ABATHYMERMIS-FISERI N-SP AND ABATHYMERMIS-SHOCKI N-SP (NEMATODA, MERMITHIDAE) FROM MIDGE (DIPTERA, CHIRONOMIDAE) IMAGOS EMERGING FROM LAKE ITASCA, MINNESOTA, USA
Aa. Johnson et Mg. Kleve, ABATHYMERMIS-FISERI N-SP AND ABATHYMERMIS-SHOCKI N-SP (NEMATODA, MERMITHIDAE) FROM MIDGE (DIPTERA, CHIRONOMIDAE) IMAGOS EMERGING FROM LAKE ITASCA, MINNESOTA, USA, Invertebrate biology., 114(1), 1995, pp. 19-26
Abathymermis fiseri n. sp. and Abathymermis shocki n. sp., two closely
related species of mermithid nematodes, are described from adult chir
onomids emerging from Lake Itasca, Minnesota in early June of 1992 and
1993. These are the first two species of Abathymermis reported outsid
e the Palearctic Realm. The species are distinguished from other suffi
ciently described members of the genus by their larger size, long prot
ractor and abbreviated bursal musculature, longer spicules, and the po
sition of the posterior extention of the trophosome in the male. A. fi
seri n. sp. and A. shocki n. sp. are separated by several quantitative
characteristics including spicule lengths, body widths at most levels
, and number of genital papillae. In addition the pointed tail and the
presence of cephalic superficial cuticular annuli in A. shocki n. sp.
differ from the rounded tail and absence of annuli in A. fiseri. n. s
p. Eggs of A. fiseri n. sp. require fertilization to initiate embryoge
nesis, while eggs of A. shocki n. sp. can develop parthenogenetically,
although males are known-the first demonstration of parthenogenesis r
esulting in viable offspring in an aquatic mermithid. The host chirono
mid species remain unknown. Eleven species of mermithids from eight ge
nera have now been reported from Lake Itasca chironomids. Lake Itasca
chironomids.