Ulva tepida Y.Masakiyo & S.Shimada (2014: 11)

Ng, Yu Fei & Huang, Danwei, 2024, Species diversity and phylogeny of the green macroalga Ulva (Ulvophyceae, Chlorophyta) in Singapore, Phytotaxa 662 (1), pp. 67-79 : 72

Ulva tepida Y.Masakiyo & S.Shimada (2014: 11)

Material examined:— SINGAPORE. Changi : Changi Beach Carpark 1, 16 July 2022, NYF220710 ( SING) ; East Coast : East Coast Park Carpark G, 18 July 2022, NYF220747 , NYF220754 ( SING) .

Description:—Thallus monostromatic, in the shape of tubular filaments, smooth with the width decreasing towards the base ( Fig. 5B ). Thallus base with second-order branching ( Fig. 5C ). Filaments 1–14 mm in length, filament apices 0.2–0.9 mm in width (n = 6), filament bases 8–72 μm in width (n = 6). Surface cells are rectangular or irregularly shaped, 7–19 μm in length and 4–11 μm in width (n = 20) ( Figs. 5D–E ). Chloroplast occupies most of the cell periphery, with 0–2 pyrenoids. In transverse section, thallus 16–18 μm in width (n = 5), cell shape is rectangular, 12–14 μm in length and 8–11 μm in width (n = 6), with parietal chloroplasts ( Fig. 5F ).

Distribution in Singapore: Changi Point Ferry Terminal and East Coast Park Carpark G.

Habitat:—Attached to upper intertidal rocks ( Fig. 5A ).

Remarks:—New species record for Singapore. Because U. tepida is smaller than most other Ulva species, it is likely that this species had been missed during previous surveys and collections. Ulva tepida has similar gross morphology to the previously recorded U. compressa , U. flexuosa and U. intestinalis due to its filamentous thalli. The tuf A phylogeny showed moderate ML and full BI support for the U. tepida / Ulva sp. 5 ( Vietnam) clade (85/1) ( Fig. 2 ), while the U. tepida clade was weakly supported in the ITS tree (67/0.67) (Supplementary File 3). There was no phylogenetic support for the U. tepida clade in the rbc L tree (Supplementary File 4). Even though Ulva sp. 5 from Vietnam is nested within the Ulva tepida clade, the former is distinguishable from U. tepida as it lacks pyrenoids ( Tran et al. 2023).

Figures

FIGURE 2. Phylogenetic tree of Ulva with Umbraulva kaloakulau as outgroup based on tufA DNA sequences. Bootstrap values ≥ 50 for maximum likelihood and posterior probability values ≥ 0.8 for Bayesian phylogenetic analyses are stated above branches. Samples sequenced from this study are coloured in green (U. ohnoi), blue (U. meridionalis), and red (U. tepida).

FIGURE 5. Morphology of Ulva tepida (NYF220747). A. In-situ rocky habitat. B. Herbarium voucher. C. Base of U. tepida. D. Surface cells. E. Thallus filament. F. Cells in transverse section.