Amphipholizona perplexa ( Nielsen, 1932 )

Gondim, Anne Isabelley, Christoffersen, Martin Lindsey, Dias, Thelma Lúcia Pereira & Solís-Marín, Francisco Alonso, 2016, Taxonomic status of the genera Amphipholizona H. L. Clark, 1915 (Ophiuroidea, Ophiolepididae) and Amphigyptis Nielsen, 1932 (Hemieuryalidae): systematic placement and synonymy, Zootaxa 4097 (3), pp. 381-395: 388-393

publication ID

http://dx.doi.org/10.11646/zootaxa.4097.3.6

publication LSID

lsid:zoobank.org:pub:161B0314-A85E-4324-A0D8-F2EFFC15685B

persistent identifier

http://treatment.plazi.org/id/03B68798-FFF5-FFF6-FF43-6CCAFED7FEA7

treatment provided by

Plazi

scientific name

Amphipholizona perplexa ( Nielsen, 1932 )
status

new comb.

Amphipholizona perplexa ( Nielsen, 1932)  new comb.

Figures 4View FIGURE 4 A –G, 5 A –L, 6 A –F

Amphigyptis perplexa Nielsen, 1932: 306  –307, fig. 22 a –b.― Fell, 1960: 12 (key).― Solís-Marín et al., 2005: 128; 2013: 564 (list).

Type material. Zoological Museum of Natural History Museum of Denmark. Two syntypes: ZMUC OPH 251 (examined from photographs provided by Dr. Jørgen Olesen).

Type locality. South of San José, Perlas Islands, Pacific Panama, 45.72 m.

Material examined. ICML-UNAM 3.41 .0, 1 spm. (dd = 4.19 mm), E. of San Marcos Islands, Gulf of California, coll. Hancock Pacific Expedition, 14 March 1936; ICML-UNAM 3.41 .4, 1 spm. (dd = 3.28 mm), North of Isla Tiburón, Gulf of California, St. 27, coll. Dr. Maria Elena Caso, Hendrichx Van der Heidel, Toledano G., Álvaro Cortés, 0 7 May 1982; ICML-UNAM 3.41 .1, 1 spm. (dd = 4.0 mm), Punta San Marcial, Gulf of California, St. 0 8, coll. Dr. Maria Elena Caso & Laura Calva Benítez, Cortés Cruise III, 30 May 1985; ICML- UNAM 3.41 .2, 1 spm. (dd = 3.61 mm), Ponta Arboleda, Gulf of California, St. 16, coll. Juan Torres Vega, Cortés Cruise III, 12 March 1985; ICML-UNAM 3.41 .3, 1 spm. (dd = 4.11 mm), La Paz Bay, Baja California Sur. USMN E 30907View Materials, 5 spms. (dd = 2.13, 3.34, 3.51, 3.61, and 3.63 mm), Off Southern California, California, USA, coll. Wolfson, F. H.

Diagnosis. Interradius covered by a single row of large polygonal plates. Arms short, flattened dorso-ventrally. Dorsal arm plate triangular or pentagonal. Ventral arm plate pentagonal and swollen. Dorsal and ventral arm plate with simple and fine stereom and some tubercles on central regions of plate. Tentacle scale lacking.

Description. Disc circular (dd = 4.19 mm), covered by few, flattened, polygonal, large plates ( Fig. 4View FIGURE 4 A, D). Radial shields large, approximately twice as long as wide, united along their full length, swollen at their distal adradial corner ( Fig. 4View FIGURE 4 A, D, G). A triangular plate separating distal extremities of radial shields sometimes present ( Fig. 4View FIGURE 4 D). Interradius covered by a single row of 2-3 large polygonal plates ( Fig. 4View FIGURE 4 A, D, G), marginal plate larger, wider, and trapezoid. Central region of disc covered by 10 to 20 flattened, polygonal plates ( Fig. 4View FIGURE 4 A, D), sometimes with small triangular or square plates occurring between them. Ventral interradius covered by imbricating scales smaller than the dorsal plates ( Fig. 4View FIGURE 4 B, C, F). Bursal slits short, localized on lateral margin of oral shields ( Fig. 5View FIGURE 5 B, C, F). Jaw short ( Fig. 4View FIGURE 4 C). Oral shields small, diamond shaped, longer than wide, with proximal angle sharp and distal angle rounded ( Fig. 4View FIGURE 4 C, F). Madreporite not differentiated. Adoral shields large, tumid, as long as wide, fully united proximally ( Fig. 4View FIGURE 4 C, F). Infradental papillae rectangular ( Fig. 4View FIGURE 4 C, F). Two oral papillae, distal longest and opercular, proximal most small and slightly rectangular ( Fig. 4View FIGURE 4 C, F).

Five short arms, approximately 2.5 times the diameter of the disc, slightly flattened dorso-ventrally ( Fig. 4View FIGURE 4 A, B, G). Dorsal arm plate pentagonal or triangular, two times wider than long, with distal margin straight ( Fig. 4View FIGURE 4 D, G). Simple and fine stereom with minute thorns, with some tubercles in central area of plate ( Fig. 5View FIGURE 5 F). Lateral arm plate visible dorsally and ventrally, with simple stereom ( Fig. 4View FIGURE 4 A, B, 6 A), pairs united dorsally and ventrally. Isolated plate from proximal arm about twice as high as wide, simple stereom with minute thorns on distal portion ( Fig. 5View FIGURE 5 A). Inner side of lateral plate slightly differentiated, with vertical and sinuous ridge, reaching middle of length of plate, flat knob on lower proximal part, inner perforation not discernible ( Fig. 5View FIGURE 5 B). Arm spine articulation formed by two lip-shaped parallel ridges of equal length, slightly curved, separated at both ends, two large openings of nearly equal size between them (muscle and nerve opening) ( Fig. 5View FIGURE 5 C). Ventral arm plate pentagonal, swollen, 1.5 times wider than long, proximal angle strongly pointed and distal margin straight ( Fig. 4View FIGURE 4 B, C, F), largely separated from following plate. Simple and fine stereom with minute thorns, with some tubercles in central region of plate ( Fig. 5View FIGURE 5 G). First ventral arm plate very small, narrow, pentagonal, twice longer than wide ( Fig. 4View FIGURE 4 C). Three to six arm spines, thin; the dorsal one is the longest (as long as one arm segment), remaining ones decrease in ventral direction ( Fig. 4View FIGURE 4 A). First arm segment with two arm spines, second with three, third with four, and from fifth onwards, six arm spines. Distal segments with only three arm spines. Arm spines with minute thorns ( Fig. 5View FIGURE 5 D, E). Tentacle pore large. Tentacle scale lacking ( Fig. 4View FIGURE 4 F).

The vertebrae are slightly longer than wide, non-keeled, with dorsal median groove V-shaped, a welldeveloped lateral curved groove, and a zygospondylous articulation ( Fig. 5View FIGURE 5 H, I, J, L). In proximal view the aboral muscle area (am) is slightly smaller than the oral muscle area (om), which is concave in distal direction ( Fig. 5View FIGURE 5 I). A well-developed suture line in dorsal and ventral view ( Fig. 5View FIGURE 5 J).

Adradial genital plate long, over the three first arm segments and in contact with the two first lateral arm plates by means of a long groove. Abradial genital plate scale-like, articulated laterally to the adradial genital plate ( Fig. 4View FIGURE 4 E).

Variations. Examined specimens measured between 3.28 and 4.19 mm in disc diameter (dd). Small morphological variations were observed. Only one specimen of 3.61 mm dd presented the primary plates well developed ( Fig. 6View FIGURE 6 D), these were the only plates present at the central region of the disc. The dorsal arm plate can vary from triangular to pentagonal. Usually, dorsal arm plates of triangular shape are observed on the first arm segments.

Color. Specimens preserved in alcohol are whitish. There is no information regarding color of living specimens.

Distribution. Gulf of California and Panama (Pacific Ocean).

Depth range. From 45.72 to 143 m ( Nielsen 1932; Solís-Marín et al. 2013). Solís-Marín et al. (2013) record the occurrence of this species from shallow waters. This may be a mistake, since no specimens analyzed in this work come from this depth.

Remarks. Nielsen (1932) described Amphipholizona perplexa  on the basis of two specimens, with a disc diameter between 3 and 3.5 mm ( Fig. 6View FIGURE 6 A, B, C), from Perlas Archipelago (Pacific Panama) at 45.72 m depth. This species has been rarely cited since its original description, being considered extremely rare. Amphipholizona perplexa  is currently known from only 10 specimens collected along the coast of California and Panama Bay, Pacific Ocean.

Amphipholizona perplexa  (junior synonymy Amphigyptis perplexa  ) was originally placed in the family Hemieuryalidae  (see comments for the genus), on the basis of the shape of the arm plates, of the oral structure, and of the shape of the bursal slits. However, this classification is incorrect. Amphipholizona perplexa  differs from Hemieuryalidae  in several characters, among which are: the presence of a circular disc, infradental papillae, six arm spines, tentacle scale lacking, and arm spine articulation formed by two parallel, slightly curved, ridges of equal length, and abradial and adradial genital plate long and similar in size. All these characters concur with the pattern seen in Amphiuridae  , and fit perfectly with the new diagnosis provided for the genus Amphipholizona  . Consequently, we propose the new combination Amphipholizona perplexa  and recommend transferring this genus to the Amphiuridae  .

According to Thomas (1966), A. perplexa  is similar to Amphipholis pentacantha H.L. Clark, 1915  . However, according to our observations, this similarity is restricted to the absence of a tentacle scale beyond the fourth arm segment in A. pentacantha  (there are two tentacle scales on the first segment and one on the second and third arm segments). In all remaining characters (e.g. disc covering, radial shields, dorsal and ventral arm plates, oral and adoral shields) these species are very different (see H.L. Clark 1915: 241, 242, pl. VI, figs. 1–2). Amphipholizona perplexa  is very closely related to A. delicata  . However, A. perplexa  differs from this latter species for having a short and slightly dorso-ventrally flattened arm, no tentacle scales along the arm and by the shape and ornamentation of the dorsal and ventral arm plates ( Table 1). Furthermore, the two species have a well-defined geographical distribution, A. perplexa  occurs in the Pacific Ocean, while A. delicata  is only known from the Atlantic Ocean. We thus consider the differences sufficient for maintaining A. delicata  and A. perplexa  as distinct species.

Ecological notes. This species is found in muddy, sandy or rocky bottoms ( Solís-Marín et al. 2013).

Morphological characters Species The genus Amphipholizona  is clearly an Amphiuridae  in several morphological aspects. However, this genus shares some characters with other, apparently non-related genera. One example is the morphology of the lateral arm plate, which has spine articulations, particularly the knobs on the inner side, which are typically amphiurid, while the general outline of the plate and especially the outer surface ornamentation are similar to the pattern found in some species of Ophiolepis  (see Thuy & Stöhr 2011: 36, Fig. 21), Ophiozonella Matsumoto, 1915  , and Ophiozonoida H.L. Clark, 1915  ( Ophiolepididae  ) (Ben Thuy and Daniela Y. Gaurisas personal communication).

Amphipholizona  seems to be more closely related to Amphipholis  than any other genus of Amphiuridae  . Both share a very similar pattern in the shape and arrangement of the oral frame and have one or no tentacle scales. It should be stressed that the great majority of species of Amphipholis  have two tentacle scales. The arrangement of oral papillae is presently considered important in separating genera in Amphiuridae ( Martynov 2010)  , and the presence of oral papillae appear to represent a conservative pattern within the Amphiuridae ( Hendler 1988)  . They may thus be indicative of deep phylogenetic affinities. Notwithstanding, the absence of tentacle scales is recorded in species across the Ophiuroidea, which suggests that this absence may be homoplastic. Only a thorough phylogenetic study may confirm possible historical relationships between these genera and will be able to clarify the affinities of this genus with some genera of Ophiolepididae  .

With the present study we have clarified the systematic position of the genus Amphipholizona  , and have contributed to the systematics, at least in part, of the families Ophiolepididae  and Hemieuryalidae  . Further efforts are needed in order to characterize these less-known taxa and to reconstruct phylogenetic relationships within Ophiuroidea.

TABLE 1. Comparison of morphological characters of Amphipholizona delicata H. L. Clark, 1915 and A. perplexa (Nielsen, 1932) new comb.

    Pentagonal or triangular. Stereom with minute thorns and with some tubercles in central region of plate
  Present, restricted to first five arm sgments  
ZMUC

Zoological Museum, University of Copenhagen

UNAM

Universidad Nacional Autonoma de Mexico

Kingdom

Animalia

Phylum

Echinodermata

Class

Ophiuroidea

Order

Ophiurida

Family

Ophiolepididae

Genus

Amphipholizona

Loc

Amphipholizona perplexa ( Nielsen, 1932 )

Gondim, Anne Isabelley, Christoffersen, Martin Lindsey, Dias, Thelma Lúcia Pereira & Solís-Marín, Francisco Alonso 2016
2016
Loc

Amphigyptis perplexa

Solis-Marin 2005: 128
Fell 1960: 12
Nielsen 1932: 306
1960