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Pinctada albina
(Lamarck, 1819)

Shark Bay Shell

Nicholai Cushing (2014)

 

 

Fact Sheet

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Summary


Physical Description


Ecology


Life History & Behaviour


Anatomy & Physiology


Evolution & Systematics


Biogeographic Distribution


Conservation & Threats


References & Links

Anatomy & Physiology

The key anatomical and physiological elements of Pinctada albina are outlined below for five main systems. Certain systems could be considered more closely associated with others such as the close association between respiratory and digestive systems or respiratory and circulatory. A description of the key features of the respiratory, digestive, circulatory, nervous and excretory systems is given below. Emphasis is placed upon the respiratory and digestive systems as they are closely linked in Lamellibranch bivalves.

Internal anatomy of a Lamellibranch bivalve. (Adapted from Ruppert et al., 2004)



Dissection of a specimen of P. albina. The mantle lobes (A) excrete the shell and protect the visceral mass and gills (B). The heart (C) contained within the pericardial cavity near byssus (D) and the digestive system (E & F). The labial palps surround the mouth (E) and food particles pass through the mouth into the stomach surrounded by the digestive gland (F). (Labelled using diagrams from Queensland Government, 2014, Ruppert et al., 2004, Southgate & Lucas, 2008)


Respiratory system

P. albina  uses its gills (ctenidia) for both filtering food particles from the water and respiration (Southgate & Lucas, 2008). Each gill consists of four elongated lamellae, which form a 'W' shape when viewed from a transverse cross-section (Diagram below) (Ruppert et al., 2004, Southgate & Lucas, 2008). Pearl oysters have two sets of symmetrical gills that are crescent-shaped fusing with the mantle, visceral mass and adductor muscle (Southgate & Lucas, 2008) and each gill has over 8000 filaments (Ruppert et al., 2004). The axis of the gills is highly vascular and the membranes of the surrounding gill tissues are very thin to allow oxygen to diffuse from the water into the circulatory system (Southgate & Lucas, 2008).
​Gill imagery of half the gill structure. This structure is mirrored in the the other gill set on the opposite side of the visceral mass. Left side is the exhalant chamber, right side is the inhalant chamber (Adapted from Ruppert et al., 2004)

Lamellibranch gills contain two different types of cilia the frontal and lateral cilia (Ruppert et al., 2004, Southgate & Lucas 2008). Lateral cilia are responsible for creating the current of water over the gills from the inhalant chamber (located closer to the visceral mass of the animal), through and along the gills and out the exhalant chamber (located closer to the shell) (Image above) (Ruppert et al., 2004, Southgate & Lucas, 2008). The frontal cilia are responsible for the transportation of particulate caught on the mucus covered fronts of the gills (Beninger & St-Jean, 1997, Ruppert et al., 2004, Southgate & Lucas, 2008). Although the role of mucus in the feeding and respiration is disputed (Jorgensen, 1996) it is widely believed and studied to be an important component of the respiratory and digestive systems of Bivalves (Beninger & St-Jean, 1997, Ruppert et al., 2004). 



​Cilliated epithilum of the gills of a specimen of P. albina. Each darker spot is the nucleus of an individual cell and the pinkish areas indicate extracellular tissues. Images are only a fraction of the entire gill structure with the entire structure containing a much greater number of cilia and folded surfaces to increase the surface area to volume ratio of the gills and improve gas exchange. (Imagery of H&E (Haematoxylin and eosin) stained slides on an Olympus dierential interference contrast (DIC; Normarski) microscope)

Once the larger particles of have been "strained" out of the water by the gill filaments, the cilia then transport these particles to the labial palps located near the mouth (Ruppert et al., 2004, Southgate & Lucas, 2008). The labial palps are covered in mucus that plays a key role in the sorting of organic and inorganic particulate matter transported from the gills (Beninger & St-Jean, 1997, Ruppert et al., 2004). The sorting fields of the labial palps work by separating the particles by sizes (Ruppert et al., 2004). Larger particles are suspended by cilia and pass over surface perpendicular to the grooves in the palps whilst smaller particles fall down between the grooves and are excreted (Ruppert et al., 2004, Southgate & Lucas, 2008). Organic and inorganic particles are also sorted in this region by ciliary action and mucus so that the digestive system receives only a fraction of the matter passed into the labial palps from the gills (Ruppert et al., 2004). From the mouth the food passes through the oesophagus and begins the journey through the digestive system.


Digestive system

Food particles move from the mouth into the oesophagus and through into the stomach where digestion begins. The stomach is almost completely enveloped by the large digestive gland, which is permeated by a series of cilia-lined ducts called digestive tubules(Southgate & Lucas, 2008). These tubules are responsible for much of initial phagocytosis (digestion and absorption) and breakdown into smaller particles (Southgate & Lucas, 2008). The tubules are lined with cilia, which serve the purposes of moving the food through these tubules during phagocytosis and increasing the surface area for nutrient absorption (Southgate & Lucas, 2008). The stomach and digestive tubules also secrete mucus, which aids in the digestion of the particles (Southgate & Lucas, 2008, Beninger & St-Jean, 1997).


​Digestive tubules of the digestive gland in the stomach of a P. albina specimen. The darker spots indicate the nuclei of individual cells and the pinkish areas extarcellular tissues. Cilia tails can be seen in images B and C with the nuclei of these cilia forming the dark ring wall of the tubules. (Imagery of H&E (Haematoxylin and eosin) stained slides on an Olympus dierential interference contrast (DIC; Normarski) microscope)

From the stomach and the digestive gland the food particles pass into the intestine, which is divided into three main sections (Southgate & Lucas, 2008). The anterior descending and the ascending intestine function in the absorption of any remaining nutrients in the stomach contents before it is excreted (Southgate & Lucas, 2008). The final section of the intestine is the rectum, which terminates on the posterior face of the oyster (see Life History & Behaviour for diagram) in the anus (Southgate & Lucas, 2008, Queensland Government, 2014). At the anus fecal matter is ejected from the digestive system and carried out of the shell by the prevailing water current moving through the gills (Southgate & Lucas, 2008).


Circulatory system

Located in the the posterior region of the visceral mass is a pericardial cavity, which contains the heart (Southgate & Lucas, 2008). The heart of P. albina is made up of one ventricle and two auricles with the base of the auricles joining to the nephridium (part of the excretory system)(Southgate & Lucas, 2008). From the heart there are two aortas, the anterior and posterior aorta, which feed smaller vessels with oxygenated hemolymph (blood and lymph)(Southgate & Lucas, 2008). In the gills the unoxygenated hemolymph flows in one direction along the gills through a pair of afferent blood vessels in the ascending limbs of the filaments (Ruppert et al., 2004). Here oxygen from the water diffuses across thin cellular membranes and into the hemolymph and is transported to the organs by the system of blood vessels (Southgate & Lucas, 2008).


Nervous system

The nervous system in P. albina consists of three pairs of ganglia and a series of nervous tissues connecting the ganglia and other organs (Southgate & Lucas, 2008). Cerebral ganglia lie on either side of oesophagus and function to coordinate some activity within the mantle, labial palps, gut, adductor muscle and foot (Ruppert et al., 2004, Southgate & Lucas, 2008). The pedal ganglia join as one mass near the base of the foot controlling functions and movements associated with the foot and byssus (Ruppert et al., 2004, Southgate & Lucas, 2008). The final set of ganglia, the visceral ganglia, are located on the adductor muscle and control functions in the gills, heart, excretory system and mantle (Ruppert et al., 2004, Southgate & Lucas, 2008). There are numerous other sensory organs including ciliary receptor cells, chemoreceptors and small sensory tentacles associated with the mantle (Ruppert et al., 2004).


Excretory system

The excretory system is comprised of a pair of nephridia located just below the auricles of the heart and a series of small pericardial glands (Southgate & Lucas, 2008). The main part of the excretory system are the nephridia, which mimic the function of the kidneys in other animals (Ruppert et al., 2004). They have an enhanced surface area and come into contact with the hemolymph in the surrounding ciculatory vessels (Ruppert et al., 2004). The nephridium filter the blood and empty the waste products through small pores into the exhalant chambers where it is expelled with other waste from the digestive system and labial palps (Ruppert et al., 2004, Southgate & Lucas, 2008)

Classification

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Kingdom
Animalia
Phylum
Mollusca
Class
Bivalvia
Order
Ostreida
Superfamily
Pterioidea
Family
Pteriidae
Genus
Pinctada

Synonyms

Avicula anomioides (Reeve, 1857)
Avicula atropurpurea (Dunker, 1852)
Avicula concinna (Dunker, 1872)
Avicula fimbriata (Reeve, 1857)
Avicula flexuosa (Reeve, 1957)
Avicula imbricata (Reeve, 1857 [non Pinctada imbricata Röding, 1798])
Avicula irradians (Reeve, 1857)
Avicula placunoides (Reeve, 1857)
Avicula radula (Reeve, 1857)
Avicula reentsii (Dunker, 1872)
Avicula reeveana (Dunker, 1872)
Avicula scheepmakeri (Dunker, 1872)
Avicula sugillata (Reeve, 1857)
Avicula tristis (Dunker, 1872)
Meleagrina albina (Lamarck, 1819)
Pinctada atropurpurea ((Dunker, 1852))
Pinctada perrutila (Iredale, 1939)
Pteria carchariarum (Jameson, 1901)
Pteria placunoides ()

Common Names

モスソアコヤ