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Tuatara: Volume 3, Issue 1, May 1950

A Guide to the Holothurians of New Zealand

page 33

A Guide to the Holothurians of New Zealand

Holothurians or sea cucumbers form a class whose members are strikingly different from those of the other classes of Echinoderms. They have been distinct for a great length of time, as clearly recognisable holothurians (Eothuria) are known from the Upper Ordovician of Girvan, Scotland. These very ancient specimens show more features in common with the Echinoidea than are shown by any recent holothurians and in particular have a test of loosely fitting plates, even in the adult. In recent forms there is a reduction of the calcareous test to the form of small bodies of varied shape embedded in the body wall and not imposing the rigidity of structure so characteristic of the other Echinoderms. As a consequence holothurians are soft bodied, many being worm-like and unattractive in appearance and the group is less frequently noted or gathered by collectors than are the other Echinoderms. Only one species, the rather conspicuous, mottled brown Stichopus mollis, found below the low tide level in Cook Strait and Stewart Island is commonly recognised in New Zealand as a sea cucumber and it is just as frequently referred to as a “sea-slug.”

Representatives of the class are, however, known from a variety of habitats on the sea floor, ranging from the intertidal zone to the greatest depths from which dredgings have been obtained. In and a little below the intertidal zone in tropical waters, especially in coral reefs, holothurians are often large, or vividly coloured and comprise a conspicuous part of the fauna. Some of the larger species are important as beche-de-mer or trepang, whose sun dried bodies form an important item of food for a number of Oriental peoples. Most of the abyssal holothurians belong to the order Elasipoda which is not known from shallower water and so cannot strictly be included in the fauna of New Zealand. One small group, the Pelagothuriidae, are the only holothurians in which the adult is adapted for swimming, but so far no Pelagothuria has been taken in New Zealand waters.

Most of the New Zealand species are rather small and inconspicuous or live buried in sand and mud, and can only be found by careful searching, while many are as yet only known from deeper water. Some of the latter have been thrown up on beaches, occasionally in enormous numbers after heavy storms and have become known in this way, while others have only been collected by dredging in deeper water. From all these habitats the total number of holothurians described for New Zealand (including the Auckland and Campbell islands) is twenty-nine, and a distinctive variety of one of these species has also been described. All these species are included in the present key. Other species may possibly be found by careful searching in the intertidal zone, and it is page 34 highly probable that systematic dredging round the New Zealand coast would reveal quite a number of holothurians not yet recorded.

Our present knowledge of the New Zealand species began with the description of eight species by Hutton in 1872 and three more in 1878, but he did not describe calcareous deposits in either of these papers. The main foundation for the knowledge of New Zealand holothurians was laid with more detailed accounts by Dendy (1896) and Dendy and Hindle (1907). A number of smaller papers by other authors have appeared and are cited by Mortensen (1925) who made a careful revision of nearly all the previously known species and added ten new ones from the material collected during his stay in New Zealand in 1915. This brought the New Zealand total to its present number.

The identification of holothurians by external features is made difficult by their tendency to contract strongly, and to withdraw tentacles and tube feet on preservation. In this state it is very difficult to gauge accurately the size of the living animal and many species then appear very similar externally, although it is usually possible to determine the main group to which they belong. The difficulty can be partially overcome by narcotising the animal in sea water to which Epsom salts is added. In this they usually extend and when completely narcotised they should be preserved in alcohol. Lengths given in this key are for specimens extended in this way. For the more precise identification of holothurians it is usually necessary to examine the shape and relative numbers of the small calcareous particles in the body wall. This can be done by treating a piece of the body wall with a solution of bleaching powder (sodium hypochlorite) and then examining it under a microscope. By this means it is also possible to see the arrangement of the calcareous particles. If the body wall is thick, the particles can be separated out by gently boiling a small piece in a 5 per cent, solution of caustic potash, until the softer portions are macerated away, leaving only the calcareous particles. These may vary in shape even within a single individual, and changes during the life of the animal are known in some species. In spite of this there is sufficient distinctiveness between the species in the shapes, sizes and arrangements of these particles to make them the most important of the diagnostic characters for identifying holothurians. Identifications arrived at by other means should, if possible, be checked against a detailed account of the spiculation of that species. Excellent descriptions of a number of species and references to papers decribing the remainder are given by Mortensen (1925) Vid. Medd. Dansk. naturh. For., 79, p322 et.seq. Name changes introduced by H. L. Clark since Mortensen's account are Mensamaria bicolumnata (formerly Pseudocucumis bicolumnatus), M. thomsoni (formerly P. thomsoni) and Lipotrapeza dearmatus (formerly Phyllophorus dearmatus).

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The locality records given in this key are for points from which the species has definitely been collected and are not meant to imply that the species is confined to those localities. Further collecting will doubtless show that a number of species are considerably more widespread than is known at present.

1. Tube feet present on ventral surface or over the whole body. 2
Tube feet absent 19
2. Tentacle tips shield or disc shaped. (Fig. l.T.) Relatively large, i.e., adult animal more than five inches long. (Retractor muscles absent.) Order Aspidochirota 3
Tentacle tips profusely brancheed. (Fig. 6.) All except one N.Z. species less than four inches long. (Retractor muscles present.) Order Dendrochirota 4
3. Order Aspidochirota
Tentacles 20. Tube feet on underside only. On the dorsal side are pointed papillae which tend to become lowered on preservation. Colour varies from light mottled brown to black. Cook Strait to Stewart Island. From low water level to 100 fathoms. Common. (Fig. 1.) Stichopus moilis
Tentacles 16. Tube feet scattered all over the body. North Auckland. 55 fathoms. Rare. Holothuria neozelanica.
4. Order Dendrochirota
Body broad, flattened; ventral surface with a flat, well defined creeping sole. (e.g. Fig. 3). Family Psolidae 5
Body more or less cylindrical, without a clearly defined ventral sole. (e.g. Fig. 4.) Family Cucumariidae 7
5. Family Psolidae
Tube feet in two rows round edge of ventral sole with two rows along middle of sole. Calcareous deposits not in the form of large overlapping scales 6
Tube feet in two rows round the edge of ventral sole but none present along middle of sole. Dorsal surface with large imbricating scales. Length a third to half an inch. North Auckland 55 fathoms. Rare. (Fig. 2.) Psolus neozelanicus
6. Colour whitish or with purplish tinge. No tube feet on dorsal surface. Length up to one inch. Stewart Island and Macquarie Island Pseudopsolus macquariensis
Colour black except for ventral sole which is white. Small whitish tube feet all over dorsal surface. Length up to one inch. Banks Peninsula and Stewart Island. Intertidal in rock crevices. (Fig. 3.) Psolidiella nigra page 36
7. Family Cucumariidae
Tentacles 10 in a single ring 8
Tentacles 20-25. Some species with five large pairs in an outer circle and five much smaller pairs in an inner circle. Tentacles may be fewer in young animals. 16
8. Size less than three inches, and not constricted off sharply into three distinct regions. 9
Large size (up to eight inches long), body strongly curved, and marked off into three distinct regions. Oamaru and Otago Harbour. Cucumaria huttoni
9. Bluntly rounded in front and cylindrical anteriorly, tapering rather suddenly behind to a more or less slender tail which occupies about a quarter to a third of the total length. 10
Nearly cylindrical (sometimes slightly flattened) or sausage shaped, but not tapering posteriorly to form a “tail.” 11
10. Colour pink, body length up to two and a half or three inches, tail strongly turned dorsally, sometimes almost directed forwards. Tube feet restricted to the middle third of the ventral surface. Cook Strait to Banks Peninsula, below tide level. (Fig. 4.) Cucumaria ocnoides.
Colour white, body length approx. one inch, tail not strongly directed dorsally. Tube feet are present along the entire length of the ambulacra on both dorsal and ventral surfaces, but more numerous on the ventral surface especially in the middle. North Auckland to Stewart Island, in mud below tide level Cucumaria alba
11. Integument firm, at least on the dorsal surface, and sometimes gritty and rough due to the presence of very numerous calcareous spicules. No distinct anal teeth. 12
Skin on body wall very delicate and thin as calcareous spicules (types shown in fig. 9.) are too few to give strength to the skin. Distinct anal teeth. Colour uniformly white or white with blackish colour on dorsal side. Length less than half an inch. North Auckland, rocky shore. Rare. Cucumaria bollonsi
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Explanation of Plates. Plate 1. These figures are not drawn to the same scale; sizes are given in the key. Fig. 1. Anterior end of Stichopus mollis showing ventral side bearing tube feet, and the tentacles with disc shaped tips (T) surrounding the slit like mouth. Fig. 2. Psolus neozelanicus, dorsal side showing imbricating scales. Fig. 3. Psclidiella nigra, latero-ventral view showing distinct light coloured sole bearing tube feet round the edge and a double row along the centre. Fig. 4. Cucumaria ocnoides, side view showing tube feet restricted to three rows (two showing) in the middle third of the body. Fig. 5. Paracaudina coriacea. Fig. 6. Profuse branching found in the tentacles of Order Dendrochirota. In preserved material the branching may appear to be much more crowded than illustrated. Fig. 7. Finger like processes of tentacle typical of many of the Order Apoda. Fig. 8. Trochodota dendyi.

Explanation of Plates.
Plate
1.
These figures are not drawn to the same scale; sizes are given in the key. Fig. 1. Anterior end of Stichopus mollis showing ventral side bearing tube feet, and the tentacles with disc shaped tips (T) surrounding the slit like mouth. Fig. 2. Psolus neozelanicus, dorsal side showing imbricating scales. Fig. 3. Psclidiella nigra, latero-ventral view showing distinct light coloured sole bearing tube feet round the edge and a double row along the centre. Fig. 4. Cucumaria ocnoides, side view showing tube feet restricted to three rows (two showing) in the middle third of the body. Fig. 5. Paracaudina coriacea. Fig. 6. Profuse branching found in the tentacles of Order Dendrochirota. In preserved material the branching may appear to be much more crowded than illustrated. Fig. 7. Finger like processes of tentacle typical of many of the Order Apoda. Fig. 8. Trochodota dendyi.

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12. Chief spicules in the form of knobbed buttons (see Figs. 10 and 11) 13
Chief spicules of other forms 14
13. Buttons with eight to ten knobs around the edge, and all the holes of approximately equal size. (Fig. 10.) Distinct tubercles on the dorsal surface. Length one and a half to two and a half inches. North Auckland to Auckland Islands. Intertidal Cucumaria brevidentis
Buttons with twelve to fourteen knobs around the edge and the two lateral holes much the largest. (Fig. 11.) Tubercles on dorsal surface sparse. Length half an inch or less. Colour white. Auckland to Stewart Island. In rock crevices. Intertidal. Cucumaria calcarea
14. Chief spicules in the form of plates or scales. Cups absent or represented only by numerous small X-shaped bodies. 15
Plates present as large overlapping scales which bear smooth rounded somewhat elevated knobs surrounded by smaller holes connected by narrow tubes or canals. (Fig. 12a.) Cups with rounded thorns very numerous in epidermis. (Fig. 12b.) Half an inch long. North Auckland 55 fathoms. Rare. Cucumaria farquhari
15. Large plates in deeper layers of skin, being very large and coarse on the dorsal part of the body. (Fig. 13a.) Numerous very fine X-shaped bodies (Fig. 13b.) each 0.03 mm. across in epidermis. Buttons sometimes present. Skin delicate ventral side, hard and roughened dorsal side. One half to three quarters of an inch. Stewart Island and Auckland Island. 5-45 fathoms. Cucumaria amokurae Plates with serrate ends overlapping, and no other types of spicules in body wall. Up to one and a half inches long. Auckland and Campbell Islands. Intertidal. Cucumaria leoninoides
16. Tube feet in close series along each of the five ambulacra. 17
Tube feet or papillae more or less scattered over the whole body 18
17. Tentacles 20. Calcareous deposits very numerous in the form of tables bearing two spines. (Fig. 14.) An inch and a half long. Otago coast. Mensamaria bicolumnata
Tentacles 25, with 15 in outer circle and 10 in the inner circle, but may be fewer in young specimens. Calcareous deposits exceedingly scarce, but a few may be found in page 39 the anterior introverted part of the body. Two inches long. Stewart Island. 20 fathoms. Rare. Mensamaria thomsoni
18. Calcareous spicules abundant in body wall, as plates which may be cruciform, and bear two spines. (Fig 15.) Colour brown or reddish brown, paler at extremities. Length two inches. Banks Peninsula. Below tide levels. Phyllophorus longidentis
Calcareous spicules absent from body wall, except for some tables at anal extremity. Length two and a half inches. Cook Strait to Banks Peninsula Lipotrapeza dearmatus
19. Body stout anteriorily, tapering to a distinct tail-like region, (e.g., Fig. 15.) 15 short tentacles, unbranched or with simple finger like processes. Order Molpadonia 20
Body slender, cylindrical, often worm like and thin walled. (e.g., Fig. 8.) 10-12 tentacles, either pinnate or bearing finger-like processes, (e.g. Fig. 7.) Order Apoda 22
20. Order Molpadonia
Calcareous spicules include perforated plates bearing a more or less central spine. (Fig 17c.) Small orange brown phosphatic concretions in the skin. (Fig. 17d.) 21
Calcareous spicules almost circular smooth edged plates with small regularly arranged perforations and no spine. (Fig. 16.) No phosphatic concretions in the skin. Colour dull purple and may reach three inches in length. In mud 5-50 fathoms. North and South Islands. Common. (Fig. 5.) Paracaudina coriacea
21. Anchor plates (Fig. 17a) and anchors (Fig. 17b) scattered among the much more numerous tables. Tentacles minute, bearing three processes of which the intermediate one is the largest. Length two and a half to three inches. Colour reddish dappled. Cape Kidnappers mud. 68-78 fathoms. Molpadia marenzelleri
Anchor plates absent. Tentacle short and rounded with one pair of minute processes near the tip. Length two and a half to three inches. Colour deep maroon red with purplish tinge. Believed to be from deeper water off North Island. Molpadia dendyi
22. Order Apoda
Tentacles 12. 23
Tentacles 10. 26
23. Tentacles with 5 or more pairs of digits. Calcareous deposits include wheels (Fig. 18) but no perforated plates or anchors. 24
Tentacles with two pairs of digits, and bear sensory cups page 40 on stalk. (Fig. 20b.) No wheels but perforated plates and anchors (Fig. 20a), are numerous. Length four to five inches. North Auckland to Cook Strait. Below tide level. Protankyra uncinata
24. Calcerous particles include smooth or rough rods in addition to wheels. Colour red or black 25
Calcareous particles of body wall wheels only. Colour white transparent with radial muscles visible through the skin. Length more than six inches. Auckland Islands. 45 fathoms. Chirodota carnleyensis
25. Small smooth oval bodies (Fig. 21) along muscle radii. No curved rods. Colour deep purple to black but often with numerous lighter spots. Length up to eight inches. Stewart Island and Auckland Islands 12-45 fathoms. Chirodota nigra
Thick curved rods (Fig. 22) along radii as well as smooth oval bodies. Colour red. Length up to one foot. Chatham Islands and Otago fiords. Chirodota gigas
26. Mouth circular. Wheels and hooks present or absent. 27
Mouth a dorso-ventral slit. Wheels always present and hooks (Fig. 19) scattered and not grouped into papillae. Colour pinkish with reddish spots at ends. Length up to two inches. Auckland to Campbell Island. Intertidal. Common. Trochodota dunedinensis
27. Wheels present, and groups of three to six hooks support each of the minute papillae. Colour whitish or with faint purplish tint. Length up to six inches. Auckland to Stewart Island. Intertidal. Common. Trochodota dendyi
No wheels or hooks present. Skin with many minute papillae giving it a granulated appearance. Pale pinkish brown. Length up to four inches. Auckland to Stewart Island. Intertidal. Kolostoneura novae-zelandiae
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Plate 2. Fig. 9. Cucumaria bollonsi, buttons and cups from the skin. Fig. 10. C. brevidentis, a button. Fig 11. C. calcarea, a button. Fig. 12. C. farquhari, A. part of large scale; B. cup. Fig 13. C. amokurae, A. large scale from side of the body; B. × shaped bodies. Fig. 14. Mensamaria bicolumnata, tables bearing a double spire. Fig. 15. Phyllophorus longidentis, plates bearing a double spine. Fig. 16. Paracaudina coriacea, a rounded plate. Fig. 17. Molpadia marenzelleri. A. anchor plate; B. anchor; C. perforated plate bearing spine; D. phosphatic concretion. Fig 18. Wheel as found in many of the Order Apoda. Fig. 19. Hook or sigmoid body as found in Trochodota. Fig. 20. Protankyra uncinata, A. anchor; B. tentacle bearing two pairs of finger like processes, and sensory cups on the stalk. Fig. 11. Chirodota nigra, smooth oval bodies found along the muscle radii. Fig. 22. Chirodota gigas, thick curved rods from along the radii. (Figs. 2, 9, 12, 13, 20, after Mortensen; figs. 14, 22, after Dendy and Hindle; fig. 17 after Theel.)

Plate 2.
Fig. 9. Cucumaria bollonsi, buttons and cups from the skin. Fig. 10. C. brevidentis, a button. Fig 11. C. calcarea, a button. Fig. 12. C. farquhari, A. part of large scale; B. cup. Fig 13. C. amokurae, A. large scale from side of the body; B. × shaped bodies. Fig. 14. Mensamaria bicolumnata, tables bearing a double spire. Fig. 15. Phyllophorus longidentis, plates bearing a double spine. Fig. 16. Paracaudina coriacea, a rounded plate. Fig. 17. Molpadia marenzelleri. A. anchor plate; B. anchor; C. perforated plate bearing spine; D. phosphatic concretion. Fig 18. Wheel as found in many of the Order Apoda. Fig. 19. Hook or sigmoid body as found in Trochodota. Fig. 20. Protankyra uncinata, A. anchor; B. tentacle bearing two pairs of finger like processes, and sensory cups on the stalk. Fig. 11. Chirodota nigra, smooth oval bodies found along the muscle radii. Fig. 22. Chirodota gigas, thick curved rods from along the radii. (Figs. 2, 9, 12, 13, 20, after Mortensen; figs. 14, 22, after Dendy and Hindle; fig. 17 after Theel.)