Ophioderma bichi, 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 : 159-166

publication ID	https://doi.org/ 10.5852/ejt.2024.947.2625
publication LSID	lsid:zoobank.org:pub:CBC9DA40-EC6D-4280-8BBC-6826D72A291E
DOI	https://doi.org/10.5281/zenodo.13610621
persistent identifier	https://treatment.plazi.org/id/03F3204B-FF94-8238-5535-B6E76026FD5F
treatment provided by	Plazi
scientific name	Ophioderma bichi
status	sp. nov.

Treatment

Ophioderma bichi sp. nov.

urn:lsid:zoobank.org:act:940B392E-8B70-408E-B306-142FC197D164

Figs 1–2 View Fig View Fig , 5 View Fig , 10–11 View Fig View Fig , 12C View Fig ; Tables 1–4 View Table 1 View Table 2 View Table 3 View Table 4

Ophioderma teres View in CoL – Steinbeck & Ricketts 1941: 391–392 (partim, non Lyman, 1860). — Ziesenhenne 1955: 190 (partim, non Lyman, 1860). — Brusca & Smith 1973: 318–319, figs 12.13–12.14 (partim, non Lyman, 1860). — Brusca 1980: 407, fig. 26.14a–b (partim, non Lyman, 1860). — Granja-Fernández 2019: 273–275 (partim, non Lyman, 1860).

Ophioderma sp. B – This study: 3–12, Figs 1–2 View Fig View Fig , Tables 1–4 View Table 1 View Table 2 View Table 3 View Table 4 .

Diagnosis

Radial shields covered with granules. Section between arm and distal genital slits with granule-bearing scales only. DAPs divided into multiple pieces (mean = 2, maximum = 9). Coloration uniform brown dorsally (preserved specimens).

Etymology

The species name bichi derives from the Sonoran lexicon, particularly the Cahita language, and means ‘naked’. Ophioderma bichi sp. nov. is typically uniform brown (DD> 11.0 mm), giving it a ‘naked’ appearance compared to its EP congeners, most of which display brilliant colors (e.g., O. panamense , O. variegatum ) or distinctive disc and arm patterns (e.g., O. occultum , O. teres ) ( Granja-Fernández et al. 2020; Humara-Gil et al. 2022). The specific epithet corresponds to a Sonoran word since the holotype was collected in Sonora, Mexico.

Material examined

Holotype

MEXICO • dry preserved specimen; Gulf of California, Sonora, Tucson Beach ; 31°20′48″ N, 113°38′30″ W; 18 Jan. 1969; B. Burch leg.; USNM E23455 About USNM .

GoogleMaps

Paratypes

MEXICO – Sonora • 2 specs (preserved dry); Gulf of California, Choya Bay, Tucson Beach ; 5 Nov. 1967; B. Burch leg.; tide pools; USNM E23397 About USNM • 1 spec.; same data as for holotype; USNM 1698589 About USNM GoogleMaps • 1 spec. (preserved in 96% ethanol); Gulf of California, Puerto Peñasco ; 31°20′8.03″ N, 113°38′5.88″ W; 2 Oct. 2015; D. Paz leg.; GenBank: OR789592 (COI) , OR800004 (16S) ; ICML-UNAM 18488 GoogleMaps .

Other material See Supp. file 1.

Description

Holotype

DD = 33.2 mm, AL = 127.5 mm, AL:DD = 3.8. Disc rounded, covered by rounded granules, slightly separated from each other. Granule size increasing from center to periphery. Some granules rubbed off near disc center, leaving scales visible. Dorsal disc granule density 54 per mm 2. Radial shields covered by granules. Eleven small plates visible near disc edge ( Fig. 10A View Fig ). Ventral interradii covered with small granules separated from each other; those closer to genital slits, larger. Four genital slits per interradius. Proximal genital slits oval, separated from distal section of oral shields by one or two rows of granules, but in contact with 1 st LAP, reaching up to proximal section of 2 nd VAP. Distal genital slits oval, slightly longer than proximal ones, placed between 7 th and 9 th arm segments; surrounded only by granule-bearing scales ( Fig. 10B View Fig ).

Oral shields 1.5× as wide as long, trilobed; proximal edge convex forming a rounded apex; rounded lateral edges; distal edge convex. Madreporite rounded triangular, with a central depression deviated towards distal section; distal edge convex. Adoral shields covered by granules, separated from each other. Jaws with 8–10 oral papillae: LyOs the largest, 3 × as long as wide, angled upwards; AdShSp rounded quadrangular, robust; 2°AdShSp smaller than AdShSp, rounded rectangular; LOPas 3–5, rectangular to conical, pointed; IPa similar to LOPas, more robust; TPa two at jaw apex, triangular to rectangular, robust. Teeth five: vT rounded rectangular; median teeth quadrangular to triangular; dorsalmost triangular and pointed. OPRSp not evident due to closed mouth. Oral plates covered with granules larger than those covering adoral shields, decreasing in size towards periphery ( Fig. 10C View Fig ).

Five arms rounded, tapering distally: one almost complete, four regenerating close to tip ( Fig. 10K View Fig ). Dorsal arm base with some small scales and few granules scattered between them ( Fig. 10D View Fig ). DAPs wider than long, typically divided into four and up to eight irregular pieces ( Fig. 10D–E View Fig ). DAP pieces sequence of the longest arm: first ten segments, 4, 8, 6, 8, 7, 5, 6, 5, 5, 6; 11 th –20 th, 4–8; 21 st –30 th, 4–6; 31 st –40 th, 4–7; 41 st –50 th, 3–5; 51 st –60 th, 3–7; 61 st –70 th, 3–5; 71 st –80 th, 2–4; 81 st –90 th, 1–2; 91 st –100 th, 1–2; 101 st –104 th, 1. Distalmost DAPs trapezoidal to triangular, entire ( Fig. 10F View Fig ). First VAP small, 2× as wide as long, with rounded edges ( Fig. 10B View Fig ). Subsequent VAPs quadrangular, longer than wide; distal edge convex ( Fig. 10G–H View Fig ). Distalmost VAPs triangular, rounded, slightly longer than wide ( Fig. 10I View Fig ). A pair of pores between the four proximalmost VAPs in all five arms ( Fig. 10B View Fig ). 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, 2, 2, 3, 4, 4, 6, 6, 7, 8, 10; 11 th –20 th, 10–11; 21 st –30 th, 10–11; 31 st –40 th, 8–11; 41 st –50 th, 9–10; 51 st –60 th, 9; 61 st –70 th, 8–9; 71 st –80 th, 7–8; 81 st –90 th, 7–8; 91 st –100 th, 6–7; 101 st –110 th, 4–6; 111 st –112 nd, 3. 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. 10J View Fig ). Two tentacle scales, rarely three; adradial tentacle scale oval, elongated, ⅔ VAP length; abradial tentacle scale shorter, ¾ adradial scale length, triangular ( Fig. 10G–H View Fig ). In the distalmost arm section, tentacle scales oval and elongated, adradial being the longest; last arm segments with only one scale ( Fig. 10I View Fig ).

General coloration uniform brown (dry specimen) ( Fig. 10K View Fig ). Dorsal side: disc brown ( Fig. 10A View Fig ). Arms brown ( Fig. 10D–F, K View Fig ). Ventral side: interradii brown ( Fig. 10B View Fig ). Oral shields brown; oral papillae and teeth cream ( Fig. 10B–C View Fig ). LAPs brown. Arm spines brown with cream bases and tips; the ventralmost, cream ( Fig. 10J View Fig ).

Disarticulated ossicles

Non-type specimen, USNM E23396 (DD = 28.1 mm, AL = 111.9 mm, AL:DD = 3.9). Radial shields irregularly triangular, elongated, covered in the intact animal; proximal edge convex; distal edge convex; adradial edge irregular with a median process; abradial edge with two processes, proximal subtle, distal prominent ( Fig. 11A–B View Fig ). Externally, distal half with swollen center showing multiple small pores, close to each other; additional larger pores closer to edges, proximalmost the largest ( Fig. 11A View Fig ). Internally, distal half center with three small middle pores; distal edge showing two rounded truncated bulbs, adradial one larger, separated by a furrow that continues to distal edge of shield ( Fig. 11B View Fig ). Dental plate fragmented into several pieces (up to five), each supporting one or two teeth in oval or round non-penetrating sockets; ventralmost piece also with round sockets for TPa ( Fig. 11C View Fig ). Adradial genital plate falcate, elongated, proximally curved. Abradial face with a short proximal furrow and two small pores close to distal edge; distal edge with two truncated knobs separated by a furrow, and a distal depression, noticed from the other side ( Fig. 11D View Fig ). Adradial face with a longitudinal groove and a notorious pore close to distal section. Distal edge rounded, laterally showing a depression followed by a central knob ( Fig. 11E View Fig ). Oral plates longer than high, middle section slightly lower than ends ( Fig. 11F– G View Fig ); abradial face with muscle fossa widening ventrally ( Fig. 11F View Fig ); adradial face with multiple pores at proximoventral edge of plate corresponding to oral papillae (lateral) and granule (ventral) sockets ( Fig. 11G View Fig ). Vertebrae zygospondylus ( Fig. 11H–I View Fig ). Proximal vertebrae wider than long, with dorsal muscle fossae larger than ventral ones ( Fig. 11H View Fig ). VAPs (from proximal arm section) quadrangular, slightly wider than long; proximal edge slightly concave, with a median spur; lateral edges with two points forming concave areas; distal edge convex ( Fig. 11J View Fig ). Internal face with two elongated lateral spurs, and a smaller, oval one in the middle ( Fig. 11K View Fig ). LAPs curved, 3 × as high as wide; dorsal edge slightly concave; ventral edge slightly convex, with a small, rounded condyle developing from internal side; proximal edge concave; distal edge convex ( Fig. 11L–N View Fig ). Proximal external LAP edge with two conspicuous, elongated, and triangular spurs in the middle ( Fig. 11L View Fig ), having their counterparts internally ( Fig. 11M View Fig ). Internal side with four pores near center, concave proximal ridge, and two separated bulbs near ventral edge, ventralmost protruding from plate ( Fig. 11M View Fig ). Ten spine articulations on distal edge, each surrounded by a thick lobe ( Fig. 11N View Fig ).

Paratype and non-type variations

Paratypes varied in size from 15.4 to 25.4 mm (DD). The smallest specimens (DD = 15.4 and 19.5 mm) did not show plates on the disc, whereas larger ones presented various irregular plates (DD = 24.1 mm) or a single plate near the arm base (DD = 25.4 mm). Three specimens (DD = 15.4, 19.5, and 24.1 mm) had rounded triangular rather than trilobed oral shields. All paratypes presented DAPs divided mainly into two pieces, although the maximum number of pieces reached varied with size, being three in the smallest (DD = 15.4 mm) and five in the largest (DD = 25.4 mm). The maximum number of arm spines also varied with size, ranging from nine (DD = 15.4 mm) to 12 (DD = 25.4 mm). In two specimens (DD = 24.1 and 25.4 mm), a few segments had three tentacle scales, while in the remaining two, all segments had two scales. Regarding coloration, one specimen presented some groups of light granules on the dorsal disc; two had arms slightly lighter than the disc, and another showed a small, cream speck on the distal section of each oral shield, except for the madreporite.

Other variations were observed in non-type specimens (DD = 8.5–32.9 mm). Two specimens had one radial shield partially naked. Seven of the smallest specimens (DD = 8.5–11.9 mm) presented mostly entire DAPs along the arm. Additionally, 18 specimens showed clusters of light granules on the ventral disc, ranging from a few to several. These were mainly present in specimens with DD = 8.5 to 11.0 mm but were also observed in larger ones with DD up to 19.5 mm.

Distribution and habitat

Ophioderma bichi sp. nov. is exclusively found in the northern Mexican Pacific waters, specifically in the Gulf of California (Baja California, Sonora, and Baja California Sur) and Revillagigedo Islands (Roca Partida Island). The northernmost record of this species corresponds to Punta Pelícano, Sonora (31° N), and the southernmost to Bahía Eclipse, Roca Partida Island (19° N) ( Fig. 5 View Fig ). Ophioderma bichi inhabits rocky substrate, shingle, and sediment under rocks and can be found from intertidal to 12 m depth. This is the third species of Ophioderma , alongside O. occultum and O. vansyoci , with a restricted distribution in the northern Mexican Pacific ( Hendler 1996; Hernández-Herrejón et al. 2010; Humara-Gil et al. 2022).

Remarks

Ophioderma bichi sp. nov. is another species that was previously ‘hidden’ within O. teres . Material of this new species in scientific collections dates back to 1888, but it was often identified as O. teres ( Steinbeck & Ricketts 1941; Ziesenhenne 1955; Brusca & Smith 1973; Brusca 1980; Granja-Fernández 2019). Remarkably, Ziesenhenne (1955: 190) noted that certain “uniform brown” specimens from the northern Mexican Pacific did not match Lyman’s (1860) description of O. teres ; still, he interpreted the differences as intraspecific variations. Those specimens belonged to O. bichi .

Ophioderma bichi sp. nov. resembles O. teres in having covered adoral shields and divided DAPs. However, they differ in the following characters: 1) radial shields always covered in O. bichi versus radial shields either covered or naked in O. teres ; 2) section between the arm and distal genital slits only with granule-bearing scales in O. bichi , and with naked and granule-bearing scales in O. teres ; 3) coloration uniform brown in O. bichi versus disc and arms brown speckled with cream in O. teres ; and 4) O. bichi is distributed in the nort hern Mexican Pacific, and O. teres is mainly found on the Pacific coast of Central America.

Other species with which O. bichi sp. nov. might be mistaken are O. occultum and O. unicolor stat. nov. In the collections, O. bichi was frequently found alongside O. occultum , although in lower abundance: a specimen of O. bichi for every 2– 46 specimens of O. occultum . These species share their covered radial and adoral shields, divided DAPs, and are distributed in the same areas (Gulf of California and Revillagigedo Islands). Nevertheless, they differ in two important characters: 1) O. bichi only presents granule-bearing scales in the section between the arm and the distal genital slits, while O. occultum presents naked and granule-bearing scales, and 2) O. bichi presents a uniform brown coloration, while O. occultum has banded arms and paired white blotches in the median and distal arm sections ( Humara-Gil et al. 2022). These characters can change in young specimens, making their differentiation difficult. In such cases, the most reliable character to differentiate both is the banding in the arms of O. occultum , which is never present in O. bichi ( Humara-Gil et al. 2022) . Regarding the confusion between O. bichi and O. unicolor , the differences between both are indicated above (see O. unicolor Remarks).

A relevant variation in O. bichi sp. nov. was observed in its coloration. Although all but one specimen had a uniform brown coloration on the dorsal side, there were differences in the ventral coloration of the disc, which could be either uniform brown (n = 36) or with clusters of white granules (n = 18). This variation appears to be associated with age, as younger (= smaller) specimens exhibited white granules more frequently (see Paratype and non-type variations). An age-related coloration in O. bichi would not be uncommon, as changes in the coloration of juveniles have been documented in other species of Ophioderma , such as O. cinereum , O. occultum , and O. panamense ( Hendler et al. 1995; Granja-Fernández et al. 2014; Humara-Gil et al. 2022). Further investigation of O. bichi specimens of various sizes is necessary to corroborate whether this variation is indeed related to the developmental stage.