Hislopia Journal 10 (1) 2017 ISSN: 0976-2124 99-103 MOUTHPARTS SENSILLA OF THE WORKER ANT LEPTOGENYS DENTILOBIS (HYMENOPTERA: FORMICIDAE) D. D. BARSAGADE, M. P. THAKRE, J. R. KIRSAN, S. B. NAGOSE, D. A. NAGARKAR & A. M. BODELE PGTD Zoology, MJF Educational Campus, RTM Nagpur University, Nagpur (MS), INDIA Corresponding author: [email protected] Abstract: The mouthparts of the worker cast in the ant, Leptogenys dentilobis are directed forward and adopted for biting and cutting type. The mouth parts consist of broad lobulated labrum, mandible with sclerotized incisors and molar cups, palped laterally placed maxillae, and the labium which forms the lower lip. Scanning electron microscopic (SEM) studies of the mouthparts revealed the presence of two major types of sensilla. i.e. sensilla trichoidea and sensilla trichoidea curvata. These sensillae though present in all the mouth parts, exhibit variation in their morphology, density and number and are site specific. Keywords: mouth parts, SEM, sensilla, Leptogenys dentilobis. Introduction The genus, Leptogenys mandibular elongated masticatory dentilobis, has attracted attention margin with noticeable sharp due to its wide variety of social pointed curved apical and pre- organization and colony structure apical teeth and a prominent basal as well as its remarkably diverse angle (CAPINERA, 2008). In the range of behaviors. In ants the adult ants the mouth parts are mouth parts consists of pair of equipped with mechano and mandibles, maxilla and labium. chemoreceptors (GOTWALD, 1969; The labium is formed due to fusion WHEELER & WHEELER, 1970; of paired structure the second pair PAUL et al., 2002). Mandible is of maxillae (RICHARDS & DAVIS, modified as defensive organ and 1987). All ants are mandibulated also in-charge the protection of and the range of mandibular their nest. In ants the worker caste activities are extended to nest play major role in colony nest construction and defense of the construction and the mandibles colony, cut and transport of food are directly related to the ants diet debris and transport of larvae and (CAPINERA, 2008). eggs (WHEELER & WHEELER, The SEM studies revealed 1970). They are strongly chitinized the presence of several mechano structure commonly known as jaw as well as chemoreceptors on the and always articulate in transverse surface of mouthparts of ant. The plane. Ants consist a triangular sensilla present on the mouthparts BARSAGADE et al. help in detection of pray in many (JSM 6380A) at the SEM centre of ants (KAISSLING 1976; Visvesvaraya National Institute of BARSAGADE et al., 2013; Technology, Nagpur, India. GATHALKAR & BARSAGADE, 2016). No major attempts have Statistical Analysis: been undertaken to study the Sensillae on mouthpart mouth part sensilla of L. dentilobis. were measured, identified and The present paper describes the counted amongst worker ultrastructure of the mouthparts individuals. Measurements were with special reference to the taken from individuals and the sensillae present over there. means were calculated with standard deviations. However, data Materials and Methods on total and differential numbers Material: in different sensillae were counted The colony of ant and calculated through the Leptogenys dentilobis was observed scanning electron micrographs and in MJF Educational Campus RTM the mean were separated by the Nagpur University, Nagpur (Fig. 1 least significant difference (LSD) a). The worker ants were collected, test. Consequently, significant anesthetized with chloroform and values were obtained using Graph- preserved in 70 % alcohol, the ant pad Quick Calcs. were identified with the help of database available on Iternet and Results and Discussion the same was confirmed from The mouthparts of worker experts. L. dentilobis are adapted for biting and cutting the food. The Methods: mouthparts consisted of the Morphological preparation labrum, mandible, maxilla, and (In situ): The collected worker ants labium (Fig.1). used for Scanning Electron Labrum: Microscopic analysis were The labrum is a bilobed, immobilized on ice and flattened structure and each lobe mouthparts were carefully is triangular in shape (Table.1). removed and fixed in 70% alcohol Numerous small setae are found for 12 hrs. The material was along the distal margin while the dehydrated in ethanol and cleared lateral borders are covered the long in acetone. The air dried setae. Intermediate size setae are mouthparts were fixed on metallic found in the middle area of the stubs at different angles with the extensor surface (Fig.1 c-e). Two help of superglue and were gold- types of sensilla are found on the coated separately. The material labrum, the sensilla trichoidea (ST) was scanned at a desirable and the sensilla trichoidea curvata magnification under a JOEL (STC). Trichoid sensilla are simple Scanning Electron Microscope articulated sensory hairs of the 2 MOUTHPARTS SENSILLA OF THE WORKER ANT LEPTOGENYS DENTILOBIS…… body surface while the sensilla sensilla trichoidea which are trichoidea curvata (STC) are long further subdivided into sensilla and curved at the tip (Table. 2). trichoid I, sensilla trichoidea II and Morphology categorizes the sensilla trichoidea III. The inner trichoid sensilla as ST-I, ST-II, ST- surface of the maxillae is also filled III on the basis of their length in with sensilla trichoidea (Table 2). the group. Labium: Mandible: The labium or the lower lip The mandibles are is formed by the fusion of two unsegmented and strongly secondary maxillae. The labrum is sclerotized, long with a scope like divisible into three sections- the cuticular structure and are the central mentum, followed by the largest element of the mouthparts. sub-mentum and the distal Each mandible bears along the prementum. The prementum bears longitudinal edge or outskirt of the two sets of flaps the glossae and cutting edge a row of highly the paraglossae and a pair of three sclerotized incisor teeth (10), which sectioned labial palps (Fig. 2 b-d). open outwards (to the sides of the The surface ultrastructure of head) and come together medially. labium reveals sensilla trichoidea (Fig. 1 b, d and f, g). The and sensilla trichoidea curvata dorsoventral surface of the while the labial palp bears three mandibles bears trichoid sensilla types of sensilla trichoidea, ST-I, (ST) and sensilla trichoidea ST-II, ST-III (Table. 2). curvata (STC). The trichoid sensilla are differentiated into ST-I, ST-II, Discussion and ST- III type. The sensilla In most of the ant species, trichoidea are present on the the mouthparts are adapted for marginal area of the ventral region. grasping and feeding (Table 2). (SNODGRASS, 1935; DUMPERT, 1972; RICHARD & DAVIS, 1987; Maxilla: CHAPMAN, 1982, 1988). The The maxilla is situated mouth parts of L. dentolobis are beneath the mandibles. Each adopted for biting and cutting type maxilla consists of cardo, stipes, with various types of sensilla. The galea and the maxillary palp. The morphology, distribution and size maxillary palps are three of the mouthpart sensillae has segmented. Stipes are sub- been studied in various insects rectangular, galea typically (Manduca sexta, Choristoneura formicoid with a well developed fumiferana, Spodoptera exigua and maxillary comb. At the outer C. Corneana) by the earlier margin, the galea is cupped or workers (ALBERT, 1980; CHEN & scooped (Fig. 2 a-d). The surface of HUA, 2014). Sensilla trichoidea are the maxilla are covered with freely movable setae and form 3 BARSAGADE et al. hairs of variable length with Myrmicinae ants. The mandible in generally a proportional diameter M. brunnea are powerful tools for with respect to length. They catching prey, fighting, digging, perform multiple functions such as seed crushing, wood-scraping, mechano-sensory, chemo-sensory grooming, brood care and and thermo-sensory; sensitive to trophallaxis (PAUL, 2001, touch, vibrations, air movements HOLLDOBLER & WILSON, 1990) and sound sense receptors and in L. dentilobis too, the (ERICKSON et al., 2009). The mandlbles serve similar function. trichoid sensillae on the In L. dentilobis the dorsal and mouthparts generally serve as ventral side of the worker mechanoreceptors (PAUL et al., mandibles possess densely 2002; ALBERT, 1980; CHEN & distrubeted tufts of trichoid HUA, 2014). In L. dentolobis it is sensillaof different length, similar observed that the mouthparts are situation is found in other ants too adapted for biting and cutting with (ZACHARUK, 1980; BARSAGADE two types of sensilla- sensilla et al., 2010). trichoidea and sensilla trichoidea Although BABU et al., 2011 curvata. However, in several reported the presence of olfactory respects they are also similar to sensilla (gustatory sensilla) in the the mouthparts of many ponerines mouthparts of the weaver (CHEN & HUA, 2014). Similar ant Oecophylla smaragdina such sensilla present on mouthparts of sensillae are absent from the M. brunnea are equipped with mouthparts of L. dentilobis. The mechano and chemoreceptors patterning of sensillae on the (PAUL, 2001; PAUL et al., 2002,), mouthparts of L. dentilobis are in L. dentilobis the sensilla may species specific and are used for function as mechano and food detection. chemoreceptors as found in other 4 MOUTHPARTS SENSILLA OF THE WORKER ANT LEPTOGENYS DENTILOBIS…… Table 1. Morphology of mouthparts of ant Leptogenys dentilobis. MOUTHPARTS LENGTH (µm) WIDTH (µm) Labrum 204.2±0.55 444.2±0.67 Mandible 952.3±0.69 249.6±0.44 Maxilla 491±0.70 222±0.41 Maxillary palp 250±0.65 62.48±0.70 Labium 866±0.54 371.3±0.45