2.2. THE CASE STUDIES
growth ratios within newly formed dichotomous UGBs differ significantly
from older branches, further emphasizing the within-colony genetic background for spatial configuration (Rinkevich 2000). In addition to the UGBs
many lateral, inside, and outside branches (LBs; Figs. 2.39a and d, Fig. 2.40)
are formed. LBs facing out of the colony elongate similarly to UGBs, further
adding lateral volume to the sphere-like structure (Loya 1976) of the colony.
LBs facing the internal volume of the colony are developed from different
zones along UGBsand it would be predicted that after prolonged elongation,
LBs would encounter and fuse with UGBs. However, such fusing (anastomosis) was never observed in unharmed colonies growing either in the field
(Rinkevich and Loya198sa) or in the laboratory. The decrease in growth rates
of internal LBs,the change of growth directions of isolated branches that are
put in close contact with each other (Rinkevich and Loya 198sa, Fig. 2.39d),
the lack of fusion between branches of a typical S. pistillata colony, and the
retreat growth occasionally recorded between closely growing branches of
allogeneic colonies (Rinkevich and Loya 1985b, Figs. 2.3ge and f, Fig. 2.40)
indicated the possible appearance of chemical signals ("isomone") carrying
biological activities that control growth patterns (Rinkevich and Loya198sa).
Several physiological characteristics of S. pistillata colonies also add to
the "holism" claim. A short-term follow-up study of photosynthetic products within the coral tissue revealed that the area of the branch tip (the
upper O.Sem) contains significantly less photosynthates than lower parts.
In contrast to general belief, long-term observations have further excluded
the possibility of a regular significant translocation of photosynthates along
a branch, from branch bases to the tips (Rinkevich and Loya1983a). This conclusion is also demonstrated by the fact that illumination of a branch base
by an optic glass fiber resulted in accumulation of photosynthates in the illuminated zone and in non-upward translocation of materials, at least for 29 h
post-incubation (Rinkevich and Loya 1984).
Translocation of photosynthates was however recorded when S. pistillata colonies were grafted with allogeneic 14C-labelled branches. The host
colonies translocated the labelled photosynthates towards the regenerating
portions (Rinkevich and Weissman 1987), probably through the gastrovascular canals that connect different polyps (Fig. 2-40). Some of the daily fixed
metabolites are stored for future use. For example, planula-larvae collected
1-7 months after coral tissue was labelled with 14Cwere found to contain significant amounts of labelled photosynthates (Rinkevich 1989). In the same
way photosynthetically fixed products of a specific single day were found to
contribute to newly formed tissues months after labelling (Rinkevich 1991), or
were contributed towards reproductive activities and the use of symbiotic invertebrates residing between the branches of S.pistillata colonies (Rinkevich
et al. 1991).
Reproductive activities are also developed and shaped at the colony level.
Onset of reproduction in S.pistillata colonies is at the age of about 2-3 years.
In the first year of reproduction the vast majority of the population contains
male gonads only, and with the increase in size, there is a tendency to an increase in the percentage of hermaphroditic colonies within the population
(Rinkevich and Loya1979).A long-term study on mature colonies in the field
revealed that sexuality (reproductive state) and/or fecundity could be completely altered from one reproductive season to the next (Rinkevich and Loya
1987). In all cases, however, synchronization in breeding was recorded over
65
growth ratios within newly formed dichotomous UGBs differ significantly
from older branches, further emphasizing the within-colony genetic background for spatial configuration (Rinkevich 2000). In addition to the UGBs
many lateral, inside, and outside branches (LBs; Figs. 2.39a and d, Fig. 2.40)
are formed. LBs facing out of the colony elongate similarly to UGBs, further
adding lateral volume to the sphere-like structure (Loya 1976) of the colony.
LBs facing the internal volume of the colony are developed from different
zones along UGBsand it would be predicted that after prolonged elongation,
LBs would encounter and fuse with UGBs. However, such fusing (anastomosis) was never observed in unharmed colonies growing either in the field
(Rinkevich and Loya198sa) or in the laboratory. The decrease in growth rates
of internal LBs,the change of growth directions of isolated branches that are
put in close contact with each other (Rinkevich and Loya 198sa, Fig. 2.39d),
the lack of fusion between branches of a typical S. pistillata colony, and the
retreat growth occasionally recorded between closely growing branches of
allogeneic colonies (Rinkevich and Loya 1985b, Figs. 2.3ge and f, Fig. 2.40)
indicated the possible appearance of chemical signals ("isomone") carrying
biological activities that control growth patterns (Rinkevich and Loya198sa).
Several physiological characteristics of S. pistillata colonies also add to
the "holism" claim. A short-term follow-up study of photosynthetic products within the coral tissue revealed that the area of the branch tip (the
upper O.Sem) contains significantly less photosynthates than lower parts.
In contrast to general belief, long-term observations have further excluded
the possibility of a regular significant translocation of photosynthates along
a branch, from branch bases to the tips (Rinkevich and Loya1983a). This conclusion is also demonstrated by the fact that illumination of a branch base
by an optic glass fiber resulted in accumulation of photosynthates in the illuminated zone and in non-upward translocation of materials, at least for 29 h
post-incubation (Rinkevich and Loya 1984).
Translocation of photosynthates was however recorded when S. pistillata colonies were grafted with allogeneic 14C-labelled branches. The host
colonies translocated the labelled photosynthates towards the regenerating
portions (Rinkevich and Weissman 1987), probably through the gastrovascular canals that connect different polyps (Fig. 2-40). Some of the daily fixed
metabolites are stored for future use. For example, planula-larvae collected
1-7 months after coral tissue was labelled with 14Cwere found to contain significant amounts of labelled photosynthates (Rinkevich 1989). In the same
way photosynthetically fixed products of a specific single day were found to
contribute to newly formed tissues months after labelling (Rinkevich 1991), or
were contributed towards reproductive activities and the use of symbiotic invertebrates residing between the branches of S.pistillata colonies (Rinkevich
et al. 1991).
Reproductive activities are also developed and shaped at the colony level.
Onset of reproduction in S.pistillata colonies is at the age of about 2-3 years.
In the first year of reproduction the vast majority of the population contains
male gonads only, and with the increase in size, there is a tendency to an increase in the percentage of hermaphroditic colonies within the population
(Rinkevich and Loya1979).A long-term study on mature colonies in the field
revealed that sexuality (reproductive state) and/or fecundity could be completely altered from one reproductive season to the next (Rinkevich and Loya
1987). In all cases, however, synchronization in breeding was recorded over
65