Thuiaria polycarpa Kirchenpauer, 1884

Galea, Horia R., Försterra, Günter & Häussermann, Verena, 2007, Additions to the hydroids (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1650, pp. 55-68 : 61-66

Thuiaria polycarpa Kirchenpauer, 1884

(fig. 3A–H, fig. 4A–E, table 3)

Thuiaria polycarpa Kirchenpauer, 1884: 27 , pl. 13 fig. 3; Nutting, 1904: 65, pl. 8 figs 7–9; Bedot, 1925: 248. Parathuiaria polycarpa Leloup, 1974: 26 , fig. 21.

Material examined. Stn. PNH – 20.iii.2007, Chiloé Island, Puñihuil, 41°55.743’ S, 74°02.202’ W, 5 m, large pebbles: numerous stems with and without gonothecae ( MHNG INVE 54636).

Type locality. Valparaíso, Chile.

Description. Colonies erect, irregularly pinnate, up to 4 cm high, arising from a tubular, creeping and anastomosing stolon. Main stem upright, unbranched, rigid; indistinctly divided into internodes by slightly transverse constrictions of perisarc that vary in location; stem with a short, naked, basal portion, followed by main part bearing hydrothecae and cladia. Perisarc thick, brown, becoming thinner and colorless towards extremities of colony. Cladia arising at obtuse angle (45–60°) below stem hydrothecae, evenly spaced, pointing upwards, slightly directed toward anterior or posterior sides of stem, occasionally branched, with up to 2nd order branches. Both stem and cladia with two rows of hydrothecae, these generally strictly opposite, more rarely subopposite (compare figs 3E, 3F). Apical part of one hydrotheca not reaching base of next one above, pairs being slightly but distinctly separated. Hydrothecae long, tubular, with distal end bent outward; adnate for 2/3–3/4; abcauline wall with perisarc thickening below aperture; free adcauline wall slightly flared distally (fig. 3G). Hydrothecal aperture nearly round, parallel to stem axis, with circular, abcauline operculum; rim with no renovations. Hydranths with 16–18 filiform tentacles; presence of an abcauline caecum could not be checked in this preserved material.

Gonothecae generally arising below stem hydrothecae, but also present on cladia; pear-shaped; perisarc colorless, lateral wall with 4–5 slight undulations, never delimited by deep constrictions; a short apical collar present, provided with a variable number of conspicuous internal projections of perisarc; color brown, contrasting with rest of gonotheca; easily visible laterally (fig. 4C), but more obvious in frontal view (fig. 4D). Gonothecal aperture closed by a thin, transparent membrane. Gonothecae, female in present material, containing one large, oval egg. Male gonothecae not observed, unknown.

Remarks. Leloup (1974) erected the new genus Parathuiaria to accommodate those hydroids having hydrothecae in opposite pairs, a hydrothecal aperture devoid of an operculum (as in Synthecium Allman, 1872 ), and gonothecae arising below the stem hydrothecae (as in Thuiaria Fleming, 1828 ). However, inspection of our material revealed the presence of an abcauline opercular flap in the hydrothecae. The operculum is very thin, transparent, and most often totally adherent to the hydrothecal opening in fixed material. In some cases, the fixation process preserved the hydrothecae with the operculum opened, and its presence is incontestable in this case. It is possible that Leloup either overlooked the operculum or studied material in inadequate condition, especially that originating from station M102.

Moreover, this species was also briefly described by Nutting (1904), who placed it without reservation in the genus Thuiaria . Nutting did not give information about the operculum in his description of the species, but mentioned it in the diagnosis of the genus (p. 61). It seems reasonable to assume that an abcauline operculum was present in Nutting’s material.

We conclude that the genus Parathuiaria Leloup, 1974 should be regarded as a synonym of Thuiaria , and we reassign this species to it, as T. polycarpa Kirchenpauer, 1884 . However, the presence of an abcauline caecum in retracted hydranths, a distinguishing character of the genus Thuiaria (differentiating it from Salacia Lamouroux, 1816 ), could not be checked in the present material.

Previous descriptions of T. polycarpa ( Kirchenpauer 1884, Nutting 1904, Leloup 1974) have stated that both stem and branches were divided into internodes of varied length (comprising 2–3 pairs of hydrothecae) by means of transverse nodes, the last being only slightly marked. In our material too, the nodes are only very slightly marked, being more distinct in some parts of colonies and undetectable in others. This difference, as in other Sertulariidae , can certainly be attributed to intraspecific or environmental variation.

Nutting (1904) noted that the hydrothecae are in strictly opposite pairs. However, in his figure 8 (plate VIII), at least one pair has slightly subopposite hydrothecae. This situation was also found in our material (see fig. 3F). Leloup (1974) observed that hydrothecae in his specimens were slightly displaced toward the anterior face of the main stem, but in our case they are strictly coplanar (see fig. 3D).

Gonothecae were absent in material examined by Kirchenpauer (1884), as well as in Nutting’s (1904) specimens. They were briefly described for the first time by Leloup (1974).

Leloup (1974) raised the question of the synonymy between T. polycarpa and T. doliolum Kirchenpauer, 1884 , but the absence of gonothecae in the type material of the former prevented him from drawing a firm conclusion. In our opinion the two species seem to be separate, a conclusion supported by some arguments indicated in descriptions and figures given by Kirchenpauer himself. The most obvious difference relates to the shape of gonotheca. Those of T. polycarpa have slightly undulated walls, while those of T. doliolum possess ca 9–10 deep, transverse annuli ( Kirchenpauer 1884, pl. 14 fig. 4b). Moreover, in the latter species, gonothecae seem to arise only from the cladia (see p.117 and pl. 13 fig. 4), while in T. polycarpa they are borne mainly on the stem and only rarely on cladia (present observations). Still concerning the gonothecae, Kirchenpauer wondered why E. F. Pöppig (Leipzig), who collected the material and named both species, choose the name “ polycarpa ” (from the Greek words “Karpos” or “Carpus”, which mean fruit) to describe a specimen devoid of gonothecae. Additionally, the cladia in T. doliolum arise from the stem in opposite pairs and are unramified even in mature, fertile material, while in T. polycarpa they are either borne singly on one side of the stem or in opposite pairs, and may occasionally give rise to secondary branches. A final argument supporting the separation of these two concerns their geographical distribution, i.e. T. polycarpa was collected along the Pacific coast of Chile, while T. doliolum originates from the Cape of Good Hope, South Africa.

Hydroid epibionts. Campanulina pumila ( Clark, 1875) , Obelia geniculata ( Linnaeus, 1758) .

World distribution. Known only from Chile.

Records from Chile. Valparaíso ( Kirchenpauer 1884), Chacao Channel ( Leloup 1974), Puñihuil, Chiloé Island (present study).

Ecology. This species was previously found growing on pebbles at a depth of 40—100 m ( Leloup 1974). Our material was collected at a depth of 5 m, also on a substrate of pebbles (ca 20 cm of diameter each).

TABLE 3. Measurements of Thuiaria polycarpa Kirchenpauer, 1884 (in µm). 1Approximate dimensions.

Sertularia operculata Linnaeus, 1758: 808 ; Hincks, 1868: 263, pl. 54; Bale, 1884: 67, pl. 6 fig. 1, pl. 19 fig. 3; Allman, 1888: 61, pl. 30 figs 1, 1A; Hartlaub, 1905: 664, figs Y4, Z4, A5, B5, C5; Blanco, 1976: 38.

Amphisbetia operculata: Ralph, 1961: 775 , fig. 8I –K; Vervoort, 1972: 98; Leloup, 1974: 25; Millard, 1975: 251, fig. 83A–E; Cornelius, 1979: 254, fig. 6; Stepanjants, 1979: 62, pl. 11 fig. 1A–G; Morri & Boero, 1986: 58, fig. 36; Gili et al., 1989: 97, fig. 23A; El Beshbeeshy, 1991: 130, fig. 30; Cornelius, 1995b: 30, fig. 4; Vervoort & Watson, 2003: 109, fig. 21A–C; Bouillon et al., 2004: 177, fig. 95G–I; Vervoort, 2006: 264.

Dynamena operculata: Naumov & Stepanjants, 1962: 89 ; Naumov, 1969: 357, fig. 220, pl. 7 fig. 1.

Material examined. Stn. HER – 12.iii.2007, Raul Marin, Las Hermanas, 43°46.285’ S, 73°02.632’ W, 15 m: two young, sterile stems, 3.0 and 3.5 mm high, respectively ( MHNG INVE 54637), epizoic on Obelia dichotoma ( Linnaeus, 1758) .

Type locality. “ In Oceano, ” no distinct type locality specified ( Linnaeus, 1758).

TABLE 4. Measurements of Amphisbetia operculata ( Linnaeus, 1758) (in µm). 1Tip of outer spine to inner corner.

Remarks. The present material comprises two young stems, one with the hydrothecae subopposite (fig. 4F), the other with the hydrothecae alternate. For a recent description of this species, see Cornelius (1995b). World distribution. Widely distributed in temperate to tropical coastal waters, to latitude ca 55° in the Southern Hemisphere and ca 60° in the Northern ( Cornelius 1995b).

Records from Chile. Dungeness Point ( Hartlaub 1905), Chiloé Island, Chacao Channel, Gulf of Ancud, Gulf of Corcovado ( Leloup 1974), Raul Marin (present study).