Virescentia asiatica sp. nov. (Batrachospermales, Rhodophyta), a new freshwater red alga from East Asia Author Aristya, Ganies Riza Faculty of Biology, Universitas Gadjah Mada, Yogyakarta 55281 (Indonesia) Author Fontana, Silvia Department of Life Science & Center for Ecology and Environment, Tunghai University, Taichung 40704 (Taiwan) Author Pok, Wai-Lun Department of Life Science & Center for Ecology and Environment, Tunghai University, Taichung 40704 (Taiwan) Author Necchi, Orlando Zoology and Botany Department, São Paulo State University, Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054 - 000 (Brazil) Author Liu, Shao-Lun Department of Life Science & Center for Ecology and Environment, Tunghai University, Taichung 40704 (Taiwan) shaolunliu@gmail.com text Cryptogamie, Algologie 2024 2024-08-27 45 7 77 88 https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/algologie2024v45a7.pdf journal article 10.5252/cryptogamie-algologie2024v45a7 a1145fc5-2e7a-4aee-925d-da4b7c299fd5 1776-0984 13646701 Virescentia asiatica sp. nov. ( Fig. 3 A-M; Table 2 ) TYPE MATERIAL . — Taiwan • Taoyuan , Longtan District , Longping Road , irrigation ditch in front of “HuangNiTangFuDe” Temple ; 24°53’07.483”N , 121°13’53.234”E ; 17.III.2015 ; Shao-Lun Liu ; holotype : HAST-146271 ; GenBank: MH835533 , MH835534 ( rbc L) and OR885897 (COI-5P) . ETYMOLOGY . — The epithet “asiatica ” refers to the currently known distribution ( Japan and Taiwan). DESCRIPTION The gametophyte is monoicous. The thallus reaches approximately 2 cm in height, displaying a black or dark brown coloration with a subtle mucilage ( Fig. 3A, B ). The branches of the thallus are strongly curved, showing an irregular and abundantly curved branching pattern (arrowheads in Fig. 3A, B ). The terminal and older branches exhibit sparse fascicles, indicative of their deciduous nature during growth ( Fig. 3A, B ). The well-developed whorls are obconic or pearshaped, measuring between 220 and 1060 µm in diameter ( Fig. 3 B-D), usually appearing distinct and contiguous or occasionally separated ( Fig. 3 B-D). Primary fascicles are composed of 7-14 cells, straight and display dichotomous branching ( Fig. 3C ). Secondary fascicles consist of 6-8 cells and cover the entire internode ( Fig. 3D ). In both primary and secondary fascicles, proximal cells are ellipsoidal or cylindrical, while distal cells are ellipsoidal or obovoidal ( Fig. 3E ). Spermatangia are 5-8 µm in diameter, are spherical or obovoidal and found terminally or laterally on primary and secondary fascicles ( Fig. 3E ). Carpogonial branches are relatively short and straight ( Fig. 3F, G, I ), consist of 3-4 disc-shaped or barrel-shaped cells ( Fig. 3F ), originating from periaxial cells of primary fascicles ( Fig.3J ) with several short-branched involucral filaments comprising 1-4 cells ( Fig. 3H ). The carpogonium is 65-80 µm long ( Fig. 3 F-J), with trichogynes stalked and varying in shape such as cylindrical, clavate, or ellipsoidal ( Fig. 3 F-J). Carposporophytes are hemispherical and dense, axial, and either lower than or equal to the whorl radius with an average of 1-2 (occasionally up to 4) per whorl ( Fig. 3D, K ), and dimensions ranging from 140 to 800 µm in diameter and 100 to 750 µm in height ( Fig. 3D, K ). Gonimoblast filaments consist of 3-6 cylindrical cells ( Fig. 3L ). Carposporangia are obovoidal and their dimensions when mature are 34-40 µm in length and 18-20 µm in diameter ( Fig. 3L, M ). HABITAT AND SEASONALITY The sample was collected on March 17, 2015 , during the Spring season. We discovered the plant growing on stones within the sun-exposed section of the stream, coexisting with the gametophyte of S. dispersa , which was notably abundant and widespread in that area at the time of collection. Prior to the first collection of V. asiatica sp. nov. , we conducted monthly visits to the type locality over a year and a half (from February 2012 to October 2013 ), as a part of an ecological survey monitoring the population dynamics of an introduced freshwater red alga M. macrospora at the same site ( Fontana et al. 2022 ). Throughout this period, there had been no visible growth of V. asiatica sp. nov. It was detected for the first time during a later visit on March 17, 2015 , where it appeared in extremely limited numbers, with only a single thallus located. The ecological conditions at the type locality in early spring 2013 (i.e., during the same season of the later V. asiatica sp. nov. collection) were 23.1°C of water temperature with a pH of 7.82. FIG . 3. — Morphological features of Virescentia asiatica sp.nov. : A , in situ gross morphology with diminutive holdfast ( arrow ). Arrowheads indicate the curvature of the branch; B , habit of the thalli with diminutive holdfast ( arrow ). Arrowheads indicate the curvature of the branch; C , contiguous barrel-shaped whorls formed by primary fascicles at nodes on the branch; D , branch showing whorls with hemispherical carposporophyte ( arrow ) at nodes and abundant secondary fascicles covering the entire internode; E , spherical spermatangia ( arrow ) at the tips of the fascicle cells; F , young straight carpogonial branch ( double arrowhead ) with carpogonium and unstalked ( arrowhead ) trichogyne ( arrow ); G , straight mature carpogonial branch with carpogonium ( double arrowhead ), cylindrical and stalked ( arrowhead ) trichogyne ( arrow ); H , compact and dense involucral branch; I , compact involucral branch with carpogonium and clavate trichogyne ( arrow ); J , carpogonial branch with trichogyne ( arrow ) arising from the basal periaxial cells of primary fascicle; K , four hemispherical carposporophyte at nodes; L , obovoidal carposporangia ( arrows ) at the tips of the gonimoblast filaments; M , close-up view of obovoidal carposporangia ( arrows ) at the tips of the gonimoblast filaments ( arrowheads ). Scale bars: A, 5 mm; B, 1 mm; C, 200 μm; D, K, 300 μm; E, F, M, 40 μm; G-I, 20 μm; J, L, 80 μm. GEOGRAPHIC DISTRIBUTION Currently known from a few localities in Taiwan and Japan . TABLE 2. — A list showing the morphological comparison between Virescentia asiatica sp. nov. and other known species of Virescentia (Sirodot) Necchi , D.C.Agostinho & M. L .Vis.

Character	Virescentia asiatica	Virescentia crispata	Virescentia guangxiensis	Virescentia	Virescentia gulbenkiana helminthosa	Virescentia viride-americana	Virescentia viride-brasiliensis	Virescentia vogesiaca
Thallus branch type	Curve	Straight	Straight	Straight	Straight	Straight	Straight	Straight
Whorl	Shape	Contiguous, obconic or pear-shaped	Contiguous, obconic, or pear-shaped	Contiguous or separated, barrel-shaped, or spherical	Contiguous or separated, barrel-shaped, or spherical	Contiguous or separated, barrel-shaped, spherical or pear-shaped	Contiguous or separated, barrel-shaped, spherical or pear-shaped	Contiguous or separated, barrel-shaped, spherical, pear-shaped or obconic	Contiguous or separated, barrel-shaped, obconic, pear-shaped or spherical
	Diameter (μm) Primary fascicle cell no.	220-1060 7-14	150-350 6-13	250-350 5-7	430-810 8-13	300-800 8-15	280-940 8-19	280-1100 7-18	340-700 7-14
Fascicle shape	Straight	Curved	Straight	Straight	Straight	Straight	Straight	Straight
Carpogonial branches shape	Straight	Slightly curved	Straight	Straight	Slightly curved	Straight	Straight	Straight
Carpogonium	Length (carpogonium basal cell + trichogyne)	65-80	54-75	Not observed	20-39	40-79	(30-)40-77	40-110	20-45
	Composed cell number (composed cell no. in twisted)	3-4	3-4	Not observed	3-12	3-11	1-7	1-7	(4-)8-20
Shape	Disc or barrel-shaped	Disc- or barrel-shaped	Not observed	Disc-shaped	Disc-shaped	Disc-shaped	Disc-shaped	Disc-shaped
Carposporophyte	No. per whorl Diameter Height Shape	1-2(-4) 140-800 100-750 Hemispherical	1-2 140-300 100-250 Spherical	Not observed Not observed Not observed Not observed	1-3 120-300 60-150 Cylindrical	1-2 150-420 100-320 Hemi-spherical	1-2 (130-)140-390 70-200(-240) Spherical	1-2 200-550 100-300 Spherical	1-2 140-330 95-175 Spherical
Gonimoblast filament	Cell layer no. Shape	3-6 Cylindrical	3-5 Cylindrical	Not observed Not observed	2-5 Cylindrical	3-7 Cylindrical	3-5 Cylindrical	3-6 Cylindrical or barrel-shaped	4-7 Cylindrical or ellipsoidal cells
Carposporangium	Length (μm) Diameter (μm) Shape	34-40 18-20 Obovoid	14-30 8-10 Clavate or obovoid	Not observed Not observed Not observed	10-18 6.5-10 Obovoid or pear-shaped	14-20.5 8.5-12.5 Obovoid or pear-shaped	15-24 8.5-12 Obovoid or pear-shaped	19-35 10-24 Obovoid, pear-shaped or ellipsoidal	13-19 8.5-13 Obovoid
Trichogyne	Shape	Stalked, cylindrical, clavate or ellipsoidal	Stalked, cylindrical	Not observed	Stalked, clavate or cylindrical	,Stalked, cylindrical, sometimes bifurcated or with knobs	Stalked, clavate or cylindrical	Stalked, clavate or sup-cylindrical	Stalked, clavate or ellipsoidal
Spermatangia	Diameter (μm) Shape	5-8 Spherical or obovoid	6-8 Spherical or obovoid	Not observed Not observed	4-6 Spherical	5-7 Spherical	4-8 Spherical	4-9 Spherical or obovoid	5-8 Spherical
	Growth placement	Primary or Secondary fascicle	Primary or Secondary fascicle	Not observed	Primary fascicle	Primary or secondary fascicle	Primary or Secondary fascicle	Primary or secondary fascicle	Primary fascicle or secondary fascicle
Special expansion cells	Absence	Absence	Presence	Absence	Absence	Absence	Absence	Absence
References	This study	Necchi et al. (2018)	Fang et al. (2021)	Necchi et al. (2018)	Necchi et al. (2018)	Necchi et al. (2018) ; Krueger-Hadfield et al. (2024)	Necchi et al. (2018)	Necchi et al. (2018)

REMARKS Compared to other known Virescentia species , V. asiatica sp. nov. has small thallus size (although may be attributable to the age of the material collected) with apparently curved branches ( Table 2 ). Apart from its diminutive size and the curvature of the branches, few other morphological traits were found to distinguish this species from others in the genus Virescentia . Notably, unlike V. asiatica sp. nov. , V. crispata and V. helminthosa have slightly curved carpogonial branches and V. guangxiensis has distinct expansion in the penultimate cells of primary or secondary fascicles ( Table 2 ).