Sertularella juanfernandezensis Galea, 2017

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 : 285-288

Sertularella juanfernandezensis Galea , sp. nov.

Figs 12C , 13E, F, H, I ; Table 14

Sertularella polyzonias . – p.p. Jäderholm, 1910: 4. – p.p. Hartlaub, 1905: 655 [non Sertularella polyzonias ( Linnaeus, 1758) ].

Holotype material: SMNH 123883; Chile, Juan Fernández archipelago, 35 m, Swedish Magellanic Expedition 1907-1909, coll. C. Skottsberg; 24.08.1908; microslide ( Fig. 12C ) with three colony fragments 7-20 mm long, the largest bearing 4 gonothecae, the smallest unbranched, and the remaining two provided with two side branches each [material identified by Jäderholm (1910) as S. polyzonias ( Linnaeus, 1758) ].

Paratype material: ZMB Cni4421; Chile, Juan Fernández archipelago; coll. Plate, det. Hartlaub (1905, as S. polyzonias ); a 3.8 cm high colony represented by a single, ramified, sterile stem.

Comparison material: HRG-0550; France, Brittany, depth unrecorded, coll. F. Ziemski; (day and month unavailable) 2011; numerous sterile, unbranched or sparingly-branched stems and fragments, up to 4.5 cm high, of S. polyzonias .

Diagnosis: Erect, coplanar colonies with monosiphonic, irregularly pinnate stems; internodes moderatelylong, slightly geniculate; hydrothecae flask-shaped, decidedly facing outwards, adnate for half their length, free adaxial wall convex; gonothecae broadly ovoid, transversely wrinkled, aperture mounted on constricted neck region, surrounded by 4 blunt spines.

Etymology: Named after its (presently known) area of occurrence.

Description: Colonies erect (though flaccid when out of liquid), up to 3.8 cm high, arising from creeping, branching stolon. Stems monosiphonic, unbranched; basal part of varied length (ca. 1.5 cm long in paratype) and ahydrothecate; above, divided into moderatelylong, slightly geniculate internodes by means of oblique constrictions of the perisarc slanting in alternate directions; one hydrotheca confined to the distal end of each internode; side branches arising generally singly (occasionally in pairs) immediately below the base of a hydrotheca, either laterally or slightly shifted on to the front of stem, giving the colony a globally planar appearance; there are no distinct apophyses supporting the branches; 1-4 hydrothecae between successive side branches; branches not strictly alternate, several successive ones may be given off on same side of the stem; up to 2nd order branches observed; first internode comparatively longer than subsequent ones; remainder with structure similar to that of stem. Hydrothecae biseriate, alternate, flask-shaped, smooth-walled, adnate for half their length to the corresponding internode, with distinct outward bend; free adaxial wall convex for most of its length, slightly upturned distally; abaxial wall concave for 3/4th its length, and distinctly convex below aperture; rim tilted away from stem/branches, and provided with 4 pointed, triangular cusps separated by moderately-deep embayments; a four-flapped operculum; three conspicuous internal, submarginal, lamellar projections of the perisarc, one abaxial and two latero-adaxial, the latter could be absent in distalmost, hence youngest, hydrothecae. Gonothecae arising laterally from the internodes, a short distance below the hydrothecal bases; broadly ovoid, transversely wrinkled (up to 6 distinct ridges in upper 2/3rd), tapering below into short, indistinct pedicel, distally bearing a constricted neck region on the top of which is found the aperture surrounded by 4 short, blunt spines; sex could not be ascertained, although a single, ovoid, central mass is carried on by the blastostyle.

Dimensions: See Table 14 .

Remarks: This species has been incorrectly assigned to Sertularella polyzonias ( Linnaeus, 1758) by both Hartlaub (1905) and Jäderholm (1910). Its morphological differences with the Linnean species are easily noted by comparing Fig. 13E, F and 13G , and Fig. 13H, I and 13J , respectively.

The hydrothecae of S. juanfernandezensis are very similar to those of a number of congeners, notably: 1) S. arbuscula ( Lamouroux, 1816) , but this species possesses very short internodes ( Millard, 1957), and its gonothecae are fusiform and, most often, smoothwalled ( Millard 1975); 2) S. crassiuscula Bale, 1924 , but this species has comparatively smaller hydrothecae, its internodes are very short, and its gonothecae are large and devoid of the distinctly constricted neck region met with in the present species ( Bale, 1924; Ralph, 1961); 3) S. falsa Millard, 1957 , but this species has relatively short internodes, there are 4 submarginal, intrathecal projections of the perisarc alternating with the hydrothecal cusps, and its gonothecae are spindle-shaped ( Millard, 1957).

Distribution: Only known from Chile – Juan Fernandez archipelago ( Hartlaub, 1905; Jäderholm, 1910).

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).

Tables

Table 14. Measurements of Sertularella juanfernandezensis Galea, sp. nov., in μm.

	Present study, SMNH 123883	Present study, ZMB Cni4421
Internode
- length (in general)	735-980	885-1165
- length of 1 st internode	1410-1570	1290-1765
- diameter at node	155-205	210-290
Hydrotheca
- free adaxial length	375-450	360-420
- adnate adaxial length	355-400	400-450
- abaxial length	520-585	540-575
- maximum width	330-345	315-410
- diameter at aperture	225-255	220-260
Gonotheca
- total length	1325-1350	-
- maximum width	860-885	-