Eucheumatopsis isiformis (C.Agardh) Núñez Resendiz, Dreckmann & Sentíes

Resendiz, María Luisa Núñez, Dreckmann, Kurt M., Sentíes, Abel, Wynne, Michael J. & Tejera, Hilda León, 2019, Marine red algae (Rhodophyta) of economic use in the algal drifts from the Yucatan Peninsula, Mexico, Phytotaxa 387 (3), pp. 219-240 : 231

Eucheumatopsis isiformis (C.Agardh) Núñez Resendiz, Dreckmann & Sentíes

Thallus cartilaginous, red pink or dark red, 15–50 cm in length, with cylindrical axes in cross section, 850–2200 μm in diameter. Main axes branching irregularly; branches and main axes with smooth margins or covered by numerous spine-like branches, arranged radially or alternately opposite, 1–2.5 mm in length ( Fig. 22 and 26 ). Multiaxial organization with a filamentous medulla and a pseudoparenchymatous cortex ( Fig. 23 ). Medulla composed of a dense mass of thick filaments, 1.8–6 μm in diameter, with numerous simple rhizoids. Inner cortex with six layers of stellate or rounded cells, 8.8–28.4 μm x 5.2–12 μm in diameter and 34–106 μm x 40–140 μm in diameter, respectively; outer cortex with two layers of ellipsoidal cells, 6–13 μm x 3.5–4.4 μm in diameter, markedly pigmented. Cystocarps developed on short laterals, with a single large central fusion cell from which diploid gonimoblast filaments radiate, 360–498 μm x 400–640 μm in diameter ( Fig. 24 ). Tetrasporangia zonately divided, 30–40 μm x 10–15 μm in diameter, embedded in the cortical cells, each sporangium arising laterally from a stellate basal cell ( Fig. 25 ).

Taxonomic comment: Until recently, this species had been previously treated as Eucheuma isiforme (C.Agardh) J.Agardh. From molecular evidence this genus was found to be paraphyletic ( Núñez Resendiz et al. 2019), so the new genus Eucheumatopsis Núñez Resendiz, Dreckmann & Sentíes was described to accommodate the species E. isiformis , this name is reinstated.

Figures

FIGURES 17–27. 17. Laurencia intricata. Medullary and cortical cells. Scale bar = 30 μm. 18–19. Yuzurua poiteaui var. gemmifera. 18. Habit.Scale bar = 3cm. 19. Pericentral, medullary and cortical cells. Scale bar = 120 μm. 20–21. Hypnea musciformis. 20. Habit. Scale bar = 2 cm. 21. Medullary and cortical cells. Scale bar = 120 μm. 22–26. Eucheumatopsis isiformis. 22. Habit. Scale bar = 4 cm. 23. Medullary filaments and cortical cells. Scale bar = 460 μm. 24. Mature cystocarp. Scale bar = 110 μm. 25. Tetrasporangium laterally attached. Scale bar = 25 μm. 26. Habit with smooth surfaces. Scale bar = 10 cm. 27. Meristotheca cylindrica. Habit. Scale bar = 4 cm.