Balanoglossus

Balanoglossus
	Unidentified specimen from Réunion
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Hemichordata
Class:	Enteropneusta
Order:	Enteropneusta
Family:	Ptychoderidae
Genus:	Balanoglossus; Delle Chiaje, 1829
Species
	See text.

Balanoglossus is a genus of ocean-dwelling acorn worms. It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. Balanoglossus specimens are deuterostomes, and resemble the sea squirts in that they possess branchial openings, or "gill slits".^[1] They have notochords and stomochords but no dorsal nerve cord.

Their heads are between 2.5 mm (1/10 in) and 5 mm (1/5 in) wide.

Discovery

Johann Friedrich von Eschscholtz discovered Balanoglossus in 1825 on Mashail Island, and described it as a worm-like holothurian. The discovery of gill slits in these animals by Alexander Kovalevsky (1865) led to the creation of the class Enteropneusta by Carl Gegenbaur (1870).

Classification

William Bateson (1885) originally included them in phylum Chordata.^[2] Hyman (1959), however, placed them near Echinodermata and gave Hemichordata a status of an independent phylum.

Habitat

1. Ptychodera clavigera, von der dorsalen Seite. 1 / l . Nach dem Leben. 2. Ptychodera minuta q 1 , von der ventralen Seite. 2 /i- Nach dem Leben. 3. desgl. Q, von der dorsalen Seite. 2 /j. Nach dem Leben. 4. Ptyclwdera erythraea, von der dorsalen Seite. Vi- Nach den vorhandnen Bruchstücken des einzigen, in Spiritus conservirten Exemplars. 5. ScMzocardium brasiliense, von der Seite. Nach dem Leben. 6. Glandiceps talaboti. Vorderkörper, von der dorsalen Seite, '/i* Nach dem Leben. 7. Glandiceps haeksi, erwachsen, Vorderkörper von der ventralen Seite. Vi- Nach dem mir vor- liegenden Spiritus -Exemplar. 8. Dasselbe Exemplar von der dorsalen Seite. 9. Junges Individuum derselben Art. 2 /i- Nach einem Spiritus -Exemplar. 10. Balanoglossus Jcoicalevskii. 4 /i- Nach dem Leben. 11. Balanioglossus hupfferi. i / i . Nach dem Leben. Die Originale zu Fig. 2, 3, 4, 7, 8 sind von Herrn O. Peters in Göttingen, zu Fig. 5 von Herrn Prof. E. Selenka in Erlangen, zu Fig. 6 von Herrn Merculiako in Neapel, zu Fig. 10 von Herrn Prof. Charles S. Minot in Boston, zu Fig. 1, 9 und 11 von mir angefertigt. — Acorn worms. Specimens 10 and 11 are *Balanoglossus.*

Balanoglossus are burrowing, exclusively marine animals. They are found in shallow waters between tide marks along the coast of warm and temperate oceans.

Species

The World Register of Marine Species lists the following species:^[3]

Balanoglossus apertus Spengel, 1893
Balanoglossus aurantiaca Girard, 1853
Balanoglossus australiensis Hill, 1894
Balanoglossus biminiensis Willey, 1899
Balanoglossus borealis Willey, 1899
Balanoglossus capensis Gilchrist, 1908
Balanoglossus carnosus Willey, 1899
Balanoglossus clavigerus Delle Chiaje, 1829
Balanoglossus gigas Müller in Spengel, 1893
Balanoglossus hydrocephalus van der Horst, 1940
Balanoglossus jamaicensis Willey, 1899
Balanoglossus misakiensis Kuwano, 1902
Balanoglossus natalensis Gilchrist, 1908
Balanoglossus numeensis Maser, 1913
Balanoglossus occidentalis Ritter, 1902
Balanoglossus parvulus Punnett, 1903
Balanoglossus proterogonius Belichov, 1928
Balanoglossus robinii Giard, 1882
Balanoglossus salmoneus Belichov, 1928
Balanoglossus simodensis Miyamoto & Saito, 2007
Balanoglossus stephensoni van der Horst, 1937
Balanoglossus studiosorum van der Horst, 1940

References

^ Morgan, Thomas (January 1894). The development of balanoglossus. T. H. Morgan.
^ Bateson, William (January 1, 1885). "II. Note on the later stages in the development of Balanoglossus Kowalevskii (Agassiz), and on the affinities of the enteropneusta". Proceedings of the Royal Society of London. 38 (235–238): 23–30. doi:10.1098/rspl.1884.0058.
^ Balanoglossus - delle Chiaje, 1829 World Register of Marine Species. Retrieved 2022-12-14.

[T.H-1] Morgan, Thomas (January 1894). The development of balanoglossus. T. H. Morgan.

[2] Bateson, William (January 1, 1885). "II. Note on the later stages in the development of Balanoglossus Kowalevskii (Agassiz), and on the affinities of the enteropneusta". Proceedings of the Royal Society of London. 38 (235–238): 23–30. doi:10.1098/rspl.1884.0058.

[3] Balanoglossus - delle Chiaje, 1829 World Register of Marine Species. Retrieved 2022-12-14.

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