Prionospio corrugata, Peixoto & Paiva, 2020

Peixoto, Antônio João Malafaia & Paiva, Paulo Cesar, 2020, New apinnate Prionospio (Annelida: Spionidae) species from southeastern Brazil, Zootaxa 4853 (4), pp. 451-508 : 483-486

Prionospio corrugata sp. nov.

( Figures 20–22 )

Type material. Brazil. Espírito Santo Basin. Holotype: Amb 5 B5, 20º 35’ 15.16” S, 39º 53’ 46.36” W, 02 Dec 2011 to 02 Feb 2012, 991m, MNRJ-2764. Paratypes: Amb11 C5, 20º 14’ 19.79” S, 39º 48’ 36.57” W, 06 Jul 2013 to 17 Jul 2013, 418m, MNRJP-2765 (5 ind); Amb5 B6, 20º 36’ 2.03” S, 39º 51’ 35.37” W, 02 Dec 2011 to 02 Feb 2012, 991m, MNRJP-2766 (4 ind); Amb12 D6, 19º 50’ 6.01” S, 39º 26’ 34.62” W, 02 Dec 2011 to 02 Feb 2012, 1048m, MNRJP-2767 (10 ind) .

Additional material examined. Amb3 E5, 19º 36’ 25.08” S, 39º 10’ 20.15” W, 352m (19 ind); Amb3 E6, 19º 40’ 13.13” S, 39º 7’ 20.92” W, 1010m (27 ind); Amb3 F5, 19º 34’ 21.01” S, 38º 41’ 16.99” W, 438m (1 ind); Amb3 CAND4 , 19º 31’ 51.13” S, 39º 3’ 4.99” W, 140m (1 ind); Amb3 CAND5 , 19º 33’ 20.99” S, 39º 2’ 36.2” W, 384m (34 ind); Amb3 CAND7 , 19º 42’ 20.31” S, 39º 5’ 55.46” W, 1289m (1 ind); Amb4 B8, 20º 41’ 33.45” S, 39º 35’ 14.76” W, 1902m (1 ind); Amb4 F7, 20º 4’ 8.18” S, 38º 31’ 27.32” W, 1288m (7 ind); Amb5 A5, 21º 4’ 5.57” S, 40º 13’ 2.63” W, 396m (49 ind); Amb5 A6, 21º 4’ 43.84” S, 40º 8’ 31.76” W, 990m (26 ind); Amb5 A7, 21º 4’ 51.67” S, 40º 4’ 14.88” W, 1316m (16 ind); Amb5 B5, 20º 35’ 15.16” S, 39º 53’ 46.36” W, 382m (5 ind); Amb5 B6, 20º 36’ 2.03” S, 39º 51’ 35.37” W, 991m (43 ind); Amb5 B7, 20º 36’ 47.44” S, 39º 49’ 22.5” W, 1315m (18 ind); Amb5 C5, 20º 14’ 19.45” S, 39º 48’ 36.67” W, 416m (5 ind); Amb5 C6, 20º 15’ 34.21” S, 39º 46’ 15.69” W, 1031m (24 ind); Amb5 C7, 20º 15’ 39.85” S, 39º 46’ 10.03” W, 1309m (15 ind); Amb5 D6, 19º 50’ 4.42” S, 39º 26’ 33.42” W, 1053m (23 ind); Amb5 D7, 19º 54’ 5.01” S, 39º 22’ 20.04” W, 1333m (12 ind); Amb5 D8, 20º 8’ 42.11” S, 39º 7’ 29.06” W, 1905m (1 ind); Amb6 D5, 19º 46’ 32.67” S, 39º 30’ 3.54” W, 402m (36 ind); Amb6 E4, 19º 36’ 5.17” S, 39º 10’ 32.93” W, 145m (1 ind); Amb6 CANWN5 , 19º 49’ 38.59” S, 39º 35’ 44.43” W, 352m (68 ind); Amb6 CANWN6 , 19º 53’ 29.3” S, 39º 32’ 59.04” W, 955m (7 ind); Amb6 CANWN7 , 19º 58’ 13.68” S, 39º 31’ 43.28” W, 1284m (4 ind); Amb8 E7, 19º 47’ 5.96” S, 39º 3’ 11.96” W, 1223m (4 ind); Amb8 G6, 19º 3’ 32.9” S, 37º 49’ 4.82” W, 1011m (1 ind); Amb8 G7, 19º 3’ 30.21” S, 37º 48’ 42.41” W, 1245m (2 ind); Amb11 A5, 21º 4’ 8.5” S, 40º 13’ 7.35” W, 383m (43 ind); Amb11 A6, 21º 4’ 43.95” S, 40º 8’ 34.11” W, 997m (18 ind); Amb11 A7, 21º 4’ 40.63” S, 40º 4’ 10.65” W, 1331m (8 ind); Amb11 B5, 20º 35’ 13.87” S, 39º 53’ 45.78” W, 382m (7 ind); Amb11 B6, 20º 35’ 57.27” S, 39º 51’ 38.12” W, 994m (29 ind); Amb11 B7, 20º 36’ 49.74” S, 39º 49’ 29.01” W, 1327m (13 ind); Amb11 C5, 20º 14’ 17.95” S, 39º 48’ 34.35” W, 418m (3 ind); Amb11 C6, 20º 15’ 32.22” S, 39º 46’ 9.28” W, 1029m (17 ind); Amb11 C7, 20º 17’ 39.63” S, 39º 42’ 38.76” W, 1347m (16 ind); Amb12 D5, 19º 46’ 32.84” S, 39º 30’ 3.65” W, 431m (18 ind); Amb12 D6, 19º 50’ 6.01” S, 39º 26’ 34.62” W, 1048m (34 ind); Amb12 D7, 19º 54’ 5.24” S, 39º 22’ 28.64” W, 1330m (1 ind); Amb12 E5, 19º 36’ 30.6” S, 39º 10’ 19.39” W, 349m (10 ind); Amb12 E6, 19º 40’ 1.46” S, 39º 7’ 21.99” W, 1018m (20 ind); Amb12 E7, 19º 47’ 2.24” S, 39º 3’ 13.72” W, 1242m (8 ind); Amb11 E8, 20º 15’ 53.31” S, 38º 40’ 53.51” W, 1886m (9 ind); Amb12 G7, 19º 3’ 31.11” S, 37º 48’ 42.65” W, 1361m (1 ind); Amb12 CAND5 , 19º 33’ 23.09” S, 39º 2’ 35.67” W, 446m (12 ind); Amb12 CAND6 , 19º 37’ 46.26” S, 39º 3’ 59.65” W, 1036m (4 ind); Amb12 CANWN5 , 19º 49’ 36.67” S, 39º 35’ 43.43” W, 363m (38 ind); Amb12 CANWN6 , 19º 53’ 27.27” S, 39º 32’ 59.82” W, 960m (7 ind); Amb12 CANWN7 , 19º 58’ 12.82” S, 39º 31’ 42.22” W, 1305m (15 ind) .

Diagnostic features: Three rows of capillary chaetae on notopodia from chaetiger 2 to chaetigers 10–12; neuropodium of chaetiger 3 bearing very long chaetae on posterior row; sculptured branchiae on chaetigers 2 and 5–7, pygidium bearing a single dorsal cirrus.

Description. A medium-sized Prionospio , largest complete specimen 6 mm long, 0.5 mm wide at the widest part for 91 chaetigers; holotype complete, 5.5 mm long, 0.40 mm wide at widest part for 74 chaetigers. Body widest and dorsoventrally flattened in branchial region, cylindrical afterwards, tapering towards pygidium. Body color yellow to whitish in alcohol ( Fig. 20 ).

Prostomium rectangular, narrow, truncated on anterior margin, extending posteriorly as a narrow keel reaching anterior margin of chaetiger 2 ( Figs 20 ; 21 A–B). Small prostomial peaks might be present. Eyes absent. Peristomium surrounding prostomium and partially fused to chaetiger 1, lacking lateral wings. Grooved palps reaching up to chaetiger 10, lost in most specimens.

Chaetiger 1 with only a few chaetae in both rami, especially in notopodium, shorter than chaetae on succeeding chaetigers. Postchaetal lamellae elliptical in notopodium and rounded in neuropodium. ( Figs 21B ; 22A ). Prechaetal lamellae absent.

Notopodial postchaetal lamellae foliaceous on chaetigers 2–7 ( Fig. 22 B–D), square-shaped on chaetigers 8 and 9 (largest on chaetiger 8) and rounded afterwards, gradually reduced in size towards posterior region, present as a low flap on last chaetigers. Notopodial prechaetal lamellae absent throughout. Low dorsal crests from chaetigers 8–9 to chaetigers 14–15 ( Fig. 21 A–B).

Neuropodial postchaetal lamellae elliptical on chaetigers 2–4 ( Figs 21C ; 22 B–D), with a pointed tip on dorsal edge of chaetiger 3. Lamellae rounded from chaetiger 5, gradually reduced in size towards posterior region, present as a low flap on last chaetigers. Neuropodial prechaetal lamellae absent throughout.

Chaetae from notopodia ( Fig. 22E ) and neuropodia ( Fig. 22F ) narrowly unilimbate, non-granulated capillaries, organized in three rows on notopodia from chaetiger 2 to chaetigers 10–12 and two rows in neuropodia and remaining notopodial chaetigers. Chaetae from each row of different lengths, anterior row shortest. Neuropodial chaetae slightly shorter than notopodial chaetae. Neuropodium of chaetiger 3 bearing very long chaetae in posterior row (up to four times longer than anterior row). Towards posterior region, capillaries progressively become elongate, nonlimbate, thinner and less numerous ( Fig. 22G ).

Hooks in notopodia starting from chaetigers 22–44, up to five per fascicle, accompanied by 1–4 short non-limbate capillaries ( Fig. 22H ). Hooks in neuropodia starting from chaetigers 10–12, up to 12 per fascicle, accompanied by 1–6 short non-limbate capillaries. All hooks multidentate, with eight secondary teeth organized in two vertical rows above main tooth ( Figs 21D ; 22I ). Small secondary hood present ( Fig. 22I ). Sabre chaetae starting from chaetigers 10–17, being morphologically identical to remaining capillaries—albeit shorter, only recognizable by a slight curvature and by ventral-most position ( Fig. 22J ).

Up to six pairs of branchiae, subtriangular, robust and flattened on chaetigers 3 and 4 and cirriform, sculptured (“wrinkled”) on remaining chaetigers, all tapered at tips ( Fig. 22 K–L). Branchiae present from chaetiger 2, up to three times longer than notopodial lamellae, slightly reduced in length towards last branchial pair. Branchiae on chaetigers 3 and 4 heavily ciliated throughout, branchiae on remaining chaetigers ciliated at base. All branchiae completely free from notopodial postchaetal lamellae ( Fig. 21 A–B).

Pygidium rounded, bearing a single long dorsal cirrus ( Fig. 22M ).

Gametes not observed.

Variation: In juveniles (up to 2.5 mm long), the prostomium is square-shaped, rather than rectangular.

Methyl green staining pattern: Prostomium, lateral and ventral sides of the peristomium, postchaetal neuropodial lamellae from chaetigers 2–6, postchaetal notopodial lamellae from chaetiger 2 to chaetigers 12–15 and dorsal crests intensely stained; tips of the last branchial pair slightly stained.

Remarks. Prionospio corrugata sp. nov. is easily recognizable among Brazilian apinnate Prionospio species by its set of characters: a rectangular prostomium, sculptured branchiae (except on chaetigers 2 and 3), three rows of capillary chaetae on notopodia from chaetiger 2 to chaetigers 10–12, row of long neurochaetae on chaetiger three and pygidium bearing a single dorsal cirrus.

The narrow rectangular prostomium is most similar to P. ehlersi Fauvel, 1928 , described from Morocco, P. kaplani , P. amarsupiata Neal & Altamira in Paterson et al., 2016 , described from Portugal and P. branchilucida Altamira, Glover, & Paterson in Paterson et al. 2016 , described from the Kaplan Clarion-Clipperton Fracture Zone, East Pacific Ocean, but these species lack a row of long neurochaetae on chaetiger 3 and possess different branchial distribution (four pairs in P. ehlersi and P. amarsupiata ; two pairs in P. branchilucida and P. kaplani ). A narrow rectangular prostomium and a row of long neurochaetae on chaetiger 3 are present in Prionospio fauchaldi , described from the continental slope of northwestern Atlantic Ocean, discussed in detail further below.

Whereas the row of long neurochaetae on chaetiger 3 and a third row of capillaries on some anterior notopodia are known only from Prionospio corrugata sp. nov. and P. fauchaldi , sculptured branchiae have only been observed in P. cinthyae sp. nov., P. sandersi , described from the Galapagos Islands, Ecuador, P. laciniosa and P. vallensis . These species can be distinguished from P. corrugata sp. nov. by the prostomial morphology (rectangular and truncated anteriorly in P. corrugata sp. nov., P. fauchaldi , triangular in P. cinthyae sp. nov. and P. vallensis , broadly rounded in P. sandersi and triangular in P. laciniosa ), presence of typical sabre chaetae (except for P. fauchaldi , see discussion below) and by the branchial distribution (up to six pairs in P. corrugata sp. nov., four pairs in P. fauchaldi , P. laciniosa , P. cinthyae sp. nov. and P. vallensis , and nine pairs in P. sandersi ). Species also differ on the presence, morphology and distribution of dorsal crests, which are lacking in P. sandersi , present as semicircular flaps on chaetigers 5–13 in P. laciniosa , present from chaetigers 8–9 to chaetigers 14–15 in P. corrugata sp. nov., from chaetiger 6 to beyond chaetiger 20 in P. vallensis , from chaetigers 8–11 in P. fauchaldi (distribution not mentioned) and from chaetiger 6 to chaetigers 7–9 in P. cinthyae sp. nov. ( Maciolek 1985; Paterson et al. 2016).

Prionospio corrugata is very similar to P. fauchaldi , as both species bear a rectangular prostomium, a long row of neurochaetae on chaetiger 3, three rows of notopodial chaetae on several anterior segments, hooks with four pairs of secondary teeth and delicate sabre chaetae. However, the species differ in important characters, such as the number of branchiae, up to six pairs in P. corrugata sp. nov. and four pairs in P. fauchaldi , shape of the postchaetal lamellae on chaetiger 1 (elliptical on the notopodium and rounded on the neuropodium of P. corrugata sp. nov. and rounded on the notopodium and elliptical on the neuropodium of P. fauchaldi ), chaetigers bearing three rows of capillaries in the notopodium (from chaetiger 2 to chaetigers 10– 12 P. corrugata sp. nov. and from chaetiger 2 to chaetigers 15–17 in P. fauchaldi ), distribution of dorsal crests (from chaetigers 8–9 to chaetigers 14–15 in P. corrugata sp. nov. and starting from chaetigers 8–11 in P. fauchaldi [distribution not mentioned]).

Species mentioned above can also be distinguished by the shape of notopodial postchaetal lamellae on various anterior chaetigers (larger on chaetigers 2–8 and broad, square-shaped on chaetiger 8 in P. corrugata sp. nov.), starting chaetiger of neuropodial hooded hooks (chaetigers 10–12 in P. corrugata sp. nov. and chaetigers 12–13 in P. fauchaldi ) and the presence of sabre chaetae on all chaetigers from chaetigers 10–17 in P. corrugata sp. nov. which are frequently lacking in P. fauchaldi . Unfortunately, all type material of P. fauchaldi was incomplete, thus making it impossible to compare the starting chaetiger of notopodial hooded hooks and pygidial morphology ( Maciolek 1985).

Etymology. The specific epithet, corrugata , derives from the wrinkled appearance of branchiae from chaetigers 2 and 5 (corruga, Latin for wrinkled and the suffix - atus, meaning possessing, bearing).

Habitat: Muddy sand to mud, 140–1905 m depth.

Distribution: Southeastern Brazil (Espírito Santo and Campos basins), Atlantic Ocean.

Figures

FIGURE 20. Prionospio corrugata sp. nov., showing characteristic color in ethanol (MNRJP-2765, paratype). Abbreviations: br, branchia; pe, peristomium; pr, prostomium.

FIGURE 21. SEM of Prionospio corrugata sp. nov. A. Anterior end and mid-body chaetigers, dorsal view. B. Close-up of the anterior end, dorsal view. C. Anterior end, ventral view. D. Hooded hooks (hoods partially removed). Abbreviations: br, branchia; cha3, chaetiger 3; nel, neuropodial lamellae; nol, notopodial lamella; pe, peristomium; pr, prostomium.

FIGURE 22. Prionospio corrugata sp. nov. A. Chaetiger 1. B. Chaetiger 2. C. Chaetiger 3. D. Chaetiger 4. E. Anterior capillary chaeta from anterior row. F. Anterior capillary chaeta from posterior row. G. Posterior capillary chaetae. H. Companion capillary chaetae. I. Hooded hook. J. Sabre chaetae. K. Sculptured branchia. L. Flattened branchia. M. Posterior-most chaetigers and pygidium.