1. Chapter 31 Phylum Acanthocephala

2. Form and Function
Throughout their evolution there has been a reduction in muscular, nervous, circulatory and excretory systems; a complete loss of a digestive system
They are pseudocoelomates; pseudocoelom is essentially filled with reproductive organs

3. General Morphology
The body consists of an anterior proboscis, a neck, and a trunk
The proboscis is highly variable in shape and is covered by numerous sclerotized hooks
The proboscis is hollow and fluid filled; it can be everted (extended) or retracted into a proboscis receptacle

4. General Morphology cont.
Lemnisci are paired organs that extend into the body cavity from the neck region; central canal of each lemniscus is continuous with the lacunar system
The lemniscus serves as a fluid reservoir when the proboscis is invaginated; may also have a function in fat metabolism

5. The rest of the body, posterior to the neck is called the trunk
General Morphology cont.
Located within the receptacle is a nerve ganglion that comprises the cerebral ganglion (brain)
The rest of the body, posterior to the neck is called the trunk
Many species have spines embedded in the trunk to aid in the attachment to the host’s mucosa of the intestine
The trunk houses the reproductive structures; also functions in absorbing and distributing nutrients

6. Tegument
The tegument is a syncytium with many functions, including protection, inactivation of the host’s digestive enzymes by charge effects, osmoregulation, concentration of nutrients, ion transport, etc
The outer surface coat is a carbohydrate rich glycocalyx
Closely packed pores at the tegument surface lead to pore canals that branch and anastomose
This fluid filled system of channels is called the lacunar system
It’s function is obscure; it may be important to the body wall musculature or serve as some kind of “circulatory system”

7. Reproductive System Male System
2 testes, each with vas efferens leading to a common vas deferens and/or a small penis
Males typically have cement glands; secrete a copulatory cement, allowing the vagina to be plugged following sperm transfer
Males also have a copulatory bursa, a bell shaped structure that is typically invaginated into the posterior end of the body cavity
A muscular sac is attached to the bursa and when it contracts fluid is forced from the lacuna system of the bursa causing it to evert

8. Reproductive System cont.
Female System
Ovary is actually fragments of ovarian balls, that lie in the ligament sac or pseudocoel
Posterior end of the ligament sac is attached to a muscular uterine bell; allows mature eggs to pass through into the uterus, vagina, and out the genital pore into the feces; immature eggs are returned to the ligament sac

9. Excretory System Nervous System
Protonephidria serve as excretory organs
Nervous System
Consists mainly of a ganglion in the proboscis sheath and of nerves that connect the ganglion to other organs and tissues
A pair of genital ganglia, with nerves is present in the male
Sense organs are found in the proboscis and in the penis and male bursa

10. Early Development
Fertilized eggs go through early embryological development in the ligament sac or pseudocoel
When eggs emerge from the gonopore they contain hooked larvae called the acanthor
A host must eat the eggs before the embryos can hatch
There is typically one intermediate host; no free-living stages occur

11. Generalized Life Cycle
An egg eaten by an arthropod hatches into an acanthor, develops into an acathella, becomes a juvenile (which may progress to a cystacanth), and is eaten by the final, vertebrate host, in which it becomes an adult
Within the invertebrate host, the acanthor is liberated from the egg, bores through the gut wall, and develops into an acanthella
The acanthella then becomes a juvenile
The vertebrate host becomes infected by eating the arthropod intermediate host

12. Life Cycle of Moniliformes moniliformes/dubius
Lives in the small intestine of rats, mice, dogs, and cats
Eggs are eaten by beetles (flour beetles) or cockroaches
Acanthors are deposited in the gut and leave with the feces
If acanthors are ingested by a cockroach, they hatche from the shell and penetrate the wall of the digestive tract

13. The acanthellae develop into the infective stage - cystacanth
Life Cycle of M. moniliformes/dubius cont.
They pass through the gut wall, enter the homocoel and undergo growth and differentiation into an acanthellae
The acanthellae develop into the infective stage - cystacanth
If a cockroach is eaten by a rodent, it everts its proboscis and embeds in the small intestine
Male and females grow to maturity and copulate; shelled acanthors then develop in the pseudocoel of the female

14. Development in the Cockroach
The shelled acanthor is stimulated by pH and carbon dioxoxide tonicity of the external medium to secrete a chitinase which acts upon the chiton layer of the shell
Acanthor then penetrates the gut and goes to the hemocoel
Development in the Rat
Dormant cystacanth in the cockroach are eaten by the rat
It is then activated by bile salts and bicarbonate of the small intestine
Results in the eversion of the proboscis and its attachment to the host mucosa

15. Effects on Behavior
Cockroaches infected with Moniliformes moniliformes move more slowly, travel less and spend more time on exposed surfaces
These behavioral changes apparently increase the probability of transmission