Exechonella harmelini, Cáceres-Chamizo & Sanner & Tilbrook & Ostrovsky, 2017

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 35-38

Exechonella harmelini n. sp.

( Fig. 14 , Table 13)

Exechonella antillea: Hayward 1974 , p. 377, fig. 4c.

Exechonella cf. antillea: Harmelin et al. 2016 , pp. 422, 424, fig. 4c. Exechonella antillea: Sokolover et al. 2016 , p. 448, fig. 8.

Material examined. Holotype: DPUV 2016-0002-0001, Mediterranean Sea , Lebanon, Selaata , depth 21 m, cave, 14 September 2002 (mounted on SEM stub, uncoated). Paratypes: DPUV 2016-0002-0002, Mediterranean Sea , Lebanon, Selaata , depth 21 m, cave, 14 September 2002 (mounted on SEM stub, uncoated). Three fragments on the same SEM stub: DPUV 2016-0002-0003 (two fragments of the same colony, on coral with barnacle), DPUV 2016- 0002-0004 , Mediterranean Sea , Lebanon, Tripoli, Ramkine Island, depth 13 m, 22 October 1999 ; DPUV 2016- 0002-0005, Mediterranean Sea , Lebanon, Tripoli , Ramkine Island , cave, depth 5–7 m, 31 May 2000 (mounted on SEM stub, uncoated). Other material examined: IPUW 7537 , four colonies, on polychaete tubes and coralline algae. Mediterranean Sea, Lebanon, Selaata, depth 32–35 m, overhang-drop off, 24 September 2002 ; IPUW 7538, eight fragments, on coralline algae. Mediterranean Sea , Lebanon. Turkey Kas, Canyon Cave, depth 18 m, 27 September 2004 ; IPUW 7539, two fragments (one growing on bryozoan colony). Mediterranean Sea , Lebanon, Tripoli, Ramkine Island, depth 13 m, 22 October 1999 ; IPUW 7540, one colony (on barnacle) and three fragments. Mediterranean Sea , Lebanon, Tripoli , Ramkine Island , cave, depth 13 m, 31 May 2000: IPUW 7541 , seven fragments, detached and on polychaete tubes. Mediterranean Sea , Lebanon, Selaata, depth 21 m, cave, 14 September 2002 ; IPUW 7542, two colonies, on bivalve shell. Mediterranean Sea , Lebanon, Selaata, depth 21 m, cave, 14 September 2002 .

Etymology. Named after Dr. Jean-Georges Harmelin who collected this species.

Description. Colony encrusting, unilaminar, multiserial. Those living on small substrata can form whorls (both, clock- and anticlockwise) resulting in 2–3-layered colonies. Autozooids hexagonal or oval in shape, flat, separated by well-defined narrow grooves. Narrow marginal rim is seen between zooids. Primary orifice wide, pear-shaped, longer than wide, poster (one-third) smaller than the anter (two-thirds), rounded or, occasionally, tending to be more quadrate. Anter of rounded outline with an inner lamina which ends at well-defined triangular condyles, their tips directed to the orifice midline, usually extending beyond the edge a step-like curved area beneath. In some zooids the condyles flattened or swollen. A low, smooth, thick-walled peristome, most prominent laterally, slightly longer than wide, oval or with parallel lateral sides. Proximal part is wider than its distal part or has about the same width, but it is narrower in some zooids. Its medial area smooth, but wrinkled either side. Small central blunt projection was observed in many instances. Frontal shield smooth, perforated by 44–67 wellseparated rounded or oval foramina, each with a wide smooth (often wrinkled) gymnocystal rim, raised slightly above the frontal shield and sloping towards the small central opening; fusions between the rims of 2–5 foramina are common. Small marginal pores are predominantly oval and well-seen around the zooid. Lateral avicularia are present on the outer raised rim of the two lateralmost foramina. Each avicularium has a central nipple-like structure with a central pore. A thin round mandible closes the lumen of the foramen. Adventitious kenozooids with 2–5 pores, each with centrally perforated cuticular plate. At least some kenozooids associated with avicularia. Vertical zooidal walls wide, represented by multiporous mural septula with 2–3 rows of communication pores. Ancestrula autozooidal.

Lebanon, Mediterranean Sea

m±sd r n AzL 980±99.2 872–1246 17 AzW 682±70 593–845 17 OrL 273±19.7 247–308 15 OrW 261±12.0 240–285 15 FoN 55±8.3 44–67 17 FoD 60±12 41–84 36 OD 16± 4 8–27 36 Remarks. Hayward (1974) described and illustrated this species (as Exechonella antillea ) from Chios, Aegean Sea. His figure 4c shows a specimen, having a wide peristome and more rounded orifice. Recently, Harmelin et al. (2016, fig. 4c) published the SEM photo of Exechonella specimen (as E. cf. antillea ) from the Lebanese coast that is strongly reminiscent the specimen from Chios. Finally, we obtained several SEM photos of two colonies of the same appearance from the Israeli coast (courtesy of Dr. N. Sokolover, Tel Aviv University). One of these colonies having ancestrula was recently illustrated (as E. antillea ) ( Sokolover et al. 2016, fig. 8). It should be also noticed that foraminal ridges cover almost entire frontal surface in three left zooids (as if they would fuse, while tiny furrows still separate them) in the illustrated colony from Israel thus making an appearance of the frontal shield quite unusual. Most zooids have typical appearance, however.

Mediterranean E. harmelini n. sp. belongs to E. antillea species-complex and its closest relative is E. pumicosa from the Caribbean Sea. Both species have similar number of foramina in a frontal shield, but in E. pumicosa rims of most foramina fuse forming ‘chains’ of 2–8, while in E. harmelini n. sp. the fusion of 2–3, in some case 5 rims were recorded. Mediterranean specimens have bigger zooidal size (980×682 µm) than colonies from Florida (798×635 µm). Also in six colonies of E. harmelini n. sp. the characteristic astogenetic pattern has been recorded resulting in the formation of “whorls” on the surface resulting in multilayered colonies.

Finally, in three studied colonies of E. pumicosa no avicularia were found. While this character can not be used as a reliable (see above), and all other species of E. antillea species-complex have these polymorphs, we decided to mention it. Noteworthy, Hayward (1974) described and figured small rounded avicularia with a central cross-bar in this species. The latter is a misinterpretation of the presence of two closely situated openings, one of the nipple-like structure and the other of the avicularium-bearing foramen.

Distribution. The present species is known from Chios, Aegean Sea, and coasts of Lebanon and Israel, east Mediterranean.

Figures

FIGURE 14. Exechonella harmelini n. sp. Mediterranean Sea, Lebanon (A, C, D, F: holotype DPUV 2016 - 0002 - 0001, noncleaned; B, paratype DPUV 2016 - 0002 - 0002, non-cleaned; E, G, H, paratype DPUV 2016 - 0002 - 0005). A, B, general view of holotype and paratype from above. ‘ Spiral’ pattern of zooidal budding is clearly visible. C, general view of the central part of non-cleaned holotype from above. D, E, close-up of autozooids with avicularia associated with lateralmost foramina (some shown by arrows). F, H, close-up of autozooid showing details of primary orifice and variability of its shape. Kenozooids (k) with pores having centrally perforated cuticular plate are visible in H. G, details of the frontal shields of two neighbour zooids showing lateralmost foramina (one with two openings) with avicularia (arrowheads). Scale bars: A, B = 2 mm; C = 1 mm; D, E = 500 µm; F, G = 200 µm; H = 300 µm.