Danamou Mounport

Observations On the Cuticle Ultrastructure in the Hoplolaiminae (Nemata: Hoplolaimidae)

The fine structure of the cuticle of Aorolaimus macbethi, Aphasmatylenchus straturatus, A. variabilis, Helicotylenchus dihystera, H. multicinctus, Hoplolaimus pararobustus, H. seinhorsti and Pararotylenchus hopperi is described. Six layers are identified in Aphasmatylenchus, Helicotylenchus and Pararotylenchus species vs seven in Hoplolaimus and Aorolaimus species. The ultrastructure of the five outer layers of the cuticle is identical in all species and consists of an external cortex, an internal cortex, a granular or fibrillar layer with electron dense ovoid structures, a striated layer and an electron dense fibrillar layer; the basal zone of the cuticle consists of a thin electron-lucent layer in Helicotylenchus and Pararotylenchus species and a thick electron-lucent layer representing half of the total thickness of the cuticle in Aphasmatylenchus species; in Hoplolaimus and Aorolaimus species, two layers are present: a thin electron-dense layer consisting of densely packed osmophilic corpuscules and a thick electron-lucent layer. Intracuticular canals previously described in other genera in the subfamily occur in all species studied and may be considered constant in Hoplolaiminae; observations on lateral fields in cross section reveal a variability of their shape and of the deepness of incisures. Three major groups in the subfamily may be distinguished based on ultrastructure and relative thickness of the layers of the cuticle: i) Hoplolaimus, Scutellonema and Aorolaimus, ii) Pararotylenchus and Helicotylenchus, iii) Aphasmatylenchus and Rotylenchus. Cuticle ultrastructure in Hoplolaiminae appears totally different from that observed in other taxonomic groups of the order Tylenchida.

Chronogaster tessellata n. sp. (Nematoda: Chronogastridae) from Senegal.

Chronogaster tessellata n. sp. is described from soil samples collected around roots of weed plants in the Saloum region, Senegal. It differs from all the species hitherto described by the presence of 40 longitudinal lines over the entire circumference of body giving the cuticle a tessellated appearance. The new species comes close to C. magnifica Andrassy, 1956 (20–24 longitudinal lines) but is less slender (a = 20–29.5 vs 29–44), with a shorter tail length (78–104 vs 114–147 μm), the radial tubules originating at 16.5–17.2 vs 19–21.5 μm posterior to base of mouth cavity. It can be separated from C. alata Gerlach, 1956 (18 longitudinal lines) by its shorter body length (0.63–0.77 vs 1.44 mm), smaller a and c′ ratios (20–29.5 vs 53 and 5.8–7.5 vs 17, respectively), and tail terminus with a mucro bearing four ventrally recurved prongs vs finely rounded in C. alata.

Laboratory culture of two Xiphinema americanum-group species (Nematoda: Longidoridae) from Senegal

Two Xiphinema americanum-group species from Senegal were successfully cultured on plants in the laboratory and the effects of host plant, temperature and soil moisture were evaluated. Soil temperature had most effect while soil moisture had no effect on multiplication. Greatest reproduction rates were observed for one species on Pennisetum typhoides (millet) and for the other species on Sorghum vulgare. These two gramineous species were better hosts than the legumes Vigna unguiculata (cowpea) and Arachis hypogaea (peanut). Multiplication was greater when plants were inoculated with freshly extracted nematodes.

Tem Observations On the Body Cuticle of Trichodoridae Thorne, 1935 (Nematoda: Enoplia)

Observations are reported on the fine structure of the cuticle of Paratrichodorus minor, P. nanus, P. rhodesiensis and Trichodorus eburneus. The ultrastructure of the cuticle was similar in Paratrichodorus and Trichodorus species; six layers were observed, the innermost layer consisting of three multilaminate units. The anatomy of the cuticle in Trichodorids was quite different from previous observations in other orders of Adenophorea. Two sets of intracuticular canals were observed as well as a peculiar type of junction between cuticle and somatic muscles. These results confirm previous studies on the anatomy of trichodorids and support the withdrawal of the family Trichodoridae from Dorylaimida. Siddiqis (1983) classification of the trichodorids under the order Triplonchida should be considered with attention.

Description of Paralongidorus dakarensis sp. n. with notes on P. bullatus Sharma & Siddiqi, 1990 from Senegal (Nematoda: Dorylaimida).

During a survey of plant-parasitic nematodes in the central regions of Senegal, a new species of Paralongidorus and seven populations of P. bullatus were collected. Paralongidorus dakarensis sp. n. is characterised by its small body size of 2.2-3.6 mm, hemispherical lip region, demarcated from body by a depression, funnel-shaped amphidial fovea and dorsally convex-conoid tail with a broadly rounded terminus. Paralongidorus dakarensis sp. n. closely resembles P. microlaimus and P. oryzae but differs from the former by shorter stylet (113-126 vs 125-136 μm), smaller c ratio (60-85 vs 85-150) and longer tail (35-49 vs 24-32 μm), and from the latter by longer stylet (113-126 vs 92 μm) and longer tail (35-49 vs 30 μm). Paralongidorus bullatus females from seven localities were measured and compared with the type population from Niger. Senegalese specimens were in general less slender and in some cases shorter or longer than those of the type population. Specimens originating from Tambacounda had a dorsally convex-conoid tail lacking the ventral curvature as described for the type population.

Scanning electron microscope observations on the Telotylenchinae Siddiqi, 1960 (Nematoda: Belonolaimidae)

Two species of the genus Trichotylenchus from the semi-arid region of West Africa, T. falciformis, type-species, and T. palustris, previously belonging to the genus Uliginotylenchus, were studied under the scanning electron microscope. Eight characters are common to both species: (i) head continuous with body contour; (ii) four to six cephalic annules present; (iii) first cephalic annule ovoid, laterally elongate and fused with the second cephalic annule at the level of the amphid; (iv) lateral cephalic sectors absent; (v) submedian cephalic sectors dorsally and ventrally fused; (vi) amphidial apertures elongate, ovoid and with longer axis obliquely dorso-ventrally directed; (vii) lateral fields areolated with three incisures; and (viii) spicules with an indentation or a small trapezoidal process on the dorsal side and a short rounded process on the lateral side, both being close to the distal extremity. The synonymy of Uliginotylenchus and Trichotylenchus is confirmed. The definition of Trichotylenchus is amended.