Marphysa americana Monro, 1933

Molina-Acevedo, Isabel C. & Idris, Izwandy, 2020, Reinstatement of species belonging Marphysa sanguinea complex (Annelida Eunicidae) and description of new species from the mid-Pacific Ocean and the Adriatic Sea, Zootaxa 4816 (1), pp. 1-48 : 4-5

publication ID	https://doi.org/ 10.11646/zootaxa.4816.1.1
publication LSID	lsid:zoobank.org:pub:0475E09C-792F-4F55-9F1F-C85B8A6E44AD
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scientific name	Marphysa americana Monro, 1933
status

Treatment

Marphysa americana Monro, 1933 View in CoL n. status

Figures 1 View FIGURE 1 , 9A View FIGURE 9 , Table 1

Marphysa sanguinea var. americana Monro, 1933: 68–69 View in CoL , Text-figs. 28.

Marphysa sanguinea americana View in CoL . — Fauchald 1970: 64–66.

Marphysa sanguinea View in CoL . — Fauchald 1977: 42 (non Montagu, 1913).

Material examined. Type material: Holotype BNHM 1932.12.24.554-556, Pacific Expedition 1923–1924, sta. Balboa 2, St. George , Balboa, Panama, Pacific Ocean, coll. C. Crossland.

Description. Holotype complete, laterally dissected, with 390 chaetigers, broken in three parts (anterior fragment with 183 chaetigers, median fragment with 87 chaetigers, posterior fragment with 120 chaetigers), all three parts belong to the same individual, L10 = 12 mm, W10 = 5.8 mm, TL = 278 mm. Last 53 chaetigers regenerating. Anterior region of the body with dorsum convex and flat ventrum, without groove; body depressed from chaetiger 9, widest at chaetiger 50, tapering after chaetiger 116.

Prostomium bilobed, 2.3 mm long, 4 mm wide; lobes frontally rounded; median sulcus shallow anteriorly and deep ventrally ( Fig. 1 View FIGURE 1 A–B). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching middle of first peristomial ring; lateral antennae reaching second peristomial ring; median antenna reaching first chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles tapering, slender. Eyes ovate, brown, between palps, and lateral antennae.

Peristomium (3.2 mm long, 7.2 mm wide) larger and wider than prostomium; first ring two times longer than second ring, separation between rings distinct only dorsal, and ventrally ( Fig. 1 View FIGURE 1 A–B). Ventral lip with a slight central anterior depression and several shallow wrinkles ( Fig. 1B View FIGURE 1 ).

Maxillary apparatus with MF = 1 + 1, 5 + 4, 7 + 0, 3 + 9, 1 + 1 ( Fig. 1D View FIGURE 1 ). MI 3.2 times longer than length of maxillary carriers. MI forceps-like, MI five times longer than length of closing system ( Fig. 1D View FIGURE 1 ); ligament between MI and MII strongly sclerotized. MII with recurved triangular teeth; MII three times longer than length of cavity opening ( Fig. 1 View FIGURE 1 D–E); ligament between MII and MIII and right MIV, slightly sclerotized. MIII with triangular teeth; with irregular attachment lamella, situated in center of right edge of the plate, slightly sclerotized ( Fig. 1D View FIGURE 1 ). Left MIV with three laterals teeth larger than rest; attachment lamella rectangular, wide, better developed in left side, situated 2/3 of anterior edge of maxilla, sclerotized. Right MIV with three laterals teeth larger than rest; attachment lamella rectangular, wide, better developed in central side, situated 2/3 of anterior edge of maxilla, sclerotized ( Fig. 1 View FIGURE 1 D–E). MV rectangular, with a short triangular tooth. Mandibles dark; calcareous cutting plates broken, sclerotized cutting plates brown, with up to 25 growth rings ( Fig. 1F View FIGURE 1 ).

Pectinate branchiae with up to 12 long filaments, present from chaetigers 45L–47R to 362L–361R ( Fig. 1J View FIGURE 1 ). First pair with two filaments and last 18 chaetigers with one filament; reaching the maximum 11 or 12 filaments in chaetigers 93L to 121L ( Fig. 9A View FIGURE 9 ). Branchial filaments longer than dorsal cirri except in first and last five branchiae.

First three parapodia smaller, best developed in chaetigers 6–53, following ones gradually smaller. Dorsal cirri conical, longer than ventral cirri in anterior chaetigers, similar length in median and posterior ones; best developed in chaetigers 6–57, following ones gradually smaller ( Fig. 1 View FIGURE 1 G–K). Prechaetal lobes short, as transverse folds in all chaetigers ( Fig. 1 View FIGURE 1 G–K). Chaetal lobes in the first 40 chaetigers rounded, shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 41 triangular, longer than other lobes, with acicula emerging in midline ( Fig. 1 View FIGURE 1 G–K). Postchaetal lobes well developed in first 92 chaetigers; conical in first six chaetigers, rounded in chaetigers 7–34, progressively smaller from chaetiger 34; from chaetiger 93 inconspicuous ( Fig. 1 View FIGURE 1 G–K). Ventral cirri digitiform in first four chaetigers; in chaetigers 5 to 345 with an oval swollen base and blunt tip; conical from chaetiger 346, gradually reducing in size ( Fig. 1 View FIGURE 1 G–K).

Aciculae blunt, reddish along most of its length, amber on the distal tip ( Fig. 1 View FIGURE 1 K–J). First chaetiger with three aciculae; in chaetigers 2–41 with five; in chaetigers 42–51 with four; in chaetigers 52–129 with three; from chaetigers 130 with two aciculae.

Limbate chaetae of two lengths in same chaetiger: long and short, long blades are in dorsal region, short blades in ventral position; limbate chaetae reduced in number around chaetiger 27, and then maintained a similar number until the posterior end. Four types of pectinate chaetae; in anterior chaetigers, thin, isodont narrow, asymmetric, with long and slender teeth, with 3–4 pectinate, with up to 12 teeth ( Fig. 1M View FIGURE 1 ); in median-posterior chaetigers, thick, isodont wide, symmetric, with short and slender teeth, with 3–4 pectinate with up to 16 teeth ( Fig. 1N View FIGURE 1 ), and thick, isodont wide, asymmetric, with long and thick teeth, with 2–3 pectinate, with up to 16 teeth ( Fig. 1O View FIGURE 1 ); in posterior chaetigers, thick, anodont wide, asymmetric, with long and thick teeth, with 1–2 pectinate, with up to 11 teeth ( Fig. 1P View FIGURE 1 ). Compound spinigers present throughout; in anterior chaetigers with blades of two lengths: shorter bladed slightly more abundant than longer blades ( Fig. 1L View FIGURE 1 ); in median-posterior chaetigers with blades of similar length. Subacicular hooks bidentate, reddish along most of its length, translucent on the distal tip; present only in chaetigers 117, 140, 149, and in regenerating region; blunt teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally ( Fig. 1Q View FIGURE 1 ).

Pygidium with dorsal pair of anal cirri as long as last eight chaetigers; ventral pair short, as long as last two chaetigers.

Distribution. Balboa, Panama, Pacific Ocean.

Habitat. The specimen was found in Balcoa dock, in shore-pools at low tide. The author did not specify the type of sediment.

Remarks. Monro (1933) studied the speciemens collected by Crossland in The Expedition of the S.Y. San George, specifically from the area of Balboa Docks Panama, Taboga and Perlas Islands. The material collected in this expedition was deposited in the British Museum.

Monro (1933) observed a single specimen accompanied by a long fragment of Onuphis magna ( Andrews, 1891) placed in the same container by Crossland. Monro compared his Panama specimen with the material of M. sanguinea available in the collection of the British Museum and concluded that both are similar in the branchiae through the body and the compound spinigers in all chaetigers. Monro also clarified that the main difference was the number of branchial filaments (12 filaments for Panama specimen and six filaments for M. sanguinea ); however, he attributed this to the size variation of the organisms and designated the Panamanian specimen as the M. sanguinea americana variety (= subspecies, see ICZN Art. 45.6.3–4). Fauchald (1970, 1977) commented that the number of branchial filaments in M. sanguinea could be variable (between 4 and 10 filaments); therefore, the subspecies described for Panama is not different from the original British form.

Herein, we find that the subspecies M. sanguinea americana (L10: 12 mm) differs from M. sanguinea (L10: 11.5–20.4 mm) by having branchiae from chaetiger 45; higher number of filaments (12); postchaetal lobe developed in more number of chaetiger (in 92 anterior chaetigers); and by the conical shape of the postchaetal lobe in first four chaetigers of the body. However, in M. sanguinea the branchiae start from chaetigers 21–25, a lower number of branchial filaments (5–6) are found, the postchaetal lobe is developed only in first 50–70 chaetigers of the body, and the postchaetal lobe is digitiform in the first four chaetigers of the body. Additionally, both taxa have differences in the number of thick and wide pectinate isodont chaetae per chaetiger. The Panama specimen has only three or four chaetae, whereas in M. sanguinea has between 18 and 20 pectinates. In view of these differences, the taxa are considered herein different species, and it is proposed to raise the subspecies proposed by Monro to the level of species.

Marphysa americana n. status resembles M. depressa ( Schmarda, 1861) ( New Zealand), M. emiliae Molina- Acevedo & Carrera-Parra, 2017 (Yucatan, Mexico), M. teretiuscula ( Schmarda, 1861) ( Sri Lanka), and M. tripectinata (Beihai, China) by having subacicular hook bidentate and reddish along most of its length. However, M. americana n. status has postchaetal lobes which are conical in first four chaetigers of the body; in contrast, M. depressa and M. emiliae have digitiform postchaetal lobes, and M. teretiuscula and M. tripectinata , have ovoid-shaped postchaetal lobes in the first four chaetigers of the body. Also, M. americana n. status has branchiae pectinate with a well-defined main axis in most segments, whereas in M. teretiuscula and M. tripectinata , in some regions of the body, the main axis are poorly developed, similar to palmate form. On the other hand, in M. americana n. status, there are only one type of anodont pectinate in posterior region, whereas in M. teretiuscula and M. emiliae there are two types of anodont pectinate in the same region. Moreover, M. americana n. status (Ll0 = 12 mm) has up 12 brachial filaments, whereas in M. depressa (L10 = 4.2–11.5 mm), there are only 2–4 branchial filaments. The comparison of M. americana n. status with the related species is provided in Table 1.