''Balanoglossus'' is a genus of ocean-dwelling
acorn worms (Enteropneusta). It has zoological importance because, being
hemichordates, they are an "evolutionary link" between
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...
s and
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
s. ''Balanoglossus'' is a
deuterostome
Deuterostomia (; in Greek) are animals typically characterized by their anus forming before their mouth during embryonic development. The group's sister clade is Protostomia, animals whose digestive tract development is more varied. Some ...
, and resembles the sea squirts (
Ascidiacea
Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tun ...
) in that it possesses branchial openings, or "
gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In co ...
s". It has a
notochord
In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consi ...
in the upper part of the body and has no nerve chord. It does have a
stomochord, however, which is a gut chord within the collar. Their heads may be as small as per 2.5 mm (1/10 in) or as large as 5 mm (1/5 in).
Discovery
The discovery of gill-slits in this animal by
Alexander Kovalevsky (1865) led to the creation of the class
Enteropneusta by
Karl Gegenbaur (1870).
Classification
William Bateson
William Bateson (8 August 1861 – 8 February 1926) was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscove ...
(1885) originally included them in phylum
Chordata
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fi ...
. Hyman (1959), however, placed them near
Echinodermata
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...
and gave
Hemichordata a status of an independent phylum.
Habitat
Balanoglossus is a tuberculos (burrowing) and exclusively marine animal. It is 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
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
:
Balanoglossus - delle Chiaje, 1829
World Register of Marine Species. Retrieved 2022-12-14.
* ''Balanoglossus apertus
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Spengel, 1893
* ''Balanoglossus aurantiaca
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Girard, 1853
* ''Balanoglossus australiensis
''Balanoglossus australiensis'' is a species of long acorn worm in Ptychoderidae family which can be found in Gulf of Carpentaria, New Zealand, Australian cities such as Hawkesbury and Manning as well as Solomon Archipelago and its sea
...
'' Hill, 1894
* ''Balanoglossus biminiensis
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Willey, 1899
* ''Balanoglossus borealis
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Willey, 1899
* ''Balanoglossus capensis
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Gilchrist, 1908
* ''Balanoglossus carnosus
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Willey, 1899
* ''Balanoglossus clavigerus
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' Delle Chiaje, 1829
* ''Balanoglossus gigas
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterostome, ...
'' Müller in Spengel, 1893
* ''Balanoglossus hydrocephalus
''Balanoglossus'' is a genus of ocean-dwelling acorn worms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates. ''Balanoglossus'' is a deuterosto ...
'' 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
{{Taxonbar, from=Q1768028
Enteropneusta
Hemichordate genera