Treadwellphysa villalobosi, Molina-Acevedo, 2019

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, Journal of Natural History 53 (9), pp. 517-540 : 534-538

Treadwellphysa villalobosi sp. nov.

( Figures 8 – 9 )

Material examined

Type material. Holotype ECOSUR206 ; Cabo Blanco, Cabuya, Punta Arenas, Costa Rica, Pacific Ocean; 9.586°N - 85.089°W; 10 November 2013; in volcanic rock; 1 m; coll. T. F. Villalobos-Guerrero . Paratypes ECOSUR 207 (1), LACM-AHF POLY 11 ,124 (1); same data as holotype.

Additional material. ECOSUR-P2944 (2); same data as holotype.

Description

Holotype complete, laterally dissected, with 417 chaetigers, L10 = 6 mm, W10 = 2.1 mm, TL = 135 mm. Anterior region of body with convex dorsum and flat ventrum, without groove; body depressed from chaetiger 12, widest at chaetiger 62, tapering after chaetiger 182.

Prostomium bilobed, 1.3 mm long, 2 mm wide; lobes frontally rounded; median sulcus shallow ( Figure 8 (a – c)), ventral sulcus deep ( Figure 8 (b)). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching second peristomial ring; lateral antennae reaching middle of second chaetiger; median antenna reaching third chaetiger. Palpophores and ceratophores ring-shaped, short, slender; palpostyles and ceratostyles tapering, slender, without articulation. Eyes reniform, brown, between palps and lateral antennae.

Peristomium of similar length than prostomium (1.3 mm long, 2.8 mm wide); first ring 2 times longer than second ring, separation between rings distinct dorsal and ventrally ( Figure 8 (a – c)). Ventral lip without central depression ( Figure 8 (b)).

Maxillary apparatus with MF = 1+1, 3+3, 5+0, 4+5, 1+1 ( Figure 8 (d)). Maxillary carriers 2.8 times shorter than length of MI. MI forceps-like; closing system 3.4 times shorter than length of MI; ligament between MI and MII sclerotised ( Figure 8 (d)). MII with recurved teeth; cavity opening oval, 2.9 times shorter than length of MII; ligament between MII and MIII and right MIV, sclerotised ( Figure 8 (d,e)). MIII short; with blunt teeth; with irregular attachment lamella, situated in centre of the right edge of maxilla, sclerotised ( Figure 8 (d,e)). Left MIV with three larger lateral teeth; attachment lamella semicircular, wide, better developed on left side, situated along anterior edge of maxilla ( Figure 8 (d,e)). Right MIV with two larger lateral teeth; attachment lamella semicircular, wide, better developed in central portion, situated along of anterior edge of maxilla ( Figure 8 (d)). MV square, with a short, rounded tooth ( Figure 8 (d,e)). Mandibles amber ( Figure 8 (f)); calcareous cutting plates broken, cutting plates dark, oval, with up to 11 growth rings.

Branchiae palmate with up to three filaments, in chaetigers 52 to 365R – 376L ( Figure 9 (d,e)). One filament along chaetigers 52L to 54L; two filaments along chaetigers 55L to 113L; three filaments along chaetigers 114L to 324L; two filaments along chaetigers 325L to 365L; one filament along chaetigers 366L to 376L. Branchial filaments longer than dorsal cirri ( Figure 9 (d,e)).

First four parapodia smaller; best developed in chaetigers 15 – 61, following ones becoming gradually smaller. Notopodial cirri conical, longer than ventral cirri in first 10 chaetigers, in chaetigers 11 to 38 of similar sizes, following ones gradually decreasing in size, shorter than ventral cirri ( Figure 9 (a – f)). Prechaetal lobes short, appearing as a transverse fold in all chaetigers ( Figure 9 (a – f)). Chaetal lobes in chaetigers 1 to 25 rounded, slightly shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 26 triangular, longer than other lobes, with aciculae emerging in midline ( Figure 9 (a – f)). Postchaetal lobes poorly developed in chaetigers 1 – 37, rounded in first 10 chaetigers; tapered with blunt tip, progressively decreasing in size from chaetigers 11 to 37; following ones inconspicuous ( Figure 9 (a – f)). Ventral cirri in chaetigers 1 – 4 digitiform; in chaetigers 5 to 284 with a swollen base as a transverse welt with a short digitiform tip; from chaetiger 285 digitiform, gradually decreasing in size ( Figure 9 (a – f)).

Aciculae blunt, reddish along most of the length, translucent on the distal tip ( Figure 9 (a – f)). First two chaetigers with two aciculae, chaetigers 3 – 49 with three aciculae; chaetigers 50 – 62 with two aciculae; from chaetiger 63 with only one acicula.

Limbate chaetae of two lengths in the same chaetiger, longer in the dorsal region of the parapodia, reduced in number in anterior chaetiger. Three types of pectinate chaetae; in anterior chaetigers, isodont narrow, with short and slender teeth, with 1 – 2 pectinate, with up to 16 teeth ( Figure 9 (g)); in median-posterior chaetigers, isodont wide, with short and slender teeth, with 4 – 6 pectinate, with up to 22 – 24 teeth ( Figure 9 (h,i)); in posterior chaetigers, anodont wide, with long and thick teeth, with 2 – 3 pectinate, with up to 10 – 14 teeth ( Figure 9 (h,i)). Compound spinifalciger and spiniger absent. Compound falcigers present in all chaetigers; in anterior region with blades of two lengths (longer 70 µm, Figure 9 (l,m), smaller 46 – 49 µm, Figure 9 (j,k)); with triangular teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally. In median-posterior chaetigers all blades of similar length, shorter than blades of anterior chaetigers (32 µm, Figure 9 (n)); with triangular teeth, distal tooth shorter than proximal, directed upward, proximal tooth directed laterally. Subacicular hooks bidentate, translucent, starting from chaetigers 50R – 51L, one per chaetiger; with triangular teeth, distal tooth smaller than proximal, directed upward; proximal tooth directed laterally; ( Figure 9 (o)).

Pygidium with two pairs of anal cirri, without articulation; dorsal pair as long as last three chaetigers; ventral pair short, as long as last chaetiger.

Variations

Material examined with L10 = 3.7 – 5.7 mm and W10 = 1.6 – 2.2 mm. Two specimens complete, holotype with 417 and paratype ECOSUR0000 with 271 chaetigers. Palps reaching second peristomial ring or first chaetiger. Lateral antennae reaching second or third chaetiger. Median antenna reaching third or fourth chaetiger. The maxillary formula variations are MII 2 – 3 + 3, MIII 4 – 5 , MIV 4 + 5 – 6. The proportions of the maxillary apparatus vary as follows: maxillary carriers 2.8 – 3.6 times shorter than length of MI; closing system 3.4 – 4.4 times shorter than the length of the MI; cavity opening 2.9 – 3.5 times shorter than the length of the MII. Branchiae from chaetigers 39 – 53 to 37 – 40 chaetigers before pygidium. Maximum number of branchial filaments varied from two to four. Poorly developed postchaetal lobe present in first 27 – 56 chaetigers. Ventral cirri with a swollen base from chaetigers 5 to 132 – 136 chaetigers before pygidium. Start of subacicular hooks in chaetigers 31 – 46.

Distribution

Cabo Blanco, Costa Rica (Pacific side).

Etymology

This species is named in honour of my colleague Tulio F. Villalobos-Guerrero, in recognition of his contributions to the study of errant polychaetes, especially on nereidids from the Mexican Pacific, and for collecting these specimens.

Remarks

Treadwellphysa villalobosi sp. nov. resembles T. languida , T. rizzoae sp. nov. and T. veracruzensis in having compound falcigers, whereas compound spinigers are absent. However, T. villalobosi sp. nov. lacks compound spinifalcigers, whereas in T. languida and T. veracruzensis these compound chaetae are present. Furthermore, in T. languida (holotype, L10: 4.5 mm) and T. veracruzensis (ECOSUR-OH-P675, L10: 3 mm) the branchiae start in chaetiger 60 and 35, respectively, while in T. villalobosi sp. nov. (holotype, L10: 6 mm) the branchiae start in chaetiger 52. Moreover, T. villalobosi sp. nov. differs from T. rizzoae sp. nov. in the colour, the starting chaetiger of the subacicular hooks, and the starting and ending of the branchiae (see remarks section of T. rizzoae sp. nov.). Likewise, the two species are different because T. villalobosi sp. nov. has tapered postchaetal lobes with blunt tip and the ventral cirri have a higher number of chaetigers with a swollen base, from chaetiger 5 to 284 (holotype of T. villalobosi has 417 chaetigers), whereas in T. rizzoae sp. nov. the postchaetal lobes are rounded and the ventral cirri have fewer chaetigers with a swollen base, from chaetiger 6 to 85 (holotype of T. rizzoae has 210 chaetigers).

Figures

Figure 8. Treadwellphysa villalobosi sp. nov., holotype ECOSUR206. (a) Anterior end, dorsal view; (b) anterior end, ventral view; (c) anterior end, lateral view; (d) maxillary apparatus, dorsal view, arrows indicate the elevation in the base of MII; (e) left MI–V, lateral view, arrow indicates ligament between maxillae; (f) mandibles. Scale bars: a–c = 1.5 mm; d–e = 0.6 mm; f = 0.45 mm.

Figure 9. Treadwellphysa villalobosi sp. nov. (a) Parapodium 3; (b) parapodium 14; (c) parapodium 42; (d) parapodium 104; (e) parapodium 209; (f) parapodium 394; (g) chaetiger 20, isodont pectinate narrow, with short and slender teeth; (h) chaetiger 249, isodont pectinate wide, with short and slender teeth; (i) chaetiger 249, anodont pectinate wide, with long and thick teeth; (j) chaetiger 17, compound falciger with short blade; (k) chaetiger 8, compound falciger with short blade; (l) chaetiger 10, compound falciger with long blade; (m) chaetiger 8, compound falciger with long blade; (n) chaetiger 249, compound falciger with short blade; (o) chaetiger 40, subacicular hook. a–f, k, m from holotype ECOSUR206; g, j, l from paratype ECOSUR207; h, i, n, o from paratype ECOSUR00000. Scale bars: a, f = 80 µm; b–e = 0.16 mm; g = 3.5 µm; h = 8.4 µm; i = 7.2 µm; j = 9.7 µm; k, m = 14 µm; l, n = 5.7 µm; o = 16 µm. All parapodia in anterior view.