Antithamnion nipponicum (Ceramiaceae, Rhodophyta), incorrectly known as A. pectinatum in western Europe, is a recent introduction along the North Carolina and Pacific coasts of North America

Figures & data

Fig. 1. Maximum likelihood tree inferred from 11 rbcL sequences of Antithamnion and Antithamnionella species, and from one specimen of Ceramium californicum used as the outgroup. The Ln likelihood of the tree was −3992.6321. Bootstrap values (>50%) are shown for all ML (top) and MP (bottom) analyses.

Table 1.  Taxon and collection information for specimens used in the morphological study and rbcL analyses

Species	Location	Collection date	Collector	Habit/attachment	GenBank number
Antithamnion aglandum Kim et Lee	Jeoongdori, Wando, Korea	29.Jan.1999	S.M. Boo, T.O. Cho & H.G. Choi	Creeping on rope	AY594700
Antithamnion hanovioides (Sonder) De Toni	Pennington Bay, Kangaroo Island, S. Australia	7.Sept.1995	M. Hommersand		AY591927
Antithamnion ‘hubbsii’ Dawson	Halfmoon Bay, San Mateo Co., California, USA	3.Jun.2003	T.O. Cho & B.Y. Won	Creeping on decaying wood of floating docks	AY591930
Antithamnion nipponicum Yamada et Inagaki	Hachinohe, Aomori, Japan	21.May.1995	M. Kamiya	Culture strain #1078, Kobe University Research Center for inland seas	AY594699
Antithamnion nipponicum	In front of Duke University Marine Laboratory, Pivers I., Beaufort, Carteret Co, North Carolina, USA	29.Oct.2003	T.O. Cho & B.Y. Won	Creeping on Hypnea sp.	AY591928
Antithamnion nipponicum	Jetty, Beaufort, Carteret Co., North Carolina, USA	29.Oct.2003	T.O. Cho	Creeping on Hypnea sp.	AY591929
Antithamnion nipponicum	Torumni, Kobe, Japan	15.Jul.2004	S. Kawaguchi
Antithamnion pectinatum (Montagne) Brauner	Lee Bay, Stewart Island, New Zealand	3.Oct.2004	W.A. Nelson	Creeping on Laurencia thyrsifera	DQ023481
Antithamnion pectinatum	Island Bay, Wellington, North Island, New Zealand	22.Aug.1990	W.A. Nelson	Creeping on Gelidium sp.	-
Antithamnionella spirographidis (Schiffner) Wollaston	Burghsluis, Netherlands	8.Aug.1997	M. Hommersand		AY591925
Antithamnionella spirographidis	Monterey Bay, California	11.Dec.1999	T.O. Cho		AY591923
Antithamnionella ternifolia (Hooker et Harvey) Lyle	Williamston, Australia	28.Mar.2002	J. West		AY591926
Ceramium californicum J. Agardh	Yaquina Bay, Oregon, USA	13.Jul.1998	T.O. Cho & G.-I. Hansen		AY591931

Fig. 2–13. Antithamnion nipponicum from Halfmoon Bay, California, USA. Figs 2–9. Vegetative structure. Fig. 2. Upright thallus. Scale bar 0.5 mm. Fig. 3. Apical region showing successive development of opposite pinnae. Scale bar 100 µm. Fig. 4. Pinnae near apex with mostly abaxial pinnules. Scale bar 50 µm. Fig. 5. Pinnae with basal branched pinnules (arrows) in the middle thallus. Scale bar 100 µm. Fig. 6. Indeterminate lateral axis arising from basal cell of pinna. Scale bar 100 µm. Fig. 7. Gland cell (arrow) developing adaxially from lowermost cells of pinnules. Scale bar 50 µm. Fig. 8. Gland cell developing adaxially from upper side of basal cell of pinnule. Scale bar 5 µm. Fig. 9. Rhizoids developing from basal cell of pinna and terminating in multilobed disc. Scale bar 100 µm. Figs 10–13. Tetrasporic structure. Fig. 10. Erect tetrasporangial thallus with tetrasporangia on the main and lateral axes. Scale bar 0.5 mm. Fig. 11. Pinna bearing tetrasporangial initials (arrows). Scale bar 100 µm. Fig. 12. Pinna bearing mature tetrasporangia. Scale bar 100 µm. Fig. 13. Basal-most cells of pinnules bearing tetrasporangia. Scale bar 40 µm. Abbreviations: AC: apical cell; Ax: axial cell; BC: basal cell; GC: gland cell; IB: indeterminate lateral axis; R: rhizoid; T: tetrasporangium; Pl: pinnule; Pn: pinna.

Fig. 14–21. Male structures of Antithamnion nipponicum from Halfmoon Bay, California, USA. Fig. 14. Male thallus. Scale bar 0.5 mm. Fig. 15. Apical region of male thallus. Scale bar 200 µm. Fig. 16. Spermatangial heads replacing pinnules. Scale bar 200 µm. Fig. 17. Spermatangial parent cells (arrow) borne on pinnule-like spermatangial head. Scale bar 10 µm. Fig. 18. Mature spermatangia borne on pinnule-like spermatangial head. Scale bar 10 µm. Fig. 19. Spermatangial heads (arrow) produced on special branches on adaxial side of pinnule. Scale bar 50 µm. Fig. 20. Spermatangial parent cells (arrow) produced on special branches on adaxial side of pinnule. Scale bar 10 µm. Fig. 21. Spermatangia (arrowhead) borne on spermatangial parent cells (arrow) on special branches on adaxial side of pinnule. Scale bar 10 µm. Abbreviations as in Figs 2–13.

Fig. 22–30. Female structures of Antithamnion nipponicum from Halfmoon Bay, California, USA. Fig. 22. Female thallus. Scale bar 250 µm. Fig. 23. Apical region with procarp (arrow). Scale bar 4.5 µm. Fig. 24. Upper part with procarps (arrows) borne on basal cells of pinna. Scale bar 50 µm. Fig. 25. Procarp composed of carpogonial branch and supporting cell. Fig. 26. Post-fertilization stage showing auxiliary cell borne on supporting cell, and connecting process (arrow) emanating from carpogonium and linking to auxiliary cell. Fig. 27. Formation of gonimoblast initial and foot cell from auxiliary cell. Fig. 28. Formation of first gonimolobes from gonimoblast initial. Scale bars 5 µm. Fig. 29. Formation of fusion cell from foot cell and supporting cell. Scale bar 40 µm. Fig. 30. Mature, naked cystocarp with two gonimobles. Scale bar 100 µm. Abbreviations: Au: auxiliary cell; CB1–3: sequence formation of carpogonial branch cells; Cp: carpogonium; Cy: cystocarp; Ft: foot cell; Fu: fusion cell; G: gonimoblast; Gi: gonimoblast initial; Gl: first gonimolobes; Su: supporting cell.

Fig. 31–35. Antithamnion nipponicum from Beaufort, North Carolina, USA. Fig. 31. Thallus growing on Hypnea sp. Scale bar 500 µm. Fig. 32. Apical region. Scale bar 50 µm. Fig. 33. Pinnae in middle part of thallus. Scale bar 50 µm. Fig. 34. Gland cells. Scale bar 40 µm. Fig. 35. Basal part showing indeterminate lateral axis and rhizoids produced from basal cells of pinnae. Scale bar 50 µm. Abbreviations as in Figs 2–13.

Fig. 36–41. Antithamnion nipponicum. Figs 36–38. Field material collected from Kobe, Japan. Fig. 36. Apical region showing successive development of opposite pinnae. Fig. 37. Indeterminate lateral axis arising from basal cell of pinna. Fig. 38. Male thallus. Scale bars 100 µm. Figs 39–41. Female culture strain (strain #1078 in Kobe University Research Center, Japan). Fig. 39. Pinnae. Scale bar 50 µm. Fig. 40. Indeterminate lateral axis produced from basal cell of pinna. Scale bar 40 µm. Fig. 41. Upper part of thallus with procarp born on basal cell (bc). Scale bar 50 µm. Abbreviations as in Figs 2–13.

Fig. 42–47. Antithamnion pectinatum and A. aglandum. Figs 42–44. Fragment of holotype of A. pectinatum from New Zealand. Fig. 42. Vegetative thallus. Scale bar 100 µm. Fig. 43. Middle part of thallus showing indeterminate lateral axis replacing a paired pinna. Scale bar 100 µm. Fig 44. Pinnae showing gland cell (arrow) touching three cells. Scale bar 50 µm. Figs 45–47. A. aglandum from Korea. Fig. 45. Vegetative thallus. Scale bar 300 µm. Fig. 46. Middle part of thallus showing indeterminate lateral axis (arrow) and rhizoid (arrowhead) produced from basal cell of pinnae. Scale bar 50 µm. Fig. 47. Pinnae. Scale bar 100 µm. Abbreviations as in Figs 2–13.