Virescentia asiatica Aristya, Fontana, Pok, Necchi & Liu, 2024, sp. nov.
Creators: name: Aristya, Ganies Riza
name: Fontana, Silvia
name: Pok, Wai-Lun
name: Necchi, Orlando
name: Liu, Shao-Lun
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Plantae
Rhodophyta
Florideophyceae
Batrachospermales
Batrachospermaceae
Virescentia
Virescentia asiatica

description: 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.
GEOGRAPHIC DISTRIBUTION
Currently known from a few localities in Taiwan and Japan.
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).
description: Published as part of Aristya, Ganies Riza, Fontana, Silvia, Pok, Wai-Lun, Necchi, Orlando & Liu, Shao-Lun, 2024, Virescentia asiatica sp. nov. (Batrachospermales, Rhodophyta), a new freshwater red alga from East Asia, pp. 77-88 in Cryptogamie, Algologie 45 (7) on pages 82-84, DOI: 10.5252/cryptogamie-algologie2024v45a7, http://zenodo.org/record/13646701