''Waldo'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of small

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 * ...

clams in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Galeommatidae Galeommatidae is a family of small and very small saltwater clams, marine bivalve molluscs in the order Galeommatida. Genera and species Genera and species within the family Galeommatidae include: * '' Achasmea'' Dall, Bartsch & Rehder, 1938 ...

. It includes five

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 ...

which are all obligate commensals of

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

s. They are found in the southern

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and Antarctic Oceans, with the exception of '' Waldo arthuri'' which is found in the northeastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

Taxonomy

Brooding Waldo arthuri on Brisaster latifrons

The

''Waldo'' belongs to the

in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Veneroida Venerida (formerly Veneroida) is an order (biology), order of mostly saltwater but also some freshwater bivalve molluscs. This order includes many familiar groups such as many clams that are valued for food and a number of freshwater bivalves. S ...

. It was named in honor of Waldo L. Schmitt, a prominent

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

carcinologist A carcinologist is a scientist who studies crustaceans or is otherwise involved in carcinology Carcinology is a branch of zoology that consists of the study of crustaceans, a group of arthropods that includes lobsters, crayfish, shrimp, krill, ...

. The genus was first established by the American malacologist David Nicol in 1966 based on the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

'' Lepton parasiticus'' recovered from

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

and first described in 1876 by the American malacologist William Healey Dall. The genus was revived and revised in 2002 by the

Argentinean Argentines (mistakenly translated Argentineans in the past; in Spanish language, Spanish (Grammatical gender, masculine) or (Grammatical gender, feminine)) are people identified with the country of Argentina. This connection may be resident ...

malacologists Diego G. Zelaya and Cristián F. Ituarte.

Description

Members of the genus ''Waldo'' have small shells (less than in length) that are ovate to trapezoidal in shape. The shells are extremely thin and fragile and can be translucent or opaque. The shell sculpture consists of commarginal grooves (striae), though weakly to moderately-defined radial ribs may also be present. The hinges of the shells have narrow plates that lack teeth (edentate) with internal ligaments. The outer organic layer of the shell (the

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

) can be thin to thick, and translucent to white in coloration. The

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

covers most of the outer shell surface and possesses small rounded protuberances (papillae). The mantle also has long, slender tentacles that extend well past the shell margin. The

foot The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...

is elongated and thin, and triangular to cylindrical in shape. The heel of the foot may be strong to absent, with one demibranch (

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

plate) on each side.

Ecology and life cycle

All members of the genus ''Waldo'' are believed to be

obligate {{wiktionary, obligate As an adjective, obligate means "by necessity" (antonym ''facultative'') and is used mainly in biology in phrases such as: * Obligate aerobe, an organism that cannot survive without oxygen * Obligate anaerobe, an organism that ...

commensal epibionts of echinoids (

s). Adults are actively mobile, crawling freely about the external surfaces of their

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...

with their large feet, much like

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

s. They use their tentacles to grasp and navigate between the spines of heir hosts. Like most clams, ''Waldo'' species are hermaphroditic. And like other galeommatoideans, they brood their young, protecting them within their

s. When they are old enough to fend for themselves, the parents will deposit them on the same sea urchin they are currently living in. They lack a free-swimming

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 ...

larval phase.

Species and distribution

With the exception of ''Waldo arthuri'', all members of the genus are found in the southern

and Antarctic Oceans. ''Waldo arthuri'' is found in an entirely separate oceanic basin, the northeastern

, where it lives in a commensal relationship with the

heart urchin The heart urchins or Spatangoida are an order of sea urchins. Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the anus towards the other. As a result, heart urch ...

'' Brisaster latifrons''. This widely disparate distribution range is unusual for the genus because of the aforementioned lack of a pelagic larval phase for members of the genus. The genus includes five

. They are the following: *'' Waldo arthuri'' Valentich-Scott, Ó Foighil, & Li, 2013 *'' Waldo digitatus'' Zelaya & Ituarte, 2013 *'' Waldo parasiticus'' ( Dall, 1876) *''

Waldo paucitentaculatus ''Waldo paucitentaculatus'' is a species of bivalve. The species was described in 2013. It is also widely distributed. References Galeommatidae {{Improve categories, date=February 2022 ...

'' Zelaya & Ituarte, 2013 *'' Waldo trapezialis'' Zelaya & Ituarte, 2002

References

External links

{{Taxonbar, from=Q16993467 Galeommatidae Molluscs described in 2013 Bivalve genera