''Macrobiotus'' is a genus of
tardigrade
Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them . In 1776, th ...
s consisting of about 100 species within the family
Macrobiotidae.
Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant.
''
Macrobiotus hufelandi'', identified by German researcher Carl August Sigismund Schultze in 1834, is recognized as the first taxonomically named tardigrade species.
By extension, ''Macrobiotus'' was the first ever described tardigrade genus. ''Macrobiotus'' shares similarities to other tardigrade genera, particularly in moulting a non-living
cuticle
A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
over multiple life stages and robust stress tolerance mechanisms.
However, ''Macrobiotus'' tends to be differentiated from other tardigrades by being one of few genera that freely lay ornamented eggs in reproduction. This genera has a relatively diverse distribution in both terrestrial and aquatic environments.
Anatomy and Morphology
Claws
''Macrobiotus'' species commonly exhibit uniform diploclaws on their legs.
Cuticle
''Macrobiotus'' belong to the clade
Ecdysozoa
Ecdysozoa () is a group of protostome animals, including Arthropoda (insects, chelicerates (including arachnids), crustaceans, and myriapods), Nematoda, and several smaller phylum (biology), phyla. The grouping of these animal phyla into a single ...
, characterized for non-living cuticle layers that can be moulted over various life stages.
This cuticular exoskeleton layer facilitates gas and water exchange. Protective benefits of the cuticle typically outweigh the energy costs required to moult.
Nervous System
''Macrobiotus'' neurons innervate a brain with inner and outer connectives, the latter connecting the brain to the trunk. Anterior leg nerves, posterior leg nerves, and peripheral nerves branch off of trunk ganglia. Connectives bridge adjacent trunk ganglia, and interpedal commissures bridge adjacent connectives.
Other Physiological Features
Many ''Macrobiotus'' species also share a firm buccal tube containing a ventral lamina without a ventral hook, a pharynx with one microplacoid and two macroplacoids, and tend to exhibit 10 peribuccal
lamellae
Lamella (: lamellae) means a small plate or flake in Latin, and in English may refer to:
Biology
* Lamella (mycology), a papery rib beneath a mushroom cap
* Lamella (botany)
* Lamella (surface anatomy), a plate-like structure in an animal
* Lame ...
.
Habitat and Distribution
Habitat
''Macrobiotus'' tend to inhabit limnoterrestrial habitats primarily consisting of mosses, though some ''Macrobiotus'' have also been discovered near lichens or aquatic plants.
Some species of ''Macrobiotus'' are obligatory freshwater
invertebrate
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s.
Diet
''
Macrobiotus sapiens'' is an example of a herbivorous diet consisting of algae.
Behaviour
Reproduction
''Macrobiotus'' species exhibit a unique style of ornamented egg morphology and deposition process of freely laying ornamented eggs, contrasting to the ancestral state of freely laying smooth eggs.
This is a
synapomorphy
In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
of two families, Eohypsibioidea and
Macrobiotidae, with Macrobiotoidea including the genus ''Macrobiotus''. Ornamented eggs can limit water evaporation due to surface tension between water molecules and the egg’s ornamentation.
Free-laying of eggs also differs from other common reproductive tendencies for tardigrades, whereby the old cuticle (or the
exuvia
In biology, exuviae are the remains of an exoskeleton and related structures that are left after ecdysozoans (including insects, crustaceans and arachnids) have molted. The exuviae of an animal can be important to biologists as they can often b ...
) is used as an ‘egg keeper’ to allow egg development after laying.
It is hypothesized that releasing eggs into the environment reduces predation of embryonic ''Macrobiotus'' species, providing an evolutionary advantage compared to laying eggs in only one place within the exuvia.
Partner finding behaviour occurs for freely-ovipositing ''
Macrobiotus shonaicus
''Macrobiotus shonaicus'' () is a species of tardigrade in the family Macrobiotidae. it is only known from its type locality (biology), type locality: Tsuruoka, Japan. The species description was published in 2018. The insides of their first thr ...
'' species, where the male touches a female tardigrade’s cloaca with their mouth several times, finishing their courtship ritual once the female tardigrade stops moving.
Freely-ovipositing species are thought to identify partners using pheromones to accommodate only having simple light detection abilities.
Some free-laying egg species like ''
M. shonaicus'' utilize
chemotaxis
Chemotaxis (from ''chemical substance, chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell organism, single-cell or multicellular organisms direct thei ...
for spermatozoa released during ejaculation to identify and swim towards the female’s cloaca.
Eggs are typically laid shortly after reproduction by the female, ranging from 16 minutes to 2 days after mating.
''Macrobiotus'' exhibits bisexual
achiasmy, whereby the process of crossing-over of genetic information between homologous chromosomes in meiosis is absent in both the male and female sex.
Stress Response
Anhydrobiosis
''Macrobiotus'' can withstand desiccation conditions by entering a state of
anhydrobiosis.
Compared to other tardigrades, ''Macrobiotus'' displays a moderate degree of desiccation tolerance. Some species have been observed to accumulate
trehalose
Trehalose (from Turkish '' tıgala'' – a sugar derived from insect cocoons + -ose) is a sugar consisting of two molecules of glucose. It is also known as mycose or tremalose. Some bacteria, fungi, plants and invertebrate animals synthesize it ...
during anhydrobiotic states. Trehalose can induce the anhydrobiotic state, serving as a potential energy source while also protecting cellular membranes and proteins in freezing and desiccation conditions. Survival during anhydrobiosis depends on body size, particularly the size of energy-storing storage cells, though the reproductive state of oocyte maturation has no effect.
It is predicted that the exoskeletal cuticle likely facilitates anhydrobiosis.
Some ''Macrobiotus'' may also demonstrate an
encysted state primarily during periods of rest, but also metabolic depression.
Starvation
One example species, ''
M. sapiens'', forms storage cells within their internal cavity in response to reduced food availability.
This strategy helps ''Macrobiotus'' species survive for several weeks without food, during which storage cell sizes significantly decrease.
Moulting
''Macrobiotus'', like other tardigrades, requires periodic moutling of their cuticle exoskeleton to grow in size.
Cuticle lining the foregut independently moults first and is expelled through the mouth, followed by moutling the cuticles lining the exterior body and hindgut. Moulting may occur in response to poor environmental conditions or starvation as overall body size decreases.
Both male and female partners of ''
M. shonaicus'', a freely-ovipositing species, moult immediately before reproduction, moulting during the process of developing mature
oocyte
An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...
s.
Species
The genus includes the following species:
* ''
Macrobiotus acadianus''
(Meyer & Domingue, 2011)
* ''
Macrobiotus almadai''
Fontoura, Pilato & Lisi, 2008
* ''
Macrobiotus alvaroi''
Pilato & Kaczmarek, 2007
* ''
Macrobiotus anderssoni''
Richters, 1907
* ''
Macrobiotus andinus''
Maucci, 1988
* ''
Macrobiotus anemone''
Meyer, Domingue & Hinton, 2014
* ''
Macrobiotus annewintersae''
Vecchi & Stec, 2021
* ''
Macrobiotus ariekammensis
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. ''Macrobiotus hufelandi'', identified by German ...
''
Węglarska, 1965
* ''
Macrobiotus azzunae
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. '' Macrobiotus hufelandi'', identified by Germ ...
''
Ben Marnissi, Cesari, Rebecchi & Bertolani, 2021
* ''
Macrobiotus basiatus
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. '' Macrobiotus hufelandi'', identified by Germ ...
''
Nelson, Adkins Fletcher, Guidetti, Roszkowska, Grobys & Kaczmarek, 2020
* ''
Macrobiotus birendrai
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. '' Macrobiotus hufelandi'', identified by Germ ...
''
Kayastha et al., 2021
* ''
Macrobiotus biserovi
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. '' Macrobiotus hufelandi'', identified by Germ ...
''
Bertolani, Guidi & Rebecchi, 1996
* ''
Macrobiotus caelestis''
Coughlan, Michalczyk & Stec, 2019
* ''
Macrobiotus caelicola''
Kathman, 1990
* ''
Macrobiotus canaricus''
Stec, Krzywański & Michalczyk, 2018
* ''
Macrobiotus caymanensis''
Meyer, 2011
* ''
Macrobiotus crenulatus''
Richters, 1904
* ''
Macrobiotus crustulus''
Stec, Dudziak & Michalczyk, 2020
* ''
Macrobiotus dariae''
Pilato & Bertolani, 2004
* ''
Macrobiotus deceptor''
Meyer, Hinton, Gladney & Klumpp, 2017
* ''
Macrobiotus denticulus''
Dastych, 2002
* ''
Macrobiotus diversus''
Biserov, 1990
* ''
Macrobiotus dolosus''
Bertolani et al., 2023
* ''
Macrobiotus drakensbergi''
Dastych, 1993
* ''
Macrobiotus dulciporus''
Roszkowska, Gawlak, Draga & Kaczmarek, 2019
* ''
Macrobiotus echinogenitus''
Richters, 1903
* ''
Macrobiotus engbergi''
Stec, Tumanov & Kristensen, 2020
* ''
Macrobiotus fontourai''
Bertolani et al., 2023
* ''
Macrobiotus furcatus''
Ehrenberg, 1859
* ''
Macrobiotus glebkai''
Biserov, 1990
* ''
Macrobiotus grandis''
Richters, 1911
* ''
Macrobiotus gretae''
Massa et al., 2021
* ''
Macrobiotus halophilus''
Fontoura, Rubal & Veiga, 2017
* ''
Macrobiotus hannae''
Nowak & Stec, 2018
* ''
Macrobiotus horningi''
Kaczmarek & Michalczyk, 2017
* ''
Macrobiotus hufelandi''
C.A.S. Schultze, 1834
* ''
Macrobiotus humilis''
Binda & Pilato, 2001
* ''
Macrobiotus hupingensis''
Yuan et al., 2022
* ''
Macrobiotus hyperboreus''
Biserov, 1990
* ''
Macrobiotus iharosi''
Pilato, Binda & Catanzaro, 1991
* ''
Macrobiotus insularis''
Pilato, 2006
* ''
Macrobiotus joannae''
Pilato & Binda, 1983
* ''
Macrobiotus julianae
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. '' Macrobiotus hufelandi'', identified by Germ ...
''
(Meyer, 2012)
* ''
Macrobiotus kamilae''
Coughlan & Stec, 2019
* ''
Macrobiotus kazmierskii''
Kaczmarek & Michalczyk, 2009
* ''
Macrobiotus kirghizicus''
Tumanov, 2005
* ''
Macrobiotus kosmali''
Kayastha et al., 2023
* ''
Macrobiotus kristenseni''
Guidetti, Peluffo, Rocha, Cesari & Moly de Peluffo, 2013
* ''
Macrobiotus kurasi''
Dastych, 1981
* ''
Macrobiotus lazzaroi''
Maucci, 1986
* ''
Macrobiotus lissostomus''
Durante Pasa & Maucci, 1979
* ''
Macrobiotus longipes''
Mihelčič, 1971
* ''
Macrobiotus macrocalix''
Bertolani & Rebecchi, 1993
* ''
Macrobiotus maculatus''
Iharos, 1973
* ''
Macrobiotus madegassus''
Maucci, 1993
* ''
Macrobiotus mandalaae''
Pilato, 1974
* ''
Macrobiotus margoae''
Stec, Vecchi & Bartels, 2021 in Stec et al. 2021
* ''
Macrobiotus marlenae''
Kaczmarek & Michalczyk, 2004
* ''
Macrobiotus martini''
Bartels, Pilato, Lisi & Nelson, 2009
* ''
Macrobiotus mileri''
Stec, 2024
* ''
Macrobiotus modestus''
Pilato & Lisi, 2009
* ''
Macrobiotus muralis''
Bertolani et al., 2023
* ''
Macrobiotus naginae''
Vecchi et. al, 2022
* ''
Macrobiotus naskreckii''
Bąkowski, Roszkowska, Gawlak & Kaczmarek, 2016
* ''
Macrobiotus nebrodensis''
Pilato, Sabella, D'Urso & Lisi, 2017
* ''
Macrobiotus nelsonae''
Guidetti, 1998
* ''
Macrobiotus noemiae''
Roszkowska & Kaczmarek, 2019
* ''
Macrobiotus noongaris''
Coughlan & Stec, 2019
* ''
Macrobiotus norvegicus''
Mihelčič, 1971
* ''
Macrobiotus occidentalis''
occidentalis Murray, 1910
* ''
Macrobiotus occidentalis''
striatus Dastych, 1974
* ''
Macrobiotus ocotensis''
Pilato, 2006
* ''
Macrobiotus ovovittatus''
Stec, 2024
* ''
Macrobiotus pallarii''
Maucci, 1954
* ''
Macrobiotus papei''
Stec, Kristensen & Michalczyk, 2018
* ''
Macrobiotus patagonicus''
Maucci, 1988
* ''
Macrobiotus paulinae''
Stec, Smolak, Kaczmarek & Michalczyk, 2015
* ''
Macrobiotus persimilis''
Binda & Pilato, 1972
* ''
Macrobiotus personatus''
Biserov, 1990
* ''
Macrobiotus peteri''
Pilato, Binda & Catanzaro, 1991
* ''
Macrobiotus pisacensis''
Kaczmarek, Cytan, Zawierucha, Diduszko & Michalczyk, 2014
* ''
Macrobiotus polonicus''
Pilato, Kaczmarek, Michalczyk & Lisi, 2003
* ''
Macrobiotus polyopus''
Marcus, 1928
* ''
Macrobiotus polypiformis''
Roszkowska, Ostrowska, Stec, Janko & Kaczmarek, 2017
* ''
Macrobiotus porifini''
Kuzdrowska, Mioduchowska, Gawlak, Bartylak, A. Kepel, M. Kepel & Kaczmarek, 2021
* ''
Macrobiotus primitivae''
de Barros, 1942
* ''
Macrobiotus psephus''
du Bois-Reymond Marcus, 1944
* ''
Macrobiotus pseudofurcatus''
Pilato, 1972
* ''
Macrobiotus pseudohufelandi''
Stec, Vecchi, Calhim & Michalczyk, 2021
* ''
Macrobiotus pseudopallarii
''Macrobiotus'' is a genus of tardigrades consisting of about 100 species within the family Macrobiotidae. Of genera within the phylum Tardigrada, ''Macrobiotus'' is one of the most species-abundant. ''Macrobiotus hufelandi'', identified by German ...
''
Stec, Vecchi & Michalczyk, 2021 in Stec et al. 2021
* ''
Macrobiotus punctillus''
Pilato, Binda & Azzaro, 1990
* ''
Macrobiotus radiatus''
Pilato, Binda & Catanzaro, 1991
* ''
Macrobiotus ragonesei''
Binda, Pilato, Moncada & Napolitano, 2001
* ''
Macrobiotus ramoli''
Dastych, 2005
* ''
Macrobiotus rawsoni''
Horning, Schuster & Grigarick, 1978
* ''
Macrobiotus rebecchii''
Stec, 2022
* ''
Macrobiotus recens''
Cuénot, 1932
* ''
Macrobiotus richtersi''
Pilato, Binda & Catanzaro, 1991
* ''
Macrobiotus ripperi''
Stec, Vecchi & Michalczyk, 2021 in Stec et al. 2021
* ''
Macrobiotus rybaki''
Stec & Vecchi, 2021 in Vecchi & Stec 2021
* ''
Macrobiotus sandrae''
Bertolani & Rebecchi, 1993
* ''
Macrobiotus santoroi''
Pilato & D'Urso, 1976
* ''
Macrobiotus sapiens''
Binda & Pilato, 1984
* ''
Macrobiotus scoticus''
Stec, Morek, Gąsiorek, Blagden & Michalczyk, 2017
* ''
Macrobiotus semmelweisi''
Pilato, Binda & Lisi, 2006
* ''
Macrobiotus serratus''
Bertolani, Guidi & Rebecchi, 1996
* ''
Macrobiotus seychellensis''
Biserov, 1994
* ''
Macrobiotus shonaicus
''Macrobiotus shonaicus'' () is a species of tardigrade in the family Macrobiotidae. it is only known from its type locality (biology), type locality: Tsuruoka, Japan. The species description was published in 2018. The insides of their first thr ...
''
Stec, Arakawa & Michalczyk, 2018
* ''
Macrobiotus siderophilus''
Bertolani et al., 2023
* ''
Macrobiotus sottilei''
Pilato, Kiosya, Lisi & Sabella, 2012
* ''
Macrobiotus terminalis''
Bertolani & Rebecchi, 1993
* ''
Macrobiotus trunovae''
Biserov, Pilato & Lisi, 2011
* ''
Macrobiotus vanescens''
Pilato, Binda & Catanzaro, 1991
* ''
Macrobiotus vladimiri''
Bertolani, Biserov, Rebecchi & Cesari, 2011
* ''
Macrobiotus wandae''
Kayastha, Berdi, Miaduchowska, Gawlak, Łukasiewicz, Gołdyn & Kaczmarek, 2020
* ''
Macrobiotus wuyishanensis''
P. Zhang & X.-Z. Sun, 2014
* ''
Macrobiotus yunshanensis''
Yang, 2002
References
{{taxonbar, from=Q4133332
Tardigrade genera
Parachela (tardigrade)