Early development of zooxanthella-containing eggs of the corals Pocillopora verrucosa and P. eydouxi with special reference to the distribution of zooxanthellae

Abstract

Some hermatypic corals spawn eggs that contain zooxanthellae. We followed development of zooxanthella-containing eggs of two such species, Pocillopora verrucosa and P. eydouxi. We also documented changes in the distribution pattern of zooxanthellae during development. Oocytes of both species took up zooxanthellae 3 to 4 days before spawning. At first, zooxanthellae were evenly distributed in oocytes, but they later moved to the hemisphere that contained the germinal vesicle. After fertilization, early cleavage events were holoblastic, progressing by furrow formation. The first cleavage furrow started at the hemisphere that contained zooxanthellae, dividing the zooxanthellate complement of the zygote about equally into the two blastomeres. The second division divided each blastomere into one zooxanthellae-rich cell and one with few zooxanthellae. With continued cell division, blastomeres containing zooxanthellae moved into the blastocoel. The blastocoel disappeared at about 5 h after the first cleavage, and the central region of the embryo was filled with cells containing either zooxanthellae or lipid droplets, forming a stereogastrula. Our results suggest that only blastomeres that had been determined to develop into gastrodermal cells receive zooxanthellae during cleavage. This determination appears to take place, at the latest, by the second cell division at the four-cell stage.

Microbial aggregates within tissues infect a diversity of corals throughout the Indo-Pacific

“…For example, there was no evidence of vertical transmission of bacteria in the gonads or larval stages of 7 coral species in the Caribbean (Sharp et al 2010); however, internalized bacterial cells were seen in Porites asteroides larvae, suggesting vertical transmission (Sharp et al 2012). Similarly, symbiotic zooxanthellae within scleractinian corals are transmitted both vertically (Hirose et al 2000) and horizontally (van Oppen 2004), depending on the coral species.…”

Spatial and Species Variations in Bacterial Communities Associated with Corals from the Red Sea as Revealed by Pyrosequencing

“…Intrinsic factors may include the vertical transmission of microbial symbionts from parent to daughter cells (26,28,29,71) and the selective acquisition of microbes from the surrounding environment by defined mechanisms in corals at different developmental stages (2,4,28), leading to coral-species-dependent microbial consortia (62,64,65). External factors, such as temperature, elevated nutrient levels, dissolved organic carbon load, and reduced pH, can create stressful conditions that change coralassociated microbial communities (78).…”

Reduced reproductive success in scleractinian corals that survived the 1998 bleaching in Okinawa

“…Here we report preliminary observations on gamete production, the percentage of colonies which spawned gametes, and the fertilization rate of two scleractinian corals, Montipora digitata and Pocillopora verrucosa during the reproductive season following the 1998 bleaching. Both species are hermaphroditic spawners and release zooxanthella-containing eggs (Hirose et al 2000). While most colonies of P, verrucosa at our collection site died after the 1998-bleaching event, colonies of M, digitata survived, even in shallow waters.…”

“…We have been studying early development of zooxanthella-containing eggs of scleractinian corals belonging to the genus Pocillopora since 1997 (Hirose et al 2000), and studying the incorporation of zooxanthellae into oocytes of Montipora species since 1995 (Hirose et al, in preparation). During the 1999 reproductive season, we tried to observe the early development of Pocillopora verrucosa and Montipora digitata.…”