Abiotic (Component or Factor) – Non-living chemical and physical parts of an environment that affect living organisms and the function of an ecosystem

Absorbance (D) – Measure of the capacity of e.g., chlorophyll to absorb light of a specific wavelength 

Absorption/Absorptance (A) – Light fraction absorbed 

Adaptation – The products of natural selection by which an organism may become better suited to its environment for a specific function(s) 

Adaptive – Having the capacity for adaptation (above) 

Adaptive plasticity – Where plasticity is considered beneficial and maintained by selection 

Additive genetic variance (VG,A) – Deviation from the population mean phenotype due to additive allele effects (substituting one allele for another) at a given locus or the multiple loci of a polygenic trait (below) 

Anastomose – Forming a network (in the context of colony morphology) 

Anthocodia – The distal part of a polyp, bearing the mouth and tentacles; can be retracted within the calyx, stem, branch or cortex 

Anthostele (Calyx) – The proximal, rigid part of polyps in some octocoral species, often stiffened by sclerites. In some cases the anthocodia is withdrawn into the anthostele 

Arborescent – Tree-like colonies possessing a stem 

Axial sheath – Part of the colonial coenenchyme immediately surrounding the axis, usually delimited by the longitudinal stem canals and characterised by sclerites commonly different in form from those of the overlying coenenchyme 

Axis – Central, longitudinal supporting structure which can consist of either, 1) an inner central horny (gorgonin) chord with or without calcareous material (loculi), 2) scleritic inner medulla and outer coenenchyme, or 3) non-scleritic central axis which may be hollow or cross-chambered 

Axis cortex (Cortex) – Tissue layer surrounding the central part of the axis; either the coenenchyme surrounding the medulla or the horny layer surrounding the central chord 

Biotic (Component or Factor) – A living organism that affects another organism and/or it's environment 

Bushy – Colonies with abundant branches typically in all directions 

Canal (Longitudinal) – Longitudinal partitions of the gastrovascular cavity of the polyp running longitudinally along the central axis, often nested within axial groves 

Canalisation – The reduced sensitivity (sensu fixed) of a phenotype to changes or perturbations in the underlying genetic and nongenetic factors that determine its expression 

Capstan – Sclerite: rod with two whorls of tubercules or wards and terminal tufts 

Central chord (Core) – The central part of a Holaxonian axis, consisting solely of horny material or horny material with varying permeations of calcareous material (loculi). Can be hollow and cross-chambered in some families (see Medulla) 

Club – Monaxial (single axis) sclerites enlarged at the head, and tapered at the opposite end, the handle 

Coenenchyme – The colonial soft tissue between the polyps, consisting of the mesoglea usually containing sclerites and penetrated by the network of solenia and gastrodermal canals 

Cortex – Tissue layer surrounding the central part of the axis; either the coenenchyme surrounding the medulla or the horny layer surrounding the central chord. 

Cross – Stellate sclerite with four rays in a single plane 

Crown (Collaret) – The ring of transversely placed, usually bow-shaped sclerites encircling the anthocodia below the tentacles 

Diving-PAM – A diving-pulse amplitude modulation fluorometer measuring the effective quantum yield (Φ) of photochemical energy conversion during photosynthesis

Dominant genetic variance (VG,D) – Deviation from the population mean phenotype due to interactions between alleles at the same locus 

Dumb-bell – Sclerite with two nearly spherical, warty heads and a distinct waist that is longer than in the double sphere 

Ecology – A branch of biology that studies the relationships of organisms with their physical and biological environment

Ecosystem – An ecological unit that consists of the environment and it's biotic and abiotic components that exist in and affect it  

Encrusting – Colony morphology consisting of a thick fleshy layer covering the substrate 

Environmental variance (VE) – Phenotypic variance among individual members of a population due to environmental effects 

Epigenetic – Resulting from external rather than genetic influences, whereby modification in gene expression/function are independent of the DNA sequence. Epigenetic influences can become heritable and fixed (through genetic assimilation) over time 

Epistatic interaction variance (VGI) – Genetic variance due to epistasis (below) 

Epistasis – The expression of a gene is modified by the presence of one or more ‘modifier genes’ from different loci. 

Evolutionary capacitance – The storage and release of genetic information (variation), typically leading to fixation through genetic assimilation as a consequence of epigenetic heritability 

Flabellate – Fan-shaped (arborescent) 

Gastric cavity (Gastrovascular cavity; Coelenteron) – Interior space of a polyp 

Gastrodermal canals – Wide, endodermal-lined canal connected with the narrower solenia and originating from them 

Genetic accommodation – A process where a phenotype is originally produced in response to either a mutational or environmental stimulus (genetic assimilation in the latter; below) 

Genetic assimilation – A process where a phenotype originally produced in response to environmental change later becomes genetically encoded typically through epigenetic heritability. Sensu stricto process of phenotypic evolution by genetic accommodation (above) 

Genetic variance (VG) – Phenotypic variance among individual members of a population due to genetic effects 

Genetic and environmental interaction variance (VGxE) – Genotype by environment interaction whereby genotypes differentially respond to their environment 

Gonads – Reproductive cells along the septa within the gastrovascular cavity 

Gorgonin – Horny proteinaceous material forming with calcareous (loculi and/or sclerites) material of the inner and/or outer layers of the central axis 

Hermatypic – Reef-building corals, typically depositing aragonite structures contributing to or the basis of coral reef development e.g., most Scleractinian corals 

Holobiont – Biological unit including the host and its microbial associate communities 

Integration – Characters (phenotypic traits or modules) behaving as a unit with integration manifested as coordinated character change in ontogeny, phylogeny, space, time, magnitude or direction 

Internode – Hard, calcareous segment of the jointed axis (e.g., Melithaeidae, Isididae) 

Intraspecific variation – Any differences among individuals of a single species. 

ITS2 cladal type – Genetic variant of the ITS2 region below that of a clade and currently unresolved taxonomically 

Loculi (Loculus) – Calcified or fibre-filled space in the holoxonian axis, especially in Plexauridae, appearing crescentic or lenticular in cross section 

Medulla – Central supporting structure of the Scleraxonia consisting of densely packed sclerites, gorgonin and occasional longitudinal canals. Surrounded by the coenenchyme (see Axis, Central Chord) 

Mesenteries (Septa/um) – Eight thin, radial and longitudinal, non-calcareous partitions joining the pharynx to the body wall and dividing the polyp gastrovascular cavity. Each septum bears a longitudinal retractor muscle 

Mesenteries filaments (Septal filaments) – The thickened convoluted edges of the mesenteries (septum) below the pharynx. The two mesenteries opposite the siphonoglyph are long and heavily flagellated 

Modularity – Degree to which a system’s components can be separated and recombined; thus organisms are considered to consist of phenotypic modules 

Monophyletic – A group of organisms descended from a common evolutionary ancestor or ancestral group, particularly one that is not shared with any other group 

Multiplanar - Branched colonies in which the branches grow in several planes 

Neck zone (Introvert) – Soft, thin-walled basal section of the anthocodia below the tentacles bearing little or no sclerites. Permits introversion of the anthocodia into the anthostele (calyx) 

Node – The flexible horny (gorgonin) segment of a jointed axis (see internode) 

Oral disc – Area of the polyp immediately surrounding the mouth and formed by the inner basal parts of the tentacles 

Particulates – Class of seawater constituents that consist of organic matter, inorganic skeletal remains, and terrigenous dusts 

Pharynx – Tubular section of the digestive system connecting the mouth and the gastrovascular cavity; possesses one or two flagellated grooves (siphonoglyphs) 

Phenotype – The set of observable traits of an individual due to its interaction of its genotype with the environment 

Phenotypic plasticity – Environmentally induced changes in an organism’s phenotype within its lifetime; a specific form of intraspecific variation (see above) 

Phenotypic variance (VP) – Variance within a quantitative phenotypic trait (see additive, dominant, epistatic, genetic, environmental, and genetic and environmental interaction) 

Polyphyletic – A group of organisms derived from more than one evolutionary ancestor or ancestral group, therefore not suitable for placing in the same taxon 

PSII – Photosystem II (two); a photosystem reaction centres/protein complex that uses light energy for the splitting of water through oxidation in photosynthesis 

Pinnules – The lateral, hollow processes arranged in two opposite rows along each tentacle 

Planar – Arborescent branching colonies where branches generally grow in a single plane 

Plasticity - Environment-dependent phenotype expression 

Pleiotropy – The influence of a single gene on several seemingly unrelated phenotypic traits 

Point(s) – Eight longitudinal rows of chevroned sclerites around the distal part of the anthocodia, superposing the crown if present 

Polygenic – Phenotypic trait controlled or the product of two or more genes and its environment (see additive genetic variance) 

Polyp (Zooid) – Any individual within a (octocoral) colony, which may be monomorphic (possess single polyp type) or consist of more than one type e.g., autozooids and siphonozooids (e.g., Coralliidae) 

Polyphenic trait (Polyphenism) – A trait which gives rise to multiple, distinct phenotypes from a single genotype due to differential environmental conditions 

Radiates – Sclerites with symmetrically radiating processes in a single or multiple planes 

Reaction norms (Norms of reaction) – A single genotypes phenotypic expression as a function of environmental variation 

Reticulate – Branching colonies where branches anastomose forming net-like structures 

Sclerite – Calcareous skeletal element present in or on the Octocoral soft tissue matrix or axial composition 

Septa (Septum, Mesenteries) – Eight thin, radial and longitudinal, non-calcareous partitions joining the pharynx to the body wall and dividing the polyp gastrovascular cavity. Each septum bears a longitudinal retractor muscle 

Sessile – Not mobile/immobile; fixed in a single place directly by it's base 

Siphonoglyph (Sulcus) – Strongly ciliated groove extending down one side of the pharynx 

Solenia (Solenium) – Narrow endodermal canal lined with gastrodermis within the coenenchyme, forming a network by interconnecting the gastric cavities of the polyps and larger canals 

Spicule – Skeletal element of non-cnidarian taxa (e.g., Porifera), often confused with sclerite 

Spindles – Monaxial (single axis) sclerites that are straight or curved and pointed at both ends 

Symbiodinium Freudenthal 1962 (Zooxanthellae) – Unicellular dinoflagellate free-living or endosymbiotic alga. The largest group of endosymbiotic dinoflagellates 

Synapomorphic – Of a character trait that evolves once in the common ancestor (and not in its ancestors) of two or more lineages, themselves possibly exhibiting further modified versions of that trait 

Residual components [Verror] – Phenotypic variance accounted for by developmental noise, bet-hedging, behavioural or other unaccountable factors 

Zooxanthellar/e (Symbiodinium) – Colloquial name for Symbiodinium Freudenthal 1962 


Glossary Bibliography 

Bayer FM, Grasshoff M, Verseveldt I eds. (1983) Illustrated trilingual glossary of morphological and anatomical terms applied to Octocorallia. E. 1. Brill/Dr. W. Backhuys, Leiden. pp.75, 20 pls. 


DeWitt TJ, Scheiner SM. (2004) Phenotypic variation from single genotypes. In: Phenotypic Plasticity: Functional and conceptual approaches (eds. DeWitt TJ, Scheiner SM), pp. 1-9. Oxford University Press, New York. 


Gotthard K, Sören Nylin S. (1995) Adaptive Plasticity and Plasticity as an Adaptation: A Selective Review of Plasticity in Animal Morphology and Life History .Oikos, 74(1): 3-17. 


Hageman SJ, Bayer MM, Todd CD. (1999) Partitioning phenotypic variation: genotypic, environmental and residual components from bryozoan skeletal morphology. J. Nat. Hist. 33(11): 1713-1735 


Johnson C. (1976) Introduction to natural selection. University Park Press, Baltimore. pp. 213 


Neuendorf KK, Mehl Jr JP, Jackson JA. (2005) Glossary of geology 5th edition. Alexandria, Verginia, pp. 779


Roth LV. (1996) Cranial Integration in the Sciuridae. Amer. Zool. 36: 14-23 


Stachowitsch M. (1992) The invertebrates: an illustrated glossary. Wiley-Liss, Inc., New York. pp. 676 


West-Eberhard MJ. (2003) Developmental Plasticity and Evolution. Oxford Univ Press, New York.