Havelockia nietae Prata & Manso & Christoffersen 2020, sp. nov.

Havelockia nietae sp. nov.

(Table 2, Figures 18–19)

urn:lsid:zoobank.org:act: 8A615CA9-6A8A-4466-82ED-774C3DDFDA03

Type material. Holotype: 1 spec., Diogo Lopes, Maca, Rio Grande do Norte State, Brazil 0504’1.4”S; 3627’31.3”W (UFPB.ECH-2120).

Type locality. Diogo Lopes, Macaú, Rio Grande do Norte State, Brazil 05º04’1.4”S; 36º27’31.3”W, in the intertidal zone.

Etymology. The specific epithet nietae is used to honor the grandmother of JP, who always encouraged her to study and admire nature.

Diagnosis. Barrel-shaped body, slightly curved. Calcareous ring stout, up to 1/2 of total body length, radial and interradial plates united along entire length, radial two times smaller than interradial. Radial plates with posterior processes segmented in seven to nine pieces. Body wall ossicles consist of two-pillared tables of two kinds; the first type has oblong discs with four regular holes; the second table type has rectangular to irregular disc with about eight holes. Tube feet with supporting tables of elongated discs with four or more holes, formed by two or three pillars with two to four teeth in the apex, supporting plates and endplates. Introvert with rosettes, some large forming a second layer, and tables of elongated to irregular disc with four or more holes and two pillars, ending in four or more teeth. Tentacles with rounded to elongated rosettes and rods.

Description of holotype. Barrel-shaped body, slightly curved (Fig. 18A), 23 mm in length, 14 mm in breadth in mid-body. Slightly thickened skin, rough due the number of ossicles. Color in life brown, darker in the posterior end, introvert white with dark spots, tentacles whitish and tube feet light orange. Color light brown in alcohol. Mouth slightly upwards. Anus terminal, anal teeth not observed. Tentacles 10, bushy, the two most ventral ones reduced. Introvert large with thin tegument, without tube feet. Tube feet in double rows in the radii, with many tube feet scattered in the interradii, covering the body. Calcareous ring stout, up to 1/2 of total body length. Radial and interradial plates united along entire length, radial two times smaller than interradial. Radial plates notched anteriorly for the passage of the radial nerves and radial canal, with posterior processes segmented in seven to nine pieces (Fig. 18E); mid-ventral plate shorter than the others but with long posterior processes (Fig. 18G). Interradial plates arrow-shaped, with an anterior depression, without posterior processes (Fig. 18E); lateral interradial plates slightly askew (Fig. 18F); ventral interradial plates smaller the others (Fig. 18G). Madreporite rounded, stone canal elongated. Polian vesicle single, elongated. Retractor muscles thick. Longitudinal muscles well developed, not divided. Respiratory trees slightly branched, extending along the length of the body. Gonad in single tuft, tubules thin, unbranched, numerous, filling a large part of the cavity. Body wall ossicles consist of tables of two kinds. The first type has oblong disc of four regular holes, some with additional perforations (Figs. 19 F–G) (80–110 µm long). The second table type has irregular disc, with five to 15 holes. These tables can present square (80–90 µm long) (Fig. 19D), star-like (100–120 µm long), triangular (100 µm long) or elongated disc (75–110 µm long) (Fig. 19E). Both table types have two-pillared spire (60–80 µm high), which are united along the length, ending into two to four teeth (Fig. 19F). Tube feet include numerous supporting tables of elongated discs with four regular holes (80–150 µm long, 40–60 µm high), formed by two or three pillars ending into two to four teeth (Figs. 19J, L), irregular tables with bifurcated disc and five or more holes (90–150 µm long) (Fig. 19K), supporting plates (75–110 µm long) (Fig. 19H) and endplates (150 µm long) (Fig. 19I). Introvert includes rosettes with a second layer (80–120 µm long) (Figs. 18D, 19C), numerous small rounded rosettes (40–70 µm long) (Fig. 19A), and tables of elongated to irregular disc with four or more holes (100–115 µm long), with short spire, two-pillared, ending in a well-developed crown of teeth (Figs. 19 B–C). Tentacles with rosettes (Fig. 18B) (20–50 µm long), and rods, (20–40 µm long), some with holes in the ends (Fig. 18C).

Geographical distribution. The specimen was found only in Diogo Lopes, Macau, Rio Grande do Norte, Brazil. The species was collected in the intertidal zone.

Remarks. The species Havelockia nietae sp. nov. is referred to Havelockia Pearson, 1903 for sharing diagnostic characteristics of this group, as calcareous ring stout with radial and interradial plates united along the length, being free only in the anterior projections; posterior paired processes of radial plates divided in several pieces; body wall tables with square to oval disc perforated by four large central and four smaller peripheral holes, sometimes reduced or absent; and 2-pillared spire ending in few blunt teeth.

In comparison with other species of the genus, Havelockia nietae sp. nov. has two kinds of body wall tables, one with regular oval disc and another with irregular disc, that can be square, triangular, star-like or elongated; besides having supporting tables with spires formed by two to three pillars, some bigger and with bifurcated disc; large rosettes with a second layer in the introvert, and a long calcareous ring. These features in combination make the species distinct.

The other Havelockia species known from the Western Atlantic, Havelockia scabra (Verrill, 1873), differs from Havelockia nietae sp. nov. by the strongly curved body, body wall tables with seven or more holes, and spire ending in several teeth. H. scabra occurs in the North Atlantic, within the Gulf of Mexico. Havelockia mansoae differs from Havelockia nietae sp. nov. by the short calcareous ring and regular ossicles in the body wall. Havelockia oraneae differs from Havelockia nietae sp. nov. by the calcareous ring morphology, presence of reduced posterior processes in the interradial plates, regular shape of the ossicles in the body wall, and absence of rosettes in the tentacles. A comparison between Atlantic Havelockia species with Havelockia nietae sp. nov. is given in table 2.

The family Sclerodactylidae is represented in the South-western Atlantic Ocean by the species Pseudothyone belli (Ludwig, 1887), Coronatum baiensis Martins & Souto 2012, Thandarum hernandezi Martinez & Brogger, 2012, Havelockia pegi Martinez, 2013, Havelockia mansoae Martins & Tavares, 2018 and Havelockia oraneae Martins & Souto, 2018.

Coronatum baiensis, have tables with an oval, knobbed disc, while the tables of Havelockia nietae sp. nov. are smooth and irregular in shape; and Pseudothyone belli has knobbed buttons instead of tables in the body wall. Havelockia nietae sp. nov. could be confused with species of the genus Thyone due the shape of the tables spire, but Thyone species are well characterized by a different type of calcareous ring, with broken radial and interradial plates. Havelockia nietae sp. nov. differs further from Thandarum hernandezi by the shape of the calcareous ring, the form of the ossicles from the introvert, and by the presence of tables four-pillared.

The external appearance of the specimen is similar to species of Parathyone, due to the barrel-shaped body and arrangement of the tube feet, but in this genus there are only cups and plates in the body wall, tables as in Havelockia nietae sp. nov. are absent.

Ecological note. The specimen was found buried in a soft substrate of sand, having the tentacles oriented to the surface in a mangrove hyper-saline area.