The Derasa clam, also known as the Southern giant clam or the smooth giant clam, is one of the largest species of mollusks that live in the world’s seas and oceans and also among the longest-lived marine creatures, often living to over 200 years. Native to the shallow waters of the reefs that surround Indonesia, Australia, Papua New Guinea, Philippines, Solomon Island, Fiji and Cocos Island, these large and colorful clams are often seen lying on the sandy substrate of the open seabed or in lagoons and they can be noticed floating around freely as well.
Spotting a Derasa Clam – Physical Features of the Smooth Giant
Derasa clams grow to the length of around 60 cm, which ranks them among the largest clam species. Their shell lacks ribbing (hence the name smooth clam), but it comes in six or seven folds – a feature that distinguishes these clams from other giant clam species. The mantle is colorful, with wave-like, black, white, bright green, orange, yellow and blue stripes. Inside the hinged shell is the large and soft body of the clam, a body with no head, but with a thick and muscular foot that protrudes through the hinges of the shell and is used by the animal to attach itself to the coral reef or to the substrate.
Derasa Clams – The Circle of Life
All clams in the species are born male, but they become hermaphrodites over time. They reach sexual maturity when they reach the length of 30 cm, that is, between the age of 3-5. They proliferate by means of broadcast spawning, but each individual releases only one type of reproductive fluid at a time, either eggs or sperm, in order to prevent self-fertilization. Their mating season is usually in spring.
How Does the Derasa Clam Eat?
These giant clams satisfy their hunger through filter feeding as well as by using the nutrients produced for them by the microscopic algae that live in a symbiotic relationship with the clams. When filter feeding, the creaturel uses another muscular organ called the intake siphon that also protrudes from the shell to extract the phytoplankton and other microscopic organisms and food particles from the water column. The algae hosted by the clam engage in photosynthesis and they feed their host with the byproducts of the process, such as carboydrates and other nutrients. This combined method is very efficient – the growth rate of the Derasa clam exceeds 3 inches per year.
The boring clam, crocea clam, crocus clam, or better known to scientists and marine biologists as the Tridacna crocea, is a small creature with thick valves that usually features dim, gray and white colors, sometimes also containing a hint of yellow, orange or red. This species is a bivalve that belongs to the Tridacninae subfamily associated with the family Cardiidae. This family has a limited number of genera, and the boring clam is in fact distinguishable as the smallest species in its entire subfamily. The clam is native to the Indo-Pacific, and has a wide range, but is also quite picky about the habitats it elects for itself.
The Crocea Clam – General Description and Physical Features Characteristic to the Species
While the genus that the boring clam belongs to contains mainly larger clams, the crocus clam itself has a shell size of only about 15 cm – that being considered the maximum size it can grow to. Its thick valves are joined together by a shorter but tough hinge. The shell is typically elongated, and the clam appears inflated, its upper valve in particular consisting of 6-10 folds that interlock to give the clam more consistency and ensure that it can lock more tightly.
How Does the Crocea Behave in Its Environment?
Crocea clam populations are similar in their behavior to most Tridacna species. The animal normally fastens itself securely to the seabed. This is obtained through the use of slits present on the lower valve, which ensure byssal threads can emerge to secure the clam to the bottom. The boring clam also has the habit of burrowing itself into the substrate. This action is the main reason why the exterior valves are smooth and shiny, as the substrate tends to polish them. The clam may also appear to be uneven when burrowing into harsh or uneven substrate and running into harder areas that are more difficult to dig through.
Where Can We Normally Find the Crocus Clam?
Commonly found in the Indo-Pacific, the boring clam prefers habitats that are rich in massive corals. This is why its preferred living space is usually located in tropical regions where the temperature is not only predominantly high all year round, but also stable. The clam’s range extends from Malaysia and Vietnam westward, to Palau, the Philippines, Vanuatu and the Solomon Islands.
The marine bivalve mollusk known as the electric flame scallop has earned its name due to its brilliant and entrancing light show that it produces on its mantle lip. Scientifically known as Ctenoides ales, it is a relatively small clam. Its additional nicknames include “electric clam,” “disco clam” and “disco scallop. Aside from being the only member of the class Bivalvia to display these types of light shows, together with the common flame scallop, the species is also known for its beautiful, bright red and orange colors and its elongated, flame-like, white tentacles.
C. Ales and Its “Disco” Light Show – A Unique Trait of the Electric Flame Scallop
The electric clam’s most unique and fascinating feature is its light display, which is actually not an example of bioluminescence. Instead, light that looks similar to the flashes of an electric light show appear as a result of a type of highly reflective tissue made up of silica nano-spheres which are highly reflective. The spheres create an uneven mirror which reflects and focuses the light from the clam’s surroundings to generate the unique and beautiful light show that this species is known for producing.
The Most Important Behavioral Traits and Distribution Facts of the Disco Scallop
The electric flame scallop does not require sunlight as much as other clams and mollusks, and so divers will usually find it difficult to spot these species, since they have a knack for hiding in crevices and difficult to reach places. The clams have their own nests which they prefer to populate on most occasions, and they normally spend a great deal of time looking for phytoplankton and other small organisms to feed on. The electric clam is widespread in most tropical regions, but it is particularly found in the Indian Ocean, around the coastlines of Indonesia, Malaysia, as well as in the eastern Pacific, the Philippines and the Palau Islands.
The Disco Clam and Its Great Appetite
One of the things that sets the electric flame scallop apart from other clams is its unquenchable appetite. Unlike other species of clams, it lacks the photosynthetic zooxanthellae that would otherwise provide it with additional energy from sunlight. Instead, it relies entirely on feeding on plankton and other tiny microfauna and food particles that it can catch through water currents. As a result, the electric flame scallop tends to consume a larger quantity of these organisms than many of its counterparts, usually staying close to the coral reef ecosystem for this purpose.