NewLec25-12-62บทนำทั่วไปของหนอนพยาธิตัวตืด

บทนำทว่ั ไปของ หนอนพยำธติ วั ตดื General Introduction to Cestodes 25/12/62 (2 ชว่ั โมง) ผศ. น.สพ. คมั ภรี ์ พฒั นะธนงั

Class Cestoidae Phylum Platyhelminthes Formerly called Cestoda Cestode or tapeworm (ribbon-like)

Class Cestoidae 11 orders  9 orders (annelids, fishes, amphibia or reptiles)  2 orders (domestic animals and men)*

Class Cestoidae  Usually segmented endoparasites in host’s digestive tract  Body divided into segments called “Proglottids”  No epidermis or cuticle  Specialized Tegument Microtrix  Complete absence of alimentary canal



Class Cestoidae 2 Subclass S.c. Cestodaria=minor group S.c. Eucestoda=major group*

Subclass Cestodaria  Small group occuring chiefly in marine fishes  Unsegmented (a single segment)  No scolex or proglottid and many characteristics similar to trematodes

Subclass Eucestoda  Morphology- 3 distinct regions: Scolex, Neck, Strobila 1. Scolex or head (p.scolices); holdfast organ 1.1Acetabulate scolex  armed scolex, these hooks are usually grouped at the apical end of the scolex on a protusible rostellum

H. nana (SOURCE: D. Scott Smith, M.D./CDC)

Subclass Eucestoda 1.2 Bothriate scolex  usually 2 longitudinally arranged, shallow depression called bothria (s. bothrium)  Located on dorsal and ventral or rarely 4 to 6

D. latum https://www.cdc.gov/dpdx/diagnosticprocedures/s tool/morphcomp.html

Subclass Eucestoda  Morphology 2. Neck region  situated immediately posterior to scolex

Subclass Eucestoda  Morphology 3. Strobila  Linearly arranged segments called proglottids form a chain  Newest segments at neck and oldest at tail end

Neck

Subclass Eucestoda Segmentation (Strobilation)  Asexual process of forming segments or proglottids  Scolex  neck  young segments (immature)  old segments (mature)  oldest segment (gravid)

Subclass Eucestoda Body wall  Several layers thick  Outer most is“tegument” (nonciliated cytoplasmic syncytium overlying muscle layers) * syncytium= A multinucleated mass of cytoplasm that is not separated into individual cells



Subclass Eucestoda Body wall  some tapeworms, the surface of the tegument is covered in numerous highly modified microvilli called \"microtriches\"  Pinocytosis and exocytosis (excretion) can occur here

microthriches Tegument of flukes Tegument of tapeworm

Subclass Eucestoda Excretory system  Most through body wall  Protonephridial system in tapeworms closely resembles that in trematodes, although the arrangement of the major collecting ducts differ

Subclass Eucestoda Nervous system  Typical no specialized sense organs  Continuous along proglottids  Brain in scolex and 2 lateral cords run longitudinally through strobila

Subclass Eucestoda Nervous system  Ring-like commisures in each proglottid  Sensory nerve endings in tegument  No sense organs



Subclass Eucestoda Respiration  Largely anaerobic, but have enzymes for aerobic respiration also

Subclass Eucestoda  Reproductive system  The majority of tapeworms are hermaphrodites  Monoecious Self fertilization within single proglottid and between proglottids  Dioecious Cross fertilization is necessary; Copulation between 2 worms if they bump into each other in the gut of the host

Subclass Eucestoda Reproductive system  Complete reproductive system in each proglottid  Basic structure similar to digenetic trematodes  Vagina and cirrus usually open together through a genital atrium

Subclass Eucestoda Reproductive system  Fertilized eggs usually stored in blind uterus.(except for pseudophyllidean)  Terminal proglottids packed with eggs break off and eggs are freed and pass out through intestine in feces or proglottids crawl out anus by themselves. (cyclophyllidean)

Testes Vitellaria Genital atrium Uterus Vagina Ovary Pseudophyllidean reproductive organ



Cyclophyllidean reproductive organ



Subclass Eucestoda Order Pseudophyllidea (Pseudophyllidean group) Order Cyclophyllidea (Cyclophyllidean group)

Pseudophyllidean group Family Diphyllobothriidae  Genus Diphyllobothrium  Genus Spirometra

Diphyllobothriu m latum





ac 200 mm 200 mm b d 1 mm 50 mm

50 mm







Spirometra mansonoides







Pseudophyllidean group  Most of the species of this group are parasitic in fish  Two genus belonging to genus Diphyllobotrium and Spirometra are parasitic in dogs, cats, including man

Pseudophyllidean group  Scolex likes spatula and having muscular dorsal and ventral grooves called bothria

Bothria Pseudophyllidean scolex

Pseudophyllidean group  Median ventral position of the genital pore and uterine pore present  Diphyllobothrium spp., Spirometra spp.

Cr: http://www.biologydiscussion.com/invertebrate-zoology/12-representative-types-of-platyhelminthes/28958