Escharina alderi ( Busk, 1856 )

Reverter-Gil, Oscar & Souto, Javier, 2015, Redescription of some species of Bryozoa described by J. Jullien and L. Calvet in the NE Atlantic, European Journal of Taxonomy 157, pp. 1-17 : 7-11

Escharina alderi ( Busk, 1856)

Figs 4 A–E, 5A–E; Table 2

Alysidota alderi Busk, 1856: 311 , pl. 9, figs 6–7.

? Lepralia barleei Busk, 1860: 143 , pl. 26, figs 1–2.

Schizoporella ovum Jullien, 1882: 16 , pl. 15, figs 36–37.

Schizoporella alderi – Hincks 1880: 243, pl. 36, figs 9, 9a, 10.

Schizoporella ovum – Jullien 1883: 512, pl. 15, figs 36–37. — Calvet 1907: 422.

Escharina alderi – Hayward & Ryland 1999: 228, figs 94c–d; 96.

Schizomavella ovum – Reverter-Gil & Fernández-Pulpeiro 2001: 120.

Material examined

Lectotype of Schizoporella ovum (here designated)

SPAIN: Travailleur st. 40, 44°05’00’’ N, 07°14’46’’ W, NW Iberian Peninsula, 15 Aug. 1881, 392 m, Jullien coll., one colony on a shell, figured specimen ( NHMUK 1899.7.1.2348).

Paralectotypes of Schizoporella ovum

SPAIN: same data as lectotype ( MNHN 1025, MNHN 2347).

Other material examined

NORWAY: Alysidota alderi, Busk coll., one uniserial colony, with some avicularia but no ovicell, on a shell ( NHMUK 1899.7.1.2143).

UNITED KINGDOM: Alysidota alderi , Shetland, 1859, Busk coll., paratype ( NHMUK 1899.7.1.2144); Alysidota alderi , Shetland, 1859, Busk coll., type ( NHMUK 1899.7.1.2145); Escharina alderi var. barleii , Shetland, Busk coll., marked as ‘Type?’ ( NHMUK 1911.10.1.1197); Escharina alderi , Scotland, 22 Oct. 1958, st. 12, 52 m, Ryland coll. ( NHMUK 1994.3.14.8).

LOCALITY UNKNOWN: Schizoporella ovum , Talisman 1883 , 340 m, no further data, Calvet coll. ( MNHN 3770).

Description

Colony encrusting, composed of linear series of autozooids, or unilaminar, multiserial. Autozooids oval to hexagonal, separated by sutures. Frontal shield convex, granular, uniformely perforated by some 25 small rounded pores, often inconspicuous, plus a row of small marginal pores. Distolateral vertical walls with several dietella. Primary orifice as long as wide. Inner distolateral orifice rim with immersed, very narrow shelf. Anter slightly horseshoe-shaped, proximal margin straight, with U-shaped sinus, as deep as wide, occupying one third of proximal border. Primary orifice encircled by smooth, broad band of gymnocystal calcification. Oral spines absent. A low, conical umbo may be developed proximal to sinus. Avicularia rare, lateral to orifice, sporadically present in uniserial colonies, apparently absent in multiserial colonies. Rostrum triangular, raised, directed proximally or proximo-laterally. Ovicell globular, recumbent on distal autozooid and partially covering orifice of maternal zooid. Surface granular, with single series of septular pores around basal periphery and sometimes raised into a central umbo. Ancestrula not observed.

Remarks

Busk (1856) described Alysidota alderi , a species with zooids in linear series, imperforate ovicells and rare adventitious avicularia. Some years later, he described Lepralia barleei for a single multiserial colony encrusting a shell collected in Shetland, with ovicells with peripheral pores and lacking avicularia ( Busk 1860).

Norman (1869) was the first author who considered these two species to be synonymous while reporting A. alderi from Shetland at depths between 50 and 170 fathoms (90–310 m). He also stated that the type specimens of both species were in his collection. Hincks (1880) assumed this synonymy to be correct and transferred the species to the genus Schizoporella . Finally, Marcus (1940) transferred Schizoporella alderi to the genus Escharina . Type and other material labeled as A. alderi is conserved at the NHMUK, but no original material of L. barleei seems to exist. Although the sample NHMUK 1911.10.1.1197 is labeled as the type of ‘ Escharina alderi var. barleei ’, it contains two colonies on stones, so they do not match the original description of the species. As no original material of L. barleei is preserved and the original description is very vague, it is not possible at present to confirm or reject the proposed synonymy.

Schizoporella ovum was described by Jullien (1882) for an undeterminate number of dead multiserial specimens, with ovicells with peripheral pores and lacking avicularia, collected off the NW Iberian Peninsula at a depth of 392 m. Three type specimens are now kept at NHMUK and MNHN; the one at NHMUK is here designated as the lectotype. Calvet (1907) reviewed the original record by Jullien, stating that the original material consisted of “ trois échantillons sur coquilles ”. This author also reported two further colonies, also on shells, collected by the Talisman 1883 cruise from an unrecorded locality at a depth of 340 m; this material (MNHN 3770), although belonging to the same species, is not part of the type series. Schizoporella ovum does not seem to have been rediscovered since then, but it was transferred to the genus Schizomavella by Reverter-Gil & Fernández-Pulpeiro (2001) following their revision of the type material at Paris.

The type material of Schizoporella ovum is identical to the sample NHMUK 1911.10.1.1197 (‘ Escharina alderi var. barleei ’), so they belong to the same species. Furthermore, S. ovum may be somewhat similar to Lepralia barleei as originally described. On the other hand, the autozooids of S. ovum are identical to the autozooids of E. alderi (see Figs 4–5 ), as was stated by Hincks (1880: 244) for uniserial and multiserial colonies of S. alderi . Differences between these two species do not appear to be significant. Schizoporella ovum (and L. barleei ) develop multiserial colonies, whereas Escharina alderi forms uniserial chains of zooids. According to Norman (1869), both forms of growth may even share the same substrate. In S. ovum (as in L. barleei ) avicularia have not been reported, and in E. alderi they are rare. Therefore, their presence is perhaps related to the uniserial mode of growth, but in any case, their presence or absence should not be used to differentiate species. In E. alderi the development of a sporadic umbo in the ovicell and in the autozooids has been reported, while it is absent in the material of S. ovum . Its presence may be related to a different degree of calcification, with no phylogenetic significance. Finally, the ovicell was described as imperforate in E. alderi , while in S. ovum (and L. barleei ) it has a series of septular pores around the basal periphery. However, SEM images of the type material of E. alderi demonstrate that the ovicell really has several basal pores ( Fig. 4E ), similar to those present in the types of S. ovum ( Fig. 5D ). It should be stated that in the genus Escharina , as in all members of the family Escharinidae , the ovicell has been described as imperforate (see Hayward & Ryland 1999; Tilbrook 2006), but the pores in the ovicell of E. alderi , as well as in other species of the family (see Bock 2014), indicate that the diagnosis of the family should be amended.

In conclusion, we propose here that Schizoporella ovum (and probably also Lepralia barleei ) are junior synonyms of Escharina alderi , differing mainly in their mode of growth.

Figures

Fig. 4. Escharina alderi (Busk, 1856). A. Group of autozooids (NHMUK 1911.10.1.1197, type of Alysidota alderi Busk, 1856). B. Same, ovicellate zooid; note the distal marginal pores in the ovicell. C. Same, detail of a broken ovicell. D. Same, primary orifice. E. Ovicellate zooid and one adventitious avicularium in a uniserial colony (NHMUK 1899.7.1.2145, paratype of Alysidota alderi Busk, 1856).

Fig. 5. Schizoporella ovum Jullien, 1882. A. Entire colony (NHMUK 1899.7.1.2348, lectotype). B. Same, primary orifice. C. Same, a broken ovicell showing the marginal pores. D. Ovicellate and nonovicellate zooids (MNHN 2347, paralectotype). E. Dietella (MNHN 1025, paralectotype).