Prionospio biancoi, 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 : 497-500

Prionospio biancoi sp. nov.

( Figures 29–31 )

Type material. Brazil. Espírito Santo Basin. Holotype: Amb 5 C7, 20°17’41,07” S, 39°42’38,02” W, 02 Dec 2011 to 02 Feb 2012,1358m, MNRJP-2770. Paratypes: Amb6 CANWN7 , 19°58’11,44” S, 39°31’38,29” W, 02 Dec 2011 to 02 Feb 2012, 1300m, MNRJP-2771 (2 ind) .

Additional material examined. Amb6 CANWN7 , 19°58’11,44” S, 39°31’38,29” W, 1300m (1 ind); Amb8 G6, 19°3’32,9” S, 37°49’4,82” W, 988m (1 ind); Amb11 B7, 20°36’48,64” S, 39°49’32,61” W, 1324m (1 ind) .

Diagnostic features: Body light yellow to yellow, with golden inclusions from chaetigers 5–6 to chaetigers 11–13, lack of dorsal crests, four pairs of apinnate branchiae, hooks bearing five pairs of secondary teeth.

Description. A large-sized Prionospio species, largest specimen 15 mm long, 1 mm wide at widest part for 72 chaetigers (incomplete); holotype incomplete, 9 mm long, 0.7 mm wide at widest part for 40 chaetigers. Body slightly dorsoventrally flattened on entire fragment, tapering towards end of fragment. Body color light yellow to yellow in alcohol, with golden inclusions near parapodia from chaetigers 5–6 to chaetigers 11–13 ( Fig. 29 ).

Prostomium rectangular, extending posteriorly as a narrow keel reaching posterior margin of chaetiger 2. Nuchal organs not observed. Prostomial peaks absent. Eyes absent. Peristomium surrounding prostomium and partially fused to chaetiger 1, lateral wings absent ( Figs 29 ; 30 B–C). Palps lost in all specimens.

Chaetiger 1 with only a few chaetae on both rami, shorter than chaetae on succeeding chaetigers. Postchaetal lamellae absent on notopodium and auricular on neuropodium, both much smaller than lamellae on succeeding chaetigers ( Fig. 31A ). Prechaetal lamellae absent.

Notopodial postchaetal lamellae foliaceous from chaetiger 2 to chaetigers 5–8 (depending on specimen size) ( Fig. 31 B–D), quadrangular and gradually reducing in size from chaetigers 6–9 to chaetigers 13–17, present as a low flap afterwards ( Figs 29 ; 30A ). Notopodial prechaetal lamellae absent. Dorsal crests absent. Lamellae from posterior region unknown.

Neuropodial postchaetal lamellae rounded and gradually reducing in size from chaetiger 2 to chaetigers 24–31 ( Fig. 31 B–D), reduced to a low flap afterwards. Neuropodial prechaetal lamellae absent. Lamellae from posterior region unknown.

Chaetae from notopodia and neuropodia organized in two rows of wide, unilimbate and granulated capillaries, intensely granulated near base and sparsely granulated near tip ( Fig. 31E ). Notopodial capillaries up to 1.4 times longer than neuropodial capillaries ( Fig. 31F ). Towards end of fragment, capillaries progressively become elongate, non-limbate, non-granulated, thinner and less numerous ( Fig. 31G ).

Hooks in notopodia starting from chaetiger 67, up to three per fascicle, accompanied by 1–4 non-limbate capillaries ( Fig. 31H ). Hooks in neuropodia starting from chaetigers 16–22, up to six per fascicle, accompanied by 1–6 non-limbate capillaries. All hooks multidentate, with 10 secondary teeth arranged in two rows above main tooth ( Figs 30D ; 31I ). Secondary hood present ( Fig. 31H ). Sabre chaetae starting from chaetigers 14–20. Sabre chaetae non-limbate and intensely granulated throughout length ( Fig. 31J ).

Branchiae present on chaetigers 2–5, about the same length of notopodial lamellae on chaetiger 2, slightly shorter than notopodial lamellae on chaetigers 3 and 4 and about half the length of notopodial lamellae on chaetiger 5. Branchiae from chaetigers 3–4 robust, flattened and densely ciliated ( Figs 30 B–C; 31K); branchiae from chaetigers 2 and 5 smooth and cirriform.

Pygidium of unknown morphology.

Methyl green staining pattern: No pattern observed, whole specimen weakly stained.

Remarks. Prionospio biancoi sp. nov. is unusual for its large size in deep-sea samples, being much larger than its congeners. The yellowish body color and lack of dorsal crests are similar to P. solisi , although species can be readily distinguished by the prostomial morphology—rectangular in P. biancoi sp. nov. and rounded in P. solisi , shape of lamellae from chaetiger 1—absent on notopodium and auricular on neuropodium in P. biancoi sp. nov. and rounded on both rami in P. solisi ; branchiae distribution—on chaetigers 2–5 in P. biancoi sp. nov. and chaetigers 3 and 4 in P. solisi ; starting chaetiger of notopodial hooded hooks—from chaetiger 67 in P. biancoi sp. nov. and chaetigers 48–61 in P. solisi ; starting chaetiger of neuropodial hooded hooks—from chaetigers 16–22 in P. biancoi sp. nov. and chaetigers 9–14 in P. solisi and starting chaetiger of sabre chaetae—from chaetigers 14–20 in P. biancoi sp. nov. and chaetigers 9–11 in P. solisi ( Peixoto & Paiva 2019) .

The species is also similar to P. fosterae sp. nov., P. hartmanae sp. nov., and P. alexandrae sp. nov. in lacking dorsal crests, although species differ on the prostomium shape—rectangular in P. biancoi sp. nov., anteriorly rounded in both P. fosterae sp. nov. and P. hartmanae sp. nov., and narrow and rectangular in P. alexandrae sp. nov. Species can also be distinguished by the branchial morphology—four pairs of apinnate branchiae in P. biancoi sp. nov., up to 11 pairs of apinnate branchiae in both P. fosterae sp. nov. and P. hartmanae sp. nov., and two pairs of cirriform and apinnate branchiae in P. alexandrae sp. nov.

Prionospio biancoi sp. nov. is similar to P. quadrilamellata sp. nov. in having four pairs of apinnate branchiae, although species can be distinguished by the branchial morphology—first and fourth branchial pairs cirriform and second and third pairs flattened in P. biancoi sp. nov. and all pairs flattened in P. quadrilamellata sp. nov. and lack of dorsal crests in P. biancoi sp. nov. Species can also be separated based on the starting chaetiger of notopodial hooded hooks—from chaetiger 67 in P. biancoi sp. nov. and chaetigers 20–32 in P. quadrilamellata sp. nov., starting chaetiger of neuropodial hooded hooks—from chaetigers 16–22 in P. biancoi sp. nov. and chaetigers 9–13 in P. quadrilamellata sp. nov. and starting chaetiger of sabre chaetae—from chaetigers 14–20 in P. biancoi sp. nov. and chaetigers 9–11 in P. quadrilamellata sp. nov.

Unfortunately, only a few anterior fragments of P. biancoi sp. nov. were collected, thus characters such as starting chaetiger of notopodial hooded hooks remain poorly known while the morphology of the pygidium remains unknown.

Etymology. The specific epithet, biancoi , is a homage to Cinthia X. Bianco, who helped the first author immensely during the initial sorting and identification of Spionidae specimens.

Habitat: Very fine sand to fine silt, 988–1358 m depth.

Distribution: Southeastern Brazil (Rio de Janeiro and Espírito Santo states), Atlantic Ocean.

Figures

FIGURE 29. Prionospio biancoi sp. nov., showing characteristic color in ethanol (MNRJP-2771, paratype). Abbreviations: br, branchiae; pe, peristomium; pr, prostomium.

FIGURE 30. SEM of Prionospio biancoi sp. nov. A. Whole fragment, dorsal view. B. Anterior end, dorsal view. C. Close-up of anterior end, dorsal view. D. Hook (hood removed). br, branchiae; ho, hook; pe, peristomium; pr, prostomium.

FIGURE 31. Prionospio biancoi sp. nov. A. Chaetiger 1. B. Chaetiger 2. C. Chaetiger 3. D. Chaetiger 4. E. Notochaetae from anterior region. F. Notochaetae from anterior region. G. Posterior capillary chaetae. H. Companion capillary chaetae. I. Hooded hook (as seen in light microscopy). J. Sabre chaetae. K. Branchiae.