Caymanostella scrippscognaticausa, Shen & Koch & Seid & Tilic & Rouse, 2024

Shen, Zihui, Koch, Nicolás Mongiardino, Seid, Charlotte A., Tilic, Ekin & Rouse, Greg W., 2024, Three New Species of Deep-Sea Wood-Associated Sea Stars (Asteroidea: Caymanostellidae) from the Eastern Pacific, Zootaxa 5536 (3), pp. 351-388 : 363-371

Caymanostella scrippscognaticausa sp. nov.

Figures 5–10

Alvarado et al. (2022) Table 1, as Belyaevostella sp. , Caymanostella sp.

Diagnosis. Adult body stellate. Juveniles pentagonal to subpentagonal. Abactinal plates oval to polygonal shaped with curved margin. Abactinal armament spiniform and sparsely distributed. Central disc plates of various sizes but similar shapes and imbricating in irregular cycles. One row of dorsal-lateral plates on each side of a row of carinal plates which are less discernible closer to arm base. Terminal plate square-shaped. Each inferomarginal plate larger than adjoining superomarginal plate. Gonopores visible, located in notches at the radial margin of the proximal-most superomarginal plates. Madreporite single pore or slit to complex grooves. Wide, robust adambulacral spines.

Materials Examined. Holotype: SIO-BIC E11441, on wood at Mound 11, Costa Rica, 8.9221 ° N, 84.3045 ° W, 1010 m depth, November 3, 2018, HOV Alvin dive 4988, collectors Victoria Orphan and Hang Yu [GenBank: COI = PP627110; 16S = PP572462; H3 = PP658046] . Paratypes: SIO-BIC E7290A (prepared for SEM), E7290C (prepared for SEM), E7290D (prepared for SEM), SIO-BIC E7290F, SIO-BIC E7289, MZUCR ECH2402, same collection data as holotype; SIO-BIC E4383, SIO-BIC E11442, on wood at Mound 12, Costa Rica, 8.9297 ° N, 84.3115 ° W, 990 m depth, February 24, 2009, HOV Alvin dive 4503, collectors Erik Cordes and Jen Gonzalez ; SIO-BIC E4549A (prepared for SEM), SMF 6939 (fixed glutaraldehyde-OsO 4, prepared for µCT), SIO-BIC E4549D (prepared for SEM), SIO-BIC E4549E, SIO-BIC E4549G, SIO-BIC E11221A, SIO-BIC E11221B, on wood at Mound 12, Costa Rica, 8.9306 ° N, 84.3124 ° W, 996 m depth, January 8, 2010, HOV Alvin dive 4587, collectors Victoria Orphan and Maria Teresa Aguado ; E7075A (prepared for SEM), E7075B (prepared for SEM), SIO-BIC E7075D, on wood at Mound 12, Costa Rica, 8.9325 ° N, 84.3074 ° W, 1002 m depth, June 5, 2017, HOV Alvin dive 4922, collectors Jen Le and Chris Roman. Other materials: SIO-BIC E4384 (fixed in Prefer), same collection data as SIO-BIC E4383; E7228 (specimen completely used up for DNA extraction; COI = PP627118), from bone and wood deployment at Mound 12, Costa Rica, 8.9300 ° N, 84.3117 ° W, 992 m depth, October 20, 2018, HOV Alvin dive 4974, collectors Lisa Levin and Kyle Metcalfe ; SIO-BIC E4403 (specimen completely used up for DNA extraction; COI = PP627104), substrate not recorded, at Jaco Scar , Costa Rica, 9.1262 ° N, 84.8384 ° W, 974–1856 m, exact depth not recorded, Mar 3, 2009, HOV Alvin dive 4509, collectors Elena Perez and Jake Bailey.

Description. Adult body stellate (Range of adult specimens: R = 2.88–6.85 mm, r = 2.33–4.65 mm, R/r = 1.21– 1.77; Holotype: R = 5.85 mm, r = 4.15 mm, R/r = 1.41, bent, so measurement may not be accurate). Thin epidermis covers abactinal surface. Epidermis thicker on actinal surface. Abactinal plates oval or irregularly polygonal with curved edges, wider than long, and imbricated so that distal edge of each plate is overlapped by proximal edge of one or more plates. Central disc plates more irregular in shape and sizes than arm plates and appear thick, causing abactinal surface to look uneven due to imbrication. Central disc plates imbricated more irregularly than arm plates. Five primary inter-radial plates (one bearing the madreporite) appear much larger than other abactinal plates and irregularly polygonal. Madreporite of holotype with multiple branching grooves ( Figs 5H , 10A ). A single row of dorsal-lateral plates on each side of a single row of carinal plates ( Figs 6E , 8A ) on each arm; rows of plates tend to become less discernible closer to the central disc. Some individuals have a second row of dorsal-lateral plates at arm base, which is more discernable in large specimens that have more plates. The row of carinal plates leads to a square-shaped terminal plate at tip of the arm with a central pore ( Figs 6E , 8A ). Each central disc plate bears around 12 or less abactinal armaments, sparsely distributed (~20/mm 2), short (0.08–0.2 mm) and spiniform. Abactinal spinelets consist of rounded, wide and robust base and stem with longitudinal ridges leading to a slightly expanded and thorny crown ( Fig. 8E, F ). Other abactinal plates bear spines of a similar shape. Each terminal plate has 4–5 elongated abactinal spines (0.1–2.5 mm), and 2–3 club shaped fringe spines (0.4–0.5 mm).

Along each side of the arm there are parallel rows of superomarginal plates and inferomarginal plates, more pentagonal than the abactinal plates. Each row has the same number of plates (adults 8–13; 9 in holotype) from interradius to arm tip, imbricating radially. Both rows uniform in shape except for proximal-most superomarginal plate. Each inferomarginal plate slightly more elongated and larger in size compared to adjoining superomarginal plate. First and/or second proximal-most superomarginal and inferomarginal plates are largest, size of plates decreases towards arm tip. Proximal-most superomarginal plate the most-oval shaped, wider than long. Marginal plates and other abactinal arm plates form a cohesive and convex abactinal surface. Gonopores conspicuous in interradius in holotype ( Fig. 5E ). Each of two gonopores on interradius in a notch associated with proximal-radial margin of proximal-most superomarginal plate, next to second proximal-most superomarginal plates ( Figs 6E , 8B ). Some gonopores appear slightly protruding, with narrow central slit, while others obscured by spines or epidermis and only visible with bleach treatment. Superomarginal plates and abactinal side of inferomarginal plates bear abactinal spines same as those on abactinal plates (superomarginal: 2–9 spinelets per plate, inferomarginal: 1–10 spinelets per plate) and similar density, but usually longer than those on central disc plates, especially those closer to margin (typical abactinal spines on superomarginal and inferomarginal plates = ~ 0.2 mm). On larger marginal plates, abactinal spines tend to arrange in two rows. Outer edge of each inferomarginal plate has 2 fringe spines. Fringe spines more elongated (0.44–0.49 mm) than abactinal spinelets and club-shaped, with tip wider than base, slightly compressed laterally ( Fig. 8G, H ). Lateral side of fringe spine wing-shaped ( Fig. 8H ), abactinal side with more thorns than actinal side.

Ambulacral furrows narrow and slightly petaloid. Tube feet 12–14 pairs. Ambulacral plates elongate, with both ends wider than middle segment ( Fig. 6D ). 12 pairs of adambulacral plates between furrow and inferomarginals of each arm. Proximal-most plate square-shaped; distal-most plate square to triangular-shaped, both small. Rest bar-shaped, oriented perpendicularly to furrow and length decreases distally, with the second proximal-most adambulacral plate largest and most elongate. Adambulacral spines arrange in one or two alternating rows and pointing towards body margin similar angle as adambulacral plates ( Fig. 8D ). Number of adambulacral spines on each plate vary with plate size. Proximal-most plate bears 1 adambulacral spine, while the number of adambulacral spines on the rest decreases distally with decrease in size, 5 at most. Adambulacral spines elongated (0.31–0.44 mm), thorny and robust ( Fig 8D, I, J ). Each tapers from wide base and numerous and small thorns tend to be obscured by the epidermis ( Fig. 8C ). The lateral side is smoother with few thorns. Each adambulacral plate has one furrow spine slightly pointing towards the ambulacral furrow. The oral side of inferomarginal plates also bears spines morphologically identical to adambulacral spines. The number of spines on the plate varies with plate size, with the largest, proximal-most plate bears 4 spines. Similar orientation as spines on adambulacral plates. Spines absent on plates near the arm tip. Oral opening large, around 2.85 mm wide. Stomach slightly everted. Paired oral plates at base of the interradius form a ridge in between. Each oral plate bears one suboral spine and 2 (sometimes 3) marginal spines pointing towards oral opening or furrow. Most pairs of oral plates at each interradius have the same number of spines, though sometimes one plate has 3 marginal spines while the other has 2. Spine shape and length are like adambulacral and furrow spines. Oral plates and proximal-most adambulacral plates delimit the boundary of the actinal chamber at the proximal part of the interradius, which contains two clusters of gonads separated by an inter-radial septum and covered by semi-transparent actinal membrane ( Figs 5G , 6B ).

Variation. Specimens of Caymanostella scrippscognaticausa sp. nov. vary greatly in size (see description), likely representing different life stages. There were 7 clearly juvenile specimens among the collected specimens (R = 0.93–1.86 mm; r = 0.82–1.53 mm; R/r = 1.11–1.27), among which the smallest two were used up for DNA extraction ( Table 1). Variations in several characters tend to correlate with ontogeny and body size. Smaller and less mature specimens are more pentagonal than stellate (adult average R/r = 1.40; juvenile average R/r = 1.20; Table 5), and early-stage juveniles are much thinner, almost transparent ( Fig. 9A–F ). Abactinal surfaces tend to be more convex in large specimens. Both epidermis and abactinal plates appear thicker in large specimens. This results in a more uneven surface of the abactinal side (e.g., compare Fig. 9G and 9K ). Under SEM the margin of the plates can be more obscured by the thicker epidermis ( Fig. 9N ) in comparison with juvenile specimens ( Fig. 9M ). Central disc plates arrange in more complex and less discernible cycles in large specimens due to greater number of plates, and orientation of plates and imbrication patterns can be more irregular ( Table 5). The row of carinal plates is more discernible in small specimens ( Fig. 7A, C ). Small specimens have madreporites in a single slit or pore (single slit Fig. 6A, C ; single pore Fig. 10D ; Table 5), and although single pore/single groove madreporites have also been found in some large individuals ( Fig. 10E, F ), more complex madreporites with branching grooves are only present in large specimens ( Fig. 10A–C, G ; Table 5). Abactinal spinelets of the smallest juveniles (R = <1 mm) are less dense and significantly shorter ( Table 5). While plates are not distinguishable in the smallest juveniles, terminal pores are visible at the abactinal side of each arm tip ( Fig. 9A, C ). The furrows are wide among the smallest juveniles and tube feet can be transparent in live specimens ( Fig. 9B ). Number of tube feet, disc plates, and adambulacral plates also increase with body size ( Table 5). Some other non-ontogenetic variations can be observed: in some specimens the furrow spines point vertically rather than pointing towards the furrow; actinal chambers range from triangular to heart shaped. Paratype SIO-BIC E7290F showed all oral plates with 3 marginal oral spines.

Distribution. Known only from the Pacific margin of Costa Rica, confirmed from 990–1010 m and possibly with a broader depth range.

Remarks. The stellate body shape and spiniform abactinal armament of Caymanostella scrippscognaticausa sp. nov. are like that of C. laguardai ( Table 6; Martin-Cao-Romero et al. 2021). However, the abactinal spinelet distribution of C. scrippscognaticausa sp. nov. appears sparser than that of C. laguardai , allowing the plates underneath to be exposed. Abactinal spinelets are similar in form to those of Caymanostella spinimarginata and C. cf. spinimarginata ( Table 6; Dilman et al. 2022), but the tips appear not as wide as those in C. cf. spinimarginata . The position of the gonopore is the most like that of C. spinimarginata ( Table 6; Dilman et al. 2022; Rowe 1989). Shapes and patterns of central disc plates are different from those in C. admiranda and C. madagascarensis ( Table 6). Detailed morphological comparisons are listed in Table 6. The maximum uncorrected intraspecific COI distance of C. scrippscognaticausa sp. nov. was 1.8% ( Table 3). There was a 6.4% divergence in uncorrected 16S between C. scrippscognaticausa sp. nov. and its well-supported sister taxon, C. laguardai ( Fig. 3 ; Table 4).

Identification of the sub-adult SMF 6938 was uncertain since many characters can change with ontogeny. It is provisionally identified as C. scrippscognaticausa sp. nov. due to its overall similarity to the juvenile paratype E7075B (which was sequenced), and the somewhat square-shaped terminal plate, yet there are no C. davidalani sp. nov. specimens of a similar size or life stage to provide a definitive comparison.

Etymology. Caymanostella scrippscognaticausa sp. nov. is named after the Scripps Family group “Cousins for Causes” for their kind donation to support research in this study.

Figures

FIGURE 3. Phylogenetic analyses. A—Maximum Likelihood analysis of mitochondrial COI of available Caymanostella sequences from GenBank, plus the newly generated sequences for this study. Sequences for Caymanostella scrippscognaticausa sp. nov. and C. davidalani sp. nov. holotypes are indicated by a *. Numbers on nodes represent ML bootstrap values. The three new species are highlighted in bold and color. B—Maximum Likelihood tree generated from concatenation of mitochondrial (COI and 16S) and nuclear (H3) genes. Numbers on nodes represent ML bootstrap values. The three new species are highlighted in bold and color. Sequences for Caymanostella scrippscognaticausa sp. nov. and C. davidalani sp. nov. are from the respective holotypes, except for the H3 sequence for C. davidalani sp. nov. which is from a paratype (SIO-BIC E7242). Sequences for C. loresae sp. nov. are from paratype USNM 1487403. Crinitostella is synonymized as Caymanostella (see Discussion).

FIGURE 5. Light Microscopy images of Caymanostella scrippscognaticausa sp. nov. Paratype SIO-BIC E7289: A—live abactinal view; B—live actinal view; F—close-up live abactinal view, with arrow indicating madreporite; G—close-up live actinal view. Holotype SIO-BIC E11441: C—preserved abactinal view, with arrow indicating madreporite; D—preserved actinal view; E—abactinal interradius, with arrows indicating gonopores; H—abactinal central disc showing madreporite. Abbreviations: a, anus; adp, adambulacral plates; ads, adambulacral spines; am, actinal membrane; fus, furrow spine; g, gonads; ip, inferomarginal plate; m, madreporite; mos, marginal oral spines; op, oral plate; sp, superomarginal plate; ss, suboral spines; t, tube feet.

FIGURE 6. Compiled micro-CT scans of a paratype (SMF 6939) of Caymanostella scrippscognaticausa sp. nov. A, C— abactinal view, with arrow indicating madreporite; B—actinal view; D—abactinal internal view; E—lateral view of abactinal interradius with arrows indicating gonopores; F—abactinal view with cross section and arrow indicating madreporite and stone canal; R = 4.2 mm; r = 3.45mm. Abbreviations: ads, adambulacral spines; am, actinal membrane; amb, ambulacral plate; cp, carinal plate; dlp, distal-lateral plate; fs, fringe spines; fus, furrow spines; g, gonads; ip, inferomarginal plate; op, oral plate; ads, adambulacral spines; sp, superomarginal plate; tp, terminal plate.

FIGURE 7. Compiled micro-CT scans of asub-adult specimen (SMF 6938), identifiedas Caymanostella scrippscognaticausa sp. nov.A, C—abactinal view; B—abactinal view; D—actinal view with transection; R = 1.77 mm; r = 1.5 mm.Abbreviations: ac, actinal chamber; cp, carinal plate; tp, terminal plate; ip, inferomarginal plate; op, oral plate; sp, superomarginal plate; t, tube feet.

FIGURE 8. Scanning Electron Microscopy (SEM) images of Caymanostella scrippscognaticausa sp. nov. A—detail of bleached abactinal arm tip (paratype SIO-BIC E7290A); B—detail of bleached abactinal interradius (paratype SIO-BIC E7290A); C—detail of adambulacral spinelets on actinal side (paratype SIO-BIC E7290C); D—detail of bleached adambulacral spinelets on actinal side (paratype SIO-BIC E7290A); E, F—abactinal spinelets (paratype SIO-BIC E7290A); G—fringe spine, H—lateral view of fringe spine (paratype SIO-BIC E7290A); I—adambulacral spine, J—lateral view of adambulacral spine (paratype SIO- BIC E7290C); Abbreviations: adp, adambulacral plate; ads, adambulacral spine; cp, carinal plate; dlp, distal-lateral plate; gp, gonopore; ip, inferomarginal plate; sp, superomarginal plate; tp, terminal plate.

FIGURE 9. Light Microscopy (LM) and Scanning Electron Microscopy (SEM) images of Caymanostella scrippscognaticausa sp. nov. specimens across ontogeny. Juvenile, SIO-BIC E7228 (destroyed for DNA extraction) (R = 0.93 mm, r = 0.84 mm, R/r = 1.11): A—live abactinal view, B—live actinal view, C—close-up of preserved abactinal arm tip, D—close-up of preserved abactinal central disc. Juvenile, SIO-BIC E4403 (destroyed for DNA extraction) (R = 0.95 mm, r = 0.82 mm, R/r = 1.16): E—live abactinal view. Juvenile, paratype SIO-BIC E7075B (R = 1.85 mm, r = 1.53 mm, R/r = 1.21): F—live abactinal view, M—SEM abactinal arm. Sub-adult, paratype SIO-BIC E11221B (R = 3.04 mm, r = 2.35 mm, R/r = 1.30): G—preserved abactinal view; H—preserved actinal view. Adult, paratype SIO-BIC E7290C (R = 5.88 mm, r = 3.75 mm, R/r = 1.57): I—preserved abactinal view; J—preserved actinal view. Adult, paratype SIO-BIC E7290F (R = 5.99 mm, r = 4.11 mm, R/r = 1.46): K—preserved abactinal view; L—preserved actinal view. Adult, paratype SIO- BIC E7290C (R = 5.88 mm, r = 3.75 mm, R/r = 1.57): N—SEM abactinal arm tip.

FIGURE 10. Light Microscopy (LM) and Scanning Electron Microscopy (SEM) images of madreporites among Caymanostella scrippscognaticausa sp. nov. specimens. A—holotype SIO-BIC E11441 (R = 5.85 mm, r = 4.15 mm, R/r = 1.41). B—paratype SIO-BIC E7290F (R = 5.99 mm, r = 4.11 mm, R/r = 1.46). C—paratype SIO-BIC E7289 (R = 6.85 mm, r = 4.65 mm, R/r=1.47). D—paratype SIO-BIC E7075B (R = 1.85 mm, r = 1.53 mm, R/r = 1.21). E—paratype SIO-BIC E7290C (R = 5.88 mm, r = 3.75 mm, R/r = 1.57). F—paratype SIO-BIC E7290A (R = 5.55 mm, r = 3.85 mm, R/r = 1.45). G—paratype SIO-BIC E7290D (R = 5.37 mm, r = 3.04 mm, R/r = 1.77, bent, measurement may not be accurate).