Sirodotia assamica Necchi, Rossignolo, Yasmin, West and Ganesan, 2020

Rossignolo, Natalia L., Yasmin, Farishta, West, John A., Ganesan, E. K. & Junior, Orlando Necchi, 2020, Molecular and morphological evidence for a new species in the genus Sirodotia (Batrachospermales, Rhodophyta) from the State of Assam, India, Phytotaxa 437 (3), pp. 121-134 : 125

Sirodotia assamica Necchi, Rossignolo, Yasmin, West and Ganesan sp. nov. ( Fig. 3 a–h )

Description. Plants dioecious or monoecious, irregularly branched; apices straight; apical cells protruse. Whorls dense or loose, pear-shaped or obconical, contiguous, 400–665 µm in diameter. Internodes 547–1177 µm in length. Cortical filaments well-developed, with two to four layers. Primary fascicles straight, 6–12 cell storeys; proximal cells cylindrical or ellipsoidal, 17–42 µm in length, 7–13 µm in diameter; distal cells obovoidal, ellipsoidal or sub-spherical, 9–14 µm in length, 5–9 in diameter; di- or trichotomously branched. Secondary fascicles abundant, covering the entire internode, equal to or shorter than the length of the primary fascicles.

Spermatangia spherical, terminal or sub-terminal, arranged in clusters on primary or secondary fascicles, 6–8 µm wide. Carpogonial branches straight or slightly curved, short, 7–23 µm long, composed of 1–5(–6) disc- or barrel-shaped cells, 5–9 µm long, 4–8 µm wide, arising from periaxial cells of primary fascicles; involucral filaments few and short, composed of 1–3 short-cylindrical or ellipsoidal cells. Carpogonia asymmetrical, with a hemispherical protuberance on one side of the basal portion, 37–64 µm in length, 10–16 µm in diameter; trichogynes elongate-cylindrical, ellipsoidal or lageniform, sessile or pedicellate.

Carposporophyte diffuse with no definite shape. Gonimoblast initial developing from protuberant side of the carpogonium; gonimoblast filaments prostrate, creeping among fascicles or cortical filaments along the main axis; with erect branches of 1–4 cylindrical or ellipsoidal cells, producing carposporangia at the tips; carposporangia obovoidal or sub-spherical, 11–14 µm in length, 6–8µm in diameter.

Holotype: India, Assam, Nagaon District, Chapanalla; 26º19’13.7” N, 92º10’16.5” E; coll. F. Yasmin , 25.ii.2019 ( SJRP 32584 ) . Holotype specimen not sequenced.

Paratypes: India, Assam, Sonapur, Tegheria ; 26º05’52” N, 92º02’02” E; coll. F. Yasmin , 24.ii.2019 ( SJRP 32583 ) ; India, Assam, Nagaon District , Chapanalla ; coll. O. Necchi Jr. et al., 23.ii.2018 ( SJRP 32585 ) .

DNA sequences: COI-5 P ( MN 508239, MN 508240) and rbc L ( MN 496129, MN 496130).

Remarks: Sirodotia assamica most distinguishing feature is the occurrence of spermatangia arranged in clusters, thus far described only for S. huillensis . However, these two species are genetically highly divergent (4.5%–5.0% for rbc L and 9.6%–10.1% for COI-5P). Sirodotia assamica is most closely comparable to S. cirrhosa , S. delicatula and S. sinica based on the vegetative and reproductive characteristics and the occurrence in or near India ( Table 2). Sirodotia assamica differs from S. sinica in having longer carpogonia (37–64 µm versus 20–41 µm in length, respectively), by the arrangement of spermatangia in clusters and smaller carposporangia (11–14 µm x 6–8 µm versus 12–18 µm x 8–10 µm, respectively). Sirodotia assamica differs from S. delicatula in having larger whorls (400–665 µm versus 137–306 µm in diameter, respectively), greater number of cell storeys in primary fascicles (6–12 versus 4–6 cells, respectively), longer carpogonia (37–64 µm x 25–40 µm in length, respectively) and spermatangia in clusters. Moreover, they are genetically quite divergent (2.5–2.7% for rbc L and 4.2%–4.7% for COI-5P). Sirodotia cirrhosa was described by Balakrishnan & Chaugule (1980) from northern and southern India. However, S. cirrhosa differs from S. assamica in having shorter carpogonia (37–64 µm x 29–41 µm long) and smaller carposporangia (11–14 µm x 8–11 µm long) and lacking spermatangia arranged in clusters. There are no molecular data for comparison since S. cirrhosa has not been reported since the record by Balakrishnan & Chaugule (1980). Moreover, the nomenclatural type of S. cirrhosa is not available for a comparative analysis since it is not lodged in the UPS herbarium (Uppsala University, Sweden), where it was supposed to be deposited according to Balakrishnan & Chaugule (1980).

Figures

FIGURE 3. Sirodotia assamica sp. nov. a. Main axis. b. Whorl showing densely arranged gonimoblast filaments along the internode (arrow). c. Primary fascicles and spermatangia (Sp) in clusters on a primary fascicle. d. Carposporangia (Cp), prostrate (Pr) and erect (Er) gonimoblast filaments. e. Detail of spermatangia (Sp) in clusters on primary fascicle. f. Spermatangia (Sp) in clusters on a secondary fascicle. g. A carpogonium with a mature trichogyne (Tr) and a basal hemispherical protuberance (PB). h. Fertilized carpogonium with attached spermatium and gonimoblast initial (GI) on the same side of the basal protuberance. Scale bar: 100 µm for figure a; 50 µm for figures b, c and f; 20 µm for figures d,e,g and h.