Female
genitalia as a taxonomic tool in the classification of Indian Acridoidea
(Orthoptera)
Mohammad Kamil Usmani 1& Hirdesh Kumar 2
1,2 Section of Entomology, Department
of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh 202002, India
Email: 1 usmanikamil94@gmail.com
(corresponding author), 2 entomologist1985@gmail.com
Date
of publication (online): 26 November 2011
Date
of publication (print): 26 November 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: Kailash Chandra
Manuscript
details:
Ms # o2589
Received 28
September 2010
Final received 04
August 2011
Finally accepted 02
November 2011
Citation: Usmani, M.K. & H. Kumar (2011). Female
genitalia as a taxonomic tool in the classification of Indian Acridoidea
(Orthoptera). Journal of Threatened Taxa3(11): 2207–2210.
Copyright: © Mohammad Kamil Usmani & Hirdesh Kumar 2011. Creative Commons Attribution 3.0 Unported License. JoTT
allows unrestricted use of this article in any medium for non-profit purposes,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Acknowledgements: We
wish to extend our gratitude to Department of Science & Technology, New
Delhi for providing financial assistance during the tenure of a major research
project (Ref. No. SR/SO/AS 32/2008) being carried out on
Biosystematics and Biodiversity of Acridoidea (Orthoptera) in northern India.Thanks are also due to Prof. Asif Ali Khan, Chairman, Department of Zoology,
Aligarh Muslim University, Aligarh for providing
necessary facilities.
Keywords: Acridoidea, female genitalia, Indian species,
Orthoptera, significance.
All the economically important species belonging to the
superfamily Acridoidea are commonly known as locusts and grasshoppers. Sometimes they are called Short-horned
Grasshoppers in contrast to Ensifera (Tettigonoidea and Grylloidea) or
Long-horned Grasshoppers which constitute one of the
other suborders of Orthoptera. Locusts and grasshoppers constitute an economically important group of
orthopterous pests that infest a number of cultivated and noncultivated crops. They cause considerable damage to agricultural
crops, pastures and forests and are well reputed for their destructiveness all
over the world. Locusts and
grasshoppers have invaded green crops from the earliest days to the present
time. Locusts are the main pests in countries bordering deserts. The devastations caused by migratory
swarms of locusts are well known. Swarms of the Desert Locusts Schistocerca gregaria have plagued agriculture
from ancient recorded times.
The accurate identification of the pest is the essential basis for
all investigations. Correct
identification and knowledge on the biology is very essential for evaluation of
the damage caused by the pests and also for developing suitable control
measures. Knowledge of the
biology, behaviour of a pest is fundamental to an understanding of its ecology
and population dynamics and to developing efficient control methods. Knowledge of the nature and causes of
pest damage is also essential in order to suggest the appropriate amount of research
and control efforts required. Experience has shown that control of agricultural pests is made easier
when their taxonomy and biological observations have been placed on a sound
basis.
The genitalic structures particularly epiphallus,aedeagus and spermatheca are less affected than the external characters by
environmental conditions. A
comparative study of these characters may therefore help to trace the
interrelationship of the groups more clearly than the external characters.
The genitalia of many animals, particularly arthropods, not only
show a great deal of structural detail but are also highly
species-specific. Genitalic
structures are most useful among the arthropods. In many group of insects genitalic structures are more
important for species diagnosis than any other character.
It has been suggested that a lock and key relationship exists as
regards the copulatory structures of the males and females of those species
with sclerotised genitalia. Such
appears the case in certain group of insects. In general, genitalic structures must be evaluated just like
other characters. In groups where
their significance has been proved they are usually very useful, because
genitalic structures appear to be among the first to change in the course of
speciation. Recently in 2009
Usmani studied the male and female genitalia in some Libyan species of
Acrididae.
The present study is based on the conventional as well as
genitalic characters, for a better understanding of the significance of
morphological structures. Comparative study has been done on genitalia with
reference to subgenital plate (Fig. 1a), ovipositor (Fig. 1b), spermatheca
(Fig. 1c) and supra-anal plate & cerci (Fig. 1d), of females.
Methods
Preparation for genitalic studies: For a detailed study of
the various components of genitalia, the apical part of female bodies was cut
off and boiled in 10% potassium hydroxide for a variable period till the
material became transparent (usually about 10 minutes) to remove unsclerotized
and non-chitinous tissues. They
were then thoroughly washed in tap water for complete removal of KOH and
examined in 70 percent ethyl alcohol on a cavity slide. Later, every specimen was dissected
under a binocular microscope with the help of fine needles to separate various
components viz., supra-anal plate and cerci, subgenital plate, ovipositor and
spermatheca. The normal process of
dehydration was adopted and clearing was done in clove oil. The genitalic structures were mounted
separately on cavity slides in Canada balsam. A 22mm square cover-glass over the
cavity of the slide was normally used when examining the supra-anal plate and
subgenital plate. This was made to
prevent them from curling upwards and inwards at the edges. The ovipositor was mounted in Canada
balsam on another cavity slide oriented to the required position without cover
glass. The slides were kept in a
slide drier at a temperature of approximately 400C for about one
week to get them completely dry.
The permanent slides were examined under the microscope in order
to make a detailed study of the genitalic structures.
Drawings were initially made with the help of a camera
lucida. Details were filled in by
conventional microscope examination.
Observations and
Results
For a better understanding of the significance of genitalic
structures, comparative study has been done on genitalia with reference to
subgenital plate, supra-anal plate & cerci, ovipositor and spermatheca of
females.
Female Genitalic
Structures
Subgenital plate (VIII
sternite) (Fig. 1a): The subgenital plate of the female is the VIII sternite and
therefore not homologous with that of the male. In the middle the surface has a
finger-like process, the egg-guide which extends
beyond the posterior margin of the plate between the bases of the lower
ovipositor valves is often concealed by them. On each side of the egg-guide there are sometimes found
brown sclerotised patches discovered by Jannone (1939) who regarded them as
sensory.
Rudimentary or well developed condition
of the egg-guide is taken as stable characters for separating various
families. The presence or absence
of Jannone’s organs and setae on the posterior margin of the female subgenital
plate are taken as subfamilial characters. Posterior margin is entirely setose in the subfamilies
Acridinae, Truxalinae and Oedipodinae; setae confined to posterior lateral
margins in the subfamilies Catantopinae, Coptacridinae, Cyrtacanthacridinae,
Eypreponemidinae and Calliptaminae; posterior margin without setae in Oxyinae
and Gomphocerinae, sometimes present in the latter subfamily. Shape of the posterior margin of
subgenital plate is suggested as a generic character. Length and shape of the egg-guide of the female subgenital
plate is considered as characters of specific significance. Flat or concave,
smooth or dentate condition of the ventral surface of the plate is used for
separating various species of the genus Oxya.
Ovipositor (Fig. 1b): It consists of three pairs
of valves, two of them large and conspicuous and the third (inner) concealed
between them. The ventral valve is
articulated with the subgenital plate and ends in a strongly sclerotised
hook. The dorsal valve is also
strongly sclerotised and with a hook-like tip. The inner valve is a small, moderately sclerotised
lobe. Basally, the valves are
articulated with a pair of long, parallel sclerotised apodemes, extending well
into the body cavity, to which are attached the main muscles of the ovipositor.
Long and slender or short and broad condition of
the ovipositor valves are taken as stable characters for separating
various subfamilies. Length of the
lateral apodeme in relation with the dorsal valve is regarded as a generic
character. The shape of valves and
apical tips are regarded as specific characters.
Spermatheca (Fig. 1c): The spermatheca is also
known as recepticulum seminis. It
is an essential part of the female reproductive system in which the spermatozoa
are stored, and they can be ejected upon eggs as the latter are passed from the
oviduct.
The spermatheca of Pamphagidae has a single apical diverticulum
although the same type occurs in other families (Pyrgomorphidae); while Acrididae as a family is characterised by a
spermatheca with two diverticula. Tubular or sac-like condition of pre-apical
diverticula of spermatheca is taken as stable characters for separating various
families. The long or short and
slender or broad condition of apical, tubular or sac-like
condition of pre-apical diverticula of spermatheca are suggested as
valid characters for grouping the subfamilies. Apical and preapical diverticula of spermatheca tubular in
the subfamilies Oxyinae, Hemiacridinae, Coptacridinae, Eyprepocnemidinae,
Tropidopolinae and Calliptaminae; apical diverticulum very long and slender,
preapical diverticulum tubular in Cyrtacanthacridinae, Catantopinae and
Romaleinae; apical divertidulum short or rudimentary, preapical diverticulum
sac-like in the subfamilies Acridinae, Truxalinae, Gomphocerinae and
Oedipodinae.
The size of apical and preapical diverticula and the presence or
absence of protuberance on preapical diverticulum is taken as specific
characters.
Female supra-plate and cerci (Fig. 1d): The X tergite, the
epipproct and the cercus in females are always of simple structure, even in the
species where these parts are highly specialised in the male sex but in some groups
there may be considerable variation in its shape and size. The shape of the female supra-anal
plate is suggested as a useful generic character. The shape and length of the female cerci are considered as
characters of specific significance.
Discussion
Earlier studies on the systematics of Indian Acridoidea are
exclusively based on conventional external visible characters, namely shape,
size, colouration, texture, number of antennal segments etc. A revolution in Acridoid systematics
was brought about by genitalic characters which has
resulted in a profound change in the systematic concept of this group. The
genitalic structures are less affected than the external characters by
environmental conditions. A
comparative study of these structures makes it possible to put forward some
suggestions regarding interrelations of families and subfamilies of Acridoidea
more clearly than the external characters.
Subfamilies Oxyinae, Hieroglyphinae, Catantopinae, Coptacridinae,
Cyrtacanthacridinae, Eyprepocnemidinae, Tropidopolinae, Calliptaminae and
Eremogryllinae are so closely related that earlier and recent workers have put
all of them in one group. In all the subfamilies apical and preapical
diverticula of spermatheca are tubular. The grouping is justified not only by the common
character of spermatheca but also by the fact that all the subfamilies
(of Catantopidae) possess prosternal process. The subfamilies Cyrtacanthacridinae, Calliptaminae and
Catantopinae are closely related in having spermatheca with long and slender
apical diverticulum, whereas in the subfamilies Eyprepocnemidinae and
Tropidopolinae, spermatheca with apical diverticulurn moderately long and
slender.
The spermatheca is with a single diverticulum in Pamphagidae while
in Pyrgomorphidae it is of variable forms, mostly with a single diverticulum,
sometimes with a small or large preapical diverticulum. In the family Acrididae, apical
diverticulum is short, rudimentary or sometimes absent and pre-apical
diverticulum is sac-like.
The sac-like condition of pre-apical diverticulum of spermatheca
is regarded as advanced characters. These occur in the subfamilies Acridinae, Oedipodinae, Truxalinae and
Gomphocerinae. The grouping of
these subfamilies into the family Acrididae is justified by the absence of
prosternal process. Gomphocerinae
is regarded as the most advanced subfamily among the group (Uvarov 1966).
REFERENCES
Jannone, G. (1939). Sulla diffusione della vescicola
ghiandolare protoracica negli Ortotteri della subfam. Oedipodinae. Bollettino di
Zoologia 10: 1–3 [35].
Usmani, M.K. (2009). Male and female genitalia in some Libyan Acrididae (Orthoptera:Acridoidea). Entomological
Research 39(2009): 1–35.
Uvarov, B.P. (1966). Grasshoppers and Locusts. A
Hand Book of General Acridology. Cambridge xi+481pp.