Sertularella antarctica Hartlaub, 1901

Horia R. Galea, Dirk Schories, Verena Häussermann & Günter Försterra, 2017, Taxonomic revision of the genus Sertularella (Cnidaria: Hydrozoa) from southern South America and the subantarctic, with descriptions of five new species, Revue suisse de Zoologie 124 (2), pp. 255-321 : 260-263

Sertularella antarctica Hartlaub, 1901

Fig. 3 A-G; Table 2

Sertularella antarctica Hartlaub, 1901: 82 , pl. 6 figs 27, 28 (replacement name for Sertularella unilateralis Allman, 1876: 114 ). – (?) p.p. Jäderholm, 1903: 283. – Hartlaub, 1905: 650, fig. P4, Q4. – Bedot, 1916: 200; 1918: 235. – Billard, 1924: 61. – (?) Vervoort, 1972: 106, fig. 32. – El Beshbeeshy, 2011: 119, fig. 37D.

non Sertularella antarctica . – p.p. Jäderholm, 1903: 283 [= Sertularella gaudichaudi ( Lamouroux, 1824) ]. – Jäderholm, 1905: 32, pl. 13 fig. 1 (= Sertularella subantarctica Galea , sp. nov.). – Blanco, 1963: 170, figs 5-6 (= Sertularella allmani Hartlaub, 1901 ).

Sertularella unilateralis Allman, 1876: 114 . – Allman, 1879: 282, pl. 18 figs 10, 11. – Studer, 1879: 120. – Kirchenpauer, 1884: 40.

non Sertularia unilateralis Lamouroux, 1824: 615 , pl. 90 figs 1-3 [= Symplectoscyphus unilateralis ( Lamouroux, 1824) ].

Sertularella allmani. – (?) Nutting, 1904: 84, pl. 18 figs 3-6

[non Sertularella allmani Hartlaub, 1901 ].

Sertularella gigantea . – Billard, 1906: 12, fig. 4 [non Sertu-

larella gigantea Mereschkowsky, 1878 ].

Sertularella ? lagena . – Galea & Schories, 2012a: 41, fig. 4K-L

[non Sertularella lagena Allman, 1876 ].

Sertularella sanmatiasensis . – (?) Peña Cantero, 2006: 939, fig. 3L. – (?) Peña Cantero & Gili, 2006: 767. – (?) Peña Cantero, 2008: 459, fig. 2C. – (?) Peña Cantero & Vervoort, 2009: 87, fig. 2B. – Peña Cantero, 2012: 858, fig. 4A; 2013: 130 [non Sertularella sanmatiasensis El Beshbeeshy, 2011 ].

Material examined: ZMH C04161; Chilean- Argentinean border, Dungeness Point, beach, coll. Michaelsen no. 104; 15.10.1892; a few fragments (only a part of the whole sample examined herein), up to 2.2 cm high. According to Hartlaub (1901), this appears to be the sole material on which he based his species upon. As no holotype was designated by him, it is here regarded as the lectotype of S. antarctica . – ZMH C11879; FRV Walther Herwig, Argentine Shelf, no additional data; several sterile colony fragments, up to 5.2 cm high, with almost only the perisarc left, identified as S. antarctica Hartlaub, 1901 . – MHNG- INVE-79773; Antarctica, King George I., Ras Tu, -62.22139° -58.88694°, 15-20 m, coll. D. Schories, lot Ant. 12/2011; 21.02.2010; fully fertile (female) colony with stems up to 6.5 cm high. – MHNG- INVE-79776; Antarctica, King George I., Ras Tu, -62.22139° -58.88694°, 15-20 m, coll. D. Schories, lot Ant. 03/2011; 21.02.2010; numerous stems and fragments up to 5.5 cm high, some bearing female gonothecae. – HRG-0534; Antarctica, King George I., Ras Tu, -62.22139° -58.88694°, 10-40 m, coll. D. Schories, lot Ant. 08/2010; 12.02.2010; numerous stems and fragments, up to 4 cm high, one bearing a female gonotheca. – HRG-0290; Antarctica, Low I., -63.43009° -62.2038°, 82 m, coll. Bentart 2006, leg. A.L. Peña Cantero; 02.2006; numerous fertile stems, up to 9.5 cm high, sex could not be ascertained [part of the material from Stn. Low 44 studied by Peña Cantero (2013)]. – HRG-0362; Chile, Región de Magallanes y de la Antártica Chilena, Punta Arenas, Faro San Isidro, -53.78174° -70.97391°, 40 m, coll. D. Schories, lot #25; 04.01.2011; three minute sterile stems [material assigned to Sertularella ? lagena Allman, 1876 by Galea & Schories (2012a)].

Description: Inspected colonies up to 9.5 cm high, arising from creeping, branching stolon. Stems monosiphonic, provided basally with 3-5 annuli above origin from stolon, then divided into uniform, moderatelylong internodes by deep, oblique constrictions of perisarc slanting in alternate directions. A hydrotheca, or a hydrotheca and a short, lateral apophysis arising from below its base, confined to the distal end of each internode; proximally a couple of spiral twists (occasionally only one, or two incomplete), and distally a bulge. Hydrothecae, apophyses, and side branches shifted on to one side of the stem, at a wide angle, not giving the colony a markedly fronto-dorsal aspect. Branching pattern irregularly pinnate, with side branches originating every 0-18 stem hydrothecae, either alternately or many on the same side; up to 4th order branching; structure similar to that of stem; 1 st internode with 2 (rarely 3) spiral twists basally, length generally greater (occasionally shorter, or equal) than that of subsequent internodes. Hydrothecae long, flask-shaped, adnate for 1/3rd of their length to the corresponding internode, swollen adaxially at varied degrees; abaxial wall almost straight; free adaxial wall sigmoid, convex for most of its length, becoming concave immediately below aperture; aperture surrounded by 4 unequally-developed, triangular cusps: abaxial one produced, thought at varied degrees, adaxial the shortest, and the laterals asymmetrical; rim thickened, renovations occasional; 3 intrathecal, submarginal cusps (2 latero-adaxial, 1 abaxial), not always discernible; a 4-flapped operculum. Gonothecae borne on both stems and side branches, male similar to female; elongated-ovoid, walls transversely-wrinkled, especially on distal half, aperture mounted on short neck region and surrounded by generally 4 blunt cusps (up to 6 possible).

Dimensions: See Table 2.

Remarks: Hartlaub (1901) introduced the replacement name Sertularella antarctica for Sertularella unilateralis Allman, 1876 in order to avoid the secondary homonymy with Sertularia unilateralis Lamouroux, 1824 , the latter considered by him as belonging to the group of 3-cusped Sertularella species (presently accepted as Symplectoscyphus Marktanner- Turneretscher, 1890).

Calder (2015, p. 239, note 39) expressed the view that Hartlaub’s (1901) binomen “has been used only sparingly […], and nomenclatural stability is not greatly threatened by adopting its senior synonym ( Sertularella unilateralis Allman, 1876a ) for the species”. However, in light of the present study, his opinion changed (Calder, pers. comm.) taking into account that secondary homonymy no longer exists in the case of S. unilateralis , and the substitute name S. antarctica has come into rather frequent use for the species (ICZN Art. 59.3.).

Type material of S. unilateralis is likely no longer extant in NHML (A. Cabrinovic, pers. comm.), and a comparison with the lectotype of S. antarctica is therefore impossible, leaving some doubts as to the conspecificity between these two nominal species. Indeed, the colony silhouette illustrated by Allman (1879, pl. 18 fig. 10) does not differ much from that of his Sertularia secunda (= Sertularia unilateralis ) ( Allman, 1888, pl. 25 figs 2, 2a) (= S. allmani Hartlaub, 1901 , see previous species). El Beshbeeshy (2011) was right in stating that S. allmani and S. antarctica are two distinct, well-defined species. A contrary opinion was expressed earlier by Vervoort (1972), who founded his conclusion based exclusively on Hartlaub’s (1901) accounts (p. 81 and 82, respectively), but not on the reexamination of the corresponding materials studied by the German author. This erroneous opinion was subsequently followed by Galea et al. (2009, as S. antarctica , p. 7 figs 2J-N, 3A-B) and Galea & Schories (2012a, as S. antarctica , p. 22, footnote 2, pl. 3D). However, the reexamination of the lectotypes of both S. allmani and S. antarctica for the purpose of the present study, leaves no doubts about the correctness of El Beshbeeshy’s statement.

The typical shape of a colony of this species is illustrated in Galea & Schories (2012b, pl. 1R), while its gonothecae appear in the insert of the same plate, as well as in fig. 2S of the same paper.

The development of the perisarc in various colonies ranges from rather thin (e.g. HRG-0290, HRG-0405, HRG- 0 524, and HRG-0534) to exceedingly hypertrophied (e.g. ZMH C04161, ZMH C11879). The adaxial side of the hydrotheca is swollen at varied degrees but, generally, approaches an almost tubular shape; in some colonies, the hydrothecae are distinctly swollen, resembling those of S. allmani but, in this case, the colony shape is diagnostic. The hydrothecal rim is conspicuously thickened, though less so in younger thecae; renovations were observed in only several instances ( Billard, 1906, as S. gigantea ; specimen HRG-0524). The abaxial, marginal cusp is always produced, though at varied extents. On the other hand, the submarginal, intrathecal projections of perisarc may be either absent or only lightly indicated (e.g. HRG- 0534), present only on adaxial side (e.g. HRG-0405), or fully displayed (3 cusps, e.g. HRG-0290, ZMH C04161, ZMHC11879).

Type material of Sertularella lagena Allman, 1876 , a poorly-described nominal species, obviously based on a young specimen, could not be located in collections of NHML (A. Cabrinovic, pers. comm.). However, the illustration provided by Allman (1879) places it closest to the present species, an opinion already expressed by Hartlaub (1901, p. 83, fig. 53; 1905, p. 647, figs M4-N4). The scarce material studied earlier by Galea & Schories (2012a), and provisionally assigned to S. lagena , was reexamined. It belongs to a very young colony whose stems do not exceed 5 internodes. Their hydrothecae are not obviously shifted unilaterally, and no intrathecal, submarginal cusps are present, although a careful inspection shows that the rims of some hydrothecae are slightly, but characteristically thickened. This, added to the typical shape and size of its internodes, suggests strong affinities with S. antarctica .

Through the courtesy of A.L. Peña Cantero, one of us (HRG) was able to examine a specimen from Low I., Antarctica (HRG-0290) identified by him as S. sanmatiasensis El Beshbeeshy, 2011 ( Peña Cantero, 2013). In light of the present observations, there is no doubt that this material belongs to the present species. Consequently, it is assumed that at least some earlier records of El Beshbeeshy’s species in the various papers (co)authored by Peña Cantero also belong to S. antarctica . However, since there are no formal descriptions of the materials involved and, occasionally, no illustrations of them, uncertainties subsist as to their real taxonomic statuses. In only rare instances (e.g. Peña Cantero, 2012), the morphology of both internodes (length, presence of proximal twists) and hydrothecae (thickened margin) leaves little doubt about the identity of the materials involved.

Distribution: Chile – Región de Magallanes y de la Antártica Chilena [(?) Isla Lennox, (?) Lennox Cove, and (?) Borgin Bay ( Jäderholm, 1903); (?) Magellan Strait ( Nutting, 1904, as S. allmani ; Vervoort, 1972); south of Peninsula Brunswick ( Galea & Schories, 2012a, as S.? lagena )]. Chilean-Argentinean border – Dungeness Point ( Hartlaub, 1901; 1905; El Beshbeeshy, 2011). Argentina – Provincia de Tierra del Fuego, Antártida e Islas del Atlántico Sur [(?) off the NE coast of Islas de los Estados ( Vervoort, 1972)]. French Southern and Antarctic Lands, Kerguelen Is. – Swains Bay ( Allman, 1876; 1879, both as S. unilateralis ). Antarctica – Wandel I. ( Billard, 1906, as S. gigantea ), Bellingshausen Sea ( Peña Cantero, 2012, as S. sanmatiasensis ), Low I. ( Peña Cantero, 2013, as S. sanmatiasensis ), King George I. ( Galea & Schories, 2012b, as S. gaudichaudi ).

Figures

Fig. 3. (A-G) Sertularella antarctica Hartlaub, 1901. Colony fragments from lectotype (A), HRG- 0290 (B) and HRG- 0524 (C). Hydrothecae from lectotype (D), HRG- 0290 (E), HRG- 0524 (F) and HRG- 0534 (G). (H, I) Sertularella asymmetra Galea & Schories, 2014. Portion of colony (H) and hydrotheca (I). Scale bars: 200 μm (D-G, I), 1 mm (A-C, H).