Molluscs

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Molluscs

Reproduction

Some molluscs are unisexual and hermaphrodite.

Hermaphrodite: Are species in which all individuals possess both male and female sex organs. Like gastropods.

Unisexual: Are those in which individuals have separate sexes. This means that they are either male and female. Like cephalopods and bivalves.

Gamete formation: Are formed in the reproductive system in organs called sex organs or gonads.

Female gonads are called ovaries. They produce feamle gametes or ova, which are spherical, immobile and larger than spermatozoa, because they contain stores of nutrients.

Male gonads are called testes, that produce male gametes and spermatozoa, which are small, elongated structures with a flagellum that enables them to move.

Molluscs have sexual reproduction: Is the most common form of reproduction in animals. This type of reproduction involves two individuals of different sexes. A male and a female.

Types of molluscs

Cephalopods: Most of them do not have shell, or just have a small internal shell, called a gladius, which looks like a sheet of plastic. In the head they have two well-developed eyes and, instead of a foot, they have a set of tentacles around the mouth. They are carnivores and active hunters. Squids, octopuses and cuttlefish.

Bivalves: Their shell is formed by two valves, and they use muscles to close these together. Their foot, in the shape of a wedge, is used to move and dig. Their head is not well-defined. They feed by filtering water and taking tiny living things. Mussels, clams, cockles, oysters and razor shells.

Gastropods: Most of them have a sell coiled in a spiral shape They have large muscular foot to move around. They have a well-developed head. In their mouth they have a scraper organ, called radula, to feed themselves. Snails, slugs and limpets.

Nutrition

Digestive System: Molluscs have digestive system. 1-The molecules in nutrients are broken down through chemical processes. 2-The nutrients are absorbed and transported to the cell. 3-The unusable part of the food is eliminated from the body.

Digestive track: Are long tubes with one opening for taking in food and another opening for expelling undigested food. They have specialised parts for carrying out the different processes involved in digestion.

Digestion: Is a process carried out by animals that consists of transforming food to obtain the nutrients it contains.

Feeding: Consists of taking food that is material from other living organisms that contains nutrients. Molluscs obtain food by the tentacles.