Phialella

Galea, Horia R., Schories, Dirk, Försterra, Günter & Häussermann, Verena, 2014, New species and new records of hydroids (Cnidaria: Hydrozoa) from Chile, Zootaxa 3852 (1), pp. 1-50 : 8

Phialella ? falklandica Browne, 1902

( Fig. 1 E, G, H)

Campanulina chilensis ― Naumov & Stepanjants, 1962: 76, Fig. 3.― Stepanjants, 1979: 42, pl. 7 Fig. 7. not Campanulina chilensis Hartlaub, 1905: 589 , Figs L2, M2b, N2.

Material examined. HF9, Isla Tres Hermanas, lat. -43.77537, long. -73.02893, 17.i.2011, 19.1 m, sample C504: colony with both stolonal and erect growth forms, epizoic on Symplectoscyphus filiformis ( Allman, 1888) ; two gonothecae occur: one mature, given off from the stem (MHNG-INVE-86205), and one immature, borne of stolon. France, Brittany, collected in 2011, HRG-0566: fertile colony of Phialella quadrata (Forbes, 1848) , on seaweed.

Remarks. There are numerous subantarctic records1 assigned to Campanulina chilensis Hartlaub, 1905 , most of them based on sterile material, except for some rare instances where fertile specimens were encountered.

On one hand, several accounts ( Leloup 1974, Blanco et al. 2000, Galea 2007) describe and depict gonothecae that are morphologically indistinguishable from those of European specimens of P. quadrata (Forbes, 1848) (see Fig. 1 I, J). On the other hand, Naumov & Stepanjants (1962) and Stepanjants (1979) found fertile specimens with longitudinally ridged gonothecae, similar to those occurring in the present material.

Two gonothecae, one immature and another mature, provided with 10 and 9, respectively, rounded longitudinal ridges ( Fig. 1 G, H), were found in the present material. The mature specimen is 1300 µm long and 500 µm wide, and contains two medusa buds, the proximal one being the youngest. Its size exceeds that given (600–650 µm long and 400–430 µm wide) by Naumov & Stepanjants for their material from off New Zealand, though both exhibit the same longitudinal ridges, suggesting that they are most probably conspecific.

Despite the opinion expressed by a number of authors [primarily Hartlaub (1905), but also Vervoort (1972), for example], claiming a reliable distinction between C. chilensis and P. quadrata based on features of the trophosome alone2, it appears that one is not distinguishable from the other. The supposed differences are further confounded by the lack of knowledge of both the gonothecae and the medusa of Hartlaub’s species.

Although records of the medusa of P. quadrata are reliably documented from Chile ( Fagetti 1973, Palma et al. 2007, Galea 2007), only rearing experiments and molecular studies could test the relationships between the benthic and planktonic stages occurring in the country, as well as with their European counterpart. For the time being, fertile hydroids from Chile with smooth-walled to slightly undulated gonothecae are provisionally included in the synonymy of P. quadrata , as did Galea (2007).

Conversely, the hydroids bearing longitudinally folded gonothecae are thought to belong to a different congener. At least another species of Phialella occurs along the Patagonian coast and around the Falkland islands, viz. P. falklandica Browne, 1902 , but it is known exclusively from its medusa stage (see Galea 2007). It could be the case that the present hydroid and the medusa of P. falklandica are synonymous but, in the absence of rearing experiments or genetic comparison, there is little evidence, besides the restricted geographical occurrence in the subantarctic, to support this hypothesis.

Distribution in Chile. The present record is from Isla Tres Hermanas.

World records. Since this hydroid could not be linked with certainty to the medusa of P. falklandica , the geographical distribution of the latter could not be evaluated properly.

Figures

FIGURE 1. A, B: Hebella cf. scandens (Bale, 1888) — hydrotheca (A); gonotheca (B). C ‒ D: Hebella striata Allman, 1888 — hydrotheca (C); gonotheca (D). E, G, H: Phialella? falklandica Browne, 1902 — portion of erect stem (E) compared with that of P. quadrata (Forbes, 1848) (F); gonotheca seen laterally (G) and apically (H), compared with those of P. quadrata (I, stolonal; J, borne of stem). K, L: Silicularia? bilabiata (Coughtrey, 1876) — two hydrothecae (K); female gonotheca (L). M ‒ O: Silicularia rosea Meyen, 1834 — two hydrothecae (M) compared with specimens from Tristan da Cunha assigned to S. hemisphaerica (Allman, 1888) (P); female (N) and male (O) gonothecae, compared to homologous gonothecae (Q and R, respectively) from Tristan. S: Halecium corrugatissimum Trebilcock, 1828 — small stem with female gonotheca. Scale bars: 300 µm (A, B, E, F, S), 500 µm (C, D, G ‒ J), and 1 mm (K ‒ R).