Ophioderma teres ( Lyman, 1860 )

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 : 141-148

Ophioderma teres ( Lyman, 1860)

Figs 1 , 3–6 , 12A ; Tables 1–4

Ophiura teres Lyman, 1860: 198–200 , 257–258 (partim).

Ophioderma sodipallaresi Caso, 1986: 223–248 , figs 1–13, syn. nov.

Ophiura teres – Lyman 1865: 37–38, fig. 1 (partim).

Ophioderma teres – Ljungman 1867: 304 (comb. nov.). — Nielsen 1932: 332–334, fig. 37. — H.L. Clark 1940: 342. — Ziesenhenne 1955: 189–190 (partim). — Granja-Fernández 2019: 273–275, fig. 37a–f (partim). — Humara-Gil et al. 2022: 373, fig. 4j, table 1.

Ophioderma sodipallaresi – Alvarado et al. 2017: 278. — Granja-Fernández 2019: 270–273, fig. 36g –l. — Humara-Gil et al. 2022: 373, fig. 4g –i, table 1.

Diagnosis

DAPs divided into multiple pieces (mean = 3, maximum = 13). Coloration light brown to brown; disc and dorsal arms with conspicuous rounded cream specks; ventral arms cream proximally, darkening distally (preserved specimens).

Material examined

Neotype (here designated)

PANAMA • dry preserved specimen; Pearl Islands; 1875; MCZ IZ OPH-113 .

Holotype of Ophioderma sodipallaresi

MEXICO • dry preserved specimen; Sinaloa, Mazatlán, northwest of Pájaros Island ; 23°15′39′′ N, 106°28′37′′ W; 9 m depth; 24 Jan. 1983; M.E. Caso, J. Torres Vega, O. López, J. Álvarez, F. Flores, Quijano and Osuna leg.; sandy-rocky substrate; ICML-UNAM 3.24.3 .

Paratypes of Ophioderma sodipallaresi

MEXICO – Sinaloa • 1 spec. (preserved dry); Mazatlán, in front of Lobos Island ; 23°10′32′′ N, 106°27′55′′ W; 12 m depth; 4 Sep. 1979; M.E. Caso, J. Torres Vega, F. Flores, J.A. Gamboa, J. Álvarez, G. Díaz and Orozco leg.; rocky-sandy substrate; ICML-UNAM 3.24.0 • 2 specs (preserved dry); Mazatlán, inlet between Lobos Island and Venados Island ; 23°13′44′′ N, 106°27′56′′ W; 10 m depth; 6 Sep. 1979; M.E. Caso, J. Torres Vega, F. Flores, J.A. Gamboa, J. Álvarez, G. Díaz and Orozco leg.; sandy-rocky substrate; ICML-UNAM 3.24.1 • 1 spec. (preserved dry); Mazatlán, north of Pájaros Island ; 23°15′40′′ N, 106°28′39′′ W; 4–5 m depth; 18 Mar. 1982; M.E. Caso, J. Torres Vega, O. López, F. Gónzalez and F. leg.; rocky-sandy substrate; ICML-UNAM 3.24.2 • 1 spec. (preserved dry); Mazatlán, northwest of Pájaros Island ; 23°15′39′′ N, 106°28′37′′ W; 9 m depth; 24 Jan. 1983; M.E. Caso, J. Torres Vega, O. López, J. Álvarez, F. Flores, Quijano and Osuna leg.; sandy-rocky substrate; ICML-UNAM 3.24.4 .

Other material See Supp. file 1.

Designation of neotype

As one of the most emblematic Ophioderma from the EP ( Solís-Marín et al. 2013), the identity of O. teres was considered clear for years. However, recent attempts to study the species revealed that: 1) its type material was missing, and 2) it had been mistaken for similar undescribed species in different scientific collections ( Humara-Gil et al. 2022; RGF, KJHG pers. obs.). In view of these problems, the designation of a neotype for O. teres became necessary to redefine it and clarify its taxonomic status ( ICZN 1999, Arts 75.1, 75.3.1).

The holotype of O. teres was searched for in the USNM, where it was originally deposited ( Lyman 1860), but could not be found. The search for the material in other collections worldwide (i.e., American Museum of Natural History, New York, USA; LACM; MCZ; Museum national d’Histoire naturelle, Paris, France; Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark; UMML; Yale Peabody Museum of Natural History, New Haven, USA) was also unsuccessful. Hence, it was presumed lost or destroyed ( ICZN 1999, Art. 75.3.4). The work of Downey (1969) implies that the holotype of O. teres might have been lost long ago, as it was not listed in her catalog of Ophiuroidea types despite having included all the USNM material. This indicates that the whereabouts of this material have been unknown since at least 1969.

A neotype for O. teres is proposed herein and is comprehensively described and illustrated in accordance with the International Code of Zoological Nomenclature ( ICZN) ( ICZN 1999, Arts 75.3.2–75.3.3). The selected specimen accords with the original description of the species by Lyman (1860), as well as with other specimens identified by him as O. teres ( MCZ IZ OPH- 112, MCZ IZ OPH- 115, MCZ IZ OPH-230) ( ICZN 1999, Art. 75.3.5). The neotype was collected in Panama like the original holotype ( Lyman 1860; ICZN 1999, Art. 75.3.6), specifically in the Pearl Islands. The latter becomes the new type locality for the species ( ICZN 1999, Art. 76.3). The neotype is deposited in the MCZ ( ICZN 1999, Art. 75.3.7).

Description

Neotype

DD = 26.5 mm, AL = 110.1 mm, AL:DD = 4.1. Disc pentagonal, covered by minute rounded granules, slightly separated from each other. Granule size varies randomly along disc. Granules rubbed off in some areas, exposing scales underneath. Dorsal disc granule density 70 per mm 2. Radial shields covered by granules ( Fig. 3A ). Small, rounded to oval plates of variable size (2–4) close to arm base ( Fig. 3A, D ). Ventral interradii covered with granules increasing in size the closer they are to disc distal section. Four genital slits per interradius. Proximal genital slits oval, slightly 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, longer than proximal ones, placed between 4 th and 6 th arm segments; surrounded by granule-bearing scales and a few naked scales next to the arm ( Fig. 3B ).

Oral shields 1.6× as wide as long, rounded triangular; proximal edge convex forming a rounded apex; lateral edges rounded; distal edge straight. Madreporite oval, with a central depression slightly deviated towards distal section; distal edge convex. Adoral shields covered by small granules, closely grouped. Jaws with 9–11 oral papillae: LyOs 2× as long as wide, angled upwards; AdShSp the largest, triangular with rounded edges; 2°AdShSp similar in shape to AdShSp, but smaller; LOPas 4–6, rectangular to conical, pointed; IPa similar to LOPas; TPa two at jaw apex, elongated, robust. Teeth five: vT triangular with rounded edges, slightly flattened; median teeth quadrangular; dorsalmost triangular and pointed. One OPRSp at each side of the jaw, conspicuous. Oral plates covered with granules larger than those close to the margin of oral shields ( Fig. 3C ).

Five arms rounded, tapering distally: all without distalmost segments ( Fig. 3K ). Dorsal arm base with some small scales and few granules scattered between them ( Fig. 3D ). DAPs wider than long, typically divided into four and up to seven irregular pieces ( Fig. 3D–E ). DAP pieces sequence of the longest arm: first ten segments, 5, 5, 4, 4, 4, 4, 4, 5, 4, 5; 11 th –20 th, 4–6; 21 st –30 th, 3–5; 31 st –40 th, 3–5; 41 st –50 th, 2–5; 51 st –60 th, 2–3; 61 st –70 th, 1–4; 71 st –80 th, 1–2; 81 st –89 th, 1. Distalmost DAPs trapezoidal to triangular, entire ( Fig. 3F ). First VAP small, 1.8 × as wide as long, with rounded edges ( Fig. 3B ). Subsequent VAPs quadrangular, longer than wide proximally to wider than long in the median arm section ( Fig. 3G– H ); distal edge convex in proximal VAPs ( Fig. 3G ), slightly concave in median VAPs ( Fig. 3H ), and convex in distal VAPs ( Fig. 3I ). Distalmost VAPs triangular with rounded edges, slightly longer than wide ( Fig. 3I ). A pair of pores between the 2–3 proximalmost VAPs in all five arms ( Fig. 3B ). LAPs conspicuous, wider than long, with up to 11 arm spines. Arm spine sequence of the longest arm (right side, including arm spine bearing segments within disc): first ten segments, 3, 3, 4, 4, 5, 6, 6, 8, 9, 9; 11 th – 20 th, 9–10; 21 st –30 th, 9–10; 31 st –40 th, 8–9; 41 st –50 th, 7–10; 51 st –60 th, 8; 61 st –70 th, 7–8; 71 st –80 th, 6–7; 81 st – 90 th, 5–6; 81 st –90 th, 4–5. Arm spines conical with blunt tips, flattened, ⅔ LAP length. Dorsalmost arm spine the shortest; ventralmost the longest and more robust, covering approximately ⅓ of the following segment adradial tentacle scale ( Fig. 3J ). Two tentacle scales, rarely three; adradial tentacle scale oval, elongated, just over ½ VAP length; abradial tentacle scale shorter and wider, ¾ adradial scale length, triangular ( Fig. 3G–H ). In the distalmost arm section, tentacle scales oval and elongated, adradial being the longest; last arm segments with only one scale ( Fig. 3I ).

General coloration light brown with lighter cream specks (dry specimen) ( Fig. 3K ). Dorsal side: disc light brown, with subtle clusters of lighter granules ( Fig. 3A ). Arms light brown with rounded cream specks not following a definite pattern ( Fig. 3D–E, K ). Ventral side: interradii light brown with clusters of cream granules, giving a non-uniform speckled appearance ( Fig. 3B ). Oral shields light brown; oral papillae, teeth, and arms cream ( Fig. 3B–C ). LAPs light brown, some with light specks as those on DAPs. Arm spines beige to light brown; the ventralmost the lighter ( Fig. 3J ).

Disarticulated ossicles

Non-type specimen, USNM E23201 (DD = 26.9 mm, AL = 83.2 mm, AL:DD = 3.1). Radial shields irregularly triangular, covered in the intact animal; proximal edge convex; distal edge convex; adradial edge irregular with a median process; abradial edge with two processes, distal prominent ( Fig. 4A–B ). Externally, distal half swollen, with scattered small pores in the center; proximalmost and lateral edges with larger pores ( Fig. 4A ). Internally, distal half center with three median pores; close to distal edge, two rounded bulbs slightly separated, adradial one larger, followed by a furrow ( Fig. 4B ). Dental plate fragmented into several pieces (up to six), each supporting one or two teeth in oval or round non-penetrating sockets ( Fig. 4C ). Adradial genital plate falcate, elongated, widening distally, with a longitudinal groove and a large pore close to distal section. Distal edge rounded, with a lateral protuberance ( Fig. 4D ). Oral plates longer than high, fragmented during disarticulation ( Fig. 4E–F ); abradial muscle fossa irregularly triangular, widening ventrally ( Fig. 4E ). Vertebrae zygospondylus ( Fig. 4G–H ). Proximal vertebrae wider than long, with dorsal muscle fossae larger than ventral ones ( Fig. 4G ). VAPs (from proximal arm section) quadrangular, slightly longer than wide; proximal edge with three points, the median and larger one corresponding to a spur; lateral edges with two points forming concave areas; distal edge concave ( Fig. 4I ). Internal face with three spurs, two elongated and lateral, and one middle smaller and rounded ( Fig. 4J ). LAPs curved, 2× as high as wide; dorsal edge straight; ventral edge slightly convex, with a small, rounded condyle developing from internal side; proximal edge concave; distal edge convex ( Fig. 4K–M ). Proximal external edge with two elongated, conspicuous spurs in the middle ( Fig. 4K ), having their counterparts internally ( Fig. 4L ). Internal side with four pores near center, concave proximal ridge, and two separated bulbs near ventral edge, the ventralmost protruding from plate. Ten spine articulations on distal edge, each surrounded by a thick lobe ( Fig. 4M ).

Non-type variations

Non-type specimens varied in size from 11.6 to 33.8 mm (DD). Fourteen specimens (DD = 11.8– 33.8 mm), including two larger than the neotype (DD = 26.7 and 33.8 mm), showed naked radial shields, oval (rarely rounded) and 1.5 × as long as wide. One specimen (DD = 19.2 mm) had nine partially visible radial shields. One of the largest specimen (DD = 32.9 mm) presented noticeable covered radial shields sunken into the disc. All the examined specimens with DD <20 mm lacked plates on their discs, while 12 larger ones (DD = 20.1–32.9 mm) had between one and four small, rounded plates near the arm base, like the neotype. Three specimens (DD = 11.6, 13.7, and 17.4 mm) only had granule-bearing scales in the section between the arm and the distal genital slit, instead of naked and granule-bearing scales like the remaining specimens. Nine specimens showed trilobed rather than rounded triangular oral shields. Eight specimens (DD = 16.5–33.5 mm) exhibited a few granules between the edges of 2–7 proximalmost DAPs. All specimens presented DAPs divided into multiple pieces; the smaller the specimen, the less fragmented the DAPs were. The smallest specimen (DD = 11.6 mm) had the highest number of entire DAPs, with only a few divided into two pieces; in the largest (DD = 33.8 mm), the mean number of DAP pieces increased to five pieces with a maximum of nine. The maximum number of arm spines also varied with size, ranging from seven (DD = 11.8 and 13.0 mm) to 12 (DD = 29.1, 32.6, and 33.5 mm). Two specimens (DD = 17.5 and 32.9 mm) presented a few segments with three tentacle scales; the remaining specimens showed two tentacle scales on each segment.

The remaining variations were observed in coloration. Five specimens displayed a brown center on their dorsal disc, with the cream specks limited to the disc periphery. One specimen had some groups of brown granules resembling brown specks, in addition to the usual cream-colored ones. In three specimens, the radial shields were completely brown, and in another they had a single central cream-colored speck. Eighteen specimens showed brown oral shields with cream specks (comparable to those observed on DAPs and radial shields); another presented cream-colored oral shields with a brown center. In four specimens, the ventral arms darkened distally. These differences likely resulted from preservation.

Distribution and habitat

Ophioderma teres was presumed to be widely distributed in the EP, from the southwestern USA to Peru ( Maluf 1988; Granja-Fernández & Hooker 2020), but its distribution appears more restricted. In Mexico, the species was collected in Sinaloa and Guerrero; in El Salvador, in Maculís; in Costa Rica, in Port Parker (now Bahía de Santa Elena), Parque Nacional Marino Ballena, and Golfo Dulce; in Panama, in the Gulf of Chiriquí, Gulf of Panama, and the Pearl Islands, and in Colombia, in Port Utria (see Supp. file 1). Its northernmost record corresponds to Pájaros Island, Sinaloa, Mexico (23° N; as O. sodipallaresi , see Remarks), and the southernmost to Port Utria, Colombia (5° N) ( Fig. 5 ).

Records of O. teres in previous studies should be carefully evaluated using voucher material to verify or refute its presence at the reported locations. For example, in Mexico the species had been reported in Baja California, Baja California Sur, Nayarit, Jalisco, and Oaxaca ( Honey-Escandón et al. 2008; Granja-Fernández et al. 2015). However, these records are now considered invalid as they pertain to O. occultum or the two newly described species below ( O. aija sp. nov., O. bichi sp. nov.). Although the species has also been reported in the USA, Nicaragua, Ecuador, and Peru ( Solís-Marín et al. 2013), no material from these countries belonging to O. teres was found in the collections visited. Based on the data available from the revised specimens, O. teres inhabits tide pools, sandy mud, sandy spits, and rocks, and can be found at depths of up to 10 m.

Remarks

Once considered quite variable in morphology and widespread in the EP, O. teres is now recognized to have been consistently confused with different known and new species ( Lyman 1860, 1865; Nielsen 1932; H.L. Clark 1940; Ziesenhenne 1955; Granja-Fernández 2019).

One of the species with the most striking resemblance to O. teres is O. sodipallaresi . Both have covered or naked radial shields ( Fig. 6A–B ), covered adoral shields ( Fig. 6C–D ), divided DAPs ( Fig. 6G–J ), and the characteristic cream-colored specks on their discs and arms ( Fig. 6 ). However, they differ in size ( O. sodipallaresi ; DD up to 20.9 mm; O. teres : DD up to 33.8 mm), distal genital slit ornamentation ( O. sodipallaresi : granule-bearing scales ( Fig. 6E ); O. teres : naked and granule-bearing scales ( Fig. 6F )), number of pieces of their divided DAPs ( O. sodipallaresi : mean = 2, maximum = 5; O. teres : mean = 3, maximum = 13), and maximum number of arm spines ( O. sodipallaresi : 10; O. teres : 12). The last three characters are known to vary in Ophioderma according to the size, though ( Granja-Fernández et al. 2020; Stöhr et al. 2020; Humara-Gil et al. 2022). Specimens of O. teres close in size (DD = 11.6–21.6 mm) ( Fig. 6B, D, F, I–J ) to the type series of O. sodipallaresi (DD = 9.9–20.9 mm) ( Fig. 6A, C, E, G–H ) had similar counts of DAPs pieces and arm spines, with the smallest one having only granules on its distal genital slit. Considering the above, O. sodipallaresi is herein regarded as a junior synonym of O. teres . Caso (1986) may have overlooked the similarities between her then new species, O. sodipallaresi , and O. teres because she had been identifying other species ( O. aija sp. nov., O. bichi sp. nov.) as the latter ( Caso 1951; RGF, KJHG pers. obs.) and had not examined specimens of O. teres sensu stricto before.

It is worth noting that the specimens described by Caso (1986) from Sinaloa as O. sodipallaresi , and two specimens from Acapulco (MCZ IZ OPH-112), were the only material of O. teres from Mexico in the collections visited. Despite the ongoing collection of ophiuroids along the Mexican Pacific coast for the past ~13 years (RGF pers. obs.), the species has not been found again in the region. This contrasts with what has been observed in other countries, such as Costa Rica, where the species appears to be conspicuous and abundant (Chacón-Monge 2019 pers. com.).

Ophioderma teres most resembles O. peruanum , with which it shares the covered or naked radial shields, covered adoral shields, distal genital slit ornamentation, divided DAPs, and color pattern. On the other hand, they differ in the size and density of the disc granules ( O. teres : scattered, of different sizes along the disc; O. peruanum : closely packed, of uniform size), extent of granules on the arms ( O. teres : limited to the arm base; O. peruanum : on the distal part of the proximalmost and median DAPs), and geographic distribution ( O. teres : from Mexico to Panama; O. peruanum : only known from Peru) ( Pineda-Enríquez et al. 2013). Despite the previous findings, the taxonomic status of O. peruanum remains unclear due to the limited number of specimens examined (n = 4). It is uncertain whether this species is distinct from O. teres or represents its southernmost record instead. Additional research incorporating morphological and molecular data is needed to elucidate the taxonomic status of O. peruanum .

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. 3. Ophioderma teres (Lyman, 1860), neotype (MCZ IZ OPH-113, DD = 26.5 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.Arrowheads indicate the extra plates on the arm base.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; TPa = tooth papilla; vT = ventralmost tooth.

Fig. 4. Ophioderma teres (Lyman, 1860), non-type specimen (USNM E23201, DD = 26.9 mm), SEM images of the ossicles. A. Radial shield, external face. B. Radial shield, internal face. C. Dental plate. D. Adradial genital plate, adradial face. E. Oral plate, abradial face. F. Oral plate, adradial face. G. Arm vertebra, proximal face. H. Arm vertebra, distal face. I. Ventral arm plate, external face. J. Ventral arm plate, internal face.K. Lateral arm plate, external face.L. Lateral arm plate, internal face. M. Lateral arm plate, lateral face. Abbreviations: dist = distal; dors = dorsal; prox = proximal; SA = spine articulation; Sp = spur; vent = ventral.

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. 6. Comparison between Ophioderma sodipallaresi Caso, 1986 (= Ophioderma teres (Lyman, 1860)), holotype from Mexico (ICML-UNAM 3.24.3, DD = 20.9 mm) (left), and Ophioderma teres, non-type material from Panama (USNM E23215, DD = 19.3 mm) (right). A–B. Dorsal disc. C–D. Jaws. E–F. Section between the arm and the distal genital slit. G, I. Dorsal arm (proximalmost). H, J. Dorsal arm (median).

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).