Sertularella implexa ( Allman, 1888 )

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 : 282-285

Sertularella implexa ( Allman, 1888)

Figs 12B , 13 A-D; Table 13

Sertularia implexa p.p. Allman, 1888: 54, pl. 26 figs 1, 1a. – Hartlaub, 1901: 90. – Bedot, 1916: 223.

non Sertularella implexa . – Galea & Schories, 2012a: 40, pl. 3 fig. 4F-J (= Sertularella recta Galea & Schories , sp. nov.)

Sertularella picta . – Vervoort, 1972: 113, figs 34, 35C [non Ser- tularella picta ( Meyen, 1834) ].

non Sertularella picta . – Vervoort, 1972: 114, fig. 35A-B [= Sertularella fuegonensis El Beshbeeshy, 2011 ].

Material examined: NHML 1888.11.13.42; a vial containing numerous sterile colony fragments in alcohol (designated here as the lectotype of S. implexa ), as well as two slides. One slide ( Fig. 12A ), marked as “type”, bears the label “Challenger Stat. 314, Falklands, Depth 70 faths, Sertularia implexa ”, and contains a 1.1 cm high colony fragment bearing 3 side branches. This material clearly does not belong to Allman’s species; in addition, its hydrothecae were quite distorted upon squashing between slide and coverslip. The other slide ( Fig. 12B ), labeled “Challenger Coll., Sertularia implexa , bet. Cape Virgins & Falkland Is., 24” is a 1.6 cm high colony fragment bearing 5 side branches, and is in agreement with both the bulk of the alcoholpreserved material and Allman’s pl. 26 fig. 1A. This second slide is selected here as the paralectotype of S. implexa . Among the alcohol-preserved material, three colony fragments (6, 12 and 18 mm high) could be identified as Sertularella hermanosensis El Beshbeeshy, 2011 , and are possibly conspecific with the material mounted in the “type” slide; they were transferred to a separate vial.

Description: Colonies growing in loosely entangled tufts, up to ca. 7.5 cm high; profusely and irregularly branched in all directions, with no definite main stems. Stems and side branches strictly monosiphonic, divided into long, slender internodes by means of oblique nodes; first internode with a proximal twist, and comparatively longer than subsequent ones; a hydrotheca, or a hydrotheca and a short apophysis arising laterally from below its base, confined to the distal part of each internode; hydrothecae in two alternate rows; rows coplanar or slightly shifted on to one side of the colony. Side branches originating every 1-14 hydrothecae; up to 3rd order branching observed. Hydrothecae long, adnate for 2/5th their length to the corresponding internode; swollen adaxially; perisarc either smooth or with 1-2 faint wrinkles forming shallow ridges not extending completely abaxially; abaxial wall nearly straight; abaxial cusp produced, remaining cusps triangular with rounded tips, separated by deep embayments; no intrathecal, submarginal projections of the perisarc. Gonothecae arising from below the hydrothecae; broadly ovoid, tapering below, distal half provided with ca. 6 transverse ridges; aperture on top, surrounded by 4 small cusps.

Dimensions: See Table 13.

Remarks: The typical silhouette of a colony is accurately depicted by Allman (1888) in his pl. 26 fig. 1. Part of Vervoort’s (1972) material assigned to S. picta ( Meyen, 1834) , notably that from Vema 18-16 (described in detail), shows the following features: 1) the colony is bushy, composed of “irregularly intertwining, fine […] repeatedly branched, sidebranches”; 2) both the stems and branches are monosiphonic throughout; 3) the internodes are moderately long; 4) the hydrothecae are “arranged in two planes, that make a very obtuse angle”; 5) their free adaxial wall is “about 1.5-2 times the length of the fused part, […] distinctly undulated, though the mode of development of the undulations is variable”. Taken together, these represent distinctive features of S. implexa . Vervoort’s material was fertile, and his account represents the first description of the gonotheca of this species.

Distribution: Chile – Región de Magallanes y Antártica Chilena [off Isla Nueva ( Vervoort, 1972, as S. picta )]. Argentina – Provincia de Santa Cruz [off Deseado ( Vervoort, 1972, as S. picta )]; Provincia de Tierra del Fuego, Antártida e Islas del Atlántico Sur [off Isla de los Estados ( Vervoort, 1972, as S. picta )]. Between Cabo Virgenes and the Falkland Is. ( Allman, 1888).

Figures

Fig. 12. (A) Sertularella (?) hermanosensis El Beshbeeshy, 2011. Likely a fragment of this species mounted on slide, as part of the type material of S. implexa (Allman, 1888). (B) Sertularella implexa (Allman, 1888), fragment from type colony mounted on slide. (C) Sertularella juanfernandezensis Galea, sp. nov., identified as S. polyzonias (Linnaeus, 1758) by Jäderholm (1910). (D) Sertularella robusta Coughtrey, 1876, identified as S. tenella (Alder, 1857) by Ritchie (1907). (E, F) Sertularella subantarctica Galea, sp. nov. Materials identified as S. allmani Hartlaub, 1901 by Jäderholm (1910, 1905) (E, F, respectively). (G, H) Sertularella valdiviae Stechov, 1923 a, two slides prepared from type colony.

Fig. 13. (A-D) Sertularella implexa (Allman, 1888). Colony fragments from holotype material (A) and Vervoort (1972, as S. picta) (B). Hydrothecae from the same sources (C and D, respectively). (E, F, H, I) Sertularella juanfernandezensis Galea, sp. nov. Portions of colonies from SMNH 123883 (E) and ZMB Cni 4421 (F), and comparison with S. polyzonias (Linnaeus, 1758) HRG- 0550 (G). Hydrothecae from the same sources (H, I and J, respectively). (L, M) Sertularella leiocarpa (Allman, 1888). Portion of colony (L) and hydrotheca (M) from HRG- 1056. Scale bars: 200 μm (C, D, H-J, M), 500 μm (K), 1 mm (A, B, E-G, L).