Cateria styx Higgins, 1968

Cateria styx Higgins, 1968 from Brazil

( Figs 20–25 View FIGURE 20 View FIGURE 21 View FIGURE 22 View FIGURE 23 View FIGURE 24 View FIGURE 25 , Tables 4, 6 −9, 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.

Diagnosis. Segments 1–6 with one midventral sternal plate and one tergal plate; segments 7–10 with single tergal plate whose lateral ends meet midventrally; segment 11 with single circular cuticular plate. Retractible dorsal organ at border of segments 5 and 6. With acicular spine middorsally on segments 2–4, 6, 8–10 and 11 (= midterminal spine), midlaterally on segment 11, in lateral accessory position on segment 11 (= lateral terminal accessory spine), and lateroventrally on segments 6–10 and 11 (= lateral terminal spine); blunt tube lateroventrally on segment 5; middorsal spine of segment 10 short with blunt tip in male, lateroventral spine on segment 10 bent terminally and with subterminal indentation in male. Type-1sensory spot middorsally on segment 1, paradorsally on both sides of segment 10 and either on the left or on the right side of segments 2, 3 and 7–9, subdorsally on segment 11 just anterior of a terminal type-3 sensory spot in the process neighbouring the midterminal spine, laterodorsally on segment 11 (central part of segment), about midlaterally on segments 1 and 2 (the former usually intermediate to sublateral position), ventrolaterally on segment 11 (central part of segment), and ventromedially on segments 2–4; type-3 sensory spot on segment 11 subdorsally terminally on the process neighbouring the midterminal spine; type-5 sensory spot middorsally on segments 2–10 (anterior part of segment), paradorsally on both sides of segments 4 and 6 and either on the left or on the right side of segment 5, subdorsally on neck (central part) and on segment 9 (posterior part), midlaterally on segments 4 and 6–9 (posterior part), sublaterally on segment 10 (posterior part), in a lateral accessory position on segments 3–7 (anterior part), lateroventrally on segments 8 and 9 (anterior part), ventrolaterally on segment 10 (anterior part) and on segments 6–10 (posterior part), and ventromedially on segments 7 and 10 (posterior part). Gland cell outlet in posterior part of segment paradorsally often but not always on one side of segments 5 and 7, subdorsally on segments 3–8 and 10, laterodorsally on segment 2, midlaterally on segment 3, sublaterally on segments 3–5 and 7–9, in a lateral accessory position on segment 1, lateroventrally on segment 2 (anterior part), ventrolaterally to ventromedially on segments 2 and 3, and ventromedially on segments 6, 8 and 9. Male distinguished from female (1) by modified spine middorsally and lateroventrally on segment 10, (2) by broad cuticular flap anteriorly on segment 11 vs lack of this structure in female, (3) lack of ventrolateral gland cell outlet in anterior part of segment 11 vs its existence in female, and (4) long but little sclerotized hairs of primary fringe on segment 10 vs longer and stronger sclerotized hairs in this position in female.

Redescription. The following description refers to females ( Fig. 20A, B View FIGURE 20 ). The introvert of the specimens from Brazil is usually only partly protruded ( Fig. 21A–C View FIGURE 21 ), and the mouth cone is retracted in all specimens studied except one ( Fig. 21E View FIGURE 21 ). However, the outer and inner oral styles can be recognized ( Fig. 21D View FIGURE 21 ), because inner organs except cuticular structures are more or less dissolved by the embedding medium. For measurements and dimensions see Table 7; for summary of spine, gland cell outlet, and sensory spot locations see Table 4.

Mouth cone. Each of the nine 51–63 mm long outer oral style consists of three jointed elements ( Fig. 21D, E View FIGURE 21 ). The 10–11 µm long apical element bends towards the mouth opening and reveals a short triangular process at its base ( Fig. 21E View FIGURE 21 ). The articulation between the 18 µm long basal and the ca. 23 µm long intermediate element is located at a different level in neighbouring styles, because the basal elements are of different lengths ( Fig. 21D View FIGURE 21 ). Probably, two or three rings of inner oral styles occur with five hook-like styles in the second ring. The posteriormost ring of inner oral styles seems to contain two different types of styles.

Scalids. The number of spinoscalid rings are difficult to figure out. Anterior of the primary spinoscalids, a ring of 10 pairs of thin, ca. 55 µm long cuticular spines are found ( Fig. 21C View FIGURE 21 ). Basally, the cuticle of the spines is significantly thickened for about 6 µm (see Fig. 26F View FIGURE 26 of specimen from Chile). Spinoscalids seem to be arranged in 5 rings and distributed similarly if not identically as in C. gerlachi . Ring 02 spinoscalids are thinner than scalids of subsequent rings.

The posteriormost ring of spinoscalids is followed by 14 areas of cuticle covered with short cuticular hairs appearing as fine ‘denticles’ in light microscopy and separated from each other by longitudinal folds of smooth cuticle ( Fig. 21 F, G View FIGURE 21 ). Each of the areas with the short cuticular hairs is succeeded posteriorly by a trichoscalid except midventrally. Therefore, 13 trichoscalids of variable length occur, namely a very short middorsal trichoscalid, a long paradorsal scalid (33 µm), a short subdorsal scalid (10–12 µm), a long midlateral scalid (20–30 µm), a short lateral accessory (10–14 µm) and lateroventral (14–18 µm) scalid, and a very long ventromedial scalid (28–37 µm) ( Fig. 21F, G View FIGURE 21 ). All trichoscalids are covered with numerous cuticular hairs.

Neck. No individual placids are recognizable in any specimen. A type-5 sensory spot with a long, curled cuticular tube occurs subdorsally and lateroventrally in the placid area.

Trunk. The body cuticle is thin, transparent, and flexible, specimens may bend their anterior end closely to their posterior end ( Fig. 21A, B View FIGURE 21 ). At the anterior margin, each segmental cuticular plate does not seem to thicken towards the interior of the body, a pachycyclus is lacking ( Figs 21F, G View FIGURE 21 , 22A–C View FIGURE 22 , 23A, B View FIGURE 23 , 24D, E View FIGURE 24 ). The anterior six trunk segments possess one almost rectangular midventral sternal plate and one tergal plate, whereas segments 7– 10 show a single tergal plate whose lateral ends meet midventrally, and segment 11 yields a single ring-like cuticular plate ( Figs 20A, B View FIGURE 20 , 21F, G View FIGURE 21 , 22A–D View FIGURE 22 ). The tergal plate of segment 11 shows on both sides a caudal, triangular extension that exceeds the posterior margins of the ventral cuticle and accompanies the midterminal spine. Terminally it bears a type-3 sensory spot ( Fig. 24E View FIGURE 24 ). The surface of the cuticle reveals from anterior to posterior the intersegmental cuticle, the secondary fringe consisting of leaf-like and spinose hairs (only on segments 2–11), a central area with cuticular scales appearing as longitudinal striation in light microscopy, and a posterior free flap which extends partly over the subsequent segment ( Figs 21F, G View FIGURE 21 , 22A–D View FIGURE 22 , 23A–C View FIGURE 23 ). Segment 1 does not reveal any leaf-like cuticular hairs but broad scales like cobbled pavement with a short posterior cuticular process raising above the surface ( Figs 21 F, G View FIGURE 21 , 23A View FIGURE 23 ). The processes are stronger and arranged denser on the midventral sternal plate of segment 1 than laterally and dorsally on the tergal plate ( Fig. 21 F, G View FIGURE 21 ). The scales appear as “denticulation pattern” in light microscopy. Segment 1 is devoid of the processes in a middorsal, subdorsal, midlateral, and almost ventromedial area extending from the anterior margin of the segment almost to its posterior margin ( Fig. 20A View FIGURE 20 , 21 F, G View FIGURE 21 ). A small area of scales appearing as longitudinal striation occurs in the central part of the segment between the processes and the free flap.

The midventral sternal plate of segment 2 is covered anteriorly with the same kind of broad scales with a posterior cuticular process as on segment 1. On the tergal plate of segments 2–11 and on the midventral sternal plate of segments 3–6, a secondary fringe consisting of leaf-like cuticular hairs regularly arranged in about 8 and 9 lines is found on anterior segments ( Fig. 22A View FIGURE 22 ) but about 12 lines on posterior segments. These hairs appear hook-like in optical longitudinal section. The regular arrangement of the lines of the leaf-like hairs is disturbed lateroventrally on segments 2–11. It cannot be decided whether or not spinose hairs arranged in a single line posterior of the lines of leaf-like hairs exist at least on some segments on the ventral side.

The central part of the segments with its narrow longitudinal striation is more extensive laterally and dorsally on segments 2–11. A patch of short, straight cuticular hairs occurs midventrally on segments 7–10 along the segments’ length ( Fig. 22B–D View FIGURE 22 ). Ventrally, segment 11 shows in its anterior half a midventral and next to the lateral spines a lateral area of short cuticular hairs. Such hairs are scattered over the posterior half of the segment.

The free flap ends in a primary fringe consisting of thin, short cuticular hairs. These hairs are longer and considerably more sclerotized dorsally and laterally on segment 10 ( Fig. 24C, D View FIGURE 24 ). The free flap of segments 2–11 reveals a deep notch where a spine or a tube originates as well as lateroventrally on segments 2–4 and about ventromedially on segments 7–10. Therefore, the flap consists ventrally of a single lobe on segments 2–6 and of two lobes on segments 7–10.

Sensory spots and gland cell outlets resemble those described for C. gerlachi from Sri Lanka and are arranged similarly ( Table 4; Fig. 20A, B View FIGURE 20 ). Type-1 sensory spots exist middorsally on segment 1 ( Fig. 23A View FIGURE 23 ), paradorsally on both sides of segment 10 and either on the left or on the right side of segments 2 ( Fig. 23A View FIGURE 23 ), 3, 7 ( Fig. 23C View FIGURE 23 ), 8 and 9, subdorsally on segment 11 just anterior of a terminal type-3 sensory spot in the process neighbouring the midterminal spine, laterodorsally on segment 11 (central part of segment), about midlaterally on segments 1 and 2 (the former usually intermediate to sublateral position; Fig. 21G View FIGURE 21 ), ventrolaterally on segment 11, and ventromedially on segments 2–4. A type-3 sensory spot is found subdorsally terminally on the process next to the midterminal spine of segment 11. Sensory spots type-5 appear middorsally on segments 2–10 (anterior part of segment), paradorsally on both sides of segments 4 and 6 and either on the left or on the right side of segment 5, subdorsally on segment 9 (posterior part), midlaterally on segments 4–9 (posterior part), sublaterally on segments 6 and 10 (posterior part), in a lateral accessory position on segments 3–7 (anterior part), lateroventrally on segments 8 and 9 (anterior part), ventrolaterally on segment 10 (anterior part) and on segments 6–10 (posterior part), and ventromedially on segments 7 and 10 (posterior part).

The largest type-1 sensory spot exists midlaterally to sublaterally on segment 2 ( Fig. 21G View FIGURE 21 ). This spot reveals two pores at its anterodorsal margin and one to two pores centrally in the large oval area of micropapillae giving the impression of a small and a large sensory spot fused in a single organ (comp. Fig. 26G View FIGURE 26 for C. styx from Chile). The posterior type-5 sensory spots on segments 6–10 just next to the lateroventral spines are rather small, they consist of a single pore and very few micropapillae; therefore, they are difficult to trace in some specimens. About midlaterally on segment 4, a small oval area appears dorsal of the attachment site of the dorsoventral muscles. A pore surrounded by substructures can be traced in one specimen ( USNM 1226573 About USNM ) but not in the others. It remains open whether or not this structure represents a type-5 sensory spot. The ventrolateral type-5 sensory spot in the central part of segment 11 seems to lie in a depression. In light microscopy, anterior middorsal, lateral accessory, lateroventral, and ventrolateral sensory spots exhibit a well developed cuticular ring around each of the two pores .

Gland cell outlets occur in the posterior part of a segment occasionally paradorsally on one side of segments 5 and 7, subdorsally on segments 3–8 and 10, laterodorsally on segment 2, midlaterally on segment 3, sublaterally on segments 3–5 and 7–9, in a lateral accessory position on segment 1, lateroventrally on segment 2 (anterior part), ventrolaterally to ventromedially on segments 2 and 3, and ventromedially on segments 6, 8 and 9 ( Tab. 4; Figs 20A, B View FIGURE 20 , 21G View FIGURE 21 , 22A–D View FIGURE 22 , 23A–C View FIGURE 23 ). A simple pore anteriorly and ventrolaterally on segment 11of females probably represents a gland cell outlet, too.

An acicular spine is located middorsally on segments 2–4, 6, 8–10 and 11 (= midterminal spine), midlaterally on segment 11, in lateral accessory position on segment 11 (= lateral terminal accessory spine), and lateroventrally on segments 6–10 and 11 (= lateral terminal spine) ( Figs 20A, B View FIGURE 20 , 21A, B View FIGURE 21 , 22A–D View FIGURE 22 , 23A–C View FIGURE 23 , 24C–E View FIGURE 24 ). The middorsal spine of segment 10 and the midterminal spine are very long ( Fig. 21A, B View FIGURE 21 ), usually show internal septa in their basal parts, and taper abruptly after one fourth to one third of the spines’s length ( Fig. 24C View FIGURE 24 ). The articulation of the lateral terminal accessory spine reveals a complex dorsal sclerotization of the cuticle. The midlateral spine on segment 11 shows a 4–5 µm long sclerotization area in the trunk cuticle ( Fig. 24B, C View FIGURE 24 ). A blunt tube with a thin outer cuticle and an inner cuticular tube occurs lateroventrally on segment 5 originating directly anterior of the lateroventral notch in the free flap. The tube appears broad at its base and tapers towards its tip ( Fig. 22A View FIGURE 22 ).

The cone-shaped dorsal organ (length 37–47 µm, thickness 13–23 µm) at the border of segments 5 and 6 is sometimes protruded ( Figs 21A, B View FIGURE 21 , 23D View FIGURE 23 ) and reveals on its dorsal site a considerably crumpled cuticle ( Fig. 23D View FIGURE 23 ) whereas the ventral cuticle appears smooth ( Fig. 23D View FIGURE 23 ). In one specimen, two basal tissue processes occur. If withdrawn, the regular trunk cuticle covers the dorsal organ entirely ( Fig. 23B View FIGURE 23 ).

An oval, weakly sclerotized gonopore can be traced lateroventrally at the border of segments 10 and 11 of 14 specimens ( Fig. 24E View FIGURE 24 ).

The midgut of four specimens harbours one or two diatoms and some debris ( Figs 23C View FIGURE 23 , 25A View FIGURE 25 ).

The protonephridia seem to open to the outside in the lateral accessory position of the posterior part of segment 9.

Two specimens exhibit a tuft of filamentous structures either middorsally on segment 2 or ventrally on segments 6 and 7 which probably represent fungi ( Fig. 25B View FIGURE 25 ).

Sexual dimorphism. Among the 33 adult specimens, none except one reveals gonads with eggs or obvious elongate sperm. One female specimen in the process of moulting ( USNM 1226567 About USNM ) reveals in its exuvia seven small, coiled up filamentous structures ( Fig. 24D, E View FIGURE 24 ) which are here suggested to represent sperm. However, 19 specimens exhibit obvious gonopores and are therefore regarded as females. From the 33 adult specimens, 9 specimens do differ in four characters from the females. This potential male stage agrees in almost all cuticular characters with the female but can be distinguished from the female (1) by a modified spine middorsally and lateroventrally on segment 10 ( Figs 20C View FIGURE 20 , 24A, B View FIGURE 24 ), (2) by the existence of a broad cuticular flap anteriorly on segment 11 ( Figs 20C View FIGURE 20 , 24B View FIGURE 24 ) vs the lack of this structure in the female, (3) the lack of a ventrolateral gland cell outlet in the anterior part of segment 11 vs its existence in the female ( Table 4), and (4) the existence of long but little sclerotized hairs of the primary fringe on segment 10 vs longer and stronger sclerotized hairs in this position in the female ( Fig. 24C, D View FIGURE 24 ) .

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 these spines is bent upwards terminally, seems to possess a subterminal indentation in this part, and ends more or less bluntly ( Figs 20C View FIGURE 20 , 24A View FIGURE 24 ). The middorsal spine on segment 10 of the male is considerably shorter than that of the female and ends with a blunt tip in all specimens which have not lost the spine during preparation ( Table 4; Figs 20C View FIGURE 20 , 24B View FIGURE 24 ). 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. No further substructures like a subdorsal and posterior tuft of hairs can be recognized ( Fig. 24B View FIGURE 24 ).

Variation of characters. Most positions of sensory spots and gland cell outlets are quite constant, but variation does occur (Table 9). Only on 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, 5 and 7–9, midlaterally on segments 5– 9, and sublaterally on segment 6 (Table 9).

Postembryonic stages. Five specimens mounted in lateral view for light microscopy are identified as juveniles. The individuals are preliminarily assigned to four different stages a−d based on different character sets (see below; Table 6) which in no way is meant to indicate that C. styx develops via just four juvenile stages. All specimens are covered by regularly arranged leaf-like cuticular hairs on all segments except in a ventrolateral to almost sublateral area on segment 1 (see Fig. 25G View FIGURE 25 for a later stage) and where the dorsoventral muscles attach to the cuticle. The trunk segments carry at their posterior margins cuticular postmarginal spicula (see below; Fig. 25G View FIGURE 25 ). The lateral mounts do not allow to figure out whether or not midsternal plates exist. The thin body cuticle results in an irregularly bulging cuticle. A free flap overlapping partly the subsequent segment is missing ( Table 6). Consequently, notches in the cuticle at the origin of spines are also lacking. Individual placids cannot be recognized. At least earlier juvenile stages reveal considerably fewer sensory organs and gland cell outlets. Sensory spots appear as type-1 spots with a more or less oval patch of micropapillae around a pore as well as type-3 spots with a small circular patch of micropapillae around a pore on a cone-like base. Gland cell outlets elevate above the trunk surface as a thick-walled spherical structure. A dorsal organ has not been traced in any specimen.

A single specimen (USNM 1226555) represents the earliest stage found, named juvenile stage a in Table 6. The trunk reveals 9 anterior segments and a still fused segment consisting of the prospective segments 10 and 11 ( Tabs 6, 8; Fig. 25C View FIGURE 25 ). A type-1 sensory spot is located at least paradorsally on segment 6, laterodorsally on segment 11, and midlaterally on segment 2 ( Table 6). A conical process accompanies the midterminal spine on both sides and may possess a type-3 sensory spot. An acicular spine seems to occur middorsally on segments 2–4, 6, 8, 9 and twice on 10+11 (centrally on segment and as midterminal spine), and lateroventrally on segments 6 and 8 and as anlage on segment 11 (= anlage of lateral terminal spine; Tabs 6, 8; Fig. 25C View FIGURE 25 ). The latter shows a broad, almost triangular base, tapers abruptly, and ends with a quite spinose tip ( Fig. 25C View FIGURE 25 ). The middorsal spine on segment 9 is significantly longer than any other spine of the specimen ( Table 8). Both this spine and the middorsal spine on segment 10 taper abruptly but the midterminal spine does not.

A specimen of a subsequent stage (USNM 1226556), named juvenile stage b in Table 6, differs from the above described stage in the existence of an additional acicular spine lateroventrally on segments 7, 9 and 10+11 ( Table 6; Fig. 25D View FIGURE 25 ). Segment 1 exhibits a middorsal spinose process which is already mentioned by Higgins (1968) as seta. The lateral terminal spine on segment 11 still persists as anlage with a broad, almost triangular base, taperering abruptly, and ending in a spinose tip ( Table 6; Fig. 25D View FIGURE 25 ). In addition, the middorsal spine of segment 10 represents now the longest spine ( Tab. 8). Both this spine and the midterminal spine taper abruptly and reveal internal septa, whereas the midterminal spine of segment 9 is straight. Outer oral styles appear as 5 longer styles with a significantly broader, bottle-like base alternating with 4 shorter styles with a narrow base.

A third specimen represents a subsequent stage (USNM 1226557), named juvenile stage c in Table 6, which can be distinguished from the specimen mentioned before by the presence of a midlateral spine on segment 11, a fully developed lateral terminal spine, an anlage of the lateral terminal accessory spine ( Table 6; Fig. 25E View FIGURE 25 ), and a lateroventral tube on segment 5. The anlage of the lateral terminal accessory spine reveals a broad, almost triangular base, tapers abruptly, and ends in a spinose tip ( Fig. 25E View FIGURE 25 ). The specimen is moulting. The process lateral of the midterminal spine is significantly larger and reveals a subterminal type-1 and a terminal type-3 sensory spot ( Table 6). A type-1 sensory spot also appears midlaterally on segment 1 and possibly on segment 2. Gland cell outlets are recognizable at least paradorsally on segments 5 and 7 ( Table 6). Both the middorsal spine on segment 10 and the midterminal spine taper abruptly, but internal septa cannot be traced, probably because of a preservation artifact (see other specimens).

The fourth and fifth specimen (USNM 1226568, 1226579), named juvenile stage d in Table 6, possess a fully developed lateral terminal accessory spine ( Fig. 25G View FIGURE 25 ) and 11 separated trunk segments ( Fig. 25F, G View FIGURE 25 ) but resemble the previous stage otherwise ( Table 6). An additional type-1 sensory spot occurs now paradorsally on one side of segment 2. The middorsal spine of segment 10 and the midterminal spine taper abruptly and show internal septa ( Table 6).

Among the adult specimens, three females are found moulting to a second female stage ( USNM 1226567 About USNM , 1226577 About USNM , 1226583 About USNM ) ( Fig. 24D, E View FIGURE 24 ) and two males moulting to a second male stage ( USNM 1226565 About USNM , 1226574 About USNM ). No morphological differences are recognizable between the two female stages and between the two male stages, respectively. The moulting females show gonopores in their old cuticle ( Fig. 24E View FIGURE 24 ). The moulting males reveal a short middorsal spine and a lateroventral spine bent terminally on segment 10 in their old cuticle. None of these specimens moulting and of those specimens addressed as female and male C. styx show postmarginal spicula at any place of the posterior border of the segmental cuticle ( Table 6) .