Bhawatsonia purpurea ( Rioja, 1947 ) Cruz-Gómez, 2021

Cruz-Gómez, Christopher, 2021, A new genus and seven new species of chrysopetalids (Annelida, Chrysopetalidae) from the Tropical Eastern Pacific, Zootaxa 5068 (1), pp. 1-59 : 33-35

Bhawatsonia purpurea ( Rioja, 1947) n. comb.

Figs 16–17 , 26

Type locality: El Mogote, La Paz Bay, Baja California Sur.

Neotype locality: El Caimancito Beach, La Paz Bay, Baja California Sur.

Type material. Neotype: ECOSUR-265 , El Caimancito Beach , La Paz Bay , Baja California Sur, México, Gulf of California, on rock, 1 m, March 2, 2004, coll. MTH & PSS. Paraneotypes: ECOSUR-266 , 3 spec. same data as holotype. ECOSUR-267 , 3 spec. El Presidente, La Paz Bay, October 10, 1987, coll. SSV.

Additional material. Twenty specimens. Baja California: ECOSUR-2120 , 2 spec. Cerro Tiburones , May 7, 1981 , coll. HA; ECOSUR-2988 , 2 spec. Bahía de Los Ángeles , March 17, 1985, coll. Lalo & Carolina ; ECO- SUR-PXXX, 3 spec. Bahía de Los Ángeles , May 25, 1986 , coll. SSV. Baja California Sur: ECOSUR-2992 , El Caimancito Beach, La Paz Bay , on rocks, 1 m, March 2, 2004 , coll. MTH & PSS; ECOSUR-2984 , La Paz Bay , 1 m, March 2, 2004 .

Description. Based on the neotype: complete with 87 segments. TL= 15.1 mm, TW= 2.7 mm. Body stiffed, long, narrowed posteriorly. Body dark violet to brown, dorsal and ventral cirri bases darker ( Fig. 16A ). Paleae fan bright maroon to bright golden, non-imbricated dorsally.

Prostomium retracted among the first six segments. Lateral antennae long, inserted on antero-ventral prostomial margin, median antenna slightly shorter than lateral ones, inserted in front of anterior eyes. Eyes red-violet, two pairs. Nuchal organ, semicircular nuchal fold, partially covering prostomium ( Fig. 16B ). Palps short, ovoid, visible only in ventral view. Mouth fold small, placed between 3 and 4 segments. Pharynx eversible, not exposed, stylets thick.

Parapodium from segment 51, notochaetae in three main groups ( Fig. 16E ). Notochaetae: lateral group inserted below notaciculum, 1–2 paleae, very slender and symmetrical, with 2–3 internal ribs ( Fig. 16F ); subunit 1, 1–2 paleae, slender and symmetrical with 8–10 internal ribs ( Fig. 16G ). Main group, 11–15 paleae, broad and symmetrical, with 17–21 (23) internal ribs and slightly serrated margins ( Fig. 16H ). Median group, 3 paleae short, wide, asymmetrical, margins serrated; the distal-most palea with 12–14 (16) internal ribs and 3 raised ribs, the next proximal palea smaller with 11–12 internal ribs, and the proximal-most and smallest with 10 internal ribs ( Fig. 16I ).

Neuropodium conical, larger than notopodium. Neurochaetae: unit 1, 2 superior spinigers, blades straight and long, 10–11 times longer than wide ( Fig. 16J ). Unit 2, 7–9 falcigers, blades straight and short, 2–3 times longer than wide ( Fig. 16K ). Unit 3, 3–7 falcigers, blades straight and short, 3–4 times longer than wide ( Fig. 16L–M ). Unit 4, 2 falcigers, blades straight and medium-sized, 6–7 times longer than wide ( Fig. 16N ). Blades bidentate, bended distally. Pygidium regenerated, rounded with two anal cirri ( Fig. 16C ; 17A ). Oocyte size: 11.5–14.6 µm (n=4) ( Fig. 16D ).

Habitat. Intertidal to subtidal (1–6.1 m). Specimens of B. purpurea n. comb. were collected on rocks and previously as epibiont of stony coral, and bivalves as Spondylus sp. and Pinna sp. ( Rioja 1947; Cruz-Gómez & Bastida-Zavala 2018). One complete specimen from La Paz Bay (ECOSUR-2992) was found inside of a sand tube ( Fig. 17B–D ).

Distribution. From Cerro Tiburones, Baja California to La India Beach, Oaxaca ( Fig. 26 ).

Remarks. Bhawatsonia purpurea n. comb. is a chrysopetalid rarely recorded, but its records include both coast of America: in the Pacific side from Baja California Sur ( Rioja 1947) and Oaxaca ( Cruz-Gómez & Bastida-Zavala 2018), and in the Caribbean, from Cuba ( Rullier 1974). However, the latter record needs to be confirmed.

This species has a complicated taxonomic history (summarized by Cruz-Gómez & Bastida-Zavala 2018), mainly due to the supposed relevant features considered in the original description, such as the prostomium, based on which it was established in Paleanotus ( Rioja 1947) . When other features were considered, like the numerous segments, paleae, and body shape, it was related to Bhawania ( Perkins 1985) . Until this study, the generic status of the species was not clear. In addition, type material designated by Rioja is currently lost ( Salazar-Vallejo 1989) ( ICZN 1999, Art. 75.3.4). In order to solve the taxonomic status of B. purpurea n. comb., designation of a neotype was necessary ( ICZN 1999,Art. 75.1;Art.75.3.1).The specimen selected as neotype fits with the original description by Rioja (1947) ( ICZN 1999, Art. 75.3.3); specimens features were described, illustrated and, compared to related species ( ICZN 1999, Art. 75.3.2). Because the type locality (El Mogote, La Paz Bay) has been modified ( ICZN 1999, Art. 76.3), the neotype specimen was collected nearby (El Caimancito Beach, La Paz Bay) approximately 4 km from the type locality, thus the environmental conditions were similar ( ICZN 1999, Art. 75.3.6). The neotype, paraneotypes and non-type specimens were deposited in the reference collection at ECOSUR ( ICZN 1999, Art. 75.3.7).

Specimens of B. purpurea n. comb. resemble those of B. nenoae n. sp. in having slender main paleae and broad median paleae. However, specimens of B. purpurea n. comb. have main paleae with consistent width along the margins and narrower shoulders, whereas B. nenoae n. sp. has main paleae with their upper middle section broader, and wider shoulders. Regarding subunit 1 paleae, specimens of B. pupurea n. comb. possess a slender palea with a range of 8–10 internal ribs, while specimens of B. nenoae n. sp. possess a broader palea with a range of 12–14 internal ribs. Further, some specimens of B. purpurea n. comb. stand out among Bhawatsonia n. gen., and other Chrysopetalinae genera, in having the largest specimens with numerous segments, up to 400. A paratype from La Paz Bay (ECOSUR-266) was the largest one examined; it has a total length of 12.64 cm and up to 400 segments.

Figures

FIGURE 16. Bhawatsonia purpurea n. comb., neotype (ECOSUR-265). A) Complete fragmented body, arrow indicates protruding ventral longitudinal muscular fibers. B) Drawing of prostomium, dorsal view. C) Drawing of regenerated posterior segments, ventral view; arrow indicates pygidium. D) Oocyte. E) Parapodium from segment 51. I) Lateral palea. G) Subunit 1. H) Main palea. I) Median palea. J) Unit 1. K) Unit 2. L–M) Unit 3. N) Unit 4. Scales: 5 µm (D), 10 µm (GJKLMN), 20 µm (FI), 50 µm (H), 100 µm (BC), 200 µm (E), 1 mm (A).

FIGURE 17. Bhawatsonia purpurea n. comb., neotype (ECOSUR-265). A) Regenerated posterior segments, ventral view; arrow indicated pygidium. Non-type specimen (ECOSUR-2992). B) Specimen sheltered inside a sand tube. C) Sand tube from B. D) Complete specimen removed from sand tube. Scales: 100 µm (A), 1 mm (BCD).

FIGURE 26. Previous and new records of chrysopetalids in the Tropical Eastern Pacific. Empty symbols indicate historic records.