Morphological aspects of immature stages of Migonemyia migonei (Diptera: Psychodidae, Phlebotominae) an important vector of Leishmaniosis in South America by scanning electron microscopy

We describe the immature stages of Migonemyia migonei, which is the vector of Leishmania (Viannia) braziliensis, the aetiological agent of cutaneous leishmaniasis in South America, and a putative vector of Leishmania infantum chagasi. Scanning Electron Microscopy (SEM) was used to refine the description of the structures of eggs, all instar larvae and pupa. The eggs have polygonal cells on the egg exochorion, and differences between larval and pupal chaetotaxy are highlighted. Different sensillary subtypes were observed in the larval stages, among the types trichoidea, basiconica, coelonica and campanoformia. These results contribute to the taxonomy of Mg. migonei and may contribute to future studies on the phylogeny of this important species vector.


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In the last few decades, new proposals in phylogeny sand flies, especially based 28 on adult morphology has been highlighted and several authors have adopted the Galati 29 [1,2] proposal, that changed the taxonomy, phylogeny and nomenclature basis of 30 phlebotomine systematic. However, the knowledge about several aspects of the 31 immature stages of phlebotomine sand flies (Diptera: Psychodidae) is still a challenge, 32 due to the difficulties of finding a natural breeding site or lab colonization. So, of about 33 more than 537 species described in the Neotropics [1][2][3], larval stages or mature larvae 34 and rarely pupae of only 92 species of the New World sand flies have been described, or 35 partially described. 36 Larval structures are important for providing some highlights on taxonomy, 37 phylogeny, and evolution of this subfamily. In the last few decades, new proposals have 38 been highlighted on phylogeny of sand flies, especially based on adult morphology, and 39 several authors have adopted the Galati proposal [1,2], which has changed the 40 taxonomy, phylogeny and nomenclature basis of phlebotomine systematic. 41 The analysis of the microstructure of the immature stages of Phlebotominae,in 42 addition to contributing to the discovery of other morphological characters capable of 43 promoting taxonomic and phylogenetic studies, in order to better elucidate the evolution 44 of this subfamily, also makes it possible to investigate the existence of sense structures 45 used in the communication of these vectors, aiming at the development of alternative 46 eco-friendly control strategies. 47 Morphology and chaetotaxy of the head were observed following the 77 methodology of Arrivillaga[26], which indicates the morphology and setae of the 78 mouthparts with taxonomical importance. Chaetotaxy of the body followed the system 79 used by Ward [27]. The chaetotaxy of the pupae used in this study followed the 80 terminology proposed by Oca-Aguilar [8]. Systematic classification follows that 81 proposed by Galati [2], and abbreviations of the genera follow Marcondes [28]. In   General appearance of the larvae of Mg. migonei: The larva is caterpillar-like, 104 with a well-sclerotized hypognathous, non-retractile head with very short antennae with 105 short basal tubercle. The dark brownish colour head and body tegument are covered by very 106 small spines and tubercles in a scattered distribution. The thorax includes prothorax, with the 107 anterior spiracle borne laterally, and other two segments (meso and metathorax). Its 108 abdomen is nine-segmented, covered by brown pale setae and the body tegument is 109 yellowish, with a pair of posterior spiracles borne laterally on a short tubercle.

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Caudal filaments (or caudal setae), long sensilla of the trichoid type that exhibit many 111 wall pores, implanted between non-parallel ridges and that interconnect (or which overlap), 112 darkened, were observed double-paired in the last three instars, or simply paired when is in 113 the first instar ( Fig. 2A-B).

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The head is dark brown ( Fig. 2A, 3A), body colour is pale with darkened eighth and 115 ninth abdominal segments and bears tiny spines in all segments ( Fig. 2A, Fig 7), the first  Table 1.

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Head: The head is capsule-like, broader than it is high. The tegument is covered by thin, 129 small spicules of the microthrichia type. On the dorsal part of the head (Fig.3A), the cephalic 130 tagma has the following setae: the anterior frontoclypeal setae (1 weakly brush-like trichoid 131 sensilla, subtype) with spinulate form, the posterior frontoclypeal setae (2;brush-like trichoid 132 sensilla, subtype) with barbed shape, the anterior genal setae (3) with a simple spine form.

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Each maxilla has three simple setae, an S1 in the apical dorsal part, and two (S2   The thorax has three segments, the prothorax has the appearance of two segments,  These setae are similar, barbed or brushed-like and have only small differences in size (Table   211 1). There is a spine hyaline seta, between the first and second rows of setae, usually near the 212 ventrolateral setae. The sternite also has two rows of setae. The first with two similar pairs of 213 setae, a little less barbed than the dorsal setae, the ventral external and the ventral internal.

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The second row has seven pairs of setae, including the seta b, with different size and shape 215 (Table 1) Table 1). The sternites (Fig. 8) (Fig. 8A). These tubercles, in the ventral side, also possess a large campaniform 249 sensilla (Fig. 9B). The posterior spiracle has 14-11 papillae.  Table 1). The pupa emerges from a Y shaped suture of the head of mature larva (Fig 11A- (Fig. 12A, 13, 15, 16). The pupa tegument has some small 284 ornaments, such as small spines and setae, which are described in Table 3 and the body   285 is covered by several small rounded tubercles. The pharate female pupa is longer (2.24 286 mm, n = 5) than the pharate males pupa (2.05 mm, n = 5) (Fig. 17).  The tegument of the abdomen is covered by several small, spiniform tubercles. There 307 are nine segments, and the width of every segment is near twice its own length. They 308 diminish gradually in size towards the distal region ( Fig. 10 A), becoming discrete  and two pairs on the sternum and two pairs on the spiracle (Fig. 16F). All these are very 320 small basiconic setae. Abdominal segment IX is covered by the larval exuvia (as is 321 VIII), but when uncovered, sexual morphological differences can be observed. In males, 322 there are two lobes on each side -one simple, covering the lateral lobe, and the other 323 divided, containing the gonostylus and gonocoxite In females, two simple and short 324 lobes on each side -one covering the oviscape and the other the cercus, though without 325 setae (Fig. 17), and the genital opening sheath is discreet (Fig. 16E). Abdominal 326 chaetotaxy can be seen in Table 2