Dissection Of Cockroach Pdf Download
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In this article we will discuss about the dissection of cockroach. Also learn about:- 1. The Alimentary System 2. Dissection of Salivary Apparatus 3. Dissection of Nervous System 4. Dissection of Reproductive System.
Carefully remove all the tracheae and fat in the region where the salivary apparatus is lodged. Turn the crop as required and trace the ducts anteriorly running from the glands and the receptacles along the sides of the crop and then ventral to the oesophagus. Pin down the head of the cockroach with ventral surface upward.
Diet is a major determinant of bacterial community structure in termite guts, but evidence of its importance in the closely related cockroaches is conflicting. Here, we investigated the ecological drivers of the bacterial gut microbiota in cockroaches that feed on lignocellulosic leaf litter.
The physicochemical conditions determined with microsensors in the guts of Ergaula capucina, Pycnoscelus surinamensis, and Byrsotria rothi were similar to those reported for both wood-feeding and omnivorous cockroaches. All gut compartments were anoxic at the center and showed a slightly acidic to neutral pH and variable but slightly reducing conditions. Hydrogen accumulated only in the crop of B. rothi. High-throughput amplicon sequencing of bacterial 16S rRNA genes documented that community structure in individual gut compartments correlated strongly with the respective microenvironmental conditions. A comparison of the hindgut microbiota of cockroaches and termites from different feeding groups revealed that the vast majority of the core taxa in cockroaches with a lignocellulosic diet were present also in omnivorous cockroaches but absent in wood-feeding higher termites.
Our results indicate that diet is not the primary driver of bacterial community structure in the gut of wood- and litter-feeding cockroaches. The high similarity to the gut microbiota of omnivorous cockroaches suggests that the dietary components that are actually digested do not differ fundamentally between feeding groups.
Cockroaches are the closest relatives of termites [1, 2]. The intestinal tracts of both insect groups are densely colonized by a symbiotic gut microbiota of bacteria and archaea, and sometimes also unicellular eukaryotes [3,4,5]. The gut microbiota of termites and its role in symbiotic digestion have been studied intensively during the past decades (for reviews, see [6,7,8]). In all evolutionarily lower termite families, lignocellulose digestion is carried out primarily by a dense assemblage of symbiotic flagellates, which are absent in all cockroaches and higher termites (family Termitidae). In the wood-feeding members of the Termitidae, their key roles in the digestion of cellulose and hemicelluloses were apparently replaced by specific lineages of Fibrobacteres and Spirochaetes [9,10,11].
Much less is known about the bacteria colonizing the intestinal tracts of cockroaches and their role in symbiotic digestion. While termites are highly specialized on a lignocellulosic diet, cockroaches are mostly omnivorous scavengers that typically exploit a variety of food sources . Nevertheless, lignocellulosic plant litter and decaying wood present a major food source for many species, and lignocellulose digestion by cockroaches is considered to play a critical role in the turnover of organic matter in forest ecosystems .
In the wood-feeding Parasphaeria boleiriana (Blaberidae: Zetoborinae) and all members of the genera Panesthia and Salganea (Blaberidae: Panesthiinae), which dwell in decaying wood logs [13,14,15], xylophagy most likely evolved independently from that in the termite clade . Also many detritivorous cockroaches feed on leaf litter or other diets rich in lignocellulosic substrates . The survival of xylophagous Panesthiinae on pure cellulose has been attributed to the presence of glycoside hydrolases produced by both the host and its gut microbiota ([15, 17]; for a review, see ), but detailed balances of plant polymer degradation in litter-feeding cockroaches are lacking.
In all cockroaches investigated to date, microenvironmental conditions are rather uniform. The gut content is slightly acidic to neutral and has a negative redox potential [26,27,28]. In adult cockroaches, the center of all gut compartments is typically anoxic, but in the gut of early larval stages, suboxic conditions have an impact on microbial community assembly during host development . Hydrogen accumulation has been reported only for the posterior midgut of the omnivorous scavengers Blaberus sp. and Shelfordella lateralis (maintained on formulated rabbit or chicken feed) [26, 30], and for the crop of Panesthia angustipennis (maintained on decaying wood) . Each major gut compartment of the omnivorous S. lateralis, the wood-feeding P. angustipennis, and a detritivorous Panchlora sp. (maintained on refuse pile material of leaf-cutter ants) distinctly differs in structure and composition of its bacterial community [26, 27, 31]. In experiments with germ-free S. lateralis that were inoculated with gut communities from various hosts, similar microbial lineages were selected by the gut environment, irrespective of the inoculum , which suggests a strong selection pressure by the microenvironmental conditions and the functional niches available in the gut.
It remains unclear whether structure and composition of the bacterial gut microbiota of cockroaches are strongly affected by diet. A significant response of the hindgut microbiota to diets with different protein contents was found in the omnivorous Blattella germanica  but contrasts with a resilience to dietary changes reported for Periplaneta americana . In S. lateralis, potential effects of high-protein and high-fiber diets of bacterial community structure were masked by strong individual variations . The high similarity in the bacterial community structures of omnivorous cockroaches and a Panchlora sp. that lives in the refuse piles of fungus-cultivating leafcutter ants suggests the existence of a core microbial community that is independent of a particular diet . However, the number of cockroach species investigated so far is too small to test the effects of host diet on bacterial community structure, and information on representatives that thrive on lignocellulosic plant litter is sorely needed.
We addressed this gap by characterizing the bacterial gut microbiota of cockroaches from the genera Byrsotria, Pycnoscelus, and Ergaula, which represent litter feeders from three subfamilies (Blaberinae, Corydiinae, Pycnoscelinae), are available from commercial breeders, and can be maintained on a diet of dried oak leaves. Using high-throughput amplicon sequencing of the bacterial 16S rRNA genes, we taxonomically analyzed the communities using a phylogenetically curated reference database (DictDb), tailor-made for the accurate identification of bacterial lineages specific to termite and cockroach guts , and compared community structure and composition to previously published datasets of cockroaches from other diet groups. To identify differences in microenvironmental conditions responsible for differences in community structure between compartments, we used microsensors to determine oxygen and hydrogen partial pressure, intestinal pH, and redox potential of the gut lumen along the entire intestinal tract. To determine whether host diet determines bacterial community structure in cockroaches, we identified the core bacterial families in cockroaches with a lignocellulosic diet and compared them to those in omnivorous cockroaches and xylophagous higher termites.
Canonical correspondence analysis (CCA) of the relative abundance of bacterial genera and environmental variables in gut compartments of the litter-feeding cockroaches Ergaula capucina (Ec), Byrsotria fumigata (Bf), and Pycnoscelus surinamensis (Ps). Each dot represents a genus-level group, with the color indicating the family affiliation and the size indicating its mean relative abundance. Each of the 435 bacterial genus-level groups was tested for covariance with the environmental variables: physicochemical conditions (pH, hydrogen partial pressure, and redox potential), host species, and gut compartment (gray labels). Approximate weighted averages of the communities in each gut compartment are shown as boxes labeled with the corresponding species abbreviation. Environmental variables are shown as directional axes (arrow length proportional to the total variance constrained by the variable). The position of a bacterial genus or community relative to the axis of an environmental variable indicates the level of correspondence between the respective genus or community and the environmental variable. Constrained inertia is equivalent to the total variance constrained by all environmental variables combined. For more details, see Additional file 2: Table S2
A comparison of the five lignocellulose-feeding cockroaches revealed that the core families shared between homologous guts made up the bulk of the bacterial community in the hindgut compartments. The similarity at the family level between the homologous gut compartments of both wood- and litter-feeding hosts was much higher than the similarity between the different gut compartments of the same species (Fig. 5). Pycnoscelus surinamensis was an exception to this trend because the core communities shared with other cockroaches was very small. In all hosts, the average contribution of the core families to the entire bacterial community increased from crop (37%) to midgut (66%) to hindgut (81%).
Similarity of the bacterial communities (family level) and abundance of core lineages in the different gut compartments of five lignocellulose-feeding cockroaches. Community similarity (Morisita-Horn index) between consecutive gut compartments of the same species (red) and between homologous gut compartments of different species (blue) is indicated by the width and the opacity of the connecting arcs. The relative abundance of core lineages (families represented in all homologous gut compartments) is indicated by the size of the concentric filling (black) of the circles, which represent the crop (C), midgut (M), and hindgut (H) compartments of Ergaula capucina (Ec), Byrsotria fumigata (Bf), Pycnoscelus surinamensis (Ps), Panesthia angustipennis (Pa), and Salganea esakii (Se). For numerical values, see Additional file 2: Table S3 2b1af7f3a8