Genetic relationship and maturity state of the allorecognition system affect contact reactions in juvenile Seriatopora corals

Abstract

Adult stony corals are characterized by a well-developed allorecognition system. In most cases, genetically identical coral grafts fuse, whereas genetically different grafts (allografts and xenografts) show various histoincompatible responses. Very little is known, however, about the allorecognition system in juvenile corals. We studied contact reactions of juvenile pairs in 2 scleractinian coral species: Seriatopora caliendrum and S. hystrix (0 to 59 d after settlement). Juvenile colonies were experimentally grafted in combination groups of various genetic distances: sibling allografts of S. hystrix (4 pairs), non sibling allografts of S. caliendrum (12 pairs), non sibling allografts of S. hystrix (16 pairs) and xenografts of the 2 species (26 pairs). Three tissue contact reactions were detected in all of the genetic combination groups: nonfusion, fusion and incompatible fusion. The transition in contact reaction patterns was recorded over a 1 yr period. Contact reactions and their duration were largely consistent among pair replicates of each combination and within each of the 4 genetic combination groups. We suggest that in juvenile Seriatopora corals, the genetic combination of each graft is a primary determinant of the contact reaction and its endurance. Maturity state of the allorecognition system, affects both onset and duration of the fusion and incompatible fusion reactions in the juvenile corals. Onset of the fusion reaction was observed only when grafted colonies were younger than 4 mo. Throughout the experimental period, most fusion reactions transformed into histoincompatible reactions or disconnection and virtually none of the allografts or xenografts maintained stable chimeras. We suggest that as the alloimmune system matures, incompatible fusion reactions eventually transform into nonfusion or disconnection via tissue necrosis of the contact zone.

Mounting of erratic histoincompatible responses in hermatypic corals: a multi-year interval comparison

“…A comparable phenomenon was described in S. pistillata and was termed transitory fusion (Amar et al, 2008). In contrast to the Stylophora characteristic outcomes of this study [as in Frank et al (Frank et al, 1997)], alloreactions between pairs of siblings or nonsibling partners of P. damicornis, Seriatopora caliendrum and Seriatopora hystrix (Hidaka et al, 1997;Nozawa and Loya, 2005) were not affected by the partners' age.…”

“…Fusion between conspecifics is not restricted to corals and is commonly found even in hydrozoans Cadavid et al, 2004). Fusion between juveniles of scleractinian corals (the formation of chimeric entities) were first detailed by Hidaka (Hidaka, 1985) in Pocillopora damicornis and then in other pocilloporid corals like Stylophora pistillata (Frank et al, 1997), Seriatopora caliendrum and Seriatopora hystrix (Nozawa and Loya, 2005). Histocompatible outcomes in corals may further reveal variable outcomes with time.…”

Do reef corals age?

“…These include the establishment of associations with endosymbiotic algae (where transmission is horizontal and not via the parent) (Little, van Oppen & Willis, 2004;Voolstra et al, 2009) and micro-organisms (Sharp et al, 2010;Apprill et al, 2012;Sharp, Distel & Paul, 2012), and the development of immunity and allorecognition systems (Frank et al, 1997;Nozawa & Loya, 2005;Puill-Stephan et al, 2012). Physiological changes continue to be made as corals develop from juveniles to adults and through adulthood with the following examples relating to both ramets and genets, depending on the study.…”

Intracolonial genetic variation in the scleractinian coral Seriatopora hystrix

“…Examples come from plants and colonial marine animals such as red algae (Monro and Poore 2009), sponges (Maldonado 1998), bryozoans , hydroids (Shenk and Buss 1991;Hart and Grosberg 1999), ascidians (Sommerfeldt and Bishop 1999;Ben-Shlomo et al 2001;Sommerfeldt et al 2003) and corals (Frank et al 1997; Barki et al 2002;Nozawa and Loya 2005;Amar et al 2008;Puill-Stephan et al 2009). Enhanced performance due to either increased organism size or a more diverse genetic 'repertoire' is commonly cited as a possible benefit of chimerism that could favor cooperation rather than conflict and so allow chimeric entities to persist in nature (Pineda-Krch and Lehtilä 2004; Amar et al 2008).…”