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PHYLUM PENTASTOMA

INTRODUCTION TO THE PENTASTOMA

Pentastoma (pen-ta-STO-ma) is made of two Greek roots that mean "five mouths" [five -pente (πέντε); and mouth -stoma (στόμα)]. The reference is to the five lobes around the mouth.

The pentastomes are parasites of vertebrate carnivores and usually have an intermediate host for their larvae. They appear to be highly modified members of the panarthropoda. Indeed, Margulis and Schwartz (1998) and Brusca and Brusca (2003) place them together with the crustaceans. Nielsen (2001) is more careful and suggests a "proarthropod" position mainly because they are so modified and synapomorphies are so difficult to identify.

*A. Armillifer, adult female (L) and two adult males (R).*	B. Detail of the anterior end of Linguatula.	C. SEM micrograph of the head of a pentastome that show the characteristic hooks.	D. Larval pentastomes from the body cavity of a swordtail fish.
Images taken from: A-C: http://www.stanford.edu/class/humbio103/ParaSites2001/pentastomiasis/Erica%20parawebsite.html D: http://edis.ifas.ufl.edu/FA090

SYNOPTIC DESCRIPTION OF THE PHYLUM PENTASTOMA

The following description of the phylum Pentastoma came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000).

I. SYNONYMS: pentastomes, tongue worms.

II. NUMBER: > 100 species known.

II. PHYLUM CHARACTERISTICS:

A. Structure

Symmetry: Bilateral

Body Cavity: Coelomic pouches lost early in development.

Body Covering: Covered by a porous cuticle that bears .

Support: Hydrostatic skeleton.

Digestive System: "Head" with five short lobes. The middle one contains the terminal mouth (the other four appendages each bear a hook). Food tube simple with terminal anus.

Circulatory System: Absent.

Locomotion: Animals attach to host by 4 stubby, unjointed appendages that end in a hook. Larvae with short, unsegmented legs.

Excretory System: Absent.

Nervous System: Very simple with up to 5 cephalic ganglia.

Endocrine System: None.

B. Reproduction:

Reproductive System: Dioecious. Internal fertilization. Oviparous.

Development: Three larval stages; the first stage develops in the egg after it is ingested by the intermediate host; the second stage resembles a tardigrade and burrows through the gut of the host where it seeks out organs like the liver, encapsulates and forms the third larval stage. The adult develops when the encapsulated larva is eaten by a host animal.

C. Ecology: Blood-sucking parasites of carnivores as adults. Parasites of intermediate hosts as larvae.

HIERARICHAL CLASSIFICATION OF THE PENTASTOMA

Most recent sources (e.g. Brusca and Brusca, 2003; and Margulis and Schwartz, 1998) place the pentastomes firmly within the Crustacea. However, Nielsen (2001) is more cautious because clear synapomorphies cannot be found. I accept that they likely are crustaceans; however, I will follow the cautious approach of Nielsen. Thus, I have a system with one class (I call it Class Pentastomatida) with 2 orders.

CLASS PENTASTOMATIDA

Pentastomum, Reighardia, Cephalobaena, Porocephalus, Armillifer, Linguatula, Waddycephalus.

This page is maintained by Jack R. Holt. Last modified: 01/08/08.