Isostichopus maculatus subsp. phoenius
Creators: name: Borrero-Pérez, Giomar H.
name: Solís-Marín, Francisco A.
name: Lessios, Harilaos
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Synallactida
Stichopodidae
Isostichopus
Isostichopus maculatus
Isostichopus maculatus phoenius (clark, 1922)

description: Isostichopus maculatus phoenius (Clark, 1922)
Figs 1K–Y, 3A–D, 4B, 5A, 9, 10B, 11B, 15–18; Tables 1–3
Stichopus badionotus var. phoenius Clark, 1922: 60.
Stichopus badionotus var. phoenius – Clark 1933: 109. — Deichmann 1930: 82.
Isostichopus badionotus – Gómez-Maduro & Hernández-Ávila 2011: 223, figs k–l (at least one specimen). — Borrero-Pérez et al. 2012: 175, figs a, d.
Stichopus sp. – Agudelo & Rodríguez 2015: 51–52, figs 1–3. — Vergara & Rodríguez 2015: 1022, fig. 1b.
Isostichopus sp. – Invemar 2015: 115. — Vergara & Rodríguez 2015: 1022, fig. 1b; 2016: 130–137. — Martínez et al. 2016: 15, fig. 1, 22, fig. 6. — Vergara et al. 2018: 39–41, figs 4–6. — Acosta et al. 2020: 1–14, fig. 1; 2021: 1–17.
Isostichopus sp. nov. – Agudelo-Martínez & Rodríguez-Forero 2017: 73.
Isostichopus sp. aff. badionotus – Agudelo-Martínez & Rodríguez-Forero 2017: 6, figs 3–4. — Arias-Hernández et al. 2017: 278–289. — Fontalvo-Martínez & Rodríguez 2017: 95. — Medina-Lambrano et al. 2017: 175.
Isostichopus isabellae n. sp. – Vergara et al. 2018: 40, fig. 4. Not an available name.
Isostichopus maculatus phoenius – Borrero-Pérez et al. 2022: 180, 186.
Isostichopus sp. ‘phoenius’ – Purcell et al. 2023: 148–149.
Original name
Stichopus badionotus var. phoenius Clark, 1922.
Current status
Isostichopus maculatus phoenius (Clark, 1922).
Name-bearing type
Holotype MCZ HOL-1182.
Type locality
Buccoo Reef, Tobago.
Diagnosis
Small dark spots surrounded by a clear halo and a dark thin line on white blotches on the background; semi-translucent and rugose body wall (Figs 1K–Y, 17–18); mtDNA divergence from other species of the genus> 7.7% in COI-Fr1 (barcoding region),>10.1% in COI-Fr2 and>7.9% in 16S; between subspecies 1.4%, 1,9% and 0.4%, respectively (Table 2).
Material examined
Holotype
TRINIDAD AND TOBAGO • spec. uniform color pattern (L = 135 mm); Tobago, Buccoo Reef; 11.179396° N, 60.811479° W; 5 Apr. 1916; J. Mills leg.; living under or among rocks; MCZ HOL-1182.
Other material
GULF OF MEXICO – USA • 1 spec. (contracted); Texas, Stetson Bank; 28.17° N, 94.28° W; 28 Jun. 2005; depth 22 m; M. Wicksten leg.; USNM 1080469 • 1 spec. (L = 120 mm); Texas, Stetson Bank; 24 Oct. 1971; J. Teerlings leg.; USNM 1096856 • 1 spec. (L = 135 mm); Texas, North Padre Island; 26.82° N, 97.32° W; T. Shirley leg.; USNM E17227 • 2 specs (L = 95–195 mm); Florida, Tortugas, Bird Key; 24.6185° N, 82.8854° W; Jun. 1917; H. Lyman Clark, Carnegie Expedition exped.; MCZ HOL-1213. – Mexico • 2 specs; Veracruz, Bajos de Tuxpan, off Tuxpan; 21 Apr. 1994; J.D. Aghub leg.; ICML-UNAM 5.14.11 • 2 specs; Veracruz, Isla Sacrificios; 26 Jan. 1962; E. Caballero leg.; ICML-UNAM 5.14.28 • 2 specs; same locality as for preceding; 24 Jan. 1957; M.E. Caso leg.; ICML-UNAM 5.14.30 • 1 spec.; same locality as for preceding; 26 Jan. 1957; ICML-UNAM 5.14.34 • 1 spec.; Veracruz, Isla Sacrificios; 19.1749361° N, 96.09303056° W; 14 May 1997; depth 3 m; A. Medina leg.; rocky bottom; ICML-UNAM 18302 • 1 spec.; Veracruz, Isla Lobos; 21.4541667° N, 97.22500001° W; 14 Jun. 1976; depth 3 m; Acropora reef; ICML-UNAM 11459 • 1 spec.; Veracruz, Isla de Enmedio, Anton Lizardo; 19.1144444° N, 95.93583333° W; 5 Apr. 2005; depth 1–2 m; F. Solís-Marín leg.; on sandy bottom; ICML-UNAM 18303.
CARIBBEAN SEA – Belize • 2 specs (L = 120–180 mm); Coco-Plum Key, edge of mangrove swamp; 16.877841° N, 88.120048° W; 2 May 1972; R. Larson leg.; USNM E18639. – Panama • 1 spec. (L = 130 mm); Bocas del Toro, Cayo Adriana; 9.2405278° N, 82.1734167° W; 30 May 2013; depth 5 m; G. Borrero-Pérez and A. Castillo leg.; mixed bottom of sand, sponges and corals, IpBT5; USNM 1659468 • 1 spec. (L = 135 mm); same data as for preceding; IpBT7; MBMLP-IpBT7 • 1 spec. (L = 170 mm); same data as for preceding; IpBT21; USNM 1659473 • 1 spec. (L = 140 mm); same data as for preceding; IpBT22; USNM 1659474 • 1 spec. (L = 138 mm); same data as for preceding; IpBT23; USNM 1659475 • 1 spec. (L = 170 mm); same data as for preceding; IpBT25; USNM 1659476 • 1 spec. (L = 160 mm); same data as for preceding; IpBT43; USNM 1659477 • 1 spec. (L = 150 mm); same data as for preceding; IpBT44; USNM 1659478 • 1 spec. (L = 185 mm); same data as for preceding; IpBT53; USNM 1659479 • 1 spec. (L = 150 mm); same data as for preceding except 31 May 2013; on mixed bottom of sand, sponges and corals, completely hidden in a crevice between sponges, IpBT26; TpBT0026 • 1 spec. (L = 160 mm); same data as for preceding; MBMLP IpBT27 • 4 specs (L = 135–180 mm); same data as for preceding; Ip8, 24, 28, 29 BT; TpBT0008, TpBT0024, TpBT0028, TpBT0029 • 1 spec. (L = 130 mm); Bocas del Toro, STRI research station; 9.3488611° N, 82.2585° W; 4 Jun. 2013; depth 5 m; G. Borrero-Pérez leg.; mixed bottom of sand, corals and isolated seagrass, exposed, between coral colonies, IpBT131; USNM 1659469 • 1 spec. (L = 130 mm); Bocas del Toro, Popa Island Cay; 9.2495° N, 82.1815279° W; 6 Jun. 2013; depth 7 m; G. Borrero-Pérez and A. Castillo leg.; mixed bottom of sand, corals and sponges at the reef fringe, completely hidden, under a loose coral head and among rubble coral, IpBT190; USNM 1659470 • 1 spec. (L = 140 mm); Bocas del Toro, near Popa Island Cay; 9.2541944° N, 82.1829444° W; 6 Jun. 2013; depth 2 m; G. Borrero-Pérez and A. Castillo leg.; mixed bottom dominated by Porites porites, with isolated seagrasses, octocorals and sponges, exposed, IpBT191; USNM 1659471 • 1 spec. (L = 125 mm); same data as for preceding; depth 3 m; IpBT192; USNM 1659472 • 1 spec.; Galeta; 9.4018444° N, 79.86053056° W; 15 Dec. 2015; depth 2 m; G. Borrero-Pérez leg.; mixed bottom of rocky, corals and isolated seagrass, exposed, IpGa8; Tiss-IpGa8 • 1 spec.; same data as for preceding; IpGa11; Tiss-IpGa11 • 1 spec.; same data as preceding, IpGa209; Tiss-IpGa209 • 1 spec. (L = 100 mm); Galeta; 9.4018444° N, 79.86053056° W; 17 Sep. 2016; depth 3 m; G. Borrero-Pérez leg.; mixed bottom of corals and rocks, exposed but camouflaged between Porites porites, IpGa269; Tiss-IpGa269 • 1 spec. (L = 158 mm); same data as for preceding; depth 1 m; A. Calderón leg.; completely hidden inside rocks, IpGa223; USNM 1659480 • 1 spec. (L = 90 mm); same data as for preceding; IpGa224; USNM 1659481. – Colombia • 1 spec. (L = 120 mm); Magdalena, Banco de las Ánimas; 11.0397778° N, 74.39919445° W; 1 Dec. 2013; depth 15 m; G. Borrero-Pérez and N. Ardila leg.; rocky bottom, anterior part exposed, IpBA313; INV EQU4144 • 1 spec. (L = 130 mm); same data as for preceding; IpBA314; INV EQU4146 • 1 spec. (L = 140 mm); same data as for preceding; rocky bottom, partially exposed within crevices between rocks, concealed by spines of Diadema antillarum, IpBA315; INV EQU4147 • 1 spec.; same data as for preceding; depth 4.5 m; IpBA319; INV TEJ1336 • 1 spec. (L = 25 mm); Magdalena, Bahía del Rodadero; 11.2070556° N, 74.2303916° W; 23 Jul. 2017; depth 1 m; G. Borrero leg.; hidden under a rock in a mixed bottom of sediment and small rocks, IpRod; INV EQU4565 • 1 spec. (L = 125 mm); La Guajira, El Pájaro-Tawaya; 11.7308333° N, 72.70436111° W; 9 Sep. 2013; depth 4.5 m; E. Ortíz and J. López leg., IpGV82; INV TEJ1257 • 1 spec. (L = 100 mm); same data as for preceding; IpGV83; INV TEJ1258 • 1 spec. (L = 125 mm); same data as for preceding; IpGV84; INV TEJ1259 • 1 spec. (L = 160 mm); same data as for preceding; IpGV86; INV TEJ1261 • 1 spec. (L = 170 mm); same data as for preceding; IpGV90; INV TEJ1265 • 1 spec. (L = 120 mm); same data as for preceding; IpGV108; INV TEJ1269 • 1 spec. (L = 180 mm); same data as for preceding; IpGV117; INV TEJ1272 • 1 spec.; La Guajira, Cabo de la Vela; 12.2086422° N, 72.1674894° W; 28 Oct. 2011; depth 2 m; G. Borrero-Pérez and C. Díaz leg., IpGV1; INV-TEJ1113 • 1 spec.; same data as for preceding; IpGV3; INV-TEJ1115. – Trinidad and Tobago • 4 specs (L = 90–115 mm); Tobago, Buccoo Bay; 11.177882° N, 60.811479° W; Apr. 1916; J. Mills leg.; MCZ HOL-1181. – Jamaica • 1 spec. (L = 120 mm); Kingston Harbor, Port Royal, Drunken Man’s Cay; 17.905085° N, 76.845067° W; 3 Sep. 1959; H. Lyman Clark leg.; MCZ HOL-4282. – Antigua and Barbuda • 2 specs (L = 90–120 mm); Antigua Island, English Harbor; 1 Jul. 1918; C. Nutting leg.; USNM 1283367 • 1 spec. (L = 170 mm); Antigua Island, Falmouth Bay; 17° N, 61.7667° W; 1918; J. Henderson leg.; USNM E41458.
Description
EXTERNAL APPEARANCE. Medium sized species, preserved and live ex situ specimens examined range from 25 to 260 mm in length (n = 68, holotype: 130 mm long and 40 mm wide). Body loaf-like, length/ width ratio 3.7± 0.8 (n = 38, 3.2–5.5, holotype 3.2). Rounded posteriorly and anteriorly (Fig. 15A), quadrangular in cross section (Figs 17–18). Live specimens also tapering slightly posteriorly and widened anteriorly when the animal is relaxed (Fig. 17E, O), or when it is coming out of its crevice, especially when only the anterior part of the body is exposed (Fig. 18O). Body wall firm and thick (0.5 to 4 mm thick in the holotype). Anus supra-terminal, circular and surrounded by large papillae. Mouth directed ventrally in live and preserved animals, encircled by a collar of large papillae (2–4 mm long in the holotype). Large peltate tentacles 20, about 7–9 mm long, 6 mm shield width, with indentations 0.5–3 mm deep. Dorsal papillae medium to large, conical, and spiky (although some of them somewhat rounded) ending in a sharply pointed tip (5 to 10 mm high; 5 to 8 mm wide); some smaller papillae rounded and scattered irregularly; most of the largest dorsal papillae arranged in two dorsal irregular rows along each edge, defining the quadrangular shape. Holotype covered with medium size conical papillae (up to 4 mm high and 5 mm wide at the base), most of them flattened and not very conspicuous. Lateral papillae large and spiky, sharply defining the dorsal and ventral surface (Figs 17–18); in the holotype they are larger than dorsal ones (up to 5 mm high and 5 mm wide at the base) (Fig. 15A). Ventral surface covered with cylindrical, large pedicels (2–4 mm long and 0.5 mm wide in the holotype) arranged in three longitudinal rows (Fig. 15A).
COLOR AND BODY WALL APPEARANCE. Living specimens are semi translucent and appearing slightly rugose (Figs 1K–Y, 17–18). Color extremely variable; four main color patterns (Figs 1, 17–18). The first three patterns are similar to those of I. maculatus maculatus, with some variations in the second (DW) and third (LDS), with regard mostly to the white spots as white granules: (1) Uniform pattern (U) (Fig. 1K– L): uniform brown, green, or red. Specimens of this uniform color are rare; in most cases at least a very small white blotch is present. (2) Dark and white color pattern (DW) (Fig. 1M–T): red, orange, or brown background with white irregular blotches of different shapes and sizes, arranged in longitudinal or transversal orientations; usually with a dark line surrounding the white blotches, or with only a line in very small blotches. Blotches markedly or gently rugose, with small dark spots surrounded by a clear halo and a dark thin line; larger spots occasionally inside the white blotches. Ventral surface with a margin at the outer edge of the same color background as the dorsal side. Middle area sometimes of almost uniform color or sometimes off-white with small spots and scattered or abundant brown blotches, or some of the same color as the margin. (3) Light and sharp dark color pattern (LSD) (Fig. 1U–W): lighter background in brown, beige, white, pink, and sharp darker irregular blotches in brown or brown-orange, of different size and irregularly arranged. Lighter background area markedly or gently rugose, with or without small dark spots surrounded by a clear halo and a dark thin line. Ventral surface off-white with scattered or abundant small brown spots and blotches, without margin at the outer edge. (4) Light and blurry dark pattern (LBD) (Fig. 1X–Y): similar to the LSD pattern, but with lighter background in brown, white, pink colors and blurry darker irregular blotches in brown or brown-orange color of different size and irregularly arranged. Spiral lines in the papillae more conspicuous than those in I. maculatus maculatus. Spiral lines in dorsal and lateral papillae in the four described patterns, although more conspicuous in the patterns 3 (LSD) and 4 (LBD). Sharply pointed tips of the papillae white, light yellow, or lighter than the base. Collar papillae usually white translucent, with the spiral lines very marked in a dark color. Tentacles and pedicels white to light yellow-brown. Specimens preserved in alcohol lighter than live ones but with white blotches with the small dark spots of patterns 2 (DW), 3 (LSD) and 4 (LBD) persisting (Fig. 15C–G). According to Clark (1922), the live holotype was semi translucent with the entire back and sides bright carmine-red (Uniform pattern), the tentacles, pedicels, and median ventral surface gray. Preserved dorsal coloration of the holotype light yellow-brown. Body wall somewhat translucent and rugose. Some of the largest papillae with a spiral line from the base to the tip; tentacles, ventral surface, and pedicels of the same color as the dorsal side; some darker small stains among the pedicels on the ventral side; tips of the pedicels darker than the tube (Fig. 15A). Juveniles semi translucent and appearing slightly rugose; color pattern in juveniles (40–50 mm) the same as in adults; the spiral lines in dorsal and lateral papillae present (Fig. 17D, B’–C’).
INTERNAL ANATOMY (Based on MCZ HOL-1182 (holotype), USNM 1659481, USNM 1659476, USNM 1659479, specimens 90–190 mm). Calcareous ring of the holotype stout, 13 mm in diameter; radial elements almost as wide as long (5 mm wide and 6 mm long) with four anterior small lobes; posterior projections 2 mm long in the dorsal radial plates; middle ventral radial plates without posterior projections; interradial plates 3 mm wide and 3 mm long, pointed anteriorly and with a concave posterior margin. Proportion of radial plates in other examined specimens similar to the holotype (L = 90 mm: 2.9 mm wide, 3.3. mm long; L = 190 mm: 6 mm wide, 7 mm long); posterior projections proportionally equal to radial plate size during growth; interradial plates stouter in large specimens (L = 90 mm: 2 mm wide, 1.4 mm long; L = 190 mm: 3 mm wide, 4 mm long) (Fig. 4B). Holotype stone canal irregularly helical, about 10 mm long, including the flat madreporite, leaf-like 2.5 mm long, attached to the mesentery; stone canal variable in size not related to body size (L = 90 mm: 8 mm; L = 130 mm: 10 mm; L = 160 mm: 14; L = 185 mm: 12 mm). Tentacle ampullae in the holotype 16–18 mm long by 1–1.5 mm wide, and 4.5 mm long in the smallest specimen (L = 90 mm). One sac-like Polian vesicle in the holotype 14 mm long by 5.5 mm wide, and 13 mm in the other specimens (L = 160 mm and 185 mm). Gonads in two tufts, one on either side of dorsal mesentery, branched in cylindrical tubes about 0.5 mm or less wide, not very bulky, extending 16 mm left and 12 mm right along the length of the body, filled with male gametes in the holotype (Fig. 11B). Gonads present in examined specimens 130 mm and 190 mm long, but absent in the smallest (L = 90 mm). In the holotype, longitudinal muscles divided, about 4 mm wide, attached to body wall medially and laterally every 2 mm. Specimen L = 90 mm longitudinal muscles 3 mm wide; and L = 195 mm 10 mm wide. Respiratory trees in the holotype inserted near the anterior cloaca with a common stem of 15 mm; right tree about 55 mm long and left 65 mm long, extending in association with the intestine; in other specimens, right tree also usually shorter than the left.
OSSICLES (based on MCZ HOL-1182 (holotype), USNM 1659481, USNM 1659472, USNM 1659476, USNM 1659479, INV EQU4565 (juvenile, for dorsal papillae), USNM 1659477 (SEM images), specimens 25–190 mm).
Dorsal papillae with tables, thin C- and S-shaped rods, perforated plates, large, curved rods and worm-like rods (Fig. 16A). Perforated plates and worm-shaped rods not found in the 25 mm specimen. Numerous few thin C-shaped rods, and rare S-shaped rods, 45–98 µm (x = 71 µm), usually in the papillae, especially towards the tip, varying in abundance in the same specimen. The length of C-shaped rods increasing in relation to body length in specimens from 25 mm to 190 mm long (Fig. 9A). Numerous table ossicles 31–78 (x = 52) µm high and 39–84 (x = 64) µm across disc (holotype 35–53 µm high; 39–51 µm across the disc); juveniles 31–46 (x = 38) μm high. Spires composed of four usually parallel pillars, or slightly constricted medially, distally, or proximally to the disc; pillars ending in triplets of blunt spines forming a wide crown; many minute spines in the 25 mm long specimen, with one crossbeam connecting adjacent pillars. Disc margins smooth and wide; with one rounded central perforation and 8 to 12 peripheral holes, usually arranged in one simple ring; tables near the top with 4 to 10 extra perforations arranged in more than one ring. Tables at top of the papillae larger, more square, with a wider disc, and with more perforations than those in the base of the papillae; those of the base similar to those of the body wall (Fig. 10B). Changes of table shape during growth not remarkable, but size of C-shaped rods and height of tables increasing in relation to body length (Figs 9A–B, 10B); disc diameter of tables without substantial change during growth (Figs 9C, 10B). Few perforated plates, located in the papilla tip, with large and few perforations, larger in the center of the plate, 72–158 µm across, absent in 20 mm juveniles, and rare in other small specimens. Slightly or strongly curved rods usually with quadrangular projections distributed mostly in the middle, occasionally perforated, 150–377 µm long, increasing in size in relation to the body length (Fig. 16A). Numerous small slightly or strongly spinous worm-shaped rods 78–197 µm long, without substantial change in size during growth (Figs 15B, 16A).
Dorsal body wall only with tables and few C-shaped ossicles 45–68 µm long, found only in the holotype and in one of the examined specimens (L = 125 mm) (Figs 10B, 16A). Numerous tables similar to those from papillae but smaller in size 30–58 (x = 44) μm high and 31–74 (x = 49) µm across the disc, with regular discs with one ring of 8–10 holes. In the holotype tables 35–47 µm high and 31–41 µm across disc, usually with 9–12 perforations arranged in one simple ring.
Pedicels with tables, thin C-shaped rods, perforated plates, large and curved rods, and end plate (Fig. 16B). A few C-shaped rods 79–98 (x = 87) µm long. Numerous table ossicles 27–47 (x = 36) μm high and 27–71 (x = 53) µm across the disc (holotype 29–40 μm high; 39–59 µm across the disc); shape of tables similar to those from the dorsal papillae and body wall, central perforation usually bigger and not rounded, with four points that interrupt the simple ring of holes on the disc. Tables with the same pattern during growth as dorsal papillae; height of tables increasing with body length (table height L = 25 mm: 27–39 µm; L = 170 mm: 38–47 µm); disc diameter not notably changing with body size (disc diameter L = 25 mm: 47–71 µm; L = 170 mm: 52–67 µm). Numerous elongated perforated plates, with numerous perforations larger and elongated in the center of the plate, 171–392 µm long; slightly curved rods 207–467 µm long, usually with wide perforated expansions in the middle; end plates 372–602 µm across, increasing in size during growth (Fig. 16B).
Ventral body wall in holotype with numerous tables similar to those from pedicels (32–40 µm high; 35–58 µm across disc) and a few thin C-shaped rods (78–79 µm long).
Tentacles with tables and rods (Fig. 16C). A few table ossicles 36–70 μm across disc (holotype 36– 46 μm); spire low, composed of four pillars, some of them incomplete, only two or three joined at the top, without crossbeams connecting adjacent pillars; discs with a large and not rounded central perforation, with four points and usually no more than four peripheral perforations with margins smooth and thin. Numerous strongly and slightly curved spiny rods 34–722 µm long (holotype 34 to 294 µm), increasing in size during growth.
Mouth membrane with tables, C-shaped ossicles, and simple rods (Figs 11B, 16D). Numerous large tables 70–102 µm high and 68–160 µm across disc (holotype 85–87 µm high; 100–160 µm across disc); spire well developed, composed of at least ten pillars, that are joined at the top, forming a very dense crown of spines, without distinguishable crossbeams connecting adjacent pillars; spire is flat. Table discs with many peripheral perforations arranged in two or three rings; margins spinous and thin, sometimes reduced to the same width as the spire. Flat table spires in all specimens from Panama, taller spires in specimens from other localities in the Caribbean. Some C-shaped rods 48–106 µm long (holotype 42–65 µm), and small rods 48–107 µm long in some specimens (holotype 58–107 µm).
Longitudinal muscles with thin C-shaped rods 28–53 µm long (holotype rods 30 µm) and small rods ranging from 37 to 93 µm in length (holotype 37–56 µm) (Fig. 16E). Posterior cloaca with numerous simple or bifurcated rods in 71–195 µm long (holotype 145–195 µm); some C-shaped ossicles 38– 84 µm long (holotype 38–52 µm). Anterior cloaca with large and complex tables 106–179 µm high and 73–244 µm across disc (holotype 71–113 µm high; 113–176 µm across disc) (Fig. 11B); in the holotype irregular plate-like branched rods, 133–201 µm across (Figs 11B, 16F). Respiratory trees with a few small tables, similar in shape to those of the dorsal body wall, 43–51 µm high and across the disc (holotype 43 µm high; 44 µm across the disc); few rods 54–229 µm long in some specimens (holotype 54–111 µm) (Fig. 16G). Intestine with spinose or smooth rods in a cross shape 50–122 µm long, sometimes with bifurcated ends (holotype 75–113 µm) (Fig. 16H). Gonads with delicate and long rods 187–364 µm long (holotype 187–262 µm) (Figs 11B, 16I); rods in gonads present even in the smallest specimen examined (L = 125 mm); a few small tables 48 µm high and 43 µm across disc in the holotype.
Distribution
Isostichopus maculatus phoenius is known from the Caribbean Sea and the Gulf of Mexico (Fig. 5A). We have collected it from Mexico, Costa Rica, Panama (Bocas del Toro, Galeta, San Blas) and Colombia (Banco de las Ánimas, Santa Marta, La Guajira). We also identified it from Museum specimens from the Florida Keys (MCZ HOL-1213), North Padre Island, and Stetson Bank, Texas (USNM E17227; USNM 1080469; USNM 1096856), Belize at Coco Plum Cay (USNM E18639), Jamaica (MCZ HOL-4282), Antigua (USNM E41458, USNM 1283367) and Trinidad and Tobago (MCZ HOL-1182, MCZ HOL-1181). We also identified it from photographs of living specimens from Estado de Sucre, Venezuela (Gómez-Maduro y Hernández-Ávila 2011 unpubl. photographs). Isostichopus maculatus phoenius appears to be sympatric with I. badionotus in the Caribbean Sea and the Gulf of Mexico, but more samples are needed to confirm the presence of this subspecies at other localities of the West Atlantic. Currently, I. maculatus phoenius has not been recorded in South Brazil, where I. badionotus was confirmed by DNA (Table 1). It is not possible to assess the distribution of I. maculatus phoenius from the literature, because it has been confused with I. badionotus. It is not easy to identify this subspecies from museum specimens either due to the similarity of the ossicles to those of I. badionotus and the loss of color in preserved specimens. We have only designated specimens as I. maculatus phoenius from the USNM and MCZ collection that could be clearly identified (examples in Fig. 15C–G). Bathymetric distribution 0– 22 m. Most of the specimens observed in the present study were in shallow habitats, no more than 10 m deep. Acosta et al. (2021) found this species (as Isostichopus sp.) in the upper 2.5 m. However, museum specimens (USNM 1080469) have been collected from 22 m (Fig. 15F).
Habitat
Isostichopus maculatus phoenius can be quite abundant, although, because of its cryptic habits and because its ossicles resemble those of I. badionotus, it has been overlooked for many years. Clark (1922) described the habitat of the holotype (MCZ HOL-1182, as S. badionotus var. phoenius) living under or among rocks, as were the four specimens from MCZ HOL-1181, collected along with the red holotype. Clark (1922) assigned these four specimens as subadults of I. badionotus and suggested that semi-translucent subadults of I. badionous (length less than 150 mm) with a distinctive coloration (often marked with a dark spiral line that runs from the base to tip of dorsal and lateral papillae) are common under rocks, or in crevices. However, in the light of the present results, the dark spiral line and the habitat indicate that they were I. maculatus phoenius. Isostichopus maculatus phoenius is smaller than I. badionotus and prefers a more cryptic habitat. Its activity is nocturnal. Our observations from Colombia and Panama showed that juveniles and adult individuals of I. maculatus phoenius remain completely hidden during the day under rocks or coral heads, or in cracks (Figs 17–18). Acosta et al. (2021) in Santa Marta (Colombia) found 98% of individuals of I. maculatus phoenius (as Isostichopus sp.) on rocky bottoms between cracks (upper 2.5 m depth), while 73% of individuals of I. badionotus were collected on sandy bottoms (3–7.8 m). Diurnal observations, between 9:00 am and 12:00 pm, at Punta Galeta (Panama) showed that I. maculatus phoenius can be exposed for approximately one hour, then they became completely hidden. During the observations, some individuals exposed only the anterior part of their body to feed (Fig. 18O), and only a few were found fully exposed during the day. Frequently during the time of exposure, they were partially hidden by the spines of Diadema antillarum (Philippi, 1845) (Fig. 18J, M–N). Some individuals, partially or completely exposed, seemed to be rubbing their mouths against the rocks and the leaves of Thalassia testudinum, or scraping on them. Observations made between 5:00 and 6:00 pm at some localities in the Caribbean showed that specimens of I. maculatus phoenius, previously unnoticed during the day, start to appear. Observation during the night showed individuals completely exposed on top of sponges (Fig. 18P). Purcell et al. (2023) stated that after reaching 15–20 cm in length, individuals can become less cryptic and can live on open sand flats, but this is a mistake.
Remarks
Stichopus badionotus var. phoenius was described as a variety of Stichopus badionotus on the basis of the bright-carmine red color on the dorsal side of one specimen collected in Bucco Reef, Tobago. Clark (1922) designated this specimen as the holotype (MCZ HOL-1182) (still preserved in very good condition (Fig. 15A)) and described the external morphology, ossicles, and the habitat of the type locality (Clark 1922: 59–60), and explained the etymology. Despite the distinctive color pattern of the holotype of I. maculatus phoenius, which is “a most unusual shade in a shallow-water holothurian” (Clark 1922), and despite the marked spiral lines in the papillae, I maculatus phoenius has remained unnoticed in holothurian research in the West Atlantic, perhaps because of the great color variability of both I. maculatus phoenius and I. badionotus. Since Clark (1922), S. badionotus var. phoenius was mentioned only by Deichmann (1930) and Clark (1933).
The coloration of the holotype corresponds to the first Uniform color pattern described in the present study. The semi translucent appearance, the habitat, and the worm-shaped rods in the dorsal papillae of other specimens of all color patterns are similar to the holotype. Our analyses revealed significant molecular, morphological and habitat differences from the sympatric species I. badionotus. The analyses also revealed significant morphological differences, such as ossicle shape and body coloration, from I. maculatus from the East Atlantic. However, because the molecular phylogeny shows DNA sequences of I. maculatus maculatus as nested in sequences of I. maculatus phoenius the latter is considered as a subspecies of I. maculatus. We propose that I. badionotus var. phoenius is elevated to the subspecific rank, as this is an available subspecific name (Articles 10.2 and 45.6.4 ICZN Code 1999). Isostichopus maculatus phoenius is extremely variable in coloration. Clark (1922) considered the individuals with the LSD color pattern described here as I. badionotus subadults (MCZ HOL-1181, Fig. 15G). However, spiral lines in papillae are one of the diagnostic characters of both I. maculatus maculatus and I. maculatus phoenius (Fig. 1K –H’). These spiral lines are also present in juveniles of I. maculatus phoenius (Fig. 17D, B’–C’). The characters diagnostic between the two subspecies are the small dark spots surrounded by a clear halo, the dark thin line, and the semi-translucent and wrinkled skin in I. maculatus phoenius (Fig. 1K–Y). This color characteristic was the most useful character in identifying museum material (Fig. 15C–G). Some specimens, such as USNM 1080469 with almost a uniform color pattern, possess small brown spots (Fig. 15F), allowing certain identification. In contrast to I. maculatus phoenius, I. maculatus maculatus is characterized by white spot like granules on the opaque and smooth skin, as mentioned by Greeff (1882) in the original description (Fig. 1Z –H’). In addition to spiral lines, worm-like rod ossicles found in the dorsal and lateral papillae of I. maculatus phoenius are a shared character between the two subspecies, although less common in I. maculatus maculatus. They were reported by Cherbonnier (1975: 633, fig. 2o) as “rare imperforate rods”. Worm-like rod ossicles can be useful in distinguishing I. maculatus phoenius from I. badionotus. These rods were observed in specimens from Colombia and Panama, and although uncommon in some specimens, they were abundantly present in the holotype (Fig. 15B).
Examination of dorsal papillae in four specimens (and several that were not measured) of I. maculatus phoenius with body lengths 25 to 185 mm long showed that C-shaped ossicle and table height increase with body size (Fig. 9A–B). Spines at the crown spires are thick and strong in larger specimens. Contrary to I. badionotus, table disc diameter and number of holes remain almost constant through growth in I. maculatus phoenius, with only a slight tendency to increase with size (Fig. 9C). Tables in the papillae were larger than those in the body wall (Fig. 10B). Juveniles of I. maculatus phoenius are not easy to distinguish from those of I. badionotus based on ossicles. The best character is the color pattern, especially the spiral lines (Figs 8, 17).
Separate analyses of COI-Fr1 (Barcoding region) and 16S DNA sequences confirm that Isostichopus sp. reported by Wen et al. (2011) and Vergara et al. (2018: Morphotype III, Isostichopus sp., Isostichopus isabellae n. sp.) is I. maculatus phoenius, because their sequences in GenBank cluster with ours in this subspecies (Fig. 3B, D; Table 1). Sequences of Vergara et al. (2018) of their Morphotype I and II of I. badionotus, fall in the same clade as our sequences of I. badionotus (Fig. 3B, D; Table 1). These molecular results, in addition to external morphology and coloration shown in several figures in various published articles, support the fact that several names used previously are also I. maculatus phoenius: Stichopus sp. (in Agudelo & Rodríguez 2015); Isostichopus sp. (in Vergara & Rodríguez 2015, 2016; Acosta et al. 2020, 2021); Isostichopus sp. aff badionotus (in Agudelo-Martínez & Rodríguez-Forero 2017; Arias-Hernández et al. 2017); and Isostichopus isabellae n. sp. (in Vergara et al. 2018). In addition, GenBank sequences JN207495 and JN207564 reported as I. badionotus by Honey-Escandón et al. (2012), actually belong to I. maculatus phoenius (Fig. 3B, D).
Vergara et al. (2018) presented valuable information about Isostichopus. Their figure 4 is useful for distinguishing I. maculatus phoenius from I. badionotus, depicting specimens of the “Light and sharp dark” color pattern (Vergara et al. 2018: 40, fig. 4a, c), and “Dark and White” color pattern of I. maculatus phoenius (most specimens in Vergara et al. 2018: 40, fig. 4b, e). However, some aspects of the taxonomic names they used, their morphological characterization (especially of ossicles) and the habitat information they presented create confusion: (1) they use two different names, Isostichopus sp. and Isostichopus isabellae n. sp., for the “new proposed species – Morphotype III”. (2) although they mentioned a new proposed species, they also stated that “it is quite possible that the morphotype III encountered here represents a described species currently relegated into the synonymy of I. badionotus ”. (3) Vergara et al. ’s figures 6e and 6f show a mix of ossicles from tentacles (large and thick unperforated rods) and from pedicels from the ventral body wall (tables, rods, perforated plates and end plate), mistakenly describing them as ossicles from dorsal body wall in the figure legend.
Biology
Despite the taxonomic confusion, even as to the genus, there is recent information about reproductive biology, gametogenesis, spawning and larval development of Isostichopus maculatus phoenius. Agudelo & Rodríguez (2015) and Agudelo-Martínez & Rodríguez-Forero (2017) reported natural spawning in captivity from July to November during two consecutive years, concluding that I. maculatus phoenius has an annual reproductive cycle in Colombia, with a single spawning event during the warmer months of the year (July to November), the same cycle as reported for I. badionotus at other locations of the Caribbean Sea (Guzmán et al. 2003; Foglietta et al. 2004; Zacarías-Soto et al. 2013; Invemar 2015). Acosta et al. (2021) confirmed that both I. maculatus phoenius (named by them Isostichopus sp.) and I. badionotus around Santa Marta (Colombia) showed a reproductive season from September to November, closely related to the increase in water temperature and rainfall. These authors reported a sex ratio of 1:1, similar to I. badionotus. However, they reported that populations of I. maculatus phoenius were smaller in the average size and weight (193± 52 mm and 178 ± 69 g) and in size and weight at first maturity (175 mm and 155 g). Acosta et al. (2021) also reported one hermaphrodite individual in this subspecies. Agudelo & Rodríguez (2015) and Agudelo-Martínez & Rodríguez-Forero (2017) were able to rear larvae to the doliolaria stage, which was reached 28–30 days after hatching at 26°C. Acosta et al. (2020) reported 22 days to the doliolaria and juveniles of 621.8 ± 12.7 μm (±SE) in length 7 days later at 26°C, the temperature in which the highest growth rates, and survival were obtained. Measurement of the growth of I. maculatus phoenius under different conditions of light and different temperatures (21°C, 23°C, 25°C), indicated that growth was best promoted by darkness at 23°C for individuals of small size and at 25°C for those of medium size (Fontalvo-Martínez & Rodríguez 2017). The histology of the gut of I. maculatus phoenius has been described (Vergara & Rodríguez 2015: fig. 1b, as Isostichopus sp.). Density of 0.1 ind/km 2 (0.001 ind/ha) has been reported in Magdalena, Colombia (Invemar 2015, as Isostichopus sp.).
Conservation status
As a previously unrecognized species that has been overlooked and confused with I. badionotus, I. maculatus phoenius has not been included in the IUCN Red List of threatened species. However, I. maculatus phoenius is being fished together with I. badionotus. Because of its cryptic habits, artisanal fishermen search for it under rocks, or at night. Wen et al. (2011) found DNA sequences of this subspecies in commercial food products (frozen and dried) purchased from local retail markets in Guangzhou, China (GenBank FJ794474) (Fig. 3B). The species has also been identified in photographs of specimens harvested in Colombia (Invemar 2015; G.H. Borrero-Pérez pers. obs.). Recently, the subspecies was included in the FAO catalog of commercially important sea cucumbers of the world (Purcell et al. 2023, as Isostichopus sp. ‘ phoenius ’) as a high-value species in Asian dried seafood markets. The average price of dried I. maculatus phoenius in Hong Kong is US $ 358 kg-1 (Purcell et al. 2023). Interest to include it in fishery and for aquaculture in Colombia has been mentioned by Rodríguez-Forero et al. (2013), Agudelo & Rodríguez (2015), Vergara & Rodríguez (2016), Agudelo-Martínez & Rodríguez-Forero (2017) and Arias-Hernández et al. (2017). Vergara & Rodríguez (2016) found that the chemical composition of the muscle of I. maculatus phoenius (as Isostichopus sp.) was similar to that of freshly internationally traded sea cucumbers. Arias-Hernandez et al. (2017) have formulated a dry-salting protocol for I. maculatus phoenius (as I. sp. aff. badionotus). Martínez et al. (2016) presented a manual for the cultivation and processing of sea cucumbers including I. maculatus phoenius (as Isostichopus sp.). As this taxon is traded as I. badionotus, it is subject to the same regulations in fisheries (Purcell et al. 2023); however, differences between this species and I. maculatus phoenius in size, habitat and behavior show the necessity to treat them as different species to ensure sustainable exploitation.
description: Published as part of Borrero-Pérez, Giomar H., Solís-Marín, Francisco A. & Lessios, Harilaos, 2024, Understanding the color variability and resolving taxonomic confusion in the sea cucumber Isostichopus badionotus (Echinodermata, Holothuroidea): a revision of the genus Isostichopus, pp. 1-96 in European Journal of Taxonomy 949 (1) on pages 50-62, DOI: 10.5852/ejt.2024.949.2641, http://zenodo.org/record/13710645