A closer look at the taxonomic and genetic diversity of endemic South African Marphysa Quatrefages, 1865

Sample collection

Specimens were collected at the fringing intertidal zones from eight open-coast sites along the KwaZulu-Natal and Eastern Cape coasts from 2013 to 2014 (n = 32) and in 2019 (n = 29), including an isolated population from rock crevices on the muddy banks of the Mzingazi canal in Richards Bay (Fig. 1). Whole specimens were preserved in 96% ethanol. Collection was approved by the Department of Forestry, Fisheries and the Environment in South Africa under permit numbers RES2013/13, RES2014/06 issued to Angus Macdonald and RES2019/49 issued to Carol Simon.

Morphological examination

Type material of Marphysa corallina, specimens identified as M. corallina deposited at the Iziko South African Museum and newly collected specimens were examined and the following characters recorded. Shape of the prostomium, peristomium, anterior body region, maxillary apparatus, parapodia and pygidium, as well as the frequency of branchiae with total number of filaments and the maxillary formula (MF) were recorded. Maxillae I to V (MI, MII, MIII, MIV, MV) were measured according to Molina-Acevedo & Carrera-Parra (2015, 2017). A Leica S9i dissecting and light ICC50W microscopes equipped with built-in cameras were used to photograph characters and plates were edited in Adobe Photoshop 2022 and included in descriptions. Specimens collected in 2013, 2014 and 2019 were deposited at the Iziko South African Museum (MB-A095266–MB-A095297). Comparative material was loaned from the Swedish Museum of Natural History, Stockholm, Sweden (SMNH) and Iziko South African Museum (MB).

Molecular analyses

DNA was extracted from tissue samples of fresh specimens using the ZR Genomic DNA Tissue MiniPrep Plus kit (Zymogen) following the manufacturer’s protocol. DNA was amplified using universal COI primers LCO1490 and HCO2198 (Folmer et al., 1994). Polymerase Chain Reaction (PCR) amplifications followed Kara et al. (2020b). Amplicons were sequenced at the Central Analytical Facility at Stellenbosch University using only the forward primer (LCO1490). Raw sequences were quality controlled to check for errors using BioEdit (v7.2.6) (Hall, 1999).

GenBank sequences of species belonging to Marphysa, Paucibranchia Molina-Acevedo, 2018, Eunice Cuvier, 1817, Palola Gray in Stair, 1847 and Leodice Lamarck, 1818 were included as ingroup taxa together with 32 newly generated sequences in this study (GenBank accession numbers: OQ836443–OQ836473, whilst Hyalinoecia Malmgren, 1867 was used as the outgroup to root the tree (Table 1). The COI dataset was trimmed and aligned using the ClustalW multiple alignment method (Thompson, Higgins & Gibson, 1994) in BioEdit. A nexus file was compiled using Dna-SP v5 (Librado & Rozas, 2009). A best-fit evolution model was calculated using PAUP (Swofford, 2003) and MrModelTest v2.3 (Nylander, 2004). Using the Akaike Information Criterion (AIC), the SYM+G model was used to reconstruct phylogenetic relationships using Bayesian Inference (BI) implemented in MrBayes 3.1.2 (Ronquist et al., 2012). Trees were calculated using four Markov Chains of 5 million generations with every 1,000^th tree sampled. The first 25% were discarded as burn-in and the resulting trees used to build a 50% majority-rule consensus tree. Convergence of runs was assessed through examining the average standard deviation of split frequencies (≤0.01). The plot of likelihood vs the sampled trees and the effective sample sizes (ESS > 200) were analysed using Tracer v1.5 (Rambaut, 2012) to verify the mixing quality of all parameters, both of which were satisfied. Trees were visualised using FigTree v1.4.4 (Rambaut, 2012) and edited in Photoshop. Our analysis was designed to validate species identities and not to assess their phylogenetic relationships.

Inter- and intraspecific genetic distances were computed using the Kimura 2-parameter model (K2P) in MEGA-X (Kumar et al., 2018) and run for 100,000 bootstrap replicates with complete deletion of gaps.

Morphological and molecular comparisons

Detailed morphological comparisons indicate that M. corallina was misidentified in the region, and instead, the specimens correspond to a new species belonging to Treadwellphysa Molina-Acevedo & Carrera-Parra, 2017, and represents the first record for South Africa. Diagnostic characters for this genus are the curvature of the inner base on MI and the elevated inner base of MII together with the ventral cirrus as a transverse welt with a rounded tip (Molina-Acevedo & Carrera-Parra, 2017). These specimens belong to a new species, herein named T. izinqa sp. nov. characterised by having reddish/golden subacicular hooks, a postchaetal lobe varying from digitiform to ear-shaped to inconspicuous, and tridentate falcigers (unique for the genus) of consistent length throughout the body.

COI sequences from Hawaiian M. corallina were not available. Nonetheless, South African sequences formed a distinct clade (intraspecific variation: <1%, BS > 0.95), differing genetically from other sequenced species of Marphysa by 21–25% (Fig. 2).

Our samples revealed another distinct morpho-species, characterised by having red eyes, branchiae with six filaments extending to the posterior end, aciculae varying from black/amber to golden, yellow or brown/golden subacicular hooks blunt or weakly bidentate, and spinigers of similar size all along the body. Accordingly, their sequences correspond to an independent clade (intraspecific variation: <1%, BS > 0.95) (Fig. 2) differing genetically from other sequenced Marphysa by 9–21%. Thus, the species was herein named Marphysa mzingazia sp. nov.

Systematics

Eunicida Dales, 1962

Eunicidae Berthold, 1827

Genus Marphysa de Quatrefages, 1865

Marphysa corallina (Kinberg, 1865)

(Fig. 3)

Material examined. Holotype: one specimen in poor condition, SMNH-Type-429, Hawaiian Islands, Oahu, Honolulu, 21°19′N, 157°52′W, Eugenie Epx. 1851–53 (three vials each with parapodia, and one vial with the maxillary apparatus).

Redescription. Holotype incomplete, with 104 chaetigers, (fragments: anterior = 9 chaetigers, second and third = 19 each, fourth = 2, fifth = 70, sixth = 3), L10 = 6.1 mm, W10 = 3.4 mm. Anterior region with dorsum convex, flat ventrally widest at chaetiger 13, tapering after chaetiger 48. Prostomium bilobed (0.9 mm long, 2.4 mm wide), sulcus anteriorly shallow, dorsally inconspicuous and ventrally deep (Figs. 3A and 3B). Prostomial appendages in a semicircle, median antenna slightly isolated by a gap. Palps reaching second peristomial ring; lateral antennae reaching first chaetiger; median antenna reaching second chaetiger (Fig. 3A). Palpophores and ceratophores short, thick; palpostyles and ceratostyles digitiform, slender, without articulations (Figs. 3A and 3B). Eyes brown, between palps and lateral antennae.

Peristomium (1.5 mm long, 3.6 mm wide) with first ring two times longer than second ring. Separation between rings distinct on all sides. Ventral lip dissected (Figs. 3A and 3B).

Maxillary apparatus in poor condition (Fig. 3C), with MIII, MIV and MV lost; MF = 1+1,4+4, ?+? ?+?, ?+? MI with falcal arch angular shaped and with straight outer edge (Fig. 3C). MI forceps-like, 2.5 times longer than length of maxillary carriers. MII wide, left distal teeth shorter, directed laterally, other teeth recurved; cavity opening oval, MII 3.8 times longer than length of cavity opening (Fig. 3C).

Pectinate branchiae from chaetigers 17L–18R to last chaetiger (Figs. 3F and 3G), with up to five long branchial filaments 5.3 times longer than dorsal cirri.

Dorsal cirri digitiform in anterior chaetigers, conical in following ones; 1.1 times longer than ventral cirri in first chaetigers, similar in length to ventral cirri in median-posterior ones (Figs. 3D–3G). Ventral cirri tongue-shaped in first four chaetigers; with an elongated oval swollen base from chaetiger 5. Prechaetal lobes in first chaetigers with dorsal edge 1.3 times longer than ventral, as transverse fold in following chaetigers (Figs. 3D–3G); chaetal lobes rounded in anterior chaetigers, triangular in following ones (Figs. 3D–3G); postchaetal lobes well developed in first 58 chaetigers; tongue-shaped in first four chaetigers, ear-shaped from chaetiger 5, progressively smaller in following ones (Figs. 3D–3G).

Aciculae blunt, reddish basally, amber distally, up to three aciculae per parapodia (Figs. 3D–3G). Limbate chaetae of two lengths in same chaetiger. Two types of pectinate chaetae: 2–3 isodont pectinate chaetae with wide blade, thin shaft, and up to 11 long, slender teeth (Fig. 3H) in anterior chaetigers; 2–3 pectinate chaetae isodont with narrow blade, thin shaft, and with up to 20–21 short, slender teeth (Fig. 3I) in median chaetigers. Pectinate chaetae from posterior region not observed. Compound falcigers bidentate, with blade of similar lengths in all parapodia, with triangular teeth in anterior region (Fig. 3J) and blunt teeth in posterior parapodia (Fig. 3K). Subacicular hooks starting in chaetigers 30R–32L, present in all parapodia throughout the body, always 2–3 per parapodium; bidentate and translucent with blunt teeth, similar in size (Fig. 3L).

Distribution. Oahu, Hawaii. Specimen records from other regions outside the type locality such as Madagascar, Mozambique, Senegal, the Red Sea, the Mediterranean, Jaluit Athol, Lakshadweep Islands, Australia and New Zealand (Day, 1967; Branch et al., 2022; Veeramuthu et al., 2012; Read & Fauchald, 2023) should be re-examined based on the updated description as it is suspected that these records may represent misidentified species.

Marphysa mzingazia sp. nov.

lsid:zoobank.org:act:6A50F2CF-2DE3-42AC-8B4D-FECC6C04D4BF

(Fig. 4)

Material examined. Holotype. One incomplete specimen (MB-A095294) in 96% ethanol, Richards Bay harbour, KwaZulu-Natal, South Africa, 28°47′09.6″S 32°04′55.8″E, coll. J. Kara and R. Kara, 1 September 2019. Paratypes 1–3. Three incomplete specimens (MB-A095293, MB-A095510, MB-A095292) in 96% ethanol, Richards Bay harbour, KwaZulu-Natal, South Africa, 28°47′09.6″S 32°04′55.8″E, coll. J. Kara and R. Kara, 1 September 2019. Non-type material. Three incomplete specimens (MB-A095295–MB-A095297) in 96% ethanol, Richards Bay harbour, KwaZulu-Natal, South Africa, 28°47′09.6″S 32°04′55.8″E, coll. J. Kara and R. Kara, 1 September 2019.

Description. Holotype incomplete (posterior end used for molecular analysis), measurements before molecular analysis: 205 chaetigers, L10 = 4 mm, W10 = 3 mm, TL = 55 mm. Body rounded anteriorly, becoming dorsoventrally flattened from chaetiger 7–8 (Figs. 4A–4C) to posterior end, widest at chaetiger 25 (2.49 mm), blood red with white antennae when alive, iridescent throughout, chaetigers 1–8 purple/brown, from segment 9 till posterior parapodia, cream (Figs. 4A and 4B), middle to posterior segments, red midline on segments and pinkish-peach pigment on dorsum (Fig. 4B) when preserved.

Prostomium bilobed (0.71 mm long, 1.48 mm wide), lobes frontally rounded, ventral sulcus deep (Figs. 4A and 4C). Prostomial appendages in semicircle, median antenna slightly isolated by a gap (Figs. 4A and 4C). Palps reaching 2^nd peristomial ring, lateral antennae reaching 2^nd chaetiger, median antenna reaching 3^rd chaetiger. Palpophores and ceratophores thick, short and ring-shaped; palpostyles and ceratostyles thick, rounded with conical ends. Pair of red eyes as subdermal patches between palps and lateral antennae (Fig. 4C, red arrows). Peristomium (1.8 mm long, 5.2 mm wide), first ring two times longer than second ring (Fig. 4A); separation between the two peristomial rings distinct on all sides (Figs. 4A and 4C).

Maxillary apparatus sclerotized, with MF = 1+1, 6+ 6, 4+0, 4+8, 1+1 (Fig. 4D). MI three times longer than maxillary carriers, 3.5 times longer than closing system, forceps-like, falcal arch slightly extended with inner base slightly rounded. MII wide, with triangular teeth directed laterally (Figs. 4D and 4E); three times longer than cavity opening. MIII short, slightly curved, blunt triangular teeth, attachment lamella irregular, situated only in center of anterior edge of maxilla, slightly sclerotized (Fig. 4E). Left MIV with distal tooth longest, attachment lamella semicircle, wide, better developed in central portion, situated 2/3 along anterior edge of maxilla, strongly sclerotized. Right MIV with distal teeth larger; attachment lamella semicircle, wide, better developed in central portion, situated 2/3 along anterior edge of maxilla, slightly sclerotized. MV rectangular, longer than wide, with rounded tooth (Fig. 4E). Mandibles brown with transparent cutting plates.

Palmate branchiae with six short filaments, from chaetigers 18 to posterior end (Figs. 4G–4I). First seven chaetigers with one branchial filament, two in chaetigers 26–28, four in chaetiger 29–59, five in chaetigers 60–90 and a maximum of six filaments from chaetiger 91 to posterior end. Branchial filaments slightly longer than dorsal cirri in anterior chaetigers and double in length in posterior chaetigers.

First three parapodia smallest, best developed in chaetigers 7–31, gradually becoming smaller (Fig. 4A). Dorsal cirri conical in most chaetigers, 1.6 times longer than ventral cirri in anterior, best developed in chaetigers 1–25 (Fig. 4F). Ventral cirri digitiform in first two parapodia (Fig. 4F); with short swollen base and rounded tip from chaetiger 3 to midbody (Fig. 4B); becoming triangular with pointed tip in following chaetigers (Figs. 4G–4I). Prechaetal lobe as a transverse fold in all chaetigers (Figs. 4G–4I). Chaetal lobe conical in anterior chaetigers (Fig. 4F); triangular in middle to posterior chaetigers, with aciculae barely emerging from midline (Figs. 4G–4I). Postchaetal lobe well developed and longer than chaetal lobe in first 42 chaetigers; digitiform in chaetigers 4–32; ear-shaped in chaetiger 33 to 42, progressively smaller in chaetiger 43 onwards (Figs. 4G–4I).

Aciculae with black shafts and amber blunt tip from anterior to middle chaetigers (Figs. 4F–4H), becoming golden in posterior (Fig. 4I), up to two aciculae in anterior to middle chaetigers, reducing to one in posterior chaetigers (Figs. 4F–4I). Limbate chaetae only supracicular. Four types of pectinate chaetae: (1) 5–6 isodont symmetrical in anterior parapodia, with narrow blades, thin shaft and 11–13 short, slender teeth (Fig. 4J), in anterior region; (2) 5–6 isodont asymmetrical with wide blades, thick shaft, 20–21 short and slender teeth (Fig. 4K), from anterior to middle region; (3) 4–5 anodont, asymmetrical with wide blades, thick shaft 13–14 medium-coarse short teeth (Fig. 4L) in middle to posterior chaetigers; (4) 1–2 anodont with asymmetrical, wide blades, thick shafts, 5–7 long and thick teeth and wide blades (Fig. 4M), in posterior parapodia. Compound spinigers with blades of two lengths in all chaetigers, longer blades more abundant (Fig. 4N). Compound falcigers absent. Subacicular hooks blunt or weakly bidentate; yellow or brown/golden (Figs. 4O and 4P), starting from chaetiger 25, two per parapodium in anterior chaetigers, one in posterior region, present in all parapodia.

Variation. Complete specimens with 201 chaetigers, L10 = 3–5 mm, W10 = 3–4 mm, TL = 23–65 mm. Palps reaching from 2^nd peristomial ring to 3^rd chaetiger, lateral antenna reaching from 2–4 chaetiger, median antenna up to 3^rd–4^th chaetiger. MF varies: MII: 4–5 + 5–6, MIII: 6–7, MIV: 3–4 + 6–8. Start of branchiae in chaetigers 18 to 26. Maximum number of branchial filaments in chaetigers 73–97. Subacicular hooks first occur in chaetigers 23–36. Postchaetal lobe well developed in chaetigers 1–43.

Habitat. Found in crevices of muddy rocks (porous rocks made up of fine-grained particles) on the banks of the Mzingazi canal.

Distribution. Mzingazi Canal, leading to Richards Bay harbour, KwaZulu-Natal, South Africa.

DNA barcode. Richards Bay, KwaZulu-Natal, South Africa. Holotype: MB-A095294, GenBank accession number OQ836470. A total of 575 bp fragment isolated with the universal mitochondrial cytochrome oxidase subunit 1 gene, primer pair LCO1490, HCO2198 (Folmer et al., 1994).

Etymology. The specific epithet mzingazia refers to the type locality i.e., the Mzingazi canal.

Remarks. Marphysa capensis (Schmarda, 1861), M. durbanensis Day, 1934, M. haemasona Quatrefages, 1866, Marphysa sherlockae Kara, Molina-Acevedo, Zanol, Simon & Idris, 2020, and M. mzingazia sp. nov. occur in South Africa and have branchiae throughout the body. Marphysa capensis only has compound falcigers in all parapodia, while all others have compound spinigers in addition to the falcigers. Marphysa durbanensis and M. haemasona have long branchial stems, while these are short in M. mzingazia sp. nov. Moreover, M. haemasona has colourless eyes (red in M. mzingazia sp. nov.) and ovoid postchaetal lobes in the first four chaetigers (digitiform in M. mzingazia sp. nov.). Marphysa durbanensis and M. sherlockae have reddish subacicular hooks, while these are amber in M. mzingazia sp. nov. (Day, 1967; Kara et al., 2020b).

Marphysa mzingazia sp. nov. resembles M. aransensis Treadwell, 1939 (Texas), M. brevibranchiata Treadwell, 1921 (Bahamas), M. fauchaldi Glasby & Hutchings, 2010 (Australia), M. gravelyi Southern, 1921 (India), M. hongkongensa Wang, Zhang & Qiu, 2018 (China), M. gaditana Martin, Gil and Zanol in Martin et al. (2020) (Spain), and M. kristiani Zanol, da Silva & Hutchings, 2016 (Australia) in having only compound spinigers in all chaetigers, and amber subacicular hooks. However, M. mzingazia sp. nov. has four types of pectinate chaetae: isodont narrow pectinate with long and slender teeth, isodont wide pectinate with short and slender teeth, anodont wide pectinate with short and slender teeth, anodont wide pectinate with long and thick teeth while M. aransensis (isodont narrow pectinate with long and slender teeth, isodont wide pectinate with short and thick teeth, anodont wide pectinate with long and thick teeth), M. fauchaldi (isodont narrow pectinate with long and slender teeth, isodont wide pectinate with short and slender teeth, anodont wide pectinate with long and slender teeth), M. gravelyi (isodont narrow pectinate with short and slender teeth, isodont wide with long and slender teeth, anodont wide pectinate with long and slender teeth), M. kristiani (isodont narrow pectinate with long and slender teeth, isodont wide pectinate with long and slender teeth, anodont wide pectinate with long and thick teeth), and M. gaditana (isodont narrow pectinate with long and slender teeth, isodont wide pectinate with long and thick teeth, anodont wide pectinate with long and thick teeth) have only three types of pectinate chaetae, and M. hongkongensa has five types of pectinate chaetae (isodont narrow pectinate with long and slender teeth, isodont wide pectinate with short and slender teeth, anodont wide pectinate with long and thick teeth, anodont wide pectinate with long and slender teeth). Furthermore, M. mzingazia sp. nov. has an auricular postchaetal lobe from chaetiger 4, whilst in M. brevibranchiata the postchaetal lobe is rounded in the same chaetiger. Finally, M. mzingazia sp. nov. has conical chaetal lobes in first chaetigers, while in M. brevibranchiata the chaetal lobe is rounded in first chaetigers.

Treadwellphysa Molina-Acevedo & Carrera-Parra, 2017

Diagnosis. According to Molina-Acevedo (2019): Prostomium bilobed; eyes present; with five prostomial appendages arranged in a semicircle; peristomial cirri absent; branchiae present along the body, long and digitiform branchial filaments. Maxillary apparatus with four pairs (I, II, IV, V) of maxillae and an unpaired (III). Maxillae I forceps-like, attachment lamellae absent; angular shaped falcal arch; base of maxilla with straight outer edge and basal inner with a curvature where the base of MII is supported. Maxillae II, inner base with a small, rounded projection that fits in the curvature of the basal inner edge of maxillae I; similar size in left and right of cavity opening, upper end reaching same height as basal tooth, without attachment lamella. Maxilla III curved; attachment lamella at the centre of posterior edge of maxilla. Maxillae IV; wide attachment lamellae, situated on posterior edge of maxillae. Maxillae V unidentate, attachment lamellae absent. Dorsal cirri on parapodia without articulation; gradually decreasing in size in middle toward posterior parapodia; ventral cirri with swollen base as a transverse welt with short digitiform tip, in more than half of parapodia of the body; poorly developed postchaetal lobe. Supracicular chaetae with limbate chaetae; and three shapes of pectinate chaetae, isodont narrow in anterior region, isodont wide in median-posterior region; and anodont wide in posterior region. Subacicular chaetae with compound falcigers always present, bidentate, or tridentate; spinigers, and spinifalcigers (long blade similar to that of a spiniger with bidentate teeth at the proximal end similar to a falciger, but lacks the general “hood” characteristic of falcigers, see Molina-Acevedo & Carrera-Parra (2017)) present occasionally; subacicular hooks bidentate present in most parapodia.

Treadwellphysa izinqa sp. nov.

lsid:zoobank.org:act:256FCA20-DEEA-463F-BABB-BD7A23D33695

(Figs. 5–6)

Marphysa corallina—Day 1954:19, Day, 1967: 400, fig. 17.7f –j (Non Kinberg, 1865).

Marphysa cf. corallina—Simon, Kara, du Toit, van Rensburg, Naidoo, Matthee 2021:30–31, fig. 15.

Material examined. Holotype. One incomplete specimen (MB-A095291) in 96% ethanol, Umhlanga Rocks, KwaZulu-Natal, South Africa, 29°43′39.2′′S 31°05′20.0′′E, coll. J. Kara, 19 September 2019. Paratypes 1–4. Four incomplete specimens (MB-A095512, MB-A095511, MB-A095290, MB-A095287) in 96% ethanol, Umhlanga Rocks, KwaZulu-Natal, South Africa, 29°43′39.2′′S 31°05′20.0′′E, coll. J. Kara, 19 September 2019. Non-type material. Three specimens, two incomplete, one complete (SAMC-A20577), Umhlali Shore station, KwaZulu-Natal, South Africa, det. J. H. Day. Nine specimens (MB-A095280–MB-A095289) in 96% ethanol, Umhlanga Rocks, KwaZulu-Natal, South Africa, 29°43′39.2″S 31°05′20.0″E, coll. J. Kara, 19 September 2019. Fourteen specimens (MB-A095266–MB-A095279) in 96% ethanol, Port Shepstone, KwaZulu-Natal, South Africa, 30°44′27.4″S 30°27′34.5″E, coll. J. Kara, 30 September 2019. Five specimens (MB-A095537–MB-A095541) in 96% ethanol, Mabibi, KwaZulu-Natal, South Africa, 27°24′58.3″S 32°42′43.8″E, coll. J. Kara, 29 April 2014. Six specimens (MB-A095517–MB-A095522) in 96% ethanol, Adlams, KwaZulu-Natal, South Africa, 27°37′28.3″S 32°39′22.5″E, coll. J. Kara, 30 March 2014. Four specimens (MB-A095513–MB-A095516) in 96% ethanol, Ballito, KwaZulu-Natal, South Africa, 29°32′23.2″S 31°13′25.9″E, coll. J. Kara, 31 January 2014. Six specimens (MB-A095527–MB-A0995532) in 96 ethanol, Reunion Rocks, KwaZulu-Natal, South Africa, 29°59′11.5″S 30°57′51.0″E, coll. J.Kara, 13 June 2013. Four specimens (MB-A095533–MB-A095536) in 96% ethanol, Green Point, KwaZulu-Natal, South Africa, 30°15′00.6″S 30°46′55.9″E, coll. J. Kara, 23 June 2013. Four specimens (MB-A095523–MB-A095526), in 96% ethanol, Umgazana, KwaZulu-Natal, South Africa, 31°42′19.3″S 29°24′49.2″E, coll. J. Kara, 10 July 2013. Five specimens (MB-A090276–MB-A090280), in 96% ethanol, Witsand, Western Cape, South Africa, 34°23′31.9″S 20°51′50.1″E, coll. A. du Toit, 30 April 2017.

Description. Holotype incomplete (posterior end used for molecular analyses) with up to 151 chaetigers, L10 = 9 mm, W10 = 7 mm, TL = 80 mm. Transversal body section rounded anteriorly, dorsoventrally flattened from chaetiger 18 to posterior end (Figs. 5A–5C); widest at chaetiger 35–40 (0.35 mm). Body light brown anteriorly (Figs. 5A and 5D), cream from middle to posterior end (Figs. 5B and 5C), iridescent throughout. Palps, lateral and median antennae olive green/dark brown with white conical tips (Figs. 5A, 5D and 5E).

Prostomium bilobed (0.1 mm long, 0.3 mm wide), lobes frontally rounded, ventral sulcus deep (Figs. 5A, 5D and 5E). Prostomial appendages in semicircle (Fig. 5D), median antenna slightly isolated by a gap. Palps reaching second peristomial ring, lateral and median antennae reaching chaetigers 1 and 2, respectively. Palpophores and ceratophores thick, short, ring shaped; palpostyles and ceratostyles thick, cylindrical with conical ends. Two black ring-shaped eyes at the base of lateral antennae (Fig. 5A, red arrow).

Peristomium (0.1 mm long, 0.25 mm wide) with first ring twice as long as second, clearly separated on all sides (Figs. 5A, 5D and 5E).

Maxillary apparatus sclerotized, MF = 1+1, 3+3, 4+0, 3+5, 1+1 (Fig. 3F). MI 2.4 times longer than maxillary carriers, three times longer than closing system, MI forceps-like, slightly extending but rounded, with curved basal inner edge (Fig. 5F). MII wide, with triangular teeth directed laterally, three times longer than cavity opening, and a small elevation at base, fitting inner edge of maxillae I (Fig. 5F). MIII short, with blunt triangular teeth and irregular attachment lamella at centre of posterior edge in relation to maxilla (Fig. 5F). Right MIV with distal tooth longest, and strongly sclerotized rectangular attachment lamella at 2/3 along posterior edge of maxilla. Right MIV with three teeth, distal tooth longest, and sclerotized circular attachment lamella along posterior edge of maxilla. MV rectangular, square, with single tooth (Fig. 5F). Mandibles brown with transparent cutting plates and six growth rings.

Branchiae pectinate, with up to three long filaments, starting from chaetiger 26 to posterior end (Fig. 6C); with a single filament at chaetigers 26 to 37, three long filaments from chaetigers 38–97, two filaments from chaetigers 98–120, and one filament from chaetigers 121 to posterior end (Figs. 5B, 5C, 6C and 6D). Branchial filaments nine times longer than dorsal cirri in median body region (Figs. 6C and 6D).

First three parapodia smallest (Figs. 6A, 6D and 6E). Dorsal cirri digitiform in anterior chaetigers, two times longer than postchaetal lobes (Fig. 6A); conical in median-posterior chaetigers, 1/2 length of chaetal lobe (Fig. 6C) and 1/3 longer than chaetal lobe in posterior chaetigers (Fig. 6D). Ventral cirri digitiform in first three parapodia, 2.3 times longer than postchaetal lobes (Fig. 6A); with oval swollen base and rounded tip from chaetiger 4–8; with transverse welt with a rounded tip from chaetiger 9–97; reducing to small swollen base with round tip from chaetiger 98 to posterior (Figs. 6B–6D). Prechaetal lobe as a transverse fold in all chaetigers (Figs. 6A–6D). Chaetal lobe rounded in anterior chaetigers (Figs. 6A and 6B); triangular in median to posterior chaetigers, with aciculae emerging from midline (Figs. 6C–6E). Postchaetal lobe developed in first 38 chaetigers and longer than chaetal lobe; digitiform in first two chaetigers; ear-shaped from chaetigers 30–37 progressively smaller and inconspicuous from chaetiger 38 to posterior end (Figs. 6B–6E).

Aciculae with black shafts and amber blunt tip (Figs. 6E and 6I), two aciculae from anterior to median chaetigers, one in posterior chaetigers (Figs. 6A–6E and 6I). Limbate capillaries of two lengths in supracicular position in all chaetigers (Fig. 6F). Four types of pectinate chaetae; in anterior chaetigers, 4–6 isodont symmetrical pectinate chaetae, with wide blade, thin shaft, up to 26–28 short and slender teeth (Fig. 6G); in median to posterior chaetigers, 1–2 isodont asymmetrical pectinate chaetae, with wide blade, thick shaft and up to 21 long and slender teeth (Fig. 6H), 1–4 anodont pectinate chaetae, with wide blade, thick shaft and up to 8–10 short and thick teeth (Fig. 6I), 1–2 anodont pectinate chaetae, with wide blade, thick shaft and up to 8–10 long and thick teeth (Fig. 6J). Compound spinigers absent. Compound falcigers tridentate with a triangular proximal tooth larger than rounded distal teeth in anterior parapodia; in median to posterior chaetigers, with blades of similar length, shorter than anterior falcigers, with rounded distal teeth shorter than triangular proximal tooth (Figs. 6K and 6L). Subacicular hook bidentate with rounded guard, reddish basally and golden at distal end; teeth triangular with proximal tooth larger than distal tooth (Fig. 6E); starting from chaetiger 28–30, usually one per parapodium, present in all chaetigers.

Pygidium with two pairs of pygidial cirri emerging ventrally, dorsal pair as long as last five chaetigers; ventral pair 1/3 as long as dorsal pair (Fig. 5C).

Variation. Paratypes incomplete, with up to 145–176 chaetigers, L10 = 7–8 mm, W10 = 5–6 mm and TL = 75–88 mm. Palps reaching between first and second peristomial rings. Lateral and median antenna reaching between chaetiger 2 and 3. Non-type material: L10 = 0.6–1.5 mm, W10 = 0.2–0.55 mm; palps reaching between first peristomial ring and chaetiger 2, lateral antenna reaching between the first peristomial ring and chaetiger 3, median antenna reaching between first peristomial ring and chaetiger 5. Branchiae starting from chaetiger 22–42, maximum number of branchial filaments from chaetiger 49–55. Subacicular hooks starting from the chaetiger 25 to 30. Postchaetal lobe well-developed from chaetiger 1–38. Maxilla formula: MII 2+3, MIV 3+5.

Habitat. Found in mucous-sand burrows in sediment under coralline algal beds, worm rock (dense aggregation of calcium carbonate-sand tubes created by sabellarid and/or serpulid worms, forming a rock-like structure), and in crevices on fringing intertidal rocky shores.

Distribution. Northern KwaZulu-Natal (Mabibi) to Eastern Cape (Umgazana), Witsand in the Western Cape (Simon et al., 2021b).

DNA barcode. Umhlanga Rocks, KwaZulu-Nata, South Africa. Holotype MB-A095291, GenBank accession number OQ836467. A total of 575 bp fragment isolated with the universal mitochondrial cytochrome oxidase subunit 1 gene, primer pair LCO1490, HCO2198 (Folmer et al., 1994).

Etymology. The isiZulu (the native language of the KwaZulu-Natal people) word “izinqa” translates to buttocks and refers to the round prostomial lobes that are separated by a deep ventral sulcus, giving a distinctive butt-like appearance that can be seen with the naked eye.

Common name. Brown wonderworm. Live T. izinqa sp. nov. can be distinguished from M. haemasona, the blood wonderworm commonly used as bait in the Western Cape, in having a solid brown body colour and white tipped antennae and palps (see fig. 15A in Simon et al., 2021b), whereas M. haemasona has a reddish/deep violet, speckled anterior dorsum, and antennae tips with brown and white bands (Simon et al., 2022).

Remarks. Marphysa cf. corallina from Witsand (Simon et al., 2021b) matches the description of T. izinqa sp. nov., particularly in having a small elevation at the inner base of maxilla II fitting in the inner curved base of MI but with a few minor differences that are probably site related. Specimens from Witsand are 40 mm longer than the specimens examined here; have two to four more branchial filaments and branchiae that start between 9–13 chaetigers later. However, the low intraspecific distances (<1%) of specimens collected from Witsand and KwaZulu-Natal confirms that they belong to the same species. Moreover, morphology of the maxillary apparatus, also considered a stable character (Molina-Acevedo & Carrera-Parra, 2017), conform to that of T. izinqa sp. nov. with having the small elevation at the inner base of MII fitting in the inner, curved base of MI (fig. 15F, Simon et al., 2021b). Thus, specimens from Witsand are considered here as Treadwellphysa izinqa sp. nov.

Treadwellphysa izinqa sp. nov. resembles T. rizzoae Molina-Acevedo, 2019, T. villalobosi Molina-Acevedo, 2019, T. languida (Treadwell, 1921), and T. veracruzensis (De León-González & Castañeda, 2006) in having only compound falcigers throughout the body. However, T. villalobosi, T. languida and T. veracruzensis have translucent subacicular hooks, and compound falcigers with blades of various lengths in anterior region, whereas in T. izinqa sp. nov. the subacicular hook is reddish basally and distally translucent, and falcigers are present with consistent length in anterior chaetigers. Treadwellphysa rizzoae has falcigers in anterior chaetigers only with similar lengths, and a poorly developed postchaetal lobe which is rounded in most chaetigers when present, while T. izinqa. sp. nov. has tridentate falcigers, well-developed postchaetal lobes that are digitiform in first chaetigers and auricular in following ones.

Identification key for the Marphysa species from South Africa

• 1 With only compound falcigers……………………M. capensis (Schmarda, 1861)

• - With compound falcigers and spinigers in anterior-median region. M. sherlockae Kara, Molina-Acevedo, Zanol, Simon & Idris, 2020

• - With only compound spinigers……………………………………………………2

• 2(1) Palmate branchiae, with short filaments, exceeding the length of the dorsal cirri………………………………M. mzingazia sp. nov.

• - Pectinate branchiae, with long filaments, at least four times longer than dorsal cirri in median region of the body…………………………………………………3

• 3(2) Postchaetal lobe digitiform in first three chaetigers, MII 5–6+6–8, and five types of pectinate chaetae: narrow isodont pectinate with long and slender teeth, wide isodont pectinate with short and slender teeth, wide isodont pectinate with short and thick teeth, wide anodont pectinate with short and slender teeth, and wide anodont with long and thick teeth……………………………M. durbanensis Day, 1934

• - Postchaetal lobe tongue-shaped (ovoid) in first three chaetigers, MII 4+4, and four types of pectinate chaetae: narrow isodont pectinate with long and slender teeth, wide isodont pectinate with short and slender teeth, wide anodont pectinate with short and slender teeth, and wide anodont with long and thick teeth…………………M. haemasona Quatrefages, 1866.