Heterocoryne caribbensis Wedler & Larson, 1986

Maggioni, Davide, Schuchert, Peter, Arrigoni, Roberto, Hoeksema, Bert W., Huang, Danwei, Strona, Giovanni, Seveso, Davide, Berumen, Michael L., Montalbetti, Enrico, Collins, Richard, Galli, Paolo & Montano, Simone, 2021, Integrative systematics illuminates the relationships in two sponge-associated hydrozoan families (Capitata: Sphaerocorynidae and Zancleopsidae), Contributions to Zoology 90, pp. 487-525 : 508

Heterocoryne caribbensis Wedler & Larson, 1986

Heterocoryne caribbensis Wedler & Larson, 1986: 75 , figs. 2 a-e; pl. 1 figs. 4–6 ; Galea, 2013: 9, pl. 1, figs. G-I; fig. 2m ; Maggioni et al. 2017: 737.

Examined material: Sample STE001, Sint Eustatius, 07/06/2015, polyps in ethanol. – Sample STE002, Sint Eustatius, 08/06/2015, polyps in ethanol. – Sample STE003, Sint Eustatius, 09/06/2015, polyps in ethanol. – Sample STE011, Sint Eustatius, 12/06/2015, polyps in ethanol and formalin. –Sample STE014, Sint Eustatius, 13/06/2015, polyps in ethanol and formalin. – Sample STE018, Sint Eustatius, 13/06/2015, polyps in ethanol. – Sample STE028, Sint Eustatius, 15/06/2015, polyps in ethanol and formalin. – Sample STE043, Sint Eustatius, 19/06/2015, polyps in ethanol and formalin. – Sample STE046, Sint Eustatius, 20/06/2015, polyps in ethanol. – Sample MHNG-INVE-0069670, Guadeloupe, 03/12/2009, polyps in ethanol.

Description: Polyp. Colonies monomorphic, living in association with sponges ( figs. 6 A-C). Hydrorhiza tubular, branched, covered by perisarc and growing within sponge host. Pedicels unbranched, covered by a thin perisarc and by the sponge, the latter forming a cone-shaped cover around the base of the polyp ( fig. 6C ). Hydranth pyriform, up to 3.5 mm long, with variable diameter (160–630 Μm). Hypostome proboscis-like. One whorl of up to eight capitate tentacles below the hypostome and one whorl of up to 12 aboral capitate tentacles, each one provided with two or three partially-fused capitate tentacles on the proximal side ( figs. 6D, E). Each tentacle with a terminal, nematocyst-rich capitulum (diameter: 95–130 Μm), with a central inclusion (lost in fixed material). Tentacles up to 1 mm long. One fixed gonophore (eumedusoid) per polyp, among oral tentacles. Living hydranths with white hypostome, and a reddish gastric cavity ( figs. 6 A-C). Desmonemes, small and large stenoteles ( fig. 6F) occurring in the capitula, and rarely scattered in the hydrorhiza and in the hydranth.

Polyp cnidome. i) Desmonemes (undischarged: 8–9 × 4–5 Μm; discharged capsule: 7 × 4–5 Μm). ii) Large stenoteles (undischarged: 16–19 × 11–13 Μm; discharged capsule: 13–16 × 10–11 Μm). iii) Small stenoteles (undischarged: 10–12 × 6–7 Μm; discharged capsule: 8–9 × 5 Μm).

Distribution: Presumably endemic to the Caribbean Sea (currently only known from Guadeloupe, Martinique, Puerto Rico, Sint Eustatius, US Virgin Islands).

Remarks: The analysed colonies fully agree with the specimens analysed by previous authors, both in general morphology and cnidome composition ( Wedler & Larson, 1986; Galea, 2013). A minor difference is the presence, in some polyps, of four instead of three tentacles in the aboral whorl.

Figures

FIGURE 2 Sphaerocoryne bedoti. Polyps from A, B) Maldives and C) Sint Eustatius. D) Tentacles organisation. E) Close-up of a hydranth showing the typical colouration.F) Hypostome, with a nematocyst band (arrowhead).G) Living polyp detached from the host and trying to ingest a portion of the host sponge.H) Capitulum with a central inclusion.I) Polyp with medusa buds organised in clusters.J) Close-up of a polyps with medusa buds clusters arising from the red band area. K) Polyp with medusa buds showing reproductive exhaustion.L) Newly released medusa.M) Desmonemes (d) and small stenoteles (ss) from the polyp. N) Large stenoteles (ls) and small stenoteles (ss) from the polyp. O) Heteroneme from the polyp.Scale bars: A, B) 0.5 mm; C-G, I-K) 0.2 mm; H, L) 25 Μm; M-O) 5 Μm.

FIGURE 4 Euphysilla pyramidata. A, B, C) Polyps from the Maldives.D) Close-up of a hydranth showing the typical colouration. E) Hypostome with nematocysts (arrowhead). F) Longitudinal organisation of tentacles.G) Polyps with medusa buds. H) Large stenoteles (ls), small stenoteles (ss), I) desmonemes, and J) heteronemes from the polyp.K, L) Medusae with medusa buds.M) Detail of a bulb showing a reduced abaxial ocellum (arrowhead). Scale bars: A) 0.5 mm; B-D, G) 0.2 mm; E, F) 0.1 mm; H-J) 5 Μm; K, L) ~ 1 mm; M) ~ 0.3 mm.

FIGURE 5 Euphysilla sp. A, B) Ethanol-fixed polyps from Martinique.C) Desmonemes, D) small and E) large stenoteles, and F) heteronemes from the polyp. Scale bars:A, B) 50 Μm;C-F) 5 Μm.

FIGURE 6 Heterocoryne caribbensis. A-C) Polyps from Sint Eustatius. D, E) Tentacles partially fused. F) Large stenoteles (ls), small stenoteles (ss), and desmonemes (d). Scale bars: A-C) 0.5 mm; D, E) 0.1 mm; F) 5 Μm.