Sertularella mixta, Galea, Horia R. & Schories, Dirk, 2012

Galea, Horia R. & Schories, Dirk, 2012, Some hydrozoans (Cnidaria) from Central Chile and the Strait of Magellan, Zootaxa 3296, pp. 19-67 : 42-44

Sertularella mixta sp. nov.

(fig. 5A–G, table 4)

Sertularella sanmatiasensis — Galea et al., 2009: 12 , fig. 3C–E [not S. sanmatiasensis El Beshbeeshy, 2011 ].

Material examined. Stn. RHO — 01.xi.2009, DS283 (20 m): a few sterile stems, on sponge. Stn. TIB — 01.xi.2009, DS166 (15 m): several infertile stems co-occurring with Sertularella sp. (MHNG-INVE-79628); DS206 (17 m): holotype (MHNG-INVE-79667)—numerous stems, either sterile or fertile, up to 2.6 cm high.

Description. Stems arising from creeping, branching, anastomosing hydrorhiza. Stems monosiphonic, unbranched or sparingly branched in one plane. Basal part of varied length, though short, with a few wrinkles above origin from stolon; remainder of stem composed of ca. 30 hydrothecate internodes. Internodes rather short, separated by oblique nodes sloping in alternate directions; one hydrotheca distally. Side branches, when present, commonly originating from within a stem hydrotheca or, more classically, borne on a short stem apophysis arising from below a stem hydrotheca. Hydrotheca tubular, slightly swollen, especially on adcauline side; adnate for half its adcauline length; abcauline wall straight to slightly swollen basally; aperture mounted on a short neck and widening at rim; abcauline cusp the longest; cusps not very prominent, separated by shallow embayments; three internal perisarc projections, one abcauline and two latero-adcauline. Gonothecae arising from below a stem hydrotheca: ovoid, with several transverse ridges distally, attenuated basally; aperture mounted on short neck; the latter quadrangular, with four projections of perisarc. Sex could not be ascertained.

Remarks. Hydroids in these samples, comprising a rather substantial number of colonies, are conspecific with the relatively scant material assigned to S. sanmatiasensis El Beshbeeshy, 2011 by Galea et al. (2009). The latter has a ratio of internode length/hydrothecal adnate adaxial wall significantly higher than in our material [see table 47 in El Beshbeeshy (2011)]. Additionally, El Beshbeeshy (2011) pointed out the peculiar bright orange and reddish brown tinge of both the perisarc and hydranths, respectively. Judging from the period of time between the date of collection and the examination of his samples (ca. a quarter of a century, from 1966 to the date of publication of his thesis in 1991), their colors are apparently long-lasting. These are totally absent in our recentlycollected material, suggesting another specific difference.

Sertularella mixta sp. nov. belongs to a morphologically similar group of species composed of S. africana Stechow, 1919 , S. ellisii (Deshayes & Milne-Edwards, 1836) 9, S. fusiformis (Hincks, 1861) , S. lagenoides Stechow, 1919 , S. mediterranea Hartlaub, 1901 , S. simplex (Hutton, 1873) , and S. uruguayensis Mañé-Garzón & Milstein, 1973 . All these species form short, monosiphonic, unbranched or sparingly-branched stems, divided into short, more or less geniculate internodes, each bearing a basally-swollen to fusiform hydrotheca, provided with three internal, submarginal cusps. Their gonothecae are transversely ribbed and provided with generally four cusps surrounding the aperture.

From table 4 it appears that both S. africana and S. simplex are much smaller species compared to S. mixta , whereas the European group of species fall into a more similar range of variation. However, their known geographical distribution is limited to the Mediterranean and the temperate parts of the NE Atlantic.

8. Billard (1922) already raised the question concerning the synonymy between the two species, listing only minor differences for S. picta , with likely no taxonomic importance, viz. a more prominent abaxial hydrothecal cusp, a much thickened rim, more conspicuous intrathecal perisarc projections, and a thickened hydrothecal base on the adaxial side.

9. The taxonomy of European Sertularella is unsettled, and opinions on the validity of the various nominal species strongly diverge [compare, for example, Picard (1956) and Peña Cantero & García Carrascosa (2002)].

TABLE 4. Comparative measurements of several species morphologically related to Sertularella mixta sp. nov., in µm. *Dimensions of hydrothecae of S. uruguayensis were recalculated from figs 2, 3 in Mañé-Garzón & Milstein (1973), and are given in brackets.

Based on geographical grounds, S. mixta comes closer to S. uruguayensis . However, its internodes are comparatively longer with respect to the adnate part of the hydrothecae; the thecae are larger, more tubular, forming a more acute angle (25–35°) with their corresponding internodes; their free adaxial wall is not so obviously swollen, and the abcauline cusp is less prominent.

Comparisons of gonothecae of the two species cannot be made presently because those of S. uruguayensis were inaccurately described and figured: the scale bar of 100 µm in fig. 4 by Mañé-Garzón & Milstein (1973) is probably incorrect (more likely it would be 1 mm long). Meanwhile, they seem to lack perisarcal projections surrounding the aperture, as observed in S. mixta .

Etymology. The specific epithet refers to the characteristic appearance of the species, which displays a combination of morphological characters found in a number of its congeners.

Distribution in Chile. Known only from Punta de Choros, Región de Coquimbo (present study).