Bougainvillia macloviana Lesson, 1830

Peña Cantero, Álvaro L., 2015, Review of some little-known benthic hydroids (Cnidaria, Hydrozoa) from the Southern Ocean, Zootaxa 3972 (3), pp. 369-392 : 373-376

Bougainvillia macloviana Lesson, 1830

( Figs 4–5 )

Perigonimus maclovianus — Vanhöffen, 1910: 284 –286, fig. 10a–d; Stepanjants, 1972: 57, fig. 2; 1979: 11, pl. 1 fig. 2; Rees, 1956: 341, 346.

Cyanea Bougainvillii Lesson, 1830: 118 , pl. 14 fig. 3.

Hippocrene macloviana —Haeckel, 1879: 90, pl. 5 figs 1–2.

Bougainvillia macloviana — Schuchert, 2007: 224 –226, fig. 11.

Material examined. Gauss Deutschen Südpolar-Expedition 1901–1903 (Syntypes): ZMB Cni 14906, Gauss Station, 18.II.1903, 65°21'S – 86°06'E (Davis Sea), several stems, with gonophores, on Balanus tintinnabulum growing on the ship hull; ZMB Cni 14860, 18.II.1903, three gonophores; ZMB Cni 14843, Kerguelen, 26.I.1902, three stems or fragments, without gonophores, up to 12 mm high.

Description. Monosiphonic, branched stems, up to 12 mm high, with up to eight polyps and five gonophores per stem; unbranched stems, with a single distal polyp, also present ( Fig. 4 A). Stems usually tortuous and relatively long until first polyp. Stems little branched; branching irregular. Polyps relatively small (c. 480 µm high and c.170 µm in maximum diameter), with conical hypostome and a distal crown of about ten filiform tentacles ( Figs 4 A–D, 5A–D). Stem perisarc extending upwards around the base of the hydranth forming a pseudohydrotheca ( Figs 4 E, 5B–D).

Gonophores developing medusae ( Figs 4 F, 5E, F), up to 1000 µm high and up to 820 µm in maximum diameter (medusa c. 600 µm high and 670 µm in maximum diameter). Gonophores arising from small, cup-shaped pedicels of perisarc (50–230 µm high and 80–120 µm in maximum diameter) ( Fig. 5 E–G).

Measurements (in µm). Cnidome: Heteronemes [range 6.0–6.5 x 3.5–4.0, mean 6.2±0.2 x 3.9±0.2 (n=10); ratio, range 1.5–1.9, mean 1.6±0.1 (n=10)], desmonemes [range 3.5 x 2.0].

Remarks. Vanhöffen (1910) stated that polyps are provided with up to 16 tentacles, although usually less, and Stepanjants (1972, 1979) gives from eight to 16.

According to Vanhöffen (1910), large numbers of mature medusae of Hippocrene macloviana (= B. macloviana ) were present when the ship Gauss was in the Observatory Bay of Kerguelen and larvae likely settled on the ship's hull. Later, polyps developed in Antarctica , while wintering at Gauss station, until recognizable medusa buds of B. macloviana were observed, thus completing the cycle of the species. Vanhöffen (1910) considered that the young medusa, agreeing in the tentacles and the shape of the stomach, belonged to B. macloviana . Schuchert (2007: 226) pointed out that, “although there remains some uncertainty because a direct link of the adult medusa and the observed was not established, it is very probable that Vanhöffen’s conclusions were correct”.

Although I was not able to determine the heteronemes, Schuchert (1996) reported microbasic euryteles (7– 8 x 3–4 Μm) for adult medusae. He also reported desmonemes (6– 7 x 4–4.5 Μm) significantly larger than those observed in the type material examined.

The material examined from Kerguelen consists of three monosiphonic, branched stems or fragments, up to 12 mm high, with up to 16 polyps. Branching is irregular. The perisarc apparently reaches the base of tentacles. Perisarc and polyps are covered with tiny detritus and sand. Vanhöffen (1910) already stated that the perisarc of the Kerguelen material was studded with mud.

Ecology and distribution. Vanhöffen’s material from Kerguelen was found epibiotic on algae ( Macrocystis ) and invertebrates ( Halicarcinus , Mytilus and Patella ); the colonies from the Davis Sea were growing on dead barnacles attached to the ship hull. Stepanjants’ (1972) material was found on stones and hydroids ( Tubularia ), at depths from the tidal level to 15 m. Medusa buds were found in February ( Vanhöffen 1910) and from December to February (Stepanjants 1972).

According to Schuchert (2007), it is a species originally from the Southern Ocean that has extended its geographical distribution through the hydroid stage attaching to ships. Brown & Kramp (1939) already indicated that its presence in the North Sea was “undoubtedly due to casual transportation of the hydroid by ships” and according to Vannucci & Rees (1961: 71) “this would imply that the hydroid is eurythermic and euryhaline and thus able to withstand a long journey through the temperate and tropical Atlantic”. The medusa is widely reported from the Southern Hemisphere (e.g. Millard 1975; Schuchert 1996) and it is also known from Europe. Schuchert (2007) indicated that the polyp is only known from Kerguelen and South Africa ( Millard 1975), but Vanhöffen (1910) described it from the Davis Sea, in Antarctica , and Stepanjants (1972) found it from the same area.

Figures

FIGURE 4. Bougainvillia macloviana Lesson, 1830: A – D, polyps (D material from Kerguelen); E, detail of pseudohydrotheca (arrow); F, gonophore (arrow). Scale bar: 200 µm (A, F), 100 µm (B), 50 µm (C – E).

FIGURE 5. Bougainvillia macloviana Lesson, 1830: A, expanded polyp; B – D, retracted polyps showing pseudohydrotheca (arrows) (D material from Kerguelen); E – F, gonophores and cups of perisarc (arrows) (F showing medusa with radial canals); G, cup of perisarc. Scale bar: 250 µm (D – G), 125 µm (A – C).