Maldanidae is a family of more than 200 species of marine

polychaetes Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are m ...

commonly known as bamboo worms or maldanid worms. They belong to the order

Capitellida Capitellida is an order of marine sedentarian annelids The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, a ...

, in the phylum

Annelida The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to variou ...

. They are most closely related to family

Arenicolidae Arenicolidae is a family of marine polychaete worms. They are commonly known as lugworms and the little coils of sand they produce are commonly seen on the beach. Arenicolids are found worldwide, mostly living in burrows in sandy substrates. Most ...

, and together form the clade

Maldanomorpha Maldanomorpha is a monophyletic group, or clade, of polychaete worms in the phylum Annelida The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant specie ...

Morphology

Maldanid worms have a long and cylindrical body that usually bends at one or both ends. It can be divided into four parts: 1) a

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

, formed by a

dorsally Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

positioned

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; : prostomia; sometimes also called the "acron") is the Cephalization, cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not in ...

that is fused to the

peristomium The peristomium is the first true body segment in an annelid worm's body in the anterior end. It is directly behind the prostomium and contains the mouth, tentacular cirri, and sometimes feeding palps, which may instead occur on the prostomium. If ...

, sometimes with a flattened

cephalic A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

plate; 2) a

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

, formed by the first four chaetigers (i.e.

chaeta A chaeta or cheta (; ) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as arthropods. Polychaete annelids (''polychaeta'' literally me ...

e-bearing segments), usually with strong spines; 3) an

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

, with several longer chaetigers that are often followed by a number of achaetous (i.e. without

e) segments; 4) a posterior end, with a

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

that contains the

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

. The maldanid

takes a wide variety of forms such as conical, plate-shaped and funnel-shape. Sometimes a few prepygidial (i.e. anterior to the

) segments can be observed. The

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed late ...

are generally biramous, with elongated median chaetigers. The notochaetae appear as various forms of capillaries, while the neurochaetae appear as various forms of uncini (i.e. hook-like structures), sometimes replaced by acicular (i.e. needle-like) spines in some

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

segments.

Ecology

Habitat

Species of maldanid worms are distributed in all marine regions of

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, from the intertidal regions to deep waters. Some species inhabit estuarine areas, and some species have been seen living on

hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...

s. They are

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

creatures that build tubes made of mineral particles of diverse sizes and textures; these tubes are fixed to stones, shells, algal holdfasts, mud or sandbanks through a thin and transparent matrix of

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

that is produced after the end of the larval period. Several species build tubes under rocks forming horizontal galleries, or vertical galleris in sand or mud at the bottom of

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

Nutrition

They consume organic material, mostly composed of

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

, although

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s and

protozoa Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...

ns have been seen in the gut of some species. Most of them are head-down feeders that transport sediments upward from below the ocean floor surface. However some species have been observed dragging surface material down their tube into a feeding cavity. During feeding, the worms extend a papillae-covered globular

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

through an increase of the

coelom The coelom (or celom) is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, i ...

ic pressure in the first four chaetigers. An enhanced

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

l growth observed within the tube wall of one species, '' Maldane sarsi'', might also be a source of nutrition. Another species, '' Praxillura maculata'', bears stiff particle-collecting spikes attached to the tube's end to collect

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and organic particles and transport them to the gut.

Reproduction

Maldanid worms are gonochoristic and present a variety of reproductive modes. Some species spawn their gametes into

seawater Seawater, or sea water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximat ...

, where fertilization occurs; others may incubate eggs in the tube or directly until the development of larvae. They are capable of both anterior and posterior regeneration after suffering damage due to their fragile and easily fragmented bodies, and at least one species that reproduces asexually has been described.

Embryonic development

Like other invertebrates in the clade

Spiralia The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other Taxon, taxa. The term ''Spiralia'' is applied to those phyla that exhibit canonical spiral clea ...

, bamboo worms undergo

spiral cleavage In embryology, cleavage is the division of cells in the early development of the embryo, following fertilization. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same siz ...

during their early development. The larvae have a prototroch, neurotroch and telotroch, as is common in many

. The larval period is short, and the larval development is either lecithotrophic (i.e. with a yolk sac attached for nutrition) or direct (i.e. having to feed independently).

Phylogeny

Maldanidae and

are united by the clade

inside of

, an order of

in the phylum

. According to a

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

based on morphological data from 2011, several of the subfamilies inside Maldanidae are united under a clade called 'Maldanoplaca'. Members of this clade would be united by the evolution of the

into an anal plate. However, a

molecular phylogeny Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

in 2018 reveals that both Maldanoplaca and the subfamily Euclymeninae are

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

Classification

The complete classification of bamboo worms accounts for 6 subfamilies, 38 genera and around 261 species. *Subfamily Rhodininae **'' Rhodine'' – 7 species **'' Boguea'' – 2 species **'' Boguella'' – 1 species *Subfamily Lumbriclymeninae **'' Lumbriclymene'' – 10 species **'' Lumbriclymenella'' – 2 species **'' Clymenopsis'' – 4 species **'' Praxillura'' – 6 species *Subfamily Notoproctinae **'' Notoproctus'' – 9 species *Subfamily Maldaninae **'' Asychis'' (=''Maldanopsis'' ; ''Branchioasychis'' ) – 5 species **'' Bathyasychis'' – 1 species **''

Chirimia Chirimía (sometimes chirisuya in Peru) is a Spanish term for a type of woodwind instrument similar to an oboe. The chirimía is a member of the shawm family of double-reed instruments, introduced to North, Central and South America in the sixtee ...

'' (=''Chrysothemis'' ) – c. 5 species **'' Maldane'' (=''Heteromaldane'' ; ''Sonatsa'' ) – 18 species **'' Metasychis'' – 4 species **'' Sabaco'' (=''Maldanopsis'' ; =''Branchioasychis'' ) – 9 species *Subfamily Euclymeninae * **'' Aclymene'' – 1 species **'' Axiothella'' (=''Axiotheia'' ) – 19 species **'' Clymenella'' (=''Paraxiothea'' ) – 19 species **'' Clymenura'' – 9 species **'' Euclymene'' (=''Arwidssonia'' ; ''Caecisirrus'' ; ''Leiocephalus'' ) – c. 30 species **'' Eupraxillella'' – 1 species **'' Gravierella'' – 1 species **'' Heteroclymene'' – 2 species **'' Isocirrus'' – 7 species **'' Johnstonia'' – c. 5 species **'' Leiochone'' – 6 species **'' Macroclymene'' – c. 5 species **'' Macroclymenella'' – 1 species **'' Maldanella'' (=''Abyssoclymene'' ) – 12 species **'' Microclymene'' – 5 species **'' Minusculisquama'' – 1 species **'' Mylitta (annelid)'' – 1 species **'' Petaloclymene'' – 2 species **'' Praxilletta'' (=''Iphianissa'' ; ''Praxilla'' ) – c. 15 species **'' Pseudoclymene'' – 1 species **'' Proclymene'' – 1 species *Subfamily Nicomachinae **'' Micromaldane'' – 7 species **'' Nicomache'' (=''Sabella'' ; ''Clymene'' ) – 17 species **'' Petalopoctus'' – c. 10 species

References

{{Authority control Polychaetes Annelid families