Porella compressa Revised 1805
Creators: name: Souto, J.
name: Reverter-Gil, O.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Bryozoa
Gymnolaemata
Cheilostomata
Bryocryptellidae
Porella
Porella compressa

description: Porella compressa (J. Sowerby, 1805)
(Figs 3, 29–44; Table 4)
Millepora compressa J. Sowerby, 1805: 83, pl. 41.
Smittia grimaldii Jullien in Jullien & Calvet 1903: 99, pl. 11, fig. 1.
Smittia decipiens Jullien in Jullien & Calvet, 1903: 101, 149, pl. 12, fig. 5. Smittia fallax Jullien in Jullien & Calvet, 1903: 102, pl. 12, fig. 6.
Smittia immersa Jullien in Jullien & Calvet, 1903: 105, pl. 13, fig. 6.
Smittina immersa: Reverter-Gil & Fernández-Pulpeiro, 2001: 110.
Porella compressa: Reverter-Gil & Fernández-Pulpeiro, 1998: 46, fig. 2; Hayward & Ryland, 1999: 158, figs 55, 57C, D.
Material examined. Lectotype of Smittia decipiens (designated here): MNHN 3924, Hirondelle st. 53, 43.74722’N, 05.86278°W, 135 m depth, Bay of Biscay, Calvet Coll.
Additional material examined: MNHN 3934, Hirondelle st. 60, 43.95000°N, 07.11278°W, 300 m depth, Bay of Biscay, Calvet Coll. as Smittia decipiens.
Lectotype of Smittia fallax (designated here): MOM 420222: Hirondelle st. 58, 43.66667°N, 06.57944°W, 134 m depth, Bay of Biscay, Calvet Coll.
Paralectotypes of Smittia fallax (designated here): MOM 420124: Hirondelle st. 53, 43.74722°N, 05.86278°W, 135 m depth, Bay of Biscay, Calvet Coll. MOM 420149: Hirondelle st. 56, 43.64167°N, 06.13778°W, 90 m depth, Bay of Biscay, Calvet Coll. MOM 420240: Hirondelle st. 59, 43.88333°N, 06.67944°W, 248 m depth, Bay of Biscay, Calvet Coll. MOM 420255: Hirondelle st. 60, 43.95000°N, 07.11278°W, 300 m depth, Bay of Biscay, Calvet Coll.
Holotype (by monotypy) of Smittia grimaldii: MNHN 5966, Hirondelle st. 85, 46.51667°N, 04.52944°W, 180 m depth, Bay of Biscay, Calvet Coll.
Lectotype of Smittia immersa (designated here): MNHN 3907, Hirondelle st. 60, 43.95000°N, 07.11278°W, 300 m depth, Bay of Biscay, Calvet Coll.
Paralectotype of Smittia immersa (designated here): MOM 420256, Hirondelle st. 60, 43.95000°N, 07.11278°W, 300 m depth, Bay of Biscay, Calvet Coll.
Additional material: MHNUSC-Bry 317: Doniños, 43.50105°N, 08.35002°W, 44 m depth. MHNUSC-Bry 539: Malpica, 43.42528°N, 08.82361°W, 119 m depth, 16/11/2001. MHNUSC-Bry 545: Malpica, 43.39667°N, 09.18139°W, 186 m depth, 02/11/2003. MHNUSC-Bry 540: Corme, 43.31083°N, 09.03083°W, 100 m depth, 31/ 12/2002. MHNUSC-Bry 541, 542: Laxe, 43.29139°N, 09.20667°W, 143 m depth, 06/11/2004. MHNUSC-Bry 543: Camariñas, 43.20139°N, 09.32167°W, 148 m depth, 18/02/2002. MHNUSC-Bry 547: Ría Muros, Porto do Son, 42.72194°N, 09.03500°W, 16 m depth, 08/03/2002. MHNUSC-Bry 546: Ría Muros, 42.68528°N, 09.10306°W, 44 m depth, 22/03/2002. MHNUSC-Bry 548: A Guarda, 41.98472°N, 08.95056°W, 69 m depth, 21/03/2005.
SD, standard deviation; N, number of measurements.
Additional localities studied (specimens not stored): O Barqueiro, 43.69806°N, 07.39083°W, 68 m depth, 13/ 12/2002. A Coruña, 43.54167°N, 08.43722°W, 94 m depth, 10/01/03. A Coruña, 43.43139°N, 08.40750°W, 63 m depth, 02/03/2002. A Coruña, 43.41056°N, 08.51528°W, 85 m depth, 15/05/2002. Malpica, 43.35222°N, 08.83778°W, 23 m depth, 02/06/2002. Laxe, 43.36639°N, 09.32778°W, 223 m depth, 29/01/2002. Laxe, 43.34389°N, 09.09611°W, 127 m depth, 30/01/2005. Laxe, 43.39944°N, 09.18833°W, 190 m depth, 18/09/2005. Camelle, fragments, 43.28194°N, 09.14333°W, 95 m depth, 14/01/2003. Camelle, several dead fragments, 43.21417°N, 09.11500°W, 35 m depth, 05/05/2004. Fisterra, one small colony, 42.84778°N, 09.39750°W, 152 m depth, 08/12/2002. A Guarda, 41.90833°N, 08.97667°W, 85 m depth, 04/02/2005.
Description. Colony erect, about 5–10 cm high, orange, with a thickly calcified encrusting base, irregularly branching, becoming thinner toward the growing margin (Figs 29, 42). Branches bilaminar, initially flat, but becoming irregularly rounded in later ontogeny. Autozooids rectangular to hexagonal, initially in regular series, but then irregularly arranged when frontal budding occurs in older parts of the colony (Fig. 44). Frontal shield slightly convex, with few frontal pores and large marginal pores; rapid thickening from secondary calcification does not substantially change its aspect. Primary orifice approximately as long as wide, with distal margin semicircular and proximal margin straight with a broad, low lyrula, occupying up to three-quarters of the proximal margin; condyles rounded, not well developed (Figs 31–35). Avicularium suboral, immediately proximal to the lyrula, oriented slightly sloping or almost perpendicular to the plane of the orifice, proximally directed (Figs 31–35). Rostrum semicircular, sometimes with a very small denticulation (Figs 32, 35, 39); crossbar complete, leaving a small oval proximal opesia. The secondary calcification soon conceals avicularium and the primary orifice with a deep peristome. Secondary orifice circular with a thin raised rim bordered by a narrow groove inside the peristome (Fig. 30). Whenever new zooids bud frontally and secondary calcification increases, different layers of zooids are formed, adapting the longitude of the peristome to the position of the zooid in the different layers, been more elongated in zooids with more internal position (Figs 40, 41). Vicarious spatulate avicularium sometimes present, positioned mainly in branching points; rostrum rounded and lightly cupped distally, crossbar complete with a small but robust columella (Figs 36–38). Ovicell globular, wider that long, imperforate and visible only in early ontogeny, soon completely immersed (Figs 42, 43).
Remarks. Porella compressa is regarded as a Boreal-Arctic species (Hayward & Ryland 1999), although distributed from the Faroe Islands to southwest of the Iberian Peninsula (Reverter-Gil et al. 2014). We have revised material of this species collected NW of the Iberian Peninsula between 16 and 300 m depth.
On the other hand, Smittia decipiens, S. fallax and S. immersa were described by Jullien (in Jullien & Calvet 1903) from material collected by l’Hirondelle in the southern area of the Bay of Biscay, and S. grimaldii from the northern area. Smittia decipiens was collected at st. 53 (two colonies at 135 m depth) and st. 60 (one sample at 300 m depth) (Figs 35, 38, 39). Several fragments of S. fallax were collected at sts 53, 56, 57, 58, 59, 60, between 90 and 300 m depth (Figs 30, 31, 36, 40, 41). Two broken colonies of S. immersa were collected only at st. 60 (300 m depth) (Figs 32, 37). Finally, S. grimaldii was collected only at st. 85 (several fragments at 180 m depth) (Fig. 33). None of the species have been collected again, but S. decipiens was already considered a junior synonym of P. compressa by Reverter-Gil & Fernández-Pulpeiro (1998), and S. immersa was included, as Smittina immersa, in a Galician checklist (Reverter-Gil & Fernández-Pulpeiro 2001). Samples of the four species are now stored at the MNHN and MOM, and lectotypes and paralectotypes are here designated.
The study of all this material proves that these species of Smittia are indistinguishable from P. compressa because they show all the diagnostic features of the species. Moreover, three of these species (S. decipiens, S. fallax, S. immersa) were collected at the same station (st. 60), and it is incomprehensible why Jullien & Calvet (1903) described the material as three different species without discussing the perceived differences. On the other hand, the original description of S. grimaldii (Jullien in Jullien & Calvet 1903, p. 99) is very similar to that of P. compressa (see description above). Nonetheless, the authors merely stated that this species is quite similar to S. fallax, but without further comments. The primary orifices of all the colonies are similar (Figs 31–35, 39; Hayward & Ryland 1999, fig. 55C), as is the suboral avicularium (Figs 31–35, 39; Hayward & Ryland 1999, fig. 55A, B). The secondary orifice shows the same outline (Figs 30, 36, 41; Hayward & Ryland 1999, figs 55D, 57C). All the colonies are erect, with branches initially flat-sectioned, but becoming cylindrical in later ontogeny.
There are, however, some differences. In the type material of S. decipiens and S. immersa the proximal border of the rostrum of the avicularia is finely dentate (Figs 32, 35, 39), a character not seen in the material of the other two species (S. fallax and S. grimaldii) or mentioned in any of the available descriptions of P. compressa. In any case, this feature is not visible using optical microscopy and is rapidly obscured by secondary calcification. In addition, the edge of the avicularia in S. fallax and S. grimaldii is eroded in the material examined, so denticles may be missing. Another difference is the presence of large, spatulate avicularia in material of S. decipiens, S. fallax and S. immersa (Figs 36–38), mainly at the margin of the branches. Such avicularia were not found in material of S. grimaldii, and were not reported in the literature on P. compressa. Their presence, however, seems inconstant and they are very difficult to see owing to the general disorder of the zooids in many parts of the colony. In fact, these avicularia were originally reported by Jullien & Calvet (1903) only in S. immersa, but we have found them in the type material of S. decipiens and S. fallax, as well as in colonies collected in Laxe (NW Spain, MHNUSC-Bry 541). Perhaps these variations are due to environmental or geographical factors or intraspecific variations which, however, are insufficient to define separated species. In summary, there is no single character, or set of characters, that makes it possible to distinguish between the four species described by Jullien & Calvet (1903), or between them and P. compressa. Although new, freshly collected material may allow undertaking future genetic studies, we currently assume that S. decipiens, S. fallax, S. grimaldii and S. immersa are junior subjective synonyms of P. compressa, as was already stated by Reverter-Gil & Fernández-Pulpeiro (1998) for S. decipiens.
The variability in colonial morphology is remarkable and mainly related to secondary calcification, which results in flat to circular-section branches that develop very long peristomes (Figs 39–41). We were unable to observe polypide activity in these zooids from the innermost layers, but nothing indicates that they are nonfunctional. These long tubular structures are therefore probably related to morphological adaptations of the polypide, as for instance a larger development of the introvert, which enables expanding the tentacle crown outside of the peristome. The proximal channel along the peristome no doubt helps with water exchange during the process of polypide extension and retraction.
description: Published as part of Souto, J. & Reverter-Gil, O., 2019, Identity of bryozoan species described by Jullien & Calvet from the Bay of Biscay historically attributed to Smittia, pp. 105-123 in Zootaxa 4545 (1) on pages 115-120, DOI: 10.11646/zootaxa.4545.1.6, http://zenodo.org/record/2618707