3.1. Condyloderesagnetis sp. nov.

http://zoobank.org/8D20EDE4-FD6E-4251-AF4F-539F88DC1831.

(Figs. 2 - 7; Figs. S1 and S 2; Tables 1 - 3; Tables S1, S2).

Condyloderes sp. — Dal Zotto et al. (2008).

Condyloderes sp. 1 — Dal Zotto & Todaro (2016), Dal Zotto et al. (2016).

3.1.1. Diagnosis

Condyloderes with two lateral rows of condyles in broader placids, two apical and three basal condyles in midventral placid, two basal and two apical condyles in remaining broader placids; longitudinal rows of cuticular hairs regularly arranged on trunk segments 1 - 9; acicular spines in lateralaccessory position on segment 1; cuspidate spines in lateral accessory position on segment 2; subdorsal cuspidate spines on segment 3; ventrolateral slightly displaced ventromedially cuspidate spines on segment 5; pairs of paradorsal and sublateral cuspidate spines on segment 7; ventrolateral cuspidate spines on segment 8; lateral accessory cuspidate spines on segment 9; thick and short lateroventral acicular spines on segment 10 in females; ventromedial appendages on segments 6 - 8 in females; laterodorsal acicular spines on segment 10 in males.

3.1.2. Examined material

Holotype: female, mounted as glycerol-paraffin slide on a Cobb aluminium frame, ZMB 11763. Paratypes: 14 females and 31 males, mounted as glycerol-paraffin slide on a Cobb aluminium frame. Additional non-type material consists of five females and 12 males, also mounted for light microscopy or on SEM stubs. Catalogue numbers for types and non-types: ZMB 11764 to 11825. One male non-type mounted for light microscopy, USNM 1484169. Information on localities of the type and non-type material is reported in Table 1.

3.1.3. Type locality

Mediterranean Sea, southern Tyrrhenian Sea, Sicily, Gulf of Castellammare, off Castellamare del Golfo, 38 Ǫ 02 Į 59.80 ĮĮ N, 012 Ǫ 52 Į 44.91 ĮĮ E, 43 m depth, silt to very fine sand.

3.1.4. Etymology

The species is named after the first daughter of the first author, Agnese, and follows the Latinized wording Agnes and its genitive Agnetis .

3.1.5. Description

The description refers to females. See chapter “3.1.6. Sexual dimorphism” for male characters which are different from female ones. Figures and tables show both male and female characters (see figure and table legends). Adult specimens consist of head, neck, and 11 trunk segments (Figs. 2, 3A—B, 4A, 6A, Band 7A; Figs. S1A and B). See Table 2 for a summary of spine and sensory spot positions, and Table 3 for measurements and dimensions.

Head. The head is made up of a retractable mouth cone and an introvert (Figs. 4E, 5 and 6C - E; Figs. S1A and B). The pharyngeal crown consists of 10 lobular extensions at the anterior end of the pharynx and becomes visible in specimens with extremely protruded mouth cone (Fig. 6D). The mouth cone is characterized by the presence of a mouth cone weir (Fig. 6E). At least two rings with five inner oral styles in each were detected (rings —02 and —01; Fig. 6D, E). Ring 00 is characterized by nine thin outer oral styles, consisting of a single element with a thin distal part (Fig. 6E). The introvert has six rings of scalids and one ring of trichoscalids. Ring 01 bears 10 primary spinoscalids consisting of a sheath-like basis and an elongated distal part. The number of visible scalids in ring 06 is 14, no ring 06 scalids were observed in sectors 5 and 7 (Fig. 5). The posterior part of the introvert is characterized by 14 elongated and fringed trichoscalids. Apair of filamentous appendages is attached anteriorly to each trichoscalid. These structures are thinner than the scalids and do not show external sculpturing (Fig. 6C).

Neck. The neck consists of 16 placids, having irregular, knobby surfaces (condyles), varying in number between narrower and broader placids (Figs. 3C, 4F, 6F and 7B). Abroader midventral placid is neighboured by two narrower placids, and from thereon a broader and a narrower placid alternate. The midventral placid shows two condyles in the apical lateral row and three condyles in the basal lateral row. The remaining broader placids have two basal and two apical condyles. The narrower placids have one condyle in the basal lateral row, which splits apically into two condyles, whereas the paraventral narrower placids reveal only a single condyle (TableS2).

Trunk. The trunk is divided into 11 segments. It appears triangular in cross-section, with the tergosternal junctions located along the lateroventral angles.

Segment 1 is formed by a closed cuticular ring and shows a deep broad and squared midventral indentation at the posterior edge, because the free flap is missing (Figs. 2A and 7B). This segment is characterized by the presence of a middorsal hirsute spine and two acicular spines placed in lateral accessory position (Figs. 4B and 7A; Fig. S1C). The middorsal spine from this segment through segment 10 is located posteriorly on its segment and originates from a sclerotized anterior keel on a trunk segment; the free flap is missing where a spine inserts (Fig. 3D). Minute cuticular hairs are located along the anterior part of the segment. Paired sensory spots are located anteriorly in subdorsal, laterodorsal, midlateral, sublateral, and ventromedial position. These sensoryspots are type-6, hence consisting of a structure emerging from the cuticle and giving the impression of being half-drowned in it (Fig. 6H). In rare cases a cilium, ca. 2 M m long, juts outof the central pore of this sensory spot (Fig. 6G). Similarly to the following segments, the posterior margin of the segment is straight, and shows a free flap overlapping the subsequent segment and terminating in a primary pectinate fringe (Fig. 4D). The free flap is interrupted where the spines originate and ventrolaterally to midventrally. This condition is repeated through segments 2 to 11 except for the ventral lack of the free flap, even if the teeth of the primary pectinate fringe are shorter and smaller on segment 10 and, particularly, on segment 11 (Figs. 6I and 7B - C, F—G). Elongated cuticular hairs (Figs. 6J and 7H) are arranged in longitudinal rows of one to three each originating from the middle part of the segment and continuing beyond the segment's posterior edge (Figs. 6C and 7B). Within each row the hairs are arranged one after the other from anterior to posterior. The rows are approximately 16 on the ventral side and 40 on the dorsal side, and are absent midventrally and paraventrally, and partially in a midlateral position. Other irregularly arranged cuticular hairs are present midventrally and ventrolaterally from anterior to posterior.

Segment 2 consists of a tergal and two sternal plates (Figs. 3D and 7A). The same condition is repeated through segments 3 to 10. This segment bears a middorsal spine, two lateroventral acicular spines, and two cuspidate spines in lateral accessory position next to the edge of the sublateral position (Figs. 4B and 7A, B, C; Fig. S1C). Pairs of type-6 sensory spots are located posteriorly in subdorsal, laterodorsal, midlateral, sublateral and ventromedial position (Figs. 3D, 4B and 7B, C; Fig. S1C). Similarly to segment 1, long cuticular hairs arranged in longitudinal rows of three to five each originate from the middle part of the segment and continue beyond the segment's posterior edge. Approximately 9 - 12 rows are present on each sternal plate and 38 - 42 rows on the tergal plate. These rows are absent close to the midsternal junction and also in part of the midlateral area. The same condition is repeated through segments 3 to 9 (Figs. 3E, 4D, 6A—B, Iand 7A—F). Segments 10 and 11 do not bear the rows of cuticular hairs (Figs. 4D, 6I and 7G).

Segment 3 has a middorsal spine, two subdorsal cuspidate spines (Figs. 3D, 6A—B and 7C—E) and two lateroventral acicular spines. Three pairs of type-6 sensory spots are placed laterodorsally, sublaterally, and ventromedially (Figs. 4B and 7C; Fig. S1C).

Segment 4 bears one middorsal spine and two lateroventral acicular spines. Paired type-6 sensory spots are present paradorsally, a pair of type-6 sensory spots is located laterodorsally and another pair ventromedially (Figs. 4B and 7C; Fig. S1C). Ovaries almost reaching the junction between this segment and segment 3 (Fig. 3H).

Segment 5 shows one middorsal spine, two lateroventral acicular spines, and two ventrolateral cuspidate spines slightly displaced ventromedially (Figs. 2A and 7A; Fig. S1D). The cuspidate spines are located next to the edge of the ventromedial position (Figs. 4C, 6B and 7A, F). Pairs of type-6 sensory spots are located laterodorsally and sublaterally. No ventral sensory spots were detected.

Segment 6 bears one middorsal spine and two lateroventral acicular spines (Fig. 4C). Pairs of type-6 sensoryspots are located paradorsally, laterodorsally, sublaterally, and ventromedially (Fig. 7F, I; Fig. S1D). Females bear ventromedial appendages on this segment (Figs. 4C and 7A, F, H).

Segment 7 has one middorsal spine, two pairs of cuspidate spines located paradorsally and sublaterally (Figs. 3E, 6A and 7D, E, I; Fig. S1G), and two lateroventral acicular spines. Apair of type-6 sensory spots is located laterodorsally and a second pair ventromedially (Figs. 4C, D, and 7F, I; Fig. S1D). Females bear ventromedial appendages (Figs. 2 and 7F, H).

Segment 8 bears one middorsal spine, two lateroventral acicular, and two ventrolateral cuspidate spines (Figs. 3E, F, 4D, 6A, and 7A, D; Fig. S1A). Pairs of type-6 sensory spots are placed paradorsally, laterodorsally, and ventromedially (Figs. 4D and 7F; Fig. S1D. Females bear ventromedial appendages (Figs. 2A and 7F).

Segment 9 has one middorsal spine, two lateroventral acicular spines, and two cuspidate spines in lateral accessory position (Figs. 3E - G, 4D, 6A, I, and 7A; Fig. S1E). Pairs of type-6 sensoryspots are located paradorsally, laterodorsally, and ventromedially (Figs. 4D, 6I and 7G; Fig. S1E). Astructure very likely representing the protonephridial opening, marked by minute cuticular papillae, is present in sublateral position (Fig. 6I - J). Ventromedial areas of micropapillae are absent.

Segment 10 is characterized by the presence of a middorsal spine (Figs. 3B, E, 6B, and 7G). Apair of paradorsal type-6 sensory spot is present (Fig. 6I). The teeth of the primary pectinate fringe are shorter and smaller than those on segments 1 - 9. Females bear two thick and short lateroventral acicular spines (Figs. 3A, G, 6I, and 7G; Fig. S1A). Short cuticular hairs are arranged irregularly especially on the sternal plates (Figs. 6I and 7G).

Segment 11 is formed by one tergal and one sternal plate. The latter seems to show a midventral to paraventral cuticular thickening, appearing optically separated from the remaining plate because of a paraventral fold in the cuticle (Figs. 4H and 7G). This segment bears a relatively short midterminal spine and two elongated lateral terminal accessory spines each with two thin areas in the basal part (Figs. 3A, 4H and 6A). Two pairs of type-3 sensory spots, each composed of a conical base and terminal cuticular papillae, are placed laterodorsally and ventrolaterally (Fig. 7G, J). The former are located more centrally on the segment, while the latter are placed posteriorly. Two ventromedial sensory spots are placed anteriorly on the segment, partially hidden by the free flap of segment 10. We could not assign these sensoryspots to any specific type of sensory spot, even though they resemble type-6. Similar structures have been observed in Condyloderes shirleyi Neuhaus & Higgins, 2019 in Neuhausetal. (2019; fig. 42D, F).

The teeth of the primary pectinate fringe are much shorter and smaller than on segments 1 - 9. Females show cuticularized gonopores at the anterior margin of the sternal plate, almost at the junction between segments 10 and 11 (Figs. 3A, G, and 7G).

It was noted that a single female specimen had an indistinct mass of material which may be interpreted as a spermatophore attached to the terminal part of its trunk (Fig. S1A). This would be the second report of potential spermatophore in a cyclorhagid, after the finding in Centroderes drakei Neuhaus, Pardos, SØrensen & Higgins, 2014 (see Neuhaus et al. 2014). The spermatophore was present in both females and male in the species of this closely related genus.

3.1.6. Sexual dimorphism

Males possess a pair of laterodorsal acicular spines on segment 10, extending beyond the posterior edge of segment 10 (Figs. 4G, 6A—B, and 7J; Fig. S1F). The acicular spines on segment 10 are thinner than the acicular spines on other segments (Fig. 4G, Fig. S1F). In addition, males lack gonopores on segment 11, lateroventral acicular spines on segment 10, and ventromedial appendages on segments 6, 7, and 8 (Fig. 4C, D), all of which are present only in females (see chapter 3.1.5.).

3.1.7. Variation

Out of 46 specimens mounted for light microscopy and in a condition to check variation of trunk characters, variation is observed in 22 specimens (= 48%) (Fig. 2; Figs. S2A - I; Table S1). Ten specimens vary in one character, seven in two characters, three in three characters, and one each in five and seven characters. Most variation results from the absence of a cuspidate spine paradorsally on one or both sides of segment 7 and of a type-6 sensory spot sublaterally on segment 5 (Fig. 7E, I; Figs. S2A, D, E; Table 2; Table S1). In two specimens, the paradorsal cuspidate spine is missing on one side of segment 7 and replaced by a sensory spot. One specimen reveals a very short middorsal and laterodorsal spine on segment 10 (Fig. S2H). Another specimen possesses a crippled lateral terminal accessory spine on one side (Fig. S2I). One specimen shows an acicular spine lateroventrally on the right side of segment 5 but a cuspidate spine on the left side of this segment; the ventrolateral cuspidate spine of the left side is missing (Fig. S2C). Three specimens lack a laterodorsal sensory spot on one side of segments 6 or 9 and possess an additional spot paradorsally on the same side of these segments (Figs. S2B and E; Table S1). A type-6 sensory spot may occur in an unusual position on one side only, e. g., lateroventrally on segment 1 (Fig. S2F). Little variation has been found in the arrangement of placids. One specimen shows two narrower placids instead of one broader placid next to the middorsal placid (Fig. S2G).

3.1.8. Ecology

Beyond the type locality of C. agnetis sp. nov., the species was found also at four more sites off Castellammare del Golfo and off the town of Trappeto, a second location placed over 12 km to the east, within the Gulf of Castellammare, Sicily, southern Tyrrhenian Sea (see chapter 3.4.8. and Table 1). The species was collected from both the two areas (off Castellammare and off Trappeto) during four different surveys led from June 2006 to December 2007. The bottom depths of the sampling sites ranged from 32 to 50 m. Sediment was made up on average of silt to very fine sand off Castellammare del Golfo, and very fine sand to coarse silt off Trappeto.

C. agnetis sp. nov. co-occurred with other kinorhynchs, i.e.: Paracentrophyes quadridentatus (Zelinka, 1928), Cristaphyes carinatus (Zelinka, 1928), Pycnophyes communis Zelinka, 1908, Pycnophyes giganteus (Zelinka, 1928), Pycnophyes robustus Zelinka, 1928, Semnoderes armiger Zelinka, 1928, Condyloderes multispinosus (off Trappeto only; see chapter 3.4.8), Echinoderes capitatus (Zelinka, 1928), Echinoderes ferrugineus Zelinka, 1928, and Echinoderes gerardi Higgins, 1978 (Dal Zotto & Todaro 2016). The other meiobenthic taxa associated with C. agnetis sp. nov. were mainly nematodes, harpacticoids, polychaetes, turbellarians, tanaidaceans, ostracods, amphipods, cumaceans, tardigrades, gastropods, bivalves, and cnidarians (Dal Zotto et al. 2016).

The densities of C. agnetis sp. nov. ranged from 1 to 6 individuals/ 10 cm 2. Comparedtothe otherassociatedkinorhynch species it was relatively scarce, but it was also rather common, because it was found at seven out of eight investigated sites off Castellammare del Golfo (Dal Zotto et al. 2016).

Any clear correlations among the abundances of C. agnetis sp. nov. and other co-occurring kinorhynch species were found, with Pearson correlation coefficients varying from —0.18 ( C. agnetis sp. nov. - S. armiger) to 0.44 ( C. agnetis sp. nov. - Pycnophyes spp. juveniles).

One male of C. agnetis sp. nov. from a sample collected at 42 m depth off Rovinj (Croatia, northern Adriatic Sea) was found among the specimens of Condyloderes on loan from the National Museum of Natural History, Smithsonian Institution, Washington D. C. (see Table 1; Figs. S1B - G).

3.1.9. Note on epizoic protozoa

Six epizoic protozoans attached on segments 1 and 7 - 9 to a male specimen from off Rovinj, northern Adriatic Sea (Figs. S1B and G).