''Sphaerocarpos muccilloi'' is a species of

liverwort Liverworts are a group of non-vascular land plants forming the division Marchantiophyta (). They may also be referred to as hepatics. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry ...

in the family

Sphaerocarpaceae Sphaerocarpaceae is a Family (biology), family of liverworts known as bottle liverworts. Approximately ten species are included in this family, most of them in the genus ''Sphaerocarpos'', but one additional species in the genus ''Geothallus''. ...

Description

''Sphaerocarpos muccilloi'' grows in pale green mats. The

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

tissue is around five cells thick towards the center of the plant, but becomes as thin as one cell towards the edges. Those cells towards the edges are square or rectangular in shape, and are 56–108 micrometers (μm) long by 30–50 μm wide. The

involucre In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also look ...

which protects the plant's

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

is aggregate and oval- or cylindrical-shaped. It has a length of 1–2 millimeters (mm) and the opening is 170–280 μm wide.Vianna, 58.

Dioecy

''S. muccilloi'' is a

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

species, which means individual plants will have either male or female reproductive organs instead of both. The female plants grow roughly in a circular shape and are about 5–8 mm long. They are lobed, and the lobes grow upwards somewhat, with many

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be un ...

s on their undersides. The male plants are more oval-shaped and also lobed. They are purple in color and usually have one fork. They are also smaller, growing only 1–3 mm long. The male sex organ, the

antheridium An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. The androecium is al ...

, is globular and 80–112 μm in diameter. It is supported by three stalk cells. The spore capsule is large (0.8–1 mm) and is embedded in the thallus. It has short hairs (

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

) and a bulbous foot. The spores are yellowish-brown and grow in tetrads which are 108–180 μm wide. The spores are around 60–90 μm wide and are areolate.

Similar species

''Sphaerocarpos muccilloi'' is closely related to other species of ''Sphaerocarpos''. However, it can be told apart from each through different morphological features. Its

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s separate at maturity from another place on the plant than in '' S. donnellii'' and '' S. cristatus'', and they are a different color from the bright yellow spores of '' S. stipitiatus.'' The differences in spores are more minute when comparing to '' S. hians'', '' S. michelii'', '' S. texanus'', and '' S. drewiae'', but each of them have different sized spores and various patterns of meshes and ridges which make them unique.Vianna, 60.

Taxonomy

''Sphaerocarpos muccilloi'' represents the

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

ian population of

, being the only species of the family found in the country.Bordin ''et al'', 1. It was first recognized as a distinct species by Eny Vianna in 1981, following the analysis of specimens collected from an earlier trip to Brazil in 1973.Vianna, 58.

Distribution and habitat

According to the

Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological sp ...

of Rio Grand do Sul, ''S. muccilloi'' is a

Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

species which can be found only in a few localities within the Brazilian state. These include the type locality of

Porto Alegre Porto Alegre (, ; , ; ) is the capital and largest city of the Brazilian Federative units of Brazil, state of Rio Grande do Sul. Its population of roughly 1.4 million inhabitants (2022) makes it the List of largest cities in Brazil, 11th-most p ...

and two locations surrounding it,

São Leopoldo São Leopoldo () (Portuguese for ''Saint Leopold'') is a Brazilian industrial city located in the south state of Rio Grande do Sul. Geography It occupies a total area of 103.9 km2 (around 80 km2 urban area) at ''circa'' 30 km fr ...

and

Ivoti Ivoti is a municipality in the Brazilian state of Rio Grande do Sul, located in the Porto Alegre metropolitan area. The population is 24,690 (2020 est.) in an area of 63.15 km2. History Originally occupied by indigenous people since 12,00 ...

. However, because of the high levels of human habitation in these places and the time passed since the last observations of the species there, it is likely that ''S. muccilloi'' is no longer present in these locations.Bordin ''et al'', 2. In 2017, the species was recorded in the

Paleobotanical Sites of Arenito Mata Paleobotany or palaeobotany, also known as paleophytology, is the branch of botany dealing with the recovery and identification of plant fossils from geological contexts, and their use for the biological reconstruction of past environments (pale ...

of Santana do Livramento. The species is most commonly found in areas of light shade on damp soil. It has been recorded among

petrified wood Petrified wood (from Ancient Greek meaning 'rock' or 'stone'; literally 'wood turned into stone'), is the name given to a special type of ''fossilized wood'', the fossilized remains of terrestrial plant, terrestrial vegetation. ''Petrifaction ...

and

hornwort Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a ...

s of the genus ''

Phaeoceros ''Phaeoceros'' is a genus of hornworts in the family Notothyladaceae. The genus is global in its distribution. Its name means 'yellow horn', and refers to the characteristic yellow spores that the plants produce in the horn-shaped sporophyte. T ...

''.

References

Notes

Bibliography

* * * {{Taxonbar, from=Q17264738 Sphaerocarpales Critically endangered flora of South America Flora of Rio Grande do Sul