Digestive And Tracheal System of Menopon Gallinae (Phthiraptera: Amblycera) Infesting Poultry Bird (Gallus Gallus Domesticus)

The digestive and tracheal system of a poultry shaft louse, Menopon gallinae (Phthiraptera: Amblycera) has been studied in greater details. Alimentary canal of louse was dissected out along with crop under stereozoom binocular microscope. Entire alimentary canal of M. gallinae was found more or less straight and has three basic parts (fore-gut, mid-gut and hind-gut) while crop-teeth was present in the crop. The posterior end of crop contains 20-30 well developed crop-teeth arranged in a single arced plate, in comb-like fashion. Mid-gut was found as simple tube and contributes nearly one half of the total length, while the hind-gut was marked by the opening of Malpighian tubules in alimentary canal. The heart of M. gallinae is of simplest kind, one chambered bulbous structure having three pairs of laterally placed ostia and supported by four pairs of alary muscles. In the tracheal system there were seven pairs of spiracles occurred on the terga of M. gallinae. The first pair of spiracle was found located close to legs while remaining six abdominal spiracles occur from segment 3rd to 8th. The degree of tracheation of various visceral organs has also been noted.

Twist regulates Yorkie to guide lineage reprogramming of syncytial alary muscles

SummaryThe genesis of syncytial muscles is typically considered as a paradigm for an irreversible developmental process. Notably, transdifferentiation of syncytial muscles is naturally occurring during Drosophila development. The ventral longitudinal heart-associated musculature (VLM) arises by a unique mechanism that revokes the differentiated fate from the so-called alary muscles and comprises at least two distinct steps: syncytial muscle cell fragmentation into single myoblasts and direct reprogramming into founder cells of the VLM lineage. Here we provide evidence that the mesodermal master regulator twist plays a key role during this reprogramming process. Acting downstream of Drosophila Tbx1 (Org-1) in the alary muscle lineage, Twist is crucially required for the derepression of the Hippo pathway effector Yki and thus for the initiation of syncytial muscle dedifferentiation and fragmentation. Subsequently, cell-autonomous FGFR-Ras-MAPK signaling in the resulting mono-nucleated myoblasts is maintaining Twist expression, thereby stabilizing nuclear Yki activity and inducing their lineage switch into the founder cells of the VLM.

Yorkie and JNK revert syncytial muscles into myoblasts during Org-1–dependent lineage reprogramming

Lineage reprogramming has received increased research attention since it was demonstrated that lineage-restricted transcription factors can be used in vitro for direct reprogramming. Recently, we reported that the ventral longitudinal musculature of the adult Drosophila heart arises in vivo by direct lineage reprogramming from larval alary muscles, a process that starts with the dedifferentiation and fragmentation of syncytial muscle cells into mononucleate myoblasts and depends on Org-1 (Drosophila Tbx1). Here, we shed light on the events occurring downstream of Org-1 in this first step of transdifferentiation and show that alary muscle lineage-specific activation of Yorkie plays a key role in initiating the dedifferentiation and fragmentation of these muscles. An additional necessary input comes from active dJNK signaling, which contributes to the activation of Yorkie and furthermore activates dJun. The synergistic activities of the Yorkie/Scalloped and dJun/dFos transcriptional activators subsequently initiate alary muscle fragmentation as well as up-regulation of Myc and piwi, both crucial for lineage reprogramming.

Yorkie and JNK revert syncytial muscles into myoblasts during Org-1 dependent lineage reprogramming

SummaryLineage reprogramming has become a prominent focus in research since it was demonstrated that lineage restricted transcription factors can be used in vitro for direct reprogramming [1]. Recently, we reported that the ventral longitudinal musculature (VLM) of the adult Drosophila heart arises in vivo by direct lineage reprogramming from alary muscles (AM), a process which starts with dedifferentiation and fragmentation of syncytial alary muscles into mononucleate myoblasts. Central upstream activators of the genetic program regulating the development of VLMs from alary muscles are the T-box factor Org-1 (Drosophila Tbx1) and the LIM homeodomain factor Tup (Drosophila Islet1) [2]. However, the events downstream of Org-1 and Tup that exert dedifferentiation and fragmentation of alary muscles have been unknown. In the present report, we shed light on the initiation of this first step of transdifferentiation and show that AM lineage specific activation of Yorkie (Yki), the transcriptional co-activator of the transcription factor Scalloped (Sd), has a key role in initiating AM lineage reprogramming. An additional necessary input comes from active dJNK signaling, which contributes to the inactivation of the Hippo kinase cascade upstream of Yki and furthermore activates dJun. The synergistic activities of the Yki/Sd and dJun/dFos (AP-1) transcriptional activator complexes in the absence of Hippo activity initiate AM dedifferentiation and lead to the expression of Myc and piwi, which are crucial for different aspects of AM transdifferentiation. Our results provide new insights into the mechanisms that mediate muscle lineage plasticity during a cellular reprogramming process occurring in vivo.HighlightsDirect lineage reprogramming of alary muscles depends on Yorkie and JNKYorkie and JNK mediate reversal of syncytial muscle cell fateYki/Sd and AP-1 induce alary muscle dedifferentiation synergisticallyYki dependent Myc induces and Piwi mediates reprogramming of alary muscles

The Basic Plan of the Adult Heart Is Conserved Across Different Species of Adult Mosquitoes, But the Morphology of Heart-Associated Tissues Varies

The heart is a pivotal organ in insects because it performs a number of different tasks, such as circulating nutrients, hormones, and excreta. In this study, the morphologies of the heart and associated tissues, including pericardial cells (PCs) and alary muscles (AMs), in the hematophagous mosquitoes Anopheles aquasalis Curry (Diptera: Culicidae), Aedes aegypti L. (Diptera: Culicidae), and Culex quinquefasciatus Say (Diptera: Culicidae), and the phytophagous Toxorhynchites theobaldi Dyar & Knab (Diptera: Culicidae) were compared using different microscopy techniques. Mosquito hearts are located across the median dorsal region of the whole abdomen. Paired incurrent openings in the heart wall (ostia) are found in the intersegmental regions (segments 2–7) of the abdomen, while an excurrent opening is located in the terminal cone of Ae. aegypti. The sides of the heart contain PC that are more numerous in An. aquasalis and Th. theobaldi. In these two species, PC form a cord of as closely aggregated cells, but in Ae. aegypti and Cx. quinquefasciatus, PC occur in pairs with two or four PC pairs per intersegmental region. In Th. theobaldi, AM binds to all regions of the heart, whereas in other mosquitoes they only bind in the intersegmental regions. The basic plan of the adult heart was conserved across all the adult mosquitoes investigated in this study. This conserved organization was expected because this organ plays an important role in the maintenance of individual homeostasis. However, the species had different PC and of AM morphologies. These morphological differences seem to be related to distinct physiological requirements of mosquito circulatory system.