Spigaleos striatula, Hayward & Winston, 2011

Hayward, Peter J. & Winston, Judith E., 2011, Bryozoa collected by the United States Antarctic Research Program: new taxa and new records, Journal of Natural History 45 (37 - 38), pp. 2259-2338 : 2331-2334

Spigaleos striatula sp. nov.

( Figure 34A, B )

Material

Holotype. NMNH 1154057 : Eltanin cruise 9, station 740, 56 ◦ 06’ to 56 ◦ 07’ S, 66 ◦ 19’ to 66 ◦ 30’ W, 494– 384 m, 18 September 1963; fragment of colony, 6 mm long.

Paratypes. VMNH 013674.00: same data as holotype; two fragments, 8.75 and 11.37 mm .

Description

Colony erect, dichotomously branched, the branches cylindrical in section, slightly curved. Autozooids axially budded, in spiral whorls of four, the orifices opening on a defined frontal surface comprising half of the branch circumference; abfrontal surface smoothly calcified, with fine longitudinal striations and sparse, slit-like pores. Autozooids elongate but with indistinct boundaries, marked only by a few slit-like marginal pores; frontal calcification apparently continuous, finely granular with sinuous longitudinal striations and grooves. Primary orifice wider than long, 0.11 × 0.09 mm, proximal edge with a short, rectangular sinus occupying just less than half its width between distinct, rounded condyles. Each autozooid with a medioproximal, suboral avicularium, its rostrum slightly acute to frontal plane, directed proximally, broadly triangular, slightly hooked distally; crossbar comparatively stout, with a blunt columella. Ovicell prominent, hyperstomial, projecting markedly from the plane of the branch; frontal surface with an extensive area of membranous ectooecium, the underlying entooecium faintly rugose and with a few small, indistinct pores.

In later ontogeny the primary orifice becomes deeply immersed and the secondary orifice and the avicularium become progressively sealed by centripetally advancing calcification. The oldest, proximal parts of the colony are almost smooth, with fine striations and sporadic, slit-like pores.

Etymology

Latin, stria; furrow, with reference to the striated calcification.

Remarks

Spigaleos was introduced ( Hayward 1992) for the endemic Antarctic species, Cellepora horneroides Waters, 1904 , and has remained monotypic until now. Spigaleos striatula sp. nov. is distinguished from the genus type especially in its primary orifice, which is wider than long, with a short, broad sinus, whereas that of S. horneroides is rounded, with a narrow U-shaped sinus. In the latter the suboral avicularium has a pronounced proximal heel that projects into the lumen of the peristome, obscuring the sinus and resembling a lyrula, while the proximal edge of the avicularium is straight in S. striatula sp. nov. and the sinus is clearly visible.

Superfamily CONESCHARELLINOIDEA Levinsen, 1909 Family LEKYTHOPORIDAE Levinsen, 1909

Turritigera stellata Busk

( Figure 34C )

Turritigera stellata Busk, 1884: 130 , pl. 24, fig. 1.

Turritigera stellata: Waters, 1888: 22 , pl. 1, figs 22, 25; 1904: 76, pl. 5, fig 3, pl. 8, fig 13; Moyano, 1974: 18, figs 4, 8, 31–34; Cook and Hayward, 1983: 67, figs 4, 10, (not 14c).

Material

Lectotype (selected here). BMNH 1944.1.8. 240, Challenger station 320, 37 ◦ 17’ S, 53 ◦ 52’ W, 600 fm (1097 m).

Other material. Hero cruise 715, station 894, 54 ◦ 55’ to 54 ◦ 54.8’ S, 64 ◦ 20’ to 64 ◦ 19’ W, 263–285 m (five specimens, the largest c. 1 cm high, with horizontal spread c. 1 cm).

Remarks

Busk (1884) founded his taxon Turritigera stellata gen. nov., sp. nov., on specimens from two Challenger stations, station 320, southwest Atlantic (37 ◦ 17’ S, 53 ◦ 53’ W), and station 142, southeast Atlantic (35 ◦ 4’ S, 18 ◦ 37’ E,). His description, though brief, applies most closely to the specimen from stn 320, selected here as the lectotype. The specimen might have been a single colony but now consists of three fragments. The largest fragment includes the base of the colony, encrusting part of a hydrocoralline. Busk (1884) did not describe the primary orifice of his specimens, but the few subsequent descriptions of T. stellata from the southwest Atlantic explicitly describe the primary orifice and its small sinus, and it has been particularly well illustrated by Moyano (1974). The material from Challenger station 142, though superficially similar to that from station 320, belongs to another, apparently undescribed, species of Turritigera . Cook and Hayward (1983) noted that material from the Patagonian Shelf, South Africa and Antarctica attributed to T. stellata showed some differences in morphological characters, did not describe the primary orifices, but provided a diagram ( Cook and Hayward 1983: fig. 14c) based on the primary orifice of the South African specimen (Challenger station 142). Hayward (1993) described the salient features of specimens from the two Challenger stations and figured the primary orifice in both cases, to demonstrate that two distinct species could be recognized. The primary orifice of the lectotype specimen of T. stellata ( Hayward 1993: fig. 7d) has a short, U-shaped sinus on its proximal edge, comprising no more than one-third of the total proximal width of the orifice, whereas the primary orifice of the specimen from station 142 ( Hayward 1993: fig. 7c) has a broadly U-shaped sinus occupying practically the whole of its width. The USARP specimens of T. stellata correspond closely with the Challenger material from the Patagonian Shelf, and with that described by Moyano (1974) from southern Chile, and the primary orifice ( Figure 34C ), in particular, matches that of the lectotype specimen. The “ T. stellata ” recorded from Marion Island, south Indian Ocean by Branch and Hayward (2007) resembles the specimens from Challenger station 142, in the possession of up to seven peristomial avicularia, one of which is much larger than the rest, although the shape of the primary orifice has not been precisely defined. The two sets of specimens may be conspecific and should be redescribed as a new species. Turritigera stellata therefore has a far narrower geographical distribution than was supposed. A second, undescribed, species is presently known from a limited region of the southeast Atlantic/south Indian Ocean, further species have been described in recent years from Antarctica ( Hayward 1993) and Marion Island ( Cook and Hayward 1983), and the genus perhaps has a polar and cold temperate, circumpolar distribution in the southern hemisphere.

Conclusion

The three samples from South Pacific localities yielded two new species of cheilostomate Bryozoa, one representing a new genus within Microporidae , whereas the single sample from the Ross Sea included fragmentary material of a species unrecorded since its original description by Busk (1884), and shown to be sufficiently distinctive to warrant the introduction of a new genus within Cellariidae . The remaining 25 samples fall naturally into two groups, one originating from eight stations in the subantarctic southwest Atlantic, mostly south of Tierra del Fuego, and the other from 14 localities south of the Antarctic convergence, in the region of the Scotia Arc. The 14 Antarctic samples included nine new species; four of these belong to genera largely or entirely limited to Antarctica, and four to genera restricted to the cold southern hemisphere, whereas Cellaria limbata sp. nov. is representative of a genus with a worldwide distribution. The addition of nine new taxa of cheilostomate Bryozoa to the Antarctic fauna is noteworthy enough, but the new species collected from the nine subantarctic localities are of considerable interest.

Eighteen new species were present in the subantarctic samples, 13 of which occurred in a single sample. The shelf environments of Tierra del Fuego and the southernmost Patagonian Shelf are perhaps the least explored of the entire subantarctic southwest Atlantic region, and this striking increase in bryozoan diversity is not unexpected. Reteporella magellensis (Busk) is the only phidoloporid presently known from the whole of the cold temperate southwest Atlantic, and given the diversity of the genus elsewhere, including Antarctic shelf environments, the discovery of additional, undescribed species, might have been predicted. Recorded diversity of Smittinidae and Microporellidae in this region is also low in comparison to other shelf environments, including Antarctica, and the discovery of new species in the geographically widespread genera, Parasmittina , Smittoidea , Hemismittoidea , Fenestrulina and Microporella is not unusual. The three new species of Osthimosia present in the sample from south of Terra del Fuego are all characterized by individually tiny colony size. This taxonomically difficult genus has a known high diversity in both cold temperate and polar southern hemisphere environments, but species are most often defined, and later identified, following SEM examination. Two new genera were recognized among the 18 new subantarctic taxa: Scriblitopora represents a further distinctive morphological expression within the Microporidae , while Schizocoryne is a more enigmatic entity, classified within the Lepraliellidae . Lageneschara peristomata sp. nov., Cellarinelloides megaciona sp. nov. and Spigaleos striatula sp. nov. are of particular interest as new species within formerly monotypic genera, all previously regarded as Antarctic endemics.

Figures

Figure 34. (A,B) Spigaleos striatula sp. nov., Paratype. (A) Portion of a branch, with ovicells and characteristic striated calcification; (B) detail to show primary orifice. (C) Turritigera stellata, the primary orifice. Scale bars: 0.25 mm (A), 0.05 mm (B, C).