Abstract
Deladenus cocophilus n. sp. was isolated from infested coconut fruits in Winder, Balochistan, Pakistan. Descriptions are given of the entomophagous (insect-parasitic females) and mycetophagous (fungus-feeding) free-living females, males, and juveniles. The new species D. cocophilus resembles those species in which the excretory pore is situated anterior to the hemizonid, namely, D. apopkaetus Chitambar, 1991; D. leptosoma Gagarin, 2001; D. ipini Massey, 1974; D. laricis (Blinova and Korentchenko, 1986) Ebsarry, 1991; D. (siricidicola) canii Bedding, 1974; D. (s) imperialis Bedding, 1974; D. nevexii Bedding, 1974; D. (wilsoni) proximus Bedding, 1974; D. (s) rudyi Bedding, 1974; D. (s) siricidicola Bedding, 1968; D. (wilsoni) wilsoni Bedding, 1968 and D. minimus Chizhov and Sturhan, 1998. The new species differs from D. ipini in the absence of a post uterine sac vs. present; a = 17 to 30 vs. 35 to 40; stylet = 8 to 10 vs. 11 to 12 μm and vulva-anus = 21 to 28 vs. 35 to 48 μm. From D. apopkaetus it differs in tail length in female 22 to 28 vs. 31 to 43 μm and in the male it is 24 to 32 vs. 30 to 46 μm. It differs from D. leptosoma in the c ratio in females, c = 21 to 37 vs. 16 to 22, presence of 6 lines in lateral field vs. 10 lines and slightly longer spicules 16 to 18 vs. 15 to 16 μm. From D. laricis it differs in a shorter stylet length 8 to 10 vs. 11 to 12 μm; in the c ratio in males 16 to 22 vs. 22 to 35 and hemizonid from anterior end 76 to 90 vs. 90 to 119 μm. It also differs from the following species: D. (siricidicola) canii; D. (s) imperialis; D. nevexii; D. (wilsoni) proximus; D. (s) rudyi; D. (s) siricidicola; D. (wilsoni) wilsoni and D. minimus in having shorter tail length, lower values of a,b,c ratios and a slightly anteriorly located vulva in females.
Keywords: coconut, Deladenus cocophilus, Hexatylina, morphology, Nematoda, new species, Pakistan, taxonomy
Thorne erected the genus Deladenus in 1941 to accommodate those species not possessing a valvular median oesophageal bulb. He differentiated Deladenus from other genera by the location of oesophageal-intestinal junction immediately behind the nerve ring. Two generations, entomoparasitic and free–living mycetophagous, were reported by Bedding (1967). Blinova and Korenchenko (1986) erected the genus Beddingia for the species with known free-living and insect parasitic forms under the family Phaenopsitylenchidae. The genus Deladenus was transferred to the family Allantonematidae by Fortuner and Raski (1987). The genus Beddingia is a junior synonym of Deladenus by Chitambar (1991). Presently there are 22 recognized species that are widely distributed and described from different regions of the world (Chizhov and Sturhan, 1998; Andrassy, 2007). The genus is characterized by the cephalic framework eight-sectored, dorsal oesophageal gland large, and subventral glands reduced. Bursa and gubernaculum are present. The free-living generation feeds on fungi. The parasitic generation lives in the haemocoel of Hymenoptera of Siricidae and Ichneumonidae (Andrassy, 2007).
During a survey of plant parasitic nematodes, specimens of an undescribed species belonging to the genus Deladenus Thorne, 1941 were encountered from coconut fruit from the vicinity of Winder, Balochistan, Pakistan. Detail examination revealed the presence of a number of mycetophagous nematodes including females, males, and juveniles as well as infective females, which were identified as D. cocophilus n. sp. and is described and illustrated herein. D. pakistanensis is the only reported species of the genus Deladenus in Pakistan (Shahina & Maqbool, 1992).
Materials and Methods
Specimens were recovered from infected coconut fruits by Cobb’s sieving and decanting method followed by modified Baermann funnel method (Southey, 1986). The nematodes were gently heat killed, fixed in TAF, transferred to glycerin solution, allowed to dehydrate (Seinhorst, 1959), and permanently mounted in anhydrous glycerin. Observations of all nematode specimens were made using a light microscope. Measurements and illustrations were made using camera lucida attachment. For still photomicrography DS-L2 camera was used. Identification was made according to Siddiqi (2000).
Description
Deladenus cocophilus n. sp.
(Fig. 1, A–G; Fig. 2, A–H; Fig. 3, A–G)
Fig. 1.
Deladenus cocophilus n. sp.: A. Oesophageal region of mycetophagous female. B. Anterior region of mycetophagous female. C. Anterior region of mycetophagous male. D. Lateral field at mid body. E. Posterior region of mycetophagous female. F. Posterior region of mycetophagous male. G. Part of female gonad.
Fig. 2.
Deladenus cocophilus n. sp. Infective female: A. Oesophageal region. B. Anterior region. C. Excretory pore and hemizonid. D–F. Posterior region. G–H. Whole body.
Fig. 3.
Light micrographs of Deladenus cocophilus n. sp.: A. Anterior region of infective female arrow showing excretory pore and hemizonid. B. Posterior region of infective female. C. Anterior region of mycetophagous male. D. Posterior region of mycetophagous male. E. Anterior region of mycetophagous female. F. Female showing excretory pore and hemizonid. G. Posterior region of mycetophagous female. (Scale: A–G = 20 μm.)
Measurements: Morphometrics of the holotype, paratype, mycetophagous females, males, and infective females of Deladenus species are given in Table 1.
Table 1.
Morphometrics of mycetophagous females, males, and infective females of Deladenus cocophilus n. sp. (Measurements are in μm except L).
Comparative data: Comparative data of morphometrics of Deladenus species having excretory pore anterior to hemizonid, taken from the original descriptions, is given in Table 2.
Table 2.
Comparative data of morphometrics of Deladenus Thorne, 1941 species having excretory pore anterior to hemizonid.
Mycetophagous female: Body varied from vermiform, cylindrical to robust, swollen in young to old female, respectively. Cuticle finely annulated, annules 0.62 to 1.25 μm at midbody. Lip region low, hemispherical, lateral field with narrow band 5 to 8 μm wide, with six incisures occupying about one-third of the body width. Stylet basal knobs 2.4 μm wide × 0.8 to 1.6 μm high, stylet shaft slightly longer (4.8 μm) than spear cone (4 μm). The opening of the dorsal oesophageal gland is 0.8 to 1.2 μm behind the stylet base. Oesophagus corpus cylindrical, slightly swollen in midregion, median chamber absent. Oesophageal glands overlapping anterior end of intestine, subventral glands reduced, dorsal oesophageal gland elongate, gland nuclei distinct. Excretory pore sclerotized, present at 65.6 to 84 μm from the anterior end. Hemizonid 13.6 to 29 μm posterior to excretory pore, 3 to 5 μm long, posterior to nerve ring. Nerve ring 61.6 to 80.8 μm from anterior end. Ovary outstretched, oocytes arranged in a single row, vulval lips protuberant with sharply posterior constriction of the body. Vagina short muscular oblique, thick-walled. Post uterine sac absent. Tail conoid with narrowly rounded terminus, length equal to vulva-anus distance.
Male: Similar to female, slightly smaller; nerve ring 72 to 92 μm from anterior end. Excretory pore 60 to 74 μm from anterior end and located anterior to nerve ring. Hemizonid 3 to 4 μm long, 16 to 22.2 μm posterior to excretory pore. Testis outstretched, reaching beyond posterior end of oesophageal gland. Spicules and gubernaculum typically tylenchoid. Bursa smooth, terminal, extending from approximately 20 to 22 μm anterior of spicules to the tail terminus.
Infective female: Body cylindrical 0.5 to 0.6 μm long, 15 to 21 μm wide, cuticle with transverse striae about 1.2-μm wide at midbody. Lateral field occupying 20% to 40% of body width, with six incisure. Lips appear fused; amphid pouch larger than those of mycetophygous female. Stylet 19 to 22 μm long, with large distinct basal knobs at base, 6 to 7 μm and 2 to 3 μm high, very different from that of mycetophagous female and male, dorsal gland orifice more posterior 10 to 12 μm from the base of stylet knobs. Excretory pore and hemizonid 16 to 24 μm apart. Corpus cylindrical. Isthmus short and broad, dorsal oesophageal gland finely granular, extending posteriorly to ovary, dorsal gland nucleus prominent. Nerve ring 60 to 90 μm from anterior end. Vulva a narrow transverse slit, lip barely protuberant, ovary prodelphic oviduct normally packed with small spermatozoa (0.8 to 1 μm) occupying about half of the body length. Tail conoid, rectum narrow and straight.
Larvae: Stylet (8.8 to 9.6 μm) similar with that of mycetophagous female and male; hemizonid and excretory pore well-separated.
Differential diagnosis: Deladenus cocophilus n. sp. is similar to those species in which the excretory pore is situated anterior to hemizonid viz., D. apopkaetus Chitambar, 1991; D. leptosoma Gagarin, 2001; D. ipini Massey, 1974; D. laricis (Blinova and Korentchenko, 1986) Ebsarry, 1991; D. (siricidicola) canii Bedding, 1974; D. (s) imperialis Bedding, 1974; D. nevexii Bedding, 1974; D. (wilsoni) proximus Bedding, 1974; D. (s) rudyi Bedding, 1974; D. (s) siricidicola Bedding, 1968; D. (wilsoni) wilsoni Bedding, 1968; and D. minimus Chizhov and Sturhan, 1998. It differs from D. ipini in the absence of post uterine sac vs. present; a = 17 to 30 μm vs. 35 to 40μm; stylet = 8 to 10 μm vs. 11 to 12 μm; and vulva-anus = 21 to 28 μm vs. 35 to 48 μm. From D. apopkaetus it differs in tail length in female 22.4 to 28 μm vs. 31 to 43 μm and in male it is 24 to 32 μm vs. 30 to 46 μm.
It differs from D. leptosoma in c ratio in female, c = 21 to 37 vs. 16 to 22; in the presence of 6 lines in lateral field vs. 10 lines; and in slightly longer spicules 16 to 18 vs. 15 to 16 μm. It differs from D. laricis in shorter stylet length, 8 to 10 vs. 11 to 12 μm; in male c ratio 16 to 22 vs. 22 to 35; and in hemizonid from anterior end 76 to 90 μm vs. 90 to 119 μm. It also differs from the following species, namely, D.(siricidicola) canii; D.(s) imperialis; D. nevexii; D.(wilsoni) proximus; D.(s) rudyi; D.(s) siricidicola; D.(wilsoni) wilsoni and D. minimus in having shorter tail length, lower values of a,b,c ratios, and slightly anteriorly located vulva in females (Table 2).
Type host and locality: Specimens of all stages of both the life cycles (mycetophagous or free-living cycle and parasitic cycle) were recovered from infected coconut (Cocos nucifera L.) fruits from Winder, Balochistan, Pakistan.
Type specimens: Holotype (female) slide no. NNRC 120/1 and paratype slide no. NNRC 120/2-25 (50 females, 40 males, 17 juveniles, and 16 infective females) are deposited in the National Nematode Collection of NNRC, University of Karachi, Karachi-75270, Pakistan. Three females, three males, and three infected females on slide no. 120/26-28 deposited in the USDA Nematode Collection (USDANC) at Beltsville, MD. Two females, two males, and two infected females deposited in the Zoology Museum, Ghent University, Ghent, Belgium (slide no.120/29-31).
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