| Plaxiphora albida | |
|---|---|
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| Dorsal surface of specimen from Tasmania on display at the Museo Civico di Storia Naturale di Milano. | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Polyplacophora |
| Order: | Chitonida |
| Family: | Mopaliidae |
| Genus: | Plaxiphora |
| Species: | P. albida |
| Binomial name | |
| Plaxiphora albida (Blainville, 1825) | |
| Synonyms | |
List
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Plaxiphora albida, the white Plaxiphora chiton, is a species of chiton in the family Mopaliidae.
The white Plaxiphora chiton reaches a common size of about 95mm, with a minimum and maximum length of 40–100 millimetres (1.6–3.9 in) and a width of 25–38 millimetres (0.98–1.50 in). The shell of this large chiton is dark green to brown, humped and oval shaped, with eight rough valves. Its girdle is leathery, brown with darker bars and with long bristles.
This species of Plaxiphora chiton was discovered by Dr. Charles Boyden on wave-exposed rocky shores of New Zealand. It was distinguishable enough from other chitons that it was described as a new species. These chitons do not have bristle-tufts on their girdle, and are low shore chiton. [1] They are also the largest giant chiton species found on Australia's coasts. [2]
Plaxiphora albida has radular, bulbous teeth. [3] Their teeth are iron-biomineralized, allowing them to more readily feed on algae attached to hard substrates like rock. Chitons not only feed on algae, but they are able to feed on sponges, corals or tunicates. [2] These molluscs have 17 teeth per row with one pair of those teeth being iron mineralized. Biomineralization strengthens the teeth and prevents mechanical wear, it makes the teeth harder. The tooth size of Plaxiphora albida is similar to that of the chiton species Acanthopleura hirtosa. In a study on mechanical tooth wear in chitons and limpets, P. albida teeth were observed to have had wear, and had more rounded teeth that were stub like. There were also small amounts of silica, presumed to be SiO2 in the teeth, but is not thought to contribute a major role to the structure of their teeth. [4]
This species of low-shore chitons is native to south-western Australia, including Queensland, New South Wales, Victoria and Tasmania.
Plaxiphora albida and Onithochiton quercinus are endemic to Southeast Australia, where they are the most abundant chitons. Both chitons grow to about 80 mm in length and are usually found around the surface of rocky shores that are exposed. The specific community is a low-shore algal type which is most abundant with the species Pyura stolonifera. [5] The sex ratio of the chiton is consistently 1:1 for males and females.
The growth of Plaxiphora albida is estimated to be around ~1 mm per season depending on the age of the chiton. This leads to the estimate of chiton growth being around ~5 mm every year [5]
Recruits of Plaxiphora albida range from 1-2 inches in width. Peak population of recruitment for the chiton is late autumn (May). Recruits have been observed to be. in multiple sites within the community. Reproductive maturity for Plaxiphora albida is roughly 2 years after birth. 50% maximum body size for the chiton is reached after only 3 to 4 years. P. albida is estimated to have a lifespan of around 6 years. While the major cause of mortality is unknown, the best conclusion would be a mixture of predation of other organisms such as starfish and seabirds, desiccation, and tidal action [5]
The gonodosomatic index of Plaxiphora albida showed fluctuations throughout the year. Smaller gonads are characteristic of immature gametes and a lower gonadosomastic index. Contrarily, larger gonads show more mature gametes and exhibit a bigger gonadosomatic index. Gonads in Plaxiphora albida are around 6–7mm. This number rises to 9–10mm when there are mature eggs and sperm present. For the Plaxiphora albida, January was the month which showed the most mature gametes and an increased size of the gonads. The gonads showed a dip in the index size during late summer and early autumn. By April, the gonads of the chiton are reduced immensely in size, staying this size for the remainder of the year. [5]
As rocky intertidal organisms, Chitons directly face threats caused by ecological shifts: temperature, tidal action, and pH. The organism's resistance to the physiological changes due to the negative impacts is largely determined by its valves. The valves determine the integrity of the shells, of which when at their threshold, could fracture and compromise the defense structure of the organism. While the fractures on the valves can be caused by a multitude of factors, there is a positive correlation between the thickness of the valves and force required to fracture. [6]
Although Chitons face variety of threats from the marine ecosystem, their ability to be abundant for the last 500 million years, suggest that their resistance to ecological pressure is robust. Scientists have accredited the agile movements of Chitons up and down the rocky niche to have partaken in their longing survival. [7]
The radula is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus. The radula is unique to the mollusks, and is found in every class of mollusk except the bivalves, which instead use cilia, waving filaments that bring minute organisms to the mouth.
Chitons are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized.
Limpets are a group of aquatic snails that exhibit a conical shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" descended independently from different ancestral gastropods. This general category of conical shell is known as "patelliform" (dish-shaped). All members of the large and ancient marine clade Patellogastropoda are limpets. Within that clade, the members of the Patellidae family in particular are often referred to as "true limpets".
The Solenogastres, common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofoveata (Chaetodermomorpha).
Odontogriphus is a genus of soft-bodied animals known from middle Cambrian Lagerstätte. Reaching as much as 12.5 centimetres (4.9 in) in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.
Chiton glaucus, common name the green chiton or the blue green chiton, is a species of chiton, a marine polyplacophoran mollusk in the family Chitonidae, the typical chitons. It is the most common chiton species in New Zealand. Chiton glaucus is part of a very primitive group of mollusc with evidence of being present in up to 80 million years of the fossil record.
Plaxiphora is a genus of chitons in the family Mopaliidae. It is distributed in the Atlantic, Indian, and Pacific Oceans, primarily in the south-temperate and subantarctic regions.
Onithochiton is a genus of chitons in the subfamily Toniciinae of the family Chitonidae, which is distributed from Australia and New Zealand to South Africa.
Acanthopleura granulata, common name the West Indian fuzzy chiton, is a medium-sized tropical species of chiton. This type of chiton's activity does not depend on spring-neap oscillations leading to lower locomotion loss. Its morphology is different from usual chitons as it has a fifth valve, which is split into halves.
Mopalia ciliata is a chiton in the genus Mopalia, commonly known as the hairy chiton. It is a medium-sized marine mollusc up to 5.0 cm (2.0 in) in length. It is oval shaped with 8 separate, moderately elevated, overlapping ridged valves on its dorsal surface. Hairy chitons can be found along the coast of North America.
The hyaline shield is a part of the radula in many kinds of molluscs. It serves as an attachment point for the muscles that retract the radula, and is thus located on the upper surface of the radula, arching backwards into the mouth. This retraction fires any food particles backwards into the mouth.
Tellina tenuis, the thin tellin, is a species of marine bivalve mollusc in the family Tellinidae. It is found off the coasts of northwest Europe and in the Mediterranean Sea, where it lives buried in sandy sediments.
Plaxiphora tricolor is a species of chiton in the family Mopaliidae.
Denticles, also called serrations, are small bumps on a tooth that serve to give the tooth a serrated edge. In paleontology, denticle characteristics such as size and density are used to describe and classify fossilized teeth, especially those of dinosaurs. Denticles are also present on the teeth of varanoid lizards, sharks, and mammals. The term is also used to describe the analogous radular teeth of mollusks.
Acanthochitona garnoti, the spiny chiton, is a medium-sized polyplacophoran mollusc in the family Acanthochitonidae, found on the coast of southern Africa.
Onithochiton literatus, the black chiton, is a medium to large-sized polyplacophoran mollusc in the family Chitonidae, found on the east coast of Africa.
Acanthopleura echinata is a Southeast Pacific species of edible chiton, a marine polyplacophoran mollusc in the family Chitonidae, the typical chitons.
Enoplochiton niger is a Southeast Pacific species of chiton, a marine polyplacophoran mollusc in the family Chitonidae, the typical chitons. It is the only species in the genus Enoplochiton.
Lasaea rubra is a species of small marine bivalve mollusc in the family Lasaeidae. It is found on the eastern side of the Atlantic Ocean. This species was first described in 1803 by the English naturalist George Montagu who gave it the name Cardium rubrum. It was later transferred to the genus Lasaea, making it Lasaea rubra.