Morphological characters and their states : Holothuroidea

1. Morphological characters and their states : Holothuroidea Ahmed S Thandar School of Biological and Conservation Sciences University of KwaZulu-Natal, Westville Campus Durban, South Africa

2. Classical/traditional taxonomy has always favoured the use of morphological characters as they are readily perceived and easiest to use. At our first workshop we attempted to standardize and define some of them and utilized their states for preliminary analyses. For the sake of posterity we must revise and refine these, at this and subsequent workshops. • Variations in morphological characters have always been accepted as indicators of genetic variations and their similarities as indicators of relationships. • Thus, over the years, as a result of the correct use of morphological characters, a more or less natural system of classification has evolved for most of the higher taxa but this is far from satisfactory.

3. When selecting morphological characters, especially for the higher taxa, we must seek non-adaptive characters as they change very slowly, unlike adaptive characters which are fast-changing and thus most likely to fluctuate under environmental pressures. The use of the latter, I believe, has be-devilled a rational classification amongst some holothuroids, notably the Dedrochirotida. • I will recall some of the morphological characters and their possible states but will not limit my consideration to the Aspidochirotida since an appreciation of these throughout the group, will be necessary for critical appraisement of original descriptions and during examination and/or re-description of types.

4. Distinction between orders based on: • Gross morphology of tentacles • Presence/absence of podia • Presence/absence of introvert and retractor muscles • Gross morphology of calcareous ring • Presence/absence of respiratory trees peltato-digitate digitate peltate dendritic pinnate

5. Distinction between families within the Aspidochirotida: • Form and arrangement of tentacles • Presence/absence of tentacle ampullae • Form of the calcareous ring • Single/paired gonadal tufts • Presence/absence of Cuvierian tubules • Presence/absence of table deposits • Presence/absence of button deposits • Presence of rosette-derived (120º) and button-derived (90º) plates

6. Characters at generic level within the Aspidochirotida • Tentacle form and number • Presence of modified podia • Form of calcareous ring • Ossicle assemblage of: • body wall (mid-dorsal & mid-ventral) • dorsal podia and/or papillae • ventral podia (tubefeet/pedicels) • tentacles • gonad • cloaca • longitudinal muscles • cloacal suspensor muscles Labidodemas rugosum Stichopus herrmanni Bohadschia marmorata Actinopyga echinites Holothuria pervicax Synallactes n. sp.

7. Characters at specific level: • Many old descriptions are very brief, hence, in the absence of type material, a lot of guesswork must have been involved in deciphering which species a particular taxonomist was describing. • Therefore, there is need for complete species descriptions. For these, we need to develop a standardized list of morphological characters and their possible states. • Such a list must not be exhaustive as many species present other characters (special/unique) which also need recording.

8. Characters at specific level • Although the most important characters for species distinction are the ossicles, my task is to review external and internal morphological characters (excluding ossicles) and their states, to allow us to standardize and define these. • Detailed descriptions are indispensable for delineating species, separating related or sister species, allowing the assemblage of these into higher taxa and aiding in the determination of relationships with the use of computer-based software.

9. External morphological characters • Body form – • cylindrical, sub-cylindrical, vermiform, robust/slender, barrel-shaped, U-shaped, cigar-shaped, pentagonal/quadrangular in cross-section, psolid-like, etc., sometimes in combination of more than one character state (wherever possible a colour or black & white photograph or drawing of the entire animal must be given)

10. External morphological characters • Size • indicative of maximum size and/or maturity (mention must be made whether one is dealing with a contracted or relaxed specimen) • measurements must be given for total length, width of mid-body • width of anterior and posterior ends, in an attenuating specimen (for U-shaped forms it would be ideal to measure lengths of both the dorsal and ventral surfaces)

11. External morphological characters • Colour • important diagnostic feature for many non-holothuroid taxa • live colouration more important • colour description must include that of tentacles (stalk and branches), podia, papillae, warts/tubercles, etc.

12. External morphological characters • Mouth • position of mouth (terminal, sub-ventral, ventral, etc) • presence/absence of acollar(naked/papillose, fused/unfused papillae) • presence/absence of valves around mouth. • Anus • position of anus (terminal, dorsal, sub-dorsal) • associated structures (specialised papillae, typical podia, anal teeth or a mixture of these)

13. External morphological characters • Tentacles • number • arrangement • size variation • type, shape • length of largest relaxed • length of shortest relaxed • colour of stalk and branches • Podia • arrangement, dorsal & ventral (scattered, in ambulacra, rows) • abundance • form and rigidity, if any • sucking disc-diameter, colour, etc. (in some species podia may be all in the form of tube feet/ pedicels, in others tube feet ventrally, papilliform dorsally, or papilliform throughout)

14. External morphological characters • Warts (tubercles) and/or papillae • size & number • arrangement • colour • Sensory cups and eyes (only in apodids) • number • form • position • arrangement

15. External morphological characters • Consistency of body wall • soft/flaccid, firm/rigid, gelatinous, etc. • Texture of body wall • smooth, rough • Thickness of body wall • dimension (must state whether relaxed/contracted specimen)

16. Internal morphological characters • Calcareous ring • very important, preserved also in fossils • adult material better as ring can change with growth • generally five radial plates alternating with five interradial plates (in apodids and malpadids, plates may exceed 10) • while type of ring is indicative of order or family, form and size of individual plates may offer good generic, subgeneric or specific characters

17. Internal morphological characters Calcareous ring – Aspidochirotida Labidodemas rugosum • radial plates usually larger than interradial plates. Must record: • shape • proportion -length vs breadth • height in relation to interradial plates • peculiar scrupturings, if any • anterior and posterior configurations, eg. notches, concavities • presence / absence of postero-median projections • variations, if any, between dorsal radial plates as opposed to ventral ones Holothuria discrepans Stichopus herrmanni Holothuria squamifera Actinopyga echinites Bohadschia marmorata Synallactes n. sp.

18. Internal morphological characters • interradial plates usually smaller than radial plates. Must record • form • size in relation to the radial plates • anterior an posterior configurations ( necessary to illustrate CR as description of one author may vary from that of another)

19. A Internal morphological characters B Calcareous ring - Dendrochirotida • simple, ribbon-like, without posterior prolongations as in some cucumariids , eg. Aslia (A) • Simple, thick, without posterior prolongations, as in most cucumariids, eg. Pentacta (B) • ring with paired, posterior prolongations as in the 10-tentacled phyllophorids. Such ring always referred to as complex/tubular or both. Basically three types: • plates compact, separate or only basally united, hardly forming a tube but with usually long, subdivided posterior processes, as in Sclerothyoninae (C) • plates compact, fused/unfused, forming only a short tube with short posterior processes that are either subdivided or entire as in Sclerodactylinae (D) • plates elongated, fused, compact or broken into a mosaic, forming a long tube with usually sub-divided posterior processes, as in the Thyoninae (E) C D E

20. Internal morphological characters • In the “supergenus” Thyone, the tubular ring is variable – generally of three types, demonstrating some geographic variation, with radial plates bifurcating either: • beyond posterior border of interradial plates or • before posterior border of interradial plates or • at posterior border of interradial plates

21. Internal morphological characters • The polytentaculate phyllophorids do not seem to be a natural group as they exhibit all forms of calcareous rings. Even in just one subfamily, the Cladolabinae, we find all forms of calcareous rings, except that which is tubular. This must be borne in mind when determining phylogynies. Actinocucumis typicus Ohshimella ehrenbergii Cladolabes aciculus Afrocucumis africana

22. Internal morphological characters • Tentacle ampullae • although their presence/absence is important at higher level, their size and shape may be important at specific level but some caution needs to be exercised • Water vascular ring • position in relation to the calcareous ring • Polian vesicles • number • position • length • shape (some caution also needs to be exercised here)

23. OVAL GLOBULAR FILAMENTOUS H. difficilis Holothuria n. sp. H. hilla H. pardalis H. scabra Neostichopus grammatus H. pervicax H. parva Mesothuria parva Internal morphological characters • Stone canal(s) • number • position • length • form • free/attached • Madreporite • internal/external • free/attached • degree of calcification • form (elongate, kidney-shaped, lobed, globular, coral-like, etc.)

24. Internal morphological characters • Respiratory trees • nearly always paired, profusely branched, one usually longer • either arise from cloaca independently or together • in some psolids and dactylochirotids may be very simple, often asymmetrical, with scant saccular/filiform end-branches • sometimes branchings very complicated with well-branched supplementary trunks giving impression of four trees, as in Massinium. Psolidothuria octodactyla Massinium arthroprocessum

25. Internal morphological characters • Gonad • form of branchings (dichotomous, irregular, etc.) • maturity • gametes, hermaphrodity • brood pouches, if any • Longitudinal muscles • usually paired in aspidochirotids, singular in dendrochirotids and some others • in molpadids either paired/singular • Retractor muscles • sites of origin and insertion • ventral ones usually arise more anteriorly • divide/undivide before insertion

26. Internal morphological characters • Cuvierian tubules • presence or absence • expellable or non-expellable • adhesivity or non-adhesivity • appearance (long,thin; short, thick; short, thin; etc.) • structure of proximal and distal ends • number of attachment sites • Ciliary funnels • shape/form • solitary, or in clusters • sessile, stalked (illustrations necessary as shape difficult to describe) Chiridota Polycheira

27. Acknowledgements • Clark, A.M. & Rowe, F.W.E. (1971) Monograph of shallow- water Indo-West Pacific echinoderms. British Museum (Natural History), London, 238 pp • Rowe, F.W.E. & Richmond, M.D. (1997) Echinodermata. In Richmond, M.D. (Ed.) A guide to the seashores of eastern Africa and the Western Indian Ocean Islands. Sida, 1997:290-320 • Thandar, A.S. (1987a) The southern African stichopodid holothurians, with notes on the changes in spicule composition with age in the endemic Neostichopus grammatus (H.L. Clark). South African Journal of Zoology, 22, 278-286. • Thandar, A.S. (1989c) The sclerodactylid holothurians of southern Africa, with the erection of one new subfamily and two new genera (Echinodermata : Holothuroidea). South African Journal of Zoology, 24, 290-304. • Thandar, A.S. (1990) The phyllophorid holothurians of southern Africa with the erection of a new genus. South African Journal of Zoology, 25, 207-223. • Thandar, A.S. (1991) The cucumariid holothurians of southern Africa with the erection of a new genus. South African Journal of Zoology, 26, 115-139.