Redescription of Female Laelaps nuttalli Hirst, 1915 (Acari: Dermanyssoidea: Laelapidae) with Emphasis on Its Gnathosoma, Sense Organs and Pulvilli

The present scanning electron microscopic (SEM) study includes the redescription of female Laelaps nuttalli with emphasis on its gnathosoma and pulvilli which were rarely described in superfamily Dermanyssoidea. Chaetotaxy of dorsal shield revealed 40 pairs of setae, 22 on prosoma and 18 on opisthosoma. Epigynial plate carried 4 pairs of setae. Gnathosoma consisted of long basis capituli carrying median hypostome and 2 lateral pedipalps. Hypostome had dorsal labrum of 2 lobes covered with minute papillae, 2 lateral 3-segmented chelicerae, and ventral labium carrying 2 median lobes with laciniae and 2 lateral club-like lobes. Function of labrum papillae might be chemosensory while labium lobules might be mechanical, preventing solid material from entering the oral cavity. Palpal and foreleg tarsal organs comprised 10 and 15 sensilla, respectively. Sensilla of palpal organ were mostly chemoreceptors while those of tarsal organ were probably mechanoreceptors. Each pulvillus terminated with 2 medioventral claws and integumental folds beside longitudinal folds. 1. Introduction Acari are immensely important group of ectoparasites affecting human, animals, and plants. The mite, Laelaps nuttalli, occurs throughout the world as a parasite of the black rat Rattus rattus, the brown rat R. norvegicus and occasionally of other rodents and small mammals [1]. L. nuttalli received the attention of several authors since the mid-twentieth century. Studies on L. nuttalli were mainly concerned with surveys and host-parasite relationships [2–18]. Recently, L. nuttalli was also collected from bats in Malaysia [19]. Considerable literatures were encountered in the redescription of mite species with SEM [20–26]. SEM was also useful in describing certain parts of mites such as the gnathosoma [27–30], palpal organ [31, 32], and foreleg tarsal organ [32–34]. Description of L. nuttalli was only investigated with LM in the studies of Keegan [1] and Tipton [35]. The present SEM study proffers redescription of L. nuttalli with particular attention to the undescribed details of idiosoma, gnathosoma, peritreme, sense organs, and pulvilli. These structures were rarely described in superfamily Dermanyssoidea which includes 15 families; most of them are parasites and disease carriers. Of these families, species of Dermanyssidae, Laelapidae, and Macronyssidae are proven transmitters of diseases in birds, reptiles, and mammals including man [36]. Detailed morphology of the gnathosoma, peritreme, and pulvilli is an important step towards elucidation of the feeding behavior, respiration, and