The purposes of this section are threefold:

a. To act as a reference for the definition of any terms found in the text.

b. To serve as a general introduction to some of the terminology associated with sponges. To this end, the sections in this glossary correspond to the headings found in the species descriptions. Within each section, the terms are then arranged in an appropriate, logical sequence.

c. To indicate the terms available and the information that should be observed and noted when recording a sponge specimen.

Where adequate and precise definitions have been previously published, these are reproduced verbatim. The main sources are Borojevic, Fry et al., (1968) and Weidenmeyer, (1977). Other sources are noted in the text.

1. FORM.

1.1 Terms relating to the shape of the sponge.

The terms in this section are arranged approximately in order of increasing mass and/or complexity of body form.

Boring a. Some or all of the sponge is contained in channels within a hard substrate such as shell or limestone.
b. No basal attachment area. (e.g. the alpha stage of Cliona celata.)
Thin sheets a. Growth predominantly lateral, resulting in spreading sheets less than 3mm thick.
b. Attachment basal area continuous. (e.g. Microciona atrasanguinea).
Cushions a. Growth predominantly lateral, resulting in spreading sheets between 3 and l0mm thick.
b. Attachment basal area continuous. (e.g. Myxilla fimbriata).
Massive-lobose a. Growth vertical and lateral but unequal, greater than about 10mm; if growth is predominantly vertical results in lobed forms; if growth is predominantly lateral results in ridged forms.
b. Attachment area matches greatest body width e.g. Myxilla incrustans).
Massive-globose a. Includes forms which are globular, hemispherical or disc-shaped.
b. Growth vertical and lateral.
c. Attachment basal area as much as greatest body width (i.e. hemispherical) or slightly less than greatest body width (i.e. globular). (e.g. Polymastia boletiformis).
Massive-pear a. Growth vertical and lateral but unequal.
b. Attachment basal area as much as, or slightly less than, the greatest body width.
Massive-fig a. Growth vertical and lateral but unequal.
b. Attachment basal area less than the greatest body width (e.g. Suberites carnosus).
Massive-flanged a. Growth vertical and lateral but unequal. Vertical growth can proceed at variable rates, infilling the spaces between the erect, flattened ribs or flanges of immature sponge. Viewed from above, flanged crests can either be regular, radiating out from the centre like spokes of a wheel, or irregular, set at angles to each other.
b. Attachment basal area corresponds to greatest body width.
Cylindrical a. Includes forms which are tubular, club-shaped, spindle-shaped.
b. Growth predominantly vertical and columnar, but because it is more raised at outer edges, a hollow centre is formed but this becomes invisible when the apical opening becomes reduced to an oscule, and effect is closed. Hollow centre may later become infilled so cylinder appears to be solid and apical opening is no longer apparent.
c. Cylinder may be circular in cross-section or ellipsoidal when cylinder is laterally compressed.
d. Attachment basal area less than the greatest body width (e.g. Scypha ciliata).
Cuplike a. Includes forms resembling vases, funnels and cups.
b. Edges of walls may be discontinuous, i.e. may only be joined together at lower margins, forming a notch, but here they are treated as cups.
c. Growth predominantly vertical and spreading, but because it is more rapid at outer edges, a hollow centre is formed which remains visible - effect is open.
d. Attachment basal area less than greatest body width (e.g. Axinella infundibuliformis).
Lamellate a. Includes forms resembling fans (flabellate forms) and flaps (i.e. vertical sheets).
b. Includes erect fans lying in one plane, to fans curved round to resemble cups or even whorls, but whose free edges never join at any point to form actual cups.
c. Growth is predominantly vertical.
d. Attachment basal area less than greatest body width (e.g. Axinella flustra).
Branching-repent a. Branches may be simple or fused, cylindrical or flattened in cross section, solid or hollow.
b. Growth is predominantly horizontal.
c. Attachment basal area large in proportion to body bulk, though it may not be continuous (e.g. Haliclona simulans).
Branching-erect a. Branches may be simple or fused, cylindrical or flattened in cross-section, solid or hollow.
b. If growth is predominantly vertical, results in erect and free forms (i.e. tree-like), with regular or irregular branching. If growth is predominantly horizontal, results in semi-erect, free forms whose branches lie parallel to the substratum. The stalk is usually visible adding to the erect impression, cf. repent.
c. Attachment basal area is small in proportion to body bulk (e.g. Axinella dissimilis).

1.2 Miscellaneous terms

These are some terms that might be encountered in the description of form (as well as in other contexts).

Mesial/medialOf or situated in the middle.
Dichotomous Branching by repeated division into two roughly equal parts.
Polytomous Branching by division into more than two parts.
Anastomose To join or merge, e.g. as in branches which fuse together.
Stipitate Stalked.
Rooting tufts Processes anchoring the sponge into a soft substrate. Common in deep sea sponges.

1.3. Sponge dimensions

Measure height, length and width (in cms). It is preferable to indicate these dimensions on a sketch.


Despite the familiarity of the concept of colours the recording of colour without a basis for comparative reference can be highly subjective. It is therefore strongly recommended that colours are recorded with the assistance of the Methuen Handbook of Colour (Kornerup and Wanscher, 1978). Many colour descriptions in the species sheets have not used this (or any other) basis of reference, but we hope to standardise gradually on this book. In general many sponges develop more pigment in high ambient light levels, so colour is variable both with predominant water clarity, depth, and topographic position of the colony.


Most marine sponges produce little smell out of water or, if they do, it is a general marine odour. However, in a few cases, odours are emitted which can be distinctive, and may even be diagnostic. Unlike people in the wine trade, spongologists have not evolved a vocabulary for smell, which must for the time being be likened to other smells that are familiar.


Many sponges produce mucus as a defence against the settlement of detritus, or other marine organisms. The extent to which this slime is exuded on collection can be diagnostic. For example, Polymastia boletiformis gives off no slime, Myxilla rosacea exudes a lot, Haliclona viscosa is only obviously slimy when crushed, and Haliclona cinerea produces slime strands when pulled apart. It is therefore important to record the amount of slime, and how it is exuded.


Again, a language for consistency is still evolving. Terms used are everyday adjectives, but their meanings in the context of sponge descriptions are given below. They should be qualified with very, slightly, etc. as appropriate.

5.1 General Consistency

Soft Like wet cotton wool (e.g. Rhaphidostyla kitchingi).

Compact Firm and rubbery (e.g. Polymastia boletiformis).

Hard Treat as a quality distinct from firmness (see below). A hard sponge is one with a surface like wood. (e.g. Haliclona simulans).

5.2 Reaction to pressure

Compressible Easily compressed (e.g. Dysidea fragilis).

Firm Requires considerable pressure to deform the sponge. Like the rubber of a car tyre. (e.g. Pachymatisma johnstonia).

Incompressible Does not compress (e.g. Stelletta grubii).

Elastic How far does the sponge return to its original shape after compression? Like a bath sponge if elastic (e.g. Dysidea fragilis).

Inelastic Where any deformation is retained (e.g. Pachymatisma johnstonia), and there is no tendency to return to the original shape. Like 'styrofoam' used by flower arrangers to hold water and plant stems.

5.3 Characteristics when torn or broken

Fragile Easily falls to pieces (e.g. Microciona armata).

Brittle Easily breaks (e.g. Haliclona simulans).

Tough Resistance to tearing: this property is in most cases covered by firmness (see above). However, uneven distribution of strengthening tissues may lead to unexpected results which are worth recording (e.g. Dysidea fragilis).

5.4 Characteristics when manipulated

Fleshy Tendency to be gelatinous with reduced or non-existent skeleton (e.g. Thymosia guernei).

Crumbly/Friable Easily broken into small pieces when rubbed between the fingers (e.g. Halichondria panicea).

Slimy Mucus is apparent when sponge is rubbed between the fingers (e.g. Stelligera rigida). See section 4 above.


6.1 Profile view

Even The gross surface profile has smooth lines, without marked irregularities. (e.g. Pachymatisma johnstonia).
Uneven Opposite to above (e.g. some forms of Myxilla incrustans).
Wrinkled Parts or all of surface thrown into wrinkles.
Irregular Folds In some parts the surface fold over onto itself (e.g. some forms of Hymeniacidon perleve).

6.2 Projections

Smooth No projections, hairs or depressions (e.g. Pachymatisma johnstonia).
Tuberculate Warty appearance caused by small rounded projections (e.g. some forms of Stylostichon plumosum, Tethya aurantium).
Conulate Pyramidal cone-shaped projections, often caused by lifting of surface due to protruding end of skeletal fibres (e.g. Dysidea fragilis).
Fistulate Hollow, narrow, reed-like tubes, averaging less than 5mm long (e.g. the smaller processes usually present on Haliclona fistulosa).
Papillate Hollow, strap-like tubes averaging more than 5mm long (e.g. Polymastia spp.).
Branching processes Longer, tassel-like, processes thrown off from the surface, which may branch and/or anastomose (e.g. Amphilectus fucorum, Haliclona fistulosa).
Oscular chimneys Mammillate to cylindrical surface projections bearing oscules (e.g. Haliclona viscosa).

6.3 Hairs

Spinose Coarse, short, stiff, bristly hairs, usually widely spaced.
Hispid Long, closely-packed hairs.
Hirsute Rough, coarse, untrimmed hairs, shorter than hispid.
Villose Long, shaggy hairs, slender and soft but not matted; longer than hispid (e.g. Stelligera rigida).
Velutinous Velvety; hairs dense, firm and straight (e.g. Suberites carnosus).

6.4 Depressions

Punctate Punctured; surface dotted with pin-point impressions (e.g. inner surface of Axinella infundibuliformis).
Striated Marked with longitudinal or parallel lines (e.g. Adreus fascicularis).
Sulcate Furrowed with longitudinal or parallel channels. (e.g. Mycale lingua)
Polygonal grooves Self explanatory.

6.5 Subsurface features

Canal patterns Subsurface exhalant canals are sometimes seen through the surface (e.g. Microciona atrasanguinea).
Cavities These sometimes occur below, and show through, the ectosome (e.g. Dysidea fragilis).

6.6 Feel

Granular Has a gritty feel (e.g. Pachymatisma johnstonia).
Leathery Feels like leather.
Slippery Negligible friction, may be caused by mucus (e.g. Homaxinella subdola ).
High friction Like a pencil eraser (e.g. Haliclona simulans).
Moderate friction Anything in between the previous two (e.g. Myxilla incrustans).


Ostium Any opening through which water enters a sponge.

Oscule (=osculum) An aperture through which water leaves a sponge.

Normally, ostia are small, sometimes not visible or obvious to the naked eye, whereas oscules are prominent. It is important to note whether apertures are scattered, grouped, in a linear series, or some other arrangement; their frequency; and whether they are open or closed before and after collection.


Although certain sponges have been reported to respond to the presence of a diver underwater, contraction usually occurs only on physical disturbance and/or removal from the water. Its occurrence and degree should be noted - i.e. none, slight, marked.


Terms described in the first section are anatomical, and in the remaining sections are skeletal.

9.1 Anatomical Terms

Choanocyte A cell bearing a flagellum, which is surrounded by a collar of cytoplasmic microvilli (i.e. finger-like projections)
Choanocyte chamber Any cavity lined by choanocytes.
Flagellated chamber Synonymous with, but less precise than, the previous term. It is preferable to avoid using. it.
Ectosome Peripheral region of a sponge, devoid of choanocyte chambers.
Choanosome A region of a sponge, containing choanocyte chambers, i.e. loosely the interior of a sponge.
Pinacoderm A unistratified layer of cells, other than the choanoderm delimiting the sponge from the external milieu.
Choanoderm A single layer of choanocytes.
Mesohyl Everything constituting the sponge between the pinacoderm and the choanoderm.
Cortex A layer of the ectosome consolidated by a distinctive skeleton.
Spherulous cells Cells containing large, round vacuoles, occupying most of the cells.(e.g. Mycale similaris).

9.2 Skeletal components

Skeleton All structures of which the primary function is the consolidation and mechanical protection of the sponge.

Spicule A discrete autochthonous element of the skeleton consisting mainly of silica or calcium carbonate. (Autochthonous means they are indigenous to the sponge which has secreted the spicules.) Section 10 (following) is a glossary of terms used to describe spicules.

Collagen The major structural protein of the animal kingdom.

Fibrillar collagen Fibrils of collagen dispersed throughout the intercellular matrix.

Spongin Proteinaceous horny skeletal material, either alone [as in bath sponges], or binding siliceous spicules together [as in Haliclona or Microciona]. Another type of collagen.

Fibre A discrete column of spongin, either without spicules, (e.g. Aplysilla) or cored by indigenous spicules (e.g. Haliclona) or filled with foreign spicules and/or debris (e.g. Dysidea). In some sponges (e.g. the Haplosclerids) the distinction is made between primary fibres, which run perpendicular to the surface, and secondary fibres, which run parallel to the surface.

Tract A column or (rarely) single line of bundled, overlapping, or aligned monaxonic megascleres, with or without spongin cement.

9.3 Skeleton Arrangements

Ascending Used mainly of fibres and tracts (q.v.), where they extend to the surface and end orientated perpendicular to it (equivalent to 'vertical').

Echinating Literally covered with spines, bristles, or bristle-like outgrowths. In the context of sponge skeletal arrangements, the term is used to describe monactinal spicules standing off, or projecting from, another structure.

Palisade Spicules arranged like a fence.

Plumose fibre, column A fibre or column usually ascending, with monaxon megascleres radiating obliquely upward from the axis, points outwards; these columns commonly anastomose; they characterize axinellid structure.

Radiate structure Skeletal architecture characterized by megascleres oriented radially from the centre of the sponge, and commonly by lack of spongin.

Isotropic reticulation Reticulation which is disorientated, random, and in which there is no distinction of primary and/or secondary fibres or tracts.

Isodictyal reticulation Isotropic reticulation in which the meshes are commonly triangular in all directions, outlined by single monaxon megascleres which are joined at their tips, with spongin cementing the nodes.

Anisotropic reticulation That type of reticulation which is oriented with respect to the surface, and in which either primary, or secondary fibres (or tracts) or both can be distinguished.

Plumoreticulate Plumose columns arranged in a network.

9.4. Skeletal Arrangements Implied by Reference to Taxa

Choristid From the Order Choristida (replaced by Astrophorida in the classification scheme used in this Guide). The type of skeletal architecture distinguished by predominantly radiate, occasionally confused, arrangements of megascleres including triaenes with cladomes outward, by lack of spongin, and commonly by a cortex. See the figure of Stelletta grubii showing part of the cortex.

Halichondroid From the Order Halichondrida. The type of skeletal architecture characteristic of Halichondria and some other sponges, i.e. with megascleres arranged in vague tracts which may be reticulate; or scattered in sheets between alveoles and stouter ascending tracts. In sections the spicules often appear as a disorganised, criss-crossing mass.

Hymedesmoid From the genus Hymedesmia. In encrusting sponges, that part of the skeleton consisting of large primary acanthostyles perpendicular to the substrate, and smaller acanthostyles echinating the substrate. See the figure of Hymedesmia paupertas showing a perpendicular section through the entire sponge.

Renieroid From the Genus Reniera in the Family Haliclonidae. The type of reticulate structure as in Haliclona (Reniera), i.e. an anisotropic reticulation of diacts which is commonly unispicular, with spongin at the nodes; or with ascending tracts within an isotropic or anisotropic interstitial reticulation of single diacts.


Because the types, shapes and sizes of spicules tend to be consistent within a species, they are very important characters for sponge classification. Their great variety has attracted a complex nomenclature, unfortunately not entirely avoidable. However, this glossary is restricted only to spicules mentioned in the species descriptions. Various narrative definitions are given below, but the essence of the glossary is in the figures on the right as the authors feel that direct visual comparison is always far better than complex jargon. On the whole, it was felt unnecessary to supplement these figures with turgid and precise definitions, and this has largely been avoided. Terms appearing below either do not occur in the figures (but do in the text), or are included to clarify the figures where this was felt to be necessary.

Monact(inal) Any spicule (megasclere or microsclere) having one ray, which grew from one end only; with ends fundamentally different in form. The four spicules to the upper right (fig. 1) are monacts.

Diact(inal) Any spicule (megasclere or microsclere) having two diverging rays; being commonly but not always bilaterally symmetrical (with conforming ends). The six spicules to the upper left (fig. 1) are diacts.

Monaxon Any linear, non-radiate spicule; or a spicule type never having more than two rays along one axis. This collective term includes both actinal and diactinal spicules. Thus all the spicules on the upper row (fig. 1) are monaxons, as are the microrhabds and sigmatoscleres in fig. 2.

Triact(inal) Any radiate spicule (megasclere or microsclere) having three rays. Such spicules are most frequent in Calcarea, rare in Hexactinellida (as reduced hexacts) and in Demospongia (as reduced tetraxons).

Triradiate Synonymous with triact - used in this Guide to describe calcareous spicules.

Tetract(inal) Any radiate spicule (megasclere or microsclere) having four rays. The lower row of spicules (fig. 1) are tetracts.

Quadriradiate Synonymous with tetract - used in this Guide to describe calcareous spicules.

Acantho- Prefix meaning spined. Acanthostyles occur frequently in the sponges in this guide.

Tylote A diactinal megasclere with a tyle on each end. Also an adjective meaning provided with one or more tyles. A tyle is any rounded swelling or knob in a spicule, other than the centrum. (Note that a centrum is the globular centre of many euasters).

Centrotylote A median swelling (tyle) in a spicule. See centrotylote oxea, and centrotylote microxea on right. (e.g. Suberites ficus)

Polytylote A spicule with a series of swellings along the shaft. (e.g. styles of Polymastia conigera)

Megasclere The larger spicule types, comprising the major structural elements of a sponge skeleton. All spicules illustrated in fig. 1 are megascleres.

Calthrops Tetraxon megasclere with equal rays arranged normal to faces of a tetrahedron. The point to note is the symmetry of calthrops spicules. (e.g. Dercitus bucklandi)

Triaene Any tetraxial, tetractinal megasclere having one unequal ray (termed rhabd) which is commonly much longer than the other three (known as clads, together forming the cladome), occasionally shorter, or modified (see Stelletta grubii).

Microscleres Relatively very small spicules of various forms, characteristic of certain sponges. The following four definitions are for the categories of microscleres encountered in this Guide. The spicules illustrated in fig. 2 are all microscleres.

Microrhabds A collective term for monaxonic microscleres, excluding sigmatoscleres and spiroscleres. Among the simple forms are microxea, microstrongyle, microstyle (comma), raphide; among the ornamented (e.g. spined) forms are sanidaster and its variants, which were once regarded as asters.

Sigmatoscleres A group of monaxon microscleres including sigma and its variants. See the central group of spicules in fig. 2.

Streptoscleres A collective term comprising streptasters with the exclusion of sanidaster and its variants. See the left of the bottom row of fig. 2.

Euasters A collective term for astrose microscleres in which the actines radiate from a centre; with or without a centrum. See the right of the bottom row (fig. 2).

Spheraster An euaster with short rays and a thick centrum. The diameter of the centrum exceeds the length of the rays. The rays may be pointed (oxyspheraster), strongylote (strongylospheraster), or tylote (tylospheraster). See the oxyspheraster in fig. 2.


Chelae The drawings of chelae in this publication have been prepared from Scanning Electron Microscope images, which reveal their true shape. As silica is transparent, however, they often appear to have different shapes under the light microscope. The alae of chelae are very thin, so usually the shape that is seen depends on the angle at which they lie to the microscope. The supporting structures beneath the alae (falces) are usually more obvious because of their thickness.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2007. [In] Sponges of Britain and Ireland