The embryonic development stage lasts for 14 hours; development then continues through four successive larval stages with ecdysis between each stage L1, L2, L3, and L4 ultimately leading to the development of a young male or female adult worm. Adverse environmental conditions such as overcrowding and lack of food can result in the formation of an intermediate larval stage known as the dauer larva.
Arthropods are the largest grouping of animals all of which have jointed legs and an exoskeleton made of chitin. Arthropods dominate the animal kingdom with an estimated 85 percent of known species included in this phylum; many arthropods are as yet undocumented.
The principal characteristics of all the animals in this phylum are functional segmentation of the body and presence of jointed appendages.
Arthropods also show the presence of an exoskeleton made principally of chitin, which is a waterproof, tough polysaccharide. Phylum Arthropoda is the largest phylum in the animal world; insects form the single largest class within this phylum.
Arthropods are eucoelomate, protostomic organisms. Phylum Arthropoda includes animals that have been successful in colonizing terrestrial, aquatic, and aerial habitats.
This phylum is further classified into five subphyla: Trilobitomorpha trilobites, all extinct , Hexapoda insects and relatives , Myriapoda millipedes, centipedes, and relatives , Crustaceans crabs, lobsters, crayfish, isopods, barnacles, and some zooplankton , and Chelicerata horseshoe crabs, arachnids, scorpions, and daddy longlegs. Trilobites are an extinct group of arthropods found chiefly in the pre-Cambrian Era that are probably most closely related to the Chelicerata. These are identified based on fossil records.
Trilobite fossil : Acadoparadoxides , possibly A. A unique feature of animals in the arthropod phylum is the presence of a segmented body and fusion of sets of segments that give rise to functional body regions called tagma.
Tagma may be in the form of a head, thorax, and abdomen, or a cephalothorax and abdomen, or a head and trunk. A central cavity, called the hemocoel or blood cavity , is present; the open circulatory system is regulated by a tubular, or single-chambered, heart.
Respiratory systems vary depending on the group of arthropod. Insects and myriapods use a series of tubes tracheae that branch through the body, open to the outside through openings called spiracles, and perform gas exchange directly between the cells and air in the tracheae.
Other organisms use variants of gills and lungs. Aquatic crustaceans utilize gills, terrestrial chelicerates employ book lungs, and aquatic chelicerates use book gills. The book lungs of arachnids scorpions, spiders, ticks, and mites contain a vertical stack of hemocoel wall tissue that somewhat resembles the pages of a book.
This allows both sides of the tissue to be in contact with the air at all times, greatly increasing the efficiency of gas exchange. The gills of crustaceans are filamentous structures that exchange gases with the surrounding water.
Book gills : The ventral side of a horseshoe crab showing the book gills located near the telson tail. These gills flap back and forth bringing oxygen to the blood. Groups of arthropods also differ in the organs used for excretion. Crustaceans possess green glands while insects use Malpighian tubules, which work in conjunction with the hindgut to reabsorb water while ridding the body of nitrogenous waste.
The cuticle is the covering of an arthropod. It is made up of two layers: the epicuticle, which is a thin, waxy, water-resistant outer layer containing no chitin; and the chitinous procuticle, which is beneath the epicuticle. Chitin is a tough, flexible polysaccharide. During this time, the animal is vulnerable to predation. The Phylum Arthropoda includes a wide range of species divided into the subphyla: Hexapoda, Crustacea, Myriapoda, and Chelicerata.
The name Hexapoda denotes the presence of six legs three pairs in these animals, which differentiates them from the number of pairs present in other arthropods. Hexapods are characterized by the presence of a head, thorax, and abdomen, constituting three tagma. The thorax bears the wings as well as six legs in three pairs. Many of the common insects we encounter on a daily basis, including ants, cockroaches, butterflies, and flies, are examples of Hexapoda.
Among the hexapods, the insects are the largest class in terms of species diversity as well as biomass in terrestrial habitats. Typically, the head bears one pair of sensory antennae, mandibles as mouthparts, a pair of compound eyes, and some ocelli simple eyes , along with numerous sensory hairs. The thorax bears three pairs of legs one pair per segment and two pairs of wings, with one pair each on the second and third thoracic segments. The abdomen usually has eleven segments and bears reproductive apertures.
Hexapoda includes insects that are winged like fruit flies and wingless like fleas. Insect showing wings and body segments : Protaetia fieberi in flight posture. Hexapods are characterized by having three distinct tagma, or body segments. Kristensen RM. Loricifera, a new phylum with Aschelminthes characters from meiobenthos. Z Zool Syst Evol 21 : — Microscopic anatomy of invertebrates, Vol. Comparative morphology: do the ultrastructural investigations of Loricifera and Tardigrada support the clade Ecdysozoa?
Suppression of long-branch attraction artefacts in the animal phylogeny using a site-heterogeneous model. Spiralian phylogeny informs the evolution of microscopic lineages. Curr Biol 25 : — 6. Complete mitochondrial genome of a tongue worm Armillifer agkistrodontis. Korean J Parasitol 54 : — 7. The oldest known priapulid-like scalidophoran animal and its implications for the early evolution of cycloneuralians and ecdysozoans.
Evol Dev 16 : — A molecular palaeobiological exploration of arthropod terrestrialisation. J Paleontol 88 : — Maas A. Gastrotricha, Cycloneuralia and Gnathifera: the fossil record.
In: Schmidt-Rhaesa A , editor. Mallatt J , Giribet G. Mol Phylogenet Evol 40 : — J Mol Evol 51 : — Assessing segmental versus non-segmental features in the ventral nervous system of onychophorans velvet worms. BMC Evol Biol 17 : 3.
Martin C , Mayer G. Neuronal tracing of oral nerves in a velvet worm—implications for the evolution of the ecdysozoan brain. Front Neuroanat 8 : 7. The study of Priapulus caudatus reveals conserved molecular patterning underlying different gut morphogenesis in the Ecdysozoa. BMC Biol 13 : The larval nervous system of the penis worm Priapulus caudatus Ecdysozoa. Mayer G. Origin and differentiation of nephridia in the Onychophora provide no support for the Articulata.
Zoomorphology : 1 — Selective neuronal staining in tardigrades and onychophorans provides insights into the evolution of segmental ganglia in panarthropods. BMC Evol Biol 13 : A revision of brain composition in Onychophora velvet worms suggests that the tritocerebrum evolved in arthropods. BMC Evol Biol 10 : Minelli A. Introduction: the evolution of segmentation.
Arthropod Struct Dev 46 : — 7. Phylogenomics resolves the timing and pattern of insect evolution. Science : — 7. Nielsen C. Proposing a solution to the Articulata-Ecdysozoa controversy. Zool Scr 32 : — Animal evolution: interrelationships of the living phyla. Oxford : Oxford University Press. Phylotranscriptomics to bring the understudied into the fold: monophyletic Ostracoda, fossil placement, and pancrustacean phylogeny. Mol Biol Evol 30 : — Biol Rev 91 : — Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda.
Nat Commun 3 : Bilaterian phylogeny: a broad sampling of 13 nuclear genes provides a new Lophotrochozoa phylogeny and supports a paraphyletic basal Acoelomorpha. Mol Biol Evol 26 : — First molecular data on the phylum Loricifera — an investigation into the phylogeny of Ecdysozoa with emphasis on the positions of Loricifera and Priapulida. Zool Sci 23 : — Mol Biol 39 : — The Opisthokonta and the Ecdysozoa may not be clades: stronger support for the grouping of plant and animal than for animal and fungi and stronger support for the Coelomata than Ecdysozoa.
Mol Biol Evol 22 : — Multigene analyses of bilaterian animals corroborate the monophyly of Ecdysozoa, Lophotrochozoa and Protostomia. The clade Ecdysozoa, perplexities and questions. Zool Anz : 43 — Piper R. Animal Earth: the amazing diversity of living creatures. An overview of arthropod genomics, mitogenomics, and the evolutionary origins of the arthropod proteome. Arthropod biology and evolution: molecules, development, morphology. Heidelberg : Springer. The complete mitochondrial genome of the onychophoran Epiperipatus biolleyi reveals a unique transfer RNA set and provides further support for the Ecdysozoa hypothesis.
Mol Biol Evol 25 : 42 — Mitochondrial genomes of Kinorhyncha: trnM duplication and new gene orders within animals. PLoS One 11 : e Rieger RM. Evolution of the cuticle in the lower Eumetazoa. Biology of the integument, Vol. Berlin : Springer. Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences. Ecdysozoan clade rejected by genome-wide analysis of rare amino acid replacements.
Mol Biol Evol 24 : — Molecular timetrees reveal a Cambrian colonization of land and a new scenario for ecdysozoan evolution. Curr Biol 23 : — 8. Ecdysozoan mitogenomics: Evidence for a common origin of the legged invertebrates, the Panarthropoda.
Genome Biol Evol 2 : — Ruppert EE. Introduction to the aschelminth phyla: a consideration of mesoderm, body cavities, and cuticle.
The position of the Arthropoda in the phylogenetic system. J Morphol : — Brains in Gastrotricha and Cycloneuralia — a comparison. Proteomic analysis of tardigrades: towards a better understanding of molecular mechanisms by anhydrobiotic organisms. PLoS One 5 : e Scholtz G. The Articulata hypothesis - or what is a segment? Org Divers Evol 2 : — Is the taxon Articulata obsolete?
Arguments in favour of a close relationship between annelids and arthropods. The new panorama of animal evolution. A phylogenomic solution to the origin of insects by resolving crustacean-hexapod relationships. Curr Biol doi These pharyngeal elements are poorly defined in shape but are consistent in position.
However, this assumption relies on the assumption that Acosmia is a priapulan—there is otherwise no evidence of pharyngeal eversibility in Acosmia. Following on from the terminal mouth and muscular pharynx, the intestine flows the length of the body. The intestine widens in the posterior trunk compared to the anterior proboscis and shows three-dimensional sediment infilling throughout Figs. Neural tissues in the Chengjiang Biota are well known among arthropods [ 30 , 31 , 32 , 33 , 34 ], and have also been reported in priapulans [ 35 ].
The veracity of these interpretations has recently been supported by similar reports of temporally contemporaneous neural preservation in North American deposits [ 36 ]. As such, Acosmia is resolved within the ecdysozoan stem group. All other known ecdysozoans are therefore within the crown group. When coding the putative spines of Acosmia as circumoral structures character , Additional File 6 rather than coding for their absence, the position of Acosmia as sister group to other Ecdysozoa is stable under equal and implied weights parsimony, maximum likelihood and Bayesian inference.
Summary of tree searches, showing simplified topology of each optimality criterion. See Methods for explanation of nodal support values.
See supplementary material for full topologies. Silhouettes from phylopic. Acosmia life reconstruction credited to Franz Anthony. Within Spiralia, the sister group relationships between some phyla i. Entoprocta were variable across optimality criteria, but the basic tree shape conforms to that of Vinther and Parry [ 37 ] from which the dataset is partly derived additional data files 2 , 3 , 4 , 5.
A basal split between a clade comprising Gnathostomulida, Micrognathozoa, Rotifera and Chaetognatha i. Gnathifera and a clade similar to Lophotrochozoa comprising Nemertea, Entoprocta, Bryozoa, Brachiopoda Phoronida, Platyhelminthes, Annelida and Mollusca was almost constant.
Only Gastrotricha did not conform to this split consistently. Gastrotricha was recovered as the sister group to Gnathifera in all parsimony analyses Additional Files 2 , 3 , the sister group to other Spiralia using maximum likelihood Additional File 4 , and unresolved in a basal spiralian polytomy with Gnathifera and the Lophotrochozoa-like clade using Bayesian inference Additional File 5.
Parsimony Additional Files 2 , 3 and maximum-likelihood Additional File 4 tree searches resolved Cycloneuralia as monophyletic, whereas Bayesian inference Additional File 5 recovered a polytomy comprising Nematoida, Scalidophora and Panarthropoda.
Strict consensuses of equal and implied weights parsimony tree searches each recovered a polytomy comprising Nematoda, Nematomorpha and Scalidophora, whereas maximum likelihood and Bayesian inference recovered Nematoida as a monophylum. The relationships between scalidophorans sampled were mostly unresolved by parsimony and Bayesian inference, though all analyses recovered a sister group relationship between Priapulus and Xiaoheiqingella i. Priapulida , between Nanaloricidae and Pliciloricidae i.
Miskoiidae, also recovered by Bayesian inference and equal weights , Palaeoscolecida, and a clade comprising Eximipriapulus , Ottoia , Eopriapulites and Eokinorhynchus. The topology of Panarthropoda was relatively labile across optimality criteria.
The lobopodians Diania , Paucipodia and Microdictyon were resolved in stem group Panarthropoda by maximum likelihood Additional File 4 and Bayesian inference Additional File 5.
Tardigrada was resolved as sister group to other panarthropods using implied weights, but was recovered as the sister group to total group Onychophora in all other optimality criteria. The stem lineage of Arthropoda was consistent across optimality criteria, comprising in stemward to crownward order Megadictyon, Kerygmachela, Pambdelurion , Hurdia, and Fuxianhuia.
The exception was implied weights, which also included Aysheaia as the most basal member of total group Arthropoda. The stem lineage of Onychophora was less stable across optimality criteria, but always included Luolishaniidae, Hallucigenia, Onychodictyon and Cardiodictyon. Ancestral state reconstructions calculated here constitute the probability of the state of absence 0 vs the probability of the state of presence 1 for six key morphological characters Tables 2 and 3 , and Fig.
Therefore, it is more probable than not that the crown group ancestor of Ecdysozoa had an adult terminal mouth, based on the distribution of that character state in the topology and the model of morphological evolution employed by the analysis. The latter is the MK model, analogous to basic principles of Jukes Cantor 69, i.
Visualization of ancestral character state reconstructions. Percentages in pie charts represent posterior probability of the state of presence 1 for that character. Posterior probabilities of ancestral character states were affected by the two contrasting topologies by small amounts in all cases. The coding of ecdysozoan fossils into the phylogenetic matrix was informed by taphonomic decay studies of extant taxa [ 42 , 43 , 44 ].
This was necessary to deduce the designation of character states as unknown? Most significantly for our interpretations, the decay process in Priapulus was taken into account [ 29 ] when designating the character states of Acosmia —which was previously regarded as a priapulan [ 20 ].
Decay experiments showed that scalids and pharyngeal armature were among the most recalcitrant of all anatomical structures in the decay of Priapulus. These morphological features do not occur in Acosmia, but other cuticular structures designated highly recalcitrant by Sansom [ 29 ] do occur in Acosmia such as annulations and trunk papillae though probably not directly homologous to the anterior and posterior papillae of Acosmia.
This shows that the cuticular anatomy of Acosmia has been preserved in sufficient fidelity for scalids and pharyngeal teeth to be present if they occurred. As they do not occur in any known specimen, their absence in Acosmia is likely to be genuine and not the result of a taphonomic bias.
Furthermore, Sansom [ 29 ] found no evidence for stem-ward slippage among priapulans when decay-informed character coding was employed, as only the most recalcitrant characters i. Murdock et al. Therefore, stem-ward slippage i. Taphonomically informed phylogenetic analyses according to four alternative optimality criteria resolved Acosmia as a stem lineage ecdysozoan Fig.
Acosmia therefore represents among the only direct palaeontological models to hypothesise how ecdysozoans might have originated and diversified. As such, it is necessary to consider the ecology of Acosmia. Acosmia is a little known Chengjiang fossil, appearing only in successive review-style compilations of the fauna [ 20 , 22 , 23 , 24 , 25 ], and is listed as a priapulan each time—though authors are consistently doubtful of the priapulan affinity.
Figures 1 , 2 , the idea being that Acosmia , with its infilled through gut and muscular pharynx, had a deposit-feeder lifestyle in the upper reaches of the muddy sediment like a lugworm in a U-shaped burrow. Assuming this reconstruction is accurate, it could be inferred that the acquisition of pharyngeal armament i.
However, this would also rely on the assumption that Acosmia represents a typical member of the ecdysozoan stem-lineage and had not adapted to a deposit feeding lifestyle independently. Characters selected for ancestral state reconstruction constituted traits that might be inferred as ecdysozoan plesiomorphies from studies of crown group taxa—though of course this is dependent on the topology under consideration.
Characters considered plesiomorphies are optimised in Fig. Adult terminal mouth: In contrast to other bilaterian groups, an adult terminal mouth has been proposed as ancestral for Ecdysozoa [ 19 , 48 , 49 ]. Extant arthropods and onychophorans lack this character in addition to some nematodes and some heterotardigrades —but the fossil record indicates that this is the result of secondary modification [ 19 ].
Most non-arthropod Cambrian ecdysozoans e. For example, the stem group arthropods Pambdelurion and Hurdia have ventral mouths. However, these taxa are located crownward of arthropod taxa with terminal mouths such as Megadictyon , and so the ventral orientation is inferred to be secondary. Pharyngeal armature: Ecdysozoans are not the only protostomes with prominent pharyngeal structures.
Various spiralian groups exhibit jaw and tooth like structures within their pharynxes, notably the Gnathifera [ 50 ]. However, the pharyngeal structures of gnathiferans are clearly distinct from those of ecdysozoans.
Gnathiferan pharynxes are equipped with bilaterally symmetrical and complex jaw apparatuses [ 50 ], which do not resemble the radially arranged teeth and stylets of extant and fossil ecdysozoans. As such, they were not scored as equivalent structures here in the phylogenetic character matrix. Ecdysozoan pharyngeal armature varies by group and was scored on a simple absence or presence basis in the character matrix under the assumption that these structures are homologous based on their consistent position ornamenting the cuticle of the pharynx, and their typically radial symmetry.
With some exceptions extant Onychophora for example , the pharynxes of ecdysozoans are commonly armed with teeth, spines or stylets etc. Little has been done to characterise the homology of these structures across the diversity of Ecdysozoa.
However, the discovery of pharyngeal teeth of a similar nature between Cambrian cycloneuralians e. Priapulans often exhibit cuspidate pharyngeal teeth e. Halicryptus spinulosus [ 59 ] which are arranged in rings of five-fold symmetry quincunxes. These are mirrored in some exceptionally preserved priapulan-like fossils such as Ottoia prolifica [ 53 ] from the Burgess Shale.
Other less obviously priapulan-like fossil scalidophorans exhibit pharyngeal teeth that are more simple and spinose, but are similarly radial in their arrangement—for example the phosphatic microfossil Eokinorhynchus rarus [ 13 , 60 ] from the Fortunian of Sichuan Province, China.
Kinorhynchs and loriciferans lack pharyngeal teeth but are themselves armed with specialised radial pharyngeal armature. Nebelsick [ 61 ] reported three quincunxes of articulating pharyngeal stylets in the cyclorhagid Echinoderes capitatus , and determined they were sensory in function.
Loriciferans also bear stylets, but they are oral features associated with the extensible buccal tube rather than the pharynx [ 62 ]. Whether this represents a migration of an ancestrally pharyngeal structure is unknown. However, nanaloricid loriciferans at least bear a triradial pattern of rows of thickened cuticular elements known as placoids [ 62 ].
The topologies presented here would suggest that the pharyngeal armament of kinorhynchs and loriciferans represent derived morphologies, especially given the similarity of priapulan teeth to those of some panarthropods [ 18 , 55 ]. Nematoid pharynxes are more problematic to interpret in an evolutionary sense, as the fossil record of the group is limited to comparatively younger crown group taxa. The oldest nematoid fossil is Palaeonema phyticum [ 63 ], which is comparable to some extant groups of nematodes.
Nothing is known about the nematoid stem group. Nematodes commonly bear stylets associated with the pharynx—especially plant parasites, but it is not clear that these structures are homologous to the teeth, stylets and placoids of other groups as they lack the radially oriented arrangement. Larval nematomorphs do show a radial pattern to their armature, but is not clear that these hexaradial piercing stylets are associated with the pharynx, the musculature of which is highly reduced in Nematomorpha [ 21 , 26 ].
Therefore, we infer that pharyngeal armature of the kind exhibited by cycloneuralians and lobopodians is a derived character for the ecdysozoan crown group and not ancestral for Ecdysozoa. Circumoral structures: Virtually all ecdysozoans, other than crown group onychophorans and arthropods crownward of radiodonts, show some form of circumoral structures.
This refers to cuticular elements arranged radially around the axis of their mouth opening, resulting in an anterior plane of radial symmetry in addition to the anterior—posterior axis of bilateral symmetry.
In this fashion, scalidophorans exhibit rings of scalids upon their introvert [ 21 ], nematoids may exhibit radial hooks or cephalic sensillae and setae [ 21 , 64 , 65 ], tardigrades exhibit a buccal ring of lamellae [ 58 , 66 ], and the fossil stem groups of both arthropods and onychophorans similarly show rings of plate-like lamellae [ 14 , 55 , 56 , 67 ].
This has been discussed previously as an ancestral character for Ecdysozoa [ 14 ], though the homology of these highly variable structures i. A recent study [ 68 ] described the introvert and pharyngeal armature of the Chengjiang worm Mafangscolex sinensis —Palaeoscolecida sensu stricto [ 17 ]—and postulated that a hexaradially-ornamented proboscis may be an ancestral ecdysozoan character.
Similarly, the authors of a study describing Eopriapulites sphinx —a Fortunian stem group scalidophoran preserved as a phosphatic microfossil—made a similar hypothesis regarding the ecdysozoan groundplan [ 69 ].
This is because hexaradial symmetry is widespread among the circumoral structures of both fossil and extant Ecdysozoa except for some Scalidophora, such as extant Kinorhyncha and Priapulida , and because the authors infer that palaeoscolecids are not stem group priapulans as reported by some analyses [ 17 ]. Yang et al. Our study mostly does not controvert the findings of Yang et al. As the monophyly of Scalidophora has yet to be demonstrated convincingly in phylogenomic studies, we hypothesise that palaeoscolecids such as Mafangscolex may possibly represent stem group Ecdysozoa as Yang et al.
Therefore, circumoral structures and their inferred plesiomorphic hexaradial symmetry are a derived character within Ecdysozoa, and not ancestral for Ecdysozoa. As such, palaeoscolecids are likely to be closer to the ecdysozoan crown group than Acosmia , if not within it as scalidophorans. Annulation: Fossil and extant ecdysozoans typically bear an annulated trunk, that is, transverse cuticular rings along their anterior—posterior body axis.
Exceptions include crown group and upper stem group arthropods [ 70 ], as well as kinorhynchs and loriciferans—which are all inferred as secondary losses due to the specialised trunk morphology of these groups.
Arthropods and kinorhynchs are segmented and covered by metamerically repeated dorsal and ventral plates, whereas loriciferans are encased within a corset-like lorica. Therefore, an annulated trunk is well supported here as an ancestral character for ecdysozoans. This form of circumoral armature was therefore recoded as absent in nematoids, as opposed to present as in Vinther and Parry [ 37 ]. As such, scalids are likely autapomorphic for Scalidophora, and they adorn a retractable anterior proboscis known as the introvert.
However, this inference is impeded by the lack of phylogenomic support for the monophyly of Scalidophora. What little molecular phylogenetics has been done has resolved the Loricifera in some unconventional positions in studies using only targeted Sanger sequencing, [ 71 , 72 ] but also as the sister group to Priapulida in a phylogenomic-scale study that did not include Kinorhyncha [ 52 ]. A sister group relationship between Priapulida and Kinorhyncha has been recovered by multiple studies utilizing different datasets that lacked Loricifera [ 39 , 73 , 74 ].
The only phylogenomic study with a taxon sample covering Priapulida, Kinorhyncha and Loricifera recovered scalidophoran paraphyly at the base of Ecdysozoa—with Loricifera as sister to Nematoda or Nematoida [ 40 ]. Scalidophoran paraphyly at the base of Ecdysozoa suggests the scalid-covered introvert could be an ancestral ecdysozoan character lost by Nematoida and Panarthropoda—an idea endorsed in some palaeontological studies [ 68 ].
Topologies employed here however all assumed monophyly of Scalidophora based on our own analyses see Fig. This process of molting is called ecdysis, and gives the group its name.
Also, what are the Synapomorphies of the Lophotrochozoans and Ecdysozoans? Ecdysozoans have the ability to shed their exoskeleton several times throughout their life span, whereas lophotrochozoan are the animals who possess a trochophore larvae and a feeding structure called lophophore. Ecdysozoa is a clade composed of eight phyla: the arthropods, tardigrades and onychophorans that share segmentation and appendages and the nematodes, nematomorphs, priapulids, kinorhynchs and loriciferans, which are worms with an anterior proboscis or introvert.
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Asked by: Eugene Langpap pets reptiles What is characteristic of all Ecdysozoans? Last Updated: 21st April, The most distinguishing and prominent feature of Ecdysozoans is their cuticle: a tough, but flexible exoskeleton that protects these animals from water loss, predators, and other aspects of the external environment.
All members of this superphylum periodically molt or shed their cuticle as they grow. Ujue Adashevsky Professional. What is the body covering of Ecdysozoans?
The Ecdysozoans are the most diverse group of animals, containing the nematode worms and the arthropods. These organisms have an external covering called a cuticle that protects their soft internal organs from water loss and the outside environment.
Rebbeca Hagele Professional. How do Ecdysozoans grow? This is in part because of the limitations a mineral skeleton imposes on an animal; growth can only occur by adding more mineral to the existing skeleton, which limits the animal's form as it grows. While many ecdysozoans also maintain their basic form throughout their life, molting removes this limitation. Shishi Roder Professional. What does Lophotrochozoa mean?
The taxon was established as a monophyletic group based on molecular evidence. Chelsea Lindheimer Explainer.
0コメント