Udotea looensis D. S. Littler & M. M. Littler

Type Locality:— USA, Looe Key, Monroe County, Florida.

Morphology:—Thalli to 5 cm tall, anchored on substrata by a small bulbous mass of entangled rhizoidal siphons. Stipe cylindrical 3–6 mm long, 1–3 mm in diameter, evident transition between the stipe and blade. Blade orbicular or reniform, green, as long (1–4.5 cm) as wide (1–4.7 cm), lower margin oval o reniform, multistratose with unistratose outer margin, ecorticate (no lateral appendages), slightly calcified, and clearly zonate (Figs. 56, 57).

Anatomy:—Blade siphons without lateral appendages, dichotomously branched, 35–55 μm in diameter, distance between each dichotomy varies from 700 to 1600 μm, supra dichotomous constrictions 30–40 μm length, 12–24 μm in diameter (Fig. 58). Stipe siphons adjacent to lateral appendages 40–60 μm in diameter, appendages peduncle 60–120 μm length, 20–40 μm in diameter. Appendages dichotomously branched 1–2 times, with abundant dichotomously lanceolate and apiculate apices (Fig. 59).

Reproduction:—Vegetative

Material examined:— MEXICO. Quintana Roo, Punta Mahahual, 10 September 2014, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23152. MEXICO. Quintana Roo, Punta Akumal, 16 December 2014, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23151. MEXICO. Quintana Roo, Rio Indio, 13 June 2014, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23154. MEXICO. Quintana Roo, El Zarzal, 19 May 1998, R. B. Searles, ENCB 17513. MEXICO. Quintana Roo, Faro de Bahía Espíritu Santo, 21 March 2009, J. A. Acosta Calderón, ENCB 20045. MEXICO. Yucatán, Progreso, 20 June 2014, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23153. MEXICO. Campeche, Playa Villamar, 25 January 2016, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23150. MEXICO. Campeche, Punta Xen, 20 June 2014, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23149. MEXICO. Campeche, Payucán, 27 October 2015, J. A. Acosta Calderón, L. E. Mateo Cid, A. C. Mendoza González, ENCB 23148. MEXICO. Campeche, Lerma, 19 September 1965, A. Vargas, ENCB 16732.

Geographic distribution:—Florida, Belize, Honduras, Panama, Bahamas, Cuba, Martinique, Mexico.

Habitat:—Rocky platforms with moderate surge and calcareous rocks in turbid waters. Subtidal to 5 m depth.

Comments:— Littler & Littler (1990) indicate that Udotea looensis shows morphologically similitudes to U. luna and U. spinulosa, however in this study morphological differences were found in the blade shape between them; for example U. looensis does not present lateral appendages in blade siphons like U. spinulosa, besides U. looensis differs from the other species by the lateral appendages’ shape. The diameter of blade siphons is smaller than those recorded in specimens from Florida (Littler & Littler 1990), but similar to those documented in specimens from Puerto Morelos, Quintana Roo, Mexico (Collado-Vides et al. 2009). This species has been recorded only for one site in Campeche (Mateo-Cid et al. 2013), but in in this paper the distribution of this species extended along the Campeche coast and is recorded for the first time for the Yucatan shore.