The taxonomy of the genus Aponema Jensen, 1978 is discussed. An emended
diagnosis and identification keys at species level are provided. Two
Aponema species - A. decramerae and A. mnazi are transferred from the
genus Aponema to Microlaimus because of the presence of two testes. One
known Microlaimus species, Microlaimus nanus Blome, 1982, is
transferred from the genus Microlaimus to Aponema because of the
presence of a single testis in males. Three new Aponema species are
A. bathyalis sp. n. is characterized by a small body, smooth or
slightly transversely striated cuticle, amphids with rod-like
protruding corpus gelatum, almost round pharyngeal bulb and presence of
three papilliform precloacal supplements in males. A. bathyalis is
similar to A. nympha and A. nanum but differs from the former by the
position of amphidial fovea (at about 1.5 head diameters from anterior
end vs less than 0.7 head diameters from anterior in A. nympha) and
from the latter by the presence of a gubernaculum, a protruding corpus
gelatum from the amphidial fovea and by the shorter tail (c = 8.2-11.3
vs c = 5.8-7.8).
A. minutissima sp. n. is characterized by a very small slender body,
transversely striated cuticle, roundish amphidial fovea, spherical
pharyngeal bulb, presence of short somatic setae, large spermatozoa,
and a weakly developed copulatory apparatus without gubernaculum. It
differs from the other Aponema species by the small body size
(0.20-0.43 mm). It mostly resembles A. bathyalis sp. n. but differs by
smaller size, slightly striated cuticle and absence of a gubernaculum.
A. westindicum sp. n. is characterized by a larger body, annulated
cuticle, discernible dorsal tooth, pyriform pharyngeal bulb and conical
tail. It differs from A. nanum (Blome, 1982) by longer body size and
structure of buccal cavity.
All Aponema species described in this paper are characterized by
monorchic males without gubernacular apophyses, females with two
outstretched ovaries and a conical tail.