8) Extraplacental membranes



The trophoblast of the free membranes degenerates soon after implantation. There is no decidua capsularis on the chorion laeve. 9) Trophoblast external to barrier



There are large collections of compact trophoblast ("Träger") into which the connective tissue of the mesoderm and villous capillaries project initially. It contains numerous mitoses in early pregnancy but this region does not generally form anchoring villi.



There is no true maternal vascular invasion by the trophoblast. Some of the Träger columns are attached to the basal myometrial spongy network, the only locus where the maternal endothelium is defective (Ramsey, 1982). 10) Endometrium



There is no real decidua at the base of the placenta, which has the villi attached to a spongy (?)myometrial layer of sinusoids. Mossman (1987) speaks of decidua, however, we have not been able to see it and Ramsey also denied its presence. 11) Various features



There are no other endometrial features of significance. Galbreath (1985) suggested that the four uterine folds that are present lead to the "nesting" of the initial blastocyst at the fundal depression and that this was related to the polyembryony. I have noted above, however, the reasons why Enders (2002) disagrees with that concept, as the folds are too soft and could readily be pushed aside by an expanding blastocyst. The endometrial space of the fundus, occupied by the blastocyst in early stages (these folds essentially retain the blastocyst), basically prevents the embryo from being moved into the uterus during the long stage before implantation occurs. It is unknown how the placenta detaches from the spongy surface of the myometrium and how the endometrium regenerates subsequently. 12) Endocrinology



A single corpus luteum is present in either ovary and persists through pregnancy. Progesterone is present during preimplantation stage, becomes elevated immediately after implantation and later falls in gestation when the placenta contains progesterone (Labhsetwar & Enders, 1968). Peppler & Stone (1980) determined the progesterone levels from blood. He found elevation to occur after implantation and to remain at the same level (20 ng/ml) until term. The follicular development has been described by Peppler & Canale (1980).



Male testosterone levels at various stages are reviewed by Peppler & Stone (1981).



The fetal adrenal glands have a typical "fetal zone" similar to that of primates. Its function has been investigated by Brinck-Johnsen et al. (1967). It has been found that the presumed reason for problems associated with captive propagation is an adrenal-induced steroid change (Rideout et al., 1985).



The circadian rhythm and rhythmic melatonin studies were reviewed by Phillips et al. (1984) who described the epiphysis (pineal gland). Strauss (1981) reported that the pituitary gland contains more LH during the period of delayed implantation than nonpregnant animals.



13) Genetics



Both species of Dasypodidae have 64 chromosomes, with 18 metacentrics, 44 acrocentric elements, a submetacentric X and an acrocentric Y chromosome.

Karyotypes of male and female nine-banded armadillo.

Hybrids are unknown.



Initial molecular characterization has been published by Prodöhl et al. (1996). They examined especially the dispersion of MZ litters and the question of inbreeding at the periphery of the animals' expansion. In a later presentation (Loughry et al., 1998) this group stated that the possible reason for the polyembryony might be the lodging of the blastocyst of the peculiarly-shaped uterus. That has been referred to above, but is extremely speculative and needs much more study. Besides, why four in this species while the mulita has so many more MZ embryos? But the investigators showed genetically that, indeed, the quadruplets are genetically identical ("clones" as they called them). Also, they did not distribute widely over several years (about 200 meters!). One should then anticipate that, ultimately, the gene pool might become considerably restricted.



The number of "scutes" that compose the bands is around 566 per animal. Its inheritance and variations observed were reported in an extensive publication by Newman and Patterson (1911). Storrs & Williams (1968) found considerable differences in many bodily parameters and chemical values of the newborn monozygotic quadruplets.



14) Immunology



Anderson & Benirschke (1963) believed that the MZ quadruplets were immunologically distinct and that inter-quadruplet skin rejection could occur. This was in error, as Billingham & Neaves (1980) later showed.



Enders & Welsh (1993) have argued that there is little or only brief exposure in armadillo (primate and rodent) trophoblast to the maternal connective tissue and that this factor may be one reason for the lack of immunologic "rejection" of the genetically different embryonic structures.



15) Pathological features



A choriocarcinoma has been described after treatment of a female armadillo with thalidomide ["Contergan" in Germany] (Marin-Padilla & Benirschke, 1963). From studies by Storrs (1978) and others it has become known that nine-banded armadillos are susceptible to infection with Mycobacterium leprae and can succumb with widespread lepromatous lesions. The disease exists in the free-living armadillos of Louisiana and Texas but has not been reported from South American specimens. Nevertheless, Storrs et al. (1975) showed that mulitas and D. kappleri, another South American dasypodid species can be infected with this organism experimentally.



Many armadillos are hunted with dogs, and suffer tail wounds as a consequence. These become frequently a source of sepsis.



The causative organism of Chagas' disease, Trypanosoma cruzi, has been identified in this species (Barreto et al., 1985) and the animal has been considered to be a reservoir for this agent.



We have seen a widespread skin infection from the flea Tunga penetrans in a nine-banded armadillo from Paraguay. This originally South American flea has spread widely and affects humans as well. Smith & Procop (2002) described the details of the histopathology of skin biopsies from seven patients who had recently traveled to tropical climates. The histologic appearance of the flea is characteristic and well described in that contribution.