Treadwellphysa dartevellei (Monro, 1936), 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 : 521-525

Treadwellphysa dartevellei (Monro, 1936) , comb. nov.

( Figures 1 – 2 )

Marphysa dartevellei Monro, 1936: 246 – 248 , figs a – f; Fauvel and Rullier 1959: 169; Amoureux 1973: 57 – 58

Material examined

Type material. Holotype British Museum of Natural History ( BMNH) 1935.1.29.1 – 2; 85 km. North of Banana, Cape Malembo, Cabinda, Angola, Africa , Atlantic Ocean ; 1933; on rock bored by Lithodomus sp.

Additional material. BMNH 1939.7.17.23 – 24 (3); Cacongo (formerly Landana), Angola, Africa. BMNH 2013233 (1); Ghana, Africa. LACM-AHF POLY 11098 (3) Paradise beach, Ada Foah, east of Pranpram, Greater Accra Region; Ghana, Africa ; 5.776°N -0.647°W; 18 September 1964; coll. Björn Berland .

Description

Holotype incomplete, laterally dissected, with 105 chaetigers, L10 = 10.2 mm, W10 = 5 mm, TL = 66 mm. Anterior region of body with convex dorsum and flat ventrum, without groove; body depressed from chaetiger 10, widest at chaetiger 33, tapering after chaetiger 45.

Prostomium bilobed, 1.8 mm long, 3 mm wide; lobes frontally rounded; median sulcus shallow ( Figure 1 (a – c)), ventral sulcus deep ( Figure 1 (b)). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching second peristomial ring; lateral antennae reaching middle of first chaetiger; median antenna broken, in additional specimen (LACM-AHF N10965 , L10 = 10.5 mm) reaching middle of second chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles tapering, slender, without articulation. Eyes rounded, brown, between palps and lateral antennae.

Peristomium larger than prostomium (2.1 mm long, 5.2 mm wide); first ring 2 times longer than second ring, separation between rings distinct on all sides ( Figure 1 (a – c)). Ventral lip with a slight central depression and a couple of shallow wrinkles ( Figure 1 (b)).

Maxillary apparatus with MF = 1+1, 3+4, 4+0, 5+6, 1+1 ( Figure 1 (d)). Maxillary carriers 4.1 times shorter than length of MI. MI forceps-like; closing system 5.8 times shorter than length of MI; ligament between MI and MII sclerotised ( Figure 1 (d,e)). 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 1 (d,e)). MIII short; with blunt teeth; with irregular attachment lamella, situated in centre of right edge of maxilla, sclerotised ( Figure 1 (d,e)). Left MIV with two larger lateral teeth; attachment lamella semicircular, slender, better developed on left side, situated 2/3 of anterior edge of maxilla ( Figure 1 (d,e)). Right MIV with two larger lateral teeth; attachment lamella semicircular, wide, better developed on the right side, situated along posterior edge ( Figure 1 (d)). MV rectangular, with a short rounded tooth ( Figure 1 (d,e)). Mandibles brown ( Figure 1 (f)); calcareous cutting plates broken, cutting plates brown, oval, with up to 10 growth rings.

Branchiae palmate with up to four filaments, present from chaetiger 35 until last parapodium of fragment ( Figure 2 (d – f)). One filament along chaetigers 35L to 38L; three filaments along chaetigers 39L to 53L; four filaments from chaetiger 54L to end of fragment. Branchial filaments longer than dorsal cirri ( Figure 2 (d – f)).

First three parapodia smaller; best developed in chaetigers 5 – 39, following ones becoming gradually smaller. Notopodial cirri conical, longer than ventral cirri in first 15 chaetigers, following ones gradually decreasing in size, shorter than ventral cirri ( Figure 2 (a – f)). Prechaetal lobes short, as a transverse fold in all chaetigers ( Figure 2 (a – f)). Chaetal lobes in chaetigers 1 – 33 rounded, of similar size to postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 34 triangular, longer than other lobes, with acicula emerging in midline ( Figure 2 (a – f)). Postchaetal lobes poorly developed in chaetigers 1 – 25, conical in first four chaetigers, rounded from chaetiger five; progressively decreasing in size from chaetigers 8 to 25; following ones inconspicuous ( Figure 2 (a – f)). Ventral cirri in chaetigers 1 – 4 digitiform; in chaetigers 5 to end of the fragment with a swollen base as a transverse welt with a short digitiform tip, gradually decreasing in size ( Figure 2 (a – f)). In complete specimen (BMNH 1939.7.17.23 – 24, L10 = 7.2 mm, 158 chaetigers) in chaetigers 5 – 91 with a swollen base as a transverse welt with short digitiform tip; from chaetiger 92 digitiform, gradually decreasing in size.

Aciculae blunt, reddish along most of the length, amber on the distal tip ( Figure 2 (a – e)); in additional specimen (BMNH 1939.7.17.23 – 24) last chaetigers with two aciculae, one amber, and the second darker ( Figure 2 (f)). First three chaetigers with three aciculae, chaetigers 4 – 28 with four, chaetigers 29 – 33 with three, chaetigers 34 – 101 with two, from chaetiger 102 with only one acicula ( Figure 2 (a – e)).

Limbate chaetae of two lengths in the same chaetiger, longer in 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 2 (g)); in median-posterior chaetigers, isodont wide, with long and slender teeth, with 5 – 8 pectinate, with up to 20 – 22 teeth ( Figure 2 (h)); in posterior chaetigers, anodont wide, with long and thick teeth, with 3 – 4 pectinate, with up to 14 – 15 teeth ( Figure 2 (i)). Compound spinifalciger absent. Compound spinigers present in all chaetigers; in anterior-median region with blades of two lengths, shorter ones ( Figure 2 (k)) more abundant than longer ones ( Figure 2 (j)); in posterior region with blades of similar size, decreasing in number, two or three per parapodium. Compound falcigers present from chaetiger 45 to last chaetiger of fragment; in median-posterior region, with blades of similar length (48 µm, Figure 2 (l)), more abundant than spinigers; all with blunt teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally. Subacicular hooks bidentate, reddish along most of its length, translucent on the distal tip, starting from chaetiger 35, one per chaetiger, except for replacement; with distal triangular tooth, smaller than proximal, directed upward, with proximal blunt tooth, directed laterally ( Figure 2 (m)).

Variations

Material examined with L10 = 5.3 – 11 mm and W10 = 3.1 – 6.7 mm. One specimen complete with 158 chaetigers and pygidium in regeneration. Palps reaching middle of the first peristomial ring or first chaetiger. Lateral and median antennae reaching first or third chaetiger. The maxillary formula variations are MII 3 – 4+3 – 4, MIII 4 – 5, MIV 4 – 6+6 – 7. The proportions of the maxillary apparatus vary as follows: the maxillary carriers are 2.8 – 4.1 times shorter than the length of the MI; the closing system is 5 – 5.8 times shorter than the length of the MI; the cavity opening is 2.8 – 3.8 times shorter than the length of the MII. Branchiae from chaetigers 30 – 44 to last chaetiger. Maximum number of branchial filaments varied from four to five. Poorly developed postchaetal lobe present in the first 23 – 40 chaetigers. Ventral cirri with a swollen base from chaetigers 5 to 91. Start of subacicular hooks in chaetigers 30 – 39. Compound falcigers start from chaetigers 30 – 54 to last chaetiger.

Distribution

Angola, Ghana, and the Republic of Congo.

Remarks

Treadwellphysa dartevellei comb. nov. resembles T. amadae , T. mixta comb. nov. and T. yucatanensis in having compound spinigiers and falcigers in anterior chaetigers. However, T. dartevellei comb. nov. lacks compound spinifalcigers and the subaciacular hooks are reddish with a translucent distal end; while T. amadae and T. yucatanensis have spinifalcigers and translucent subacicular hooks. Moreover, T. mixta comb. nov. and T. dartevellei comb. nov. differ by the distribution of the compound chaetae; in the former, the compound spinigers are only in the anterior chaetigers and the compound falcigers are in all chaetigers; while T. dartevellei comb. nov. has compound spinigers in all chaetigers and compound falcigers present from chaetigers 30 – 54.

Figures

Figure 1. Treadwellphysa dartevellei (Monro, 1936) comb. nov., holotype BMNH 1935.1.29.1–2. (a) Anterior end, dorsal view; (b) anterior end, ventral view; (c) anterior end, lateral view; (d) maxillary apparatus, dorsal view, arrows indicate the elevation at the base of MII; (e) left MI–MV, lateral view, arrows indicate ligaments between maxillae; (f) mandibles. Scale bars: a–c = 2.55 mm; d–f = 0.85 mm.

Figure 2. Treadwellphysa dartevellei (Monro, 1936) comb. nov. (a) Parapodium 3; (b) parapodium 8; (c) parapodium 21; (d) parapodium 53; (e) parapodium 71; (f) parapodium 151; (g) chaetiger 21, isodont pectinate narrow with short and slender teeth; (h) chaetiger 93, isodont pectinate wide with long and slender teeth; (i) chaetiger 150, anodont pectinate wide with long and thick teeth; (j) chaetiger 8, compound spiniger with long blade; (k) chaetiger 8, compound spiniger with short blade; (l) chaetiger 71, compound falciger; (m) chaetiger 93, subacicular hook. a–e, g, l from holotype BMNH 1935.1.29.1–2; f, h–k, m from non-type BMNH 1939.7.17.23–24.Scale bars:a = 0.15 mm; b = 0.29 mm; c = 0.42 mm; d = 0.3 mm; e = 0.6 mm; f = 0.2 mm; g–i = 7 µm; j–l = 17.5 µm; m = 60 µm. All parapodia in anterior view.