Biology and Physiology ofPomacea Canaliculata Presented byCHANG PEI XIAN D 20101037455
Pomacea Canaliculata are amphibious, both in physiology and behaviour.Their mantle cavity contains both a ctenidium (gill) and a portion modified as a pulmonary sacs or “lung”.have gills, but can survive for extended periods exposed to air.Have a trap door (operculum) to protect their soft tissues when withdrawn into the shell.
Coloration of the shell is brown or olive brown, often with darker bands and blotches.Show sexual dimorphism in shell size, shape, thickness and weight.They have been reported to change sex. Sex change is from male to female (during a period of without aestivation)Shows variation related mainly to different thermal regimes.
Pomecea Canaliculata have long life cycles (>3 years but depends on the thermal regimes). Iteropareous in regions with hydric and thermal seasonality.When reared at a constant temperature of 25 C, P. Canaliculata’s life span reduced to less than 14 months.Growth is not continuous but seasonal. temperature appears to be the main factor affecting both the maturation process and their activity.
Sexually mature when it is 25 mm.Able to tolerate low levels of salinity.Experimental traits have shown that growth rates, longevity and age at maturity are highly dependent on temperature, crowding and food availability.Mobility and feeding are highly reduced when water depth is lower than shell diameter, drought survival is probably related to size.
Digestive System The digestive system of Pomacea Canaliculata is adapted to feed on aquatic plants. It can be divided in five regions: The intake region (mouth and buccal cavity with radula and jaws) The pre-digestion region (esophagus with salivary glands and lateral pouches) Digestion region (3 chambered stomach with associated digestive glands) Uptake region (intestine) The excretion region (rectum and anus)
Mouth vertical slit opening, located between the labial tentacles and leading to the buccal cavity. Food is located with the labial tentacles and when needed gathered from the water surface with foot. The radula of an eating snail in The radula knobs and jaws of an eating Detail(Pomacea Canaliculata) Snail(Pomacea Canaliculata)
Buccal cavity A muscular cavity with a set of calcareous jaws, 2 radula knobs and the radula (rasp tongue), is situated behind the mouth opening. When the radula is bend and stretched, this spreading the teeth on it, which provides the grasp function. After the food has pulled into the buccal cavity, calcareous jaws cut off the piece of food.
Stomach A pink “U” shaped structure on the left side of the body whorl. Consists of three compartments: ◦ the muscular gizzard (posterior chamber) ◦ the vestibule (anterior chamber) ◦ the style sac.
Intestine Lies close to the style sac and coils around the posterior kidney. Can be divided in several parts: the caecum, the first, second and third part of the intestine and anal papilia. The digestion of the food is partially done by adding enzymes by the snail itself and partly by the micro-organisms in here. The uptake of the food compound is carry out through the walls of the intestine and transported to the blood stream.
Sensory SystemPomacea Canaliculata are highly dependent on their smell sense.Able to locate food and recognize other snails of their own species with their smell sense.Vision is weak; functions merely as a light direction detector.The tactile sense is well developed.The hearing capabilities are worthless, even more, they are completely deaf.
Body: the whole body surface contains chemo- and mechanoreceptors.Eyes: The eye on the eye stalk of a Pomacea Canaliculata Snail. The eyes of the Pomacea Canaliculata are located at the base of the tentacles, on top of the eyestalks.
The structure of the eye does not provide detail vision, they rather function as directional light sensors.Colour vision is absent; Pomacea Canaliculata is colour-blind.Two mechanisms are used in their eyes to increase sensitivity to light: the eyes are relatively large with a large lens and the light sensitive cells (rhabdoms) are grouped and connected with the same neuron.
Osphridia: A chemosensory structure that is located in the mantle cavity, in front on the lung. Gives the snail capability to smell chemical substances in the water.
Statocysts: Function as balancing organs, used by the snail to detect its position with regard to the ground. Located inside the snail’s body closed to the pedal ganglia.Tentacles: Important sensory organs. Pomacea Canaliculata highly rely on the smell capacity and the sensitivity of their tentacles to navigate in their environment.
Nervous SystemCentral nervous system consists of a several ganglia connected with each other by a commisura.The perikaya (cell bodies of the nerve cells) are concentrated in these ganglia.Some parts of the nervous system are symmetric while others are not.There isn’t a central brain in snails like mammals have.
Respiratory SystemThe respiratory system of the Pomacea Canaliculata : a combination of a gill and a lung.The arise of the lung in Pomacea Canaliculata can be explained by the following conditions: Low oxygen level in the tropical pools. Use during periods of drought. Increases the action radius of the snail.
Retained their gill during the course of evolution, this is contrary to the Pulmonata snails, which only have a lung and no gills.Having a gill provide a big advantage - can avoid attacks by the land predators.Have a siphon (breathing tube) so that they can breath air while staying hidden below the surface.
Description of the Respiratory Organs Ctenidium: Gill of the Pomacea Canaliculata. Consists of a row of gill filaments that hang into the mantle cavity. Osphradius: Smell organ of Pomacea Canaliculata.
Lung:An air filled sac in the left mantle cavity.Walls of the pulmonary sac are well supplied with blood to exchange oxygen and carbon dioxide.Siphon:An organ consisting of a fold of the mantle cavity.Enable the snail to breath air while staying submerged.
Heart and CirculationThere is only one auricle that receives oxygen rich blood from the lung and gills, deoxygenated blood from kidney.No separated blood circulation for oxygen rich and deoxygenated blood.Blood has two functions: As hydroskeleton(structural support). Transport of O2, CO2, hormones, nutrition and waste products.Open circulation.
H = Head - cephalic hemocoel Au = AuricleF = Foot hemocoel V = VentricleE = Oesophagus Aa = Aorta anteriorVm = Visceral mass (hemocoel) Ap = Aorta posterioraK = anterior (front) Kidney Vs = Visceral sinuspK = posterior (back) Kidney Fs = Foot sinusA = Ampulla
The transport of the blood to and from the organs occur through artery.They don’t have capillary veins and arterioles.
Reproductive SystemHas separated sexes (dioecious).The differences between the sexes are not visible at shell colour or pattern.
Male reproductive system The male reproductive tract consist of the testis and vas deferens, the seminal vesicle and the prostate gland, the penial sac, the penis and the penis sheath. During mating activities, this penial papilla bends towards the sperm groove in which the sperm is conducted. The sperm is conveyed in the penial duct at the base of the penis. On erection the penis comes out of the penial sac and is grasped around on the lower part by a muscular penial sheath from the mantle.
Female Reproductive SystemThe egg cells are stored in the ovaries.To produce an egg, the egg cell is brought to the receptaculum seminis. In this place, the fertilization of the egg cells takes place.The spermatozoa (sperm cells) of the male can survive for more than a month in the female, and several egg clutches can be fertilized with a single copulation.The eggs were deposited above the water line.