''Buxbaumia'' (bug moss, bug-on-a-stick, humpbacked elves, or elf-cap moss)
is a genus of twelve species of
moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
(Bryophyta). It was first named in 1742 by
Albrecht von Haller
Albrecht von Haller (also known as Albertus de Haller; 16 October 170812 December 1777) was a Swiss anatomist, physiologist, naturalist, encyclopedist, bibliographer and poet. A pupil of Herman Boerhaave, he is often referred to as "the fa ...
and later brought into modern botanical nomenclature in 1801 by
Johann Hedwig
Johann Hedwig (8 December 1730 – 18 February 1799), also styled as Johannes Hedwig, was a German botanist notable for his studies of mosses. He is sometimes called the "father of bryology". He is known for his particular observations of sexual r ...
to commemorate
Johann Christian Buxbaum Johann Christian Buxbaum (no later than 5 October 1693 – 7 July 1730), was a German physician, botanist, entomologist and traveller.
He was born in Merseburg and studied medicine at the Universities of Leipzig, Wittenberg, Jena, and Leyden.
In ...
, a German physician and botanist who discovered the moss in 1712 at the mouth of the
Volga River
The Volga (; russian: Во́лга, a=Ru-Волга.ogg, p=ˈvoɫɡə) is the List of rivers of Europe#Rivers of Europe by length, longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Cas ...
.
The moss is microscopic for most of its existence, and plants are noticeable only after they begin to produce their reproductive structures. The asymmetrical spore capsule has a distinctive shape and structure, some features of which appear to be transitional from those in primitive mosses to most modern mosses.
Description
Plants of ''Buxbaumia'' have a much reduced
gametophyte
A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...
, bearing a
sporophyte
A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase.
Life cycle
The sporophyte develops from the zygote pr ...
that is enormous by comparison.
In most mosses, the gametophyte stage of the
life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
*Life-cycle hypothesis, ...
is both green and leafy, and is substantially larger than the spore-producing stage. Unlike these other mosses, the gametophyte of ''Buxbaumia'' is microscopic, colorless, stemless, and nearly leafless.
It consists exclusively of thread-like
protonema
A protonema (plural: protonemata) is a thread-like chain of cells that forms the earliest stage of development of the gametophyte (the haploid phase) in the life cycle of mosses. When a moss first grows from a spore, it starts as a ''germ tube'', ...
ta for most of its existence, resembling a thin green-black felt on the surface where it grows.
The plants are
dioicous
Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis rathe ...
, with separate plants producing the male and female organs.
Male plants develop only one microscopic leaf around each
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. Androecium is also ...
,
and female plants produce just three or four tiny colorless leaves around each
archegonium
An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...
.
Because of its small size, the gametophyte stage is not generally noticed until the stalked
sporangium
A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...
develops, and is locatable principally because the sporangium grows upon and above the tiny gametophyte.
The extremely reduced state of ''Buxbaumia'' plants raises the question of how it makes or obtains sufficient nutrition for survival. In contrast to most mosses, ''Buxbaumia'' does not produce abundant
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
and is
saprophytic
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...
.
It is possible that some of its nutritional needs are met by
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
that grow within the plant.
However, a recent study of the chloroplast genome in ''Buxbaumia'' failed to find any reduction in selective pressure on photosynthetic genes, suggesting that they are fully functional in photosynthesis, and that the moss is not
mycoheterotrophic
Myco-heterotrophy (from Greek μύκης , "fungus", ἕτερος ', "another", "different" and τροφή ', "nutrition") is a symbiotic relationship between certain kinds of plants and fungi, in which the plant gets all or part of its food fro ...
. This is also consistent with a lack of association between its rhizoids and nearby hyphae of soil fungi.
The sporophyte at maturity is between 4 and 11 mm tall.
The
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
capsule is attached at the top of the stalk and is distinctive,
being asymmetric in shape and oblique in attachment.
As with most other Bryopsida, the opening through which the spores are released is surrounded by a double
peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes.
In mosses
In mosses, ...
(diplolepidious) formed from the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
s of disintegrated cells.
The exostome (outer row) consists of 16 short articulated "teeth". Unlike most other mosses, the endostome (inner row) does not divide into teeth, but rather is a continuous pleated membrane around the capsule opening.
Only the genus ''
Diphyscium
''Diphyscium'' is a genus of mosses in the family Diphysciaceae. Members of this genus are small, perennial plants. The capsule does not elongate much, and remains buried among surrounding leaves.
There are fifteen species of ''Diphyscium''. ...
'' has a similar peristome structure, although that genus has only 16 pleats in its endostome, in contrast to the 32 pleats in ''Buxbaumia''.
''Diphyscium'' shares with ''Buxbaumia'' one other oddity of the sporophyte; the foot (stalk base) ramifies as a result of outgrowths, so much so that they may be mistaken for
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 unic ...
s.
Distribution and ecology
![Buxbaumiaaphylla](https://upload.wikimedia.org/wikipedia/commons/a/a5/Buxbaumiaaphylla.jpg)
Species of ''Buxbaumia'' may be found across much of the temperate to subarctic regions of the
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
, as well as cooler regions of
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
and
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
.
The moss is an
annual
Annual may refer to:
* Annual publication, periodical publications appearing regularly once per year
**Yearbook
** Literary annual
* Annual plant
* Annual report
* Annual giving
* Annual, Morocco, a settlement in northeastern Morocco
* Annuals (b ...
or
biennial plant
A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle.
Life cycle
In its first year, the biennal plant undergoes primary growth, during which its vegetative structures ...
and grows in
disturbed
Disturbed may refer to:
Books
* ''Disturbed'', a 2011 novel by Kevin O'Brien (author)
Film and TV
* ''Disturbed'' (film), a 1990 film starring Malcolm McDowell
* "Disturbed" (''Numb3rs''), a 2009 episode of ''Numb3rs''
* "The Disturbed", a 2 ...
habitats or as a
pioneer species
Pioneer species are hardy species that are the first to colonize barren environments or previously biodiverse steady-state ecosystems that have been disrupted, such as by wildfire.
Pioneer flora
Some lichens grow on rocks without soil, so m ...
.
The plants grow on decaying wood, rock outcrops, or directly on the soil.
They do not grow regularly or reliably at given locations, and frequently disappear from places where they have previously been found.
Sporophyte stages begin their development in the autumn, and are green through the winter months.
Spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s are mature and ready for dispersal by the late spring or early summer.
The spores are ejected from the capsule in puffs when raindrops fall upon the capsule's flattened top.
The asymmetric sporophytes of ''
Buxbaumia aphylla'' develop so that the opening is oriented towards the strongest source of light, usually towards the south.
The species often grows together with the diminutive
liverwort
The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of g ...
''
Cephaloziella'', which forms a blackish crust that is easier to spot than ''Buxbaumia'' itself.
Classification
''Buxbaumia'' is the only genus in the family Buxbaumiaceae, the order Buxbaumiales, and the subclass Buxbaumiidae.
It is the
sister group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
to all other members of class
Bryopsida
The Bryopsida constitute the largest class of mosses, containing 95% of all moss species. It consists of approximately 11,500 species, common throughout the whole world.
The group is distinguished by having spore capsules with teeth that are '' ...
.
Some older classifications included the
Diphysciaceae within the Buxbaumiales (or as part of the Buxbaumiaceae) because of similarities in the
peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes.
In mosses
In mosses, ...
structure,
or placed the Buxbaumiaceae in the
Tetraphidales.
However, recent phylogenetic studies based on genomic and transcriptomic data
clearly support it as the sister group of all other
Bryopsida
The Bryopsida constitute the largest class of mosses, containing 95% of all moss species. It consists of approximately 11,500 species, common throughout the whole world.
The group is distinguished by having spore capsules with teeth that are '' ...
.
The genus ''Buxbaumia'' includes twelve species:
Because of the simplicity of its structure, Goebel interpreted ''Buxbaumia'' as a primitive moss, transitional between the
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and mosses,
but subsequent research suggests that it is a secondarily reduced form.
The unusual peristome in ''Buxbaumia'' is now thought to be a transitional form between the nematodontous (cellular teeth) peristome of the
Polytrichopsida
Polytrichaceae is a common family of mosses. Members of this family tend to be larger than other mosses with a thickened central stem and a rhizome. The leaves have a midrib that bears photosynthetic lamellae on the upper surface. Species in th ...
and the arthrodontous (cell wall teeth) peristome of the Bryopsida.
References
External links
* W. B. Schofield. 2004. ''Bryophyte Flora of North America''
Buxbaumiaceae
{{Taxonbar, from1=Q135187, from2=Q12304697, from3=Q12304698, from4=Q12304699
Moss genera
Bryopsida