Digestive system consists of an alimentary canal and digestive glands. Alimentary Canal: The alimentary canal is a straight tube from mouth to anus. It is lined by. The lancelets, also known as amphioxi (singular, amphioxus), consist of about 32 species of fish-like marine. The common lancelet, Branchiostoma lanceolatum, has been recorded from the . The digestive system of Branchiostoma consists of an alimentary canal and.

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Digestive Systems of Branchiostoma and Ascidia | Zoology

The circulatory system does resemble that of primitive fish in its general layout, but is much simpler, and does not include a heart. These results illustrate phagocytic intercellular digestion in Branchiostomaexplain why Branchiostoma digestive tract epithelial cells express typical immune genes and suggest that the main physiological function of the Branchiostoma diverticulum is different from that of the vertebrate liver.

With the advent of molecular genetics lancelets are once again regarded as a model of vertebrate ancestors, and are in process of being revived as a amphioxuz organism. Both primary and secondary gill-bars are covered on their external or outer surface by sparsely ciliated ectodermal or atrial epithelium, but on their inner, anterior and posterior surfaces by endodermal pharyngeal epithelium which is heavily ciliated.

The gill-clefts are metameric, vertical apertures when first formed in the larva, but each gets divided into two.

The oral cirri remain converged inward to form a sieve over the mouth at the time of feeding. Open in a separate window. On the other hand, internal food collection appeared in some others.


The mucus-entangled food particles move upwards and are then pushed back into the oesophagus by the ciliary action of the dorsal lamina. The cilia in the endostyle and gill-bars beat to produce an upward current to push the mucus-entangled food particles towards the epipharyngeal groove.

On the other hand, because Branchiostoma cannot embody every feature of the ancestral chordate, and its diverticulum is possibly a specialized structure reflecting only Brachiostoma’s own evolutionary history or lifestyle, studies of echinoderms, hemichordates, urochordates and ammocoetes larval lampreys are indispensable to investigating this question [ 58 ].

Lancelet – Wikipedia

In other projects Wikimedia Commons. The anterior part of the nerve tube is slightly dilated to form the brain and the posterior part remains as the spinal cord. There is no liver.

The myotomes are separated from one another by dense connective tissue septa, called myocommas. Having passed through the gill slits, the water enters an atrium surrounding the pharynx, then exits the body via the atriopore.

It is commonly anphioxus in the sandy shores.

Phagocytic intracellular digestion in amphioxus (Branchiostoma)

The Hesse organs also known as dorsal ocelli consist of a photoreceptor cell surrounded by a band of microvill and bearing melanopsin, but half enveloped by a cup-shaped pigment cell. Such anterior prolongation of the notochord beyond the brain is associated with its burrowing habit. In larval stage its cavity remains in direct communication with the ventricle through the neuropore.

There are no blood cells, and no haemoglobin. Received Mar 11; Accepted May Di, diverticulum; Ir, ileo-colon ring; Lu, lumen; As, apical side; P, phagosome. Both adults and larvae exhibit a “cough” reflex to clear the mouth or throat of debris or items too large to swallow.


Outer of these, the mid-dorsal groove is the largest and ends in a pit or depression in the roof of buccal cavity. The food cord from the hepatic diverticulum is pushed backwards by the cilia present in its cavity.

In non-chordates the muscle layer is of almost uniform thickness surrounding the coelom. The annotated tissue-specific genes were verified by conserved homologous sequence using C lustal W and neighbour-joining trees using M ega 6 with bootstraps. Branchiostoma is a microphagus animal which obtains the food by filtering the stream of water that enters the pharyngeal cavity. The total RNA isolation was processed in the same way as the construction of Full. They are the modern representatives of the subphylum Cephalochordataformerly thought to be the sister group of the craniates.

It was described by Peter Simon Pallas in as molluscan slugs in the genus Limax. The gastric secretion has a strong carbohydrate-splitting enzyme and weaker lipolytic and proteolytic enzymes.

Kurt YG, et al. Genetic programming of liver and pancreas progenitors: Gene expression profiles suggest that diverticulum epithelial cells have functional features of both digestive cells and phagocytes. B— The animal swims spirally about its axis. Philosophical Transactions of the Royal Society B: The epithelial cells of the diverticulum and hindgut can phagocytize food particles directly, and the phagocytic capability of diverticulum cells is greater than that of the hindgut epithelial cells.

Slides for the animal portion of Biology – Clam and Crayfish dissection.