Phragmatopoma, Morch, 1863

Chávez-López, Yessica, 2020, New species and new records of Phragmatopoma (Polychaeta: Sabellariidae) from Tropical America, Zootaxa 4845 (3), pp. 301-330 : 325-327

Phragmatopoma sp.

Figure 11 A–I

Material examined: One specimen. Costa Rica: UMAR-Poly-OH-042, ( Cabuyal Beach , Guanacaste, 10°40’27”N, 85°39’12”W, intertidal, on rock, October 30, 2012, coll. T. F. Villalobos-Guerrero) .

Description. Colour pattern in preserved specimens. Body pale yellow ( Fig. 11A ). Outer paleae with blade amber and handle cherry; median plume translucent ( Fig. 11E ). Middle paleae dark brown with cherry tip ( Fig. 11F ). Inner paleae amber ( Fig. 11G ). Opercular papillae pale yellow in dorsal section, and light purple in the ventral. Median ridge with brown eyespots ( Fig. 11C ). Tentacles light purple ( Fig. 11 C–D). Building organ and ventral region of thorax slightly brown. Parathoracic chaetae translucent. Abdominal neuropodia with brown spots very small. Abdominal neurochaetae and uncini translucent ( Fig. 11 H–I). Caudal peduncle brown in lateral margin.

Body. Complete specimen of 10 mm total length; parathoracic region 1.2 mm wide; 29 abdominal segments; caudal peduncle broke, 1 mm long ( Fig. 11A ).

Operculum. Opercular crown and opercular stalk completely fused. Opercular crown conic and circular, slightly protruding in lateral view ( Fig. 11 A–B, D). Three rows of paleae, only two visible: 68 outer paleae, 25 middle and inner paleae. Outer paleae geniculate with a pair of heterodont teeth, one lacerate and the other blunted; flat blade twice longer than wide, serrated margin, without transversal thecae visible; median plume short, ½ as long as blade, longer than wide, filamentous ( Fig. 11E ). Middle paleae strongly geniculate with straight peak, smooth surface; subquadrangular nape, decurrent, serrated surface, wider than peak, ¼ as long as peak; chin slightly wider than long, margin serrated; blunt tip falcate, smooth margin ( Fig. 11F ). Inner paleae strongly geniculate with serrated peak, straight, almost seven times longer than wide; nape smooth; tip without filaments ( Fig. 11G ). Papillae small and oval. Oral tentacles unbranched. Median ridge short, ½ as long as opercular stalk, with marginal and center eyespots ( Fig. 11C ). Median organ absent. Building organ ‘U’-shaped.

Thorax. Chaetiger 1 with a pair of neuropodia, chaetae broken. Chaetiger 2 with a pair of conical cirri, neuropodia with chaetae broken and a pair of branchiae.

Parathorax. Three parathoracic segments. Chaetigers without branchiae, possibly lost by fixation. Notopodia and neuropodia with all chaetae broken.

Abdomen. Some segments with a pair of branchiae, most branchiae broken. Neurochaetae verticillate of different lengths ( Fig. 11H ). Notopodia with a series of uncini with seven pairs of teeth ( Fig. 11I ).

Caudal region. Caudal peduncle elastic and smooth, broken.

Tubes. Lost.

Habitat. Found on rocks in the intertidal zone. In the same aggregation as P. villalobosi n. sp.

Distribution. Only known from Cabuyal Beach, Guanacaste, Costa Rica.

Remarks. Most outer paleae were broken or have lost the median plume; in the same way, the parathoracic and abdominal chaetae were broken or so fragile. These could be a result of fixation 96% ethanol.

Although Phragmatopoma sp. and P. villalobosi n. sp. were collected in the same aggregation (Villalobos-Guerrero com. pers.), both have various important differences in their morphology. Phragmatopoma villalobosi n. sp. has ridges in the middle paleae of the mid-dorsal section of opercular crown, and the outer paleae have median plume long; both characters are absent in Phragmatopoma sp. Also, the number of paleae is considerably different, having most paleae in Phragmatopoma sp. (68 outer paleae, 25 middle paleae) than in P. villalobosi n. sp. (38 outer paleae, 17 middle paleae).

The circular shape of the opercular crown and the middle paleae of Phragmatopoma sp. are similar to the ones present in P. carlosi n. sp. However, the middle paleae of Phragmatopoma sp. have a decurrent nape slightly longer than blade of paleae and a tip blunted and curved, in contrast with the decurrent nape, slightly short with tip slender and sharp observed only in the dorsal paleae of P. carlosi n. sp.

Phragmatopoma sp. was obtained from the same aggregation as P. villalobosi n. sp. It is known that an aggregation can be built by the species of different genera (e.g. P. californica and Sabellaria nanella , or Phragmatopoma sp. 1 and S. nanella fide Santos et al. 2014 , Chávez-López obs. pers.) or by species of same genera (e.g. Idanthyrsus cretus and Idanthyrsus sp. 1 fide Chávez-López in prep). However, it is unknown how common these mixed associations are. For this reason, a detailed review of sabellariid aggregations is necessary.

Figures

FIGURE 11. Phragmatopoma sp. A, Complete body, dorsal view. B, Opercular crown, up view. C, Median ridge. D, Operculum, lateral view. E, Outer paleae. F, Middle paleae. G, Inner paleae. H, Verticillate abdominal chaetae. I, Abdominal uncini. Scale bars: A: 2 mm; B: 500 μm; C: 300 μm; D: 1 mm; E, H: 50 μm; F: 150 μm; G: 100 μm; I: 10 μm. Abbreviation: op, outer paleae; mp, middle paleae; ip, inner paleae; mr, median ridge; pl, median plume; lt, lateral teeth.