Females, second generation: Similar to first generation females, except following characters: smaller size, slender body, tail straight and longer than width at anus, with minute spine.
Males, first generation: Cuticle, lip region, stoma and esophageal region as in first generation females. Body much smaller than females. Testis single reflexed. Spicules paired, well curved, spicule head truncate or rounded (FIG.SEM). Shaft very short, or indistinct. Blade wide anteriorly, tapering posteriorly to a blunt tip. Spicule tip usually slightly curved or with a notch dorsally. Velum prominent but short, not covering spicule tip. In ventral view, gubernaculum tapering anteriorly to form a neck then enlarging slightly to a ventrally curved end. In lateral view, bow-shaped, constricted at posterior part to round proximal portion. Two ventral preanal papillae and twelve pairs of genital papillae located as follows: one ventral papilla adanal, the other far distant from anal opening; pre-anal eight pairs in subventral line, three above cloaca and a row of five pairs up the body; in subventral position post-anal two pairs subterminal, one subdorsal on distal half of tail and one subdorsal slightly anterior to anus. Tail conical, tapering to rounded body terminus. Bursa absent.
Measurements(n=20): Length= 1400 micrometers (um) (1200-1900); greatest width=97 um (75-156); distance from head to excretory pore=84 um (71-105); distance from head to nerve ring=129 um (120-137); esophagus length=167 um (156-189); length of tail=33 um (30-40); width at cloaca 42 um (36-54); length of spicules=63 um (48-72); length of gubernaculum=44 um (39-60); ratio, D%=51 (42-59), SW=1.50 (After Mamiya, 1988).
Males, second generation: Similar to first generation males but differing by following characters: smaller size, slender body, tail with minute spine.
Infective juveniles: Body slender, gradually tapering posteriorly, generally ensheathed in cuticle of second stage juveniles. Lip region not set off. Lateral fields distinct. Mouth opening closed. Esophagus long and narrow, terminating in basal bulb, weak and less prominent than in adults. Excretory pore at level of mid esophagus. Excretory glands displacing basal bulb and anterior end of intestine. Nerve ring distinct, anterior to basal bulb. Hemizonid at level of nerve ring. Cardia distinct. Bacterial pouch in anterior portion of intestine. Intestine dense, and dark in appearance. Tail conical with pointed terminus.
Measurements (n=50): Length=589 um (524-662); greatest width= 26 um (22-31); distance from head to excretory pore=46 um (42-50); distance from head to nerve ring=76 um (70-84); esophagus length=111 um (106-120); length of tail=50 um (44-59); length of bacterial pouch=21um (17-24); a=22.5 (19.3-25.2); b=5.3 (4.9-5.9); c= 11.7 (9.9-12.9); D%=41 (38-44).
Type locality: Hamakita, Shizuoka Prefecture, Japan. No type host; nematodes were recovered from soil using scarabaeid beetle larvae (Anomala cuprea) as bait.
Type specimens: Holotype (male) and allotype (female) deposited in the nematology collection at Forestry and Forest Products Research Institute, lbaraki, Japan. Paratypes deposited at the Herbarium and Insect Museum of the National Institute of Agro-Environmental Sciences, Tsukuba, lbaraki, Japan; USDA Nematode Collection, Beltsville, Maryland, U.S.A.; Nematode Survey Collection, University of California, Davis, California, U.S.A.; and Commonwealth Institute of Parasitology, Harpenclen, Herts, England.
Diagnosis: Seinernema kushidai is closely related to S.carpocapsae and S. intermedium (Neoableclana intermedia Poinar, 1985). It can be separated from the latter two species by the location of the excretory pore of all stages, shape of spicules, gubernaculum of adult males, and the body length of infective juveniles. The body length of infective juveniles of S. kushidai is distinctly smaller than S. intermedium and slightly longer than S. carpocapsae. The excretory pore of infective juveniles of S. kushidai (ratio, EP/Esophagus=0.38-0.44) is located more anteriorly than in S. intermedium (ratio, EP/esophagus=0.48-0.58) and more posteriorly than in S.carpocapsae (ratio, EP/esophagus=0.23-0.28). The gubernaculum or the first and second generation males of S. kushidai is recognizably different from that of S.carpocapsae and S. intermedium. In lateral view, the round proximal portion is separated from the other part by constriction, giving a shape distinguishing it from the other two species. The gubernaculurn of S. carpocapsae is narrow with an indistinctly constricted proximal portion, and that of S. intermedium is typically bowshaped overall in lateral view. The spicules of S. kushidai lack color and have a smoothly rounded manubrium, while those of S. carpocapsae are yellow and have an angular manubrium. The bacterial pouch in the infective juveniles of S.kushidai is smaller than that of S. intermedium (27-48 um). The upper range of pouch length in S. kushidai does not overlap with the lower end of that in S. intermedium. The length of infective juveniles of S. kushidai is smaller than S. kraussei, S. feltiae and S. glaseri, and longer than S. rarum.
Bionomics:Life cycle: Infective juveniles of S. kushidai were capable of invading and killing larvae of both scarabaeid species, H. picea and A. cuprea and caused 100% mortality for both insect species. Average days of host death were 5.0 for 20 larvae of H. picea and 5.2 for 14 larvae of A. cuprea after exposure to the nematode. The infective juveniles started to develop in the host just after the host's death, irrespecitve of days required to kill insect hosts. The life cycle of S. kushidai is similar to that of other steinernematid nematodes. Exsheathment of infective juveniles after entering the host occurred somewhat later than did other steinernematids. Subsequent host death was delayed more than 3 days in comparison with that caused by other nematodes. In case of S. carpocapsae, the host generally dies within 48 hours after the entrance of infective juveniles. Exsheathed juveniles continued to develop into large first generation adults, mated, and deposited many eggs. Eggs and hatched juveniles appeared within 3 days of host death and occasionally developed to second generation adults during the following 2-4 days. In most cases, the first generation adults produced infective juveniles which appeared in the insect cadavers 5 days after the host's death. At this time, parasitic juveniles, probably 2nd stage juveniles with almost uniform size, outnumbered infective juveniles in the cadavers. Proportion of infective juveniles to total number of juveniles gradually increased and reached nearly 100% 9 days after host death. Even when the second generation adults were produced, most infective juveniles seemed to develop from eggs deposited by the first generation adult females, because the numbers of second generation adults were few, if any, and they existed concurrently with infective juveniles. Sometimes the eggs hatched in the body of first generation adults and developed to infective juveniles within the body. Average number of infective juveniles produced per each cadaver of H. picea was about 50,800 (n=10).
REFERENCE
Mamiya, Y. 1988. Steinernema kushidai n.
sp. (Nematoda: Steinernematidae) associated
with scarabaeid beetle larvae from Shizuoca,
Japan. Applied Entomology and Zoology
23:313-320.
This document was constructed and is maintained by KHUONG
B. NGUYEN
Entomology & Nematology Department
University of Florida