Key to Class Holothuroidea

Phylum Echinodermata

Taken primarily from  Kozloff, 1987, 1996  (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a Upper surface of body with numerous large, fleshy, pointed projections; buccal tentacles moplike; length commonly greater than 25 cm 2
1b Upper surface of body without fleshy, pointed projections; buccal tentacles bushy, pinnately branched, or unbranched, but not moplike; length rarely exceeding 25 cm 3
2a Color usually reddish brown or orange-brown, sometimes mottled; length up to about 50 cm; primarily subtidal, but also low intertidal  (Parastichopus californicus in key) Apostichopus californicus
2b Color reddish orange with small white papillae and rust-colored patches; length up to about 38 cm; strictly subtidal (Parastichopus leukothele in key) Apostichopus leukothele
3a Without tube feet other than the buccal tentacles; buccal tentacles either unbranched or pinnately branched 4
3b With tube feet on at least part of the general body surface; buccal tentacles bushy 7
4a Buccal tentacles unbranched, fingerlike; body wall thick, without anchor-shaped ossicles that project externally; aboral end of the body tapering to a "tail"  5
4b Buccal tentacles pinnately branched; body wall thin, with anchor-shaped ossicles that project externally (these ossicles are microscopic, but they engage one's skin when the animal is handled); body slender, but not tapering to a "tail" 6
5a Body elongated, with a long tail; color generally pinkish, purplish, or silvery gray; intertidal or subtidal, in rather clean sand Paracaudina chilensis
5b Body stout, with a short tail; color mostly reddish brown or reddish purple; subtidal, in mud Molpadia intermedia
6a Usually with 12 (sometimes 11 or 13) buccal tentacles; body surface with raised papillae; color almost uniformly pale pink; average diameter of oocytes about 400 micrometers; primarily intertidal in muddy sand and gravel Leptosynapta clarki 
6b Usually with 10 (sometimes 9 or 11) buccal tentacles; body surface without raised papillae; color white with dark red spots (more spots on the upper surface and near the anterior end than elsewhere); shallow subtidal Leptosynapta transgressor
7a Lower surface of body a flattened "sole" with 3 double rows of tube feet; upper surface covered by large calcareous plates 8
7b Lower surface of body not flattened to form a "sole"; upper surface not covered by calcareous plates 10
8a Calcareous plates on upper surface with small nodules readily visible at 10x magnification (caution: the nodules, to which the sandpaperlike texture of the plates is due, break off readily if scraped); greatest diameter of plates not often exceeding 5 mm 9
8b Calcareous plates on upper surface without small nodules; greatest diameter of plates in larger specimens (at least 5 cm long) sometimes exceeding 1 cm, and usually at least 5 mm in smaller specimens (general color reddish brown; tentacles red; common shallow water species, and sometimes intertidal)  Psolus chitonoides
9a Length up to 3 cm; general color pinkish or lavender; greatest diameter of calcareous plates about 3 mm (common subtidal species) Psolidium bidiscum
(Psolidium bullatum in key)
9b Length up to 6 cm; general color not pinkish or lavender; greatest diameter of calcareous plates in larger specimens (3-6 cm long) about 5 mm Psolus squamatus
10a Length commonly 20-25 cm, but cometimes attaining 35 cm; general body color usually reddish brown, sometimes with a purplish tinge, but the buccal tentacles bright orange or orange-brown, and the introvert about the same color; common intertidal and subtidal species, usually in crevices and between rocks  Cucumaria miniata
10b Length rarely exceeding 20 cm (Lambert, 26 cm) (and in most species, other than Havelockia benti and Cucumaria fallax, not often exceeding 10 cm); general body color not reddish brown, and the buccal tentacles and introvert not bright orange or orange-brown (they may, however, be pale orange or pale brown) 11
11a General body color (the buccal tentacles and introvert may be different) white, cream, yellowish, pale orange, pinkish, brown, or tan, but neither dark nor conspicuously speckled with dark pigment (Havelockia benti, whose color ranges from pale orange to brown, often has small dots of brown pigment, but these contribute to a nearly uniform coloration rather than to conspicuous speckles) 12
11b Body either dark (often blackish) or conspicuously speckled with dark pigment 19
12a Body tapered at both ends (the posterior end may look like a tail) and curved at least slightly (sometimes the body is nearly U-shaped) 13
12b Body not obviously tapered at either end and not curved 15
13a Skin with the texture of fine sandpaper; perforated ossicles of body wall triangular to oval (length up to 10 cm, but commonly 5 or 6 cm) Pentamera pseudocalcigera
13b Skin rather smooth to the touch, not at all like sandpaper; perforated ossicles of body wall diamond-shaped, circular, or star-shaped 14
14a Body plump, decidedly curved, and with the posterior portion tapering quickly to a nipplelike tail; perforated ossicles of body wall circular to star-shaped and with an obvious central spine  Pentamera populifera
14b Body not especially plump, and only slightly curved, the posterior portion not tapering so quickly that there is a tail; most ossicles of the body wall diamond-shaped, with 4 large perforations in the central portion (there are also a few smaller, circular plates that have minute spinelets on one surface) Pentamera lissoplaca
15a Tube feet not restricted to the ambulacra; general body color light brown, but sometimes pale orange; length up to 20 cm Havelockia benti
15b Tube feet restricted to the ambulacra (although the rows of tube feet may be irregular); general body color white, yellowish, pale orange, pale brown, or tan; length not often exceeding 10 cm (except in Cucumaria fallax, whose length may reach 15 cm) 16
16a General body color pale brown, tan, or yellowish; length up to 15 cm (Lambert, 26 cm); body slimy when the animal is alive (introvert white or whitish; buccal tentacles faintly pinkish or yellowish; subtidal, mostly under rocks in cobble) Cucumaria pallida
16b General body color white to pale orange (not brown or tan); length rarely exceeding 10 cm; body not slimy 17
17a Length not often more than 3 cm; perforated ossicles of body wall with numerous knobs and spines on the one surface (rare subtidal species) Pentamera trachyplaca
17b Length commonly 5-10 cm; perforated ossicles of body wall without knobs and spines (common intertidal and subtidal species) 18
18a Tube feet slender (when the animal is relaxed), their length usually less than the width of the interambulacral areas; color nearly pure white; body wall thin; animal often covering itself with pieces of algae, bits of shell, and other foreign material Eupentacta pseudoquinquesemita
18b Tube feet rather stout (when animal is relaxed), their length usually greater than the width of the interambulacral areas; color white to pale yelllow or pale orange; body wall tough; animal not often covering itself with foreign material  Eupentacta quinquesemita
19a Prevailing color whitish or yellowish, with purple, brown, or black speckles Cucumaria piperata
19b Color almost uniformly grayish, grayish brown, or blackish (albinistic specimens occur, however) 20
20a With many tube feet between the ambulacra; ossicles of body wall button-shaped, with 4 holes; length up to about 5 cm; subtidal (Identified in 1996 key as Cucumaria lubrica) Pseudocnus curatus
20b With few if any tube feet between the ambulacra; ossicles of body wall neither button-shaped nor with 4 holes; length up to about 2.5 cm; intertidal, and usually in beds of Mytilus californianus Cucumaria pseudocurata

Taxonomic Levels Represented in This Key:

  Apostichopus californicus
  Cucumaria miniata
  Cucumaria pallida
  Cucumaria piperata
  Eupentacta quinquesemita
  Psolidium bidiscum
  Psolus chitonoides
  Pseudocnus curatus

Page created by {Kelly Williams}, 7-2002
Edited by Hans Helmstetler 12-2002, Dave Cowles 2005, 2006