Treadwellphysa mixta Molina-Acevedo 2019
Creators: name: Molina-Acevedo, Isabel C.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Eunicida
Eunicidae
Treadwellphysa
Treadwellphysa mixta

description: Treadwellphysa mixta (Fauchald, 1970), comb. nov.
(Figures 3 – 4)
Marphysa mixta Fauchald, 1970: 61 – 63, pl. 9, figs a – h; Ruiz-Cancino et al. 2010: 43 – 44, figs 9a – k, 16G
Material examined
Type material. Holotype LACM-AHF POLY 286; Tangola Tangola Bay (Tangolunda bay), Gulf of Tehuantepec, Oaxaca, Mexico; R / V VELERO III sta. 4 – 33; 15.75°N -96.1°W; 6 January 1933; in shore, hand; coll. Allan Hancock Foundation.
Additional material. LACM-AHF POLY 6945 (1); SE side of bay, San Lorenzo Rocks and rocks opposite Farralon de Obispo, Acapulco, Mexico, Pacific Ocean; 16.855°N - 99.886°W; Sta. Dawson 123,1946 – 47 sta. 123; 2 February 1947; coll. E. Yale Dawson. ECOSUR-OH- P00071 (1), ECOSUR-OH-P00073 (1), ECOSUR-OH-P00078 (1); Las Escolleras beach, Puerto Madero, Chiapas, Mexico, Pacific Ocean; 14.704°N - 92.407°W; 11 April 2008; in oyster crassostrea prismatica; coll. S.I. Salazar-Vallejo and L.F. Carrera-Parra. ECOSUR-OH-P00075 (1), ECOSUR-OH-P00077 (1), ECOSUR-OH-P00080 (1); Las Escolleras beach, Puerto Madero, Chiapas, Mexico, Pacific Ocean; 14.704°N - 92.407°W; 11 April 2008; in sabellarid reef; coll. S.I. Salazar-Vallejo and L.F. Carrera-Parra.
Description
Holotype complete, with 352 chaetigers, L10 = 7.7 mm, W10 = 3.5 mm TL = 130 mm. Anterior region of body with convex dorsum and flat ventrum, without groove; body depressed from chaetiger 6, widest at chaetiger 11, tapering after chaetiger 22.
Prostomium bilobed, 1.5 mm long, 2 mm wide; lobes frontally rounded; median sulcus shallow (Figure 3 (a – c)), ventral sulcus deep (Figure 3 (b)). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching second peristomial ring; lateral antennae reaching second chaetiger; median antenna reaching middle of second chaetiger. Palpophores and ceratophores ring-shaped, short, slender; palpostyles and ceratostyles tapering, thick, without articulation. Eyes oval, brown, between palps and lateral antennae.
Peristomium larger than prostomium (1.6 mm long, 2.7 mm wide), first ring 2 times longer than second ring, separation between rings distinct on all sides (Figure 3 (a – c)). Ventral lip with a slight central depression and a couple of shallow wrinkles (Figure 3 (b)).
Maxillary apparatus not examined in holotype, in additional specimen (LACM-AHF POLY 6945) with MF = 1+1, 4+4, 5+0, 4+7, 1+1 (Figure 3 (e)). Maxillary carriers 3 times shorter in length than MI. MI forceps-like; closing system 3.5 times shorter than length of MI; ligament between MI and MII sclerotised (Figure 3 (e – f)). MII with recurved teeth; cavity opening oval, 2 times shorter than length of MII; ligament between MII and MIII and right MIV, sclerotised (3E – F). MIII short; with triangular teeth; with irregular attachment lamella, situated in centre of right edge of maxilla and reaching the base of MIV, sclerotised (Figure 3 (e,f)). Left MIV with two larger lateral teeth; attachment lamella semicircle, slender, better developed on left side, situated 2/3 along anterior edge of maxilla (Figure 3 (e,f)). Right MIV with three larger lateral teeth; attachment lamella semicircle, slender, better developed on right side, situated along anterior edge (Figure 3 (e,f)). MV square, with a short rounded tooth (Figure 3 (e,f)). Mandibles dark (Figure 3 (d)); calcareous cutting plates broken, cutting plates amber, oval, with up to 10 growth rings.
Branchiae pectinate with up to five filaments, in chaetigers 35 to 304L – 303R (Figure 4 (d,e)). Two filaments along chaetigers 35 to 47L; three filaments along chaetigers 48L to 58L; four filaments along chaetigers 59L to 110L; five filaments along chaetigers 111L to 223L; four filaments along chaetigers 224L to 242L; three filaments along chaetigers 243L to 257L; two filaments along chaetigers 258L to 280L; one filament along chaetigers 282L to 303L – 304R. Branchial filaments longer than dorsal cirri (Figure 4 (d,e)).
First two parapodia smaller; best developed in chaetigers 4 – 18, following ones becoming gradually smaller. Notopodial cirri conical, longer than ventral cirri in first 35 chaetigers, following ones gradually decreasing in size, shorter than ventral cirri (Figure 4 (a – f)). Prechaetal lobes short, as a transverse fold in all chaetigers (Figure 4 (a – f)). Chaetal lobes in chaetigers 1 to 38 rounded, of similar size to postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 39 triangular, longer than other lobes, with acicula emerging in midline (Figure 4 (a – f)). Postchaetal lobes poorly developed in chaetigers 1 – 33, conical in first six chaetigers, rounded and progressively decreasing in size from chaetiger 7 to 33; following ones inconspicuous (Figure 4 (a – f)). Ventral cirri in chaetigers 1 – 3 digitiform; in chaetigers 4 to 272 with a swollen base as a transverse welt with a short digitiform tip; from chaetiger 273 conical, gradually decreasing in size (Figure 4 (a – f)).
Aciculae blunt, reddish along most of its length, amber on the distal tip (Figure 4 (a – d)); in posterior chaetigers with distal end translucent (Figure 4 (e,f)). First 20 chaetigers with two or three aciculae; chaetigers 21 – 46 with two; from chaetiger 47 with only one acicula.
Limbate chaetae of two lengths in the same chaetiger, longer in dorsal region of the parapodia, reduced in number around chaetiger 20. Three types of pectinate chaetae; in anterior chaetigers, isodont narrow, with short and slender teeth, with 1 – 2 pectinate, with up to 17 – 18 teeth (Figure 4 (g)); in median-posterior chaetigers, isodont wide, with short and slender teeth, with 5 – 6 pectinate, with up to 19 – 20 teeth (Figure 4 (h)); in posterior chaetigers, anodont wide, with long and thick teeth, with 2 – 3 pectinate, with up to 10 – 11 teeth (Figure 4 (i)). Compound spinifalciger absent. Compound spinigers present in first 50 chaetigers, with blades of two lengths in the same chaetiger, longer ones (Figure 4 (k)) less abundant than short ones (Figure 4 (j)) present until chaetiger 31. Compound falcigers in all chaetigers; in anterior-median region with blades of similar length (57 µm, Figure 4 (l)), more abundant than spinigers; all with triangular teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally. In posterior chaetigers, falcigers with all blades of similar length (48 µm, Figure 4 (m)), shorter than in anterior-median region; all with triangular teeth, distal tooth smaller than proximal, directed upward, proximal tooth directed laterally. Subacicular hooks bidentate, reddish along most of its length, translucent on the distal tip, in median-posterior chaetiger with the lightest reddish colour; starting in chaetigers 37R – 40L, one per chaetiger, except for replacement; with triangular teeth, distal tooth smaller than proximal, directed upward, proximal tooth directed laterally (Figure 4 (n)).
Pygidium with two pairs of anal cirri, without articulation; dorsal pair as long as last eight chaetigers; ventral pair short, as long as last chaetiger.
Variations
Material examined with L10 = 3.3 – 8 mm and W10 = 1.4 – 3.5 mm. Two specimens complete with 165 and 352 chaetigers. Palps reaching middle of first peristomial ring or second chaetiger. Lateral antennae reaching middle of second peristomial ring or second chaetiger. Median antenna reaching first or third chaetiger. The maxillary formula variations are MII 3 – 4 +4, MIII 4 – 5, MIV 4 – 5+6 – 8. The proportions of the maxillary apparatus vary as follows: the maxillary carriers are 2.3 – 3.3 times shorter than the length of the MI; the closing system is 3.8 – 4.5 times shorter than the length of the MI; the cavity opening is 2 – 3 times shorter than the length of the MII. Branchiae from chaetigers 20 – 35 to 3 – 48 chaetigers before pygidium. Maximum number of branchial filaments varied from three to five. Poorly developed postchaetal lobe present in first 23 – 61 chaetigers. Ventral cirri with a swollen base from chaetigers 4 – 5 to 58 – 80 chaetigers before the pygidium. Start of subacicular hooks from chaetigers 22 – 37. Compound spinigers present only in first 25 – 55 chaetigers.
Distribution
From Chiapas to Guerrero, Mexican Pacific.
Remarks
Treadwellphysa mixta comb. nov. resembles T. amadae, T. dartevellei comb. nov. and T. yucatanensis in the presence of compound falcigers and spinigers. However, T. mixta comb. nov. lacks compound spinifalcigers; while in T. amadae and T. yucatanensis chaetae of this kind are present. In addition, T. mixta comb. nov. has a conical postchaetal lobe in first chaetigers and it is of similar size to the chaetal lobe, whereas T. amadae has a rounded postchaetal lobe, 2 times longer than the chaetal lobe. In T. mixta comb. nov. (holotype, L10 = 7.7 mm) the branchiae start in chaetiger 35, whereas in T. yucatanensis (holotype, L10 = 5.6 mm) the branchiae start in chaetiger 53. On the other hand, T. mixta comb. nov. has compound spinigers only in the anterior region (first 25 – 55 chaetigers) and falcigers in all chaetigers, while in T. dartevellei comb. nov. spinigers are present in all chaetigers and falcigers start from chaetigers 30 – 54. Besides, in T. mixta comb. nov. (holotype, L10 = 7.7, 352 chaetigers) the branchiae end 3 – 48 chaetigers before the pygidium and the postchaetal lobes are developed in the first 52 chaetigers, whereas T. dartevellei comb. nov. (BMNH 1939.7.17.23 – 24, L10 = 7.2, 158 chaetigers) has branchiae to the last chaetiger and its postchaetal lobes are developed in the first 25 chaetigers.
description: Published as part of Molina-Acevedo, Isabel C., 2019, Redescription of two species previously regarded as Marphysa de Quatrefagesı 1865 ı with the description of new species of Treadwellphysa Molina-Acevedo and Carrera-Parraı 2017, pp. 517-540 in Journal of Natural History 53 (9) on pages 525-529, DOI: 10.1080/00222933.2019.1596328, http://zenodo.org/record/3675703