Vaucheria aestuarii Muralidhar, Novis & Broady, 2014

Muralidhar, Abishek, Broady, Paul A., Macintyre, Duncan P., Wilcox, Michael D., Garrill, Ashley & Novis, Phil M., 2014, Morphological and phylogenetic characterization of seven species of Vaucheria (Xanthophyceae), including two new species, from contrasting habitats in New Zealand, Phytotaxa 186 (3), pp. 117-136 : 127-131

Vaucheria aestuarii Muralidhar, Novis & Broady , sp. nov. ( Fig. 6 ).

Siphons 45–65 µm diameter; branches frequent. Alga dioecious (Entwisle 1998a); antheridia and oogonia borne terminally on separate, long siphons; distribution frequent ( Fig. 6 ). Antheridia cylindrical-acuminate; 180–400 µm long; in monopodial clusters of three and subtended by 1–2 wall bound cavities; with short cylindrical papillae (one-three lateral and one terminal), 10–14 µm Oogonia clavate, 110–130 µm diameter, not subtended by wall-bound cavity, irregular mass of protoplasm subtending oogonium. Oospores ellipsoid, thin-walled, covering entire terminal portion of oogonium, never free from the oogonial wall.

Type:— NEW ZEALAND. Canterbury: Avon Heathcote Estuary, Christchurch (43.525723° S, 172.724087° E), D. Macintyre, 8 December 2011, G7 (holotype: CHR! 631518) .

Section:— Piloboloideae ( Walz 1866: 144) Heering (1907: 169).

Etymology:— named after the habitat the type strain was sourced from, an estuary.

Molecular data:— This strain grouped together with other species from sect. Piloboloideae ( V. litorea , V. medusa Christensen (1952: 179) and V. compacta ( Collins 1900: 13) Collins ex Taylor (1937: 226) ; Fig. 2 ). The closest relative to the V. aestuarii strain in terms of p-distance was a Vaucheria medusa strain collected from an estuary at Frogmore, South Devon, England (p-distance = 0.045).

Notes:— The diagnostic characters which set this strain apart from the other species in sect. Piloboloideae ( Blum 1972, Entwisle 1988a) are: the ellipsoidal shape of the oospore which occupies the entire portion of the terminal oogonium, the absence of a wall bound cavity subtending the oospore, the presence of an irregular mass of protoplasm left behind by the mature oospore and long terminal antheridia in monopodial clusters of three with short cylindrical papillae. Vaucheria litorea and V. glomerata Blum & Womersley (1955: 713) are the closest morphologically to V. aestuarii . They both have spherical masses of protoplasm left behind by the mature oogonia, in contrast to an irregular mass of protoplasm seen in V. aestuarii . Both have a wall bound cavity subtending the oogonia, which is lacking in V. aestuarii . The length of the antheridia is slightly greater in V. glomerata than in V. aestuarii whilst both exhibit similar cylindrical protuberances. Other antheridial characters that differ between V. aestuarii and V. glomerata are the presence of up to three lateral protuberances (up to two in V. glomerata ) and sometimes two wall-bound cavities in a single antheridium (mostly one in V. glomerata ). These antheridial characters have not been used previously as characters with which to define species in this section. Striking differences in oogonial morphology and to a lesser extent, antheridial morphology, warranted recognition of this strain as a new species. The antheridia and oogonia are arranged in lateral branches in V. medusa and V. compacta which separates them from V. aestuarii in which they are arranged terminally ( Christensen 1952, 1987b). Additionally, V. medusa is monecious which further distinguishes it from V. aestuarii ( Christensen 1952, 1987b). A comparison of characters of some closely related morphospecies in the sect. Piloboloideae is given in Table 4.

This strain grew as pale green mats on intertidal mud flats of the Avon-Heathcote Estuary. Field material was sterile but developed reproductive structures in culture when stressed (see Methods).

Species Gametangial Oogonia Antheridia arrangement

Wall bound Proximal mass Oospore shape Shape Length (µm) Protuberances cavity of protoplasm

Shape Number Length (µm) V. aestuarii Terminal, No Yes, irregular Ellipsoid Cylindrical- fusiform- 180–400 Cylindrical 1 terminal, 1–3 10–14

dioecious mass acuminate lateral

V. compacta Lateral, No No Spherical-ovoid Acuminate 85–225 Conical 2– 4 lateral 16–50 dioecious

V.glomerata Terminal, Yes Yes, spherical Globose-ellipsoid Cylindrical-fusiform <500 Cylindrical 1 terminal, 1–2 10–25 dioecious mass lateral

V. litorea Terminal, Yes Yes, spherical Globose Cylindrical-fusiform> 500 Conical 1 terminal, 1–6 12–48 dioecious mass lateral

V. longicaulis Terminal, No No Globose-ellipsoid Cylindrical-fusiform 330–730 Conical 1 terminal, 1–4 Up to 190 dioecious lateral

V. medusa Lateral, Yes Yes Spherical Fusiform 114 ± 7 Conical 1 terminal, 1–3 – monoecious lateral

V. piloboloides Terminal, No No Ellipsoid- lenticular Cylindrical-fusiform- 212–300 Cylindrical- 1 terminal, 1–4 16–108 monoecious bifurcate conical lateral

Vaucheria litorea Agardh

Siphons 90–150 µm diameter; branches sparse. Alga dioecious. Antheridia cylindrical-acuminate, terminal on siphons, 400–650 µm long; distribution frequent; borne in sympodial clusters of 3 or more ( Fig. 7 ). Antheridia have 1–2 lateral conical papillae 20–30 µm long × 100–140 µm diameter; terminal pore, 8–10 µm Antheridia subtended by wall bound cavity. Oogonia not observed.

Section:— Piloboloideae.

Representative specimen:— NEW ZEALAND: Canterbury: Lake Ellesmere ( Te Waihora ) (43.763501° S, 172.550004° E), P. A. Broady & D. MacIntyre, 2 December 2012, E5A ( CHR 631519 ) .

References:— Blum and Womersley (1955: 714); Christensen (1987b: 18); Entwisle (1988a: 27).

Molecular data:— This strain grouped together with other species from sect. Piloboloideae ( V. aestuarii , V. medusa and V. compacta , Fig. 2 ). In terms of p-distance, our strain of V. litorea was closest to another strain of the same species collected from a salt pan in North Jutland, Denmark (p-distance = 0.028). But phylogenetic analyses failed to resolve the relationships between the three strains of V. litorea in our study.

Notes:— This strain was identified as Vaucheria litorea Agardh based on the morphology and arrangement of the antheridia which exhibited characteristic conical protuberances (1 terminal and 1–4 lateral protuberances). Vaucheria compacta and V. longicaulis of sect. Piloboloideae also exhibit conical protuberances. The lateral protuberances in V. longicaulis reach 190 µm long ( Entwisle 1988a). In this strain they were up to 20–30 µm long, clearly separating it from V. longicaulis . In V. compacta , antheridia are on lateral branches whereas in V. litorea they are terminal. All strains of V. litorea were separated from V. compacta by a robust branch in our phylogenetic analyses, but the relationships between these strains were not resolved; it is possible that V. litorea represents a grade.

This strain grew sheltered under plants in moist soil on the mudflats of Lake Ellesmere / Te Waihora, a brackish lake. Field material was sterile but developed reproductive structures when stressed (see Methods). This is the first record of V. litorea from New Zealand. It is common in intertidal saltmarshes and estuarine habitats worldwide.

Figures

FIGURE 2. 50% majority rule consensus tree showing Bayesian phylogenies of Vaucheria strains from different habitats in New Zealand (indicated in bold) based on the phylogenetic analysis of the rbcL gene and partial rbcL-rbcS spacer region. Support numbers and branches are Bayesian posterior probabilities/ Maximum Parsimony bootstrap values. The different taxonomic sections of the strains are as in Andersen and Bailey (2002) and the presence and absence of a gametophore bearing antheridia and oogonia are indicated beside the tree. Scale bar = 0.1 substitutions/site. Substitution model and data sets described in text.

FIGURE 6. Light micrographs and illustrations of Vaucheria aestuarii reproductive structures (G7). A, C, D, F, G. Clavate oogonia with mass of protoplasm left behind by mature oospore (arrows), note there is no wall bound cavity subtending the oogonia. E. Long cylindrical antheridia with short cylindrical- conical papillae (arrows) in a monopodial cluster, subtended by a wall bound cavity. H.Antheridium with a wall bound cavity (arrow). I. Antheridia in a monopodial cluster, note 2 wall bound cavities (arrows) in a single antheridium separated by a mass of sperm. Bars = 50 µm.

FIGURE 7. Light micrographs and illustration of Vaucheria litorea antheridia (E5A). A, C, F. Long cylindrical antheridia with short conical papillae and subtended by a wall bound cavity in a sympodial cluster. B. Wall bound cavity subtending an antheridium (arrow). D, E. Large terminal pore of an antheridium (arrow). E. Sperm material being ejected from pore. G, H. Lateral conical papillae in antheridium (arrows). Scale bars = 200 µm (A, C, F), 100 µm (B, D, E, G, H).