larger foraminifer Jullienella foetida Schlumberger , occasionally reaching a colony size of over 1000 zooids. The depth of occurrence off Ghana ranged between 10 and 51 m.

Therenia rosei new species

( Figure 6 )

Escharina porosa: Hayward 1974, p. 377 , Figure 4A, B ; Rosso 1996a, Plate 4, Figure f.

Differential diagnosis

T. rosei is distinguished from T. porosa owing to its larger pores in the frontal wall, a wider sinus with rounded shoulders, the presence of a thickened rim framing the distolateral orifice margin, and in a broader area of exposed ooecium.

Differences to T. cryptooecium are found in the less densely perforated frontal wall, in a narrower sinus with rounded shoulders, in crenellated condyles, and in the broad area of exposed ooecium.

In contrast to T. peristomata , T. rosei has a more densely perforated frontal wall, a thick rim framing the distolateral orifice margin, a distinctly larger aperture and primary orifice with condyles extending beyond the shoulders of the sinus, as well as larger avicularia with a more extensive immersed shelf in the proximal opesium and a crossbar lacking the columella.

Etymology

Named in honour of Doris and Hans Rose, the first author’s aunt and uncle.

Material examined

Holotype: NHM 1975.1.12.17A, Chios, Aegean Sea, figured by Hayward (1974, Figure 4A, B ). Paratype: NHM 1975.1.12.17B, Chios, Aegean Sea. Other material: PMC. R.I.H.B-4, Gulf of Noto , Ionian Sea .

Measurements

ZL 681¡47, 588–716 (2, 6); ZW 520¡75, 404–641 (2, 6); OL 154¡10, 133–167 (2, 9); OW 163¡10, 145–175 (2, 9); ApL 157¡5, 151–164 (1, 4); ApW 182¡9, 173–193

(1, 4); OvL 197¡17, 171–208 (1, 4); OvW 326¡40, 282–374 (1, 4); AL 175¡15, 141– 192 (2, 12); AW 136¡11, 122–157 (2, 12); PD 10¡1, 9–13 (2, 12).

Description

Colony encrusting unilaminar, multiserial. Zooecia rhomboid, hexagonal or polygonal, separated by distinct grooves; frontal wall flat, closely and regularly perforated by numerous small pseudopores, and with few, relatively large, marginal areolar pores (usually two or three, rarely more than five); lateral walls with some 10 relatively small, distolateral communication pores. Orifice very slightly dimorphic with a deeply immersed shelf along the distolateral margin, proximolaterally framed by a smooth narrow band of gymnocystal calcification; primary orifice in autozooecia about as broad as long and widest in distal third, anter three-quarters of a transverse ellipse, proximal border straight, sinus U-shaped with rounded shoulders, occupying about one-third of proximal margin, condyles slightly immersed, strong, crenellated, more or less straight with rounded ends pointing medially and projecting above shoulders of sinus, the flattened frontal faces sloping proximally towards a distinct edge parallel to proximal orifice margin, distolateral orifice border bounded by a slightly raised and curved rim of thick calcification sloping towards orifice; aperture in ovicellate zooecia of similar shape and length but slightly wider; condyles slightly ribbed, not as broad as in autozooecia and ends not projecting beyond shoulders of sinus.

Ooecium initially hemispherical, later for the most part immersed, exposed frontal area a crescentic, broad, flat band of smooth calcification slightly oblique to colony surface.

Avicularium situated directly proximolateral to orifice on either left or right side, in distal pseudoporous cystid, which is level with and not clearly demarcated from frontal shield of zooecium, one or two areolar pores at lateral or proximolateral margin; rostrum oval to kidney-shaped, broad, sloping band, laterally or distolaterally oriented; crossbar complete, without columella, thick and extending fairly deep into cystid, square-edged and twisted along its axis, proximal opesium bounded by an immersed, broad and slightly convex shelf of calcification extending towards crossbar from proximal rostrum margin.

An ancestrula or early astogenetic stages of colony growth were not observed.

Remarks

This species was reported as E. porosa by Hayward (1974) and Rosso (1996a) from the eastern and central Mediterranean Sea, respectively. It is possible that T. rosei also occurs in the western Mediterranean and the Canary Islands. While Zabala and Maluquer (1988, p. 129, Figure 291; Plate 15, Figure D) record this morphotype from off Spain, Cook (1968, p. 195), Arístegui Ruiz (1984, p. 294, Figure 62a–c; Plate 20, Figures 6–8 , 1987), and Arístegui and Cruz (1986, p. 166) report E. porosa from the Canaries. Especially Arístegui Ruiz’ (1984) figured specimens are very closely related, if not identical, to T. rosei . However, more SEM work is needed to enable a precise determination of these specimens. The same applies to the Mediterranean fossil H. montenati Pouyet, 1976 , which is also morphologically closely related to the recent species.

T. rosei was reported off the Greek island of Chios from 1 to 60 m depth by Hayward (1974). Rosso (1996a) found a single living specimen at 33 m and few dead colony fragments between 31 to 130 m depth off south-eastern Sicily. It encrusts rocks and calcareous substrata such as shells and coralline algae.

Figures

Figure 4. Herentia thalassae David and Pouyet, 1978. MNHN 7619, off NW Spain; note that the vertical component in these perpendicular views is greatly understated, the distal parts of the zooecia and ooecia are distinctly raised. (A) General aspect of colony; (B) close-up of ovicellate zooecium; (C) close-up of autozooecium. Scale bars: 400 mm (A); 100 mm (B, C).

Figure 5. Therenia cryptooecium n. sp. Holotype, NHM 1972.1.2.16A, Ghana, off Tema. (A) General aspect of colony; note the presence of three ovicellate zooecia (arrows); (B) autozooecia at the colony margin; note differences in condyle length between orifices; (C) close-up of autozooecium orifice and avicularium; (D) close-up of ovicellate zooecium, which is characterized by a slightly larger aperture and shorter condyles. Scale bars: 200 mm (A); 100 mm (B, D); 50 mm (C).

Figure 6. Therenia rosei n. sp. Holotype, NHM 1975.1.12.17A, Aegean Sea. (A) Autozooecia; (B) ovicellate zooecia; (C) close-up of autozooecium orifice and avicularium; (D) close-up of ovicellate zooecium; note difference in condyle morphology compared to orifice of autozooecium. Scale bars: 200 mm (A, B); 50 mm (C, D).