Ophioderma pentacanthum H.L. Clark, 1917

Granja-Fernández, Rebeca, Pineda-Enríquez, Tania, Solís-Marín, Francisco Alonso & Laguarda-Figueras, Alfredo, 2020, Ophioderma hendleri sp. nov. (Echinodermata: Ophiuroidea: Ophiodermatidae) and its congeners from the Eastern Pacific, European Journal of Taxonomy 729, pp. 11-41 : 27-30

Ophioderma pentacanthum H.L. Clark, 1917

Fig. 7 , Table 1

Ophioderma pentacantha H.L. Clark, 1917: 443–444 , pl. 3–4, figs 1–2.

Ophioderma pentacanthum – Ziesenhenne 1955: 197. — Downey 1969: 115. — Maluf 1988: 83, 203. — Buitrón-Sánchez & Solís-Marín 1993: 221.

Ophioderma pentacantha – Maluf 1991: 354. — Hickman 1998: 25. — Pineda-Enríquez et al. 2013: 60–62. — Solís-Marín et al. 2013: 570. — Tirado-Sánchez et al. 2014: 24. — Granja-Fernández et al. 2015a: 41.

Diagnosis

Radial shields covered by very small granules. Naked adoral shields, longer than broad. First ventral arm plate large and rhombic. Up to 6 arm spines, very large and slender; the dorsalmost is the shortest and the ventralmost is much larger than the rest, overlapping the tentacle scales of the contiguous segment. Adradial tentacle scale almost double in size of abradial one. In vivo coloration: disc orange with dark blotches, arms with transverse brown bands.

Examined material

Holotype

ECUADOR • 1 spec.; Galapagos, Hood Island , 5 miles SW of Ripple Point, Albatross Station 4643 ; 1°29´0˝ S, 89°48´30˝ W; 183 m (100 fms); 7 Nov. 1904; Albatross Expedition leg.; broken shells and globigerina; USNM E726 .

Paratypes

ECUADOR • 1 spec.; same collection data as for holotype; MCZ OPH-4519 • 1 spec.; same collection data as for holotype; USNM E9798 .

Other material

COSTA RICA • 1 spec.; between Everest and Piedra, Cocos Island ; 5°34´04.72˝ N, 87°02´37.84˝ W; 102 m; 15 Oct. 2016; DeepSee submersible (Dive 2377) leg.; MZUCR-ECH 1413 • 1 spec.; Parque Nacional Isla del Coco ; 5°34´35.21˝ N, 87°03´27.96˝ W; 142 m; 14 Sep. 2013; DeepSee submersible leg.; MZUCR-ECH 1414 • See: Supplementary material.

Description (paratype MCZ OPH-4519)

DD = 21.1 mm; 5 arms, LA = 147.7 mm. Disc flat and rounded. Dorsal disc densely covered by rounded and fine granules, which are very close together, granule density 182 mm-2; granules extend to base of arms. Some granules rubbed off in some areas of disc. Radial shields completely covered by granules ( Fig. 7A ). Interradii covered with granulation, similar to on dorsal disc ( Fig. 7B ). Four genital slits on each interradius; proximal and distal genital slits elongated; distal genital slits surrounded by granules and few scales that are next to side of lateral arm plates ( Fig. 7B ).

Oral shields broader than long, rounded triangular, with convex obtuse proximal angle, straight distal edge, obtuse lateral angles. Madreporite with a small, circular, and shallow depression located in distal part of oral shield. Adoral shields naked, triangular, longer than broad, and separated. Jaws bear 8–9 papillae on each side: LyOs small, 1.5× as long as broad, angled upwards; AdShSp largest, rounded; 2°AdShSp smaller but similar in shape to AdShSp; LOPa 3–4 conical, pointed, and separated, 1 st LOPa smaller but similar in shape to 2°AdShSp; IPa sometimes smallest, elongated, pointed and separated; TPa 2 at jaw tips, larger than LOPa, elongated, robust, and pointed, slightly or completely separated. vT 1; 4 teeth, all robust. OPRSp 1 large and pointed at each side, visible within buccal cavity. Granules covering oral plates, slightly longer than those on dorsal disc and interradii ( Fig. 7C ).

Dorsal base of arms with granules and with approximately 11 scales laterally at arm. Dorsal arm plates 3× broader than long, overlapping and trapezoidal, with distal edge straight or slightly incised and rounded lateral edges ( Fig. 7D ). First ventral arm plate large, broader than long, rhomboid ( Fig. 7C ). Subsequent ventral arm plates quadrangular, slightly broader than long ( Fig. 7E ). Paired and large pores between ventral arm plates 1–2, 2–3, 3–4, 4–5, 5–6 ( Fig. 7B, G ). LAP with up to 5–6 arm spines; distalmost segments with 3–4 arm spines. Arm spines with a blunt tip, slender and very large; approximately one arm segment length. Dorsalmost arm spine shortest and slender; ventralmost arm spine longest and more robust than rest, in contact with and covering tentacle scale of succeeding joint ( Fig. 7E ). Two tentacle scales; adradial tentacle scale ovoid and very elongated; abradial tentacle scale subtriangular and half size of adradial one ( Fig. 7E, G ).

Color light brown (dry specimen) ( Fig. 7F ). Dorsal side: disc light brown and mottled dark brown in center ( Fig. 7A ); arms light brown with transverse dark brown bands every 2 or 3 segments ( Fig. 7D, F ). Ventral side interradii: beige in center and in proximal part, and light brown on margin, with some beige marks ( Fig. 7B ). Jaw in general beige, but oral shields and granules brown in color ( Fig. 7C ). Ventral arm plates beige ( Fig. 7E ).

Habitat and distribution

Previously known only for Galapagos Islands, Ecuador (H.L. Clark 1917; Ziesenhenne 1955; Downey 1969; Maluf 1988; Hickman 1998; Solís-Marín et al. 2013). In this work, a new distribution record is reported for Cocos Island, Costa Rica (MZUCR-ECH 1413, MZUCR-ECH 1414; see Remarks). From 102–183 m depth (H.L. Clark 1917). Collected in broken shells (H.L. Clark 1917).

Remarks

In the original description of O. pentacanthum, H.L. Clark (1917) designated an uncatalogued specimen as “heliotype” (= holotype), including four additional specimens, but a proper designation of the type material (including catalog numbers) was lacking at that moment. Downey (1969) considered the specimen USNM E726 (DD = 27 mm) as paratype, not recognizing it as the holotype in spite of a museum label marking it as type material by H.L. Clark (pers. comm. Pawson, 2020), also not considering the illustration already included in the original description. However, according to the International Code of Zoological Nomenclature ( ICZN 1999), Articles 73.1.2 and 73.1.4, the described and illustrated specimen which corresponds to USNM E726 should be treated as the holotype. During the revision of the paratypes only two specimens were found: MCZ OPH-4519 and USNM E9798. The labels of the paratype USNM E9798 indicate the presence of two specimens, but the lot includes only one. Therefore, two specimens are “lost”, one that is part of USNM E9798, and a second one whose catalog number is unknown, but in case they are found, they must be treated as paratypes.

All the morphological characters of the holotype, paratypes, and voucher specimens correspond with the original description by H.L. Clark (1917); nevertheless, we observed other relevant characters. H.L. Clark (1917) coined the named O. pentacanthum based on the number of arm spines (five), but we observed that most of the examined specimens (MCZ OPH-4519, MZUCR-ECH 1413, MZUCR-ECH 1414) had up to six arm spines. It is important to mention that the low number of arm spines is one of the most important diagnostic characters for this species since O. pentacanthum is the only Ophioderma in the Eastern Pacific having up to six arm spines, while the rest of its congeners have more than eight. Another important characteristic that has not previously been mentioned is the elongation of the genital slits ( Fig. 7 G–H, J), which is not found in other Ophioderma from the Eastern Pacific; perhaps, the large elongation of these genital slits is due to the large size of the specimens, but this must be confirmed when more data from specimens of different sizes is obtained. One of the most remarkable features of O. pentacanthum is the paired and large pores between the most proximal ventral arm plates. The paratype MCZ OPH-4519 ( Fig. 7G ) presents them on at least the first six arm segments, but they cover ¼ of the arm in the Costa Rican specimens ( Fig. 7 H–K). Furthermore, the observed pores in such specimens are extremely large (occupying most of the proximal portion of the ventral arm plates) and elongated in the first segments ( Fig. 7H, J ), decreasing in size and becoming more rounded towards the medial ( Fig. 7I, K ) and distalmost part of the arm. The reason why H.L. Clark (1917) did not observe these pores could be related to the smaller size of the type material (MCZ OPH-4519, DD = 21.1 mm) in comparison to the specimens from Costa Rica (MZUCR-ECH 1413, DD = 23 mm; MZUCR-ECH 1414, DD = 26.8 mm). Taking into account all the nominal species, it seems that smaller specimens of Ophioderma tend to have reduced and fewer pores (or even absent) in the ventral part of the arm, whilst larger specimens can have larger and more numerous pores being a characteristic inherent of growth; this agrees with observations made by Nielsen (1932). Nevertheless, more specimens are necessary to review and compare to corroborate this assumption and to determine whether the pores have any functional importance in the organisms (pers. com. Stöhr & Granja-Fernández, 2017). Lastly, it is important to remark that the field notes of the specimens from Costa Rica mentioned that the in vivo color of O. pentacanthum was orange with brown botches on the disc and arms with transversal brown bands; this is the first record of the in vivo coloration for this species.

H.L. Clark (1917) described this species from the Galapagos Islands but it was subsequently recorded in the Gulf of California, Mexico, and Guatemala ( Ziesenhenne 1955; Solís-Marín et al. 2013). In the review of the genus Ophioderma by Ziesenhenne (1955), he mentioned that the occurrence of O. pentacanthum in the Gulf of California (one specimen deposited in the Allan Hancock Collection) was “rare”. Nevertheless, many authors have considered this record as valid ( Maluf 1991; Buitrón-Sánchez & Solís-Marín 1993; Maluf & Brusca 2005; Granja-Fernández et al. 2015a). We reviewed all the LACM Ophioderma material, where all the material of the Allan Hancock Foundation is deposited, and we could not find any material corresponding to Ziesenhenne´s record. Moreover, in all the other visited collections we did not find any specimens labeled and/or identified as O. pentacanthum , except for the type material from the Galapagos Islands. Despite the rarity of O. pentacanthum in scientific collections, the reviewed specimens agree with the distribution in the Southeastern Pacific (Galapagos Islands and Cocos Island) at depths below 100 m (H.L. Clark 1917). Consequently, it is plausible that Ziesenhenne´s specimen does not correspond to O. pentacanthum but to a similar species (e.g., O. hendleri sp. nov.). Also, the Solís-Marín et al. (2013) record of O. pentacanthum from Guatemala is erroneous. Therefore, we suggest that the records from Mexico and Guatemala should be considered invalid.

Figures

Fig. 7. Ophioderma pentacanthum H.L. Clark, 1917, paratype (A–G = MCZ OPH-4519, DD = 21.1 mm H–I = MZUCR-ECH 1413, DD = 23.0 mm; J–K = MZUCR-ECH 1414, DD = 26.8 mm). A. Dorsal disc. B. Ventral disc. C. Mouth. D. Dorsal arm. E. Ventral arm. F. Dorsal view. G. Pores between proximal ventral arm plates. H. Pores in proximal ventral arm plates. I. Pores in median ventral arm plates. J. Pores in proximal ventral arm plates. K. Pores in median ventral arm plates.