Vaucheria bursata (Müller) Agardh, 1811

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 : 121-124

Vaucheria bursata (Müller) Agardh

Basionym: Conferva bursata Müller (1788: 96)

Siphons 35–110 µm diameter, light to dark green, texture velvety to coarse; branches occasional to frequent. Alga monoecious; antheridia and oogonia adjacent; occasional to frequent, sometimes with two oogonia per antheridium ( Fig. 3 ). Antheridia circinate-cylindrical, 35–110 µm long × 25–35 µm diameter, turning through less than a full circle. Antheridial pedicel straight or curved distally. Oogonia sessile, ovoid-reniform, 35–155 µm long × 30–120 µm diameter; long axes parallel or oblique to the length of siphons. Oospores and oogonia similar in size and shape.

Section:— Corniculatae ( Walz 1866: 144) Entwisle (1988a: 13).

Heterotypic synonyms:— Ectosperma sessilis Vaucher (1803: 31) ; Vaucheria repens Hassall (1843: 430) ; Vaucheria sessilis (Vaucher) de Candolle in Lamarck and de Candolle 1805: 63); Vaucheria sessilis f. clavata Heering (1907: 147) ; Vaucheria sessilis f. repens (Hassall) Hansgirg (1886: 95) .

Representative specimens:— NEW ZEALAND: Canterbury: Okeover Stream, Christchurch (43.522546° S, 172.584832° E), A . Muralidhar , 10 November 2010, UCVFW1 ( CHR 631511 ) ; NEW ZEALAND: Canterbury: Okeover Stream, Christchurch (43.523075° S, 172.587363° E), A . Muralidhar , 31 January 2011, UCVFW2 ( CHR 631512 ) ; NEW ZEALAND: Canterbury: Heathcote River, Christchurch (43.551215° S, 172.671878° E), A . Muralidhar , 19 January 2011, UCVFW3 ( CHR 631513 ) ; NEW ZEALAND: Canterbury: Kaituna River (43.725468° S, 172.693239° E), A . Muralidhar , 1 February 2011, UCVFW4 ( CHR 631514 ) ; NEW ZEALAND: Canterbury: Knights Stream (43.592133°S, 172.559791°E), P. A . Broady , 26 February 2011, UCVFW5 ( CHR 631515 ) .

References:— Christensen (1969: 26); Christensen (1973: 513); Entwisle (1987: 309); Entwisle (1988a: 17).

Molecular data:— Our five V. bursata strains grouped together in a robust clade making up sect. Corniculatae in both MPB (maximum parsimony bootstrap) and Bayesian analyses ( Fig. 2 ). This clade also included sequences of strains designated as V. bursata , V. repens and V. dilwynii from Genbank in addition to V. cf. borealis from this study. All five V. bursata strains in this study were very closely related with a maximum p-distance of 0.005 between them. It should be noted that V. bursata is not monophyletic.

Notes:— All five strains conformed closely to the published descriptions of Vaucheria bursata (Müller) Agardh ( Entwisle 1987, 1988a). Vaucheria bursata has been recorded previously in New Zealand as the synonym Vaucheria sessilis f. repens ( Sarma 1974) . This is a common species found in freshwater habitats worldwide.

There has been considerable disagreement about the classification and naming of species in the V. bursata complex. The synonymy of V. bursata and V. sessilis is well-accepted ( Rieth 1963, 1980, Christensen 1969, Entwisle 1987, 1988 a, Johnson & Merritt 2002) but there is conflict about which name has priority. Johnson & Merritt (2002) used the name V. sessilis (Vaucher) de Candolle in Lamarck and de Condolle, while Entwisle (1988a) used the name V. bursata (Müller) Agardh. Because Conferva bursata Müller , the basionym from which V. bursata originates, clearly predates Ectosperma sessilis Vaucher , the basionym of Vaucheria sessilis , we follow Entwisle (1988a) in naming our strains V. bursata . Entwisle placed two other species with slightly different morphologies, V. repens and V. clavata , in synonymy with V. bursata but Blum (1972) considered V. repens as a unique species while Johnson & Merritt (2002) listed it as a doubtful species.

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 3. Light micrographs and illustration of Vaucheria bursata reproductive structures. A, E. UCVFW1. G. UCVFW2. C, D. UCVFW3. B. UCVFW4. H, I. UCVFW5. G. Two oogonia either side of a developing antheridium. I. Two sets of antheridia and oogonia side by side. Scale bars = 50 µm.