Asclerocheilus tropicus Blake, 1981

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 : 101-103

Asclerocheilus tropicus Blake, 1981

Fig. 7

Asclerocheilus tropicus Blake, 1981: 1133 , figs 1a–c.

Material examined

BRAZIL – Espírito Santo, Espírito Santo Basin • 1 incomplete spec.; 19.765° S, 39.507° W; depth 150 m; Jan. 2012; box corer; continental slope; UERJ-9244 • 2 complete specs; 19.601° S, 39.176° W; depth 143 m; Jun. 2013; van Veen grab; continental slope; UERJ, UERJ-4622 .

Description

Medium- to small-sized specimens; 3.5–5 mm long, 0.1–0.5 mm wide for 13–34 chaetigers. Prostomium with two large flaring lobes ( Fig. 7A–B ). When present, eyes as broad obliquely longitudinal lines, with orange coloration, positioned near posterior margin of prostomium. Peristomium uniannulated, smooth. First chaetigers biannulated; then tri- to quadriannulated from midbody to posterior chaetigers.

Acicular spines on notopodia of chaetiger 1, numbering 5–6, present in two rows ( Fig. 7C ). Short spinous chaetae absent. Lyrate chaetae from chaetiger 2 ( Fig. 7D ), with unequal tynes (tynes ratio = 1.8–2.1), present in single row anterior to capillaries, numbering 3–5. Capillaries organized in two rows on anterior to midbody chaetigers then in single row on posterior chaetigers. Two specimens lack posterior end, but one presented short pygidial margin, without cirri.

Remarks

The specimens collected during the research campaigns material agree in their morphological and ecological features those described by Blake (1981) and Nogueira (2002). Importantly, Nogueira (2002) confirmed his identifications comparing the Brazilian specimens with type material of A. tropicus . Here, we expand the distribution of the species to the Espírito Santo and Campos basins. Interestingly, the variation regarding the presence of a sulcus separating the prostomial lobes was also observed in some specimens, with the prostomium lacking a clear separation from them, even under staining ( Fig. 7A–B ). On the other hand, the number of acicular spines ( Fig. 7C ) and lyrate chaetae ( Fig. 7D ) did not reach the maximum number reported by Nogueira (2002) but agreed in overall shape. Regarding the body annulation, most specimens were in poor state, hampering a clear distinction of secondary annuli in most chaetigers. In the light of the abovementioned considerations, the specimens did not present enough variability to justify their separation from A. tropicus sensu Nogueira (2002) . Further studies exploring the identity of this species using molecular data are needed, considering its Pacific and South Atlantic records, both confirmed by morphology.

Ecology

We found specimens living on the continental shelf of the Espírito Santo and Campos basins, in a bathymetric range up to 157 m deep. This find is relevant, because we expand its bathymetric distribution, considering the previous accounts based on records of specimens living in shallow subtidal waters ( Blake 1981; Nogueira 2002).

Figures

Fig. 7. Asclerocheilus tropicus Blake, 1981 (UERJ 9244), under optical microscopy, specimens stained with Shirlastain A. A. Anterior region in ventral view. B. Anterior region in ventral view, emphasizing the prostomium and first chaetiger. C. Acicular spines on chaetiger 1. D. Lyrate chaetae from a posterior chaetiger. Abbreviations: see Material and methods.