Phragmatopoma villalobosi, Chávez-López, 2020

Chávez-López, Yessica, 2020, New species and new records of Phragmatopoma (Polychaeta: Sabellariidae) from Tropical America, Zootaxa 4845 (3), pp. 301-330 : 322-325

Phragmatopoma villalobosi n. sp.

Figure 10 A –J

LSID: urn:lsid:zoobank.org:act:A3094DD9-3CA4-4A08-A383-4599B8DE562C

Type material. Holotype: UMAR-Poly-OH-040, Cabuyal Beach , Guanacaste, 10°40’27”N, 85°39’12”W, Costa Rica, intertidal, on rock, October 30, 2012, coll. T. F. Villalobos-Guerrero ; Paratypes: UMAR-Poly-OH-041, three specimens, Cabuyal Beach, Guanacaste, same as holotype .

Description. Color pattern of preserved specimens. Body pale yellow to fourth abdominal segment, the rest of the segments dark brown in dorsal and ventral view ( Fig. 10A). Outer paleae yellowish; median plume translucent ( Fig. 10D). Middle paleae dark amber ( Fig. 10 E–F); dorsal paleae with ridge translucent ( Fig. 10E). Inner paleae amber ( Fig. 10G). Opercular papillae light brown in the dorsal region, completely brown in ventral ( Fig. 10A, C). Median ridge with brown eyespots ( Fig. 10C). Opercular stalk brown dark in the lateral region. Tentacles light brown ( Fig. 10C), branchiae pale yellow to dark. Parathoracic chaetae yellowish ( Fig. 10H). Abdominal neurochaetae and uncini translucent ( Fig. 10I). Caudal peduncle completely black ( Fig. 10A).

Body. Complete specimen of 9 mm total length; parathoracic region 0.8 mm wide; 27 abdominal segments; caudal peduncle broke. Body complete, but broken in the middle of abdominal segments ( Fig. 10A).

Operculum. Opercular crown and opercular stalk completely fused. Opercular crown conic and oval, very protruding in lateral view ( Fig. 10 A–B). Three rows of paleae, only two visible: 39 outer paleae, 39 middle and inner paleae. Outer paleae geniculate with a pair of heterodont teeth, one blunt and another broken; flat blade twice longer than wide, with serrated margin in the base and smooth distally; paleae of the mid-dorsal section of opercular crown with long median plume, almost as long as blade, five times longer than wide, filamentous with thin filaments, ½ as long as plume ( Fig. 10D); paleae of the mid-ventral sections without median plume, blade broken. Middle paleae strongly geniculate of two different shapes, depending on its position in the opercular crown; peak elevated with transversal thecae; mid-dorsal paleae with a prominent ridge ( Fig. 10E); straight quadrangular nape with serrated surface, slightly wider than peak, and short, 1/7 as long as peak; small chin, as long as wide, with serrated margin; sharp tip curved in mid-dorsal paleae ( Fig. 10E) and blunt tip straight in mid-ventral ( Fig. 10F). Inner paleae strongly geniculate with serrated peak, slightly elevated, eight times longer than wide; nape smooth; tip without filaments ( Fig. 10G). Papillae small and oval ( Fig. 10C). Oral tentacles unbranched. Median ridge short, ½ as long as opercular stalk with eyespots ( Fig. 10C). Median organ absent. Building organ ‘U’- shaped.

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

Parathorax. Three parathoracic segments. Chaetigers with a pair of branchiae. Notopodia with lanceolate chaetae interspersed with small capillary chaetae ( Fig. 10H). Neuropodia with lanceolate chaetae interspersed with capillary chaetae; neurochaetae thinner than notochaetae. Most of chaetae broken.

Abdomen. Some segments with a pair of branchiae, most branchiae broken. Neurochaetae verticillate of different length. Notopodia with a series of uncini with seven pairs of teeth ( Fig. 10I).

Caudal region. Caudal peduncle elastic and smooth, broken ( Fig. 10A).

Tubes. Lost.

Variation. Body measurements varied from 4–9 mm total length; parathoracic region 0.8–1 mm wide; caudal peduncle broken (n= 4 spec.). The number of abdominal segments varied from 23–27. One specimen lacks middle paleae dorsal with ridges.

Habitat. Found on rocks in the intertidal zone.

Distribution. Only known from Cabuyal Beach, Guanacaste, Costa Rica ( Fig. 13).

Etymology. This new species is named after Tulio F. Villalobos-Guerrero, a colleague who collected the type specimens.

Remarks. The specimens reviewed have most outer paleae broken; this could be a consequence of the fixation solution, 96% ethanol. Phragmatopoma villalobosi n. sp. differs from all Phragmatopoma species by the presence of ridges in the middle paleae of mid-dorsal section of the opercular crown ( Fig. 10E), and by the dark color pattern in the abdominal region ( Fig. 10A).

Phragmatopoma villalobosi n. sp. has a very protruding conical operculum ( Fig. 10 A–B); this is a shared character with P. balbinae n. sp. and P. attenuata . However, P. balbinae n. sp. has outer paleae as long as wide, and not twice longer than wide as in P. villalobosi n. sp.; middle paleae with decurrent nape in P. balbinae n. sp. and not straight as Costa Rica specimens; and inner paleae with peak elevated and not straight as in P. villalobosi n. sp.

Phragmatopoma villalobosi n. sp. and P. attenuata also share a similar shape in outer paleae and median plume long, with thin filaments, but in P. attenuata the filaments of the median plume are longer (as long as blade) than in P. villalobosi n. sp., as long as ½ of the blade.