Paucibranchia miroi, Molina-Acevedo, 2018

Molina-Acevedo, Isabel C., 2018, Morphological revision of the Subgroup 1 Fauchald, 1970 of Marphysa de Quatrefages, 1865 (Eunicidae: Polychaeta), Zootaxa 4480 (1), pp. 1-125 : 72-77

publication ID	https://doi.org/ 10.11646/zootaxa.4480.1.1
publication LSID	lsid:zoobank.org:pub:0D3D99EC-107A-4D6B-B19E-52147C6C141E
DOI	https://doi.org/10.5281/zenodo.5953882
persistent identifier	https://treatment.plazi.org/id/CE78C444-FF8F-2136-FF5B-A142FAC6FCD5
treatment provided by	Plazi
scientific name	Paucibranchia miroi
status	sp. nov.

Treatment

Paucibranchia miroi View in CoL n. sp.

Figures 50–53 View FIGURE 50 View FIGURE 51 View FIGURE 52 View FIGURE 53 , Tables 1–2

Material examined. Type material: Holotype USNM 1233966 View Materials , R/ V Pillsbury, Cruise 6607, sta. 448, off center of Panama, Caribbean Sea , 09°08' N 80°56' W, 21 Jul 1966, 962– 878 m. Paratypes: UMML 22.1130 View Materials (3), ECOSUR 0 197 (3), R/ V Pillsbury, Cruise 6607, sta. 407, off center of Panama, Caribbean Sea GoogleMaps , 09°01' N 77°26' W, 18 Jul 1966, 1171– 1239 m. Additional material: UMML 22.1131 (10), Same data as paratypes. UMML 22.1132 (1), R/V Pillsbury, Cruise 6607, sta. 364, south of the Colombian Caribbean, 09°24' N 76°34' W, 13 Jul 1966, 933– 961 m. UMML 22.1133 (4), R/V Pillsbury, Cruise 6607, sta. 413, south of the Colombian Caribbean, 08°50' N 76°54' W, 18 Jul 1966, 1281– 963 m. UMML 22.1134 View Materials (1), R/ V Pillsbury, Cruise 6907, sta. 861, west Canouan Island , Saint Vincent and the Grenadines, Caribbean Sea GoogleMaps , 12°42' N 61°06' W, 0 4 Jul 1969, 380 m. UMML 22.1135 View Materials (2), R/ V Pillsbury, Cruise 7006, sta. 1177, Gulf of Gonâve, Haiti, Caribbean Sea GoogleMaps , 19°21.5' N 73°50' W, 30 Jun 1970, 1525 m.

Description. Holotype complete, with 83 chaetigers, L10= 13 mm, W10= 5 mm, TL= 48 mm. Anterior region of body with convex dorsum and flat ventrum; with a ventral groove from chaetigers 5 to last chaetiger; body depressed from chaetiger 8, widest at chaetiger 23, tapering after chaetiger 24.

Prostomium bilobed, 2 mm long, 3.4 mm wide, frontally truncated, dorsally swollen, without median sulcus ( Fig. 50A–B View FIGURE 50 ), ventral sulcus deep. Prostomial appendages in semicircle, equidistant. Palps reaching anterior end of second peristomial ring; lateral antennae reaching the middle of second peristomial ring; median antenna reaching first chaetiger. Palpophores and ceratophores ring-shaped, short, slender; palpostyles and ceratostyles tapering, with base thicker than palpophores and ceratophores, without articulation. Eyes absent.

Peristomium bigger than prostomium (3 mm long, 4.4 mm wide), first ring two times longer than second ring; separation between rings ventrally, faintly visible dorsally and laterally ( Fig. 50A–B View FIGURE 50 ). Inferior lip smooth.

Maxillary apparatus with MF= 1+1, 6+5, 9+0, 5+11, 1+1 ( Fig. 50C View FIGURE 50 ). Maxillary carriers 3.3 times shorter than length of MI. MI forceps-like; closing system 4 shorter than length of MI; ligament between MI and MII rectangular, sclerotized ( Fig. 50C View FIGURE 50 ). MII wide; two distal teeth bigger, directed laterally, other teeth recurved; cavity opening oval, 4.3 times shorter than length of MII; outer edge of the maxilla with thick border which fits the MI ( Fig. 50D View FIGURE 50 ); ligament between MII and MIII, and right MIV, slightly sclerotized ( Fig. 50C View FIGURE 50 ). MIII short; three distal teeth smaller, rounded; with rectangular attachment lamella, sclerotized, slender, situated in center of posterior edge of maxilla ( Fig. 50C View FIGURE 50 ). Left MIV with bigger three distal teeth; attachment lamella semicircular, slender, situated 2/3 along length of posterior end of maxilla. Right MIV with blunt teeth, bigger three distal teeth; attachment lamella wide, circular, situated 3/4 along length of posterior edge. MV rectangular, slightly longer than wide, with a short rounded tooth ( Fig. 50C View FIGURE 50 ). Mandibles sclerotized; with whitish cutting plates, rectangular, with around 5 growth rings ( Fig. 50E View FIGURE 50 ).

Branchiae pectinate with up to 21 filaments, in chaetigers 7–14 ( Figs. 50A View FIGURE 50 ; 51B View FIGURE 51 ). Number of branchial filaments per chaetiger in order anterior-posterior: 20, 18, 24, 24, 21, 17, 11, 7. Basal branchial filaments slender, as long as than dorsal cirri.

First two parapodia smallest; most developed along chaetigers 3–13, following ones becoming gradually smaller. Notopodial cirri conical, slightly increasing in size from 3 (Ldc3: 1.3 mm; Ldc10: 1.4 mm), from chaetiger 24, gradually decreasing in width, in posterior region slightly shorter than anterior region ones (Ldc65: 1 mm) ( Fig. 51A–D View FIGURE 51 ). Prechaetal lobes short, as a transverse fold in all chaetigers ( Fig. 51A–D View FIGURE 51 ). Chaetal lobes in chaetigers 1– 19, rectangular, shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 20, triangular, longer than other lobes, with aciculae emerging dorsally to midline ( Fig. 51A–D View FIGURE 51 ). Postchaetal lobes well developed in chaetigers 1–35; digitiform in first 4 chaetigers, in chaetigers 5–35 conical, thinner, elongated in branchial region; decreasing in size in chaetigers 15–35, following ones inconspicuous ( Fig. 51A–D View FIGURE 51 ). Ventral cirri conical in chaetigers 1–3; in chaetigers 4–78 with oval swollen base and digitiform tip, gradually reducing in size; from chaetiger 79, conical, gradually reducing in size posteriorly ( Fig. 51A–D View FIGURE 51 ).

Aciculae sharp, with reddish basal end, distally amber ( Figs. 51A–D View FIGURE 51 ; 52F–G View FIGURE 52 ). First 24 chaetigers with 4 or 5 aciculae; in chaetigers 25–72 with 2 aciculae; from chaetiger 73, with only one acicula.

Limbate chaetae of two sizes in same chaetiger, larger in anterior region, reduced in number from about chaetiger 20. Two types of pectinate chaetae, in anterior chaetigers isodont narrow with long and slender teeth, with 2–3 pectinate, with up to 15 teeth, with transverse distal edge ( Fig. 52A View FIGURE 52 ); in median-posterior isodonts narrow with short and slender teeth, with 14–17 pectinate, with up to 18 teeth, with transverse distal edge ( Fig. 52B View FIGURE 52 ). Compound falcigers present in all chaetigers; in all chaetigers with blade of similar size (66.5–70 µm, Fig. 52C View FIGURE 52 ), all with triangular teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally. Subacicular hooks bidentate, reddish basal end, distally amber; in posterior chaetigers the reddish coloration decreases in intensity ( Fig. 52F–G View FIGURE 52 ), lighter than the acicula; starting in chaetiger 20, with one hook per chaetiger; with triangular teeth, distal tooth smaller than proximal, directed upward, proximal directed laterally ( Fig. 52E View FIGURE 52 ).

Pygidium with two pairs of anal cirri, without articulation; dorsal pair broken, in paratype ECOSUR 0 197 as long as last seven chaetigers; ventral pair short, as long as last chaetiger.

Variation. Material examined varied in following features: L10= 6–12 mm, W10= 3–5.5 mm. Twenty-five organisms were examined, of which 16 was females, 7 was males, and two lacking gametes. Thirteen complete specimens with 79 to 99 chaetigers. Palps reaching first peristomial ring or reaching second peristomial rings. Lateral and median antennae reaching second peristomial ring or reaching first chaetiger. Maxillary formula varies as follows: MII 5–8+5–8, MIII 8–10, MIV 3–5+8–12. Branchiae from chaetigers 7 to 12–15. The first and last chaetiger with branchiae were not related to the size of organisms. Maximium number of branchial filaments varied from 13 to 30 (R2= 0.44, n=25; Fig. 53A View FIGURE 53 ). Well developed postchaetal lobe in first 17–25 chaetiger (R2= 0.52, n=25; Fig. 53B View FIGURE 53 ); Ventral cirri with swollen base from chaetiger 4 to 18–23. The first and last chaetiger with ventral cirri were also not correlated with the growth of organisms. Start of subacicular hooks in chaetigers 19–24 (R2= 0.67, n=25; Fig. 53C View FIGURE 53 ).

Type Locality. Off Panama, Caribbean Sea.

Distribution. Panamanian and Colombian Caribbean, Saint Vincent and the Grenadines, and Haiti.

Etymology. The species is named after my father, Argemiro (Miro) Molina Tobón , in recognition of his teachings on love and deference for nature. The species epithet is based on his nickname, "Miro".

Remarks. This species is the longest within Paucibranchia , reaching up to 12 mm at L10, (remaining species L10= up to 6 mm).

Pauchibranchia miroi n. sp. is close to P. conferta n. comb., P. gathofi n. sp. and P. purcellana n. comb. by having compound falcigers only and aciculae reddish basally. However, P. miroi n. sp. lacks eyes and its prostomium is bilobed; whereas P. conferta n. comb. and P. gathofi n. sp. have eyes and an entire prostomium. Likewise, P. miroi n. sp. has falcigers with blades of similar size in anterior region; whereas in P. gathofi n. sp. they have blades of two sizes in the same region. Also, P. miroi n. sp. differs from P. purcellana n. comb. by having the former dorsal cirri slightly shorter in the postbranchial region, postchaetal lobe digitiform in pre-branchial chaetigers and conical in the brachial regions, and falcigers with blades of similar size in all chaetigers; whereas P. purcellana n. comb. has the dorsal cirri 1.4 times longer in postbranchial chaetigers than posterior region, postchetal lobes bluntly conical, and falcigers with blades of three sizes in anterior chaetigers. The comparison with the others Paucibranchia n. gen. species having only compound falcigers present is provided in Table 2.