PAPER SESSION I: BIOLOGY AND DIVERSITY OF THE ACARI

CHAIRPERSON: Dr. E.A. Ueckermann

PAPER 1

SOIL MITE (MESOSTIGMATA) FAUNA OF THE THAR DESERT OF RAJASTHAN

A.K. Bhattacharyya

Desert Regional Station, Zoological Survey of India, Jhalamand, Pali Road, Jodhpur 342 005, Rajasthan, India. E-mail: asitzsi@usa.net

The Thar Desert of India covers four Indian states viz., Rajasthan, Gujarat, Haryana and Punjab constituting nearly 10% land area of India. Taking into account the manifestation of aridity the focal point of the Thar Desert is restricted to Rajasthan accounting to 62% of the state. The soil mesostigmatid fauna of the region is extremely poorly known as evidenced from the fact that so far only two species (Eugmasus sp. and Macrocheles limue) have been reported. In an effort to explore the possibilities of occurrence of some more species the author carried out a preliminary study on a collection of soil mites collected from different places of the region. The study yielded two new records and two new species. Asca biswasi and Lasioseius parberlesei have been reported for the first time from this region. Both these two species were originally described from West Bengal. Two new species viz., Lasioseius rajasthanicus and Gamasellodes tusii show their similarities with Lasioseius indicus and Gamasellodes bicolor respectively.

PAPER 2

Ptyctimous mites (Acari, Oribatida) of Madagascar and other eastern African islands

W. Niedbała

Department of Animal Taxonomy and Ecology, Adam Mickiewicz University, Szamarzewskiego 91a, 608-569 Poznań, Poland, E-mail: niedbala@main.amu.edu.pl

In the island of Madagascar and a few neighbouring islands: Aldabra, Comoro, Mauritius, Reunion and the Seychelles, the number of hitherto found Ptyctima species is 57, including: 37 Phthiracaroidea, 18 Euphthiracaroidea, and 2 Mesoplophoroidea. Of those 57 species 30 are endemites (54.5 %), 10 Ethiopian species (17.5 %), 12 pantropical species  (21.0 %) 3 Oriental (5.3 %) and 2 semicosmopolitan (3.5 %). The endemism of Phthiracaroidea (62 %) is similar to Euphthiracaroidea (59 %). Similarity between the Ptyctima faunas of Madagascar and neighbouring islands is very small - only one or two species are common. Moreover, the fauna of Mauritius is completely different from that of Madagascar. The Ptyctima fauna of Madagascar and the near islands must have been shaped before separation of Madagascar from Africa, which is suggested by the presence of the phylogenetically eldest and the youngest genera of both Phthiracaroidea and Euphthiracaroidea.  On the other hand, a large number of species of late derived genera Notophthiracarus and Hoplophorella may indicate a relatively late colonisation of the islands by Phthiracaroidea. Dispersion of Ptyctima onto the Madagascar and neighbouring islands took place from the east - the Oriental region and south - the Australian region.

PAPER 3

PRESENT STATE OF KNOWLEDGE OF INDIAN ASCID MITES (ACARINA: MESOSTIGMATA) AND THEIR ZOOGEOGRAPHICAL DISTRIBUTION

A.K. Bhattacharyya

Desert Regional Station, Zoological Survey of India, Jhalamand, Pali Road, Jodhpur 342 005, Rajasthan, India. E-mail: asitzsi@usa.net

Ascid mites being highly specialised inhabit almost all the zoogeographical regions of the world. The global ascid fauna is represented by around 1000 species distributed over 34 genera. In spite of varied ecological nature, the Indian ascid fauna has failed to draw the proper attention of the ascidologists. So far, only 13 species were known from the Indian region. During a five-year long study the author studied Indian ascid mites and recorded 79 species belonging to 12 genera. Of the 12 genera so far encountered in India, six genera viz., Asca, Gamasellodes, Protogamasellus, Blattisocius, Lasioseius and Proctolaelaps are cosmopolitan in distribution occurring in both eastern and western hemispheres. The other six genera viz., Arctoseius, Xenoseius, Cheiroseius, Platyseius, Hoploseius and Antennoseius are discontinuously distributed. Out of 79 species, 44 species are endemic to the Indian region, 35 species are recorded from other zoogeographical regions. Among the recorded species only three viz., Asca aphidiodes (Linnaeus), Blattisocius dentriticus (Berlese) and Gamasellodes bicolor (Berlese) are truly cosmopolitan in distribution. India has 20 species in common with the Palaearctic region, 13 species with Nearctic, 9 species with Ethiopian, 8 species with Australian and 5 species with Neotropical. In further consideration it is noted that the species distribution of the Indian subregion show maximum similarity with the Indo-Chinese region (four species are common to both regions). The Indo-Malayan subregion shares two common species with the Indian subregion while no information about the Ceylonese ascid fauna is available to us. The similarity of the Indian ascid fauna with the Palaearctic region is due to the nearness of India with the Palaearctic region. The very low similarity between India and other zoogeographical regions in respect of distribution of ascid mites is difficult to interpret as insubstantial information is available on the ascid fauna of countries of the southern hemispheres encompassing South Africa, certain regions of southeast Asia, Australia and New Zealand. The information obtained from the study is not sufficient to establish a concrete trend regarding the zoogeographical distribution and abundance of the recorded species. Nevertheless, the study provides qualitative and quantitative data on the species richness and abundance from a previously little studied or unexplored area of India.

PAPER 4

MITES FROM MEXICAN OAKS CANOPIES

J.G. Palacios-Vargas, R. Iglesias & G. Castano

Lab. Ecología y Sistemática de Microartrópodos, Depto. Biología, Fac. Ciencias, UNAM, México, D.F. 04510, Mexico, E-mail: gcm@hp.fciencias.unam.mx

Mites are very small, but they occupy diverse biological niches. On trees, some are associated with suspended soils, while others live in epiphytic plants, moss, lichens, bark crevices or even on leaves and flowers. They are known to live in a diverse number of habitats, those free living are better represented in soil and litter, where they can have huge populations in a few square centimetres. Only recently they were collected in big numbers from tropical tree canopies, where they can be predators, scavengers, grazers, or associated with any animal or plant. The five localities of the oak species studied were at the states of Mexico (Cahuacán, Juchitepec, Villa del Carbón), Distrito Federal (Milpa Alta), and Hidalgo State (Santiaguito). All the foggings were individual trees and with triplicates. Foggings were employed to obtain the arthropods living on the canopy of the oak trees. Specimens were taken from two collections made by Tovar (1999) in February and August 1997. He used a natural pyrethrum in aqueous solution, to fog three isolated trees of each of six selected oak species (Quercus castanea, Q. crassifolia, Q. crassipes, Q. greegii, Q. laeta and Q. rugosa) and put 10 square spans (0.99 m² in surface) under each tree. All specimens were stored in 70% alcohol. Mites were sorted, counted and mounted in Hoyer’s solution, in order to identify the different taxa. The total amount of mites obtained with the two foggings was 6,256 specimens. Most of them (95%) were collected during the rainy season, and only about 5% during the dry season. The Mesostigmata were represented by 194 specimens, Prostigmata by 849 and the Cryptostigmata or Oribatids were by far the most abundant, with a total of 5,212 specimens. Only the 4% of the Oribatids were collected in the dry season and 96% during the rainy season. The oak species with most oribatid mites during the dry season were: Quercus crassipes (92), Q. castanea (35), Q. crassifolia and Q. rugosa (33), Q. laeta (13) and Q. greggii (9). The species with highest abundance during the rainy season were: Q. crassipes (2,094), Q. castanea (1,054), Q. laeta (979), Q. crassifolia (514), Q. rugosa (247), Q. greggii (235). The mite taxa we have found are represented by the following groups of Oribatid mites, Camisiidae: Camisia ca. segnis, Camisia sp.; Trhypochthoniidae: Trhypochthonius ca. tectorun; Liodidae: Platyliodes; Damaeidae: Belba sp.; Carabodidae: Carabodes sp., Tectocepheidae: Tectocepheus ca. elegans; Oppiidae: Striatoppia sp.; Cymbaeremaeidae: Scapheremaeus volcanicus, S. palaciosi; Oribatulidae: Zigoribatula sp.; Scheloribatidae: Cryptozetes usnea, Scheloribates sp.; Oripodidae: Oripoda ca. cubana, Parapirnodus ca. longus; Ceratozetidae: Ceratozetes sp.We present the inventory of the species found on each oak tree and the differences during the dry and rainy seasons.

PAPER 5

The functional micromorphology of the spiracles of the tortoise tick Amblyomma marmoreum.

E.D. Green¹, F.C. Clarke² & C. Baker³

¹Department of Anatomy, ²Dept. of Biology and ³Electron Microscope Unit, Medical University of Southern Africa, Box 139, Medunsa, 0204, South Africa. E-mail: clark@medunsa.ca.za

Spiracles in ticks control both respiratory gas exchange and tracheal water loss. The large size of the spiracles of A. marmoreum makes them suitable for morphological studies to investigate how the spiracles may control these processes. Larvae and nymphs were fixed directly in 70% ethanol. 50% of the flat and engorged adult ticks were euthanased in CO₂ in an attempt to cause the spiracles to open before fixation, while the remaining adults were fixed directly in 70% ethanol. Spiracles were carefully dissected and routinely processed for scanning electron microscopy (SEM) and viewed in a Leica Stereoscan 420 SEM at 5 to 7 kV. The external morphology revealed a spiracular plate with a porous comma-shaped outer margin perforated by many small aeropyles, surrounding a macula with a central ostium plugged by a valve-like lip. The spiracular plates of the nymphs and adults differed in size and shape of the macula and distribution of aeropyles. The interpedicellar space consists of a labyrinth of pedicels, which connect the spiracular plate to the thick base plate, which forms the floor of the subostial space. The pedicels are arranged in groups forming tubular chambers, many of which open to the atmosphere through the aeropyles. All chambers interconnect by means of slit-like fenestrations between the pedicles to allow respiration. The subostial space leads into the atrial chamber from which the main tracheal trunks arise. The thick lateral wall of the atrial chamber has a distinctive circular internal rim against which the thin medial wall may evert, to form a valve-like mechanism. This may close off the atrial chamber and trachea from the subostial chamber, and thus limit tracheal water loss through the open aeropyles when the spiracles are closed during interrespiratory intervals. The dense arrangement of pedicles and the closely spaced small aeropyles may further increase the resistance to transpiration and reduce the airflow, thereby reducing the water vapour loss from the spiracles.