Dynamena disticha (Bosc, 1802)

Estrada-González, Mariae C., Agüero, José & Mendoza-Becerril, María A., 2023, Medusozoans from the Mexican Pacific: a review based on historical literature and recent observations, Journal of Natural History 57 (1), pp. 784-853 : 829-830

Dynamena disticha (Bosc, 1802)

( Figure 7I, J )

Material examined

3 colonies, polyp, without gonophores; Punta Diablo, La Paz Bay , Baja California Sur, 24.316°, 110.340°W; depth 0–1 m; 7 May 2017; on rock; ECO-CH-Z 11753 . – Several colonies, polyp, without gonophores; Punta Los Muertos, Baja California Sur, 24.248°N, 110.150°W; depth 1–2 m; 20 July 2018; on the alga Gracilaria sp .; ECO-CH-Z 11767 . – 1 colony, polyp, without gonophores; El Califín, La Paz Bay , Baja California Sur, 24.268°N, 110.616°W; depth 0.5–2 m; 25 May 2018; on the alga Sargassum horridum ; ECO-CH-Z 11782 . – Several colonies, polyp, without gonophores; El Califín, La Paz Bay , Baja California Sur, 24.268°N, 110.616°W; depth 0.5–2 m; 4 September 2018; on the alga Codium brandegeei ; ECO-CH-Z 11781 . – 1 colony, polyp, without gonophores; Agua de Yepiz, La Paz Bay , Baja California Sur, 24.288°N, 110.630°W; depth 0–1 m; 24 June 2018; on the alga Sargassum sp .; ECO-CH-Z 11786 .

Identification (after Calder 1991; Miranda et al. 2011)

Colonies erect; hydrocaulus monosiphonic, unbranched, divided into internodes by oblique nodes. Basal athecate separated from the thecate internodes by an oblique node; thecate internodes with 1–3 pairs of opposite hydrothecae. Hydrothecae only contiguous in front of internodes, separated across back, parts of adcauline wall nearly straight and parallel to internodes, free part convex, curved outwards; abcauline wall concave except for basal part. Hydrothecal margin with two large rounded lateral cusps and a smaller median adcauline cusp. Operculum formed by two valves, a large abcauline and a smaller adcauline.

Distribution

Previously recorded on the west coast of the Gulf of California in Baja California and Baja California Sur ( Fraser 1938b, 1948; Mendoza-Becerril et al. 2020) and for the rest of the gulf in Nayarit ( Fraser 1948). In the MP, it has been recorded off the coasts of Baja California, Baja California Sur, Guerrero, and Oaxaca ( Fraser 1938a, 1938c, 1948).

Remarks

A colony of the labelled sample PD_6 exhibited second-order branching, a morphological variation previously recorded for D. disticha ( Calder 1991) .

Figures

Figure 7. (A, B) Ventromma halecioides (Alder, 1859): A, hydrocaulus; B, hydrotheca. (C, D) Monotheca flexuosa (Bale, 1894): C, hydrocaulus; D, hydrotheca. (E, F) Plumularia floridana Nutting, 1900: E, hydrocaulus; F, hydrotheca. (G, H) Dynamena crisioides Lamouroux, 1824: G, colony; H, hydrotheca. (I, J) Dynamena disticha (Bosc, 1802): I, colony; J, hydrotheca. (K, L) Pasya quadridentata (Ellis and Solander, 1786): K, colony; L, gonotheca. Scale bars: A, H, I, K, L = 500 μm; B, D = 100 μm; C, E = 250 μm; F, J = 200 μm; G = 1 cm. Drawings made by Nicholas Bezio.