1010 Journal of Applied Sciences Research, 9(1): 1010-1014, 2013 ISSN 1819-544X This is a refereed journal and all articles are professionally screened and reviewed

ORIGINAL ARTICLES

Red palm weevil, Rhynchophorus ferrugineus and harvest , Anacanthotermes ochraceus with the infrared receptors structures as a sensitive detector to hosts and shelters

Mohamed Ragaei and Al-Kazafy H. Sabry

Pests and Plant Protection Dep. National Research Centre, Dokki, Egypt

ABSTRACT

This experiment was carried out to investigate the infrared receptors on the red palm weevil, Rhynchophorus ferrugineus (Olivier) and harvest termites, Anacanthotermes ochraceus (Burmeister). The results showed that these have infrared receptors on their bodies. These infrared receptors were found on the cuticle of larvae, pupae and the adult's wings of the red palm weevil, and found also on the cuticle of ’s workers. These infrared receptors are called sensilla which distributed on the cuticle. In addition the cuticle and wings of these insects have absorbance area which uptake the heat of infrared radiation. The adult of red pal weevils may be rely on sensilla on its wings which respond to broadband infrared radiation. These infrared radiations attract and lead them to warm place, where they will most likely to lay their eggs. On the other hand, termite may be use the heat of infrared radiation in food metabolism.

Key words: cuticle, wings, infrared radiation, food, insects

Introduction

Infrared radiation is a part of the electromagnetic spectrum, nearest red in the visible range. Their existence has been known for several hundred years (Maldague and Moore, 2001). Although invisible to the human eye, infrared energy has a penetrating heating effect and is easily felt when encountered. Most objects, living or not, give off infrared heat, whether internally generated or reflected. Initial uses of infrared were for military surveillance, as early as World War II (Maldague and Moore, 2001). Today, there are many nonmilitary uses and include measurement devices, binoculars, night viewing for hunting, etc…. In structures, infrared devices have been used to find faulty electrical connections and heat and water leaks in walls and roofs (Maldague and Moore, 2001). A more recent use includes termite detection (Lewis, 2003). Beetles of the genus Melanophila and certain flat bugs of the genus Aradus actually approach forest fires. For the detection of fires and of hot surfaces the pyrophilous species of both genera have developed infrared (IR) receptors, which have developed from common hair mechanoreceptors (Klocke et al., 2011). The little ash , Acanthocnemus nigricans depends on fires for its reproduction and is equipped with a pair of sophisticated prothoracic IR receptors (Kreiss et al., 2005). Whereas the olfactory receptors for smoke are located on the antennae, the IR receptors are housed in extra-antennal sensory organs, which can be found on the thorax or on the abdomen (Klocke et al. 2011). The same authors found also, Melanophila beetles and Aradus bugs are equipped with sensory structures that allow both the detection of hot fires at considerable distances as well as being able to locate moderately hot spots close by. These insects feature so-called photomechanic IR receptors, which might serve well as models for the technical design of un-cooled IR receptors. In the present paper we focus on the structure and function of the biological model as well as on the design and theoretical evaluation of a technical photomechanic IR sensor. Schmitz et al. (2002) found that the Australian beetle Acanthocnemus nigricans is attracted by forest fires and has a pair of complex infrared (IR) receptor organs on the first thoracic segment. Each organ consists of a tiny sensory disc (diameter 120–130 µm) which serves as an absorbing structure for IR radiation. Miles (1966) described that the infrared radiation has stimulation factor in the cockroaches orientation in darkness. Campell et al. (2002) reported that infrared (IR) pit organs of common vampire bats, Desmodus rotundus enable them to detect IR radiation emitted by blood-rich locations on homeothermic prey. Barrett et al. (1970) stated that Crotaline and Boid snacks possess infrared imaging receptors called pit organs, which work along with their visual and other sensory system to enable them to detect, locates and apprehend prey. Schmitz and Bleckmann (1998) recorded from single units of individual sensilla of the thoracic infrared (IR) pit organs of Melanophila acuminata. Lazzari and Nunez (1989) found that bloodsucking bugs use IR receptors to detect warm-blooded prey. Gronenberg and Schmitz (1999) found that the

Corresponding Author: Al-kazafy H. Sabry, Pests and Plant Protection Dep. National Research Centre, Dokki, Egypt, E-mail: [email protected] 1011 J. Appl. Sci. Res., 9(1): 1010-1014, 2013

IR-sensitive receptors of Melanophila acuminata are also specialized structures, even more so than wind- sensitive hairs on the wings. Most insects have IR receptors in wings. In locusts, sensory afferents originating from the wing tegula (Bräunig et al. 1983), from the wing-hinge stretch receptors (Altman and Tyrer, 1977), or from the wing itself (Bräunig et al. 1983) terminate plurisegmentally, as do wing afferents in the beetle Tenebrio (Breidbach, 1990) and in winged ants (Gronenberg and Peeters, 1993). This work aims to investigate the site and role of infrared receptors in red palm weevil (larvae, pupae and adult wings) and termites as well.

Materials and Methods

1. The experimental insects:

The pupae and larvae of the red palm weevil, Rhynchophorus ferrugineus were obtained from infested palm tree and reared under laboratory condition (26 ± 1 ºC and 70 ± 5% RH) until adult emergence. The workers of termite were obtained from Plant Protection Research Institute, Giza, Egypt. This work was conducted in National Research Center, Dokki, Egypt.

2. Sample preparation:

Adult, larvae, pupae of red palm weevils and termite workers were freeze by liquid nitrogen then dried in the chamber of the scanning electron–microscope, SEM (Jeol-JSM-5600 LV in SEM) in the low vacuum mode. Then the micrographs were taken, this technique called low vacuum scanning electron microscope freeze drying (L V-SEM) (Gasser et al., 2008). This technique resulted in the presence of few small particles in white color represents ice during freeze drying technique of the specimens in low vacuum SEM on the micrographs.

Results:

1. Role of IR receptors in red palm weevil:

Many investigators focused on mature stage to detect the role of infrared receptors (IR). Figure 1a and 1b showed that there are many hairs on the body larvae of red palm weevil, Rhynchophorus ferrugineus. These hairs called IR sensilla.

Fig. 1: Infrared receptors in the cuticle of red palm weevil larvae, (IR-S) infrared sensilla; (1a) showed the single IR-S and (1b) showed many IR.

The IR receptors most likely have evolved from common contact mechanoreceptors. The female weevil prepares a small hole with its snout in the soft tissues of the trees or in the existing wounds in the crown or trunk. A female lays about 200-500 oval whitish eggs during its oviposition period, of about 34 months. Soft whitish grubs on hatching feed on the soft tissues and tunnel into the tree trunk. Figure (2a) demonstrated that the pupae of red palm weevil have many IR receptors. Larvae pupate inside cocoons in the palm trunk, or in concealed places at the base of palm fronds. The pupal stage may last from 11 to 45 days. Figure (2b) showed that the sensilla (IR receptors) shaped with the brush. These sensilla help the pupae of red palm weevil to uptake the heat of infrared radiation.

1012 J. Appl. Sci. Res., 9(1): 1010-1014, 2013

Fig. 2: Infrared receptors in the cuticle of red palm weevil pupae, (IR-S) infrared sensilla; (2a) showed the single IR-S and (2b) showed IR shaped with the brush.

Figure (3a) showed the small bores in the adult's wings. These bores called absorbance area which absorbs the heat of infrared radiation. On the other hand, Figure (3b) showed the infrared sensilla distributed on the wings of the red palm weevil. These sensilla receive the infrared radiation.

Fig. 3: The infrared receptors on the wing of red palm weevil; (3a) showed the bores of heat absorbance (AA) and (3b) showed the sensilla on the wings.

IR receptors in termites:

Our results indicate the presence of many hairs on termite workers cuticle which act as infrared receptors and also shows the absorbance area bores (AA) (Fig. 4 a&b). As shown in Figure (4), the infrared receptors are found on the cuticle of termite workers body, forming the infrared receptors. Figure (4b) shows the absorbance bores in cuticle of termite workers. These bores are absorbing the heat of infrared radiations and use it in different bioactivities.

Fig. 4: Infrared receptor (IR) in termite workers: (4a) many hairs in termite workers make as infrared receptors and (4b) shows the absorbance area bores (AA).

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Discussion:

The larvae of red palm weevil may be used the IR sensilla to search the suitable food. The grubs cause damage inside the stem or crown by feeding on soft tissues and often cause severe damage especially when a large number of them bore into the soft growing parts. This IR receptor may be uptake IR radiation in a way not described in detail, the resulting thermal expansion of the cuticular sphere and gives the larvae energy needed for growth. This pupa may be using the IR receptors to get the thermal energy in its environment. So, many and insects use the infrared sensilla as thermoreceptors. The same result was found by Gronenberg and Schmitz (1999). The authors found that the development of these sensilla in pupae, as one would expect dome-shaped and hair-like sensilla at the leg base to share initial developmental steps. Many investigators focused in the abdominal segments of adult but in this work the IR receptors on wing were studied. The results showed the absorbing area (AA) which absorbs the heat by IR receptors. Schmitz et al. (2007) found that IR radiation absorbed by the proteins, the chitin fibers and the water of the sensillum heats up the sphere which immediately causes thermal expansion especially of the fluid inside the spongy mesocuticular layer. The same results were found by Fenomore (1980). The authors found that the adults of red palm weevil were detected the oviposition sites by physical nature of their surface and chemical factors. Mainz et al. (2004) found that IR organs and two types of transitional stages were found ventrolaterally on the second, third, and fourth of the five abdominals sternites. A fully developed IR receptor consists of a round absorbing area. Ragaei (2010), mentioned that, wings of the red palm weevil contains materials that would act as semiconductors. Mahmoud et al. (2012) found that many sensilla distributed on antenna of palm weevil adults. The adults of red palm weevil use these sensilla to get their food, oviposition and mating. Schmitz et al. (2007) reported that two models of sensilla function can be found. The first one was so called photomechanic principle. The authors proposed that the biomolecules (i.e. proteins and chitin) of the cuticular sphere strongly absorb mid-IR radiation. In a way not described in detail, the resulting thermal expansion of the cuticular sphere is measured by the mechanoreceptor. The second model that IR radiation enters this cavity by a small apical waveguide with a diameter of about 1.5 µm. Due to the absorption of IR photons at the inner cuticular walls of the cavity; the enclosed air is heated up and expands. In a way not further specified the resulting increase in gas pressure should stimulate the mechanoreceptor. The same authors also, reported that any deviation from the bauplan (is a closely related term in biology referring to the common new and original (homologous) properties of the members of a systematic group (taxon)) of a hair mechanoreceptor is of particular concern for the transformation of IR radiation into a mechanical stimulus. It's known that termite workers seem to be blind, due to their undeveloped eyes (http://www.termiteweb.com/the-worker-termites). Termite soldiers are usually blind, but in some families, particularly among the dampwood termites, soldiers developing from the reproductive line may have at least partly functional eyes (Bordereau et al., 1997 and Ross, 2007). Jaffe et al. (2012) stated that it’s known that termites use trail pheromones to mark a trail which is followed by conspecifics. Each individual deposits a small amount of pheromone from the sternal gland onto the substrate. This effect can be used to show the characteristic trail-following behavior of the termites. Our results indicate the presence of many hairs on termite workers cuticle, which acts as infrared receptors. The cuticle of termites also has an absorbance infrared area which absorbs heat from infrared radiation. Use aging refers to a process that the protein, lipid, or carbohydrate contained in food is digested by microorganisms which existed in the termites gut. Aging of proteins, lipids, or carbohydrates usually results in unique flavors. Irradiation of far infrared rays can cause activation of microbial growth. So, the infrared helps in food digestion. These hairs receive the infrared radiation and uptake the heat which used in growth of microorganisms in gut. These microorganisms help termites in digestion of cellulose in gut.

Acknowledgments

We are indebted deep thanks for Dr. Amira M El-Rafei, Refractories, Ceramics and Building Materials Dept. National Research Centre, Dokki, Egypt for her helpness in scan microscope photos.

References

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