Havelockia Pearson, 1903

Martinez, Mariano I., Thandar, Ahmed S. & Penchaszadeh, Pablo E., 2013, A new species of Havelockia Pearson, 1903 from the Argentine Sea (Holothuroidea: Dendrochirotida: Sclerodactylidae), Zootaxa 3609 (6), pp. 583-588 : 584-587

Genus Havelockia Pearson, 1903

Diagnosis (after Thandar, 1989: 292)

Calcareous ring short, stout, only anterior projections of radial and interradial plates free; posterior paired processes of radial plates divided into several pieces. Body wall ossicles tables with a squarish to oval disc usually perforated by four large central and four smaller peripheral holes, the latter sometimes reduced or absent; spire of two pillars joined at apex and terminating in few blunt teeth.

Type species: Havelockia herdmani Pearson, 1903 (by original designation).

Havelockia pegi sp. nov. ( Figures 1–3 )

Diagnosis. Tentacles purple in colour; body wall ossicles scarce, only few detected, especially from the anal region and base of tube feet, comprising tables with a 2-pillared, often regressed spire; tentacles and introvert with rosettes.

Etymology. The specific name pegi is used to honour the Martinez-Ferreyra family to whom this name is quite significant. It is a noun in apposition.

Material examined. Holotype: 86 mm length, one male individual and 3 slides with ossicles, Villarino, Golfo San José, Chubut Province (Sep. 2006), (42°25’S – 64°31’W), 10 m. MACN-In 39019. Paratypes: 32,70 mm, 55,95 mm, Buenos Aires Province (9 Sep. 2009), (38°15’S – 57°15’W), 48 m., MACN-In 39021 (2 paratypes); 35,55 mm, Villarino, Golfo San José, Chubut Province (42°25’S – 64°31’W), 10m, MACN-In 39020 (1 paratype); 30,43 mm length, one individual and 1 slide with ossicles; El sótano, Golfo San Matías, Río Negro Province, Argentina (Nov.

2011), (41º00’ S – 65º08’ W), 15 m, ICML-UNAM 5.195.0 (1 paratype); 40 mm, one individual; San Matías, Río Negro Province (16 Nov. 2009), (41º 20’S – 62º 59’W), 34 m, CNP-INV 415 (1 paratype).

Description. All specimens partially eviscerated; length up to 86 mm. Body form U-shaped to cylindrical. Colour in life and in alcohol, brown; tentacles purple in life, turning to light violet or brown in alcohol. Tube feet scattered, covering entire body with no indication of any regular arrangement ( Fig. 1 ). Larger tube feet around 2 mm in length, suckers well developed. Tentacles 10, bushy, ventral two reduced to quarter the size of large tentacles. Anal teeth present. Calcareous ring short-tubular with plates compact, fused for most of their length; posterior paired processes of radial plates of moderate length, divided into 3–4 pieces of calcite. Polian vesicle single, saccular, free, on left side of mesentery; stone canal long, straight, on right side of mesentery, madreporite lenticular. Gonad of holotype mature, in two tufts, attached to the middle of body, each with numerous undivided branches, filling greater part of coelom. Respiratory trees, each with two branches, extending along the total length of body, the right tree slightly longer. Longitudinal muscle bands well developed. Retractor muscles attach to the radial plates. Cloaca elongate, about quarter to one fifth the total length of body.

Body wall ossicles rare, only a few detected, especially in the anal region and bases of tube feet, comprising tables with an oblong or irregular, often regressive disc (65–160 µm) with 4–8 holes and a low, 2-pillared spire, pillars sometimes fused ( Fig. 2 a, 3a). Tube feet ossicles as tables with a quadrilocular, straight or slightly curved disc (115–172 µm), with four central holes and often an additional hole at each end; spire 2-pillared, ending in several blunt teeth or spire regressive or absent ( Fig. 2 b, 3b), end-plate circular, ca. 225 µm, with small central holes and larger ones outside these in no regular arrangement ( Fig. 2 c). Introvert and tentacles with closed rosettes, 30–62 µm ( Fig. 2 d).

Habitat: sand, broken shells and gravel.

Distribution: South Atlantic Ocean, from Buenos Aires Province, Mar del Plata (38°15’S – 57°15’W) to Chubut Province, Villarino (42°25’S – 64°31’W)

Depth: 10– 48 m.

Remarks. In all individuals examined, the tentacles, calcareous ring and the first part of the gut are partially eviscerated. The dark purple colour of the tentacles, in living, and brown or light-violet in preserved specimens, is quite distinctive in comparison with that of some other Argentinian dendrochirotids.

The family Sclerodactylidae (sensu Pawson & Fell 1965) comprises over 80 species with a world-wide distribution, but it is surprising that besides Pseudothyone belli (Ludwig, 1887) and the recently described Coronatum baiensis Martins & Souto, 2012 , no other true sclerodactylid has been recorded from the south-western Atlantic Ocean so far. In comparison with most species of the genus, Havelockia pegi sp. nov. has scarce body wall ossicles, a circular end-plate, and rosettes in both the introvert and tentacles. These features in combination make it distinctive. There are only a couple of Havelockia species with scarce or no body wall deposits. These are H. discolor (Sluiter, 1901) with no body wall deposits and H. conciliatrix (Sluiter, 1901) with scarce deposits, restricted to the podia. Both are warm-water West Pacific species and differ from the new species in many features, e.g. H. conciliatrix has conical papillae and naked dorsal interradii and H. discolor has rods in the tentacles and no deposits in the body wall and tube feet. In comparison with the other sclerodactylids (sensu Panning, 1949, non Pawson & Fell, 1965) from South America, C. baiensis has tables with oval, knobbed disc while Pseudothyone belli has knobbed buttons instead of tables in the body wall.

The new species might be mistaken to represent a Pentamera , notably P. chiloensis , which also occurs in Argentinian waters. However, the genus Pentamera is well characterized by the ambulacral restriction of the tube feet, a different type of calcareous ring and well developed body wall ossicles, often accompanied by plates. P. chiloensis in particular, although lacking plate-like ossicles, has well-developed table deposits with numerous holes, table spires with 1–4 pillars and stellate end-plates (Pawson 1969). Thandarum hernandezi differs from H. pegi in the ambulacral restriction of the tube feet and the presence of 4-pillared tables in the body wall. However, both species have a northern distribution, but restricted to the Rio de la Plata and are not found further north as the low salinity prevent their influx into the northern waters. Perhaps the same factor intervenes to prevent Brazilian species extending southwards (Tommasi et al. 1988b, Martinez & Brogger 2012).

More collections along the long Argentinian coastline will undoubtedly reveal more dendrochirotids as this order is notorious for its distribution in temperate waters of all the world’s oceans. In fact, the temperate waters of most continents or subcontinents of the southern hemisphere, including New Zealand, are well endowed with endemic dendrochirotids—so Argentina may not be an exception.

Figures

FIGURE 2. Ossicles of Havelockia pegi sp. nov. A. Tables from body wall; B. Quadrilocular tables from tube feet; C. endplate; D. Rosettes from introvert and tentacles. Scale 50 µm.

FIGURE 1. A. Holotype of Havelockia pegi sp. nov., MACN-In 39019, scale 2 cm; B. Calcareous ring.

FIGURE 3. A. table from body wall near anus; B. Quadrilocular table from tube foot. Scale 20 µm.