1 specimen, South Africa, KwaZulu-Natal, St Lucia beach, 7 October 2010, SJ Bownes legit.

TL, 319 µm; PhL, 92 µm; PhIJ at U26; TbA, 4 per side; TbL, 1+1+1+2 per side; TbP, 5 per side; Ocellar granules absent.

the single specimen found is a young adult at the male phase. Among the nine species of Dactylopodola described so far (Hummon and Todaro 2010), the body shape of the specimen from South Africa most resembles Dactylopodola australiensis Hochberg, 2003, Dactylopodola indica (Rao & Ganapati, 1968), Dactylopodola mesotyphle Hummon, Todaro, Tongiorgi & Balsamo, 1998 and Dactylopodola typhle (Remane, 1927). By virtue of its body size (considering the age), number and arrangement of the adhesive tubes our specimen best approaches the morphometric traits of Dactylopodola indica and, especially, of Dactylopodola australiensis. While Dactylopodola indica is reported (Rao and Ganapati 1968) to have only 2 TbA and 4 TbP per side (vs 4 and 5, respectively), Dactylopodola australiensis seems to differ from the South African specimen solely in the length of the pharynx (131 vs 92 µm) and in the position of the pharyngeo-intestinal junction (U34-U35 vs U26) (see Hochberg 2003); it is possible that dissimilarities are due to the early age of the African specimen.

1 juvenile specimen, South Africa, KwaZulu-Natal, St Lucia beach, 22 February 2010, NAF Miranda legit.

TL, 208.6 µm; PhL, 92 µm; PhIJ at U26; oral palps, 36.4 µm in length, showing 5 dorsal and 6 ventral papillae; cuticular covering made up of relatively large tetrancres; TbA, 3 per side; TbL, 5 per side; TbP, 4 per side, 3 at the end of the caudal pedicle and 1 near its base (inner side).

The anatomical traits of the animal from South Africa do not seem to match those of any other known species of Pseudostomella.However, specimen was a juvenile (i.e., not reproductively mature) and so could not be fully described. Should an adult be found in the future, useful comparisons could be restricted to species bearing a cuticular covering made up of tetrancres and relatively long caudal pedicles.

South Africa, KwaZulu-Natal, St. Lucia beach (28°23'S; 32°25'E); among medium, moderately siliceous grains on a high-energy sandy beach at mid-tide level.

Holotype, the 146.5 μm long adult specimen shown in Figure 3.

Four specimens, two adults (including the holotype) plus one subadult collected on 22 February 2010 (NAF Miranda legit) and 1 adult collected on 7 October 2010 (SJ Bownes legit)

Medium-sized Halichaetonotus (LT to 146.6 μm), head, neck and trunk well defined; head rounded, lacking hypostomion but with a small cephalion; medium-long furca projecting from the posterior of the trunk. Body enveloped by 15 columns (7 dorsal, 2 lateral + 2 ventrolateral hydrofoil scales, 2+2 ventral small scales) of alternating keeled scales each with 17–19 scales. Scales, round on head and neck becoming oval to semi-elliptical on the trunk; in general, keel extending beyond the edge of the scales as short spiny processes; on three posterior scales, one median and two lateral, keels forming long and robust spines extending beyond end of trunk. Two small spiny scales on dorsal and several keeled scales on ventral base of furca. Laterally and ventrolaterally, 2+2 columns of hydrofoil scales of varying length; ventrally, 2+2 additional columns of smaller scales; locomotory cilia arranged in two longitudinal bands, interciliary ventral field naked except for two pairs of perianal ovoid keeled/spiny scales. Almost circular mouth opening into cylindrical pharynx with 2 teeth, then sack-like intestine and terminal ventral anus. All specimens parthenogenetic, sometimes with single large egg in position dorsal to mid intestine.

The specific name alludes to the geographic locality where the new species has been found.

The description is mainly based on an adult specimen, 146.5 μm in total length. Head rounded, slightly elongated along anterior/posterior axis, bearing a shallow cephalion but no pleural lobes or visible hypostomion; neck narrower than head, trunk sac-like, terminating in a furcate caudum. Body widths at the head/neck/trunk/caudum are 31/22.5/34.5/22 μm, at U11/27/58/81, respectively. Caudum of medium length (26.6 μm), paired laterally divergent adhesive tubes (20 μm in length) with a slightly swollen base (6.5 μm), covered by scales.

Cuticular armature. Head, neck, and trunk covered dorsally and lateroventrally by alternating columns (7 dorsal, 1+1 lateral and 1+1 ventrolateral hydrofoil, 2+2 ventral) of 17–19 keeled scales, barely overlapping. On dorsal side, head and neck scales are round (3–5 μm in diameter), while trunk scales are oval to semi-elliptical (9.5 × 5.5 - 12.7 × 6.6 μm). In general, keel on dorsal scales extends beyond the edge of scales as short spiny process; however, on two lateral and one median trunk scales, at U63 and U71, respectively, keels form robust, very long spines projecting 26 μm beyond scales. On posterior trunk region are two oval, double keeled scales (5 × 4 μm) each anchoring a sensorial bristle at U79.5 and a couple of oval spiny scales (4 × 3.5 μm) bearing spines (4–5 μm long) protruding into the furcal indentation. Lateral and ventrolateral spines of hydrofoil scales bearing flattened lamellae, most of which taper into a long hairy process; lamellae bearing spines of the lateral scales are longer than related ventrolateral ones (up to 25 vs up to 19), while lamellae of a column are longest at mid trunk. On ventral side, up to five keeled scales, 3–4 μm long, cover the fleshy portion of each furcal branch; the interciliary field appears naked except for two pairs of oval keeled scales in the perianal region; scales of anterior pair are larger (9.5 × 4.5 μm) than posterior ones (6.0 × 3.5 μm).

Ventral ciliation. paired longitudinal bands extending from U03 to approximately U77; each broadly club-shaped anteriorly, but narrowing considerably from the posterior pharyngeal region; bands approach each other immediately behind the mouth, but remain separate throughout their entire length; individual cilia are about 11 μm in length.

Digestive tract:Mouth of medium size (ca.6 μm in diameter), projecting very slightly ventrally and leading progressively into a 32 μm long pharynx; pharynx muscular, roughly cylindrical (8 μm in diameter), showing a bulb anteriorly (12 μm in diameter); two cuticular teeth are visible within the bulb; pharynx connected to sack-like intestine at pharyngeo-intestinal junction at U25; intestine straight, narrowing posteriorly, anus ventral at U77.

Reproductive tract. Three specimens were in parthenogenic phase, two of which with a large egg filling much of the trunk.

Highly variable cuticular armature distinguishes the 30 species of Halichaetonotus described so far (Hummon and Todaro 2010, Hummon 2010). The new species most closely resembles Halichaetonotus marivagus, Balsamo, Todaro & Tongiorgi, 1992, and Halichaetonotus australis Nichols & Todaro, 2005, in that all three species are characterised by three dorsal spines close to the posterior end of the trunk. Spines are longest in Halichaetonotus australis (up to 46 µm), intermediate in Halichaetonotus sanctaeluciae sp. n. (up to 26 µm) and shortest in Halichaetonotus marivagus (up to 15 µm).

Halichaetonotus marivagus known from the Mediterranean, can easily be distinguished from the new species also on the basis of its wide hypostomion, which is absent in Halichaetonotus sanctaeluciae sp. n., and for exhibiting a large cephalion that covers much of the dorsal side of its head (Balsamo et al. 1992).

Halichaetonotus australis described from the east coast of Australia, is unique in that the large median dorsal spine precedes the lateral ones (the opposite is true for Halichaetonotus sanctaeluciae sp. n.). Moreover, the keel of the dorsal scales does not extend beyond the edge of the scales (Nicholas and Todaro 2005), whereas in Halichaetonotus santaeluciae sp. n. keels form a spiny process.

The new species also resembles Halichaetonotus aculifer (Gerlach, 1953) in terms of size and, most importantly, the shape of the hydrofoil scales. However, the presence of three long spines on the posterior trunk and the absence of ventral interciliary field scales in Halichaetonotus sanctaeluciae sp. n. are features that can easily differentiate this species from Halichaetonotus aculifer (see Gerlach 1953).

1 adult specimen, South Africa, KwaZulu-Natal, St Lucia beach, 22 February 2010, NAF Miranda legit.

TL, 106.2 µm; PhL, 27.2 µm; PhIJ at U29.5; FuL, 21 (adhesive tube 17 µm); dorsal cuticular covering made up of seven columns of 17 overlapping, keeled scales. Scales round (up to 4 µm in diameter) on the head and neck region becoming ovoid (up to 8 × 4) over trunk. With exception of medial one, scales of posterior-most row bear keel extending into a 14 µm- long spine; 1+1 columns of hydrofoil scales ventrolaterally.

by virtue of the six spiny scales on the trunk rear, the animal appears different from any other species described so far. Unfortunately, a break of the slide occurred during the observation prevented the examination of the ventral side. Without detailed observations of the ventral scales’ shape, size and arrangement, we choose to avoid making a formal description of the species until additional specimens are observed.

2 adult specimens and 2 juveniles, South Africa, KwaZulu-Natal, St Lucia beach, 22 February 2010, NAF Miranda legit.

TL, up to 104 µm; PhL, up to 25 µm; PhIJ at U29; FuL, up to 17.5 (adhesive tube 13 µm); dorsal cuticular covering made up of nine columns of 17 slightly overlapping, keeled scales. Scales round (up to 2–3 µm in diameter) on head and neck region becoming elliptical (up to 5 × 2 µm) over trunk. Ventrolaterally, 1+1 columns of hydrofoil scales bearing large lamellae.

Morphometry and general appearance of the specimens found at St Lucia match the metric and meristic characteristics of the cosmopolitan Halichaetonotus decipiens (Remane, 1929). Unfortunately, the detritus attached to the ventral side of one of the two adults and the large egg inside the second, prevented the observation of the cuticular details on the ventral side. Consequently, that identification to species cannot be made without reasonable doubts.

1 adult specimen, South Africa, KwaZulu-Natal, St Lucia beach, 22 February 2010, NAF Miranda legit.

TL, 179 µm; PhL, 41.5 µm; PhIJ at U25.6; FuL, 52.3 µm (adhesive tube 20.5 µm); Dorsal cuticular covering made up of seven columns of 43–45 overlapping, scales extending laterally as hydrofoil scales. Ten flat scales on the inner margin of each furcal branch. Two pairs of head sensory cirri, 17–28 µm in length, 1 pair of head tentacles, 11.5 µm in length.

morphometry and general appearance of the specimen from St. Lucia is in general accordance with data reported for the cosmopolitan Halichaetonotus squamosa; in particular, the South African specimen appears of a size intermediate between individuals of the Mediterranean populations described by Wilke (1954) and Luporini et al. (1973) and specimens described from the Atlantic coast of France by Ruppert (1979).

1 adult specimen. South Africa, KwaZulu-Natal, St Lucia beach, 22 February 2010, NAF Miranda legit.

TL, 196 µm; PhL, 49.5 µm; PhIJ at U29; FuL, 27 µm (adhesive tube 10.2 µm); dorsal cuticular covering made up of 15 columns of 48 pedunculated scales (median column).

Morphometry and general appearance of the specimens found at St Lucia fall within the taxonomic range of the cosmopolitan Xenotrichula intermedia Remane, 1934 and of an as yet unnamed Xenotrichula sp. from Kuwait. The latter two species are siblings, sharing almost identical external morphology but very different organization of the muscular system (see Leasi and Todaro 2009). Technical reasons (several specimens are necessary) prevented the use of confocal laser scanning microscopy to study the organization of the muscular system in the only specimen available. Consequently, identification of the animal found at St. Lucia could not be made with sufficient confidence.