Worm Breeder's Gazette 13(3): 108 (June 1, 1994)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.


Lynn Carta[1], Kelly Thomas[2], Paul Sternberg[1]

[1]Division of Biology, California Institute of Technology, Pasadena, CA
[2]University of Missouri, Kansas City, Missouri

Morphological, life cycle and molecular characteristics are used to describe seven hermaphroditic species of Oscheius (Andrassy, 1976) including O. brevesophaga, n. sp. O. mesoesophaga n. sp., O. fijiensis n. sp., O. spiculunca n. sp.. O. longirecta n. sp., O. subvulva n. sp., and O. longimascula n. sp. These were compared with living isolates of Rhabditis (Oscheius) tipulae (Lam and Webster, 1971 ) Sudhaus, 1993, Rh. (O.) dolichuroides (Anderson and Sudhaus, 1985) and Dolichorhabditis dolichura (Schneider, 1866) Andrassy, 1983 provided through David Fitch. Starvation induced males were mated among the isolates below to define distinct biological species. These species were sequenced over a 310 nucleotide bp region of the nuclear 28S rRNA. Vulval anatomy was observed in the early L4 stage. Life cycle was determined from egg to egg at 20û C. to within half a day.

Four major groups are defined by larger base pair difference gaps between than within groups. These correspond to somewhat distinct groups morphologically and developmentally. The approximately 40 bp gap between the Tipulae and Dolichura group is as large as the gap between the Tipulae group and Caenorhabditis, the closest molecular and morphological outgroup.

The only nonfertile hybrids produced were those of O. mesoesophaga hermaphrodites mated with O. tipulae males. With just 1 base pair difference between each sp. in the series, O. brevesophaga, mesoesophaga and tipulae are best distinguished by esophageal length. By contrast, three interbreeding isolate groups of O. brevesophaga could be defined by 1 or 2 bp changes. Thus, at least 2 bp changes may be necessary to distinguish a biological species in this group, while no change may be sufficient (e.g. as in Rhabditis anomala and a new hermaphroditic sibling species, Rhabditis heranamaloides). This can help define species where males are nearly impossible to find or mate.

Vulval anatomy revealed that 2- lineages generated 4 cells and 3' generated 4 cells (4:4) in the three non-Dolichura groups, and 4:2 cells in three of the four species of the Dolichura group examined. (Caenorhabditis has a 7:2 pattern.) A significant number of O. subvulva individuals showed an interesting asymmetry with 4 cells resulting from the 3' P4 .plineage, while the 3' P8 .plineage gave only two cells.

The revised genus Oscheius (Andrassy, 1976)* can be distinguished from Caenorhabditis by absence of median bulb, dorsal opening of rays 5 and 8 on the fan (5 and 7 in Caenorhabditis, 4 and 7 in some Pellioditis and C. plicata), 9 or 10 rays, peloderan or pseudopeloderan male tail and 2'-:3' vulval progeny of 4:4 or 4:2, long rectum (>25 µm), generally swollen or hooked spicule tips, and prominent excretory canal. This genus will encompass all species currently within Dolichorhabditis (Andrassy, 1983), Oscheius (Andrassy, 1976), some species of Rhabditis Dujardin, 1845 and Pellioditis (Dougherty, 1953 ) Timm, 1960.

*Rhabditis (Oscheius) (Sudhaus, 1993) is the revised equivalent of Andrassy's original genus, distinguished by "an extremely long rectum, spicules with knobbed terminus and sloping head, and long, elongated and convoluted cervical duct," and includes some species referred to above (Sudhaus, W. 1993. Nematologica 39:234-239).

Table 1. Collection data on new hermaphroditic Oscheius spp.

Dolichura group: representative sp. Dolichorhabditis dolichura (Schneider, 1866) Andrassy, 1983, Vulva usually > 50% (2° :3° usually = 4:2), Bursa with 9 rays, Spicules with swollen tips, Life cycle 5 days or more at 20' C.

1. subvulva n. sp.

a. PS-330 (J. Purcell, Pasadena, California)

b. PS-1017 (L. Huang, Pasadena. California)

2. longimascula n. sp.

a. PS-1173 (NC-II, L. Carmichael, Chapel Hill, N. Carolina)

PS-1209 (NC-I, L. Carmichael, Chapel Hill, N. Carolina)

Tipulae group: representative sp. Rhabditis (OscheiusJ tipulae (Lam & Webster, 1971) Sudhaus, 1993, Excretory pore not as anterior as isthmus, Vulva ² 50%, (2°:3° = 4:4), Spicules <30µ with tips not visibly swollen, 2 setose stomatal denticles, 9 bursal rays, Life cycle < 5 days.

3. brevesophaga (old "carpathica") n. sp.

a PS-1022 (C. Winter, Sao Paulo, Brazil)

b. PS-1131 (W. Wood, Tokyo)

c. PS-959 (C. Bertuccioli, NY, NY)

d. PS-966 (S. Burden, Cleveland, OH)

e. PS-1005 (K. Liu, Washington, DC)

f. PS-986 (D. Hamill, Kansas)

g. PS-334 (A. M., Pasadena, CA)

h. PS-1180 (J. Peneflesh, Boston, MA)

i. PS-1181 (Cai, Michigan)

j. PS-1170 (Accinelli, D.. Huntsville. ALA)

4. mesoesophaga n. sp.

a. PS-320 (Frank W., Pasadena, CA)

b. PS-1187 (J. Trager, San Marino, CA))

c. PS-335 (RMS. Pasadena. CA)

Insectivora group: representative sp. Oscheius insectivora (Koerner in Osche, 1952) Andrassy, 1976, Vulva = 50% (2°-:3° = 4:4), 9 or 10 fan rays, Stomatal glottoid with 2 to 3 warts or denticles, Life cycle < 5 days at 20° C., Spicule tips hooked or acute, Spicule > 30µ, Bursa usually pseudopeloderan (except pheropsophi), Bursa with 10 rays, ³ 4 lateral lines, protruding vulval lips. 1994).)

5. spiculunca n. sp.

a. PS-1004 (K. Liu, Baltimore, Maryland)

b. PS-1006 (P. Bokor, NYC, NY)

c. PS-1302 (K. Pinson, Ann Arbor, Michigan)

6. Iongirecta n. sp.

a. PS-1128 (W. Wood, Guang Zhou, China)

b. PS-70 (W. Wood, Shanghai, China)

c. PS-757 (P. Kayne, Honolulu, Hawaii)

d. PS-985 (H. Browning, Lafayette, Indiana)

e. PS-1171 (D. Accinelli, Huntsville, Alabama)

Fijiensis group: Three setaceous stomatal teeth, Spicule tips swollen, Bursa with 10 rays, peloderan tail (2° :3° = 4:4).

7. fijiensis n. sp., PS-1191 (W. Boorstein, Kioa Is., Fiji)