View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Horizon / Pleins textes Fundam. appl. NemalOl., 1997,20 (4), 305-315 Description of Rhabditis (Caenorhabditis) drosophilae n. sp. and R. (C.) sonorae n. sp. (Nematoda: Rhabditida) from saguaro cactus rot in Arizona Karin KJONTKE Institut für Zoologie, AG Fvolutionsbiologie, FUBerlin, Konigin-Luise-Str. 1-3, 14195 Berlin, Gerrnany. Accepted for publication 14]uly 1996. SUDlDlary - Two gonochoristic species, RhabdiLis (CaenorhabdiLis) drosophilae n. sp. and R. (C.) sonome n. sp. are described from decaying saguaro cactus tissue in Arizona, USA. They are characterized by an anteriorly open bursa with a smooth edge; the spicule tips in both species are not pointed and are complex in shape. The dauerlarvae of R. drosophilae n. sp. are phoretic on the cactophilic fly Drosophila nigrospimcula. Arguments for the placement of both species in the subgenus CaenorhabdiLis of Rhabdilis, and a list of autapomorphic characters are presented, as weil as considerations on the colonization of cactus rot by Rhabditis (CaenorhabdiLis) species. RésUDlé - Description de Rhabditis (Caenorhabditis) drosophilae n. sp. et de R. (C.) sonorae n. sp. (Nernatoda: Rhabditida) associés aux racines du cactus" Saguaro " en Arizona - Description est donnée de deux espèces gonocho­ riques, RhabdiLis (Caenorhabdilis) drosophilae n. sp. et R. (C.) sonome n. sp., provenant de tissus de cactus" Saguaro " en décomposi­ tion en Arizona, États-Unis d'Amérique. Elles sont caractérisées par une bourse ouverte antérieurement et à marge lisse; chez les deux espèces, les spicules, de forme complexe, ne sont pas pointus. Les dauerlarvae de R. drosophilae n. sp. sont phorétiques sur la mouche Drosophila nigrospiracula associée aux cactus. Des arguments sont avancés pour J'inclusion de deux espèces dans le sous-genre CaenoThabditis du genre RhabdiLis; une liste de caractères autoapomorphiques est donnée, de même que des considéra­ tions sur la colonisation des racines de cactus par les espèces de Rhabditis (Caenorhabditis). Key-words : Arizona, Rhabditis (Caenorhabditis), saguaro cactus, SEM, Sonoran Desert, nematodes. Species of the subgenus Caenorhabditis Osche, 1952 Methods of Rhabditis Dujardin, 1845 are of particular interest since Rhabditis (Caenorhabditis) elegans Maupas, 1899 R. drosophilae n. sp. dauerlarvae were picked from became one of the model organisms for developmental their phoretic associates Drosophila nigirospiracula Pat­ and genetic research. In recent papers, the interest fo­ terson & Wheeler, 1942, and reared on agar plates ta cused also on comparative srudies of R. elegans and its which a smail piece of saguaro cactus tissue was added. relatives (Baird et al., 1992; Fitch & Emmons, 1995; R. sonorae n. sp. specimens were isolated from sagua­ Fitch et al., 1995; Sommer & Sternberg, 1995; Fitch & ro cactus rot. Both species were cultured on agar plates Thomas, 1997). With the exception of R. plieata Vblk, and saguaro cactus tissue. Heat relaxed or glutaralde­ 1950 (Sudhaus, 1974), ail species designated to the hyde fixed specimens from laboratory cultures were ex­ subgenus Caenorhabditis are morphologically very simi­ amined by light microscopy. Measurements were taken lar to R. elegans. In fact, most species are hardly dis­ with a compound research microscope equipped with a tinguishable. During a survey of the nematode fauna of camera lucida and a digitizing board. For scanning elec­ rotting saguaro cactus (Camegiea gigantea), two new tron microscopy (SEM) srudy, R. drosophilae n. sp. Rhabditis (Caenorhabditis) species have been discovered. adults and juveniles were picked from a laboratory cul­ These two species differ in sorne important features ture plate; dauerlarvae were removed from D. nigrospi­ from R. elegans and its presumed (Sudhaus, 1976; Fitch meula individuals. The nematodes were transferred to et al., 1995; Kiontke & Sudhaus, 1996; Sudhaus & cold 0.05 M phosphate buffered 2.5 %glutaraldehyde at Kiontke, 1996) closest relatives. They are described in pH 7.2 for 24 h. R. sonorae n. sp. specimens were fixed this paper. using cold 0.5 % glutaraldehyde in 0.05 M phosphate ISSN 1164-5571/96/07 $ 4.00/ © Gauthier-Villars - ORSTOM 305 K. Kionlke buffer. The specimens were washed in phosphate buff­ Each end of the slit covered with a broad cuticular flap. er, processed gradually to absolute ethanol, critical point Four dilator muscles attached to the vulva lips. Gonad dried using COz, mounted on stubs and sputter coated didelphic and dorsal1y reflexed, anterior branch right, with gold. Specimens were examined with a Philips posterior branch left of intestine. Unreflexed part of SEM 515. anterior branch of gonad 230-448 (342 ± 86) f..lm long, reflexed part measuring 113-236 (166 ± 43) f..lm. Unre­ flexed part of the posterior gonad measuring 247-428 Rhabditis (Caenorhabditis) drosophilae* n. sp. (342 ± 67) f..lm, reflexed part 78-217 (160 ± 48) f..lm long. =species 2 in Kiontke & Sudhaus, 1996; Thus, the reflexed part of the anterior branch ofthe gonad Sudhaus & Kiontke, 1996 represents 36-92 % of the length of the gonad (38-82 % (Figs 1,2) for the posterior branch). Posterior and anterior branch of almost the same length. Gonad, measured from ante­ MEASUREMENTS rior to posterior flexure, comprising 52-86 (61) % of See Table 1. body length. Oviduct forming a spermatheca containing large sperm cel1s of about 5 f..lm diam. Sphincter present DESCRIPTION between spermatheca and uterus. Four to eighteen de­ veloping eggs present in uteri, sometimes also up to Adults: Cuticle about 1 f..lm thick, smooth, with faint annules, which are not visible on lateral field. Three eight hatched juveniles. Eggs measuring 48-52 lateral ridges extending posteriorly to a point about (50 ± 1) f..lm x 26-31 (27 ± 2) f..lm (n =6). Rectum 18­ 75 f..lm anterior to anus. Deirids situated in the dorsal­ 25 (22 ± 2) f..lm long. Tail elongate with filiform tip. most ridge. Lips closed; each lip with one inner labial Phasmid openings 38-58 (50 ± 6) f..lm or 1.7-2.5 times sensillum in both sexes. Lip region sexually dimorphic : ABW behind anus, at 36-53 (44) % of taillength. males with prominent cephalic sensilla on the subdorsal Males: Testis right of intestine, comprising 54-70 and subventrallips at the level of the amphids; females (62) % of body length; ventral1y reflexed part 73-105 without cephalic sensilla. Amphid openings at the base (141 ± 20) f..lm long, that is 19-34 (25) % of gonad of the laterallips, not visible with light microscope. Each length. Bursa anteriorly open and peloderan with nine lip with a semicircular flap projecting inta the mouth pairs of bursal papil1ae. Arrangement of papil1ae 21 cavity. Length of buccal cavity averaging 4.3 times its 1 + 3 + 3. Tips of papil1a 1, 4, and 7 attached to the width in females and males. Buccal cavity comprising dorsal surface of bursal velum, tips of papil1ae 2, 5 and 8 9-11 % of the pharynx length in both sexes. Pharyngeal attached to the ventral surface, papil1ae 3 and 9 extend­ collar 10-13 (12 ± 1) f..lm, enveloping 55-70 % of buccal ing to the bursa edge, papilla 6 thicker than others, cavity. Metarhabdions isomorphic and isotopic each slightly bottle shaped and embedded in the velum with­ with one triangular tooth projecting into the mouth cav­ out reaching the edge. Bursa edge smooth. Phasmids ity. Corpus 94-114 (104 ± 6) f..lm, comprising 52-57 % (visible on SEM images) situated at the base ofpapilla 9. of pharynx length. Width of median bulb 20-27 Precloacal sensillum on roundish knob with a bulgy bas­ (24 ±2) f..lm in females and 18-23 (21 ± 1) f..lm in males, ai anterior edge. Subventral postcloacal sensilla filiform. almost as wide as terminal bulb measuring 22-30 Spicules separate, slightly curved with notched tip, dor­ (26 ± 2) f..lm in females and 21-27 (23 ± 2) f..lm in males. solateral part very thin like a velum; proximal part sep­ Terminal bulb with duplex haustrulum posterior ta the arated from the distal part by a fine line or seam. Gu­ valvular apparatus. Cardia present and prominent. Cer­ bernaculum slender and curved; 74-88 (81) % of vical (" excretory ") pore 128-193 (151 ± 17) f..lm from spicule length, its lateral edges partly folded ventraIly. anterior end at 68-91 % of pharynx length. Deirids, Rectum 30 ± 1 f..lm long on average. " posterior deirids ", and lateral channel conspicuous in glutaraldehyde fixed specimens. Deirids 136-213 Second-stage Juveniles: Second-stage juveniles 02) (163 ± 21) f..lm behind the anterior end, at 78-127 % of preparing to become dauerlarvae storing lipids as oil pharynx length, thus in many cases posterior ta cervical draplets in their intestine as weil as in the hypodermis. pore. "Posterior deirids" visible in sorne glutaralde­ As in other juvenile stages except dauerlarvae, no lateral hyde fixed specimens, in females 225-350 f..lm, in males ridges present on lateral field. Mouth open. Amphid 147-193 f..lm anterior to anus or cloaca, at about 75 % of openings inconspicuous. Pharynx with wel1 developed body length. median and terminal bulbs, their width 11-13 f..lm and 12-15 f..lm. Distance between anterior end and cervical Females: Vulva a transverse slit, the cuticle on both pore 74-102 (90 ± 9) f..lm, corresponding to 63-88 sides of the vulval opening with ridge-like sculptures. (78) % of pharynx length. Genital primordium oval in shape, 9-18 f..lm .Iong, at about 50 % of body length. Rectum length 13-17 (15 ± 1) f..lm. Tail with filiform tip. Phasmids 21-28 (24±2) f..lm or 1.6-2.1 ABW be­ * Named from the phoretic associate Drosophila nigrospiracula. hind anus. 306 Fundam. appl. Nemalol. Two new Rhabditis Table 1. Measurements (in /Lm) of hem relaxed living specimens of Rhabditis (Caenorhabditis) drosophilae n.