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Pteropods
Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. Most live in the top 10 m of the ocean and are less than 1 cm long. The monophyly of Pteropoda is the subject of a lengthy debate; they have even been considered as paraphyletic with respect to cephalopods. Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic. Pteropoda encompasses the two clades Thecosomata, the sea butterflies, and Gymnosomata, the sea angels. The Thecosomata ( "case-body") have a shell, while the Gymnosomata ("naked body") do not. The two clades may or may not be sister taxa; if not, their similarity (in that they are both pelagic, small, and transparent, and both groups swim using wing-like flaps (parapodia) which protrude from their bodies) may reflect convergent adaptation to their particular lifestyle. Taxonomy The group Pteropod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Butterfly
The Thecosomata (collective/plural: ''thecosomes'', meaning "case/shell-body"), or sea butterflies, are a taxonomic suborder of small, pelagic, free-swimming sea snails known as holoplanktonic opisthobranch gastropod mollusks, in the order Pteropoda (also included within the informal group Opisthobranchia). Most pteropods have some form of calcified shell, although it is often very light, even translucent. The sea butterflies include some of the world's most abundant gastropod species; as their large numbers are an essential part of the ocean food chain, they are a significant contributor to the oceanic carbon cycle. Morphology Unlike other sea snails, or even land snails, sea butterflies float and swim freely through the ocean, traveling along with the currents. This has led to a number of evolutionary adaptations in their bodies, including complete or near-complete loss of the shell and the gill in several families. Their gastropodal foot has also taken the form of two wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Angel
Sea angels (clade Gymnosomata) are a large group of small free-swimming sea slugs, classified into six separate families. They are pelagic opisthobranchs in the clade Gymnosomata within the larger mollusc clade Heterobranchia. Sea angels were previously considered to be pteropods. Sea angels are also sometimes known as "sea butterflies" but this is potentially misleading because the family Clionidae is just one of the families within this clade, and the term "sea butterfly" is also applied to the shelled Thecosomata. Recent molecular data suggest the Gymnosomata form a sister group to the Thecosomata (other planktonic, weakly or nonmineralized gastropods), but this long-standing hypothesis has also had some recent detractors. Distribution These organisms have a wide geographic range, from polar regions, under sea ice, to equatorial (tropic) seas. From spring to autumn, sea angels live at a depth of 200 m in the Sea of Okhotsk. In winter, they migrate to the coast of north H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Slug
Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod mollusks) that, over evolutionary time, have either entirely lost their shells or have seemingly lost their shells due to having a significantly reduced or internal shell. The name "sea slug" is often applied to Nudibranch, nudibranchs and a paraphyletic set of other marine gastropods without apparent Gastropod shell, shells. Sea slugs have an enormous variation in body shape, color, and size. Most are partially translucent. The often bright colors of Coral reef, reef-dwelling species imply that these animals are under constant threat of predators. Still, the color can warn other animals of the sea slug's toxic stinging cells (nematocysts) or offensive taste. Like all Gastropod, gastropods, they have small, razor-sharp teeth called Radula, rad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theropoda
Theropoda (; from ancient Greek [wiktionary:θηρίον, , (''therion'') "wild beast"; wiktionary:πούς, , wiktionary:ποδός, (''pous, podos'') "foot"]) is one of the three major groups (Clade, clades) of Dinosaur, dinosaurs, alongside Ornithischia and Sauropodomorpha. Theropods, both extant and extinct, are characterized by hollow bones and three toes and claws on each limb. They are generally classed as a group of saurischian dinosaurs, placing them closer to sauropodomorphs than to ornithischians. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Members of the subgroup Coelurosauria and possibly some other or all theropods were covered in Feather, feathers. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are currently represented by about 11,000 living species, making theropods the only group of dinosaurs alive today. Theropods first appeared during the Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Phylogenetics
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 determine the processes by which diversity among species has been achieved. The result of a molecular phylogenetics, phylogenetic analysis is expressed in a phylogenetic tree. Molecular phylogenetics is one aspect of molecular systematics, a broader term that also includes the use of molecular data in Taxonomy (biology), taxonomy and biogeography. Molecular phylogenetics and molecular evolution correlate. Molecular evolution is the process of selective changes (mutations) at a molecular level (genes, proteins, etc.) throughout various branches in the tree of life (evolution). Molecular phylogenetics makes inferences of the evolutionary relationships that arise due to molecular evolution and results in the construction of a phylogenetic tre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opisthobranch
Opisthobranchs () is a now informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping. Euopisthobranchia is a taxon containing a revised collection of opisthobranchs, and that taxon is considered monophyletic. Euopisthobranchia does not include some "traditional" opisthobranchs such as the Sacoglossa and the Acochlidiacea. The subclass Heterobranchia now contains all the species which used to be assigned to Opisthobranchia, plus all the species in the Pulmonata. The subclass Opisthobranchia included species in the order Cephalaspidea (bubble shells and headshield slugs), the sacoglossans, anaspidean sea hares, pelagic sea angels, sea butterflies, and many families of the Nudibranchia. ''Opisthobranch'' means "gills behind" (and to the right) of the heart. In contrast, ''Prosobranch'' means ''gills in front'' (of the heart). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Alexandre Lesueur
Charles Alexandre Lesueur (; 1 January 1778 in Le Havre – 12 December 1846 in Le Havre) was a French Natural history, naturalist, artist, and explorer. He was a prolific natural-history collector, gathering many type specimens in Australia, Southeast Asia, and North America, and was also responsible for describing numerous species, including the spiny softshell turtle (''Apalone spinifera''), smooth softshell turtle (''Apalone mutica, A. mutica''), and common map turtle (''Graptemys geographica''). Both Mount Lesueur and Lesueur National Park in Western Australia are named in his honor. Early life Charles Alexandre Lesueur was born on January 1, 1778, to Jean-Baptiste Denis Lesueur and Charlotte Thieullent. Charlotte died when Charles was sixteen years old, and Charles' maternal grandmother took care of him and his siblings. Charles attended the Collège du Havre and possibly the Ecole publique des mathématiques et d'hydrographie. He was in military service in a cadet b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
François Péron
François Auguste Péron (22 August 1775 – 14 December 1810) was a French naturalist and explorer. Life Péron was born in Cérilly, Allier, in 1775, the son of a tailor (not a harness maker as is frequently asserted). Although intended for the priesthood, due to the Revolution Péron reluctantly joined the 2nd Allier Volunteer Battalion in 1792 and helped defend besieged Landau. In the following year he was wounded and taken prisoner by Prussian forces near Hochspeyer in the Pfälzerwald. Imprisoned in the fortress of Magdeburg, he was not repatriated to France until 1794. Having lost the sight of an eye, Péron was invalided out of the army. For two years he was Town Clerk in Cérilly before gaining a scholarship to study medicine in Paris. While in Paris, Péron changed interests towards zoology, spending time at the Muséum d'histoire naturelle. In 1800, after an unhappy love affair, he sought to join Nicolas Baudin's expedition to Australian waters as an anthropolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection. Historically, adaptation has been described from the time of the ancient Greek philosophers such as Empedocles and Aristotle. In 18th and 19th-century natural theology, adaptation was taken as evidence for the existence of a deity. Charles Darwin and Alfred Russel Wallace proposed instead that it was explained by natural selection. Adaptation is related to biological fitness, which governs the rate of evolution as measured by changes in allele frequencies. Often, two or more species co-adapt and co-evolve as they develop adaptations tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is Cladogram#Homoplasies, homoplasy. The recurrent evolution of flight is a classic example, as flying pterygota, insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are ''analogous'', whereas ''homology (biology), homologous'' structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution, where related species evolve different trai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parapodium
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 lateral outgrowths that bear the chaetae. In several groups of sea snails and sea slugs, 'parapodium' refers to lateral fleshy protrusions. __TOC__ Annelid parapodia Most species of polychaete annelids have paired, fleshy parapodia which are segmentally arranged along the body axis. Parapodia vary greatly in size and form, reflecting a variety of functions, such as, anchorage, protection and locomotion. General description Parapodia in polychaetes can be uniramous (consisting of one lobe or ramus) but are usually biramous (two lobes or rami). In the latter case, the dorsal lobes are called notopodia and the ventral lobes neuropodia. Both neuropodia and notopodia may possess a bundle of chaetae (neurochaetae and notochaetae respectively ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
