''Paedoclione doliiformis'' is a

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 appropriate s ...

sea angel Sea angels (clade Gymnosomata) are a large group of small free-swimming sea slugs, not to be confused with Cnidarians (Jellyfish and other similar creatures), classified into six different families. They are pelagic opisthobranchs in the clade G ...

, a small floating

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary t ...

, a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Clionidae The Clionidae are a family of sea angels, which are a group of pelagic marine gastropods. They resemble angels, complete with flapping "wings", hence their common name. They are gelatinous, mostly transparent pteropods, and they only have sh ...

. ''Paedoclione doliiformis'' is the only species in the genus ''Paedoclione''."Genus ''Paedoclione''"
Marine Species Identification Portal, accessed 4 February 2011. The generic name is a reference to the

paedomorphic Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

habit of this genus, which retains many larval features throughout its life.Lalli C. M. & Conover R. J. (1973). "Reproduction and development of ''Paedoclione doliiformis'', and a comparison with ''Clione limacina'' (Opisthobranchia: Gymnosomata)". ''Marine Biology'' 19(1): 13–22. . ''Paedoclione doliiformis'' was originally described by

Charles Haskell Danforth Charles Haskell Danforth (30 November 1883 – 10 January 1969) was an American anatomist and professor at Stanford University. He took a special interest in problems of heredity and comparative anatomy. Danforth was born in Oxford, Maine to Jame ...

in 1907. It was not collected by zoologists for the next 61 years. It was rediscovered in 1968 by Lalli (1972).Lalli C. M. (1972). "Food and feeding in ''Paedoclione doliiformis'' Danforth, a neotenous gymnosomatous pteropod". ''Biological Bulletin'' 143(2)
392
402, 4 figs
abstract and PDF

Distribution

The type locality of ''Paedoclione doliiformis'' is

Casco Bay Casco Bay is an inlet of the Gulf of Maine on the southern coast of Maine, New England, United States. Its easternmost approach is Cape Small and its westernmost approach is Two Lights in Cape Elizabeth. The city of Portland sits along its south ...

Portland, Maine Portland is the largest city in the U.S. state of Maine and the seat of Cumberland County. Portland's population was 68,408 in April 2020. The Greater Portland metropolitan area is home to over half a million people, the 104th-largest metropol ...

. The distribution includes St. Margarets Bay, Nova Scotia, the

Gulf of Maine The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America. It is bounded by Cape Cod at the eastern tip of Massachusetts in the southwest and by Cape Sable Island at the southern tip of Nova Scotia in the northeast ...

and possibly elsewhere.

Description

''Paedoclione doliiformis'' retains juvenile (larval) physical characteristics for the whole of its life. This is called

neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

(a kind of

pedomorphosis Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

). The body length is up to 1.5 mm. ''Paedoclione doliiformis'' has no shell. It is a gelatinous, mostly transparent pteropod, and it only has a shell in its embryonic stage. The orange visceral sac is confined to the anterior part.

Life cycle

Mating is carried out ventrally for mutual fertilization. The following spring, this results in a free-floating, gelatinous egg mass. Eggs hatch after three days, and the shell is retained until the 11th day.

Feeding habits

''Paedoclione doliiformis'' feeds exclusively on ''

Limacina helicina ''Limacina helicina'' is a species of small swimming planktonic sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies (Thecosomata). ''Limacina helicina'' is a keystone species of mesozooplankton in Ar ...

'' and on ''

Limacina retroversa ''Limacina retroversa'' is a species of swimming predatory sea snail in the family Limacinidae, that belongs to the group commonly known as sea butterflies (Thecosomata). There is one subspecies, ''Limacina retroversa australis'' (Eydoux & Sou ...

'', but solely on juveniles with shells smaller than 1 mm.Lalli C. M. & Gilmer R. W. (1989). ''Pelagic Snails. The biology of holoplanktonic gastropod molluscs.'' Stanford University Press: Stanford, California
page 185188
Its abundance is closely linked to that of its prey.

References

{{Taxonbar, from=Q3142296 Clionidae Gastropods described in 1907