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Article Category: Research Article
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Online Publication Date: 08 Mar 2025

Description of Gamasellus onitiae sp. nov. (Ologamasidae: Mesostigmata) from Dung Beetle, Onitis philemon (Coleoptera: Scarabaeidae)1

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Page Range: 269 – 275
DOI: 10.18474/JES24-21
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Abstract

Gamasellus onitiae sp. nov. (Ologamasidae: Mesostigmata) has been identified and described after being been collected from a dung beetle, Onitis philemon (Scarabaeidae, Coleoptera), in India. The specimen was found to be attached via a claw to the head region of the beetle. The mite–beetle association appeared to be phoretic. The distal setae, ventral setae, sternal shield length, and peritreme of G. onitiae sp. nov. differ from those of the closely related Gamasellus falciger (G. Canestrini & R. Canestrini), Gamasellus deepdelensis (Ryke), Gamasellus racovitzai (Jumeau and Usher), and Gamasellus bellavistae Emberson.

Keywords: dung beetle; head region; claw; distal setae; peritreme

More than 60 species have been classified under the genus Gamasellus Berlese, which is a member of the family Ologamasidae (order Mesostigmata). Important characters of the Gamasellus genus are: (a) the dorsal shield will enfold the ventral surface without combining with ventrianal shield; (b) the setae of the legs can be simple or complex; (c) it is ubiquitous in nature, as noted by Pérez-Martínez et al. (2019); and (d) it has a phoretic relationship with insects, attaching to the host wings (Camerik 2010, Farish and Axtell 1971). Szymkowiak et al. (2007) postulated that the phoretic behavior enhances survival as well as expands its geographic distribution. Perotti et al. (2010) also reported that phoretic attachment is often facilitated by specialized structures for attachment to the host insect. Usher and Bowring (1984) observed that Gamasellus racovitzai (Jumeau and Usher) is a terrestrial predator and is distributed in various habitats with mossy places. It is apparent that there are several species in this genus that remain undescribed; this study was conducted with a heretofore undescribed species in Tamil Nadu, India.

Materials and Methods

The host insect, a dung beetle identified as Onitis philemon (Scarabaeidae, Coleoptera), was collected from Tamil Nadu. An examination revealed that a mite was attached to the head region of the dung beetle. The attachment was facilitated by a strongly inclined tarsal claw. The mite specimen was cleared and the slide mounted for examination and taxonomic identification using Krantz (1968). Drawings were rendered with camera lucida, and the measurements are in micrometers. Voucher slides have been retained in the collection curated by V.R. in the Department of Entomology, Acarology Laboratory, Tamil Nadu Agricultural University, Coimbatore, India.

Results and Discussion

Ten dung beetles with 10 to 15 mites attached to the ventrum of the head region were collected and provided mite specimens for this study. Ten mite slides (one mite specimen mounted per beetle) were prepared for microscopic observation as well as taxonomic drawings. The chaetotaxy measurements from the 10 mites are listed in Table 1. The slide-mounted mite specimens were identified to the genus Gamasellus, but the species could not be confirmed. It was, thus, deemed to be an undescribed species of Gamasellus. The description of the species is given below.

Table 1.Chaetotaxy measurements of Gamasellus onitiae sp. nov.
Table 1.

Taxonomic Description

Genus: Gamasellus Berlese, 1892Gamasellus onitiae sp. nov. (Figs. 1–5)

Male dorsum

Idiosoma 810 long and 580 wide; 27 pairs of setae arise from the dorsum and length ranges from 25 to 115. The arrangement and chaetotaxy of dorsal setae are shown in Fig. 1. Ornamentation is represented as sparse dots on the figure. The setae are smooth and long; setae S5 are longer than other setae (180) (Table 1).

Fig. 1.Fig. 1.Fig. 1.
Fig. 1.Dorsum of Gamasellus onitiae sp. nov.

Citation: Journal of Entomological Science 60, 2; 10.18474/JES24-21

Fig. 2.Fig. 2.Fig. 2.
Fig. 2.Ventrum of Gamasellus onitiae sp. nov.

Citation: Journal of Entomological Science 60, 2; 10.18474/JES24-21

Fig. 3.Fig. 3.Fig. 3.
Fig. 3.Legs I, II of Gamasellus onitiae sp. nov.

Citation: Journal of Entomological Science 60, 2; 10.18474/JES24-21

Fig. 4.Fig. 4.Fig. 4.
Fig. 4.Legs III, IV of Gamasellus onitiae sp. nov.

Citation: Journal of Entomological Science 60, 2; 10.18474/JES24-21

Fig. 5.Fig. 5.Fig. 5.
Fig. 5.Gnathosoma of Gamasellus onitiae sp. nov.

Citation: Journal of Entomological Science 60, 2; 10.18474/JES24-21

Venter

Sternal shield narrow, well developed, 375 long, 200 wide, with five pairs of setae 55, 65, 55, 50, and 70 long from anterior to posterior. First and third setae are equal in length. The sternal shield is larger in outline and subequal in length and width. In addition, the genital shield is 115 long and 120 wide (Table 1), with two paranal setae and an adanal seta (Fig. 2). Two pairs of setae arise between the sternal and genital shields; two and one pairs of setae arise on the anterior and lateral sides of the sternal shield, respectively. Nine pairs of setae are located at the lateral side of the genital shield. The peritreme lies at the anterior portion of coxa IV.

Legs

A pretarsus and a claw were observed at the terminus of each of the legs. Legs I to IV measure 700, 595, 670, and 745 long, respectively. All legs possessed well-developed claws and pulvilli, and the setal pattern was simple.

Leg chaetotaxy

Coxae, 0-0-0-0; trochanter, 10-6-6-7; femora, 7-10-9-6; genua, 8-9-3-2; tibia, 7-3-0-2; and tarsi 19-8-7-7.

Gnathosoma

Gnathosoma 340 long and 200 wide (Table 1). The chelicerae are chelate and dentate. The tritosternum bifid. Two pairs of setae are on the chelicerae (25).

Types

A holotype male marked on the slide, INDIA: Tamil Nadu, Ramanatham, Cuddalore, 03.X.2005. Egg: Onitis philemon (Scarabaeidae: Coleoptera), Coll: R. Vaithiyanathan, (No: 117/1). Three paratype slides, collection data same as type.

Diagnosis

This new species resembles Gamasellus claudiae Walter; however, the two species were found to differ in the following characters:

  • Sternal shields differ in length and width.

  • Sternal shield setae were same in both species.

  • The new species contains two paranal setae and an adanal seta on the genital shield, in contrast to G. claudiae, which possesses six pairs of setae, excluding paranal and adanal setae.

The other differential characters are tabulated in Table 2.

Table 2.Comparision of Gamasellus onitiae sp. nov. with related species.
Table 2.

Relationship to the host

Orange-colored mites found attached to the ventrum of head region of the beetle. Mites attach to the beetle body by means of tarsal claws.

Etymology

The mite species is named after the type host genus.

References Cited

  • Camerik, A.M. 2010.
    Phoresy revisited, Pg. 333–336
    . In Sabelis, M. and Bruin J. (eds.), Trends in Acarology.
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    Dordrecht, The Netherlands
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  • Farish, D.J. and Axtell R.C. 1971. Phoresy redefined and examined in Macrocheles muscaedomesticae (Acarina: Marcochelidae). Acarologia 13: 16–29.
  • Krantz, G.W. 1968. A Manual of Acarology,
    2nd ed
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    Oregon State Univ
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    Corvallis
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  • Perotti, M.A., Braig H.R. and Goff M.L. 2010.
    Phoretic mites and carcasses: Acari transported by organisms associated with animal and human decomposition, Pg. 69–92
    . In Amendt, J., C.P. Campobasso, Grassberger M. and Goff M.L. (eds.), Current Concepts in Forensic Entomology.
    Springer
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    New York, NY
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  • Pérez-Martínez, S., Lourdes Moraza M. and Saloña-Bordas M.I. 2019. Gamasina mites (Acari: Mesostigmata) associated with animal remains in the Mediterranean region of Navarra (Northern Spain). Insects 10(
    1
    ): 5.
  • Szymkowiak, P., Górski G. and Bajerlein D. 2007. Passive dispersal in arachnids. Biol. Lett. 44: 75–101.
  • Usher, M. and Bowring M.F.B. 1984. Laboratory studies of predation by the Antarctic mite Gamasellus racvitzai (Acarina: Mesostigmata). Oecologia 62: 245–249.
Fig. 1.
Fig. 1.

Dorsum of Gamasellus onitiae sp. nov.

Fig. 2.
Fig. 2.

Ventrum of Gamasellus onitiae sp. nov.

Fig. 3.
Fig. 3.

Legs I, II of Gamasellus onitiae sp. nov.

Fig. 4.
Fig. 4.

Legs III, IV of Gamasellus onitiae sp. nov.

Fig. 5.
Fig. 5.

Gnathosoma of Gamasellus onitiae sp. nov.

Contributor Notes

2Corresponding author: S. Vijay (email: entovijay@gmail.com).
3Rice Research Station, Ambasamudram–627 401, India.
4Department of Entomology, Tamil Nadu Agricultural University, Coimbatore–641 003, India.
5Krishi Vigyan Kendra, Sandhiyur–636 203.
6Regional Research Station, Vriddhachalam–606 001, India.
7Tamil Nadu Agricultural University (retired), Coimbatore–641 003, India.
Received: 22 Feb 2024
Accepted: 09 Mar 2024
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