Chiridota heheva, Pawson, David L. & Vance, Doris J., 2004

Pawson, David L. & Vance, Doris J., 2004, Chiridota heheva, new species, from Western Atlantic deep­sea cold seeps and anthropogenic habitats (Echinodermata: Holothuroidea: Apodida), Zootaxa 534, pp. 1-12 : 3-10

Chiridota heheva new species

Figures 1–3 .

Diagnosis: Inhabitant of bathyal/abyssal cold seeps and anthropogenic (wood) habitats. Tentacles with terminal discs carrying approximately 20 discrete, finger­like digits, which are free and extended during feeding. Tentacles equally spaces; no ventral gap. Color in life blue to bluish­purple, with numerous conspicuous whitish spots (wheel papillae) in all interradii.

Material Examined: Nineteen specimens, and one fragment, all deposited in the National Museum of Natural History, Smithsonian Institution, Washington DC, USA.

HOLOTYPE, USNM E51169 , R/V Arctic Discoverer, approximately 395 kilometers east of Savannah, Georgia, wreck of S.S. Central America, 32° N, 77°W, 2,200 meters, September, 1991, 1 specimen, collected by E. Herdendorf. Total length 45 mm.

PARATYPES:

1. USNM E51168 , R/V Arctic Discoverer, approximately 395 kilometers east of Savannah, Georgia, wreck of S.S. Central America, 32° N, 77° W, 2,200 meters, September, 1991, 3 specimens, collected by E. Herdendorf. Total length 113 mm, 64 mm, 30 mm.

2. USNM E51170 , R/V Arctic Discoverer, approximately 395 kilometers east of Savannah, Georgia, wreck of S.S. Central America, 32° N, 77° W, 2,200 meters, September, 1991, 2 specimens, collected by E. Herdendorf. Total length 120 mm, 132 mm.

3. USNM E51171 , R/V Arctic Discoverer, approximately 395 kilometers east of Savannah, Georgia, wreck of S.S. Central America, 32° N, 77° W, 2,200 meters, September, 1991, 1 specimen, collected by E. Herdendorf. Total length 80 mm.

4. USNM E51172 , R/V Arctic Discoverer, approximately 395 kilometers east of Savannah, Georgia, wreck of S.S. Central America, 32° N, 77° W, 2,200 meters, September, 1991, 2 specimens, collected by E. Herdendorf. Total length 40 mm, 83 mm.

5. USNM 1014686, Lamont Doherty Geological Observatory, eastern Gulf of Mexico, Florida Escarpment, Sta: 1343, 26 ° 03' N, 84° 54' W, 3,270 meters, March 9, 1984, 2 specimens, collected by B. Hecker. Total length 70 mm, 95 mm; 1 fragment, 85mm.

ADDITIONAL MATERIAL:

1. Alvin Dive 3635, Pot 3, eastern Gulf of Mexico, Florida Escarpment, seep site, 26°01.77' N, 84°55.03' W, 3,293 meters, October 28, 2000, 1 specimen, collected by C. Van Dover. Total length 43 mm.

2. Alvin Dive 3709, Blake Ridge, east of Savannah, Georgia, 32°29.41'N, 76°11.09'W, 2,178 metres, September 25, 2001, 1 specimen, collected by C. Van Dover. 64 mm.

3. Alvin Dive 1343, eastern Gulf of Mexico, Florida Escarpment, seep site, 26°02.2'N, 84° 54.9'W, 3,266 meters, March 9, 1984, 2 specimens, collected by B, Hecker. Total length 48 mm, 82 mm.

4. Alvin Dive 3635, eastern Gulf of Mexico, Florida Escarpment, seep site, 26°01.77'N, 84°55.03' W, 3,293 meters, October 28, 2000, 2 specimens, collected C. Van Dover. Total length 31,70 mm.

5. Alvin Dive 3636, eastern Gulf of Mexico, Florida Escarpment, seep site, 26°02.23'N, 84°55.03'W, 3,291 meters, October 29, 2000, 1 specimen, collected C. Van Dover. Total length 59 mm.

6 Alvin Dive 876, southeast of Puerto Rico, Deep Ocean Station No. 3, 17E57.6'N, 64E48.5'W, 3998m, 20 December 1978, 1 specimen, collected R. Turner & F. Grassle. Total length 36 mm.

Description: Body cylindrical ( Figure 1 , 2 B), greatest length in alcohol 132 mm; in life, fully expanded individuals probably exceed 200 mm in length. Diameter almost constant along length of body, approximately 5% of total length. Mouth and anus terminal. Oral disc with 12 tentacles, conspicuous, supported by well­developed calcareous ring. In a specimen 90 mm in length, oral disc is 15 mm in diameter. Smooth dark­colored body wall carries few to very numerous whitish to grayish wheel papillae in all interradii (Figure 1, 2A–B). Wheel papillae, which contain numerous wheel ossicles, range from circular to elongate oval and may average approximately 1 mm in diameter. Some specimens with few such papillae; in others a 20 mm­long area of the mid­dorsal body wall may carry 35 papillae. Largest papillae surround the anus, often forming a ring of 5 papillae up to 2 mm in diameter. These terminal papillae superficially resemble “anal teeth” of non­apodid holothurians.

Color in alcohol mostly dark purplish. In life this species is blue to bluish­grey, with papillae conspicuous as white spots ( Figure 2 A–D). Herdendorf et al. (1995) note that the color is “purple to bluish­gray”. Tentacles lighter­colored than remainder of body.

The 12 tentacles are equally spaced, with no ventral gap, and no bilateral symmetry in their arrangement ( Figure 2 E). Cylindrical tentacle stalks terminate in a disc or pad which carries up to 20 discrete, finger­like digits ( Figure 2 G), each approximately 1.0–1.5 mm long in a partially contracted state. In contracted tentacle, digits remain distinguishable as discrete structures ( Figure 2 F, 2G). In situ photographs show that the digits are fully extended when the animal is actively feeding ( Figure 2 A, 2D).

Internal anatomy similar to that in C. hydrothermica . Calcareous ring conspicuous, strong, rigid, composed of ten pieces, of which the left and right dorsal radial pieces are double (bipartite) ( Figure 3C ). Radial pieces not perforated for passage of radial nerve. Polian vesicles numerous, of varying length, usually more than 20 vesicles present. Short, tightly coiled stone canal in mid­dorsal interradius tightly coiled, terminating at conspicuous whitish madreporite attached to body wall. Gonad a bunch of short vesicles, extending 2–3 cm posteriorly in the dorsal area. Gonad of one female specimen collected in October 2000 contains numerous eggs 97–125µm in diameter (mean 110µm, standard deviation 7.14); in another female collected in March 1984, numerous apparently mature eggs present. No ciliated urns (funnels) found. Intestines of specimens from seep sites (Blake Ridge) usually contain mixture of sand grains and indeterminate flocculent material. In some specimens from Central America wreck (Paratype lots 2–6), intestine contained numerous small fragments of wood from the vessel. The specimen from Alvin Dive 876 contained flocculent material and numerous small wood fragments.

An average­sized wheel papilla from mid­body contained almost 400 wheels of typical chiridotid type, with six spokes ( Figures 3 F–I), and with inner edge of the rim carrying numerous teeth ( Figure 3 G). Wheels lie in papillae with toothed rim uppermost. At center of inner surface of wheel is the typical “star” structure ( Figure 3 F) described by Smirnov (1998). At Florida Escarpment, wheels 126–200µm in diameter (mean 177µm, standard deviation 32.70); at Blake Ridge wheels 145–207µm in diameter (mean 175µm, standard deviation 20.24). Number of teeth on rim ranges from 96 to 126; Teeth increase in number as wheels increase in diameter.

Tentacle stalks and terminal branches contain flattened rods very variable in size, 100– 202µm in length, with slightly spinous ends and usually with slightly widened central region ( Figure 3 E). Rods usually straight, sometimes branched, varying in length, average length approximately 160µm.

Behavior: Chiridota heheva is active, moving about in its varied habitats. The tentacles appear to be in constant motion in the Central America videotapes, their cylindrical stalks extended, and their discoidal terminal pads, fringed with extended finger­like digits, waving slowly in the water. This species apparently feeds on a mixture of sediment, wood fragments when available, and suspended material, suggesting that the species may derive its nutriment from a variety of sources. Herdendorf (1995) described the feeding behavior of this species at the Central America shipwreck, noting that “Detritus on the timbers and organic matter in the sediment ooze were major food items. One at a time the tentacles were stuffed into the pharynx and the adhering food particles were wiped off as the tentacles were pulled out of the mouth. The animals were observed placing rather sizable particles (up to 1 mm) in their mouths, some of which were rejected and fell to the ocean floor” (P.122). The specimen from Alvin Dive 876 was apparently recovered from Dr. Ruth Turner’s wood blocks, for it had ingested numerous small wood fragments.

Reproduction: The mean egg diameter of 110µm is small when compared to some other deep­sea holothurians ( Billett, 1991), whose egg diameters tend to range upwards from approximately 200µm (ibid., p.287). Billett suggests that egg diameters in the range of 200–450 µm suggest that probably lecithotrophic larvae are involved. The type of larva in C. heheva is unknown, but the egg size points to the possibility of a planktotrophic larva ( Pearse, 1994). Further, the rapid colonization of Dr. Turner’s wood blocks ( Turner, 1977) by this holothurian suggests that its larval stages are demersal, at least for the later part of larval life. As apparently mature eggs were present in gonads of individuals collected in October 2000 and March 1984, it seems possible that this species can reproduce yearround.

Ecological notes: This new species is apparently common at cold seeps in the Western Atlantic. Paull et al. (1984) noted that “slender purple holothurians” (P.965) were “numerous” (P. 966) at the base of the Florida Escarpment in the eastern Gulf of Mexico. Here, sulfide rich hypersaline waters seep from the seabed at near ambient temperatures. In a more detailed discussion of the fauna of the Florida Escarpment, Hecker (1985) noted that that Chiridota sp. “appears to be an opportunist in that it colonizes ephemeral areas of nutrient enrichment”, for it had been found not only at the cold seeps, but also on Dr. Ruth Turner’s experimental deep­sea “wood islands” ( Turner, 1977; personal communication, D. Pawson to B. Hecker, 1984). Hecker’s suggestion was amply borne out by the discovery of this holothurian species at the wreck of the ship Central America ( Herdendorf et al, 1995), where it was videotaped and photographed on, and collected from, a variety of substrates, especially wood and soft sediments (see Herdendorf et al., 1995, Figures 47, 60).

At the Blake Ridge Diapir, Van Dover et al. (2003) found this holothurian in association with mussels ( Bathymodiolus heckerae ) in a community of animals associated with methane seeps. One figure (6e, reproduced here as Figure 2 B) shows a Chiridota heheva with its anterior and posterior extremities embedded among the mussels. Van Dover et al. (2003) noted that this holothurian was known from the Florida Escarpment (Turnipseed & Van Dover, unpublished), but not recorded from the Barbados seeps by Sibuet & Olu (1998). Carney (1994) did not find Chiridota at the chemosynthetic Gulf of Mexico sites that he explored.

In their review of cold seep biodiversity and biogeography, Sibuet & Olu (1998) note that of the 211 species then known from cold seeps, only one, the pogonophoran Lamellibrachia barhami , was common to cold seeps and shipwrecks. Chiridota heheva can now be added to this list, and Herdendorf et al. (1995) list at least six genera (sponge, Haliclona sp.; pogonophoran Sclerolinum sp.; cephalopod Benthoctopus sp.; barnacle Arcoscalpellum sp.; crustaceans Munida sp and Munidopsis sp.) from the Central America shipwreck that are also known from cold seep sites. The role of whale carcasses on the seabed as “islands” where chemosynthetic communities flourish, was discovered very recently ( Smith et al., 1998; Smith et al., 2003). Dead whales can apparently function as “stepping stones”, enabling the broad dispersal of certain chemosynthetic invertebrates to widely separated vents and seeps. The importance of anthropogenic substrates, such as wood blocks and the wooden wreckage of sunken vessels, as “stepping stones”, aiding in dispersal of cold seep animals, has yet to be accurately assessed for deep­sea invertebrates. The pioneering studies of Turner (1973, 1977, 1981) and Turner et al. (1985) need to be followed by further investigations in the western Atlantic using wood blocks at ecologically important sites, such as immediately to the north of the Blake Ridge seep sites, in the Straits of Florida, and off the west coast of Florida.

Distribution: Known from cold seeps on the Florida Escarpment in the eastern Gulf of Mexico; cold seeps at the Blake Ridge, east of Savannah, Georgia; wood blocks immediately south­east of Puerto Rico; the wreck of the ship Central America east of Savannah Georgia. Depth range 2,178–3,998 metres.

Etymology: The species name, heheva , is derived from the names of colleagues who kindly sent us material for study. The first syllable of the species name, “ he­”, is from Dr. Hecker. The second syllable, “ he ”, is from Dr. Herdendorf. The third syllable, “ va ”, is from Dr. Van Dover. Coincidentally, the Polynesian (Tahitian) word “ heheva ” refers to a dance. The slow and rhythmic movements of the feeding tentacles in this new species are strongly reminiscent of a Polynesian dancer’s hand movements.

Remarks: Chiridota heheva is similar in some respects to C. hydrothermica , described by Smirnov et al. (2000) from hydrothermal vents in West and Southeastern Pacific. It agrees with C. hydrothermica in the general characteristics of the wheel ossicles, in the morphology of the calcareous ring, and in the presence of numerous Polian vesicles. The two species differ consistently in color and, most importantly, in the structure of the tentacles. In life, C. heheva is purplish or bluish, and the dark color is preserved in alcohol in the substantial body wall; also, the wheel papillae are very conspicuous as white spots against this dark­colored background, in living and preserved material. In contrast, C. hydrothermica is “semi­transparent, grey­brownish.... The papillae are inconspicuous, their color is the same as the body” ( Smirnov et al., 2000, p.322).

Both species differ in the structure of the tentacles. The “ventral gap” between two ventral tentacles noted for C. hydrothermica does not exist in C. heheva . In C. heheva the digits are always distinct and conspicuous, while in C. hydrothermica the “tentacle processes are fused along their length, giving the tentacles a lobe­like shape with a wavy margin” ( Smirnov et al., 2000, p. 322).

Another abyssal species, Chiridota laevis (Fabricius) , is known from the North Atlantic and North Pacific ( Clark, 1908). It differs from C. heheva in color, being described as “pinkish, pinkish brown, greyish or yellowish ( Clark,1908), and in its preferred habitat. In addition, as is typical in most Chiridota species, the anterior projections of the radial pieces of the calcareous ring in C. laevis are perforated for passage of the radial nerve (see Figure 3 D).

In light of the unique structure of the calcareous ring and tentacles, it might be desirable to erect a new genus for C. hydrothermica and C. heheva . This should be considered only after a comprehensive review of all deep­sea species currently referred to the genus Chiridota .

Figures

FIGURE 1. Chiridota heheva new species. Approximately 4 individuals in situ near whitish bacterial mats (?) at Florida Escarpment seep site, eastern Gulf of Mexico, 3,270 meters. Alvin Dive 1343. Approximate diameter of body 5 mm. Photo, S. Golubic.

FIGURE 2. Chiridota heheva new species. A, At Bathymodiolus heckeri mussel beds, Blake Ridge, close­up view showing anterior end of body with white spots (wheel papillae), and extended tentacles. Note finger­like digits forming a fringe around tentacle terminal disc. Approximate diameter of tentacle stem 1 mm. From Van Dover et al., 2003, with permission. B, One individual at Bathymodiolus heckeri mussel beds, Blake Ridge, showing conspicuous white spots (wheel papillae) against bluish ground color of body wall. Approximate diameter of body 5 mm. Shrimp at right center is Alvinocaris sp. From Van Dover et al., 2003, with permission. C, At Central America wreck showing conspicuous white spots (wheel papillae) against bluish ground color of body wall. Image taken from videotape, Charles E. Herdendorf. Size of specimen unknown. D, At Central America wreck, showing extended feeding tentacles with conspicuous, discrete digits. Size of specimen unknown. Image taken from videotape, Charles E. Herdendorf. E, Oral field with 12 tentacles in a partially contracted state. Note absence of a “ ventral gap ” between tentacles. Long axis of mouth is 2 mm. F, Close­up view of contracted tentacles showing infolded digits. G, Partially contracted tentacle showing discrete digits. Approximate length of digits 1. 5 mm.

FIGURE 3. A – C, E – J, Chiridota heheva new species; D, Chiridota laevis (Fabricius). A, Left ventral radial piece from calcareous ring. Note absence of perforation for radial nerve. Length of piece 1. 9 mm. B, Right ventral interradial piece from calcareous ring; length of piece 1. 6 mm. C, Bipartite right dorsal radial piece from calcareous ring. Note absence of perforation for radial nerve. Length of piece 2. 7 mm. D, Chiridota laevis (Fabricius), bipartite right dorsal radial piece from calcareous ring. Note perforation for radial nerve. Length of piece mm. 1.6 mm. E, Rods from tentacles. Length of longest rod 177 µm. F, Inner surface of wheel from wheel papilla. Diameter of wheel 186 µm. G, Outer surface of wheel from wheel papilla. Diameter of wheel 154 µm. H, Three wheels from wheel papillae, two showing inner surface, one showing outer surface. Largest wheel abnormal in having teeth on margin of inner rim. Diameter of largest wheel 184 µm. I, Wheel in lateral view. Diameter of wheel 132 µm. J, Wheel in slightly oblique view. Diameter of wheel 190 µm.