Balanoglossus

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

Last updated September 25, 2025

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 chordates in that they possess branchial openings.^[1]

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

Acorn worms. Specimens 10 and 11 are Balanoglossus. Enteropneusta.png — 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 apertusSpengel, 1893
Balanoglossus aurantiacaGirard, 1853
Balanoglossus australiensis Hill, 1894
Balanoglossus biminiensisWilley, 1899
Balanoglossus borealisWilley, 1899
Balanoglossus capensisGilchrist, 1908
Balanoglossus carnosusWilley, 1899
Balanoglossus clavigerusDelle Chiaje, 1829
Balanoglossus gigas Müller in Spengel, 1893
Balanoglossus hydrocephalusvan der Horst, 1940
Balanoglossus jamaicensisWilley, 1899
Balanoglossus misakiensisKuwano, 1902
Balanoglossus natalensisGilchrist, 1908
Balanoglossus numeensisMaser, 1913
Balanoglossus occidentalisRitter, 1902
Balanoglossus parvulusPunnett, 1903
Balanoglossus proterogoniusBelichov, 1928
Balanoglossus robiniiGiard, 1882
Balanoglossus salmoneusBelichov, 1928
Balanoglossus simodensisMiyamoto & Saito, 2007
Balanoglossus stephensonivan der Horst, 1937
Balanoglossus studiosorumvan 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.

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[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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