Coral Anatomy and Histopathology Terms
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A / B /
C / D / E / F / G / H
/ I / K /
L / M / N / O / P / R
/ S / T /
V / Z
A
Aboral – region of polyp directly
opposed to, away from, or remote from the mouth; the terms
Basal or Proximal can also be used
to describe this region. (Dorland 2006)
Acrosphere – globular tip of scleractinian
tentacle, containing numerous nematocytes.
(Fautin 2005)
Actinopharynx (preferred term; synonyms – stomodaeum, pharynx)
– invagination of the epidermis to form
a short muscular tubular passageway between the mouth and gastric cavity in a polyp,
mostly lined with flagellated supporting cells. (Fautin 2005; Peters 2001)
Acute – exposure to a pathogen or a health effect that is brief,
intense, short-term, or severe. The terms acute and subacute as they refer to pathology
in coral are not currently precise enough to apply to cellular/microscopic changes
and these terms as they are used in the current document will refer only to colony-level
(gross) observations. (Stedman 1995)
Amoebocyte – a cell possessing
pleomorphic form and high elasticity, the principal cellular defense element
of Cnidaria and typically found in the mesoglea.
Granular amoebocytes contain small, dense, acidophilic granules in the cytoplasm,
may secrete collagen fibers or sclerites, phagocytize and digest particulate matter,
or differentiate into other cell types. (Fautin and Mariscal 1991)
Amphophilic – having an affinity both for acid and basic dyes.
(Pharma 2006)
Anthocodia (plural Anthocodiae) – the
distal part of an octocorallian polyp,
bearing the mouth and tentacles. (Bayer et al. 1983)
Anthostele (= Calyx) – the rigid
part of polyps seen in some species of octocorals, often stiffened by sclerites, and into which the anthocodia may be withdrawn.
(Bayer et al. 1983)
Antipathin – a material composed of proteins and chitin
that forms the axis in an antipatharian (black
coral). (Goldberg 1976)
Apical – opposite of basal,
situated near the apex or tip of a structure, as in the apical portion of a cell.
(Stedman 1995)
Apoptosis (a form of programmed cell death) – a morphologic pattern
of cell death formation of cytoplasmic blebs, and fragmentation of the cell into
membrane-bound affecting single cells, marked by shrinkage of the cell, condensation
of chromatin, apoptotic bodies that are phagocytosed by other cells. (Dorland 2006;
Stedman 1995)
Aragonite – mineral variation of calcium carbonate (CaCO3) with
a crystal structure different from the other two forms of CaCO3, vaterite and calcite.
It is formed mainly by marine organisms (e.g., coral) that use it to make their
shells and skeletons. (Coris 2006)
Atrophy – diminution of tissues, organs, or entire body, as from
death and reabsorption of cells, diminished cellular proliferation, decreased cellular
volume, malnutrition, or lessened function. (Stedman 1995)
Attenuated – thinned or weakened, cause unknown. (Stedman 1995)
Autolysis – lysis, enzymatic
digestion, of cells by the enzymes present within them. (Stedman 1995)
Axial Polyp – the longest polyp of a group of polyps, which produces
secondary (daughter) polyps by lateral budding from its body wall. (Bayer et al.
1983)
Axial Sheath – that part of the colonial coenenchyme immediately surrounding the axis in the
octocoral taxa Gorgonacea and Pennatulacea, containing the longitudinal canals and
characterized by sclerite commonly different
in form from those of the overlying coenenchyme. (Bayer et al. 1983)
Axis – inner supporting structure of Gorgonacea and Pennatulacea.
It is usually composed of collagen (see Gorgonin);
however, the antipatharian (black coral) axis consists of different proteins and
chitin (see Antipathin). The axis can
be mineralized in some groups, usually by magnesium calcite (as in sclerites), but in some, the mineral in the axis is aragonite and amorphous hydroxyapatite also occurs
in some axial skeletons. (Bayer et al. 1983; Bayer and Macintyre 2001; Goldberg
1976; Holl et al. 1992)
Axis Cortex – layer around the
central chord or core of the axis, deposited by an axis epithelium. (Bayer
et al. 1983)
Axis Epithelium – layer of cells derived from ectoderm consisting of two types of cells: corticocytes (cells that produce the axis) and desmocytes (cells that attach the octocoral tissues
to the axis). (Bayer et al. 1983)
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B
Basal - situated near the base of a structure in relation to a
specific reference point, opposite of apical.
(Stedman 1995)
Basal Plate – aragonite
structure built by the polyp at the bottom or
base of the skeletal cup (corallite)
enclosing a scleractinian polyp. (Stachowitsch 1992)
Basophilic – denoting components of cells having an affinity for
basic dyes under specific pH conditions. Basophilic compounds (e.g., nucleic acids)
stain blue with hematoxylin in the 'hematoxylin and eosin' (H&E) staining procedure.
(Pharma 2006)
Bleaching - the loss or expulsion of symbiotic dinoflagellates
(Symbiodinium spp.) by corals; can be caused by various stressors, including increased
temperatures (Hoegh-Guldberg et al. 2007) and toxins produced by bacterial pathogens
(Rosenberg and Falkovitz 2004). During temperature-induced bleaching, caspase-mediated
apoptosis and autophagy are reciprocally activated to expel the dinoflagellate symbionts
(Dunn et al. 2007). (Teplitski and Ritchie 2009)
Body Wall – the three layers of tissues (epidermis,
mesoglea,
gastrodermis) that form the surfaces of the polyp,
enclosing the gastrovascular
cavity and, in colonial corals, the
gastrovascular canals. (Bayer et al. 1983; Goldberg 2002b)
-
Surface Body Wall – in contact with seawater, covering the coenenchyme, tentacles,
oral disk,
peristome, and polyp neck zone and anthostele
(octocoral) or column (hexacoral).
-
Basal Body Wall – the
calicodermis*, mesoglea, and gastrodermis that covers the exoskeleton
of the scleractinian coral, surrounding the gastrovascular cavity and canals.
-
Actinopharynx Body Wall – the specialized (heavily ciliated or flagellated)
epidermis, mesoglea, and gastrodermis that forms the
actinopharynx.
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C
Calice – the upper open or oral
surface of the corallite. (Peters 1984)
Calicoblast – primary cell type of the calicodermis* that
secretes the organic matrix involved in calcification and formation of the skeleton
in the scleractinians. (Puverel et al. 2005)
Calicodermis* (= Calicoblastic Epithelium) – the thin
but complex layer of ectodermally derived cells around a scleractinian polyp whose primary function is building the exoskeleton.
In a colonial coral, as new polyps are formed, the calicodermis continues as the
cell layer immediately adjacent to the skeleton of the interconnecting gastrovascular canals in imperforate corals
and completely surrounds the gastrovascular canals embedded in the exoskeleton in
perforate corals. Most of the cells are modified to secrete an organic matrix that
may have a crucial role in the formation of aragonite
crystals to form the exoskeleton. These cells, currently referred to as calicoblasts,
do not form aragonite intracellularly. Other cells in the calicodermis are modified
to attach the tissue to the exoskeleton (see
Desmocyte). This epithelium
can also contain mucocytes, pigment cells, or amoebocytes, but usually lacks cnidocytes.
(Goldberg 2002b; Goldberg 2001a; Peters 1984, Coral Histopathology Workshop 2005)
Calyx (plural Calyces) – see
Anthostele
Central Chord or Core – the central part of the axis, made of gorgonin
alone, or gorgonin permeated with calcareous matter, sometimes hollow and cross-chambered,
not always present. (Bayer et al. 1983)
Chromophore Cell – amoeboid
cell containing cytoplasmic pigment granules in the scleractinian genus
Porites. The granules appear yellow to tan when stained with hematoxylin and eosin
using incandescent light microscopy and are bright green in unstained polyp sections when using a filter for green fluorescent protein
with epifluorescence microscopy. (Duerden 1902; Smith 2004)
Chronic – long-term exposure to a
pathogen or a prolonged health effect. The term chronic as it refers to
pathology in coral is not currently precise enough to apply to cellular/microscopic
changes and this term as used in the current document will refer only to colony-level
(gross) observations. (Stedman 1995, Coral Histopathology Workshop 2005)
Cilium (plural Cilia) – one of the motile extensions of the surface
of an epithelial cell containing nine longitudinal double microtubules made of structural
proteins arranged in a ring around a central pair. (Stedman 1995)
Cinclide – small opening or “soft spot” in the body wall through
which mesenterial filaments
can be extruded. (Fautin and Mariscal 1991)
Cnida (plural Cnidae) – a collagenous capsule that develops in
a cnidocyte and contains a tubule or thread that everts when triggered. There are
three types of cnidae: nematocysts,
spirocysts, or
ptychocysts. Cnidae are non-self-replicating organelles secreted by the
Golgi apparatus, and are the most complex secretory products in the animal kingdom.
(Hessinger and Lenhoff 1989; Mariscal 1984)
Cnidocyst – cnida. (Mariscal
1984)
Cnidocyte – epithelial cell that can produce a cnida in the Cnidarians,
see also Nematocyst and Spirocyst. (Mariscal 1984)
Cnidoglandular Band (or Lobe) – the
distal thickened rim or free along a mesentery.
It consists of the median band or tract of a
mesenterial filament containing nematocytes,
ciliated columnar or collar cells,
mucocytes, and granular gland (zymogen) cells, may have two
lateral lobes distal to the median lobe, consisting mainly of nutritive three types
of cnidae: nematocysts, spirocysts, or ptychocysts.
Cnidae are non-self-replicating organelles secreted by the Golgi apparatus, and
are the most complex secretory products in the animal kingdom. (Hessinger and Lenhoff
1989; Mariscal 1984)
Coccidian – a single-celled organism belonging to the protistan
Phylum Apicomplexa, characterized by merogony and a life cycle comprising both sexual
and asexual stages, parasitic in epithelial cells of invertebrates and vertebrates.
(Upton and Peters 1986)
Coenenchyme – the tissues between and continuous with the polyps in a colonial anthozoan, consisting of the surface body wall and gastrovascular canals found either on the surface of or penetrating
the skeleton (in hexacorals) or consisting of the surface body wall, gastrovascular
canals, and solenia penetrating through the
thick mesoglea stiffened with sclerites (in octocorals). The edge zone of the coenenchyme
is that portion extending outside the peripheral polyps at the edge of a colony
or outside the theca in a solitary coral. (Bayer
et al. 1983; Stachowitsch 1992)
Coenosteum – skeleton deposited outside and between the corallite walls of the polyps
of a colonial scleractinian. (Peters 1984; Stachowitsch 1992)
Collar Cell – specialized cell found in the epithelia of the mesenterial filament
and actinopharynx. Requires transmission
electron microscopy to distinguish its characteristic feature, a cilium with shallow
rootlet surrounded by fibril-linked microvilli, with small fibrous or lysosome-like apical
inclusions. (Goldberg 2002b)
Column – the body wall of an anemone, the cylindrical surface of
a polyp. In a scleractinian, that portion of the polyp
that can extend outside the calice. (Fautin
2005; Peters 1984)
Columella – column-shaped skeletal projection of the central basal plate or modified inner
septal edges, may be solid or not. (Peters 1984; Stachowitsch 1992)
Corallite – the skeleton deposited by an individual polyp within a colony. (Peters 1984, Acropora Biological Review
Team)
Corallum – the entire skeletal structure formed by either a solitary
(single corallite) or colonial (group
of corallites) coral. (Peters 1984)
Corticocyte – cell that produces
gorgonin and forms the axis in a gorgonian.
(Tidball 1982)
Costa – the extension of the septa outside the calice onto the
coenosteum. (Peters 1984)
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D
Degeneration – a nonspecific term applied to retrogressive but
sometimes reversible pathological change in cells or tissues, resulting in impairment
or destruction of functions; deterioration; preferably the specific changes observed
should be fully described. (Dorland 2006; Stedman 1995)
Desmocyte – anchoring cell of the
calicodermis* (scleractinian) or
axis epithelium (gorgonian), characterized by unique
apical and basal modifications
for attachment to skeletal surfaces and mesoglea
respectively. (Chapman 1974; Goldberg 2001b; Muscatine et al. 1997)
Diagnosis – the determination of the nature of a disease. (Stedman
1995)
-
Field Diagnosis – made from the study of the macroscopic changes
of a coral disease observed in the field.
-
Laboratory Diagnosis – made by a chemical, virological, parasitological,
microbiological, or immunological study of secretions, discharges, or tissues.
-
Morphologic Diagnosis – made from an anatomical or histological
study of the lesions present.
-
Etiologic Diagnosis – the determination of the cause of the disease.
-
Differential Diagnosis – a systematic comparison and contrasting
of similar disease signs and findings to determine which of two or more diseases
is considered to be most likely present in the organism, although one or more other
diseases are considered less likely to be present but possible. (See also Pathognomonic) A differential diagnosis is also made
to distinguish between closely related species in taxonomy.
Disassociation (or Dissociation) – a separation of relationships,
as in the separation of epithelial cells because of damage to the intercellular
junctions. (Stedman 1995)
Disease – any deviation from, or interruption of, the normal structure
or function of any body part, organ, or system that is manifested by a characteristic
set of signs and whose etiology, pathology, and prognosis may be known or unknown
(Dorland 2006); any impairment that interferes with or modifies the performance
of normal function, including responses to environmental factors such as nutrition,
toxicants, and climate; infectious agents; inherent or congenital defects, or combinations
of these factors. (Wobeser 1981)
Distal – that part of a structure situated away from the center
of or point of origin, the extremity or distant part of a limb or organ, e.g., distal
tentacle. For a polyp, the distal part is the oral end of the entire polyp. (Fautin
2005; Stedman 1995)
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E
Ectoderm – the outer layer of pluripotential cells in the embryo,
after establishment of the primary germ layers during the gastrula stage of development.
(Hyman 1940; Martindale et al. 2004; Stedman 1995 discussed the diploblastic versus
triploblastic nature of cnidarians)
Endocoel – the region of the
gastrovascular cavity between two mesenteries
belonging to the same pair; in the endocoel of nondirective mesenteries, the longitudinal
retractor muscles on the mesogleal
pleats of the two mesenteries protrude into the cavity; in the endocoel
of directive mesenteries,
the longitudinal retractor muscles on the mesogleal pleats are on the side of the
mesenteries so they do not protrude into the cavity. (Fautin 2005)
Endoderm (or Entoderm) – the inner layer of pluripotent cells in
the embryo, after establishment of the primary germ layers during the gastrula stage
of development. (Hyman 1940; Martindale et al. 2004; Stedman 1995 discussed the
diploblastic versus triploblastic nature of cnidarians)
Endolithic – growing within a rock or any other hard inorganic
substratum, e.g., coral skeleton. (Coris 2006)
Eosinophilic – cell or tissue elements staining readily with eosin
dyes, appear pink to red when using a hematoxylin and eosin staining procedure;
sometimes referred to as "acidophilic". (Pharma 2006)
Epidermis – external epithelium of coral
polyps and coenenchyme derived
from the ectoderm, may be composed of columnar
supporting cells (with apical specializations
such as microvilli, cilia, or flagella), ciliated sensory cells, mucocytes,
epitheliomuscular cells, cnidocytes,
pigment cells, neurons, amoebocytes.
The epidermis can be reduced in octocorals (supporting cells, sensory cells, cnidocytes,
scleroblasts, mucocytes, amoebocytes)
and may secrete a covering on basal parts of
octocoral colonies. (Fautin and Mariscal 1991; Hyman 1940)
Epitheliomuscular Cell – cnidarian cell in which the cell body
is columnar and the nucleus is situated in the basal
portion of the cell. It is joined to other epithelial cells in the epidermis or gastrodermis
and has elongated basal cytoplasmic extensions containing actin and myosin filaments,
known as muscle fibrils or myonemes. The
extensions are perpendicular to the cell body and attach to the surface of the mesoglea, facilitating polyp movement
and contraction. The apical surface of the cell
may have a flagellum. (Fautin and Mariscal
1991)
Epithelium – layer of cells covering both
ectodermally and endodermally derived
tissues of the polyp body and canals, bound together by various junctions and cementing
substances to provide strength and mediate the exchange of metabolic and messenger
molecules, and bound to and supported by basement membrane or basal lamina. (Dorland
2006; Stedman 1995)
Euchromatic (= Orthochromatic) – denoting any tissue or cell that
stains the color of the dye used, i.e., the same color as the dye solution with
which it is stained. (Pharma 2006)
Exocoel – the region of the
gastrovascular cavity between two mesenteries
belonging to different pairs. Except for the exocoels flanking the directive mesenteries, retractor muscles do
not protrude into an exocoel. (Fautin 2005)
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F
Filament – see
Mesenterial Filament
Flagellum (plural Flagella) – single, elongate motile structure
consisting of nine pairs of microtubules around two single central proteinaceous
microtubules extending from the apical surface of an epithelial cell or tail of
spermatozoan. (Stedman 1995)
Full Thickness (= Transmural)
– a lesion, wound, or process that involves all layers of a tissue: epidermis or calicodermis*,
mesoglea, and
gastrodermis. (Coral Histopathology Workshop 2005)
Fusiform – spindle-shaped, tapering at both ends, as in a fusiform
cell. (Stedman 1995)
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G
Gastric Cavity – see
Gastrovascular Cavity
Gastrodermal Canal – see
Gastrovascular Canal
Gastrodermis – the inner epithelium of a coral polyp derived from
the embryonic endoderm, lining the gastrovascular cavity and polyp-connecting
canals. Some cells in this epithelium are phagocytic
to digest food particles, absorb nutrients, and release waste products; zooxanthellae often reside within membrane-bound vacuoles in these cells. The gastrodermis may also contain
ciliated or flagellated supporting cells,
cnidocytes, amoebocytes,
sensory cells, mucocytes, and pigment cells. (Fautin and Mariscal 1991; Goldberg
2002a; Hyman 1940; Peters 1984)
Gastrovascular Canal – a system of tubes lined with gastrodermis that connect the gastrovascular cavities of colonial coral
polyps. The canals extend along the surface of the
coenosteum in all colonial scleractinians; in some species additional canals
extend from the gastrovascular cavities to penetrate through the coenosteum between
polyps, forming a porous or perforated skeleton. In the octocorals, the gastrovascular
canals are embedded in the mesoglea and connect to thinner canals called solenia. (Bayer et al. 1983; Peters 1984)
Gastrovascular Cavity – the interior space of a coral polyp, also
referred to as the coelenteron in anthozoans, the saclike cavity within a polyp
connected to the mouth by the actinopharynx. (Bayer et al. 1983; Fautin and Mariscal
1991)
Germ Cell – oocyte or spermatocyte; cell originating in the gastrodermis of a mesentery
that migrates into the mesoglea and develops
into either an oocyte or spermatocyte. (Fautin and Mariscal 1991)
Giemsa – a stain that contains both basic and acidic dyes and will
therefore differentiate acidic and basic granules in granulocytes. It is also often used to stain
tissue sections suspected to contain protozoan
parasites. (Pharma 2006)
GMS – Grocott-Gomori’s Methenamine Silver Stain, a modification
of Gomori’s methenamine-silver staining procedure for fungi in which sections are pretreated with chromic acid before addition
of the methenamine-silver solution and then counterstained with light green to demonstrate
black-brown fungi against a pale green background. (Pharma 2006; Stedman 1995)
Gonad – gametogenic region of a mesentery in a polyp. (Fautin and
Mariscal 1991)
Gorgonin – a fibrous, collagenous protein that provides skeletal
support for sea fans and other members of the octocoral order Gorgonacea. (Coris
2006; Hyman 1940)
Granular Gland Cell (= Zymogen
Cell) – secretory epithelial cell containing acidophilic granules (e.g.,
lysosomes) that are released into the gastrovascular cavity
for extracellular digestion of prey. (Fautin and Mariscal 1991; Hyman 1940)
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H
Holdfast – the portion of an octocoral colony attaching it to or
in the substrate. (Bayer et al. 1983)
Hyalin – a translucent, homogenous, structureless, eosinophilic,
albuminoid substance occurring in tissue
degeneration. (Pharma 2006; Stedman 1995)
Hyalination – process of deposition of a cellular amorphous homogeneous
substance which stains bright red with hematoxylin and eosin. (Stedman 1995)
Hyaline – having the properties of hyalin. (Stedman 1995)
Hydropic – excess of water or watery fluid. (Stedman 1995)
Hyperplasia – an increase in the number of normal cells in normal
arrangement in a tissue or organ, increasing its size. (Dorland 2006; Stedman 1995)
Hyphae – the fine, branching tubes which make up the body (or mycelium)
of a multicellular fungus. (Pharma 2006)
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I
Imperforate coral – corals which have solid skeletons with no connections
between the polyps. (Coris 2006)
Infection – invasion and multiplication of parasitic organisms
within the body. (Stedman 1995)
Inflammation – a fundamental pathological process aimed at destroying,
diluting, and walling off the injurious agent. The process generally consists of
a dynamic complex of cytological and chemical reactions that occur in affected tissues
in response to an injury or abnormal stimulation caused by a physical, chemical,
or biologic agent, including the local reactions and resulting morphologic changes,
the destruction or removal of injurious material, and the responses that lead to
repair or healing. (Dorland 2006; Sparks 1985; Stedman 1995)
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K
Karyolysis – swelling of the nucleus of a cell and gradual loss
of its chromatin, indicated by paling of the basophilic reaction in hematoxylin
and eosin staining. (Dorland 2006; Stedman 1995)
Karyorrhexis – rupture of the nucleus of a cell and the chromatin
disintegrates into small pieces, which are extruded from the cell. (Dorland 2006)
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L
Lesion – a wound or injury, or any pathologic change in the tissues.
(Stedman 1995)
-
Lesion Distribution – distinguished on the basis of number of that
particular type of lesion (focal: single, localized area; multifocal: relating to,
arising from, or occurring in more than one place; diffuse: spread about, not restricted;
systemic: spread throughout the entire organism).
-
Lesion Severity – semiquantitative, subjective ranking of the degree
of damage or extent of pathological change seen in tissues or an organism (ranging
from minimal: smallest amount or lowest limit; mild; moderate; marked; to severe:
intensely or extremely bad, very poor condition, or greatest in degree or extent).
Loculus (plural Loculi) – calcified area or fiber-filled space
within an axis (the axial skeleton of a gorgonian)
or a space within the
gastrovascular cavity between septa
(interseptal loculus). (Bayer et al. 1983; Fautin 2005)
Lysis – dissolution or destruction of cells or structures. Lyse
means to break up, disintegrate, or to effect lysis. (Stedman 1995)
Lysosome – a cytoplasmic membrane-bound vesicle containing a variety
of glycoprotein hydrolytic enzymes (lysozymes) active at an acid pH, for digesting
exogenous material such as bacteria or worn-out organelles of the cell. (Stedman
1995)
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M
Margin – a boundary, edge, or border, as of a surface or structure.
In anthozoans, also where the polyp column meets the
oral disk. (Fautin 2005; Stedman 1995)
Melanin – high molecular weight polymer of indole quinone produced
by animals, this pigment can be black, brown, yellow, red, or violet. It is produced
by gorgonian cells (corticocytes)
to encapsulate infectious agents. (Petes et al. 2003; Pharma 2006)
Melanized – characterized by deposition of melanin. (Stedman 1995)
Mesenterial Filament – a convoluted, elongated or ribbonlike extension
of the free inner edge of the mesentery, composed of cells which aid in capture
and digestion of food. These filaments, which appear as white loops with translucent
mesentery, may also help to protect the coral from substrate competitors and invaders
by protrusion through the mouth or through temporary openings in the tissue. The
free edge is the cnidoglandular
band, which may or may not be flanked by lateral ciliated tracts or lobes
depending on the species and location along the edge. In octocorals, the filaments
of the two mesenteries opposite the siphonoglyph
are very long and heavily flagellated,
whereas the remaining six are shorter and glandular. (Bayer et al. 1983; Goldberg
2002b; Peters 1984)
-
Digestive Filament – specialized ciliated, thin, grossly translucent,
unequally bilobed, stalk-like contractile structure with spatulate distal end found
in the scleractinian coral Mycetophyllia reesi. One lobe contains cnidae, mucocytes,
collar cells, and granular cells and it protrudes through the polyp
mouth during feeding (this species lacks tentacles). It is histologically distinct
from mesenterial filaments
and is housed in mesenterial ducts, radially arranged specially modified tubular
mesenteries connecting to the actinopharynx.
(Goldberg 2002b)
Mesentery – internal longitudinal partition of tissue providing
structural support and increasing surface area, which is important in nutrition
and fertility of anthozoans. A mesentery develops by infolding of the mesoglea and
its lining gastrodermis from the body wall of the polyp. Multiple mesenteries are
arranged radially within the gastrovascular cavity of the polyp (between the septa
in scleractinian corals) and are attached to the oral disk. (Fautin 2005)
-
Directive Mesentery – one of a pair of mesenteries attached to
the actinopharynx in which the
mesogleal pleats of the longitudinal
retractor muscles face away from each other, toward the
exocoel.
-
Nondirective Mesentery – one of a pair of mesenteries attached
to the actinopharynx in which the mesogleal pleats of the longitudinal retractor
muscles face each other, toward the endocoel.
-
Complete Mesentery – extends from the body wall to attach to the
actinopharynx.
-
Incomplete Mesentery – the free inner edge does not reach the actinopharynx.
Mesoglea – the connective tissue of coral and all cnidarians consisting
of collagenous fibers embedded in a gelatinous material or ground substance of highly
hydrated protein and neutral polysaccharide polymers and containing amoebocytes and other cells. The proportion of matrix
to fiber and cells in this layer varies with the species and its condition. (Fautin
and Mariscal 1991; Peters 1984)
Mesogleal pleat – sheets of myonemes
known as longitudinal retractor muscles are anchored into mesoglea and pleated accordion-fashion
so that the mesoglea is sandwiched between two monolayers of epithelia within the
middle portion of a mesentery. (Fautin
and Mariscal 1991; Peters 1984)
Mucocyte – modified columnar epithelial cell with basal nucleus
containing basophilic granules or spumous inclusions, also referred to as a mucous secretory cell or mucosecretory cell. The cell synthesizes
and secretes mucus through an apical pore to
aid in feeding, protection, and sediment removal. (Peters 1984)
Mucosecretory cell - see Mucocyte
Mucous secretory cell - see Mucocyte
Mucus – protective secretion of
mucocytes consisting of a polysaccharide-protein-lipid complex; it traps
particles non-selectively, removes sediment, lubricates the passage of food within
the actinopharynx (ciliary-mucus
feeding) and helps digest it, provides protection against desiccation, and presents
a barrier against environmental stresses, including salinity and temperature changes
and exposure to UV radiation. Mucus may also be involved in self-recognition and
the immune response of cnidarians. Some of the properties of mucus can be distinguished
in histology by using a staining procedure involving alcian blue, periodic acid,
and Schiff’s reagent (AB/PAS). (Brown and Bythell 2005; Carson 1997; Fautin and
Mariscal 1991; Goldberg 2002a)
Mycosis – any disease caused by a fungus. (Pharma 2006)
Myoneme – contractile portion of epitheliomuscular cell or muscle fibril (myofibril)
contained within the plasma membrane that anchors it to the
mesoglea. It is attached by a long peduncle or process to the nuclear-containing
portion of the cell. Myonemes may be diffuse or clustered into longitudinal and
circular contracting sheets of muscle. (Fautin and Mariscal 1991)
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N
Necrosis – cell death characterized by irreversible damage, the
earliest of which is mitochondrial. Changes visible with light microscopy are nuclear
(pyknosis,
karyolysis, or karyorrhexis)
and generally accompanied by cytoplasmic hyper-eosinophilia, shrinkage, or fragmentation.
After such changes, the outlines of individual cells are indistinct and affected
cells may become merged, sometimes forming a focus of coarsely granular, amorphous,
or hyaline material. (Stedman 1995)
Necrotic – pertaining to or affected by necrosis. (Stedman 1995)
Nematocyst – a type of cnida,
secreted by the Golgi apparatus, produced exclusively by a
cnidocyte or nematocyte of
the Cnidaria. It consists of a double-walled capsule and an elongated hollow, sometimes
externally spiny tubule that evaginates on mechanical or chemical stimulation to
entangle or deliver toxin to prey or repel attackers. About 30 types of nematocysts
have been defined, based on morphology of the capsule and tubule. (Fautin and Mariscal
1991; Goldberg 2002b; Hessinger and Lenhoff 1989; Peters 1984)
Nematocyte – cell that produces a nematocyst. (Mariscal 1984)
Nematode – member of the Nematoda, a class of unsegmented helminthes
with fundamental bilateral symmetry and secondary triradiate symmetry of the oral
and esophageal structures. Many species are parasites. (Pharma 2006)
Neoplasia – the pathological process that results in the formation
and growth of a neoplasm. (Stedman 1995)
Neoplasm – an abnormal tissue that grows by cellular proliferation
more rapidly than normal and continues to grow after the stimuli that initiated
the new growth cease. A neoplasm is often characterized by partial or complete lack
of structural organization and functional coordination with the normal tissue, usually
forming a distinct mass. (Stedman 1995)
Neuron – multifunctional (combined characteristics of sensory,
motor, inter- and neurosecretory neurons), morphological and functional unit of
the nerve net consisting of the nerve cell body and processes, axon and dendrite(s)
(sometimes these processes are referred to as neurites), communicating through electrical
conduction or secretion of neuropeptides. (Fautin and Mariscal 1991; Grimmelikhuijzen
and Westfall 1995)
Nodule – a small node, a circumscribed mass of tissue, or knob-like
or knotty swelling of tissue. (Stedman 1995)
Nonseptate – not divided internally by partitions. (Stedman 1995)
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O
Oocyte – female sex cell or gamete, immature ovum. (Stedman 1995)
Oral – describing the region of a coral polyp near or toward the
mouth; the terms Apical and Distal can also be used to describe this region. (Fautin
2005)
Oral Disk – the part of the polyp through the center of which the
mouth opens, including peristomal tissue
and tentacles. (Peters 1984)
Ovum – the mature female germ cell (egg; female gamete). (Coris
2006)
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P
Parasite – an organism that lives on (ectoparasite) or in (endoparasite)
another organism and derives its nourishment from that host organism. (Stedman 1995)
Pathogen – any virus, microorganism, or other substance
causing disease. (Stedman 1995)
Pathognomonic – typical characteristic signs, findings, or pattern
of abnormalities specific for a given disease and not found in any other condition.
Few disease signs and findings are characteristic for a single disease (see also
Differential Diagnosis).
(Stedman 1995)
Perforate coral – coral that has a porous skeleton with gastrovascular
canals that connect the gastrovascular cavities of the polyps along the surface
and through the skeleton. (Coris 2006)
Peristome – the portion of the
oral disk surrounding the mouth and inside the ring of tentacles; may be
elevated. (Peters 1984)
Pigment cell – basally located epithelial cell that produces pigmented
granules (e.g., green fluorescent protein-like pigments, animal coloration pigment).
The genus Porites contains specialized pigment granule-producing amoeboid cells called
chromophore cells. Note that phagocytes
can contain lipofucsin pigment granules obtained from necrotic cells. (Duerden 1902;
Peters 1984)
Phagocyte – a cell capable of ingesting bacteria, foreign particles,
and other cells, present on the lobes of the mesenterial filaments
and elsewhere in corals. (Hyman 1940; Peters 1984; Stedman 1995)
Pharynx – see Actinopharynx
Pinnule – one of the lateral processes along the tentacle of an octocoral. (Bayer et al. 1983)
Planula (plural Planulae) – the ciliated planktonic larval stage
of the coral, devel¬oping from the zygote, occasionally noted in histological sections.
The planula undergoes metamorphosis upon settlement on a suitable substrate. Some
species of corals produce free-swimming planulae and other species brood planulae
within the gastric cavity for variable periods of time. (Peters 1984)
Pleomorphic – polymorphic, occurring in more than one morphologic
form. (Stedman 1995)
Polyp – the basic structural unit of an anthozoan, consisting
of a sac-like cylindrical body, a basal (aboral) disk that may be modified to produce
a calcium carbonate or gorgonin exoskeleton or attach the polyp to the substrate,
and an oral disk bearing mouth and tentacles. (Peters 1984)
Proximal – that part of a structure nearest to the
point of origin on an organism, as in a part of a limb or organ, e.g., proximal
portion of tentacle. For a polyp the proximal part is its base that is attached
to a surface or in mesoglea or skeleton. (Fautin 2005; Stedman 1995)
Psuedo-gynodioecy – the process whereby males of Galaxea fascicularis
release packages (or ‘bundles’) consisting of sperm and infertile ‘pseudo-eggs’
(containing a high-lipid content) that are thought to confer buoyancy to the male
bundle. (Hayakawa et al. 2007)
Ptychocyst – a type of cnida
used in tube construction by burying anemones (Ceriantharia). These anemones build
a tube into which they can contract for protection almost entirely from the everted
flattened, sticky tubules of the ptychocysts that trap sand grains to form the tube.
(Hyman 1940)
Pyknosis – a condensation or reduction in size of the cell or its
nucleus. Nuclear pyknosis is contraction of the nucleus to a deep staining irregular
or round mass, a stage of necrosis or sign
of cell death. (Pharma 2006; Stedman 1995)
Pyknotic – characterized by pyknosis. (Stedman 1995)
Pyrenoid – a small proteinaceous body found within the cytoplasm
of zooxanthellae (and other phytoflagellates)
and closely associated with the chloroplasts. It contains the enzyme ribulose-1,5-bisphosphate
carboxylase/oxygenase (RubisCO), which adds carbon dioxide to the sugar ribulose-1,5-bisphosphate
as it synthesizes and deposits polysaccharides. The pyrenoid is visible in fixed,
stained sections of zooxanthellae as a small round refringent body surrounded by
a pale staining starch sheath. (Dorland 2006; Leggat et al. 1999)
Pyriform – pear-shaped. (Pharma 2006)
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R
Regeneration – reproduction or reconstitution of a lost or injured
part or an entire organism. (Stedman 1995)
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S
Sclerite – minute magnesium-calcite element in octocoral mesoglea
or axis. (Bayer et al. 1983; Goldberg 1976)
Scleroblast – cell within the
mesoglea of octocorals that produces a sclerite. The sclerite may be formed
intracellularly in some octocorals or by a combination of intra- and extracellular
calcification. (Bayer et al. 1983)
Section – a thin slice of tissue, cells, macroorganisms, or any
material for examination under the microscope. (Stedman 1995)
-
Cross – sliced at right angles (or transverse) to the longitudinal
axis of the organism. A cross-section of a polyp is one sliced at right angles to
the longitudinal axis running in the oral to aboral direction. A cross-section of
a coral colony branch is one sliced at right angles to the longitudinal axis extending
from the axial polyp to the base of the branch.
-
Sagittal – sliced along or parallel to the longitudinal axis of
the polyp or branch (see Cross for explanation of axes).
-
Oblique – a diagonal cross section that is neither parallel to
the longitudinal axis nor at right angles to this axis (see Cross for explanation
of axes).
Septum (plural Septa) – one of the vertical calcareous plates or
partitions radiating from the corallite
wall toward the central axis within the calice
that provide support to the mesenteries.
(Peters 1984)
-
Primary – full plates/partitions that separate two sets of mesenterial
pairs.
-
Secondary – partial plates/partitions that separate mesenteries
within a mesenterial pair.
Signalment – identification of the organism whose health is being
examined, by describing distinguishing peculiar, appropriate, or characteristic
physical marks or signs (e.g., species name, age or stage in development, size,
coloration, gross lesions) and collection site and date collected. The basic signalment
is aided by including collection site information, the specific samples collected
from the specimen for investigation, and other observations on the history of the
specimen’s condition, to the extent known. (CDHC Workshop: Coral Histopathology
II, this document page 20)
Siphonoglyph – the strongly ciliated groove extending down the
side of the actinopharynx to
direct water into the
gastrovascular cavity. Scleractinian polyps lack siphonoglyphs; a polyp
of an octocoral, cerianthid, and zoanthid has one siphonoglyph; an antipatharian
polyp has two siphonoglyphs; although an actinarian and corallimorpharian polyp
usually has two siphonoglyphs, it may have none, one, three, or more of them. (Bayer
et al. 1983; Fautin 2005; Hyman 1940)
Skeleton – the structurally supporting matrix of aragonite crystals formed by a scleractinian on the outside
of the polyp, technically an exoskeleton, or the structural support for an octocoral.
(Bayer et al. 1983; Stachowitsch 1992)
Solenium (plural Solenia) – in octocorals, a small canal lined
with gastrodermis, penetrating
the coenenchyme, forming a network,
and fusing with the larger
gastrovascular canals to interconnect the
gastrovascular cavities of the polyps. (Bayer et al. 1983)
Spermary – gonad producing male gametes within the mesoglea of a mesentery.
It may appear as an unattached cyst-like structure within the gastrovascular cavity of a sectioned octocoral polyp, but the mesentery
producing it is attached to the underside of the
oral disk. (Bayer et al. 1983; Fautin and Mariscal 1991)
Spermatocyte, Spermatozoan – male gamete or sex cell that contains
the genetic information to be transmitted by the male. (Stedman 1995)
Spirocyst – single-walled capsule which contains a tightly coiled
tubule bearing microtubules that form a web of fine, adhesive microfibrillae when
discharged for prey capture or attachment, produced by a spirocyte. (Goldberg and
Taylor 1996; Mariscal 1984; Peters 1984)
Spirocyte – a cell lacking a sensory cilium that produces the spirocyst
and occurs only in anthozoans. (Fautin and Mariscal 1991)
Stem Cell – any precursor cell, a cell whose daughter cells may
differentiate into other cell types. The term “interstitial cell” or “I-cell” has
been used in the literature to refer to undifferentiated cnidarian (particularly
Hydrozoa) cells lying between epithelial cells or migrating through the mesoglea
that differentiate into the germ cells, nematocytes, and other cell types as needed.
The term is rarely used in discussions of Anthozoa. More recent resources did not
include this term, and “interstitial cell” has other specific meanings in vertebrate
histology. “Stem cell” has universal meaning in all organisms. (Fautin and Mariscal
1991; Hyman 1940; Stedman 1995; Thomas and Edwards 1991)
Stomodeum – mouth and
actinopharynx as it begins developing in the coral embryo and planula, is also often applied to the actinopharynx
of the adult. (Hyman 1940; Stedman 1995)
Supporting cell – columnar cell of the epidermis or gastrodermis
with central nucleus, may have apical specializations of microvilli, cilia, or flagella.
(Goldberg 2002a)
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T
Tentacle – hollow, contractile extension of the polyp’s
oral disk distal to the mesenteries, typically cylindrical, commonly tapering
to a point but in some species terminating in a spherical
acrosphere, and rarely branched. In octocorals, each tentacle has two diametrically
arrayed rows of short pinnules. The tentacle’s
internal cavity is continuous with the
gastrovascular space, continuous with that of the main body. In most species,
it is studded with nematocysts and/or
spirocysts, either scattered or arrayed
in batteries. Tentacles are typically used in food capture, defense, and sediment
removal; in some species, some tentacles are specialized to take up dissolved organic
matter from seawater. (Acropora Biological Review Team 2005; Peters 1984; Stachowitsch
1992)
Theca – wall of the skeletal cup (corallite)
surrounding the scleractinian polyp. (Stachowitsch 1992)
Tinctorial – relating to coloring or staining. (Pharma 2006)
Tissue – a collection of similar cells and the intercellular substances
surrounding them united in the performance of a particular function. Cnidaria possess
all four of the basic tissues: (1) epithelium, (2) connective, (3) muscle, and (4)
nerve. (Dorland 2006; Hyman 1940; Stedman 1995)
Transmural – see Full
Thickness
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V
Vacuole – a tiny fluid-filled cavity or a membrane-bound vesicle
formed in the protoplasm of a cell. (Dorland 2006; Stedman 1995)
Vacuolated – having vacuoles. (Stedman 1995)
Vacuolization (or Vacuolation) – formation or multiplication of
vacuoles. (Stedman 1995)
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Z
Zooxanthellae – dinoflagellates (unicellular photosynthetic organisms)
that live within the gastrodermal cells
of some scleractinians, octocorals, sea anemones and other animals (not cnidarians),
which give corals a characteristic brown coloration. Zooxanthellae provide energy
in the form of photosynthate, use animal wastes (nitrogenous ones and carbon dioxide)
and, in calcifying organisms, enhance calcification. (Peters 1984)
Zymogen – Proenzyme, precursor of an enzyme requiring a change
in the molecule to make it active. (Stedman 1995)