Hydrocorynidae, Rees, 1957

Mendoza-Becerril, María A., Estrada-González, Mariae C., Mazariegos-Villarreal, Alejandra, Restrepo-Avendaño, Luisa, Villar-Beltrán, Rogelio D., Agüero, José & Cunha, Amanda F., 2020, Taxonomy and diversity of Hydrozoa (Cnidaria, Medusozoa) of La Paz Bay, Gulf of California, Zootaxa 4808 (1), pp. 1-37: 7

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Hydrocorynidae   sp.

Figs. 3 View FIGURE 3 C –G

Material examined. Polyp—PB6_6, sampling site 2 (3), on rock, Cirripedia, and Bryozoa.

Description. Colonies small, unbranched, arising from an encrusting base, from 0.6 to 1.2 cm high, with an amorphous hydrorhizal plate with 8–17 hydranths. Hydranths from 0.4 to 1.1 mm high; capitate tentacles 10–13 in number, arranged in two close whorls (0.3–0.4 mm long). Soft and smooth exoskeleton. Gonophore origin on unbranched pedicels off the hydrorhiza, 0.01 to 0.2 mm long; pedicel 0.03 to 0.08 mm long.

Nematocysts (length x diam.). Stenotele (9.3–17.0 x 6.4–10.5 µm) and microbasic euryteles (10.9–12.7 x 4.3– 4.8 µm).

Remarks. Genera of this family have often been distinguished based on whether gonophores remain fixed or are liberated as free medusa. Their polyp is notable for its large size, reaching up to 6 cm high in a state of expansion ( Rees 1957). Mangin (1991) distinguishes Samuraia   from Hydrocoryne   because the former has gonophores originating on unbranched pedicels on the hydrorhiza and medusoids with gonads surrounding the manubrium; it lacks tentacles, ocelli, mouth, and peduncle; and has irregular, knobby radial canals. In the material examined, we could not observe mature gonophores or medusoids, and the polyps were tiny and probably juveniles. As a result, the morphology of the material examined could be related to either Samuraia   or Hydrocoryne   , especially if we consider the following characters: number of tentacles of the hydranth (10–13 vs. 11–22 and 30–70 in Samuraia   and Hydrocoryne   , respectively), tentacles arranged in two close whorls and length of extended tentacles (0.3–0.4 mm vs. 0.4–0.6 and 0.5–3.4 mm in Samuraia   and Hydrocoryne   , respectively), size of the hydranths (0.4–1.1 mm vs. 30 and 60 mm long in Samuraia   and Hydrocoryne   , respectively), and size of the colony (8–17 vs. 1–3 and 2–20 hydranths/colony in Samuraia   and Hydrocoryne   , respectively).

Distribution. Family reported in the Pacific and Atlantic Oceans ( Morandini et al. 2009; Du et al. 2013). In Mexican Pacific, it has been registered in Sonora (Pelican Point) ( Mangin 1991) and Guerrero (Acapulco) ( Bigelow 1909).