Cateria styx Higgins, 1968

Cateria styx Higgins, 1968 from Chile

( Figs 26–28 View FIGURE 26 View FIGURE 27 View FIGURE 28 , Tables 4, 7, 10, 11)

Material examined. Table 1 lists the localities from which specimens were obtained (see also Fig. 1 View FIGURE 1 ) and the museum collection where the material is deposited.

Description. Mouth cone ( Fig. 27A View FIGURE 27 ) as well as scalid morphology and arrangement ( Fig. 26A–C, F View FIGURE 26 ) agree widely with those described for C. gerlachi from Sri Lanka, but placids cannot be recognized as individual elements. A type-5 sensory spot with a long, curled cuticular tube occurs subdorsally and lateroventrally in the placid area.

For measurements and dimensions see Table 7; for summary of spine, gland cell outlet, and sensory spot locations see Table 4.

Scalids. The spinoscalids and trichoscalids are arranged as in C. gerlachi ( Figs 3 View FIGURE 3 , 26C, F View FIGURE 26 ). Anterior to the primary spinoscalids is a pair of elongate spinose processes with a strongly sclerotized base but no shorter spinose processes ( Fig. 26C, F View FIGURE 26 ). Each primary spinoscalid itself consists of a long basal part, a long central part with internal septa and an outer annulation, and a shorter flexible terminal part with a blunt tip ( Fig. 26A View FIGURE 26 ). The internal septa and the outer annulation of the central part of the spinoscalid are weak and barely visible in light microscopy ( Fig. 26A View FIGURE 26 ). The central part of the primary spinoscalids possesses anteriorly a fringe of cuticular hairs on the side facing away from the head. Out of the 10 primary scalids, 6 are slightly longer than the remaining 4. The primary spinoscalids are the longest of the introvert. Ring 02 spinoscalids are slim and show basally bar-like thickenings in the introvert’s cuticle, namely four thickenings in odd sectors and two thickenings in even sectors ( Fig. 26C, F View FIGURE 26 ). Ring 03–05 spinoscalids are more robust than the spinoscalids of ring 02. Trichoscalids are arranged as in C. gerlachi ( Fig. 26A, B View FIGURE 26 ). One male (USNM 1226595b) reveals a bifurcate lateroventral trichoscalid on one side only ( Fig. 26A, B View FIGURE 26 ).

Trunk. The description refers to females. Trunk characters agree widely with those of C. styx from Brazil, so mainly the differences are mentioned in the following. The cuticle of segments 1–10 ( Figs 26 D, E, G View FIGURE 26 , 27D–H View FIGURE 27 ) does not seem to differ from the specimens found in Brazil, but little information is available for the ventral cuticle of segment 11. On segment 1, the scales are missing in a longitudinal area middorsally, about subdorsally, about midlaterally, and ventromedially. In these areas, the cuticle shows a granular appearance ( Fig. 26B View FIGURE 26 ).

The secondary fringe of segments 2–11 may take up more than one half of the segment’s length and consists of leaf-like cuticular hairs which are usually deeply split into two hairs and a posterior line of spinose hairs. The leaf-like hairs of the secondary fringe are arranged more or less regularly in 7 (anterior segments) to 17 (more posterior segments) lines. Anterior of these lines, up to four cuticular areas per side and additional 2–4 lines of leaf-like hairs alternate ( Figs 26D, G View FIGURE 26 , 27B, F–H View FIGURE 27 ). Posterior of the lines, one line of straight spinose cuticular hairs occurs ventrally on the tergal plate of segments 4–10 and also dorsally at least on segments 7–9. These hairs are considerably more prominent on the ventral side of the tergal plate on segments 4 and 5 ( Fig. 27D View FIGURE 27 ).

The central area of each segment shows a narrow, longitudinal sculpturing of the cuticle in light microscopy ( Figs 26E View FIGURE 26 , 27F–H View FIGURE 27 ). From the few SEM photographs available for this species, the sculpturing is interpreted as to represent scales which become more three-dimensional on posterior segments. It seems there is only a single line of scales in the central area of segments 1–9, but several rows on segments 10 and 11. The central area seems to be missing ventrally on the tergal plate of segments 2 and 3 and to be covered by the long spinose hairs of the secondary fringe ventrally on the tergal plate of segments 4–9. The posterior part of the intersegmental cuticle and the midlateral and paraventral attachment sites of the dorsoventral muscles are covered by low, mainly longitudinal cuticular ridges ( Figs 26G View FIGURE 26 , 27F–H View FIGURE 27 ). The attachment sites of the dorsoventral muscles appear as single elongate-oval cuticular areas without any scales ( Figs 26G View FIGURE 26 , 27F–H View FIGURE 27 ). The quite extensive free flap exhibits an even narrower and more elongate sculpturing than the central area and ends in the primary fringe which consists of numerous short, thin cuticular hairs ( Figs 26D, E, G View FIGURE 26 , 27D–H View FIGURE 27 ). On segment 10, these hairs are longer but less strongly sclerotized than in C. styx from Brazil.

Sensory spots and gland cell outlets resemble those described for C. styx from Brazil and are arranged similarly ( Table 4). The largest type-1 sensory spot exists midlaterally to sublaterally on segment 2. It shows two pores at the anterodorsal margin of the spot and one or two pores centrally in the oval area with micropapillae ( Fig. 26G View FIGURE 26 ) giving the impression of a small and a large sensory spot fused in a single organ. Whereas specimens from Chile always possess a midlateral type-5 sensory spot posteriorly on segment 5, the Brazilian specimens reveal this organ in five animals but lack it in 10 (Table 10). Also, the sublateral position on segment 6 shows more often a gland cell outlet in the Chilean material, but a type-5 sensory spot in the Brazilian specimens ( Table 4). However, variation is significant in this position (cf. Tables 10 and 9).

Gland cell outlets differ in several positions from the specimens of Brazil ( Table 4). The Brazilian material shows a gland cell outlet laterodorsally on segment 1, but this is missing in the Chilean animals ( Table 4). Vice versa, the Chilean specimens possess a gland cell outlet subdorsally on segment 1, laterodorsally on segment 3, midlaterally on segment 1, in a lateral accessory position on segment 4, lateroventrally on segment 1, ventrolaterally on segment1 (possibly only males), and ventromedially on segment 5; these gland cell outlets are lacking in the animals from Brazil ( Table 4).

The lateral terminal spine and the lateral terminal accessory spine are covered by numerous fine cuticular hairs. The midlateral spine on segment 11 shows a 9–11 µm long sclerotization area in the trunk cuticle ( Fig. 28A, B View FIGURE 28 ).

The cone-shaped dorsal organ (length 78–90 µm, width 30–44 µm) at the border of segments 5 and 6 is often protruded and reveals on its dorsal side a considerably crumpled cuticle ( Fig. 27B View FIGURE 27 ) whereas the ventral cuticle appears smooth in light microscopy but less deep crumpled in SEM ( Fig. 27C View FIGURE 27 ). If withdrawn, the regular trunk cuticle covers the dorsal organ entirely.

The female reveals an oval area surrounded by a ring of sclerotized cuticle on both sides lateroventrally at the border of segments 10 and 11. This structure is interpreted as a gonopore ( Fig. 28C View FIGURE 28 ).

Sexual dimorphism. Among the 9 adult specimens, five specimens reveal gonopores and are therefore regarded as females. Another specimen shows female characters but no obvious eggs or gonopores and is termed here as adult of undetermined sex but probably female. No specimen has been found revealing obvious elongate sperm. However, three specimens mounted for light microscopy and one for SEM do differ in several characters from the female. This potential male stage agrees in all cuticular characters with the female but can be distinguished from the female (1) by a modified acicular spine lateroventrally and middorsally on segment 10 ( Fig. 28A, B View FIGURE 28 ), (2) by the existence of a broad cuticular flap on segment 11 ( Fig. 28B View FIGURE 28 ) vs the lack of this structure in the female and adults of undetermined sex, (3) the lack of a ventrolateral gland cell outlet anterior on segment 11 vs its existence in the female and adult of undetermined sex, and (4) in the existence of a gland cell outlet ventromedially on segment 1 vs its lack in the female and adult ( Table 4).

The lateroventral spine on segment 10 of males is not straight as in the female and adults of undetermined sex but modified revealing usually a broader base and tapering towards its tip. Also, the tip of this spine is bent upwards terminally and seems to possess an indentation in this part ( Fig. 28A, B View FIGURE 28 ). The length of the middorsal spine on segment 10 of males reaches less than one third of the length of this spine in females ( Table 7; Fig. 28A, C View FIGURE 28 ). The cuticular flap anteriorly on segment 11 is broad with a rounded posterior margin and occupies a lateral accessory to midlateral position, so the center is about sublaterally. The flap reveals a tuft of hairs subdorsally and posteriorly ( Fig. 28B View FIGURE 28 ).

Variation of characters. Three females and two males ( USNM 12265995 About USNM a–c, 12265996, 12265997) differ significantly in almost all measurements from the remaining specimens in that they are larger and possess larger spines ( Table 7). Most positions of sensory spots and gland cell outlets are quite constant, but variation does occur (Table 10). Only on few certain segments and positions the occurrence of sensory spots and gland cell outlets varies to a higher degree such as paradorsally on segments 2, 3 and 7–9 (Table 10). This may be caused by the few specimens studied .

Postembryonic stages. The single specimen available reveals 11 separated segments and agrees in its cuticular characters such as the distribution of leaf-like cuticular hairs and postmarginal spicula with the latest stage found for this species from Brazil. A type-3 sensory spot is recognizable in the extension of the segment next to the midterminal spine. A gland cell outlet seems to exist midlaterally on segment 5 and sublaterally on segment 6. The specimen reveals a lateroventral tube on segment 5, a spine middorsally on segments 2–4, 6, 8–11 (= midterminal spine, midlaterally on segment 11, lateroventrally on segments 6–11 (= lateral terminal spine), and in a lateral accessory position on segment 11 (= lateral terminal accessory spine) ( Fig. 28D View FIGURE 28 ).