Paraehlersia knysnaensis sp. nov.

urn:lsid:zoobank.org:act: BFA1DCAC-364D-40D2-88DA-2E2207C7073D

Figs 13–16

non Syllis (Langerhansia) ferruginea Langerhans, 1881 – Day 1967a: 244, fig 12.20–r.

Etymology

The species name ‘ knysnaensis ’ is dedicated to the type locality at Knysna Estuary, South Africa.

Type material

Holotype SOUTH AFRICA • entire specimen; Knysna Estuary, Railway; 34°2ʹ23.65ʺ S, 23°2ʹ6.49ʺ E; Jul. 2021; Arturo Álvarez-Aguilar and Danne Pretorius leg.; intertidal, soft sediments; fixed in 4% seawater formalin, preserved in 70% ethanol; SAM–A089279.

Paratypes SOUTH AFRICA • 2 anterior fragments; Knysna Estuary, Railway; 34°2ʹ23.65ʺ S, 23°2ʹ6.49ʺ E; Jul. 2021; CEAB AP 1006A • 2 entire specimens; same collection data as for preceding; Jul. 2021; CEAB AP 1006B • 2 entire specimens, 3 anterior fragments; same collection data as for preceding; May 2021; SAMC–A089213 • 1 entire specimen; same collection data as for preceding; Jan. 2021; SAM–A089280 • 1 specimen, prepared for SEM; same collection data as for preceding; Jan. 2021; CEAB AP 1006C • 1 specimen lacking posterior end; Bollard Bay; 34°2ʹ37.33ʺ S, 23°3ʹ59.65ʺ E; Jul. 2021; SAM–A089281 • 5 entire specimens, 2 anterior fragments; Reserve; 34°3ʹ31.80ʺ S, 23°2ʹ2.18ʺ E; Jul. 2021; SAM– A089282 • 1 anterior fragment; The Point; 34°2ʹ21.32ʺ S, 23°0ʹ45.01ʺ E; Jan. 2021; SAM–A089283 • 1 entire specimen, 1 in two fragments; Thesen Island Bridge; 34°2ʹ39.01ʺ S, 23°2ʹ52.19ʺ E; May 2021; SAMC–A089232 • 1 entire specimen, 1 specimen stolonizing; Ashmead; 34°2ʹ39.01ʺ S, 23°2ʹ52.19ʺ E; May 2021; SAM–A089291 • 1 entire specimen; same collection data as for preceding; Jan. 2021; SAM– A089285 • 1 entire specimen; Brenton; 34°3ʹ31.80ʺ S, 23°2ʹ2.18ʺ E; Jan. 2021; SAM–A089286 • 1 specimen prepared for SEM; same data as for preceding; Jul. 2021; CEAB AP 1006D • 1 entire specimen; Thesen Island Bridge; 34°2ʹ39.01ʺ S, 23°2ʹ52.19ʺ E; Jan. 2021; SAM–A089284 • 2 specimens prepared for light microscopy; same data as for preceding; Jul. 2021; CEAB AP 1006E.

Other material examined

SOUTH AFRICA • 1 complete, 3 incomplete specimens (2 stolonizing); Saldanha Bay, UCT Ecological Survey, station SB183N; 33°2’30”S, 17°58’42”E; 29 Apr. 1959; fixed in 4% seawater formalin, preserved in 70% ethanol; SAM-MB-A060273 • 1 incomplete specimen; False Bay, Oatland Point, UCT Ecological Survey; station FAL149 V; 34°11’48”S, 18°27’16”E; 12 Mar. 1953; SAM-MB-A020798.

Description

Body long and thin, but highly variable in length, 6.52 (4.1–12) mm long, 0.36 (0.31–0.73 mm wide, with 59 (55–65) chaetigers (Figs 13A–B, 15A–B). Prostomium small, oval to sub-pentagonal, with four eyes and two anterior ocular spots (Figs 13B–D). Palps large, triangular, ⅔ as long as prostomium, fused at bases, with a distinct groove (Fig. 13A–D). Lateral and median antennae pseudo-articulated (Figs 13B, D, 15C–D). Tentacular segment shorter than following ones (Figs 13D, 15C–D). Dorsal tentacular cirri pseudo-articulated, slightly longer than ventral one, as long as median antenna; ventral tentacular cirri pseudo-articulated (Figs 13B–D, 15C–D). Dorsal cirri slender, elongated, whip-shaped, alternating long and short all along body, smooth except first that is slightly pseudo-articulated distally (Figs 13B–F, 15C–F). Dorsal cirri of chaetiger 1 as long as body width, of chaetiger 2 ⅓ of body width, of chaetiger 3 ⅓ of body width, of chaetiger 4 half of body width (Figs 13C–D, 15C), then alternating ⅓ and half body width along most of body (Figs 13E, 15E), to as long and half body width in posteriormost segments (Figs 13F, 15G). Anterior dorsal cirri with a short sub-cirral papilla at bases of cirrophores and a fossa between cirrophore and papilla (Fig. 16A). Parapodial lobes conical with round tips (Figs 13B–F, 15C–F). Ventral cirri as long as parapodial lobes, anterior ones lanceolate, with round tips, posterior and midbody triangular with elongated tips (Figs 13H–I, 15B, D, F, H). Anterior parapodia with 20–30 compound chaetae mostly falcigers; 4–6 spinigers of two lengths; number of chaetae reducing towards posterior segments (Figs 14A, 16B, G, K). Anterior parapodia with falcigers with short, bidentate blades, most dorsal 18 μm long, most ventral 14 μm, with a very small subdistal tooth, and few thick marginal spines (Figs 14A–B, 16B–D); spinigers long, filiform, 2–3 with blades ca 90 µm long, 2–3 with blades ca 50 μm long, distally bifid, visible only under SEM, with short marginal spines (Figs 14A, C, 16B, E). Midbody parapodia compound chaetae with 5–10 falcigers, ca 15–17 μm long, similar to anterior ones in mid-anterior parapodia (Fig. 16H), progressively changing to show two different forms: thick, ⅔ as thick as thin, with subdistal tooth much larger than distal one (Figs 14D, 16I–J) and thin, with subdistal tooth slightly larger than distal one (Figs14E, 16I); all with few thick marginal spines; 2–4 spinigers of two lengths similar to anteriormost parapodia (Figs 14D–G, 16F–G). Posterior parapodia with 3–5 falcigers, 15–17 μm long and varying in thickness; thick ¼ as thick as thin, with subdistal tooth much larger than distal one (Figs 14H, 16L), thin with subdistal tooth slightly smaller than distal one (Figs 14I, 16L); all with few thick spines on margin (Figs 14H–I, 16L); two spinigers of similar length (60–65 µm), similar in shape to anteriormost parapodia, apparently unidentate (Figs 14K, 16K, M). Dorsal simple chaetae on most posterior segments, slightly curved, with slightly serrated margin, distally bidentate, both teeth short, broad, upwards directed (Figs 14L, 16N–O); ventral simple chaetae on most posterior segments, markedly bidentate, both teeth acute, large, subdistal slightly longer than distal one, apparently smooth (Figs 14M, 16P). Three aciculae in anterior parapodia, two straight with slightly inflated, acuminate tip, one with round tip bent in oblique angle (Fig. 14N); two aciculae in midbody parapodia, one straight with slightly inflated, acuminate tip and one with round tip bent in oblique angle (Fig. 14O); one acicula in posterior parapodia, with round tip bent in oblique angle (Fig. 14P–Q). Pharynx with a small pharyngeal tooth close to anterior margin, similar in size (Fig. 13C) or slightly longer (Fig. 13B, D) than proventricle, extending through 6–7 segments; proventricle through 4–7 segments with 26 (25–27) muscular rows. Pygidium small, triangular, with two very long, smooth, whip–shaped anal cirri; pygidial appendix triangular (Figs 13B, F, 15G–H).

Distribution

South Africa. Western Cape Province: west coast (Saldanha Bay, False Bay) and southern coast (Knysna Estuary).

Remarks

Paraehlersia knysnaensis sp. nov. differs from all previously known species in the genus in having two types of spiniger chaetae (long and short) and falciger blades with the distal tooth much longer than the subdistal one in anterior parapodia, while all other species have spinigers with either a graduating length or with similar lengths and falcigers with both teeth similar in size. Also, P. knysnaensis has two types of falcigers (thin, with teeth of similar size and thick, with subdistal tooth much larger than distal one) in midbody posterior parapodia, while all other species have only falcigers corresponding to the thick type, with subdistal tooth either slightly or much larger than distal one.

Paraehlersia pamelae Prado & San Martín, 2024, from the Alboran Sea, shares with P. knysnaensis sp. nov. the shape of simple chaetae and aciculae, as well as the small size of the pharyngeal tooth, but P. pamelae has a shorter body (3.52 mm and 4.1–12 mm long, respectively) and the pharynx is longer than proventricle (similar in size or slightly longer in our species) (Prado & San Martín 2024).

Paraehlersia ferrugina (Langerhans, 1881), from the Canary Islands, has the ventral simple chaetae with subdistal tooth much longer than distal one and up to eight aciculae with truncated tips in anterior region (San Martín 2003), while the subdistal tooth in the ventral simple chaetae is only slightly longer and the aciculae are not so numerous and have rounded tips in P. knysnaensis sp. nov. Paraehlersia ferrugina was also reported from South Africa by Day (1967a), but the specimens differ from P. knysnaensis in shape of falciger and spiniger chaetae. Paraehlersia ferrugina was first reported from South Africa in Day (1960), which did not include any illustration or descriptive notes —only a mention that it was a new record for the country. Day (1967a) cited only his earlier work (Day 1960) as the reference for this identification. We have examined this material and it matched P. knysnaensis in all diagnostic features. Notably, the shape of both falcigers and spinigers were inaccurately represented in Day (1967a). In particular, the marginal teeth of anterior falcigers, as well as those at the base of posterior falcigers, are significantly more pronounced than depicted.

Paraehlersia articulata (Kudenov & Harris, 1995), from the Santa Barbara Channel (California), has aciculae with diamond shaped tips (round in P. knysnaensis sp. nov.) and a proventricle with slightly less muscular cell rows (22–24 vs 25–27) (Kudenov & Harris 1995).

Paraehlersia longichaetosa Fukuda, Centurión, Nogueira & San Martín, 2012, from offshore Banco Sarmiento (Argentina), has filiform dorsal cirri (whip-shaped in P. knysnaensis sp. nov.), ventral cirri shorter than parapodial lobes (equally long in P. knysnaensis), bidentate ventral simple chaetae with a clear distal serration (smooth in P. knysnaensis), and single posterior acicula with irregularly inflated tips (round, bent at oblique angle in P. knysnaensis) (Fukuda et al. 2012).

Paraehlersia martapolae Fukuda, Centurión, Nogueira & San Martín, 2012, from São Paulo (Brazil), has ventral cirri shorter than parapodial lobes (similar in length in P. knysnaensis sp. nov.), pharynx longer than proventricle, through 9–12 segments (similar in size to proventricle, through 6–7 segments in P. knysnaensis), and proventricle shorter than pharynx, extending through 5–6.5 segments with 21–24 muscular rows (as long as proventricle, through 4–5 segments, with 25–27 muscular rows in P. knysnaensis) (Fukuda et al. 2012).

Paraehlersia dionisi (Núñez & San Martín, 1991), from the Canary Islands, has dorsal simple chaetae with heavily serrated margin (slightly serrated margin in P. knysnaensis sp. nov.), aciculae with rounded tip ending in a lateral, short mucron (with round, non-mucronate tip in P. knysnaensis), and proventricle shorter than pharynx, extending through seven segments and with 30 muscular rows (similar in length to pharynx, extending through 4–5 segments, and 25–30 muscular rows in P. knysnaensis) (Núñez & San Martín 1991).

Paraehlersia kawesqar Soto & San Martín, 2018, from Concepción Channel (Chile), has ventral cirri shorter than parapodial lobes (similar in length to parapodial lobes in P. knysnaensis sp. nov.), acicula distally acuminated (with round tip, bent in oblique angle in P. knysnaensis), pharynx shorter than proventricle extending through 7–9 segments (similar, 6–7 segments in P. knysnaensis), proventricle extending through 14–15 segments (4–5 in P. knysnaensis) (Soto & San Martín 2018).

Paraehlersia ehlersiaeformis (Augener 1913), from Shark Bay (Australia), has ventral cirri shorter than parapodial lobes (longer than parapodial lobes in P. knysnaensis sp. nov.), dorsal simple chaetae slightly truncated (bidentate in P. knysnaensis), ventral simple chaetae with proximal tooth slightly hooked (both teeth acute in P. knysnaensis), acicula in anterior parapodia with acuminate or lancet-shaped tip (round in P. knysnaensis) and solitary with oblique tip in midbody and posterior parapodia (straight, with rounded tip in P. knysnaensis), pharynx longer than proventricle (similar in P. knysnaensis), and proventricle with 21–22 muscular rows (25–27 in P. knysnaensis) (San Martín & Hutchings 2006).