Let us learn about the comparison of ciliary mode between branchiostoma, ascidia and balanoglossus.
Comparison # Balanoglossus:
1. Internal food-collection, i.e., food is collected inside the body.
2. Microphages.
3. Wheel organ produces a flow of water-current which is drawn into the mouth.
4. Velum with velar tentacles control the entry of water-current into mouth.
5. The feeding current follows the following course:
Mouth → Pharynx → Pharyngeal gill-slits → Atrium → Atriopore → Exterior
6. Cilia present in gill-bar beat to drive the water- current into the atrium through the gill-slits and thus maintains a constant water-current through mouth.
7. Food-particles are entangled by the sticky secretion of the mucous cells of the endostyle lying on the floor of the pharynx.
8. The mucus-entangled food-particles are driven by the cilia of endostyle as a food-rope along the peripharyngeal ciliary grooves to the epipharyngeal groove from where food-cord passes to oesophagus.
9. The entry of the large particles are prevented by the buccal cirri around mouth.
10. Afferent and efferent nerve-fibres are held to control the ciliary-beating and regulate the water-current.
11. The receptor-organs present over the velum and atrium, taste and regulate the nature of water-current.
12. If the water-current contains any toxic substance, the atriopore becomes closed and the pharyngeal-muscle contracts and the water- current is regurgitated.
Comparison # Ascidia:
1. Internal food collection
2. Microphages.
3. No wheel organ. External water-current directly enters into the mouth.
4. Same as in Branchiostoma.
5. Same as in Branchiostoma
6. Same as in Branchiostoma.
7. Food-particles from the feeding-current are entangled by the mucus, secreted from the glandular tracts of endostyle.
8. The mucus-entangled food-particles move upward from endostyle along the peripharyngeal ciliary grooves and then reach the dorsal lamina from where food-cord is pushed back into oesophagus.
9. The tentacles at the base of the oral siphon are held to obstruct the entry of large particles.
10. Same as in Branchiostoma.
11. The receptor-papillae on the stigmata, may check the water- current.
12. Unwanted water- current is forcefully expelled by the closing of one siphon, and the subsequent contraction of the body musculature.
Comparison # Balanoglossus:
1. External food-collection, i.e., food particles are trapped outside the body.
2. Microphages.
3. Due to external food- collection, there is no need of water-current toward mouth.
4. Muscular tip of the collar over the mouth regulates the feeding- current into mouth.
5. The feeding-current follows the following course:
Mouth → Pharynx → Pharynx → Pharyngeal gill-slits → Exterior
6. Cilia of gill-bars beat to maintain a constant water-current via mouth and pharyngeal gill-slits to the exterior.
7. As food-collection is external, food-particles are entangled outside the body by the mucus, secreted by proboscis. The mucus-coated food- particles directly pass into the mouth by ciliary action.
8. The externally-collected food-particles pass directly to the oesophagus via the ventral digestive part of the pharynx. There is no endostyle and epipharyngeal groove.
9. The muscular tip of the collar can be folded over the mouth, to prevent the entry of large particles.
10. Nerve-fibres reflected in the collar epithelia, are held to control the opening of the mouth by the muscular fold of collar.
11. Sensory-cells at the edges of pre-oral ciliary organ at the base of the proboscis act as chemo-receptor organ and taste the nature of feeding-current
12. No such regulatory mechanism is known.