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Abstract
The present work includes many major objectives , where on , ultrastructural studies have been conducted by scanning electron microscopy and focused on the distribution and description of the sense organs on the antennae , mouth-parts and cerci of the cockroach , Blattella germanica (L.).
The achieved results demonstrated the presence of many types of sensilla on the antennae of them , hair-plate sensilla ( sensilla chaetica A) which are distributed on the scape , these sensilla have a short shaft which allows movement of the hair and their function as mechanoreceptors . Thick-walled chemoreceptors ( sensilla chaetica B ) , found on all antennal segments , they have a flexible socket at the base with a hollow thick shaft , these sensilla are designated for olfaction. Thin-walled chemoreceptors ( sensilla trichodea ) ,are located on the distal parts of the flagellar segments and have sharp tipped shafts and vary in length , these sensilla are involved in olfaction and chemoreception. Basiconic sensilla , are found on the distal parts of the flagellar segments , these sensilla are hair-like and have thin-walled shafts with a blunt tip , they are chemoreceptive and their function mainly olfaction. Campaniform sensilla , found singly , scattered on the scape and concentrated as a ring around the distal margin of the pedicel , these sensilla are oval and have circular domes, they are considered to be mechanoreceptors and have an olfaction function. Coeloconic sensilla , only one sensillum has been observed on the last terminal segment of the antenna , these sensilla are short peg-like structure inside a pit , they are involved in olfaction. Pectinate scales are arranged , aggregated with large numbers around all segments of the antennae , they have bulbous bases which possess one , two or extend to six spikes ( finger-like projections ), these scales are thought to be designated for olfaction and mechanoreception.
Mouth-parts sensilla have been also observed , the labrum showed to possess, hair-plate sensilla ( chaetica A) , thick-walled sensilla (chaetica B) and few numbers of basiconic sensilla , also a well apparent structures which are numerous , dense and papillae-like , have been observed and it is thought that they are designated for gustation.
Mandibles of male and female are similar but there is difference between the distribution of teeth on the left and on the right , the sensilla on the mandible are aggregated in two groups , the first one occur on the upper left half of the ventrolateral surface of the mandible and comprised of sensilla trichodea , while the second sensillar group is occurred on the lower right half of the ventrolateral surface , it is comprised mainly of sensilla chaetica A , sensilla B and snsilla trichodea.
The sense organs of maxillae are distributed similarly on both male and female , laciniae have sensilla chaetica B on the their lateromarginal surface , while galeae have few number of sensilla chaetica A and sensill trichodea , also galeae develops an unique structures which are consisted of pectinate scales surrounded by dome , papillae like. These papillae are oval , oblong-like toward the apex , these structures have not been described before this work and they are though to be involved in gustetion. The maxillary palpus has 5 segments , the fifth segment has groove and slit sensilla (GAS) , sensilla trichodea , thick-walled sensilla ( chaetica B ) , the fourth segment has sensilla chaetica A and papillae-like projections on it’s distal margin , the third segment has sensilla chaetica A , B and sensilla trichodea , while the first and second segments have few thick-walled sensilla ( chaetica B ) , hair-plate sensilla ( chaetica A ) and few numbers of sensilla campaniformia.
Labium , is composed of prementum , mentum and the submentum , the sensilla are distributed , scattered throughout the labium and both sexes have the same types , the glossae have sensilla chaetica B and one sensillum chaeticum A , paraglossae have large number of sensilla chaetica B and one of sensilla chaetica A. Both of sensilla chaetica A and sensilla chaetica B are dispersed , scattered on the mentum , submentum. Labial palpus has four segments , the last segment has numerous trichoid sensilla while the rest of the segment filled with sensilla chaetica B which arranged in rows around it. The third segment has sensilla chaetica B and sensilla chaetica A. The first and second segments have few thick-walled sensilla ( chaetica B ) and few of hair-plate sensilla ( chaetica A) at the articulation between the first and second segments.
Cerci of male and female have the same number of segments and the sensilla are distributed throughout them , the most common type is , the thick-walled sensilla ( chaetica B ) and thin-walled chemoreceptors (trichodea) which are present with large number also there are found pectinate scales.
Microbiological studies on the alimentary canal as well as the external body of the German cockroach have been carried out in order to detect the bacterial pathogens and isolate the associated fungal species. The results obtained during the present study , relevant to bacteria , yielded isolation of five bacterial pathogens , they are respectively , Escherichia coli , species , gram-negative , non-sporing bacilli and varying from almost coccoid forms to long rods , occurred in foregut and hindgut , these microorganisms cause wound infections , enteritis , traveler’s diarrhea and urinary tract infection for human , also they are incriminated in animal pathogenicity. Actinomyeces sp. , gram-positive , non-motile and connected in chains , they were isolated and detected throughout all regions of the alimentary canal and the external body of the German cockroach , they are encountered in human and animal pathogenicity and lead to a condition referred as actinomycosis , which an infection in thorax , abdomen skin and mucosa of the mouth take place. Streptococcus faecalis , gram-positive , non-motile and appear in ovoid cells , they have been detected and observed in the alimentary canal , salivary glands and their frequency in the foregut were high , these pathogens are involved in abscesses , urinary tract infections , endocarditis and associated with mild outbreak of food poisoning and water contamination , also they cause scoure , wound infections for animals. Proteus sp. , gram-negative , non-capsulate and the rods vary in length from short to long filaments , these bacterial species were detected in the midgut and hindgut , they cause gastro-enteritis , abscesses , bed sores , skin and wound infections for man as well as they are more pathogenic for fish , dogs , cows and many other animals. Anthracoid sp. , gram-positive , motile and some are capsulated , they were detected in the midgut hindgut , legs and wings , these microorganisms have been considered to be non-pathogenic. Respecting to fungi , it has been isolated three fungal species , Aspergillus flavus , colonies have whit to yellowish margin , conidial areas are yellow-green and the conidiophores colourless , conidial heads columnar, this species is observed in midgut , hindgut and the external body also it represented the highest prevalence in the midgut , these fungal species are involved in many diseases for human such as , thickened nails , sinusitis , allergic symptoms and they invade the central nervous system. Aspergilus fumigatus , conidial areas greyed-green , conidiophores short , smooth , the conidia globose to subglobose and the conidial heads are compact and columnar , these fungal species were found throughout all different parts of the insect , they are encountered in a case called aspergillosis which lead to myocardial and pulmonary aspergillosis , also this fungal specie cause allergic diseases , cellulitis of the face as well as responsible for abortion in cattle and sheep. Candida albicans , appear as oval budding yeast with elongated cells , the fungus was observed in the foregut and the external body and showed high representation in the foregut and salivary glands. Candida albicans , cause many infections of mouth , skin , vulvovaginitis and interdigital webs of hands , also lungs , kidneys may be invaded by this fungus and results in a condition known as candidiasis , this case has been also reported in calves, poultry , birds , cows and sheep.
Parasitological studies have taken the consideration in this work , where nematode worm , Thelastomoids sp. , has been observed in the hind gut of the cockroach , the eggs of such these nematodes passes out from the alimentary canal of the insect with the faeces , they undergo development and form tad-pole like larvae , the eggs complete their life cycle when they are ingested by man or German cockroaches and hatch the worm matures , the results achieved during the present study concluded that, German cockroach, Blattela germanica play an important role in the transmission of bacterial pathogens , fungal species and nematode worms , this result in many diseases for both human and animals.