Pinna bicolor
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| Pinna bicolor | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia |
| Order: | Pteriida |
| Family: | Pinnidae |
| Genus: | Pinna |
| Species: | P. bicolor |
| Binomial name | |
| Pinna bicolor Gmelin, 1791 | |
| Synonyms[1] | |
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Pinna bicolor, also known as bicolor pen shell, razorfish, razor clam, or pen shell, is a species of large saltwater clam in the family Pinnidae. It is commonly found in shallow waters up to 50 m (160 ft) deep. It can be found embedded in firm muddy intertidal sediments, seagrass beds, and reef flats along continental and island shores.
P. bicolor have thin, elongated triangular shells that narrow to a point and range in color from light yellow-brown to dark brown.[2] They are often overlooked as most of the shell is often buried with only about 2–3 cm of it sticking out of the ground. Glands near the buried end of the shell secrete byssus threads which allow the P. bicolor to attach itself to buried rocks and stones to anchor itself to the ground. When embedded in mud, the shell projects a fan shape as it is known to bury itself with the pointed end down.[3] This earns it the moniker of "razor clam" in Australia due the danger these strong shells pose to waders and their abundance at low tide.[4] They are generally known as "razorfish" in South Australia.[5][6]
With a bilaterally symmetric body, the shells of a P. bicolor have an average length of 40 cm (16 in) with a maximum length of 50 cm (20 in).[7][8] Its major organs are small and located at the pointed end that is buried deep in the ground where it is difficult for most predators to reach.
Distribution
Pinna bicolor is native to Kwazulu-Natal, South Africa, and is commonly found in shallow waters up to 50 m (160 ft) deep.[7][4] It also inhabits tropical zones from 35oN–37oS and 29oE–154oW; occurs from the south and eastern African coasts, Madagascar, the Red Sea, the Persian Gulf and India, as well as spanning from Japan to southern Australia and the whole East Indies. It is generally absent from mid-oceanic islands such as those in the central Indian Ocean.[8] It occurs most commonly at depths of 20 m (66 ft) at low population densities of 2–5 per square meter, likely because they occur in environments with low nutrient concentrations.[9]
Their habitat temperatures generally range between 27–30 °C and salinity ranges from 28–33 parts per thousand.[2] They sit partially embedded in firm muddy intertidal sediments, in seagrass beds, and atop reef flats along continental and island shores at depths of up to 50 m (160 ft).[4] Since this species is bottom-living, changes in environmental conditions have not impacted them much.[10]