Macrostomum lignano
Encyclopedia
Macrostomum lignano is a free-living, hermaphroditic flatworm
. It is transparent and of small size (adults reaching about 1.7 mm), and is part of the intertidal sand meiofauna of the Adriatic Sea
. Originally a model organism for research on developmental biology
and the evolution of the bilaterian body plan
,
it has since expanded to other important fields of research such as sexual selection
and sexual conflict
s, ageing
and the evolution of the bilaterian body plan
, ecotoxicology
, and, more recently, genomics
", meaning "big-mouthed", derives from the Greek
μάκρος makros, "large", and στόμα, stoma, mouth. The species name, lignano, comes from the location where this species has so far been found, the sandy beaches and lagoons at and near Lignano Sabbiadoro
, Italy
.
s, is an unsegmented
, soft-bodied bilaterian without body cavity
, and no specialized circulatory
or respiratory
organ
s. Unlike many other flatworms, its body is not flattened but round in cross section, the diffusion
of oxygen
and nutrients to the different body parts being possible due to its small size (adults reach about 1.7 mm in length)
Macrostomum lignano is a simultaneous hermaphrodite. Adults (about 12 days after hatching
, at 20°C and ad libitum
food) have a pair of ovaries and a pair of testes, and simultaneously produce gametes in both sex functions. Reproduction is by outcrossing
, with worms mating
reciprocally.
ns, gastrotrich
s, nematode
s, and numerous groups of crustaceans like copepod
s.
Density varies widely, there can be hundreds of individuals in a tablespoon of sand. When conditions deteriorate, for instance due to desiccation or increased salinity, M. lignano can encyst by secreting a soft shell which can be dissolved within minutes once conditions improve .
To date, M. lignano has only been found in locations near Lignano Sabbiadoro
(Italy): tidal lagoons on the eastern side of Bibione and the Isola di Martignano, natural and semi-natural beaches of the Laguna di Marano and the Isola Valle Vechia.
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
. It is transparent and of small size (adults reaching about 1.7 mm), and is part of the intertidal sand meiofauna of the Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
. Originally a model organism for research on developmental biology
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
and the evolution of the bilaterian body plan
Body plan
A body plan is the blueprint for the way the body of an organism is laid out. An organism's symmetry, its number of body segments and number of limbs are all aspects of its body plan...
,
it has since expanded to other important fields of research such as sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...
and sexual conflict
Sexual conflict
Sexual conflict occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly the mode and frequency of mating, leading to an evolutionary arms race between males and females. The conflict encompasses the actions and behaviors of both sexes to influence...
s, ageing
Ageing
Ageing or aging is the accumulation of changes in a person over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline...
and the evolution of the bilaterian body plan
Body plan
A body plan is the blueprint for the way the body of an organism is laid out. An organism's symmetry, its number of body segments and number of limbs are all aspects of its body plan...
, ecotoxicology
Ecotoxicology
Ecotoxicology is the study of the effects of toxic chemicals on biological organisms, especially at the population, community, ecosystem level. Ecotoxicology is a multidisciplinary field, which integrates toxicology and ecology....
, and, more recently, genomics
Genomics
Genomics is a discipline in genetics concerning the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis,...
Name
The genus name "MacrostomumMacrostomum
Macrostomum is a genus of Platyhelminthes with worldwide distribution, with over a hundred species described . These hermaphroditic, free-living flatworms are small in size, with large species reaching only about 5 mm...
", meaning "big-mouthed", derives from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
μάκρος makros, "large", and στόμα, stoma, mouth. The species name, lignano, comes from the location where this species has so far been found, the sandy beaches and lagoons at and near Lignano Sabbiadoro
Lignano Sabbiadoro
Lignano Sabbiadoro is a village and comune within the province of Udine, in the Friuli-Venezia Giulia region . It is one of the main summer resorts in northern Italy and in the Adriatic Sea coast.-History:...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
.
Biology
Macrostomum lignano, like all other flatwormFlatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
s, is an unsegmented
Segmentation (biology)
Segmentation in biology refers to either a type of gastrointestinal motility or the division of some animal and plant body plans into a series of repetitive segments. This article will focus on the segmentation of animal body plans, specifically using the examples of the phyla Arthropoda,...
, soft-bodied bilaterian without body cavity
Coelom
The coelom is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size...
, and no specialized circulatory
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
or respiratory
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
s. Unlike many other flatworms, its body is not flattened but round in cross section, the diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and nutrients to the different body parts being possible due to its small size (adults reach about 1.7 mm in length)
Macrostomum lignano is a simultaneous hermaphrodite. Adults (about 12 days after hatching
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
, at 20°C and ad libitum
Ad libitum
Ad libitum is Latin for "at one's pleasure"; it is often shortened to "ad lib" or "ad-lib"...
food) have a pair of ovaries and a pair of testes, and simultaneously produce gametes in both sex functions. Reproduction is by outcrossing
Outcrossing
Outcrossing is the practice of introducing unrelated genetic material into a breeding line. It increases genetic diversity, thus reducing the probability of all individuals being subject to disease or reducing genetic abnormalities...
, with worms mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
reciprocally.
Ecology and Distribution
Macrostomum lignano lives interstitially in sandy habitats, at the intertidal or upper-intertidal zone, usually in the upper 5 to 10 mm. It only needs a little humidity in the sand to survive, but it can also be found underwater during high tide. It favours protected areas with no or very low wave exposure like tidal lagoons. M. lignano feeds primarily on diatoms, but it has been observed to eat small invertebrates and, occasionally, eggs (even conspecific, and sometimes its own). M. lignano can often be found with other turbellariaTurbellaria
The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes , and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to in length...
ns, gastrotrich
Gastrotrich
The gastrotrichs are a phylum of microscopic animals abundant in fresh water and marine environments. Most fresh water species are part of the periphyton and benthos...
s, nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s, and numerous groups of crustaceans like copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s.
Density varies widely, there can be hundreds of individuals in a tablespoon of sand. When conditions deteriorate, for instance due to desiccation or increased salinity, M. lignano can encyst by secreting a soft shell which can be dissolved within minutes once conditions improve .
To date, M. lignano has only been found in locations near Lignano Sabbiadoro
Lignano Sabbiadoro
Lignano Sabbiadoro is a village and comune within the province of Udine, in the Friuli-Venezia Giulia region . It is one of the main summer resorts in northern Italy and in the Adriatic Sea coast.-History:...
(Italy): tidal lagoons on the eastern side of Bibione and the Isola di Martignano, natural and semi-natural beaches of the Laguna di Marano and the Isola Valle Vechia.
External links
- Turbellaria database
- www.macrostomum.net
- http://evolution.unibas.ch/scharer/research/current_research/macrostomum_overview.htmlEvolutionary Research on Macrostomum species at the University of BaselUniversity of BaselThe University of Basel is located in Basel, Switzerland, and is considered to be one of leading universities in the country...
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