Embryonic development of the hemipteran insect Rhodnius prolixus

Abstract

The embryonic development of the hemipteran insect Rhodnius prolixus was studied by use of contemporary light and electron microscopy. Embryos were staged according to days postoviposition. Eggs laid on day one complete blastoderm formation and anatrepsis, the first phase of blastokinesis, by day 5. The embryo develops in a cephalocaudal orientation which is 180° to the anteroposterior axis of the egg. Subsequent development, prior to the second phase of blastokinesis (katatrepsis), leads to segmentation of the germ band, evagination of appendages, and histogenesis of germ layers. Concomitantly with these events, the amnion undergoes dramatic change. By day 7 the embryo begins a 180° revolution while migrating to the ventral surface of the yolk. This restores its polarity with respect to that of the egg and facilitates hatching. The serosa contracts, pulling the amnion and embryo anteriorly. Eventually the serosa is internalized at a point dorsal to the head and the lateral walls of the embryo grow up and surround the yolk. Development continues until day 15 when the embryo hatches as a first instar larva.

Evidence against a germ plasm in the milkweed bugOncopeltus fasciatus, a hemimetabolous insect

“…These caveats notwithstanding, the molecular and morphological evidence that the cells we identify in this report are bona fide Oncopeltus PGCs is comparable to that available for PGC identification in most studied animal species: (1) three conserved germ line genes, vasa , tudor , and boule , are specific germ cell markers in Oncopeltus (Figs 1–4); (2) transcripts of these genes first become enriched in germ cells specifically at the time that these cells were previously reported to arise based on morphological and cytological criteria (Figs 2–4) (Butt, 1949); and (3) cells with these molecular markers undergo migration and primordial gonad occupation (supplementary material Fig. S1; Figs 3, 4) consistent with the well-documented behavior of PGCs in many other hemipterans (Seidel, 1924; Mellanby, 1935; Butt, 1949; Sander, 1956; Kelly and Huebner, 1989; Heming and Huebner, 1994). …”

“…However, A. pisum embryogenesis is highly modified relative to that of other hemimetabolous insects and even relative to other members of the same order (Miura et al, 2003). Studies of embryogenesis in most other hemipterans describe absence of germ plasm and PGC origin after cellularisation from the blastopore region at gastrulation stages (Metschnikoff, 1866; Witlaczil, 1884; Will, 1888; Seidel, 1924; Mellanby, 1935; Butt, 1949; Sander, 1956; Kelly and Huebner, 1989; Heming and Huebner, 1994). We therefore wished to examine the expression and function of germ line genes in a hemipteran displaying embryological characteristics more representative of the order.…”

Silencing of Maternal Heme-binding Protein Causes Embryonic Mitochondrial Dysfunction and Impairs Embryogenesis in the Blood Sucking Insect Rhodnius prolixus

“…Transversal sections of fertilized red eggs laid by dsMAL-injected females and white eggs from dsRHBP-silenced females showed that dsMAL embryos were in the early stages of gastrulation, as expected (29), whereas dsRHPB embryos were not formed (Fig. 3, C-F).…”

Functional Anatomy of the External and Internal Reproductive Structures in Insect Vectors of Chagas Disease with Particular Reference to Rhodnius prolixus

“…This intricate structural relationship between the first and second valvulae may be an adaptation to serve a physiological role as the egg is passing out of the vagina. For instance, the excretory pore of the cement gland is situated on the dorsal side of the vulva near the tubular bases of the second valvulae (see Figure 3), yet on exiting the body, the cement gland secretions appear as dabs of secretions on the ventral, not dorsal, side of the egg [26]. In combination with the tubular nature of the base of the second valvula, and the ridge and groove mechanism, these valvulae may function to direct cement gland secretions onto the ventral surface of an egg as it passes through the vulva.…”

“…Second, this indentation appears to be directly related to the egg passing through the vulva, and not due to structural changes after being laid. In a SEM image of an egg passing out of the vulva, the exiting egg already shows a distinct indentation under the dorsal genital segment [26].…”