Marphysa brevibranchiata Treadwell, 1921

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 : 12-15

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 brevibranchiata Treadwell, 1921
status

Treatment

Marphysa brevibranchiata Treadwell, 1921 View in CoL n. status

Figures 4 View FIGURE 4 , 9D View FIGURE 9 , Table 1

Marphysa acicularum var. brevibranchiata Treadwell, 1921: 60–61 View in CoL , Pl. 5, Figs. 5–8 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 , text-figs. 194–200.

Marphysa sanguinea View in CoL . — Hartman 1944a: 128 (non Montagu, 1813).

Material examined. Type material: Lectotype AMNH 1358 About AMNH designated here , Paralectotypes (3 specimens) AMNH _ IZC 00361334 About AMNH , Bermuda, 1916, coll. A. Treadwell.

Description. Lectotype complete, dissected ventrally, with 289 chaetigers, L10 = 11.5 mm, W10 = 3.6 mm; TL: 172 mm. Last 28 chaetigers regenerating. Anterior region of the body with dorsum convex and flat ventrum; body depressed from chaetiger 7, widest at chaetiger 22, tapering after chaetiger 40.

Prostomium bilobed, 1.7 mm long, 2.6 mm wide; lobes frontally truncated; with median sulcus shallow anteriorly and deep ventrally ( Fig. 4 View FIGURE 4 A–B). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching second peristomial ring; lateral antennae reaching first chaetiger; median antenna reaching middle of the first chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles tapering, slender. Eyes not observed.

Peristomium (2.3 mm long, 3.8 mm wide) larger than prostomium; first ring two times longer than second ring; separation between rings distinct on all sides ( Fig. 4 View FIGURE 4 A–B). Ventral lip dissected, in paralectotype L10 = 12.4 mm, with a slight central anterior depression and a couple of shallow wrinkles ( Fig. 4B View FIGURE 4 ).

Maxillary apparatus with MF = 1 + 1, 6 + 6, 8 + 0, 3 + 9, 1 + 1 according to Treadwell, 1921: 61. In paralectotype with MF = 1 + 1, 6 + 5, 7 + 0, 3 + 9, 1 + 1 ( Fig. 4D View FIGURE 4 ). MI 2.8 times longer than length of maxillary carriers. MI forceps-like, MI five times longer than length of closing system ( Fig. 4 View FIGURE 4 D–E); ligament between MI and MII sclerotized. MII with recurved triangular teeth; MII 3.8 times longer than length of cavity opening ( Fig. 4 View FIGURE 4 D–E); ligament between MII and MIII and right MIV, slightly sclerotized. MIII with triangular teeth; with irregular attachment lamella, situated in center of the right edge of the plate, slightly sclerotized ( Fig. 4 View FIGURE 4 D–E). Left MIV with second lateral tooth larger than rest; attachment lamella rectangular, wide, better developed in left side, situated 2/3 of anterior edge of maxilla, sclerotized. Right MIV with teeth of similar size; attachment lamella semicircle, wide, better developed in left, situated 2/3 of anterior edge of maxilla, sclerotized ( Fig. 4 View FIGURE 4 D–E). MV square with a short, rounded tooth. Mandibles dark; calcareous cutting plates broken, sclerotized cutting plates brown, oval, up to 25 growth rings ( Fig. 4F View FIGURE 4 ) .

Pectinate branchiae up to seven short filaments, present from chaetigers 28 to 277 ( Fig. 4J View FIGURE 4 ). First and last 17 chaetigers with one filament; reaching the maximum seven filaments in chaetigers 123L–257L ( Fig. 9D View FIGURE 9 ). Branchial filaments longer than dorsal cirri except in the last branchiae. In paralectotype without regeneration posterior region, branchiae ending at six chaetigers before pygidium.

First four parapodia smaller, best developed in chaetigers 6–83, following ones becoming gradually smaller. Dorsal cirri conical, longer than ventral cirri in anterior chaetigers, of similar size in the following ones; best developed in chaetigers 2–25, following ones gradually smaller ( Fig. 4 View FIGURE 4 G–K). Prechaetal lobes short, as transverse folds in all chaetigers ( Fig. 4 View FIGURE 4 G–K). Chaetal lobes in first 44 chaetigers rounded, shorter than postchaetal lobe, with aciculae emerging dorsal to midline; from chaetiger 45 triangular, longer than other lobes, with acicula emerging in midline ( Fig. 4 View FIGURE 4 G–K). Postchaetal lobes well developed in the first 50 chaetigers; digitiform in the first four chaetigers, rounded from chaetiger 5, progressively smaller from chaetiger 19; chaetiger 51 inconspicuous ( Fig. 4 View FIGURE 4 G–K). Ventral cirri digitiform in the first five chaetigers; chaetigers 6 to 260 with an oval swollen base and digitiform tip; digitiform from chaetiger 261, gradually reducing in size ( Fig. 4 View FIGURE 4 G–K).

Aciculae blunt, reddish along most of its length, amber on the distal tip ( Fig. 4 View FIGURE 4 G–K). First 20 chaetigers with three aciculae; in chaetigers 21–147 with two aciculae; from chaetiger 148 with only one acicula.

Limbate chaetae with two lengths in same chaetiger: long and short, long blades in dorsal position, short blades in ventral position; limbate chaetae reduced in number around chaetiger 28, and then maintained a similar number until the posterior end. Four types of pectinate chaetae; in anterior-median chaetigers, thin, isodont narrow, symmetric, with long, and slender teeth, 1–2 chaetae, with up to 14 teeth ( Fig. 4N View FIGURE 4 ); in median-posterior chaetigers, thick, isodont wide, asymmetric, with short and slender, 1–2 chaetae with up to 40 teeth ( Fig. 4L View FIGURE 4 ); in posterior chaetigers, thick, anodont wide, symmetric, with long and slender teeth, 1–2 chaetae, up to nine teeth ( Fig. 4M View FIGURE 4 ), and thick, anodont wide, symmetric, with short and thick teeth, 1–2 chaetae, up to 16 teeth ( Fig. 4O View FIGURE 4 ). Compound spinigers present throughout; in anterior chaetigers with blades of three lengths in the same chaetiger: shorter and median blades more abundant than longer blades ( Fig. 4P View FIGURE 4 ); in median-posterior chaetigers with blades of two lengths. Subacicular hooks unidentate, translucent; starting from chaetigers 35L–36R, one or two per chaetiger (second replacement hook); present continuously in all chaetigers ( Fig. 4Q View FIGURE 4 ).

Pygidium with dorsal pair of anal cirri as long as the last 10 chaetigers; ventral pair short, as long as the last four chaetigers ( Fig. 4C View FIGURE 4 ).

Variation. Material examined with L10 = 11.5–14.2 mm, W10 = 3.4–4 mm, TChae = 289–310. Median antenna reaching middle of first or second chaetiger. The maxillary formula is variable: MII 6 + 5–6, MIII 7, MIV 3–4 + 9. The proportions of the maxillary apparatus vary as follows: MI are 2.7–2.8 times longer than the length of the maxillary carriers; MI are 4.5–5 times longer than the length of the closing system; MII are 3.3–3.8 times longer than the length of the cavity opening. Branchiae start from chaetigers 28–36 and end 6–12 chaetigers before pygidium. Maximum number of branchial filaments varied from seven to eight and postchaetal lobes were conspicuous in first 50–75 chaetigers. Ventral cirri with a swollen base start from chaetigers 5–6 to 128–168 chaetigers before the pygidium. Subacicular hooks start from chaetigers 36–46.

Distribution. Bermuda, Atlantic Ocean.

Habitat. According to Treadwell (1921), M. brevibranchiata co-occurred with M. acicularum in Flatts Inlet , Ely’s Harbor, and Fairyland Creek, Bermuda, in the intertidal region of muddy flats.

Remarks. Treadwell (1921) studied some specimens that were morphologically close to M. acicularum collected by himself, from several locality of Bermuda. According to his description, the specimens presented minor differences from M. acicularum in the branchiae and maxillary apparatus shape, which he attributed to a variation on these characters. For this reason, Treadwell assigned his Bermuda specimens as the variety M. acicularum brevibranchiata . Several years later, Hartman (1944a) suggested this subspecies, like other three species from the Grand Caribbean ( M. acicularum , M. nobilis and M. viridis ), were junior synonyms of M. sanguinea ( England) . Nonetheless, Molina-Acevedo & Carrera-Parra (2015) reinstated the three Marphysa species; but not M. a. brevibranchiata because the type material was not found at the USNM, as reported by Hartman (1956). Herein, the syntypes were finally found in the general collection at the AMNH, where most of the Treadwell’s species were deposited. The specimen used for the description of M. a. brevibranchiata was identified and proposing as lectotype, the rest of the material is considering as paralectotypes (ICZN 1999, Art. 74F).

Treadwell correctly highlighted the differences between M. acicularum and the subspecies M. a. brevibranchiata . The first species has a low number of teeth in MIV (6–7), and the branchial filaments are long, whereas M. a. brevibranchiata has more teeth on the right MIV (9), and the branchial filaments are short. On the other hand, in M. acicularum (L10 = 4–15.8 mm), the branchiae start from chaetigers 22–27, there are 2–5 branchial filaments, the postchaetal lobe is developed in anterior chaetigers (first 28–56 chaetigers), and the ventral cirri with swollen base end 13 chaetigers before pygidium or in the last chaetiger; in constrat of M. a. brevibranchiata (L10 = 11.5–14.2 mm) that the branchiae start from chaetigers 28–36, with up to 7–8 branchial filaments, the postchaetal lobe is developed in more chaetigers (first 50–75 chaetigers), and the ventral cirri with swollen base end 128–168 chaetigers before of pygidium. Hence, both are considered unique species, the subspecies M. acicularum brevibranchiata is raised to species status.

Marphysa brevibranchiata n. status (L10 = 4–15.8 mm) differs from M. sanguinea (neotype and additional material, L10 = 11.5–20.4 mm) because in the former the branchiae start from chaetigers 22–27, branchial filaments are short, there are two types of anodont pectinate, and the subacicular hook is translucent. In contrast, in M. sanguinea the branchiae start from chaetigers 21–25, only one type of anodont pectinate are present, the branchial filaments are longer, and the subacicular hook is reddish basally and translucent distally. Based on these visual differences, we conclude that M. brevibranchiata n. status is a valid species and different from M. sanguinea .

Marphysa brevibranchiata n. status resembles M. aransensis Treadwell, 1939 , M. kristiani , and M. sebastiana Steiner & Amaral, 2000 by having short branchial filaments, the absence of limbate subacicular chaetae, and the translucent subacicular hook. However, M. brevibranchiata n. status has only pectinate branchiae, in contrast to M. kristiani that has pectinate and palmate branchiae in some regions of the body, and M. sebastiana only has palmate branchiae. Moreover, M. brevitentaculata has the postchaetal lobe digitiform in the first four chaetigers, whereas in M. aransensis , the postchaetal lobe is rounded in the first chaetigers. The comparison of M. brevibranchiata n. status with the related species is provided in Table 1.