haetognaths are transparent or translucent -animals covered by a cuticle. The body is divided into a distinct head, trunk, and tail. There are between four and fourteen , spines on each side of their head, flanking a hollow vestibule containing the mouth. The spines are used in hunting, and covered with a arising from the neck region when the animal is swimming. chaetognaths
The trunk one or two pairs of lateral fins incorporating structures superficially similar to the fin rays of fish, with which they are not homologous, however: unlike those of vertebrates, these are composed of a thickened basement membrane extending from the epidermis. An additional caudal fin covers the post-anal tail. Two chaetognath species, Caecosagitta macrocephala and Eukrohnia fowleri, have bioluminescent organs on their fins.
Chaetognaths swim in using a dorso-ventral undulating body motion, where their tail fin assists with propulsion and the body fins with stabilization andSome species are known to use the neurotoxin tetrodotoxin to subdue prey.
The lacks a peritoneum, and therefore resembles the pseudocoel of animals such as nematodes, but is divided into one compartment on each side of the trunk, and additional compartments inside the head and tail. Although they have a mouth with one or two rows of tiny teeth, compound eyes, and a nervous system, they have no respiratory or circulatory systems.
The mouth opens into a muscular pharynx, which contains glands to lubricate the passage of food. From here, a straight intestine runs the length of the trunk to an anus just in front of the tail. The intestine is the primary site of digestion and includes a pair of diverticula near the anterior end.
The nervous system is reasonably simple, consisting of a ganglionated nerve ring surrounding the pharynx. The dorsal ganglion is the largest, but nerves extend from all the ganglia along the length of the body. Chaetognaths have two compound eyes, each consisting of a number of pigment-cup ocelli fused together. In addition, there are a number of sensory bristles arranged in rows along the side of the body, where they probably perform a function similar to that of the lateral line in fish. An additional, curved, band of sensory bristles lies over the head and neck.
Materials are moved about the body cavity by cilia. Waste materials are simply excreted through the skin and anus.
The arrow worm rhabdomeres are derived from microtubules 20 nm long and 50 nm wide, which in turn form conical bodies that contain granules and thread structures. The cone body is derived from a cilium.[9]
haetognaths โปร่งใสหรือโปร่งแสงสัตว์ปกคลุมด้วยคิวติเคิล . ร่างกายแบ่งออกเป็นจำนวนหัว ลำตัว และหาง มีระหว่างสี่และ 14 , หนามบนแต่ละด้านของหัวของพวกเขา , flanking กลวงด้นประกอบด้วยปาก หนามจะใช้ในการล่าสัตว์และปกคลุมด้วยที่เกิดจากบริเวณลำคอเมื่อเป็นสัตว์ที่ว่ายน้ำ chaetognaths
The trunk one or two pairs of lateral fins incorporating structures superficially similar to the fin rays of fish, with which they are not homologous, however: unlike those of vertebrates, these are composed of a thickened basement membrane extending from the epidermis. An additional caudal fin covers the post-anal tail. Two chaetognath species, Caecosagitta macrocephala and Eukrohnia fowleri, have bioluminescent organs on their fins.
Chaetognaths swim in using a dorso-ventral undulating body motion, where their tail fin assists with propulsion and the body fins with stabilization andSome species are known to use the neurotoxin tetrodotoxin to subdue prey.
The lacks a peritoneum, and therefore resembles the pseudocoel of animals such as nematodes,แต่จะแบ่งออกเป็นหนึ่งช่องในแต่ละด้านของลำต้นและช่องเพิ่มเติมภายในหัวและหาง ถึงแม้ว่าพวกเขามีปากด้วยหนึ่งหรือสองแถวของฟันเล็ก ๆบริเวณดวงตาและระบบประสาท พวกเขาไม่มีระบบทางเดินหายใจ หรือเกิด
ปากเปิดเข้าไปในคอหอยของกล้ามเนื้อซึ่งมีต่อมหล่อลื่นทางเดินของอาหาร จากที่นี่ a straight intestine runs the length of the trunk to an anus just in front of the tail. The intestine is the primary site of digestion and includes a pair of diverticula near the anterior end.
The nervous system is reasonably simple, consisting of a ganglionated nerve ring surrounding the pharynx. The dorsal ganglion is the largest, but nerves extend from all the ganglia along the length of the body. Chaetognaths have two compound eyes, each consisting of a number of pigment-cup ocelli fused together. In addition, there are a number of sensory bristles arranged in rows along the side of the body, where they probably perform a function similar to that of the lateral line in fish. An additional, curved, band of sensory bristles lies over the head and neck.
Materials are moved about the body cavity by cilia. Waste materials are simply excreted through the skin and anus.
The arrow worm rhabdomeres are derived from microtubules 20 nm long and 50 nm wide, which in turn form conical bodies that contain granules and thread structures. The cone body is derived from a cilium.[9]
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