Sisubiotus splendidus, Atherton, 2025
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publication ID |
https://doi.org/10.11646/zootaxa.5679.3.5 |
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publication LSID |
lsid:zoobank.org:pub:34EF9B46-7640-4080-B6E6-EA84B34822BE |
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persistent identifier |
https://treatment.plazi.org/id/03818788-FFFF-FFEF-FF02-3BDD7CDDFB4F |
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treatment provided by |
Plazi |
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scientific name |
Sisubiotus splendidus |
| status |
sp. nov. |
Sisubiotus splendidus sp. nov.
urn:lsid:zoobank.org:act:5CC43126-CABC-4444-BE82-80D42FDEAA8F
Figures 4–9 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9
Etymology.
Derived from the Latin splendidus : splendid, due to the beauty of the species and its eggs. Material Examined.
A total of 21 animals and 22 eggs. Specimens mounted on microscope slides in Hoyer’s medium (16a + 19e) or processed for DNA sequencing (5a + 3e).
Type repositories:
Type materials are deposited in the invertebrate collection of the Swedish Museum of Natural History (Frescativägen 40, Stockholm, Sweden)
Type Materials.
Holotype: Animal preserved in Hoyer’s medium. Slide no. SMNH-Type-9994
Paratypes: 15 animals and 19 eggs preserved in Hoyer’s medium. Slides nos. SMNH-Type-9995–10003
Diagnosis.
Species of Sisubiotus , whitish to transparent under LM with black eyespots present anteriorly in living animals ( Figure 4 View FIGURE 4 ). Leg granulation present on legs II–IV ( Figures 5C–G View FIGURE 5 ). OCA with three bands of teeth ( Figure 6 View FIGURE 6 ): the first consisting of numerous small granules at the base of peribuccal lamellae; the second positioned posterior to the ring fold and consisting of an anterior row of longitudinal elongated teeth followed by 3–5 irregular rows of medium granules; the third anterior to the buccal tube opening and consisting of three dorsal and three ventral transversal crests and one or two additional mucrones. Claws of legs I–III with smooth lunules ( Figures 5A–D View FIGURE 5 ), of legs IV with dentate lunules ( Figures 6F–G View FIGURE 6 ). Eggs 140–188 µm full diameter, 86–118 µm bare diameter, with 9–11 processes on the circumference ( Figure 8 View FIGURE 8 ). Processes mostly smooth without labyrinthine layer clearly visible in LM ( Figures 8C–G View FIGURE 8 ). Each process surrounded by 10–12 deep areolae, present in a “1+3” pattern of a single areola between two neighboring processes and three areolae at the junction of three processes ( Figure 9 View FIGURE 9 ). Egg chorion and areolae surfaces evenly reticulated with small mesh.
Description.
The morphometric measurements for animals and eggs are summarized in Table 2 and 3, respectively, and were not Thorpe’s normalized. Results from Thorpe’s normalization found that all of the measured characters for the species were isometric with respect to the length of the buccal tube. The raw morphometric data is provided in supplemental material S6, and the Thorpe’s normalized data is provided in supplemental material S7.
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Living animal whitish; transparent after fixation in Hoyer’s medium; 199–621 µm long ( Figure 4 View FIGURE 4 ). Anteriorly positioned eyes present in living animals, not always visible after fixation in Hoyer’s medium. Cuticle without sculpturing, gibbosities, spines, papillae, or pores. Small patches of fine granulation present on the external surfaces beside the claws of legs II and III ( Figures 5C–D View FIGURE 5 ) as well as dorsal and surrounding the claws of legs IV ( Figures 5E–F View FIGURE 5 ). Granulation on legs I absent. A cuticular bulge (pulvinus) is present on the internal surface of leg pairs I–III, clearly visible when the leg is fully extended ( Figures 5A–B,D View FIGURE 5 ).
Mouth antero-ventral. Bucco-pharyngeal apparatus Macrobiotus - type ( Pilato & Binda, 2010) with ten peribuccal lamellae and ventral lamina present.
The OCA with three well developed bands of teeth, clearly visible with DIC ( Figure 6 View FIGURE 6 ). The first is a wide band of numerous small granules situated at the base of the peribuccal lamellae that, though still visible, may be difficult to detect in smaller animals. The second band is situated just posterior to the ring fold and includes 3–5 rows of medium sized granules, with the teeth in the most anterior row of the second band distinctly larger and more longitudinally elongated than the teeth of the other rows. The third band is present anterior to the buccal tube opening and is divided into a dorsal and ventral part. The dorsal part is composed of a rectangular median transverse ridge and two lateral ridges that thin slightly towards the external margins ( Figures 6A,C,E View FIGURE 6 ). The ventral part comprises paired lateral ridges, a median ridge that is thicker and less wide than the dorsal median ridge, and one or two additional mucrons that are medium or small granules situated just posterior to the median ridge ( Figures 6B,D,F View FIGURE 6 ).
Rigid buccal tube with 26–48 µm (pt 65.7–70.5) long ventral lamina. Stylet supports insert 29–54 µm (pt 13.9– 20.8) from the anterior and lead to typical stylet system. Posterior end of the buccal tube terminates in a distinct thickening and within the pharyngeal bulb. Pharyngeal bulb globular, with triangular apophyses and rows of two macroplacoids and a single microplacoid ( Figure 7 View FIGURE 7 ). In the frontal view ( Figures 7A–B View FIGURE 7 ), the first macroplacoid has a distinct and complex shape: the anterior half has a pointed end, slightly narrows before expanding out to form a pair of bulbous wings towards the midpoint; a distinct constriction is directly posterior to the wings at the midpoint; and a rectangular posterior half terminates with a bluntly rounded end. The second macroplacoid has a nearly rectangular anterior part with a blunt end and very slight constrictions towards the first third and just prior to the posterior end, which expands out into a pair of thicker rounded bulbs. Macroplacoid row length 16–42 µm (pt 41.1–59.3), and placoid row length 20–50 µm (pt 53.1–72.3). Length sequence 2<1, with length of first macroplacoid 9–21 µm (pt 25.4–33.6), second macroplacoid 6–17 µm (pt 15.6–24.6). Microplacoid heart-shaped, 3–8 µm (pt 8.5–12) long and situated closely posterior to the second macroplacoid ( Figure 7B View FIGURE 7 ).
Double claws of the hufelandi type, slender with a long common tract and evident accessory points on the primary branch ( Figure 5 View FIGURE 5 ). Claws generally increasing in length posteriorly, with the claws of legs IV distinctly larger and with larger lunules than those of the other legs. Lunules of claws of legs I–III smooth ( Figure 5B View FIGURE 5 ) and of legs IV weakly dentate ( Figure 5F View FIGURE 5 ). A single, continuous cuticular bar present on each of legs I–III below the lunules ( Figures 5B,D View FIGURE 5 ).
Single ovary located dorso-caudal to the intestine, occasionally with one or two eggs present ( Figure 4C View FIGURE 4 ). Testes, seminal vesicles and seminal receptacles not seen.
Globular eggs laid freely, ornamented with clear, large conical processes, occasionally with frayed or bifurcated tips ( Figure 8 View FIGURE 8 ). Egg diameter including processes 86–118 µm; 9–11 processes on the circumference ( Figure 8A View FIGURE 8 ). Processes surrounded by 10–12 deep areolae, present in an alternating pattern of a single, large areola between two neighboring processes and three smaller areolae located at the junction of three processes ( Figures 8B View FIGURE 8 , 9 View FIGURE 9 ). Areolae surface reticulated with a small mesh that appears as many dots or small wrinkles under LM ( Figure 8E View FIGURE 8 ). Processes transparent with bubbles sometimes present near the apices ( Figure 8C,F View FIGURE 8 ), mostly smooth but with occasional, irregularly distributed wrinkles or dots ( Figures 8F–G View FIGURE 8 ). A labyrinthine layer between the process walls not distinguishable under LM.
DNA Sequences.
Sequences for Sis. splendidus sp. nov. were obtained for all three markers from two animals and one egg. The 28S was represented by one haplotype; 18S was represented by two haplotypes (uncorrected p-value between haplotypes 0.06%); and COI was represented by two haplotypes (uncorrected p-value between haplotypes 0.33%):
- 28S: 831 bp; GenBank accession number PV744341
- 18S haplotype 1: specimens 24-426, 24-430; 1690 bp; GenBank accession number PV744336
- 18S haplotype 2: specimen 24-411; 1690 bp; GenBank accession number PV744335
- COI haplotype 1: specimens 24-411, 24-430; 612 bp; GenBank accession number PV746802
- COI haplotype 2: specimen 24-426, 612 bp; GenBank accession number PV746803
Morphological differentiation.
All five species of Sisubiotus , including the new species, are very similar morphologically with only few differentiating characters present in the adult animals or eggs. Nevertheless, Sisubiotus splendidus sp. nov. is most easily distinguished from all others of the genus by the dentate lunulae of the claws of legs IV (the other species have only smooth lunulae) and the leg granulation that is present only on legs II–IV ( Sis. spectabilis , Sis. grandis and Sis. hakaiensis have granulation present on all legs, while Sis. wuyishanensis lacks leg granulation). More cautiously (see discussion on the eggshells of Sis. spectabilis below), the eggs of Sis. splendidus sp. nov. exhibit a distinct “1+3” areolae pattern ( Figure 9 View FIGURE 9 ) rather than the double row of areolae that surrounds the processes of the other species (excepting Sis. wuyishanensis , which purportedly lacks egg areolae entirely—but see Stec et al. 2021).
Additionally, Sis. splendidus sp. nov. differs from:
1. Sisubiotus spectabilis (following the description of Stec et al., 2021) by a longer ventral lamina (pt 65.7–70.5 in the new species vs 54.8–64.8 in Sis. spectabilis ) and smaller claws (e.g. external claw of leg II pt 18.6–24.2 vs. 24.3–36.8; posterior claw of leg IV pt 26.3–29.7 vs. 29.8–38.8);
2. Sisubiotus grandis (following the description of Maucci & Pilato, 1974) by the location of the eyespots in living animals (anterior in the new species vs. posterior in Sis. grandis ), the more numerous teeth in the second band of the OCA, and the reticulation of the entire egg areolae (the center of the egg areolae is smooth in Sis. grandis );
3. Sisubiotus hakaiensis by the smaller eggs (bare diameter 86.0–117.5 µm vs. 126.0–134.0 µm) that labyrinthine layer in the process walls not visible with LM;
4. Sisubiotus wuyishanensis (species inquirenda) by the smaller claws on leg I (primary branch of external claw pt 18.6–22.5 in the new species vs. pt 23.7–27.1 in Sis. wuyishanensis ) and leg II (pt 18.6–24.2 vs pt 23.3–26.8) and by the smaller number of processes on the egg circumference (9–11 vs. 13) with wider bases (20.7–31.3 µm vs 20.5 µm).
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