Asclerocheilus geiseae, Mendes & Paiva & Rizzo, 2024

Mendes, Samuel Lucas Da Silva Delgado, Paiva, Paulo Cesar De & Rizzo, Alexandra E., 2024, On species of Asclerocheilus Ashworth, 1901 (Annelida: Scalibregmatidae) from Brazil, European Journal of Taxonomy 947, pp. 88-108 : 92-96

Asclerocheilus geiseae sp. nov.

urn:lsid:zoobank.org:act:1FAE1F5A-0E5E-4F38-8DF1-726A8F981D18

Figs 1–3

Diagnosis

Triangular prostomium, with two long horns, both thin and projected upwards. Eyes absent. Ventral groove present from chaetiger 1 with first pad asymmetrically rounded, contributing to mouth’s lower lip formation. Acicular spines present on chaetigers 1–3 on notopodia, and 1–2 on neuropodia. Short spinous chaetae not observed. Lyrate chaetae present from chaetiger 2 on neuropodia and 3 on notopodia. Anterior chaetigers parapodial lobes larger, more prominent, present as broad blunted projection in both noto- and neuropodia. Pygidium present as short uniannulated segment, with crenulated margin.

Etymology

The specific epithet ‘ geiseae ’ was chosen to honour the Brazilian mastozoologist Dr Lena Geise, from the Rio de Janeiro State University (UERJ), for her important contributions to Brazilian zoology and to celebrate our friendship.

Type material

Holotype

BRAZIL – Espírito Santo, Espírito Santo Basin • complete spec.; 19.959° S, 39.892° W; depth 11 m; Dec. 2010; van Veen grab; subtidal zone; UERJ, UERJ-8065 .

Paratypes

BRAZIL – Espírito Santo, Espírito Santo Basin • 1 complete spec., 1 incomplete spec.; 19.960° S, 39.892° W;depth 11 m; Dec. 2010; van Veen grab; subtidal zone; UERJ, UERJ-8066 • 1 complete spec.; 19.9590° S, 39.893° W; depth 47 m; Jul. 2011; van Veen grab; subtidal zone; UERJ, UERJ-8067 • 1 complete spec.; 19.959° S, 39.892° W; depth 47 m; Dec. 2010; van Veen grab; subtidal zone; UERJ, UERJ-9223 • 1 complete spec.; 19.959° S, 39.892° W; depth 47 m; Dec. 2010; van Veen grab; subtidal zone; UERJ, UERJ-9224 .

Description

Holotype complete, 10 mm long, 1 mm wide over expanded region, 0.3 mm wide on narrowest region for 57 chaetigers. Medium-sized species, paratypes measuring 4–5 mm long, 0.4–0.6 mm wide expanded on anterior region, 0.13–0.25 mm wide on narrowest posterior region, for 32–44 chaetigerous segments. Body arenicoliform, weakly expanded over chaetigers 2–19. Colour in alcohol pale tan. Body surface covered by secondarily annulated rings. Secondary annuli composed by rounded to rectangular small pads, basally fused to each other, in both anterior and posterior regions. Annuli’s small pads on anterior region may be weaker in comparison to posterior region. Internal glands were not observed.

Triangular prostomium, with two long horns, both thin and projected upwards ( Figs 1A–B , 2B , 3A–B ). Eyes absent. Nuchal organs not observed. Peristomium achaetous, uniannulated in holotype, but some paratypes presented a peristomium biannulated ventrally and uniannulated dorsally. Proboscis smooth. Mouth’s lips presenting single row of paired lobes formed superiorly by peristomium and inferiorly by ventral groove first pad. Upper lip presents 5–6 lobules, lower lip presents 5–7 lobules. Ventral groove present from chaetiger 1 with first pad asymmetrically rounded, contributing to mouth’s lower lip formation on its superior margin ( Figs 1A–B , 3A–B ). Quadrangular bi- to triannulated pads present from chaetiger 2, forming ventral mid-ridge up to end of the body. Each pad is paired to a single chaetiger. Posterior pads thinner than anterior ones.

Dorsally, chaetiger 1 with two secondary annuli connected to parapodial lobe, plus an intermediate annulation between chaetigers ( Figs 1A–B , 3A–B ); following chaetigers with three secondary annuli connected to parapodial lobe, and an intermediate annulation between chaetigers ( Fig. 2A, D ). Ventrally, chaetigers 1–4 with two secondary annuli connected to parapodial lobes, plus an intermediate annulation between chaetigers ( Figs 1A–B , 3A–B ). Following chaetigers on anterior region with three secondary annuli connected to parapodial lobe, and also an intermediate annulation between chaetigers ( Fig. 3A ). First and second chaetigers often smooth, but this variation should be interpreted as artefact. Interramal papillae rounded, present from anterior chaetigers ( Fig. 2A ), smaller and sometimes absent in posterior chaetigers ( Fig. 2D ), internal content unknown.

Acicular spines present on chaetigers 1–3 on notopodia, and 1–2 on neuropodia ( Figs 1C–D , 2B–C , 3C ). Short spinous chaetae not observed. Lyrate chaetae present from chaetiger 2 on neuropodia and 3 on notopodia ( Figs 1E , 2E , 3D ), numbering 5–6 lyrate chaetae per fascicle, with unequal tynes (tynes ratio: 2.5 on anterior chaetigers to 1.8–2.22 on midbody to posterior chaetigers).

Notopodial acicular chaetae organized in two rows on chaetigers 1–2, numbering up to 9 per row, with rounded tips ( Figs 1C , 2B , 3C ). Notopodial acicular chaetae on chaetiger 3 organized in single row, numbering 5 transitional acicular spines, with pointed tips. Neuropodial acicular spines weaker than notopodial ones, organized in single row on chaetigers 1–2, all curved with pointed tips ( Figs 1D , 2C ), numbering 8 per fascicle, transitional on chaetiger 2. Capillaries organised in single row on chaetigers 1–2, then in two rows on chaetiger 4 up to middle of body. In posterior chaetigers, capillaries become organized in single row.

Anterior chaetigers parapodial lobes larger, more prominent, present as broad blunted projection in both noto- and neuropodia, more robust and distinct than on posterior chaetigers ( Fig. 2A ). Parapodial lobes becoming gradually thinner and smaller in midbody and posterior chaetigers, emerging as apically rounded projections ( Fig. 2D ). Pygidium present as short uniannulated segment, with crenulated margin, from which emerges 4 long anal cirri; two dorso-lateral and two ventro-lateral ( Fig. 3E ).

Remarks

This species is morphologically similar to A. intermedius , A. shanei , A. abyssalis and A. blakei sp. nov. by having acicular spines on notopodia of chaetigers 1–3. However, it is unique among them by the presence of acicular spines with rounded tips in two rows on notopodia of chaetigers 1–2, then replaced by one row of acicular spines with pointed tips on notopodia of chaetiger 3. Moreover, A. abyssalis is the only species of the genus with short spinous chaetae mentioned on its description.

Ecology

This species was found at the Rio Doce river mouth near the Campos Basin (Brazilian southern region), living on sandy sediment at depths of 11– 50 m.

Figures

Fig. 1. Asclerocheilus geiseae sp. nov., holotype (UERJ-8065), schematic representation. A. Ventral view of anterior region. B. Lateral view of anterior region. C. Acicular spine with rounded tip present on chaetigers 1–2. D. Acicular spine with pointed tip present only on chaetiger 3. E. Lyrate chaeta. Abbreviations: see Material and methods.

Fig. 2. Asclerocheilus geiseae sp. nov., paratype (UERJ-8066), under optical microscopy, specimens stained with Shirlastain A. A. Latero-ventral view of anterior body. B. Acicular spines with rounded tips. C. Acicular spine with pointed tip. D. Mid-body chaetigers in lateral view. E. Lyrate chaetae. Abbreviations: see Material and methods.

Fig. 3. Asclerocheilus geiseae sp. nov., under SEM. A. Ventral view of anterior body. B. Prostomium and peristomium in ventral view. C. Acicular spines with rounded tips. D. Lyrate chaetae. E. Ventral view of posterior most chaetigers and pygidium, only two cirri are present, the others were lost in this specimen. Abbreviations: see Material and methods.