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Description

Myriopathes gen. nov.

 

(figs 1-6)

 

Antipathes Pallas, 1766: 205 (in part); Brook, 1889: 166 ("Antipathidae myriophylloides"); van Pesch, 1914: 39 (subgenus Euantipathes, in part); Pax, 1932: 410.

 

Diagnosis.— Corallum flabellate or bushy. Stem and branches pinnulate to the second order or more. Primary pinnules arranged biserially and alternately in two lateral or anterolateral rows. Secondary pinnules uniserial at base of primary pinnules, becoming biserial distally. Uniserial secondary pinnules usually projecting out of plane formed by biserial primary pinnules. When present, tertiary pinnules developing on secondary pinnules closest to base of primary pinnule.

 

Type species.— Antipathes myriophylla Pallas, 1766.

 

Type material.— It is unclear whether Pallas, 1766, described this species on the basis of an Indo-Pacific specimen he himself examined or whether he based it on the pre-Linnaean descriptions he cites (including Rumphius' Erica marina tenuis). Pallas (1766: 210) mentions, however, that he identified the species in various museums in America and gives the American coast as one of the two localities, the other being "Oceanus Indus". The species, as it has been recognized by subsequent investigators, including Brook (1889: 166) and van Pesch (1914: 42) is only known from the Indo-Pacific. Because of the limitations in the original description given by Pallas, and because of the morphological variability associated with this species, the selection of a neotype from the Indo-Pacific appears to be the best approach to resolving the difficulties in identifying the species. Therefore, a specimen collected near Ambon, Indonesia was selected as the neotype. This specimen fits the general description of the species as it has been used since Pallas's publication, and the locality agrees with that of Rumphius.

 

Neotype.— RMNH Coel. 24064, Indonesia, Moluccas, Ambon, Leitimur, S. coast, Hutumuri, 26.xi.1990, Rumphius Biohistorical Expedition 1990, sta 27, 22-25 m, coll. A. Fortuin & C.L.H.M. Fransen.

 

Description of the neotype.— The specimen selected as the neotype is about 20 cm tall and 30 cm wide (fig. 1). The basal stem diameter is 3.3 mm. The corallum is branched to the 6th order. The larger branches are up to 9 cm long and tend to form individual fronds separated from each other but overlapping such that in places the flabellate corallum has a thickness of several centimeters. The branches are complexly pinnulate to the third order. The primary pinnules are arranged bilaterally in two rows, as well as alternately along the branches (fig. 2). In each row the primary pinnules are 1.2-2.0 mm apart (mostly 1.4-1.8 mm apart). A maximum of about 12 primary pinnules occur along one centimeter of branch (counting those in both lateral rows). The primary pinnules are up to 7 mm long and 0.15 mm in basal diameter, and they are inclined distally; the distal angle they form with the branch being 60-70°. Three or four secondary pinnules are located on the lowermost portion of each primary (figs. 2 and 3). They are arranged uniserially, but as the primary pinnule increases in length, more distal secondaries become bilaterial, and the primary pinnule develops into a branch. The uniserial secondaries are at right angles or are inclined distally relative to the primary on which they occur. On each primary pinnule the uniserial secondaries form a plane that is generally perpendicular to the plane containing the branch and the primary on which they occur. The uniserially arranged secondaries have the same orientation from branch to branch, therefore, they all project out of one and the same side of the corallum, giving the corallum a clearly defined anterior and posterior side. The secondary pinnules are up to 2 mm long, with a basal diameter of about 0.1 mm (the longest secondaries occur at the base of the primaries, 0.2-0.8 mm from the branch). As the branches increase in diameter they may overgrow the point of insertion of the secondaries on the primaries. As a result the lowermost secondaries become embedded in the branch sclerenchyme and thus the branch can appear to have four rows of primary pinnules. A single tertiary pinnule may occur on the secondaries, particularly the lowermost of these (fig 3). The tertiaries are mostly 0.8-1.2 mm long and have a basal diameter of about 0.08 mm. They usually occur on the distal or upper side of the secondaries (in the direction of the branch), but they may also project out laterally or even basally.

 

The spines on the pinnules (fig. 4) are conical to somewhat horn-shaped, slightly compressed, and longer on the polyp side of the axis. On pinnules 0.7 mm in diameter, the polypar spines measure up to 0.11 mm and the abpolypar spines about 0.9 mm. On pinnules 0.12 mm in diameter, the polypar spines may be as much as 0.16 mm and the abpolypar spines 0.14 mm or less, and on branches 0.18 mm in diameter, the polypar spines measure 0.17 mm and the abpolypar spines 0.15 mm or less. The spines become more terete and more numerous on the larger branches, and on the stem, where they are about 0.2 mm tall, they are distinctly dendritic. The polyps are poorly preserved over most of the corallum. However, in places they can be seen to be arranged in a single series on the pinnular side of the branches and primary pinnules (corresponding to the side with the larger spines). Polyps on the secondary pinnules are often confined to the upper (distal) side; therefore, they tend to face towards the more distal polyps on the primary pinnules. The polyps, slightly elongated in the transverse axis, measure 0.6-0.8 mm in transverse diameter. The interpolyp space (between lateral tentacles of adjacent polyps) ranges from 0.2-0.4 mm, and there are about nine polyps per centimeter. In the preserved state the tentacles are knob-like and up to about 0.15 mm long.

 

Species Assigned to Myriopathes.— Nominal species that can be currently assigned to Myriopathes, as it is defined above, include Antipathes ulex Ellis & Solander, 1786, Antipathes panamensis Verrill, 1869, Hydradendriuni spinosum Carter ,1880, Antipathes japonica Brook, 1889, Antipathes bifaria Brook, 1889, Aphanipathes rugosa Thomson & Simpson, 1905, Antipathes lata Silberfeld, 1909, Aphanipathes stechowi Pax(1932), and Antipathes antrocrada Opresko, 1999. The type specimens of M. ulex and M. lata were not located, and assignment of these species to Myriopathes is based on the descriptions and illustrations given by the original and subsequent authors.

 

The species of Myriopathes listed above can be divided into two subgroups. In one group, represented by the type species, as well as M. ulex, M. panamensis, M. stechowi, M. spinosa, and M. rugosa, the corallum is generally flabellate (see fig. 1). The second group, containing M. bifaria, M. lata, M. japonica, and M. antrocrada (fig. 5) is characterized by a more bushy corallum, although on individual branches the arrangement of the smaller branches and primary pinnules can be somewhat planar.

 

Within these two subgroups the species are differentiated by the length, density and orientation of the primary pinnules, the number, length and density of the secondary pinnules and, to a lesser degree, the size and density of the spines. The pinnular arrangement of four species; M. myriophylla, M. japonica, M. bifaria, and M. antrocrada, is shown in fig. 6.

 

Remarks.— In his monograph on the Antipatharia, Brook (1889: 166-170) noted that in the "type of branching" several species (including A. panamensis, A. ulex, A. spinosa, A. japonica, and A. bifaria) had similarities with A. myriophylla Pallas. Brook described these species as belonging to the "Antipathidae Myriophylloides" group. The genus Myriopathes is equivalent to Brook's "Myriophylloides" group.

 

Myriopathes is very distinct from other genera in the family in that it is the only one in which the primary pinnules are arranged regularly in two rows as well as being subpinnulated. In the general morphology of the corallum, Myriopathes resembles Antipathella (see below), particularly those species of Myriopathes in which the subpinnulation is reduced to not more than a single secondary pinnule on the primary pinnules.

 

Etymology.— The genus name is derived from the name of the type species "myriophylla" and the commonly used suffix "pathes".

 

Distribution.— Species of this genus have been reported from the eastern Pacific (M. panamensis), Indo-Pacific (M. myriophylla, M. bifaria, M. ulex), Japan (M. japonica, M. stechowi, M. lata), Hawaii (M. ulex), Indian Ocean (M. rugosa), and Australia (M. antrocrada).”

 

(Opresko, 2001)

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© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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