Laubieriellus decapitata, Peixoto & Paiva, 2019

Peixoto, Antônio João Malafaia & Paiva, Paulo Cesar De, 2019, New Prionospio and Laubieriellus (Annelida: Spionidae) species from Southeastern Brazil, Zootaxa 4577 (3), pp. 529-547 : 540-543

Laubieriellus decapitata sp. nov.

( Figures 11–13 )

Type material. Brazil. Espírito Santo Basin. Holotype: Amb 1 Foz 14R3, 19° 42' 34.9" S 39° 39' 3.42" W, 12/11– 19/2010, 39m, MZUSP 3383 . Paratypes: Amb6 D4R2, 19° 45' 54.88" S 39° 30' 26.22" W, 12/2011 to 02/ 2012, 142m, MNRJP 1830 (2 ind), MZUSP 3386 (2 ind); Amb6 E4R3, 19° 36' 5.08" S 39° 10' 32.85" W, 12/2011 to 02/ 2012, 149m, MNRJP 1829 (1 ind), MZUSP 3384 (1 ind), MZUSP 3385 (1 ind); Amb7 E3R3, 19° 26' 4.07" S 39° 17' 38.2" W, 12/2011 to 02/2012, 50m, MNRJP 1831 (5 ind) .

Additional material: Amb1 Foz6, 19° 54' 56.16" S 39° 56' 40.83" W, 34m (1 ind); Amb1 Foz11, 19° 57' 32.89" S 39° 53' 30.69" W, 47m (1 ind); Amb1 Foz14, 19° 42' 32.21" S 39° 38' 57.36" W, 42m (4 ind); Amb1 Foz15, 19° 37' 48.27" S 39° 35' 25.83" W, 42m (15 ind); Amb1 Foz16, 20° 1' 3.73" S 39° 50' 13.76" W, 52m (5 ind); Amb1 Foz17, 19° 55' 44.66" S 39° 45' 38.7" W, 52m (3 ind); Amb2 Foz11, 19° 57' 32.36" S 39° 53' 33.01" W, 47m (2 ind); Amb2 Foz16, 20° 1' 2.6" S 39° 50' 18.72" W, 51m (1 ind); Amb2 Foz17, 19° 55' 45.59" S 39° 45' 41.35" W, 51m (3 ind); Amb2 Foz19, 19° 46' 10.69" S 39° 34' 55.84" W, 50m (1 ind); Amb2 Foz20b, 19° 41' 29.14" S 39° 31' 18.18" W, 53m (1 ind); Amb6 D4, 19° 45' 55.39" S 39° 30' 25.74" W, 132m (79 ind); Amb6 E4, 19° 36' 5.17" S 39° 10' 32.93" W, 153m (10 ind); Amb6 CAND4, 19° 31' 51.68" S 39° 3' 4.79" W, 171m (2 ind); Amb6 CANWN4, 19° 49' 7.27" S 39° 36' 8.52" W, 158m (2 ind); Amb7 A2, 21° 2' 47.31" S 40° 32' 28.94" W, 40m (1 ind); Amb7 A3, 21° 4' 1.29" S 40° 18' 50.11" W, 50m (2 ind); Amb7 B3, 20° 34' 53.42" S 40° 6' 27.43" W, 50 m (13 ind); Amb7 B4, 20° 35' 25.16" S 39° 54' 58.31" W, 157m (2 ind); Amb7 C2, 20° 11' 25.35" S 40° 2' 16.02" W, 39m (5 ind);Amb7 C3, 20° 12' 20.26" S 39° 57' 59.7" W, 50m (4 ind); Amb7 D1, 19° 35' 37.21" S 39° 41' 19.68" W, 26m (1 ind); Amb7 D2, 19° 40' 26.04" S 39° 36' 19.65" W, 40m,(4 ind); Amb7 D3, 19° 43' 14.34" S 39° 33' 34.86" W, 50m (6 ind); Amb7 D4, 19° 45' 54.56" S 39° 30' 25.23" W, 145m (6 ind); Amb7 E2, 19° 18' 5.9" S 39° 23' 23.3" W, 39m (3 ind); Amb7 E3, 19° 26' 5" S 39° 17' 38.92" W, 50m (33 ind); Amb7 E4, 19° 36' 4.32" S 39° 10' 34.07" W, 147m (2 ind); Amb7 F2, 18° 52' 32.61" S 39° 8' 42.82" W, 39m (10 ind); Amb7 F3, 18° 53' 29.72" S 39° 6' 23.3" W, 52m (2 ind); Amb7 F4, 19° 33' 2.92" S 38° 42' 52.26" W, 152m (1 ind); Amb7 G2, 18° 36' 31.68" S 39° 9' 33" W, 39m (5 ind); Amb7 G3, 18° 40' 55.3" S 38° 55' 41.48" W, 55m (11 ind); Amb12 D4 P300, 19° 45' 53.43" S 39° 30' 25.97" W, 146m (1 ind); Amb12 D4, 19° 45' 53.43" S 39° 30' 25.97" W, 146m (3 ind); Amb12 D4 T300,19° 45' 53.43" S 39° 30' 25.97" W, 144m (1 ind); Amb12 E4, 19° 36' 3.57" S 39° 10' 33.64" W, 152m (3 ind); Amb14 A2, 21° 3' 31.13" S 40° 22' 59.88" W, 40m (1 ind); Amb14 E2, 19° 18' 6.12" S 39° 23' 23.35" W, 38m (1 ind); Amb 14 F3, 18° 53' 31.97" S 39° 6' 21.78" W, 51m (13 ind); Amb13 G2, 18° 36' 32.45" S 39° 9' 32.83" W, 40m (9 ind); Amb13 G3, 18° 40' 57.41" S 38° 55' 39.92" W, 53m (30 ind).

Diagnostic features: Large auricular notopodial prechaetal and postchaetal lamellae on chaetiger 1; prostomium often obscured by peristomium.

Description: A small-sized spionid, largest individual about 5 mm long, 0.3 mm wide for 45 chaetigers, holotype 3.5 mm long, 0,28 mm wide for 37 chaetigers. Body translucent and fragile, dorsoventrally flattened throughout. Pigmentation absent.

Prostomium truncate, weakly incised anteriorly, eyes absent. Caruncle extending posteriorly to end of chaetiger 3. Prostomial peaks absent. Peristomium encircling the prostomium and partially fused with chaetiger 1, lateral wings absent ( Figs 11 ; 12 A–B). Grooved palps extending up to chaetiger 8, lost in most specimens.

Chaetiger 1 with short chaetae on both rami. Notopodial and neuropodial postchaetal lamellae large, auricularshaped, well-developed in adults, although smaller than those on following chaetigers ( Figs 11 ; 12 A–C). Notopodial prechaetal lamellae large and auricular-shaped.

Notopodial postchaetal lamellae foliaceous and largest on chaetigers 2–5, extending to mid-dorsum ( Figs 11A ; 12 A–B; 13A–D). Postchaetal lamellae round on chaetigers 6–7, progressively smaller on chaetigers 8–9 and reduced from chaetiger 10 onwards. Prechaetal lamellae absent. Dorsal crests high from chaetiger 7 to 9 and low crest from chaetiger 10 to chaetigers 11–12 ( Figs 11A ; 12 A–B).

Neuropodial postchaetal lamellae rounded from chaetigers 2–9, broad in the branchial region, largest on chaetiger 3 and reduced from chaetiger 10 onwards. Prechaetal lamellae absent. Ventral crests with median notch from chaetiger 2 to chaetigers 9–11, shallow on chaetigers 2 and 3 ( Figs 11B ; 12C ).

Chaetae organized in two rows of non-limbate and lightly granulated capillaries. In anterior notopodia, capillaries of the posterior rows up to two times longer than capillaries from the anterior row ( Fig. 13 F–G). Towards the posterior region, capillaries progressively become elongate, thin and less numerous.

Neuropodial hooded hooks from chaetiger 9–10, up to eight per fascicle. Notopodial hooks absent. Hooks multidentate, with 6–8 secondary teeth arranged in two rows above main tooth ( Figs 12D ; 13H ). Small secondary hood present. Hooks accompanied by 3–10 short non-limbate capillaries. Granulated sabre chaetae from chaetiger 10 ( Fig. 13I ).

Branchiae on chaetigers 2–5, longer than postchaetal notopodial lamellae. Branchiae apinnate, cirriform on chaetigers 2 and 5 and robust, flattened and densely ciliated on chaetigers 3 and 4, all pairs narrowing abruptly at tips ( Figs 11A ; 12 A–B; 13A–D).

Pygidium with one long mid-dorsal cirrus and a pair of shorter ventral cirri ( Fig. 13E ).

Oocytes from chaetigers 9–12, measuring up to 120 µm.

Variation: Around 20% of all specimens presented two sabre chaetae per rami on chaetigers 10 and 11.

Methyl green pattern: Diffused throughout the body. Margins of lamellae slightly more stained from chaetiger 1 to chaetiger 10.

Remarks: The genus Laubieriellus was erected by Maciolek (1981b) to include species of the Prionospio - complex that bear ventral crests on anterior chaetigers, have cylindrical apinnate branchiae, and lack notopodial hooded hooks.

Only three Laubieriellus species are known: L. grasslei , from hydrothermal vents on the Galápagos Islands ( Ecuador), L. salzi , from the coast of Israel, Mediterranean Sea, and L. cacatua , from Western Australia.

Laubieriellus species present remarkable character overlapping. Thus, characters such as caruncle length, first chaetiger with hooded hooks and sabre chaetae may not be helpful to distinguish species ( Table 1).

Laubieriellus decapitata sp. nov. is similar to L. cacatua in the distribution of dorsal and ventral crests, but these species can be distinguished by prostomial shape, shape of postchaetal neuropodial lamellae (especially on chaetiger 1), arrangement and number of secondary teeth on the hooded hooks, and pygidial shape. Laubieriellus decapitata sp. nov. can be readily distinguished from L. grasslei by prostomial shape, distribution of dorsal and ventral crests, notch morphology, pygidial shape, and bathymetry.

Laubieriellus decapitata sp. nov. is most similar to L. salzi in prostomial shape, but the two species can be distinguished by the distribution of dorsal and ventral crests, shape of parapodial lamellae on chaetiger 1, shape of notopodial lamellae after chaetiger 10 (reduced in L. decapitata and digitiform in L. salzi ) and number of secondary teeth on the hooded hooks.

Etymology: The epithet decapitata (Latin for beheaded) refers to the prostomium, which is difficult to distinguish as it is translucent and does not stand out from the surrounding structures, and is also encircled by the peristomium for the most part. This led many students to consider specimens as fragments with the prostomium absent.

Habitat: Coarse to fine sand.

Distribution: Espírito Santo and Campos basins, 25–150 m deep. The present record expands the geographic range of the genus to the Southern Atlantic Ocean.

Figures

FIGURE 11. Laubieriellus decapitata sp. nov. (MNRJP 1831, paratypes). A. Anterior chaetigers, dorsal view. B. Anterior chaetigers, ventral view. Abbreviations: dc, dorsal crest; pe, peristomium; pr, prostomium; vc, ventral crest.

FIGURE 12. SEM of Laubieriellus decapitata sp. nov. A. Anterior chaetigers, dorsal view. B. Anterior chaetigers, dorsolateral view. C. Anterior chaetigers, ventral view. D. Hooks (hoods removed), lateral view. Abbreviations: br, branchia; dc, dorsal crest; pr, prostomium; vc, ventral crest.

FIGURE 13. Laubieriellus decapitata sp. nov. A. Parapodium from chaetiger 2. B. Parapodium from chaetiger 3. C. Parapodium from chaetiger 4. D. Parapodium from chaetiger 5. E. Pygidium. F. Anterior capillary chaetae from posterior row. G. Anterior capillary chaeta from anterior row. H. Hooded hooks (as seen in light microscopy). I. Sabre chaeta.