Eucheumatopsis sanibelensis E.S.Peterson, C.W.Schneider et G.W.Saunders, 2020

Peterson, Elias S., Schneider, Craig W. & Saunders, Gary W., 2020, Eucheumatopsis sanibelensis sp. nov. from the Gulf coast of Florida, USA, Phytotaxa 440 (3), pp. 215-224 : 220-221

Eucheumatopsis sanibelensis E.S.Peterson, C.W.Schneider et G.W.Saunders , sp. nov. ( Figs 2–4 )

Description: Plants rosy-red, saxicolous, with cartilaginous, terete to compressed axes to 24 cm tall, attached by discoid holdfasts; axes not percurrent, slender to greatly thickened, gradually tapering from base to apex, 1–3 mm diam. prior to first branches, alternately to irregularly branched, typically from four to seven orders, occasionally sub-pinnate or secund, with or without adventitious branches, ultimate spine-like branches lacking ( Fig. 2 ); branches basally constricted or tapering to the bases, apices acute, some slightly curved; medulla composed of densely tangled filaments, 2–7 µm diam., giving rise to the radially organized inner cortex of 3–4 layers; innermost cortex composed of hyaline, stellate, non-pigmented, thick-walled cells, 68–170 µm in diam. and 92–200 µm long, middle cortex of cells 26–50 µm in diam. and 25–53 µm long, tapering to the outer cortex of 1–2 layers of densely pigmented, elongate cells 2–7 µm in diam. and 6–16 µm long ( Figs 3, 4 ); tetrasporangia and gametangia unknown.

Diagnosis: Differing from congener Eucheumatopsis isiformis in its overall size, the lack of ultimate spine-like branches, the total number of cortical cell layers, the size of inner and outer cortical cells, and density of the medullary filaments. Differing from the similar Agardhiella subulata in its greater orders of branching and smaller outer cortical cell diameter.As these two species have overlapping morphologies ( Table 2) and distributional ranges, the new species remains best differentiated by its genetic markers.

Holotype: FLORIDA, USA – Craig W. Schneider (CWS) 13-4-1 [ FL009 ], 19 Mar. 2013, Lee Co., lighthouse at eastern end of Sanibel I., 26˚27’15.92 ” N, 82˚00’57.55” W, vic. fishing pier in drift with Sargassum [deposited in UNB, GenBank COI-5 P – MN941986 , LSU – MN941976 , rbc L – MN941997 ] ( Fig. 2 ) ; Isotypes deposited in MICH, NY, US, Herb. CWS .

Additional collections: FLORIDA, USA – CWS 15-1-7 [FL 033, 034], 19 Mar. 2015, loc. cit., 26˚27’15.37” N, 82˚00’53.09” W, in drift ; CWS 16-2-4b [ FL 042 ] 15 Mar. 2016, loc. cit., 26˚26’59.46” N, 82˚01’03.48” W, in drift. Etymology: Named for the nearshore Sanibel Island where it has been collected on the Gulf of Mexico coast of Florida in the western Atlantic Ocean .

Figures

FIGURES 2–4. Eucheumatopsis sanibelensis E.S.Peterson, C.W.Schneider et G.W.Saunders, sp. nov. [CWS 13-4-1]. 2. Holotype specimen. Scale bar = 5 cm. 3. Axis cross-section near apex. Scale bar = 50 µm. 4. Surface view of blade showing outer cortical cell arrangement. Scale bar = 50 µm.