Rev 12/01/2022
Stegelleta Thorne, 1938
The genus Stegella was erected by Thorne (1937) with Stegella incisa Thorne, 1937 as type species,.Due to homonomy with a hydroid, Stegella Stechow, 1919, it was later renamed and became Stegelleta Thorne, 1938 (Bostrom & Holovachov, 2014).
The genus Stegelleta consists of cephalobids with the cuticle tessellate, appearing as plate-like segments over entire body; labial probolae furcate, prongs simple or with few branches; cephalic probolae variable, rounded axil borders or flap-like with membranes; and the wing area unusually broad with a medial line and crenate borders (Bostrom & Holovachov, 2014)..
Cuticle annulated, without distinctly annulated internal layer; annuli with longitudinal incisures (tessellated).
Lateral field with two or four wings (appearing as three, four or five incisures); ending at tail terminus in females and in males.
Lip region weakly offset, with six globular lips arranged in three pairs: one dorsal and two subventral. Pairs of lips separated by primary axils; guarding processes absent; secondary axils undeveloped.
Cephalic probolae absent or ias one acute tine extending along the primary axil, occurring only on lateral lips or on all six lips.
Labial probolae elongate-conoid with broad basis, bifurcated about halfway forming two slender prongs, in some species further bifurcated apically.
Six labial and four cephalic papilliform sensilla .
Amphidial aperture slit-shaped, located on lateral lips.
Stoma divided into cheilo-, gymno- and stegostom: cheilostom barrel-shaped with strongly sclerotized bacilliform cheilorhabdia; gymnostom weakly developed, as wide as stegostom, with weak gymnorhabdia; stegostom consists of a funnel-shaped prostegostom and variably shaped mesostego-, metastego- and telostegostom parts.
Metastegostom with a denticle.
Pharynx cephaloboid: pharyngeal procorpus and metacorpus cylindrical, lining of procorpus and metacorpus are of same thickness; isthmus narrower than metacorpus; basal pharyngeal bulb oval, with strongly developed valves.
Nerve ring encircling posterior part of metacorpus or anterior part of isthmus.
Excretory pore opens at level of nerve ring, at posterior part of metacorpus or anterior part of isthmus.
Deirids present.
Phasmids located at about one-third to half of tail length in both sexes.
Female
Reproductive system cephaloboid; posterior part of ovary straight; spermatheca present; postvulval uterine sac present; vagina straight; vulva flat, vulval flap absent or present.
Rectum short (1–2 times longer than anal body diameter).
Female tail conoid or subcylindrical, straight, tail terminus bluntly rounded or truncate.
Male
Reproductive system cephaloboid; spicules cephaloboid with manubrium and corpus of approximately equal width; gubernaculum plate-like or wedge-shaped; cornua crurum present.
Male genital papillae: at least one ventrosublateral pair located anterior to cloaca; one ventrosublateral pair located at the level of cloacal opening; two pairs located at middle of tail length; and three pairs (lateral, subventral and subdorsal) near tail terminus; there is a midventral papilla on anterior cloacal lip.
Male tail conoid, arcuate ventrad, tail terminus bluntly rounded.
from Bostrom & Holovachov, 2014
Key to the species of Stegelleta as of 2014
1. a. Lateral field with five incisures; cuticle with over 40 longitudinal rows of blocks; labial probolae biacute apically ............................................... S. tuarua Yeates, 1967
b. Lateral field with three-four incisures; cuticle with 12 to 26 longitudinal rows of blocks; labial probolae bifurcate half of length ............................. 2
2. a. Labial probolae with minute secondary bifurcations at tips ............................................................................................................................... S. iketaia Yeates, 1967
b. Labial probolae without minute secondary bifurcations at tips ............................................... .............................. .............................. ..... 3
3. a. Cephalic probolae in shape of acute tines present on all six lips along the primary axils; cuticle with 24 to 26 longitudinal rows of blocks .............. S. arenaria Bostr�om & Holovachov, 2012
b. Cephalic probolae absent, or present only on lateral lips along the primary axils; cuticle with 12� to 22 longitudinal rows of blocks ........................ 4
4. a. Cuticle with 22 longitudinal rows of blocks ................................................................................................................................................... S. georgica Bagaturija, 1973
b. Cuticle with 12� to 16 longitudinal rows of blocks ........................................................................................ .............................. .................. 5
5. a. Parthenogenetic species; spermatheca 7 to 13 μm long; postuterine sac about 7 to 17 μm long ............. ............................................................... S. ophioglossa Andrassy, 1967
b. Amphimictic species; spermatheca 24 to 43 μm long; postuterine sac about 22 to 36 μm long ........ ............................................................ .... 6
6. a. Cephalic probolae absent .......................................................................................... ....................................... ..................... ............... S. incisa Thorne, 1937
b. Cephalic probolae setose, present on lateral lips only ................................................................................ .......................................... S. laterocornuta Bostrom & Holovachov, 2014
Adapted (slightly) from Bostronm and Holovachov (2014)
Species of the genus are considered rather rare inhabitants of terrestrial habitats, although they occur on all continents except Antarctica (Bostronm and Holovachov 2014).
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Bacteria
Andrassy, I. 2005. Free-living Nematodes of Hungary, I (Nematoda errantia). Pedozoologica Hungarica 3. Hungarian Natural History Museum, Budapest, Hungary. 518p.
Bostrom, S. and Holovachov, O. 2014. Descriptions of species of Stegelleta Thorne, 1938 (Nematoda, Rhabditida, Cephalobidae) from California, New Zealand and Senegal, and a revision of the genus. European Journal of Taxonomy 87:1-19. DOI: https://doi.org/10.5852/ejt.2014.87
Thorne, G. 1937. A revision of the nematode family Cephalobidae Chitwood and Chitwood, 1934. Proc. Helminth Soc. Wash. 4:1-16.
Thorne G. 1938. Notes on free-living and plant-parasitic nematodes. IV. Proceedings of the Helminthological Society of Washington 5: 64-65