Terrestrial Isopod Armadillidium Vulgare Research Articles

ANATOMY OF THE CENTRAL NERVOUS SYSTEM OF ARMADILLIDIUM VULGARE (LATREILLE) (ISOPODA)

In an anatomical investigation of the central nervous system of the terrestrial isopod Armadillidium vulgare (Latreille), some specimens were dissected; others were sectioned and stained for light microscopical study. The brain, consisting of protocerebral, deutocerebral, and tritocerebral divisions, is situated ventrally in the extreme anterior region of the cephalothorax. The protocerebrum is bilobed and divided dorsally by a deep, median cleft. Each lobe (=optic lobe) tapers to form a large optic nerve. A pseudofrontal organ is suspended ventrally from the distal extremity of each optic lobe. A pair of accessory lobes extends ventrally beneath the main lobes of the protocerebrum. The deutocerebrum is much reduced in size, reflecting an apparent adaptive trend among terrestrial isopods (and amphipods) toward reduction of the antennules and associated loss of olfactory function. The well-developed lobes of the tritocerebrum extend laterally and continue as the circumesophageal connectives, completing encirclement of the esophagus to form a paired connective that unites with the subesophageal mass. The subesophageal mass is a fusion of the mandibular, maxillulary, maxillary, and maxillipedal ganglia. The ventral nerve cord, for most of its length, consists of seven pereionic ganglia joined by paired longitudinal connectives and smaller, single, median intermediate connectives. Six pairs of pleonic ganglia are fused into a single pleonic mass. Characteristic groupings of nerve cell bodies occur on the surfaces of the brain and ventral nerve cord. Distinctive, small, and densely packed glomerular cells occupy the surfaces of the optic lobes. Neuropiles and fiber tracts form conducting pathways, although those of the ventral cord are not so distinct morphologically as are some in the brain. Strong tagmatization is suggested by fusion to form a single pleonic mass.

Occurrence of the Isopod Iridovirus in European Armadillidium and Porcellio (Crustacea, Isopoda)

First record of iridovirus infections of terrestrial isopods (Armadillidium vulgare and Porcellio scaber) in Europe (The Netherlands). Infested specimens can be detected by their bright blue color.

Plagiorhynchus formosus Van Cleave, 1918, a Synonym of Plagiorhynchus cylindraceus (Goeze, 1782) Schmidt and Kuntz, 1966

When he first described Plagiorhynchus formosus, Van Cleave (1918, Trans. Am. Microsc. Soc. 37: 19-48) did not differentiate his new species from European species, other than to state that the eggs lack polar elongations. He did not consider it to belong in the genus Prosthorhynchus, even though he included, but did not mention, the description of that genus by Kostylev (1915, Ann. Mus. Zool. Acad. Imp. Sci. 20: 389-394) in his Literature Cited. It does, however, fit into the concept of Prosthorhynchus, and was transferred there by Travassos (1926, Mem. Inst. Oswaldo Cruz 19: 31-125). While subsequent authors debated the validity of these two genera, Schmidt and Kuntz (1966, J. Parasitol. 52: 520-527) reduced them to subgenera in the genus Plagiorhynchus Liihe, 1911. In his early years of publication, Van Cleave emphasized the distinctness of New World from Old World acanthocephalan faunas. Later authors seem to have taken this for granted, for there is no study which compares Plagiorhynchus formosus with its European counterpart Plagiorhynchus cylindraceus, also a parasite of Turdidae and other passeriform birds. I was stimulated into considering the conspecificity of those two forms when presented with two juvenile specimens of P. formosus collected in an Australian pigeon by Dr. J. H. Arundel, University of Melbourne, Victoria. Through the kindness of Professor Y. J. Golvan, who redescribed P. cylindraceus, (1956, Ann. Parasitol. 31: 350384), I was able to examine numerous specimens of that species from his collection. Careful comparison of all taxonomic characters generally used revealed no difference whatever between American P. formosus and P. cylindraceus from Europe, Israel, and Australia. Hook numbers, arrangements, and sizes broadly overlap in these specimens, as do other characteristics. In their description of Plagiorhynchus (Prosthorhynchus) taiwanensis, Schmidt and Kuntz (1966, loc. cit.) incorrectly stressed the constancy of lemniscus length in this genus. Subsequent examination of a longer series of P. formosus specimens, as well as the European worms, shows variability of the lemnisci that overlaps in both groups. As the length of the lemnisci was the only character separating P. taiwanensis from P. formosus, the former also must fall as a synonym of P. cylindraceus. The life cycles of P. cylindraceus and P. formosus also support their conspecificity. Sinitsin (1929, J. Parasitol. 15: 287) reported cystacanths of P. formosus in the terrestrial isopod Armadillidium vulgare. Schmidt and Olsen (1964, J. Parasitol. 50: 721-730) subsequently presented a detailed description of P. formosus's development in this host. Dollfus and Dalens (1960, Ann. Parasitol. 35: 347349) reported P. cylindraceus from the same species of isopod. As this crustacean was originally European (Van Name, 1936, Bull. Am. Mus. Nat. Hist. 71: 1-535), it seems possible this acanthocephalan became established in North America, and maybe Australia and the Far East as well, as the range of the sowbug was extended. The synonymies of this species are as follows:

Population Ecology of a Terrestrial Isopod in Two Breckland Grass Heaths

SUMMARY (1) Two superficially similar chalk grasslands in the Breckland of East Anglia provided very different habitats for the abundant terrestrial isopod Armadillidium vulgare (Latreille). At Lakenheath Warren the site was a tussocky grassland, ungrazed, with Festuca spp. covering 65-80% of the area, and most of the isopod population was found in the litter layer (5 cm deep) of the large tussocks throughout the year. At Weeting Heath National Nature Reserve, smaller Festuca tussocks comprised 25-30% of the site, and the isopods moved between the tussocks and the intervening grazed sward. (2) Mean annual population density of A. vulgare on the grazed site at Weeting was 1.4-1.6 times larger than that of the ungrazed site at Lakenheath, which increased to a maximum of 2.8 times at other periods. (3) Differences in population structure between the two sites were detected in terms of age structure, generation distribution and cohort composition.

Some Unique Features in Compound Eyes of Two Isopods

I have observed certain unique features in the ultrastructure of the compound eyes of the terrestrial isopod crustaceans Porcellio scaber and Armadillidium vulgare, using both scanning and transmission electron microscopy.Only about twenty ommatidia, arranged into four rows, constitute an eye, giving the organ the appearance of a cluster of grapes (Fig. 1). A few trichoid sensilla are interspersed between the ommatidia.The dioptric apparatus of each ommatidium is composed of a biconvex, cuticular lens and an underlying spherical crystalline cone. In these isopods each crystalline cone is the secretion of only two cells (Fig. 2), rather than four as in most malacostracans. The suture line between the two cone hemispheres is always parallel to the long axis of the ommatidium.

Water Content and Water Activity in the Cuticle of Terrestrial Isopods

ABSTRACT The water content of the cuticle of both desiccated and non-desiccated terrestrial isopods Porcellio scaber and Armadillidium vulgare was measured. The animals were desiccated for various times (up to 3 h) over silica gel and the mean water content of the cuticle was 54·0 ± 0·78% for P. scaber and 52·7 ± 1·11% for A. vulgare. There was no trend as regards the desiccation time, nor did the body weight affect the water content. The water content of the cuticle remained virtually unchanged as long as the animal was alive in the desiccator. It dropped significantly after the animal had died after having lost some 30 % of its body weight. The cuticular water content of non-desiccated P. scaber tended to be slightly higher than that of desiccated ones. In A. vulgare no significant difference was observed between non-desiccated and desiccated specimens. The water activity of the excised cuticle of the above two species and of Oniscus asellus and Cylisticus convexus was above that of the haemolymph and therefore not in osmotic equilibrium with it. The osmotic equilibrium points were below the osmotic pressures of the blood; the difference amounted from 1·5 to 2·8 atm. in different species. The difference in water activity between blood and cuticle, the maintenance of water content with desiccation, and the drop in water level at death, all indicate the presence of an active mechanism regulating the cuticular water in terrestrial isopods.

Life Cycle and Development of Prosthorhynchus formosus (Van Cleave, 1918) Travassos, 1926, an Acanthocephalan Parasite of Birds

The life cycle of Prosthorhynchus formosus (Van Cleave, 1918) Travassos, 1926 is presented. The terrestrial isopods Armadillidium vulgare, Porcellio laevis, and P. scaber served as experimental intermediate hosts, and chickens and turkeys as experimental definitive hosts. After ingestion of the eggs by the isopod, the acanthor emerges from its shells within 15 min to 2 hr, enters the gut wall of its host, and remains there 15 to 25 days. It then migrates to the hemocoel and develops through the acanthella stage to the infective cystacanth by the 60th to 65th day of infection. Van Cleave (1918) described Plagiorhynchus formosus on the basis of four specimens collected from the flicker, Colaptes auratus, at Bowie, Maryland. In 1926, Travassos reassigned this species to the genus Prosthorhynchus but gave no reasons for the change. Van Cleave (1942) disagreed strongly with this change in generic status and reaffirmed its position in Plagiorhynchus. Golvan (1956) clarified the differences between Plagiorhynchus and Prosthorhynchus and defended its position in Prosthorhynchus. This view, which was upheld by Petrochenko (1956) and Yamaguti (1963), is accepted by the present authors. Jones (1928) extended the host list to include the chicken (Gallus domesticus), robin (Turdus migratorius), and the crow (Corvus americanus). She remarked on the possibilities of this worm becoming an important parasite of domestic fowl. Cuvillier (1934) added the catbird (Dumatella carolinensis), and a thrush Received for publication 17 April 1964. * Part of a thesis submitted by the senior author to the Graduate School of Colorado State University in partial fulfillment of the requirements for the Ph.D. degree, February 1964. This investigation was supported by Training Grant PHS-2E-94 (C2,3) from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, U. S. Public Health Service, and by a fellowship from the Boettcher Foundation, Denver, Colorado. (Hylocichla sp.), and Van Cleave (1942) the towhee (Pipilo erythrophthalmus), starling (Sturnus vulgaris), grackle (Quiscalus quiscala), and hermit thrush (Hylocichla guttata). Chandler and Rausch (1949) found it in the brown thrasher (Toxostoma rufum), and Hunter and Quay (1953) in Macgillivray's seaside sparrow (Ammospiza maritima macgillivaraii). The present report adds the red-shafted flicker (Colaptes cafer) and the domestic turkey (experimental). Sinitsin (1929) reported finding a juvenile of Plagiorhynchus formosus in the sowbug, Armadillidium vulgare, near Washington, D. C. To date, this is the only report on the life history of P. formosus, although Dollfus and Dalens (1960) reported larvae of Prosthorhynchus cylindraceus in A. vulgare in France. This work presents the complete life cycle of Prosthorhynchus formosus as observed under laboratory conditions, utilizing three species of terrestrial isopods as intermediate hosts and domestic fowl as definitive hosts. MATERIALS AND METHODS