The Mercenaria mercenaria is a member of the Mollusca phylum since it shares characteristics with other members of this group. One shared characteristic is members of this phylum have bilateral symmetry and these organisms are triploblastic (Phylum Mollusca, n.d.). In addition, these members of the Mollusca phylum have bodies made up of three body regions, a head-foot, a visceral mass, and a mantle (Phylum Mollusca, n.d.).
Why is this organism a member of this class?
The Hard clam is a member of Bivalvia class since it has a shell made up of two parts, which was created by the mantle that had released calcium carbonate (Yeh, n.d.). In addition, the shell continues to grow as the organism inside it grows (Yeh, n.d.). Also, most members of the Bivalvia class find their necessary nutrients through filter feeding (Yeh, n.d.). A final shared characteristic amongst the members in this class is as larvae these organisms are able to swim freely in a body of water (Yeh, n.d.).
1. What type of symmetry?
The Northern quahog has bilateral symmetry (Burdette, 2001).
2. How many germ layers?
This organism is triploblastic, meaning it has three germ layers: the mesoderm, endoderm, and the ectoderm (Chen, 2009).
3. Types and names of body cavity(ies) if any.
The Hard clam is a coelomate, and this organism has a pericardial body cavity (Chen, 2009).
4. Type of segmentation and number and name of segments. This may not be applicable to all animals.
The Northern quahog does not have segmentation in its body structure (Chen, 2009).
5. Type of support/locomotion system.
Hard clams use their foot as their primary source of locomotion, in addition to the movement of waters currents (Cloe, 2018). The foot is used to help the clam move in a side to side motion, and it allows them to burrow themselves into the sand (Cloe, 2018). Hard clams have two different types of muscles; the valve muscles, and the two foot muscles (Cloe, 2018). The valve or adductor muscles allow the organism to control the opening and the closing of its shell, and the two foot muscles allow the clam to move side to side (Cloe, 2018). This organism is protected by its two part shell. The shell is created by a tissue called the mantle that releases a substance called calcium carbonate, which makes up the shell (Anatomy of Animals, n.d.).
6. Describe the respiratory and circulatory system.
The Hard clam has an open circulatory system (Anatomy of Animals, n.d.). The circulatory system pumps out blue blood caused by the hemocyanin pigment found in the the blood, and this blood is pumped by the organism’s heart found in the pericardial cavity(Anatomy of Animals, n.d.). The blood from the heart is pumped into vessels connected to different organs, and inside the organs are sinuses (Anatomy of Animals, n.d.). The respiratory system of the Hard clam is made up of gills located above the foot of the organism, and once the water is taken up by the gills, oxygen is taken into the bloodstream (BIO 5 GENERAL BIOLOGY, n.d.). Carbon dioxide produced by the Hard clam is released back into the water (BIO 5 GENERAL BIOLOGY, n.d.).
7. Describe the digestive and excretory system.
The Northern quahog retrieves food by taking in small particles when it takes in water, and then the organism release excess water, keeping the particles left for nutrients (Digestive System, n.d.). This makes the Northern quahog a filter feeder (Digestive System, n.d.). The water along with the particles is taken in through the mantle cavity that has an opening called the incurrent siphon (Anatomy of Animals, n.d.). As water passes through the gills of the clam, the particles attach to a mucus on the gills, and small cilia push the particles from the mucus into the mouth (Anatomy of Animals, n.d.). The particles then travels into the stomach, which is surrounded by digestive glands that releases enzymes into the stomach to break up the particles (Anatomy of Animals, n.d.). The stomach has tubes with their sides surrounded by cilia, and that is where the food particles enter the stomach (Anatomy of Animals, n.d.). In addition to the digestive glands, there is the style sac that releases an enzyme called amylase, which will break up starches in the stomach (Anatomy of Animals, n.d.). The broken up nutrients will be absorbed into the bloodstream by the glandular cells that line the ciliated tubes (Anatomy of Animals, n.d.). The wastes from the digestive gland are returned to the stomach, and then the wastes will end up in the intestines (Anatomy of Animals, n.d.). Wastes in the intestines will leave the organism through its anus, and the wastes are carried out as water is expelled (BIO 5 GENERAL BIOLOGY, n.d.). Waste made by the cells, ammonia, is removed by two kidneys that remove the cell waste from the pericardial cavity (BIO 5 GENERAL BIOLOGY, n.d.).
8. Describe the type of nervous system.
This organism has a nervous system made up of three pairs of ganglia, which are connected together by nerve cords (BIO 5 GENERAL BIOLOGY, n.d.). The nerve cords are then attached to sensory cells, which differentiate to sense different things, such as touch and light (BIO 5 GENERAL BIOLOGY, n.d.) . These sensory cells will also be located in different areas of the body (BIO 5 GENERAL BIOLOGY, n.d.).
9. Describe reproduction and development.
The Hard clam begins its mating season when the water starts beginning warmer, which is during the period between end of May and early June (M., 2016). The average temperature for mating season to begin needs to be around 68℉ (M., 2016). In order for fertilization to occur, young clams release sperm into the ocean, while older clams release eggs into the ocean (M, 2016). Once the sperm and egg meet in the ocean, fertilization occurs, and cells divide until a morula forms (M, 2016). Next, the morula develops into a trochophore when cilia develops on the morula, and the organism is able to move about (M, 2016). Then as the organism develops a shell and a foot, it is in its veliger stage, where begins to appear like a clam with a shell and a fully grown foot (M, 2016). As the organism is in its pediveliger stage, the Hard clam gains enough weight to sink to the bottom of the ocean floor, which takes between 8 to 14 days (M, 2016). The lifespan of a Hard clam is approximately 30 years (M, 2016).
10. What is this organism’s habitat?
This organism lives in areas where mud and sand flats are present, and the range of salinity that a Hard clam can keep its larvae in is between 20 to 35 parts per thousand (Burdette, 2001). In addition, this clam species has been native to do Atlantic Ocean, and its species has been able to live in the Pacific Ocean, as well (Burdette, 2001). The geographical range where a Hard clam can be found is from the Gulf of St. Lawrence all the way to the Gulf of Mexico (Burdette, 2001).
11. What type of special adaptations does it have for this habitat?
Special adaptations that allow for the Northern quahog clam to survive in its habitat are its foot, its filter feeding abilities, and its shell. The foot allows for the organism to burrow itself into mud and sand flats, which gives the organism shelter, and a source of hiding away from predators. Next, the Northern quahog clam being a filter feeder allows it to survive in its habitat since the clam is not a fast moving organism. Therefore, the clam does not need to chase or to capture its food since the gills take in nutrients from the water for the clam to sustain itself. Finally, the shell is a significant adaptation for the clam to be able to survive in its habitat. The reason is the shell gives the clam protection to its soft body from predators. The shell is difficult to open when the clam contracts its muscles to keep the predator from eating them.