Phyrella mookiei, Michonneau & Paulay, 2014

Michonneau, François & Paulay, Gustav, 2014, Revision of the genus Phyrella (Holothuroidea: Dendrochirotida) with the description of a new species from Guam, Zootaxa 3760 (2), pp. 101-140 : 118-124

Phyrella mookiei sp. nov.

Figures 10–16 ; 27 h

http://zoobank.org/ D3E02B0E-308A-4C67-A143-05DB64692E75

Material examined. Holotype: UF 10336 , Guam, North end of Tumon Bay, Gun Beach, reef flat 0–1 m, 12 June 2010, coll. Nathaniel Evans, François Michonneau, Gustav Paulay, Arthur Anker. Paratypes: UF 4770 , Guam, Pago Bay outer reef flat, 0–1 m, May 2003, coll. Gustav Paulay ; UF 11539 , Guam, Piti Power plant intake tunnel under road, 2 m, 17 September 2011, coll. David Burdick.

Description. External morphology. Body wall soft, fairly thin, densely covered with tube feet. Beige (UF 4770, UF 11539) to off-white (UF 10336), with well-defined burgundy (UF 4770, UF 10336) to dark brown (UF 11539) spots either restricted to venter (UF 4770) or across entire body (UF 10336, UF 11539); area around introvert and cloaca with diffuse burgundy coloration in UF 10336 ( Fig. 11A ). Coloration in preservative similar to live after 3 years. Oral disc marbled with burgundy and white ( Fig. 10 , Fig. 11B ). Tentacles dendritic with longstalk, with small dark spots at their extremities ( Fig. 10 , Fig. 11B ). Body relatively straight when fully relaxed, contracting to U-shaped. Holotype 60 mm long along dorsum, 64 mm along venter and 18 mm wide; UF 4770, more contracted, 40 mm long along dorsum, 57 mm long along venter, and 23 mm wide; UF 11539 very contracted, 37 mm long along dorsum, 45 mm long along venter, and 16 mm wide. Introvert retracted in all specimens, 4 mm (UF 10336), 6 mm (UF 4770), and 12 mm (UF 11539) long. Tube feet abundant, evenly dispersed across radial and inter-radial areas, slightly denser ventrally, generally same color as body wall near base, lightening distally. Eighteen tentacles (10 on outer circle, 8 on inner circle) in UF 4770, ~17 tentacles in holotype based on live pictures (introvert retracted and not dissected). Cloacal membrane white; surrounded by 5 calcified anal teeth.

Internal anatomy (UF 4770, UF 11539). Polian vesicle single, white, 5–7 mm long. Stone canal short (2 mm), partially embedded in membrane surrounding calcareous ring. Madreporite free, small (<1 mm), spherical. Gonads well developed in both dissected specimens, both tufts extending almost entire length of animal; gonadal tubules unbranched to dichotomously branched 1–3 times; white with minute burgundy spots (similar color to body wall), with spots more common proximally and distally (UF 4770); in UF 10336, oocytes are clearly discernible, white, aligned in a row, encased in the thin, translucent gonadal tube wall, with abundant, minute, burgundy spots. Both dissected specimens have eviscerated, retaining gonads, anterior fragment of esophagus, cloaca and both respiratory trees. Intestine (retained separately for UF 4770) distended where filled with fine sand and other debris. Respiratory trees white with minute burgundy spots that are much less abundant in UF 4770 than in UF 11549, both branches extending almost entire length of animal.

Calcareous ring. Calcareous ring embedded in a fairly thin membrane, with highly fragmented radial and inter-radial elements ( Fig. 27h ). Anterior margins of radial plates unequally divided by well-formed notches. Anterior margins of inter-radial plates arrow-head shaped, more pointed and elongated in UF 4770 than UF 10336. Radial and inter-radial elements closely associated along most of their length. Inter-radials each composed of 5–12 elements. Radials each composed of 14–16 elements. Radials form posteriorly tails that curve to point anteriorly.

Ossicle assemblage. Dorsal and ventral body wall with similar ossicle complements of tables and rosettes ( Fig. 12A ), latter more abundant dorsally than ventrally. Tables of variable forms; disc 70–125 µ m in diameter, with 10–25 µ m diameter central perforation, and 4–15 (8 in the most symmetrical tables) holes arranged in a ring ( Fig. 13d ) or dispersed more irregularly in more highly perforated discs ( Fig. 13f ), disc margin smooth ( Fig. 13e ) to undulating ( Fig. 13f ), to partially ( Fig. 13a , Fig. 14m ) or completely serrated, barely raised; spire absent ( Fig. 13g –h ), to partially ( Fig. 14a–e ) or well developed ( Fig. 13a ), when complete, formed by four pillars connected by a single cross-beam half way along spire; crown variable in diameter when present, forming a spiny ring when well developed ( Fig. 13a,c ). Podia with perforated plates, 130–185 µ m long, 70–100 µ m wide; wider and not as elongated as in P. fragilis or P. thyonoides ; with large holes in center and smaller toward periphery; with large well-defined serrations, along at least part of the more convex margin ( Fig. 13l–o ; Fig. 14f–i, o–p ). Cloacal body wall with tables and abundant rosettes. Tables of variable form ranging from similar to body wall tables ( Fig. 15g ), to others that show a much greater number of disc perforations ( Fig. 15k ); disc 75–85 µ m in diameter, rim typically more serrated in tables of cloacal region than elsewhere in body wall; spire absent ( Fig. 15e ), incomplete ( Fig. 15m ), or complete, ending in a crown with teeth or lateral projections ( Fig. 15k ). Podia near cloaca with abundant rosettes ( Fig. 12C ) and perforated plates; latter smaller (80–100 µ m long) and often narrower (40–60 µ m wide) than those elsewhere in body wall ( Fig. 15c,d ), some with unusual lateral extensions ( Fig. 15a ). Podia that flank anal teeth with rods and abundant rosettes; rods often with marked curvature; ends with 2–6 holes and sometimes small spines ( Fig. 16a–d ). Introvert with similar ossicle assemblage to cloacal region; with tables and abundant rosettes. Tables 95–105 µ m in diameter. Podia with abundant rosettes, and perforated plates. Perforated plates variable, ranging from similar to those from the body wall ( Fig. 14u–v, x ), to much smaller (80 µ m long), almost circular, with small perforations ( Fig. 14w,y ). Tentacles with rods, 50–65 µ m long, with one or no perforation at ends ( Fig. 15n ). No ossicles observed in cloacal, longitudinal and retractor muscles; cloaca; intestine; gonads; and respiratory tree.

Etymology. Named after Mookie, the dog of our collection assistant Ms. Mandy Bemis, because the “woolly” appearance and color of this species is similar to the soft coat of wheaten terriers, the breed to which Mookie belongs.

Remarks. Phyrella mookiei resembles P. fragilis externally, but the ossicle assemblage and color pattern distinguish the two. In P. mookiei , holes in the disc of the tables are smaller, the margins of the disc are often at least partially serrated, the crowns are often more complete and wider; the perforated plates of the podia are shorter and wider; and the irregular tables in cloacal region have many holes in their rim. Rosettes occur throughout the body wall in P. mookiei but are restricted to introvert and near-cloacal body wall in other Phyrella . While both species have a beige-tan base color, the well-defined dark spotting distinguishes P. mookiei .

Ecology & distribution. The specimens were found in shallow waters (<2 m), under rocks, in coarse coralline sediments in areas of high flow. Phyrella mookiei is currently only known from Guam, where it is fairly rare.

Figures

FIGURE 10. Phyrella mookiei in situ, Guam. The animal is buried in sediment; the oral disc with extended tentacles is visible. Oral disc diameter approximately 1 cm in diameter. Photograph by David Burdick.

FIGURE 11. Live appearance of Phyrella mookiei UF 10336 (Holotype). A: Dorsal view, about 65 mm long; B: close-up view of oral region.

FIGURE 12. Rosettes of Phyrella mookiei. A: UF 10336 (Holotype), mid-dorsal body wall; B: UF 4770 (Paratype), introvert; C: UF 4770 (Paratype), cloacal region. Scale bar, 20 µm.

FIGURE 13. Ossicle assemblage of Phyrella mookiei UF 10336 (Holotype). a–k: tables (a–h) and perforated plates (i–k) from mid-dorsal body wall; l–o: perforated plates (l–n) and tube foot end plate (o) from ventral body wall.

FIGURE 14. Ossicle assemblage of Phyrella mookiei UF 4770 (Paratype). a–i: tables (a–e) and perforated plates (f–i) from mid-dorsal body wall; j–p: tables (j–n) and perforated plates (o–p) from mid-ventral body wall; q–z: tables (q–t) and perforated plates (u–z) from introvert.

FIGURE 15. Ossicle assemblage of Phyrella mookiei UF 4770 (Paratype). a–m: perforated plates (a–e) and tables (f–m) from cloacal region; n: rods from tentacles.

FIGURE 16. Ossicle assemblage of Phyrella mookiei UF 11359 (Paratype). a–d: rods in podia that flank anal teeth.

FIGURE 27. Calcareous rings. a–c: Phyrella fragilis (a: UF 4096, b: WAM Z26012, c: WAM Z26013); d–e: Phyrella trapeza, syntypes (d: MCZ HOL1488, thick body wall; e: MCZ HOL1488, thin body wall); f: Phyrella thyonoides, holotype (MCZ HOL1654); g: Phyrella cf. thyonoides (UF 9601); h: Phyrella mookiei, paratype (UF 4770); i: Phyllophorus aculeatus, holotype (USNM 1871).