Extrusion of masses of yolk during embryonary development of the fruit flyAnastrepha fraterculus

Abstract

Eggs of the fruit fly Anastrephafiaterculus (Diptera; Tephritidae) present an extensive variation in size. On average, they measured 1,4 15h86 pm in length and 24 1h 16 pm in diameter. In vivo analysis of the embryonic development showed that, during gastrulation, the embryos may extrude a mass of yolk from their posterior end. Later on, during the development of the head, a similar mass may also be extruded fiom the anterior end. Four types of embryos were found:(1) embryos with masses at both ends; (2) embryos with only the anterior mass; (3) embryos showing just the posterior mass and (4) embryos without any mass. They occur in different frequencies in a sample of embryos collected fiom a population cage in which type 1 embryos were the most common. The masses varied in size, there being no significant differences between the anterior and posterior ones, nor among masses fiom different types of embryos. The masses are made of yolk material and contain a variable number of vitellophages. Hoechst staining revealed the presence of symbiont bacteroids in the masses. Electron microscopy confirmed these results. Just before hatching, the larva eats the anterior mass, then makes a 180" turn inside the egg, ingests the posterior mass and finally hatches near the posterior pole of the egg. The extrusion of the masses and the complex behavior of the larva may be related to the mechanism of bacterial infestation in this species.

Current knowledge of the species complex Anastrepha fraterculus (Diptera, Tephritidae) in Brazil

“…However, one karyotype described from Bahia actually corresponded to Anastrepha sororcula Zucchi (Morgante et al 1993). In the nominal species Anastrepha fraterculus , similar acrocentric autosomes and chromosome numbers (2n=12) have been described from populations in Mexico, Brazil and Argentina (Mendes 1958, Bush 1962, Solferini and Morgante 1987, Selivon et al 1996, Selivon et al 1997, Basso et al 2003). In the Brazilian species complex, conspicuous differences in the sex chromosomes were found.…”

“…Some studies conducted in the 1990’s correlated morphological traits and genetics of Brazilian samples (Selivon and Perondini 1998, Selivon et al 1996, 1997, 1999), enabling the recognition of two different biological entities within the complex (referred in this paper as Anastrepha sp.1 or Brazilian-1 and Anastrepha sp.2 or Brazilian-2). Later Selivon et al (2004, 2005a,b) used diverse sources and proposed the existence of a third Brazilian entity named Anastrepha sp.3 aff.…”

“…In this work, some degree of postzygotic reproductive isolation was found among F1 crosses between Anastrepha sp.1 males (Vacaria, Rio Grande do Sul) and Anastrepha sp.2 females (Conceição do Almeida, Bahia). Cytoplasmic incompatibility between different Wolbachia strains found in eggs of Anastrepha sp.1 and Anastrepha sp.2 has been suggested as one of the causes of their postzygotic reproductive isolation (Selivon et al 1996; Selivon et al 1999; Selivon et al 2002). Later, Wolbachia strains were also found in adults from Piracicaba (Cáceres et al 2009) as well as in Anastrepha sp.…”

Oviposition of fruit flies (Diptera: Tephritidae) and its relation with the pericarp of citrus fruits

“…According to Ferrar (1987), the hatching of larvae of C. capitata occurs through a longitudinal oviposition slit starting at the front end of the egg. Conversely, in A. fraterculus the oviposition slit is located in the posterior third of the egg (Selivon et al, 1996). This fact suggests that oxygen demand may also be a factor considered at oviposition time, since the two species of fruit flies studied did not oviposit their eggs inside the citrus fruits (Table 2).…”

Haldane's rule and other aspects of reproductive isolation observed in the Anastrepha fraterculus complex (Diptera: Tephritidae)

“…Besides possible problems in the development of the hybrid eggs due to failure of genome adjustment, the decrease in egg hatching may also be related to cytoplasmic incompatibility. Selivon et al (1996) reported that eggs of A. fraterculus (now recognized as sp. 2) harbor a large population of symbiontic bacteria, which seems to be present also in the eggs of A. fraterculus sp.…”