Physical characteristics

All tongue worms inhabit the respiratory systems of terrestrial vertebrates. As a consequence, all aspects of their structure and function have adapted to life in this unusual habitat. All are aerodynamic, possessing an elongated, wormlike, mostly cylindrical body, which is rounded both anteriorly and posteriorly. The body is differentiated into an anterior head region, bearing a small ventral mouth flanked by two pairs of retractile hooks, and a long posterior trunk, which carries numerous raised annuli that are not true segments. Sexual dimorphism is pronounced, females are invariably larger than males. Females may be as small as 0.06 x 0.01 in (1.5 x 0.3 mm) (Rileyiella) to 4.7 x 0.4 in (12 x 1 cm) (Armillifer), but males are much shorter and proportionately more slender. The chitinous cuticle is thin, flexible, and translucent, so that in living specimens the body organs, suspended in an extensive fluid-filled haemocoel, are clearly visible. Peristaltic contractions of the body wall musculature affect locomotion, which is comparable with that of soft-skinned dipteran maggots. The cuticle is shed periodically during growth, and simple metamorphosis occurs (developing nymphs resemble adults). Numerous, exceedingly fine, chitin-lined ducts erupt over the entire surface of the cuticle, each connected to an extensive system of subparietal gland cells that abound in the haemocoel immediately beneath the tegu-mental epidermis. Secretion from these glands, composed largely of membranous secretory droplets, is critical to prolonged survival of these parasites in the delicate environment of the lung. Large numbers of distinctive, flask-shaped cells, analogous to those involved in ion transport in other invertebrates, are embedded in the cuticle. Additional gland systems, located mainly in the head (both orders), but also flanking the intestine in porocephalids, discharge copious en-zymic secretions over the head and into hook pits. There are no respiratory or excretory systems.

The sucking mouth leads into a short esophagus, which is separated by a valve from a simple undifferentiated tubular intestine. The intestine terminates at a short rectum. The simple nervous system forms initially as separate ganglia that fuse progressively during development to varying degrees within the two orders. In Porocephalida, all ganglia fuse to form a compact "brain." In cephalobaenids only the most anterior ganglia do so. A variety of small sense organs, often visible as distinct papillae, are arranged over the head, but most are concentrated on the ventral surface around the mouth.

The reproductive system differs between the two orders. The uterus of cephalobaenids is saccate, and the vagina opens anteriorly close to the junction of the head and trunk. In poro-cephalids, the uterus is elongate and tubular. Because it is many times longer than the body, the uterus is irregularly coiled to occupy most of the available haemocoel. The vagina opens near the anus. In both orders, the dorsal ovary leads into a paired oviduct, which passes around the gut. Close to the junction between the oviduct and the uterus are paired spermath-ecae, which are responsible for long-term storage of sperm.

Part of the surface of a rat that was killed, soaked in saline and then enclosed in a polyethylene bag that was left at room temperature for 24 hours. The rat had been infected with eggs of Armillifer armillatus four months earlier. Upon the death of this intermediate rodent host, nymphs excyst and burrow out to the surface using enzymes to digest a route through tissues. Under natural circumstances these nymphs would anticipate liberation into the stomach of a snake! (Photo by John Riley. Reproduced by permission.)

Part of the surface of a rat that was killed, soaked in saline and then enclosed in a polyethylene bag that was left at room temperature for 24 hours. The rat had been infected with eggs of Armillifer armillatus four months earlier. Upon the death of this intermediate rodent host, nymphs excyst and burrow out to the surface using enzymes to digest a route through tissues. Under natural circumstances these nymphs would anticipate liberation into the stomach of a snake! (Photo by John Riley. Reproduced by permission.)

A culture of (mainly) eighth instar nymphs of Armillifer armillatus. These have been sieved and washed from a blood-based culture medium; normally they would be resident in the lung of an African gaboon viper. The raised annuli are bands of circular muscles and gland cells and do not represent true segments. (Photo by John Riley. Reproduced by permission.)

A culture of (mainly) eighth instar nymphs of Armillifer armillatus. These have been sieved and washed from a blood-based culture medium; normally they would be resident in the lung of an African gaboon viper. The raised annuli are bands of circular muscles and gland cells and do not represent true segments. (Photo by John Riley. Reproduced by permission.)

The lower reproductive tract of males comprises paired, elongate penises—basically thin, coiled tubes of chitin—close to elaborate chitinous spicules called dilators. Dilators may be extruded through the anterior genital pore by muscles and thereby carry the tip of the penis either to the entrance of the spermathecal ducts in cephalobaenids or into the vagina/uterus in porocephalids. Peristalsis within the uterus of porocephalids pulls the ornamented heads of the paired penises toward the spermathecal ducts. The testis is dorsal, and the paired vasa deferentia empty into a seminal vesicle, which functions as a sperm storage depot before intromission.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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