A new species of Nybelinia Poche, 1926, N. queenslandensis sp. n. (Cestoda: Trypanorhyncha) is described from sharks, Carcharhinus melanopterus (Quoy et Gaimard, 1824) from the coast of northeastern Queensland, Australia. Morphological features of the 46 known species of Nybelinia Poche, 1926 are tabulated and the new species is differentiated from all known taxa that are adequately described on the basis of having a homcomorphous armature, metabasal hooks 20-25 pm long, tentacles 0.07-0.09 mm in diameter, short bulbs (0.38-0.45 mm) and craspedote segments with the testes encircling the female genital complex. The fine structure of the scolex microtriches, frontal and rhynchodeal glands, tentacles and hooks, sheath and retractor muscle is described and compared with that of other trypanorhynchs.
It is shown experimentally that the option between developmental diapause and non-diapause development in nymphs of Ixodes scapularis Say, 1821 (Middle Atlantic population) is determined by photoperiodic conditions according to a two-step photoperiodic reaction of short-day long-day type. Diapause arrest of development is induced by an impact of either long day upon unfed nymphs, or short day upon engorged nymphs, while non-diapause development completed in 2-2.5 months at 20°C needs the change from short-day to long-day conditions. Some ecophysiological aspects of mechanisms controlling seasonal development of ticks belonging to Ixodes ricinus complex are discussed.
Unfed nymphs of Ixodes ricinus (L.) can be divided into two morphological groups according to the length of idioso-ma, scutum, hypostome and palpal segment III, and the number of dorsal alloscutal setae. Specimens of greater body dimensions and more numerous dorsal alloscutal setae moulted predominantly into females. The frequency of different nymphal length categories in field-collected ticks followed a normal distribution. The length of unfed nymphs correlates well with the length (r = 0.7248 ± 0.0711, P < 0.001) and weight (r = 0.6519 ± 0.0782, P < 0.001) of engorged nymphs, however, it varies in ticks of different origin. In field-collected ticks, freshly engorged female nymphs were 2.30-2.94 mm long, male nymphs 2.14-2.46 mm long. Feeding period (P < 0.05) and premoulting period (P < 0,001 ) were significantly longer in female nymphs both in field-collected and laboratory-derived I. ricinus. The engorgement weight was found to be the best criterion for differentiation of male and female nymphs of ixodid ticks. In field-collected nymphs engorged on BALB/c mice, 98.6 % of females moulted from nymphs weighting more than 3.60 mg, while in laboratory-derived ticks, 98.4 % of females emerged from nymphs of 3.42 mg body mass or more.