Ophioderma hybrida,

Stöhr, Sabine, Weber, Alexandra Anh-Thu, Boissin, Emilie & Chenuil, Anne, 2020, Resolving the Ophioderma longicauda (Echinodermata: Ophiuroidea) cryptic species complex: five sisters, three of them new, European Journal of Taxonomy 600, pp. 1-37: 22-24

publication ID

https://doi.org/10.5852/ejt.2020.600

publication LSID

lsid:zoobank.org:pub:A0FAB2BB-5CEF-42CB-9014-41655BC12D79

DOI

http://doi.org/10.5281/zenodo.3638053

persistent identifier

http://treatment.plazi.org/id/038FF87B-8C5E-FFD6-811F-A4DDCA24975B

treatment provided by

Plazi

scientific name

Ophioderma hybrida
status

sp. nov.

Ophioderma hybrida  sp. nov.

urn:lsid:zoobank.org:act:72379251-8181-4B42-8CB6-881F0C144526

Figs 9–10View FigView Fig; Tables 1–2

Diagnosis

Species of Ophioderma  with variable morphology. Dorsal arm plates single or as several pieces. Seven to 10 equal arm spines. Eight oral papillae. Colour pattern: disc dark brown or olive dorsally and ventrally, often with white spots. Dorsal arms dark brown with light brown or white and black spots, ventrally lighter brown. Maximum known size about 19 mm dd.

Etymology

This species has likely evolved by an ancient hybridization event between two species ( O. longicauda  and O. zibrowii  sp. nov. or their respective ancestors), which the Latin word hybrida  alludes to. It also refers to the mixed morphology of the species.

Material examined

Holotype

MEDITERRANEAN SEA • Tunisia, Kelibia ; 36°50′7.31″ N, 11°7′6.20″ E; depth 0.3–1.5 m; 3 Jul. 2013; Zined Marzouk & Alexandra Weber leg.; preserved in 95% ethanol; SMNH-Type-9185.GoogleMaps 

Paratypes

MEDITERRANEAN SEA • 11 specimens; same data as for holotype; SMNH-Type-9186GoogleMaps  8 specimens; Tunisia, Monastir; 35°46′28.83″ N, 10°50′18.93″ E; depth 2–5 m; 25 Jun. 2013; A. Weber leg.; preserved in 95% ethanol; SMNH-Type-9187GoogleMaps  .

Other material

MEDITERRANEAN SEA • 3 specimens (with dorsal disc removed, but present); same data as for holotype; SMNH-178454GoogleMaps  3 specimens; Tunisia, Tunis; 1849; Åberg leg.; SMNH- 35614, 123374, 123375  .

Description

Holotype ( Fig. 9View Fig)

Disc diameter 17.4 mm, two arms cut off near disc but present ( Fig. 9View Fig A–B). Radial shields covered by disc granules ( Fig. 9AView Fig). Dorsal arm plates weakly tumid, as 1–3 pieces on about first 30 joints, when single twice as wide as long, distal edge straight or concave ( Fig. 9View Fig C–D). Ten arm spines, all about equal in length, ventralmost slightly wider. Ventral arm plates overlapping, squared, distal edge convex ( Fig. 9EView Fig). Two oval scale-like tentacle scales, superimposed on the ventralmost spine. Ventral disc covered by granules similar to dorsal disc. Eight oral papillae, short, weakly pointed to round, Lyman’s ossicle large, pointing into mouth slit ( Fig. 9FView Fig). Tooth papillae larger than oral papillae, teeth rounded block-shaped. Oral shield almost twice as wide as long, with wide proximal angle, distal edge slightly convex. Madreporite larger, almost as long as wide ( Fig. 9BView Fig). Adoral shield long, narrow, extending around the lateral edge of the oral shield, separating it from the arm ( Fig. 9FView Fig). Adoral shields covered with granules, similar to disc granules. Proximal genital slits angled from oral shield to second arm joint, distal genital slits at disc edge, two arm joints long.

Disk dark brown dorsally with radiating lighter brown pattern and scattered white spots ( Fig. 9AView Fig). Dorsal arms dark brown with light brown and dark spots along the distal plate edges and on some lateral edges ( Fig. 9View Fig C–D). Ventral disc and arms light greenish brown, oral shields darker ( Fig. 9BView Fig).

Variation

The range of morphological variation is presented in Table 2 and on Fig. 10View Fig. The specimens vary in size from 9.8 to 18.7 mm disc diameter. Among the 23 examined specimens, the number of dorsal arm plate pieces varies considerably. Multiple plates or pieces have been found on the proximal arms, until about joint number 30, but not on all joints, and sometimes not on all arms ( Fig. 10EView Fig). In most specimens, there are only two pieces, but in a few animals, multiple pieces were observed ( Fig. 10E, H, NView Fig). Some specimens have only single dorsal arm plates ( Fig. 10B, KView Fig). More pieces are present in the larger specimens but there appears to be only a weak size relation for this trait. Likewise, the number of arm spines and oral papillae is not related to disc diameter. All but two animals have granule covered radial shields. Colour variations are limited. All examined specimens have a dark brown or olive dorsal disc with varying white patterning (from spots to radiating lines) and a dark ventral disc, similar or lighter oral frame and ventral arms. The dorsal arms show alternating light and dark bands and a series of light and dark spots along the distal edge of the dorsal arm plates.

Other specimens

SMNH- 35614 15.5 mm dd, SMNH-123374 16.3 mm dd, SMNH-123375 14.3 mm dd. Colour faded to light brown. Most of the granules rubbed off the discs, and status of the radial shields as naked/granule covered cannot be assessed, but they have an exposed area, devoid of scales. Eight oral papillae. Two to three dorsal arm plates on single joints (SMNH-123374), up to nine joints (SMNH- 123375), up to 12 joints (SMNH-35614), variable between arms. Juveniles present in the bursae.

Remarks

The origin of this species through an ancient hybridization event between O. longicauda  and O. zibrowii  sp. nov. (or their ancestors) ( Weber et al. 2019) is further supported by its high morphological variability. Multiple dorsal arm plates are typical of O. longicauda  , and in some specimens of O. hybrida  sp. nov. the most proximal joints bear several plates, forming a crowded mosaic pattern similar to O. longicauda  . The usually granule covered radial shields are shared with all species except O. zibrowii  sp. nov. ( Table 1) and are probably evidence of O. longicauda  (or its ancestor) being one of the ancestral species. The variation of arm spines and oral papillae overlap with both ancestral species and O. africana  sp. nov., but O. guineense  has a higher number of arm spines. Ophioderma hybrida  sp. nov. shares the vivid colour pattern of the arms with O. zibrowii  sp. nov. and O. guineense  , whereas O. africana  sp. nov. and O. longicauda  are darker and the spots on the arms are less obvious in the former. So far, O. hybrida  sp. nov. appears to be a smaller species with disc diameter under 20 mm, but more material is needed to confirm this. We believe that the reproductive mode of O. hybrida  sp. nov. is brooding given that brooding individuals have been collected in Tunisia ( Stöhr et al. 2009) and the ones examined in this study are morphologically more similar to O. hybrida  sp. nov. than to O. zibrowii  sp. nov., because they have more dorsal arm plates per joint. Yet, we cannot confirm it, as the brooding specimens from Tunisia were too old for genetic analyses (1849 and 1924; PCR amplification failed). In addition, all other O. hybrida  sp. nov. specimens have been collected outside the reproductive season so examination of their gonads was inconclusive in determining their reproductive strategy.

N

Nanjing University

E

Royal Botanic Garden Edinburgh

A

Harvard University - Arnold Arboretum