Prionospio cinthyae, 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 : 479-483

Prionospio cinthyae sp. nov.

( Figures 17–19 )

Type material. Brazil. Espírito Santo Basin. Holotype: Amb 7 E3, 19º 26’ 5” S, 39º 17’ 38.92” W, 02 Dec 2011 to 02 Feb 2012, 26m, MNRJ-2761. Paratypes: Amb1 Foz15, 19º 37’ 48.27” S, 39º 35’ 25.83” W, 11 Dec 2010 to 19 Dec 2010, 41m, MNRJP-2762 (5 ind); Amb7 E3, 19º 26’ 5” S, 39º 17’ 38.92” W, 02 Dec 2011 to 02 Feb 2012, 26m, MNRJP-2763 (9 ind) .

Additional material examined. Amb1 Foz1, 19º 52’ 22.74” S, 39º 59’ 38.05” W, 28m (1 ind); Amb1 Foz2, 19º 47’ 22.34” S, 39º 55’ 6.96” W, 24m (1 ind); Amb1 Foz5, 19º 32’ 32.82” S, 39º 41’ 34.89” W, 20m (1 ind); Amb1 Foz7, 19º 49’ 57.38” S, 39º 52’ 14.02” W, 33m (15 ind); Amb1 Foz8, 19º 44’ 45.48” S, 39º 46’ 25.78” W, 32m (2 ind); Amb1 Foz10, 19º 35’ 10.73” S, 39º 38’ 35.79” W, 32m (2 ind); Amb1 Foz11, 19º 57’ 32.89” S, 39º 53’ 30.69” W, 47m (4 ind); Amb1 Foz12, 19º 52’ 35.48” S, 39º 49’ 5.63” W, 43m (7 ind); Amb1 Foz15, 19º 37’ 48.27” S, 39º 35’ 25.83” W, 41m (23 ind); Amb1 Foz20, 19º 41’ 33.92” S, 39º 31’ 17.74” W, 54m (5 ind); Amb2 Foz1, 19º 52’ 14.57” S, 39º 59’ 41.06” W, 27m (8 ind); Amb2 Foz3, 19º 42’ 8.87” S, 39º 49’ 29.72” W, 16m (1 ind); Amb2 Foz7, 19º 49’ 52.15” S, 39º 52’ 24.51” W, 30m (5 ind);Amb2 Foz10, 19º 35’ 2.68” S, 39º 38’ 40.25” W, 31m (4 ind); Amb2 Foz12, 19º 52’ 29.19” S, 39º 49’ 12.78” W, 45m (3 ind); Amb2 Foz20, 19º 41’ 26.47” S, 39º 31’ 19.38” W, 53m (3 ind); Amb2 Foz20b, 19º 41’ 26.14” S, 39º 31’ 20.62” W, 53m (1 ind); Amb7 A2, 21º 3’ 27.14” S, 40º 22’ 59.61” W, 40m (1 ind); Amb7 B1, 20º 34’ 32.47” S, 40º 20’ 52.37” W, 25m (20 ind); Amb7 D1, 19º 35’ 37.21” S, 39º 41’ 19.68” W, 25m (13 ind); Amb7 D3, 19º 43’ 14.34” S, 39º 33’ 34.86” W, 50m (27 ind); Amb7 E2, 19º 18’ 5.9” S, 39º 23’ 23.3” W, 39m (6 ind); Amb7 E3, 19º 26’ 5” S, 39º 17’ 38.92” W, 26m (138 ind); Amb7 F2, 18º 52’ 32.61” S, 39º 8’ 42.82” W, 40m (1 ind); Amb14 B1, 20º 34’ 29.6” S, 40º 20’ 54.56” W, 26m (1 ind); Amb14 E2, 19º 18’ 6.12” S, 39º 23’ 23.35” W, 38m (4 ind); Amb14 E3, 19º 26’ 4.81” S, 39º 17’ 38.64” W, 50m (8 ind); Amb12 E4, 19º 36’ 4,74” S, 39º 10’ 34,59” W, 150m (3 ind).

Diagnostic features: Four pairs of apinnate branchiae, first and last pairs wrinkled, first pair up to three times longer than last branchial pair, dorsal crests from chaetiger 6 to chaetigers 7–9.

Description. A medium-sized Prionospio , largest complete specimen about 7.5 mm long, 0.25 mm wide at widest part for 55 chaetigers; holotype complete, 7.5 mm long, 0.25 mm wide at widest part for 54 chaetigers. Body dorsoventrally flattened throughout, tapered towards pygidium. Body color light yellow to whitish in alcohol ( Fig. 17 A–B).

Prostomium triangular, rounded anteriorly, extending posteriorly as a narrow keel reaching the anterior margin of chaetiger 2. Nuchal organs reaching anterior margin of chaetiger 2. ( Fig. 18A ). Prostomial peaks absent. A single pair of minute blackish eyes generally present or eyes absent. Peristomium surrounding prostomium, partially fused to chaetiger 1, lateral wings absent. Grooved palps reaching up to chaetiger 10, lost in most specimens ( Fig. 17 A–B).

Chaetiger 1 bearing only a few chaetae on both rami, shorter than chaetae on succeeding chaetigers. Postchaetal lamellae square-shaped in notopodium and rounded in neuropodium, slightly reduced ( Fig. 19A ). Prechaetal lamellae absent.

Notopodial postchaetal lamellae foliaceous from chaetiger 2 to chaetigers 7–8 (largest on chaetigers 3–5) ( Fig. 19 B–D), rounded afterwards and gradually reduced in size towards posterior region, present as a low flap on last chaetigers ( Fig. 18B ). Notopodial prechaetal lamellae absent throughout. Dorsal crests from chaetiger 6 to chaetigers 7–9 (usually chaetiger 7), high on chaetiger 7 and low on remaining chaetigers ( Fig. 18 B–D).

Neuropodial postchaetal lamellae square-shaped on chaetigers 2 and 3 and rounded from chaetiger 4 afterwards ( Fig. 19 B–D), gradually reduced in size towards posterior region, present as a low flap on last chaetigers ( Fig. 18B ). Neuropodial prechaetal lamellae absent throughout.

Chaetae from notopodia and neuropodia organized in two rows of narrowly unilimbate and sparsely granulated capillaries ( Fig. 19 A–C). Chaetae from both rows of equal length in notopodia ( Fig. 19E ), whereas in neuropodia, posterior row of chaetae up to 1.5 times longer than anterior row ( Fig. 19 F–G). Neuropodial chaetae slightly shorter than notopodial chaetae. Towards the posterior region, capillaries progressively become elongate, non-limbate, nongranulated and less numerous ( Fig. 19H ).

Hooks in notopodia starting from chaetigers 21–33, up to three per fascicle, accompanied by 1–4 short non-limbate capillaries ( Fig. 19I ). Hooks in neuropodia starting from chaetigers 10–12 (generally chaetiger 10), up to five per fascicle, accompanied by 1–5 non-limbate capillaries. All hooks multidentate, with three pairs of teeth above main tooth ( Figs 18 E–F; 19J). Secondary hood absent. Sabre chaetae consistently from chaetiger 10. Sabre chaetae non-limbate, with sparsely light granulations along shaft ( Figs 18F ; 19K ).

Four pairs of apinnate branchiae, subtriangular, robust and flattened on chaetigers three and four and long, cirriform and sculptured (“wrinkled”) on chaetigers 2 and 5 ( Figs 18 A–D; 19M), all longer than notopodial lamellae and tapered at tips. Branchiae from chaetiger two up to eight times longer than notopodial lamellae and up to three times longer than branchiae from chaetiger five ( Fig. 18 A–D). All branchiae completely free from notopodial postchaetal lamellae.

Pygidium bearing a single long dorsal cirrus and two short and robust ventro-lateral lobes ( Fig. 19N ).

Oocytes from chaetiger 10, measuring up to 100 μm.

Methyl green staining pattern: Light green pigment diffused throughout body, margins of prostomium, peristomium, ventral side of peristomium and chaetiger 1 intensely stained.

Remarks. Prionospio cinthyae sp. nov. differs from most apinnate species—and, particularly, from all apinnate species recorded in Brazil in having only four pairs of branchiae. While this pattern is common among pinnate Prionospio species, it is somewhat rare among apinnate species, being observed only in P. laciniosa Maciolek, 1985 , described from Angola, P. fauchaldi Maciolek, 1985 , P. elegantula Imajima, 1990a , and P. japonicus Okuda, 1935 from Japan and P. vallensis Neal & Paterson in Paterson et al., 2016 , from off Portugal.

Prionospio cinthyae sp. nov. can be easily distinguished from P. elegantula based on branchial morphology, as the latter species bear extremely long, thin and smooth branchiae on chaetigers 2–5, while P. cinthyae sp. nov. bears wrinkled branchiae on chaetigers 2 and 5 and flattened branchiae on chaetigers 3 and 4.

Prionospio cinthyae sp. nov. and P. japonicus are similar in having a triangular prostomium and long branchiae on chaetiger 2, but can be distinguished by the lack of dorsal crests and presence of prostomial peaks in P. japonicus and by branchial morphology, P. japonicus possesses a long, cirriform branchiae on chaetiger 2 and shorter branchiae on the remaining chaetigers, while P. cinthyae sp. nov. possesses wrinkled branchiae on chaetigers 2 and 5 and flattened branchiae on chaetigers 3 and 4.

Only five additional Prionospio species bear wrinkled branchiae: P. fauchaldi , P. laciniosa , P. sandersi Maciolek, 1981 , P. vallensis , and P. corrugata sp. nov. Although P. sandersi and P. corrugata sp. nov. also bear wrinkled branchiae, both can be separated from P. cinthyae sp. nov. based on the branchial number, always four pairs in P. cinthyae sp. nov., up to six pairs in P. corrugata sp. nov. and up to nine pairs in P. sandersi and by the shape of the prostomium, which is triangular in P. cinthyae sp. nov., rectangular in P. corrugata sp. nov. and rounded in P. sandersi .

Prionospio cinthyae sp. nov. is most similar to P. fauchaldi , P. vallensis and P. laciniosa in having a combination of smooth and wrinkled apinnate branchiae on chaetigers 2–5 and long branchiae on chaetiger 2. However, Prionospio cinthyae sp. nov. can be distinguished from those species based on the presence of robust sabre chaetae (delicate in P. fauchaldi ), unmodified dorsal crests on chaetigers 6–9 (present from chaetigers 8–11 in P. fauchaldi , from chaetiger 4 to beyond chaetiger 20 in P. vallensis and modified into semicircular flaps on chaetigers 5–13 in P. laciniosa ), hook morphology (three pairs of secondary teeth in Prionospio cinthyae sp. nov., four pairs in P. fauchaldi and six pairs in P. laciniosa and P. vallensis ) and by the prostomium morphology (triangular in P. cinthyae sp. nov. and P. laciniosa , rectangular in P. fauchaldi and P. vallensis ). Prionospio cinthyae sp. nov. further differs from P. fauchaldi in lacking a long row of neurochaetae on chaetiger 3.

Etymology. The specific epithet, cinthyae , is an homage to Cinthya S. G. Santos, a polychaete researcher and former advisor of the first author.

Habitat: Gravel sand to mud, 16–150 m depth.

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

Figures

FIGURE 17. Prionospio cinthyae sp. nov., showing characteristic color in ethanol (MNRJP-2763, paratype). A. Dorsal view. B. Lateral view. Abbreviations: br, branchia; nol, notopodial lamellae; pe, peristomium; pr, prostomium.

FIGURE 18. SEM of Prionospio cinthyae sp. nov. A. Anterior end and mid-body chaetigers. B. Whole animal, dorsal view. C. Anterior end and mid-body chaetigers. D. Close-up of the anterior end. E. Hooks (hoods removed). F. Neuropodial chaetae. Abbreviations: Abbreviations: br, branchia; dc, dorsal crest; sa, sabre chaetae.

FIGURE 19. Prionospio cinthyae sp. nov. A. Chaetiger 1. B. Chaetiger 2. C. Chaetiger 3. D. Chaetiger 4. E. Anterior capillary notochaetae. F. Anterior capillary neurochaeta from anterior row. G. Anterior capillary neurochaeta from posterior row. H. Posterior capillary chaetae. I. Companion capillary chaetae. J. Hooded hook. K. Sabre chaetae. L. Sculptured branchia. M. Flattened branchia. N. Posterior-most chaetigers and pygidium.