Region Of Cuticle Research Articles

Light and Scanning Electron Microscopy of the Ecdysis of Haemonchus contortus Infective Larvae

During the second ecdysis of ruminant trichostrongyles, a region of the second molt cuticle is digested by a 44-kDa Zn-metalloprotease. We have examined this digestion process by light and scanning electron microscopy (SEM). The substrate region of the cuticle appeared, during the ecdysis process, as an indented ring at the 20th cuticular annulus coincident with the anterior terminus of the lateral alae. Continued digestion of the cuticle resulted in holes in the ring region that expanded until they became continuous and separation occurred between the anterior and posterior portions of the cuticle. Mechanical movements of the L3 forced aside the cuticle cap that generally remained attached on one side to the posterior portion as the larva escaped from the sheath. The site of secretion of the 44-kDa ecdysing enzyme causing cuticle digestion was not clear from morphological observations; however, existing evidence strongly points to the release of enzyme from the esophageal (pharyngeal) glands through the mouth.

Morphology and chemistry of the mandibular gland complex in the primitive termite, Zootermopsis angusticollis (Hagen) (Isoptera : Hodotermitidae)

A pair of cephalic exocrine glands are described in the primitive termite Zootermopsis angusticollis (Hagen) (Isoptera : Hodotermitidae). One of the glands, the accessory mandibular gland, is apparently undescribed and is located ventrally near the mandibular gland. The 2 glands are located on either side of the head and open in a region of intersegmental cuticle between the maxilla and the lateral margins of the head capsule. Together, the 2 glands are termed the mandibular gland complex. The morphology of the 2 glands is described using light microscopy and scanning electron microscopy. The accessory mandibular gland is formed as an invagination of intersegmental cuticle, has the shape of a 3-fingered glove, and empties via a single large pore. The mandibular gland empties via numerous pores into a pore plate which, when folded, becomes a “pocket” or reservoir. Individual accessory mandibular glands were dissected free of intersegmental cuticle and the 2 major components of the secretion of the gland were identified as n-heneicosane and n-tricosane. It is suggested that the secretion of the accessory mandibular gland may function as a recognition pheromone and/or as a spreading agent for the secretion of the mandibular gland.

MORPHOLOGICAL AND BEHAVIORAL IDENTIFICATION OF THE SENSORY STRUCTURES MEDIATING PHEROMONE RECEPTION IN THE BLUE CRAB,CALLINECTES SAPIDUS

Scanning electron microscopy was used to survey the aesthetasc tuft on the outer flagellum of the antennule (1st antenna) in order to identify sensilla potentially involved in pheromone detection by the male blue crab. These studies showed that the tuft of each antennule is divided into a mesial and lateral half by a region of cuticle from which no sensilla arise. Two setal types were revealed: the aesthetascs and previously undescribed sensilla which originate exclusively on the mesial side of the tuft and project to the lateral half between the rows of aesthetascs. Experiments were performed in which the mesial half, lateral half, or entire aesthetasc tuft was bilaterally ablated from the antennules of test males. As revealed by behavioral tests, pheromone responses in "mesial half" and "lateral half" ablation groups were reduced 22% and 21%, respectively, relative to control (P > 0.10); whereas a highly significant (P < 0.005) response decrement (80% relative to control) occurred in the "entire tuft" ablated group. The data suggest that pheromone reception in the male blue crab is effected via the aesthetascs. The relationship of these findings to those for other decapod crustaceans is discussed.

Ultrastructure des glandes tegumentaires dorsales, secretrices de la “laque” chez la femelle de Coccus Hesperidum L. (Homoptera: Coccidae)

The integumentary glands which secrete the “lac” in the female Coccus hesperidum are located in the dorsal cuticle. Each gland is formed of 4 cells; one central cell, one intermediate cell and 2 identical lateral cells. Two enveloping cells surround the gland. The secretion, called “lac resin” reaches the exterior by way of the canalicule. The secretory product of the lateral cells comes out through a highly differentiated porous region of cuticle at the extremity of the canalicule. It solidifies around the cuticular secretory pore forming a flakey mass. Their function appears to be to reinforce the integument which protects the eggs and larvae gathered under the female.

Motor patterns and structural interactions of basi-ischiopodite levator muscles in routine limb elevation and production of autotomy in the land crab,Cardisoma guanhumi

1. The anatomical and neurophysiological basis of limb elevation at the basiischiopodite joint during locomotion, resistance reflexes, activation of cuticular stress detector 1 (CSL1) and production of the autotomy fracture was studied. 2. Scanning electron micrographs of the basi-ischiopodite interior revealed that the fracture plane consists of a line of tiny perforations in the cuticle (Fig. 3 A and B), which render the limb particularly susceptible to a distorting force concentrated at a single point along the plane. 3. Both the larger anterior levator (AL) and the smaller posterior levator (PL) can elevate the basi-ischiopodite. Force applied to the AL tendon is transmitted via elastic elements to a thin region of cuticle along the fracture plane and can cause the limb to fracture; force applied to the PL tendon is not transmitted to the fracture plane. The levator tendons are mechanically linked at their insertions so that contraction of PL alters the manner in which the force of AL is applied at its tendon insertion (Fig. 5). 4. AL and PL are simultaneously active in walking and resistance reflexes although they possess no shared innervation. The levators are antagonized in both motor patterns by the depressor muscle group. 5. Autotomy elicited by injury to the limb activates large phasic units in the AL nerve; activity in the PL nerve is simultaneously suppressed. In structural terms the inactivity of PL would result in the AL tendon bracing against the internal fulcrum (Fig. 4 A) in an orientation favorable for the transmission of force to the fracture plane. 6. Both levators are activated by stimulation of CSD1. This receptor does not evoke autotomy and instead may regulate the force exerted by the levators in such a way as to relieve stress in the cuticle distal to the AL tendon insertion when the integrity of the fracture plane is threatened.

Ascaris suum: A Scanning Electron Microscope Study

The head, cuticle, and caudal region of the adult worm were examined with the scanning electron microscope. The inner and outer ring of papillae were easily visible as well as the amphids of each subventral lip. Each lip has 2 dentigerous ridges formed by 2 rows of conoidal to rectangular denticles. Variations in the anterior and posterior cuticular pattern were observed. Both male and female caudal regions end in a knob or buttonlike structure. Numerous bacteria were found surrounding the base of each caudal papilla of the male. The use of the scanning electron microscope (SEM) to study the surface features of nematodes has been reported by few investigators. Hammond (1969) and Green (1967) described several methods for preparing nematodes for SEM. Madden et al. (1970) reported on the SEM of an en face view of Ascaris suum. Anderson et al. (1970) used SEM to study cuticular lesions of Ascaris suum associated with bacteria and yeasts. These papers constitute not only the bulk of the SEM of nematodes but also show that scanning electron microscopy is an efficient and worthwhile intermediate step between light and transmission electron microscopy. This paper reports additional scanning electron microscope observations of the adult nematode Ascaris suum. MATERIALS AND METHODS Live Ascaris suum were removed from the small intestine of swine at the Meyerhoff Meat Packing Co., Munsing, Indiana, and stored in 0.9% NaCl solution at 4 C. Approximately 14 hr later, 10 live adult worms were put into 3% glutaraldehyde in a 0.1 M phosphate buffer pH 7.2, cut into 3to 5-mm sections, and fixed for 24 hr at room temperature. Following this primary fixation, they were washed several times in 0.1 M phosphate buffer, pH 7.2, and immediately postfixed in Parducz fixative (Parducz, 1967) for 4 hr. Next they were washed for 1 hr with deionized double-distilled water which was changed every 10 min. The specimens were attached to aluminum stubs and dehydrated in the following manner: A thin Received for publication 22 June 1972. * This investigation was supported by NIH Training Grant AI-00033 to Dr. Norman D. Levine. t Present address: Division of Biology, Kansas State University, Manhattan, Kansas 66506. layer of the ethyl acetate extract of double-coated tape No. 666 (3 M Co.) was applied and the specimens were mounted; enough deionized doubledistilled water was used to cover the specimens; a brass stub holder was immersed in a liquid nitrogen bath to precool it; then the stubs plus the specimens were immersed quickly in this liquid nitrogen bath to facilitate rapid freezing, the stub holder with the stubs mounted in it was transferred rapidly from the liquid nitrogen bath to an Edwards-Pearse Speedivac tissue dryer (Edwards High Vacuum, Inc.) for dehydration by sublimation for 8 hr. Next the specimens were removed and coated with gold and palladium. Specimens were examined with the Cambridge Stereoscan Scanning Electron Microscope (Cambridge Instrument Co., Ltd.), operated at 20 kv accelerating voltage.

STUDIES ON THE TAPEWORM ANOPLOCEPHALA PERFOLIATA (GOEZE, 1782).

1. The exrectory system of Anoplocephala perfoliata has been re-described and shown to consist of a dorsal ‘network’ system of vessels to which the flame cells are connected and a ventral pair of longitudinal vessels linked only by a transverse vessel in each proglottid.2. The two excretory systems unite only in the apical ramifying vessels of the scolex.3. Alkaline phosphatase activity was demonstrated in the cuticular microvilli, the subcuticular region and in the excretory vessels.4. Non-specific esterase, insensitive to 10−4m E 600, was located in the lappets and embryonated eggs and esterases, inhibited by 10−4m E600, in parts of the cuticle and subcuticular region and parenchyma.5. Cholinesterases were found in the nervous system and in the reproductive ducts.6. Aminopeptidase was found in the neck region, in the undifferentiated proglottids, the active testes and ovaries, the male reproductive ducts and in the region of high metabolic activity in the fringe of the proglottid.