Polymastigos profundus, Silva & Amaral, 2022

Silva, Camila Fernanda Da & Amaral, Antonia Cecilia Zacagnini, 2022, Capitellidae (Annelida) from the Brazilian Continental Margin (SW Atlantic): new occurrences of three genera and description of new species, Zootaxa 5104 (1), pp. 89-110 : 103-106

Polymastigos profundus sp. nov.

( Fig. 5A–I ; Table 3)

http://zoobank.org./ BAF59F2B-5D24-4FDC-94F9-D837E30EE80F

Material examined. Espírito Santo Basin: Holotype ( ZUEC POL 20096) 19°3'27''S 37°48'41"W, 17 Jul 2013, subtidal, 1361m, Stn. AMB12/G7, 1 spec. Paratype 1 ( ZUEC POL 20095) 19°3'27''S 37°48'42"W, 02 Feb 2012, subtidal, 1245m, Stn. AMB8/G7, 1 spec. Paratype 2 ( ZUEC POL 20101) 21°4'31''S 40°8'16"W, 02 Feb 2012, subtidal, 990m, Stn. AMB5/A6, 1 spec.

Additional material examined. Espírito Santo Basin : ( ZUEC POL 20099) 19°3'27''S 37°48'41"W, 17 Jul 2013, subtidal, 1361m, Stn. AMB12/G7, 7 specs .

Description. Incomplete holotype 42 mm long, 1.3 mm wide for 42 chaetigers. Body robust; anterior thorax slightly wider than posterior thorax; posterior thorax the same width as abdomen. Brownish color in alcohol.

Prostomium conical, large, 1/3 of the peristomium width. Tiny palpode; eyespots absent. Peristomium large, same width and 1.5x longer than chaetigers 1 and 2 ( Fig. 5A, C ). Nuchal organs not everted. Proboscis globularshaped, strongly papillated with robust papillae ( Fig. 5B ).

Thorax rounded, with 11 chaetigers. Chaetiger 1 uniramous. Capillaries on notopodia of chaetigers 1–11 and on neuropodia of chaetigers 2–10; hooded hooks on neuropodia of chaetiger 11 ( Fig. 5G ). Peristomium and chaetigers 1–3 strongly tessellated dorsally, with deep grooves on epithelium; subsequent chaetigers smooth ( Fig. 5B, F ). Deep lateral groove (LG) on peristomium and chaetigers 1–4 ( Fig. 5C ). Chaetigers 1–4 not biannulate, slightly rectangular, straight, 1.2x wider than long, chaetiger 4 the widest, with deep intersegmental groove ( Fig. 5A, F, G ). Chaetigers 5–11 not biannulate, square-like, as wide as long, straight, with deep intersegmental groove ( Fig. 5A, F, G ). Chaetal bundles numerous (~30 chaetae) and dorso-lateral throughout thorax; deep and large cavity of capillaries insertion ( Fig. 5F–G ). Chaetae emerging from middle of chaetiger. Lateral organs very small, visible only after staining. A pair of genital pores between chaetigers 7/8, 8/9, 9/10, 10/11, 11/12, and 12/13 ( Fig. 5F ). Transition between thorax and abdomen very subtle, marked by Methyl Green staining and slightly change in shape of chaetigers.

Table 3. Selected morphological characteristics of all described Polymastigos species.

Abdomen rounded, with capillaries on notopodia up to chaetiger 24 and hooded hooks on neuropodia of all abdominal chaetigers ( Fig. 5D, G ). Chaetigers 1.2x wider than long ( Fig. 5D–E ). Chaetae and hooded hooks emerging from last third of chaetiger. Notopodial lobes absent on chaetigers with capillaries ( Fig. 5D ); small, poorly developed, and dorso-lateral on chaetigers with hooded hooks (~10 hooded hooks each fascicle). Neuropodial lobes small, poorly developed, and ventral; distance between lobes reduced along the abdomen (~40 hooded hooks each fascicle) ( Fig. 5E ). Noto-and neuropodial hooded hooks with two rows of teeth above main fang (2–1), main fang slightly curved, large, and with a rounded tip; narrow and smooth hood ( Fig. 5H–I ). Branchiae unknown. Pygidium unknown.

Variation. Incomplete paratypes ranged from 14–17 mm long, 1.2–1.5 mm wide, and 24–31 chaetigers. Juveniles (<0.5 mm wide) presented hooded hooks on the last 2–3 thoracic neuropodia, transition between thorax and abdomen not distinguishable, and tessellation not evident. On paratype 1 and 2, abdominal capillaries occurred up to chaetiger 20 and 19, respectively.

Methyl Green staining pattern (MGSP). Thorax staining darker than abdomen, abdomen staining light green without any evident pattern. A dark and thin band on anterior margin of chaetiger 4 present ( Fig. 5F–G ). The posterior region (posterior to chaetal bundle) of chaetiger seven up to anterior region (anterior to chaetal bundle) of chaetiger 11 staining darker than the remaining ones ( Fig. 5F–G ). Chaetiger 11 with a dark and thin band near the division with chaetiger 12 ( Fig. 5F–G ).

Remarks. Polymastigos profundus sp. nov. is characterized by having body rounded, peristomium and chaetigers 1–3 strongly tessellated dorsally, with deep grooves on epithelium; peristomium and chaetigers 1–4 with a deep lateral groove; palpode present; and transition between thorax and abdomen very subtle. Both known species of Polymastigos are different from the new species by the presence of capillaries on noto- and neuropodia of chaetiger 11, evident transition between thorax and abdomen, and body being flattened rather than rounded. These three species also differ on the number of abdominal chaetigers bearing capillaries, which is 2–7 (chaetiger 12–13 to 12–18) on P. javaensis , 6–12 (chaetiger 12–17 and 12–23) on P. reishi , and 8–13 (chaetiger 12–24 to 12–24) on P. profundus sp. nov. Additionally, juveniles from both known species lack capillaries on abdomen and in contrast, juveniles from the new species bear capillaries on abdomen. Lastly, both known species present genital pores between chaetigers 7/8, 8/9, 9/10, 10/11; however, the new species presents genital pores between chaetigers 7/8, 8/9, 9/10, 10/11, 11/12, and 12/13. Besides the description of P. reishi states that genital pores end on division of segments 10 and 11, Green’s drawing (Fig. 29D, 328) suggests also a genital pore between segments 11 and 12. The maximum body width recorded for Polymastigos profundus sp. nov. was higher (1.5 mm) than the body width recorded for P. reishi (1.1 mm) and P. javaensis (1.2 mm). Therefore, the higher number of intersegments with genital pores on P. profundus sp. nov. may be due to the higher body size of these specimens compared with the both known species.

Etymology. Profundus is a latin word that means “deep”. This species was named after its depth of occurrence, since it is the one recorded in greater depth among the described species.

Habitat. Deep-sea regions (990–1361m), in soft-bottoms.

Type locality. Espírito Santo Basin, Southwest Atlantic Ocean (19°3'27''S 37°48'41"W) .

Distribution. Southwest Atlantic Ocean: Espírito Santo Basin ( Brazil).

Figures

FIGURE 5. Polymastigos profundus sp. nov. (A) Thoracic region, lateral view; (B) Anterior end, lateral view; (C) Abdominal region; lateral view; (D) Abdominal region; dorsal view; (E) Abdominal region; ventral view; (F) Methyl Green staining pattern, lateral view; (G) Methyl Green staining pattern, ventral view; (H) Notopodial hooded hook, frontal view; (I) Neuropodial hooded hook, frontal view. A: abdomen. Ch: chaetiger. GP: genital pores. LG: lateral groove. NeL: neuropodial lobe. NoL: notopodial lobe. Pa: palpode. Pb: proboscis. Pe: peristomium. Pr: prostomium. T: thorax. White arrows: genital pores. Scale bars: A, F, 1 mm; B, E, 0.2 mm; C, D, G, 0.5 mm; H, I, 5 µm.