Obelia oxydentata Stechow, 1914

Mendoza-Becerril, María A., Murillo-Torres, Paulina, Serviere-Zaragoza, Elisa, León-Cisneros, Karla, Mazariegos-Villarreal, Alejandra, López-Vivas, Juan Manuel & Agüero, José, 2024, First records of hydroid epibionts on the introduced macroalga Gracilaria parvispora in the Mexican Pacific, Biodiversity Data Journal 12, pp. e 130248-e 130248 : e130248-

Obelia oxydentata Stechow, 1914

Materials

Type status: Other material. Location: locality: UABCS Pichilingue ; minimumDepthInMeters: 0.0; maximumDepthInMeters: 1.0; Event: year: 2021; month: 7; day: 15; habitat: middle and apical macroalgae regions; Record Level: dataGeneralizations: 28 ° C; 36 PSU

Notes

Fig. 6 f, Fig. 7

Type locality. United States: Virgin Islands, St. Thomas, Charlotte Amalie ( Stechow 1914).

Detailed description in Stechow (1914).

Taxonomic status. Accepted. AphiaID 766210.

Remarks. Colony morphology and size support evidence that this species differs from Obelia bidentata Clark, 1875 . Previous studies have discussed the reason for the recognition of the species, supporting the correct identification of the species ( Calder 2013, Calder 2019, Calder et al. 2019). This species is 1–60 mm tall, with predominant sizes from 1 to 10 mm ( Calder et al. 2019, Calder 2020, Calder et al. 2021). The species has been recorded in other localities of the Pacific: Coconut Island Reef, Hawaii; Salinas Yacht Club, Ecuador ( Calder 2020, Calder et al. 2021); and Oaxaca, Mexico ( Ramos-Morales et al. 2024). However, in this last record, the number of cusps (7-10 vs. 15-20) differs from the original description and further descriptions (cf. Stechow (1914), Calder et al. (2019), Calder (2020), Calder et al. (2021), Ramos-Morales et al. (2024), this study) and, in fig. 3 g of Ramos-Morales et al. (2024), the cuspids are unclear.

Diagnosis

Colonies monosiphonic, erect from 1-4 mm. Exoskeleton thin. Hydrothecal pedicel unbranched with a single hydrotheca at the distal end. Pedicel with 4-6 annulations (0.1- 0.05 mm length); branches arising from curved and short lateral apophysis. Hydrothecae (0.2 mm wide) straight to the slightly oblique diaphragm and bi-mucronate marginal cusps (16-20 in total). Cusps are slightly rounded, with deep, rounded spaces between each other, alternately differing slightly in depth. Without gonophores.

Figures

Figure 6. Hydrozoan epibionts. a Corydendrium sp.: part of hydrocaulus with two hydranths, scale equals 0.5 mm; b Ventromma halecioides: part of a hydrocaulus with the proximal end of a hydrocladium, hydrothecae, nematothecae, scale equals 0.3 mm; c Plumularia floridana: part of a hydrocaulus with the proximal end of a hydrocladium, hydrothecae and nematothecae, scale equals 0.1 mm; d Clytia linearis: part of hydrocaulus with hydrothecae, scale equals 0.8 mm; e Obelia cf. dichotoma: part of hydrocaulus with hydrothecae, scale equals 0.2 mm; f Obelia oxydentata: part of hydrocaulus with hydrothecae, scale equals 0.3 mm; g Obelia tenuis: part of hydrocaulus with a hydrotheca, scale equals 0.1 mm.

Figure 7. Obelia oxydentata. a colony, scale equals 0.5 mm; b part of hydrocaulus with hydrothecae; scale equals 0.1 mm.