Serosa ontogeny in two embryonic morphs of Copidosoma floridanum: The influence of host hormones

Abstract

The embryos of 2 larval morphs of the insect parasitoid Copidosoma floridanum (Ashmead) (Hymenoptera: Encyrtidae) were readily distinguished on the basis of temporal and morphological characters. Although larvae of the 2 morphs differed in morphology and timing of hatch, both morphs derived a serosal membrane just prior to embryonic morphogenesis. Nuclei of the serosa increased in diameter and ploidy during development. Serosa polyploidy was similar in both morphs a t identical stages of morphogenesis. Host endocrine perturbations that blocked C. floridanum morphogenesis also affected serosa development. Serosa ontogeny was blocked when the host was ligated at 7 h of the 4th stadium. Daily application of the juvenile hormone analogue methoprene starting at 20 h of the host's 3rd stadium resulted in serosal nuclei with greater diameters and ploidy values than those of untreated embryos. Treatment of the host with methoprene beginning a t 20 h of the 3rd stadium followed by ligation at 7 h of the 4th stadium arrested serosa ontogeny and embryonic growth of the parasitoid. These data indicate that embryos of both morphs of C . floridanurn formed a serosa just prior to morphogenesis and that serosa ontogeny required host head factors. Furthermore, host juvenile hormone did not influence serosa ontogeny but stimulated polyploidy of membrane nuclei. o 1992 Why-Liss, Inc

Transplantation of a polyembryonic wasp embryo: a technique for transferring endoparasitic embryo into the host egg

“…Our transplanted embryos (Fig. 5c) produced a number of adults (t=0.56; P=0.58) similar to that of T. ni eggs parasitized by C. floridanum that were collected in nature (Grbic et al 1992). These wasps were viable and able to mate and produce progeny.…”

“…Collected egg sheets were exposed to parasitic wasps in a 1:3 egg/wasp ratio, oviposition events were observed, and the parasitized eggs were marked with a pencil. After 10 min of oviposition, unparasitized eggs were destroyed, then parasitized egg sheets were briefly washed in 0.1% bleach solution, dried, and placed in 10-cm plastic cups that contained an artificial diet (Baehrecke et al 1992). Inverted cups (diet on top) were placed in a Percival incubator with a temperature of 27°C (16 h light/8 h dark photoperiod).…”

Compatible invasion of a phylogenetically distant host embryo by a hymenopteran parasitoid embryo

“…An extra-embryonic syncytium has been reported in all polyembryonic and some monoembryonic parasitic wasps, where it plays an important role in the uptake of nutrients from the host (Baehrecke et al 1992;Trenblay and Caltagirone 1973;Strand 1986;Koscielski and Koscielska 1985). The extra-embryonic syncytium produced by polyembryonic wasps is derived from embryonic polar bodies and is essential for the compartmentation of the morula by invaginating into the embryonic cell mass to form the polymorula (Baehrecke et al 1992), for the protection of larvae from any host immune responses (Corley and Strand 2003), and for anchoring the embryo to host tissues (Strand and Grbic 1997). This kinetic property of the extra-embryonic syncytium may be also involved in the active invasion of the morula into the host embryo.…”

“…One or two eggs are laid in the host egg during any stage of development (Ode and Strand 1995). The parasitoid egg cleaves nearly holoblastically to form a morula, which is a spherical mass of embryonic cells surrounded by an extra-embryonic syncytium (Strand 1989;Iwabuchi 1991;Baehrecke et al 1992;Grbic et al 1998). The embryo proliferates clonally in the growing host larva and produces as many as 2000 embryos Baehrecke et al 1993;Utsunomiya and Iwabuchi 2002).…”

An ultrastructural study of polyembryonic parasitoid embryo and host embryo cell interactions

“…Copidosoma floridanum (Hymenoptera: Encyrtidae) is a polyembryonic egg-larval endoparasitoid of the plusiine Lepidoptera, in which one or two eggs are deposited into a host egg during any stage of its development (Ode and Strand, 1995). The C. floridanum egg subsequently cleaves nearly holoblastically to form a spherical mass (termed a morula) of embryonic cells surrounded by an extraembryonic syncytium (Strand, 1989;Iwabuchi, 1991;Baehrecke et al, 1992;Grbic et al, 1998). Our previous study demonstrated that C. floridanum is able to enter a host embryo not only by laying eggs directly into it but also by invasion of the morula-stage embryo (Nakaguchi et al, 2006).…”