Systematic Comparison of Two Species of Genus Aeropus Gistel (Orthoptera: Gomphoceridae) from Mongolian Plateau

Subudao Eerdun1, Hai Si1, Rui-Lin Tian1,2*, Hua Mei1, Caicike Badumu1 and Ridunhu Hu1

1College of Life Science and Technology, Inner Mongolia Normal University, Hohhot 010022, China.

2Key Laboratory of Biodiversity conservation and Sustainable Utilization for College and University of Inner Mongolia Autonomous Region, Hohhot 010022, China.

Subudao Eerdun and Hai Si contributed equally to this study.

ABSTRACT

The review and summary of research history on Aeropus Gistel from Mongolian Plateau were carried out. Simultaneously, the comparative observation was conducted on the male genitalia and forewing veins between Aeropus sibiricus (Linnaeus, 1767) and Aeropus licenti (Chang, 1939) distributed in the Mongolian Plateau. Mongolian Plateau is the main distribution area for Aeropus Gistel, where significant differences exists in the morphological characteristics of Epiphallus and Phallic complex between Aeropus sibiricus and Aeropus licenti, which is the reliable basis for identifying the two species.

Article Information

Received 25 January 2022

Revised 12 May 2022

Accepted 01 June 2022

Available online 02 November 2022

(early access)

Published 13 December 2023

Authors’ Contribution

SE, HS and R-LT designed and planned the research, identified the specimens, analyzed the data and wrote the manuscript. HM, CB and RH contributed to the collection of specimens and analyzing the data.

Key words

Aeropus gistel, Mongolian plateau, Aeropus sibiricus, Aeropus

DOI: https://dx.doi.org/10.17582/journal.pjz/20220125030115

* Corresponding author: tianrl@imnu.edu.cn

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Copyright 2024 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Aeropus Gistel, 1848 is a genus established earlier in Gomphoceridae, Acridoidea, Orthoptera. In the 1930s, the British scholar Uvarov defined the differences between Aeropus Gistel, 1848 and Gomphocerus Thunberg, 1815. Three species in this genus were recorded, one of which included six subspecies (Uvarov, 1931). However, some scholars recorded the species of this genus into Gomphocerus Thunberg, 1815 (Kirby, 1910; Yin et al., 1995), and did not categorize Aeropus. At present, most scholars followed Uvarov’s system (Yin and Xia, 2002), and regarded Gomphocerus and Aeropus as the parallel genus of Gomphoceridae. Aeropus Gistel is a dominant species in alpine, subalpine grassland and forest grassland in Mongolian Plateau and its surrounding areas, especially Aeropus sibiricus Linnaeus,1767 being a plateau-sub-plateau indicator species in the Mongolian Plateau and its surrounding areas (He et al., 2017; Song et al., 2021). Therefore, the comprehensive understanding on the research history and taxonomic characteristics of Aeropus Gistel in the Mongolian Plateau has important significance for further and in-depth study on its plateau adaptation mechanism and species differentiation.

There are two species of Aeropus Gistel grasshoppers that are distributed in the Mongolian Plateau, including Aeropus sibiricus (L., 1767) and Aeropus licenti (Chang, 1939) (Supplementary Fig. 1). A. sibiricus belongs to Aeropus Gistel with its earliest record of existence found in the Mongolian Plateau. In 1925, Tarbinsky collected A. sibiricus from the Altai Mountains in Mongolia (Chang, 1939). In 1929, Bey-Bienko recorded distribution of A. sibiricus around Mandhe in Yakeshi of Hulunbuir, Inner Mongolia, China (Bey-Bienko, 1929).

In the early 20th century, Paul Emile Licent, a French naturalist and missionary, who was also the founder of the Tianjin Hoang Ho Pai Ho Museum at that time (Now Tianjin Nature Museum), began to collect the insect specimens in the Inner Mongolia and surrounding areas of the Mongolian Plateau from 1919. Chang (1939) from St. John’s University who was engaged in research at the Shanghai Zhendan Museum identified the orthopteran specimens collected by Paul Emile Licent. The specimens collected from Hahaye, Shanxi (recorded as Shansi: Hahaye at that time) by Paul Emile Licent in 1933 were regarded as a Holotype, which was identified as a new species and named after him as A. licenti. Whereas the specimens collected from Wudang Lamasery of Inner Mongolia (recorded as Mongolia: Outangtchao Pl. du Toumet at that time) in 1919 were regarded as Allotype (Chang, 1939). Therefore, Mongolian Plateau was not only the place to be considered as specimen production area of one species in Aeropus Gistel, but also the main distribution area of this genus. Until now, The Aeropus Gistel in Mongolian Plateau included the above two species (Chen, 2007; Yin and Xia, 2002; Yin et al., 1995).

It was found that there was no characteristic map given in the literature published for the new species of A. licenti, and the taxonomic characteristics of the two kinds of grasshopper given in various literatures were relatively scattered. In order to clarify the taxonomic characteristics of above both types, the comparative observations on major taxonomic characteristics, male genitalia and forewing veins were conducted in this study.

Materials and Methods

In this study, the specimens of A. sibiricus were collected from Xiao-jing-gou (111.8ºE, 41.1ºN), Da-qing-shan, Hohhot, Inner Mongolia, China and the specimens of A. licenti were collected from Ha-la-wu Bei-gou (105.9ºE, 38.9ºN), He-lan Mountain, Alxa League, Inner Mongolia, China (Fig. 1). All the specimens (male A. sibiricus: IMNU-En-Or63103 and male A. licenti: IMNU-En-Or63209) were archived in the Biological Herbarium of Inner Mongolia Normal University.

 

Anatomy of male genitalia

The abdominal end of male specimen was cut after softening. This was followed by the removal of the muscle and connective tissue. The epiphallus and phallic complex were isolated and stored in glycerol. Stereomicroscope LEICA S8APO was used to observe and photograph the epiphallus and phallic complex of genitalia. According to the observation results, the characteristic map of epiphallus and phallic complex were drawn. The digital stereomicroscope LEICA S8APO was applied to determine a total of seven measurable traits including the outer distance of apical ancorae in epiphallus, inner distance of basal ancorae, width of the bridge, outer distance of basal ancorae, height of ancorae, inner distance of lophi, outer distance of posterior projection (Zhang, 2009). The unit of length used for measurement was mm.

Characteristics of forewing veins

After softening, the wings of male specimens were spread, and the forewing veins were observed and photographed under stereomicroscope LEICA S8APO. The skeleton map of the forewing veins was drawn according to the observation results, and the length unit was mm.

Results

Male genitalia

The epiphallus in A. sibiricus presents bridge shape (Fig. 2A, B), with arched bridge (B). The top of ancorae (An) is sharp and slightly curved inward (Fig. 2B: B:2). The upward protrusion of anterior pro (Ant) is triangular (Fig. 2B, B: 3), and the posterior projection (Pp) has outward acute angle protrusion (Fig. 2, B: 5). The lophi (L) is divided into inner and outer lophi, the inner lophi is kidney shaped and the outer lophi is oval (Fig. 2B, B: 6).

The epiphallus of A. licenti presents bridge shape (Fig. 2B: C, D), the bridge (B) is arched. The top of ancorae (An) is sharp and curved inward (Fig. 2B, D: 2). The upward protrusion of anterior pro (Ant) is triangular (Fig. 2B, D: 3), and the protrusion of posterior projection (Pp) is slightly outward (Fig. 2, D: 5), which is not as significant as that of A. sibiricus. The lophi (L) is divided into inner and outer lophi, and the inner lophi being kidney shaped and outer lophi is crescent shaped (Fig. 2B, D: 6), while the outer lophi in A. sibiricus is oval (Fig. 2B, B: 6).

The detailed indexes of various parts of male genitalia are shown in Table I.

The basal valves of penis (Bp) in phallic complex of A. sibiricus (Fig. 3A, B) have been found in two pieces (Fig. 3, B: 1), which are presented in petal shape with sharp angular protrusions at the tip. Zygoma (Zy) are U shaped and reaches 1/2 of the basal valves of penis (Fig. 3, B: 3). The base of valves of cingulum (Vc) has a relatively-wide inverted U-shaped notch (Fig. 3, B: 4). The apical valves of penis (Ap) present sharp-spine shape, which are curved in the direction of zygoma with hook shape and divided into two valves respectively (Fig. 3, B: 5).

 

Table I. Measurement indexes of male genitalia of two species of Aeropus Gistel (Length Unit: mm).

Indicator	A. sibiricus	A. licenti
Width of bridge (Epiphallus)	0.52±0.04	0.58±0.09
Outer distance of apical ancorae (Epiphallus)	1.14±0.06	0.94±0.08
Outer distance of basal ancorae (Epiphallus)	1.26±0.06	1.31±0.05
Inner distance of basal ancorae (Epiphallus)	0.96±0.07	1.00±0.03
Height of ancorae (Epiphallus)	0.63±0.01	0.62±0.09
Inner distance of lophi (Epiphallus)	0.17±0.05	0.50±0.04
Outer distance of posterior projection (Epiphallus)	2.13±0.14	2.28±0.18

 

Note: Observed and measured specimens, n=4.

 

The basal valves of penis (Bp) in phallic complex of A. sibiricus (Fig. 3, C, D) are two pieces (Fig. 3, D: 1), which are presented as petal shape. Zygoma (Zy) are U shaped and reaches 2/3 of the basal valves of penis (Fig. 3, D: 3), while zygoma in A. sibiricus reaches 1/2 of the basal valves of penis. The base of valves of cingulum (Vc) has an inverted U-shaped notch (Fig. 3, D: 4), which is narrower than that of A. sibiricus (Fig. 3, B: 4). The apical valves of penis (Ap) are shown as sharp-spine shaped, which are curved in the direction of zygoma with hook shape and divided into two valves, respectively (Fig. 3, D: 5).

 

Characteristics of forewing veins

The fore wings of A. sibiricus exceeded the end of meropodium of metapedes. The anterior cubitus (CuA) and posterior cubitus (CuP) were partially or completely merged with each other (Fig. 4: B: 5, 6).

The fore wings of A. licenti reached the end of meropodium of metapedes. The base of precostal area in forewings was found to be significantly enlarged and the top was narrow. The full lengths of anterior cubitus (CuA) and posterior cubitus (CuP) were separated and not combined. The cubital area was found to be narrow and significant (Fig. 4, D:5, 6).

The medial areas of both species of grasshoppers were seen to be wide, lacking the intercalary media vein (IM) (Fig. 4: C, D).

Discussion

The precostal area in forewings of Gomphocerus Thunberg, 1815 has been found to be particularly long that exceeds the middle of wings, with a cubital area wider than the medial area (Uvarov, 1931). However, the precostal area in forewings of Aeropus Gistel, 1848 has been seen as relatively short and does not reach the middle of wings. The anterior cubitus (CuA) and posterior cubitus (CuP) have been reported to be very close to or overlap, thus making the cubital area extremely narrow (Fig. 4) which even disappears (Uvarov, 1931). In addition, the propodium tibia of male adults of Aeropus Gistel was found to expanded (Supplementary Fig. 1), however, Gomphocerus Thunberg lacks such characteristics. Therefore, the differences between Gomphocerus Thunberg and Aeropus Gistel have been found to be extremely significant, and should be identified as two independent genera.

 

Mongolia Plateau is the general name of the East Asian inland plateau area in Northeast Asia. It starts from the Greater Khingan in the east, ends at the Altai Moutains in the west, is bounded by the Sajan and Yablonovy Khrebet Mountains in the north, and bounded by Moni Mountains in the south. It is located in a vast area within the range of 87°40′-122°15′E and 37°46′-53°08′N with an average altitude of above 1580 m (Chen and Tian, 2001; Zhang, 2009). It includes the whole territory of Mongolia and Inner Mongolia autonomous region of China and its surrounding areas. Such a diverse ecological environment provides a special environment for insect diversity (Tian, 2020). The Mongolian Plateau and its surrounding areas are the main distributing areas for Aeropus Gistel.

The differences in the reliable and distinguishing features like phallic complex and epiphallus between A. sibiricus and A. licenti were found to be most significant (Table I, Fig. 2, 3). Differences have been marked in the characteristics of CuA and CuP in the forewing veins (Fig. 4), which might be more applied in the classification between genera.

Until now there are four species recorded in Aeropus Gistel, including A. kudia (Caudell, 1927), A. armeniacus (Uvarov, 1939), A. licenti (Chang, 1939) and A. sibiricus (L., 1767) (Yin and Xia, 2002). A. kudia is distributed in Siberia and Sakhalin in Russia. A. armeniacus is distributed in Armenia of Russia. A. licenti is distributed in Inner Mongolia, Shanxi as well as adjacent Ningxia, Gansu, Qinghai, Hebei and Shanxi in China. A. sibiricus is also seen as a widely distributed species. In the past, scholars considered that there were seven geographical subspecies according to the differences on the degree of swollen pronotum and distribution areas, including the A. sibiricus sibiricus in the western Siberia, A. sibiricus graecus (L.) in Greece, A. sibiricus hispanicus in central Spain, A. sibiricus pyrenaicus in Huesca of northern Spain, A. sibiricus helveticus in Switzerland, A. sibiricus caucasicus in Western Caucasus, and A. sibiricus tibetanus in Southeast Tibet, China (Uvarov, 1931; Chang, 1939; Yin et al., 1995). Some recent literatures considered that except for A. tibetanus Uvarov, 1935 (Yin and Xia, 2002) as the independent species, the other subspecies were all recorded as A. sibiricus (L., 1767). Therefore, there were differences in the morphological characteristics of A. sibiricus in different distribution areas. However, whether there are any differences on the physiological characteristics needs to be further studied.

According to the observation results on A. sibiricus in Da-qing-shan, Inner Mongolia in the recent years, both the propodium tibia and pronotum in nymph of A. sibiricus were not swollen. During the last molt before they become adults, the propodium tibia and pronotum of males were found to be swollen (unpublished data), but the specific reasons for expansion and the biological significance of swollen tibia and pronotum were not clear, which needs to be studied further.

The recorded species in Aeropus Gistel were all distributed in the areas above a certain altitude (Uvarov, 1931; Chang, 1939; Yin and Xia, 2002). Therefore, living at a high altitude is a feature of this genus. A. sibiricus and A. licenti were widely distributed in Mongolian Plateau, which provides indispensable materials for studying the species differentiation mechanism and plateau adaption characteristics in this genus.

ACKNOWLEDGEMENT

We are grateful to Professor Nonnaizab for helping us identify the specimens. This research was supported by the Natural Science Foundation of Inner Mongolia, China (No. 2020MS03016).

Supplementary material

There is supplementary material associated with this article. Access the material online at: https://dx.doi.org/10.17582/journal.pjz/20220125030115

Statement of conflict of interest

The authors have declared no conflict of interest.

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