Ophioderma aija, Humara-Gil & Granja-Fernández & Bautista-Guerrero & Solís-Marín & Rodríguez-Troncoso, 2024

Humara-Gil, Karla J., Granja-Fernández, Rebeca, Bautista-Guerrero, Eric, Solís-Marín, Francisco A. & Rodríguez-Troncoso, Alma P., 2024, Delimitation of Ophioderma teres (Lyman, 1860) and Ophioderma unicolor H. L. Clark, 1940 stat. nov. (Echinodermata: Ophiuroidea), including the description of two new species, European Journal of Taxonomy 947, pp. 130-174 : 154-159

Ophioderma aija sp. nov.

urn:lsid:zoobank.org:act:E2101504-18BC-489E-B65E-CC334EF256D8

Figs 1–2 , 5 , 8–9 , 12B ; Tables 1–4

Ophioderma teres – Lyman 1860: 258 (partim, non Lyman, 1860); 1865: 38 (partim, non Lyman, 1860). — Steinbeck & Ricketts 1941: 391–392 (partim, non Lyman, 1860). — Caso 1951: 258–265, figs 21–24 (partim, non Lyman, 1860). — Ziesenhenne 1955: 190–191 (partim, non Lyman, 1860). — Granja-Fernández & López-Pérez 2011: 1321–1322 (non Lyman, 1860). — Granja-Fernández et al. 2014: 134–135 , fig. 6g –l (non Lyman, 1860).

Ophioderma teres var. unicolor – H.L. Clark 1940: 342 (partim, non H.L. Clark, 1940). — Downey 1969: 115 (partim, non H.L. Clark, 1940). — Granja-Fernández 2019: 277–279 (partim, non H.L. Clark, 1940). — Mireles-Velázquez et al. 2021: 317–319, fig. 2e–f (non H.L. Clark, 1940).

Ophioderma cf. teres unicolor – Humara-Gil et al. 2022: 367, 379–380, fig. 5 (partial DNA sequences of genes COI and 16S).

Ophioderma sp. – Granja-Fernández et al. 2022: 5, 9.

Ophioderma sp. A – This study: 3–12, Figs 1–2 , Tables 1–4 .

Diagnosis

Radial shields naked. Arms short (mean AL:DD = 2.7). DAPs divided into multiple pieces (mean = 3, maximum = 9). Coloration dark brown; dorsal and ventral disc with dark, sinuous rings; dorsal arms brown; ventral arms cream (preserved specimens) or yellow (in vivo specimens) proximally, darkening distally.

Etymology

The specific epithet aija combines the first two letters of the given names of Aida Janet Gil-Rabadán, mother of the first author. Born under a lucky star, she deserves her own on Earth.

Material examined

Holotype

MEXICO • spec. preserved in 70% ethanol; Oaxaca, La Mina ; 15°40.43′ N, 96°28.60′ W; May 2008; ICML-UNAM 18466 .

Paratypes

MEXICO – Oaxaca • 4 specs (preserved in 70% ethanol); Estacahuite ; 3.0– 12.2 m depth; 3 Mar. 2009; D. Arellanes-García and F. Benítez-Villalobos leg.; sand under dead coral and rocks; ICML-UNAM 18467 • 5 specs (preserved in 96% ethanol); Estacahuite ; 15°40′6′′ N, 96°28′52′′ W; 9 m depth; 20 Feb. 2020; R. Granja-Fernández leg.; rocks; ICML-UNAM 18468 • 2 specs (preserved dry); Tijera ; 15°41′15′′ N, 96°26′31′′ W; 10 m depth; 21 Feb. 2020; R. Granja-Fernández leg.; rocks; DNA voucher spec. labelled as “OJ5”; GenBank: OR789590 (COI), OR800000 (16S) ; ICML-UNAM 18469 .

Other material See Supp. file 1.

Description

Holotype

DD = 26.7 mm, AL = 78.9 mm, AL:DD = 3. Disc rounded, covered by rounded granules, slightly separated from each other. Granule size increasing from center to periphery. Dorsal disc granule density 60 per mm 2. Radial shields naked; visible section approximately 1.5× as long as wide, oval; distance between shields about 4× width of shield ( Fig. 8A ). Ventral interradii covered with granules of uniform size, slightly separated from each other. Four genital slits per interradius. Proximal genital slits oval, separated from distal section of oral shields by two rows of granules, but in contact with 1 st LAP; reaching up to proximal section of 2 nd VAP. Distal genital slits oval, 1.5× as long as proximal ones, placed between 7 th and 9 th arm segments; surrounded by granule-bearing scales and naked scales next to the arm ( Fig. 8B ).

Oral shields 1.6× as wide as long, rounded triangular; proximal edge convex forming a rounded apex; lateral edges rounded; distal edge straight. Madreporite rounded trapezoidal, with a central depression deviated towards distal section; distal edge convex. Adoral shields covered by small granules. Jaws with 8–9 oral papillae: LyOs 3.5× as long as wide, angled upwards; AdShSp the largest, trapezoidal; 2°AdShSp smaller than AdShSp, rounded rectangular; LOPas 3–5, rounded rectangular to conical; IPa similar to LOPas, larger; TPa two at jaw apex, triangular to rectangular, robust. Teeth 4–5: vT triangular, slightly flattened; median and dorsalmost teeth quadrangular. One OPRSp on each side of the jaw, conspicuous. Oral plates covered with granules larger than those covering adoral shields, decreasing in size towards periphery ( Fig. 8C ).

Five arms rounded, tapering distally: all incomplete, three regenerating, the remainder without the distalmost segments ( Fig. 8K ). Dorsal arm base with multiple scales extending to 1–2 arm segments ( Fig. 8D ). DAPs wider than long, typically divided into two and up to five irregular pieces ( Fig. 8D–E ). DAP pieces sequence of the longest arm: first ten segments, 3, 3, 4, 5, 5, 5, 4, 4, 5, 5; 11 th –20 th, 3–4; 21 st –30 th, 2–4; 31 st –40 th, 2–5; 41 st –50 th, 1–3; 51 st –60 th, 1–2; 61 st –70 th, 1–2; 71 st –74 th, 1. Distalmost DAPs trapezoidal to triangular, entire ( Fig. 8F ). First VAP small, 2× as wide as long, with rounded edges ( Fig. 8B ). Subsequent VAPs quadrangular, longer than wide; proximal edge straight, distal edge convex ( Fig. 8G–H ). Distalmost VAPs triangular, rounded, wider than long ( Fig. 8I ). A pair of pores between the two proximalmost VAPs in all five arms ( Fig. 8B ). LAPs conspicuous, wider than long, with up to ten arm spines. Arm spine sequence of the longest arm (right side, including arm spine bearing segments within the disc): first ten segments, 3, 3, 3, 4, 5, 5, 6, 7, 8, 9; 11 th –20 th, 9–10; 21 st –30 th, 9–10; 31 st –40 th, 8–9; 41 st –50 th, 8; 51 st –60 th, 6–8; 61 st –70 th, 6–7; 71 st –80 th, 4–6; 81 st –83 rd, 4. Arm spines conical with blunt tips, slightly flattened, ⅔ LAP length. Dorsalmost arm spine the shortest; ventralmost the longest and more robust, in contact with tentacle scales of the following segment ( Fig. 8J ). Two tentacle scales; adradial tentacle scale oval, elongated, just over ⅔ VAP length; abradial tentacle scale shorter and wider, ¾ adradial scale length, triangular ( Fig. 8G–H ). In the distalmost arm section, tentacle scales oval and elongated, adradial being the longest; last arm segments with only one scale ( Fig. 8I ).

General coloration dark brown (specimen in ethanol) ( Fig. 8K ). Dorsal side: disc dark brown with darker, sinuous rings; these may or may not continue over radial shields. Radial shields lighter brown ( Fig. 8A ). Arms brown, lighter than disc ( Fig. 8D–F, K ). Ventral side: interradii lighter than dorsal disc, with dark, sinuous rings ( Fig. 8B ). Oral shields light brown, two with small, darker specks; oral papillae, teeth, and arms cream ( Fig. 8B–C ). Ventral arms darkening towards the distalmost arm section. LAPs light brown. Arm spines light brown; the ventralmost the lighter ( Fig. 8J ).

Disarticulated ossicles

Non-type specimen, ICML-UNAM 18457 (DD = 26.2 mm, AL = 81.9 mm, AL:DD = 3.1). Radial shields irregularly triangular, naked in the intact animal; proximal edge convex; distal edge unequally convex; adradial edge irregular, slightly convex in the middle; abradial edge with two well-defined processes, distal prominent ( Fig. 9A–B ). Externally, distal half swollen, with a raised oval in the center corresponding to the naked section in the intact animal; oval surface surrounded by numerous small pores; scattered larger pores placed near edges and proximal section ( Fig. 9A ). Internally, distal half center with three median pores; close to distal edge, two rounded truncated bulbs slightly separated, adradial one larger, followed by a furrow ( Fig. 9B ). Dental plate fragmented into several pieces (up to five), bearing one or two teeth in oval or round non-penetrating sockets; ventralmost piece also with round sockets for TPa ( Fig. 9C ). Adradial genital plate falcate, elongated. Abradial face slightly depressed in the middle, longitudinally, with three pores close to distal edge; distal edge with two truncated knobs and a distal depression, noticed from the other side ( Fig. 9D ). Adradial face with a longitudinal groove and a notorious pore close to distal section. Distal edge rounded, with a lateral depression followed by a knob ( Fig. 9E ). Oral plates longer than high, middle section slightly lower than ends ( Fig. 9F–G ); abradial face with muscle fossa irregularly oval, elongated ( Fig. 9F ); adradial face with multiple pores at proximoventral edge of plate corresponding to oral papillae (lateral) and granules (ventral) sockets ( Fig. 9G ). Vertebrae zygospondylus ( Fig. 9H–I ). Proximal vertebrae wider than long, with dorsal muscle fossae larger than ventral ones ( Fig. 9H ). VAPs (from proximal arm section) quadrangular, longer than wide; proximal edge with three points, the median one corresponding to a spur; lateral edges with two points forming concave areas; distal edge convex ( Fig. 9J ). Internal face with three spurs, two elongated and lateral, and one smaller, oval in the middle ( Fig. 9K ). LAPs curved, 2× as high as wide; dorsal edge straight; ventral edge convex, with a small, rounded condyle developing from internal side; proximal edge concave; distal edge convex ( Fig. 9L–N ). Proximal external LAP edge with two conspicuous, elongated, and triangular spurs in the middle ( Fig. 9L ), having their counterparts internally ( Fig. 9M ). Internal side with four pores near center, concave proximal ridge, two separated bulbs near ventral edge, ventralmost protruding from plate. Ten spine articulations on distal edge, each surrounded by a thick lobe ( Fig. 9N ).

Paratype and non-type variations

Paratypes varied in size from 3.6 to 23.7 mm (DD). The two smallest specimens (DD = 3.6 and 4.8 mm) showed radial shields, jaws (including oral shields), DAPs, VAPs, and LAPs covered with granules, as well as the arm base and the section between the arm and distal genital slit. The arm spines in these specimens were up to five, short and pointed. Larger specimens (DD = 9.4–23.7 mm) resembled more the holotype, as they had naked radial shields, oral shields and arms without granules, and scales on the arm base and distal genital slit. These presented exposed DAPs, divided into a maximum of three pieces in the smallest specimen (DD = 9.4 mm) and seven in larger ones (DD> 22.4 mm), varying according to size. The maximum number of arm spines also varied with size, ranging from seven (DD = 9.4 mm) to nine (DD = 17.2–23.7 mm). As for coloration, all paratypes exhibited dark, sinuous rings on the disc. The number and color intensity of these rings varied within (dorsal/ventral sides) and between specimens. The smallest specimens showed the faintest rings, which were quite susceptible to fading with preservation. Paratypes presented light brown, dark brown, or cream-colored oral shields with a brown center. On the ventral side, the interradii were as dark as the disc or light, darkening towards the disc edge.

Other variations were observed in non-type specimens (DD = 6.0– 26.4 mm). As in the paratypes, the smallest specimens (DD <8.5 mm) had radial shields covered with granules; however, two large specimens (DD = 18.8 and 23.6 mm) also presented covered radial shields. Four specimens (DD = 10.6– 19.0 mm) had one to several small, rounded plates on the disc. A few specimens showed trilobed, rather than rounded triangular, oral shields. Specimens with DD from 5.6 mm began to show some uncovered DAPs in the proximal and median arm sections, mostly entire or divided into up to two pieces, while their VAPs, LAPs, and oral shields remained covered. On the other hand, those with DD from 7.7 mm had all their DAPs, VAPs, LAPs, and oral shields without granules. In terms of coloration, one specimen presented a uniform light brown ventral side, and another had a general cream coloration with dark, sinuous rings on the dorsal disc.

Distribution and habitat

Ophioderma aija sp. nov. has been collected in Mexico in the Gulf of California (Sonora, Baja California Sur), Jalisco, Colima, Michoacán, Guerrero, and Oaxaca, as well as in Nicaragua, in Cardon Island (see Supp. file 1). Its northernmost record is from Guaymas, Sonora, Mexico (27° N), and the southernmost from Cardon Island, Corinto, Nicaragua (12° N) ( Fig. 5 ). The species may also occur in Ecuador (Galapagos Islands and La Plata), according to Ziesenhenne (1955: 191). Revising material from these areas would help to confirm this. Ophioderma aija is found typically on rocks, but also on shingle, sand, and live and dead coral, from the intertidal zone to 27 m depth.

Remarks

Despite being recorded since 1860 ( Lyman 1860), O. aija sp. nov. remained undescribed due to its misidentification as either O. teres or O. unicolor stat. nov. Confusion with O. teres arose from the original description of this species, where Lyman (1860: 258) included a specimen of O. aija (DD = 14 mm) as additional material, describing its characteristic color pattern: “…very dark umber, with fine, sinuous, black lines on the disc”. Since then, O. aija has been recorded as O. teres by other authors (e.g., Lyman 1865; Steinbeck & Ricketts 1941; Caso 1951; Granja-Fernández & López-Pérez 2011), occasionally attributing their morphological differences to distribution, habitat ( Ziesenhenne 1955), or a juvenile life stage ( Granja-Fernández et al. 2014). On the other hand, the misidentification as O. unicolor started due to a mixture of one specimen of O. aija in the type series of O. unicolor (H.L. Clark 1940; Downey 1969). Revision of the former paratype (MCZ IZ OPH-167471) led some authors to identify O. aija as O. teres var. unicolor ( Granja-Fernández 2019; Mireles-Velázquez et al. 2021) or O. cf. teres unicolor ( Humara-Gil et al. 2022) . In this work, the comprehensive revision of the type series of O. unicolor resulted in the reclassification of the specimen of O. aija as a distinct species.

Ophioderma aija sp. nov. shares with O. teres and O. unicolor stat. nov. the covered adoral shields and divided DAPs. However, they differ as follows: 1) radial shields typically naked in O. aija and O. unicolor versus radial shields either covered or naked in O. teres ; 2) shorter arms in O. aija (mean AL:DD = 2.7) than in O. teres (mean AL:DD = 4.1) and O. unicolor (mean AL:DD = 3.6); 3) DAPs divided into more pieces in O. aija (mean = 3, maximum = 9) and O. teres (mean = 3, maximum = 13) than in O. unicolor (mean = 2, maximum = 6), and 4) color pattern with dark, sinuous rings in the disc in O. aija , rounded cream specks in the disc and arms in O. teres , and uniform brown disc and arms in O. unicolor .

As mentioned previously, one of the most distinctive characters of O. aija sp. nov. is its color pattern. Although the rings remain visible in preserved specimens as old as 163 years (MZC IZ OPH-112), they may fade due to fixation. It is advisable to photograph or label specimens appropriately in the field to avoid confusion with other similar species in case the rings fade. This is particularly important for juvenile specimens whose other diagnostic characters may not be developed.

Figures

Fig. 1. Bayesian inference (BI) tree of COI sequences. Numbers on branches indicate posterior probability/bootstrap values obtained with BI and maximum likelihood (ML), respectively. A dash (–) indicates the branches not recovered in the ML analysis. Sequences obtained in this study are indicated in bold (see Supp. file 5).

Fig. 2. Bayesian inference (BI) tree of 16Ssequences. Numberson branches indicate posterior probability/ bootstrap values obtained with BI and maximum likelihood, respectively. Sequences obtained in this study are indicated in bold (see Supp. file 5).

Fig. 5. Distribution of Ophioderma teres (Lyman, 1860), Ophioderma unicolor H.L. Clark, 1940 stat. nov., Ophioderma aija sp. nov., and Ophioderma bichi sp. nov. in the eastern Pacific. A. Gulf of California. B. Revillagigedo Islands. C. Mexican Tropical Pacific. D. Central America and Colombia. E. Galapagos Islands.

Fig. 8. Ophioderma aija sp. nov., holotype (ICML-UNAM 18466, DD = 26.7 mm). A. Dorsal disc. B. Ventral disc (inset: section between the arm and the distal genital slit). C. Close-up of a jaw. D. Proximalmost dorsal arm. E. Median dorsal arm. F. Distalmost dorsal arm. G. Proximalmost ventral arm. H. Median ventral arm. I. Distalmost ventral arm. J. Lateral arm plates and arm spines. K. Dorsal view. Abbreviations: 2° AdShSp = secondary adoral shield spine; AdShSp = adoral shield spine; IPa = infradental papilla; LOPas = lateral oral papillae; LyOs = Lyman’s ossicle; OPRSp = oral plate ridge spine; RS = radial shield; TPa = tooth papilla; vT = ventralmost tooth.

Fig. 9. Ophioderma aija sp. nov., non-type specimen (ICML-UNAM 18457, DD = 26.2 mm), SEM images of the ossicles. A. Radial shield, external face. The arrowhead indicates the naked section observed in the intact animal. B. Radial shield, internal face. C. Dental plate. D. Adradial genital plate, abradial face. E. Adradial genital plate, adradial face. F. Oral plate, abradial face. G. Oral plate, adradial face. Black arrows point to oral papillae sockets, white arrows point to granule sockets. H. Arm vertebra, proximal face. I. Arm vertebra, distal face. J. Ventral arm plate, external face. K. Ventral arm plate, internal face. L. Lateral arm plate, external face. M. Lateral arm plate, internal face. N. Lateral arm plate, lateral face. Abbreviations: dist = distal; dors = dorsal; prox = proximal; SA = spine articulation; Sp = spur; vent = ventral.

Fig. 12. Photographs of the species in situ. A. Ophioderma teres (Lyman, 1860) (Bajo Rojo, Costa Rica) (photograph: Steven Lara-Angulo). B. Ophioderma aija sp. nov. (Estacahuite, Mexico) (photograph: Francisco Benítez-Villalobos). C. Ophioderma bichi sp. nov. (Puerto Peñasco, Mexico) (photograph: Paloma Valdivia).