Diopatra madeirensis Langerhans, 1880

Paxton, Hannelore & Arias, Andres, 2017, Unveiling a surprising diversity of the genus Diopatra Audouin & Milne Edwards, 1833 (Annelida: Onuphidae) in the Macaronesian region (eastern North Atlantic) with the description of four new species, Zootaxa 4300 (4), pp. 505-535 : 514-521

Diopatra madeirensis Langerhans, 1880 (redescription)

Figures 7 A–D, 8, 9; Table 1

Diopatra madeirensis Langerhans, 1880: 290 , pl. 15, fig 25a, b.

Material examined. Type material. Syntype: (NHMW 2296 slide preparation), Madeira, depth about 36 m, coll. P. Langerhans.

Non-type material. AM W.49213 (1 specimen), Ponta da Calheta beach, Porto Santo Island, Madeira Islands, 33°01’33”N – 16°22’18”W, intertidal, coll. A. Arias, Jul 2010 ; AM W.49214 (1 wet specimen plus parts thereof on SEM stub), La Laja beach, Gran Canaria, Canary Islands, 28°03’N – 15°25’W, intertidal, coll. A. Arias, 12 Jul 2012 ; MNCN 16.01 /17816–16.01/17817 (1 wet specimen plus 1 specimen on SEM stub) La Laja beach, Gran Canaria, Canary Islands, 28°03’N – 15°25’W, intertidal, coll. A. Arias, 12 Jul 2012 .

Type locality. Eastern North Atlantic , Madeira, depth about 36 m.

Diagnosis. Prostomium anteriorly rounded with two subulate frontal lips; antennae to chaetiger 7–10 with nine to ten ceratophoral rings, lateral projections absent; nuchal grooves crescentic to semicircular; peristomial cirri present. Anterior four to five pairs of parapodia with bidentate pseudocompound hooks with pointed hoods; single postchaetal lobes. Ventral parapodial lobes absent; ventral cirri on four to five chaetigers. Subacicular hooks from chaetiger 15–17; pectinate chaetae with 25–30 teeth; spiralled branchiae, first on chaetiger 4–5, last single filament on chaetiger 38.

Description. Specimen from Porto Santo (AM W.49213) almost complete, measuring 38 mm in length for 82 chaetigers, 1.7 mm in width; specimens from Gran Canaria (AM W.49214 / MNCN 16.01/17816) 11 and 9 mm for 17 and 25 chaetigers, width 2.5 and 0.7 mm. Ethanol stored specimens overall cream-coloured to very pale brown with more brown pigmentation at anterior part of prostomium, ceratophores, proximal and part of ceratostyles (figs 7A–C); some specimens with lateral segmental spots near bases of parapodia, when best developed, appearing as vertical stripe next to parapodia ( Fig. 7 A).

Prostomium anteriorly rounded with two subulate frontal lips separated by a small gap. Ventral upper lips oval with papilla-like median section between lips; lower lip with median section ( Fig. 8 A). Ceratophores of palps and antennae with eight to nine proximal rings and a longer distal ring ( Fig. 8 B), styles tapering to distal end, with fine tips. Palps reaching to chaetiger 2–4, lateral antennae to chaetiger 7–10, median antenna to chaetiger 7–9. Ceratostyles with about 20 irregular longitudinal rows of sensory buds ( Fig. 8 C); buds slightly raised, circular ( Fig. 8 D). Nuchal grooves crescentic to semicircular ( Fig. 8 E), peristomial cirri very slender and long, 1.5–twice as long as peristomium, reaching almost to distal end of ceratophores, inserted distally on peristomium, lateral to lateral antennae.

First four to five pairs of parapodia modified, slightly prolonged and directed anteroventrally. Prechaetal lobe rounded, postchaetal lobe subulate ( Fig. 9 A). Prechaetal lobe becoming reduced, absent from about chaetiger 10; postchaetal lobe becoming smaller but remaining as little knob into posterior region. Dorsal cirri subulate, very long, attaining greatest length in branchial region, reaching almost up to mid-dorsum, thereafter gradually shortening, becoming very slender posteriorly; ventral cirri subulate on anterior four to five chaetigers, thereafter replaced by ventral glandular pads ( Fig. 8 A). Spiralled branchiae from chaetiger 4, best developed on chaetigers 6– 10 with about 10 whorls reaching to ceratophores when anteriorly extended. Individual filaments long and slender, about three to four times as long as branchial stem wide ( Fig. 9 B), number of filaments decreasing gradually after chaetiger 10; single filaments from chaetiger 38, absent shortly thereafter.

Modified parapodia (chaetigers 1 to 4–5) with one to two slender upper simple limbate chaetae and pseudocompound bidentate hooks with pointed hoods and almost smooth shafts. Each parapodium with median robust ( Fig. 9 C), two to three upper slenderer ( Fig. 9 D) and two to three lower very slender hooks ( Fig. 9 E).

Unmodified parapodia (chaetigers 5–6 onwards) with pectinate and limbate chaetae ( Fig. 8 F). Pectinate chaetae slightly oblique; initially only one to two chaetae with 15–20 teeth each ( Fig. 8 G), increasing to five to six chaetae with 25–30 teeth by chaetiger 30–40. Limbate chaetae becoming coarsely serrated by chaetiger 30–40; lower limbate chaetae replaced by bidentate subacicular hooks from chaetiger 15–17.

Mandibles ( Fig. 9 F) short in relation to maxillae ( Fig. 9 G); maxillary formula: MxI = 1+1; MxII = 9+10; MxIII = 8+0; MxIV = 8+10; MxV = 1+1.

Tube typical for genus, consisting of thin inner secreted layer with pieces of shell fragments and vegetation attached at angle ( Fig. 7 D).

Remarks. Diopatra madeirensis was described on the basis of one incomplete specimen measuring 1 cm in length for 35 segments and six juveniles consisting of 31–35 chaetigers of which at least some were complete specimens, collected one year later. The larger specimen was described as having quite long antennae (lateral antenna to chaetiger 4), peristomial cirri, branchiae from chaetiger 4, longer than the width of the body with a delicate stem and 12–15 spirally arranged delicate, long filaments. The spiraled branchiae were present only until chaetiger 13, consisted of one filament on chaetiger 14–15, and were absent from chaetiger 16. The pseudocompound hooks were illustrated as having a relatively short appendage, being bidentate with a long distal tooth and pointed hoods ( Langerhans, 1880: pl 15, fig 25), present on the first four chaetigers; subacicular hooks started from chaetiger 9. The maxillary formula was given as: MxI = 1+1; MxII = 15+12; MxIII = 17+0; MxIV = 10+12. In our experience the values for the left MxII and MxIII are atypical for the genus and can only be explained as an abnormality or an erroneous observation.

This specimen was obviously also not fully grown as demonstrated by the early origin of the subacicular hooks and the relatively short extent of the branchiae. Langerhans considered the six smaller juveniles to belong to the same species as they agreed in the form and distribution of the chaetae, except that in one specimen the pseudocompound hooks were present only on three parapodia, the first branchiae were always on chaetiger 5, developed well only on two chaetigers, absent from chaetiger 10, and peristomial cirri were absent.

We have examined photographs of the only existing type specimen (NHMW 2296). It is a slide preparation of a specimen measuring 6 mm in length, 0.5 mm in width without parapodia, consisting of at least 25 chaetigers. The first branchiae start on chaetiger 5, consist of a slender stem with long slender filaments, with the branchiae of chaetiger 6 being about half as long and the next consisting only of a few filaments. The protomandibles take up almost half the size of the mandibular shafts and the maxillae, although of the permanent type, are very weakly sclerotised. These combined features confirm that the specimen is one of the juveniles collected one year after the original specimen.

Our newly reported specimens from Porto Santo (Madeira Islands) and Gran Canaria (Canary Islands) are more mature than the originally described D. madeirensis specimens, as obvious from the better developed branchiae and later origin of subacicular hooks. Although this complicates the comparison of the two groups of specimens, their unifying characteristics are that their anterior parapodia have pseudocompound hooks with a short bidentate appendage having a long terminal tooth and pointed hoods ( Fig. 9 C–E), and branchiae with a slender branchial stem and long slender filaments ( Fig 9 B). We think it is justifiable that they represent the same species, D. madeirensis , the only Diopatra species (besides the indeterminable D. brevicirris ) described from Madeira. Diopatra madeirensis resembles D. marocensis which most likely also occurs on Madeira. However, the two species can be easily distinguished in that the dorsal colour pattern of the former consists only of lateral brown spots ( Fig. 7 A) while the latter has a complex colour pattern ( Fig. 12 A). Other morphological characteristics that differentiate D. madeirensis from D. marocensis and the other Macaronesian species have been detailed in Table 1.

Biology. One of the specimens from Gran Canaria (MNCN) was found with eggs of different sizes suspended in the coelom. Whilst the smaller ones had attached strings of nurse cells, those measuring about 200 µm in diameter had lost theirs already, indicating that they had reached full size. This relatively small egg size is indicative of broadcast spawning rather than brooding, which is the strategy of D. marocensis ( Arias et al. 2013) .

Characteristic D. budaevae D. gallardoi D. hektoeni D. D. mariae D. marocensis D. mellea D. micrura D. D. sp. nov. sp.nov. madeirensis sp. nov. sp. nov. neapolitana brevicirris , inđet.

. length (mm)/ N o. 7/38 95/119 18/75>38/82>28/86 139/214>31/>95 78/97 600/300>50/>63

chaetigers

. width (mm) at 0.7 4.5 0.9 2.5 2.5 5.7 3.5 4.5 9 3

chaetiger 10

Colour pattern brƟwn brƟwn pale brƟwn very pale very pale intriƇate pattern very pale antennae with brƟwn? prƟstƟmium, lines/banđs banđs Ɵn brƟwn with brƟwn with brƟwn with đark brƟwn miđđƟrsal lateral brƟwn Ɵn anteriƟr peristƟmum lateral brƟwn mƟttleđ mƟttleđ spiral banđs bars Ɵn spƟts anđ segments tƟ anđ anteriƟr spƟts đarker đarker anteriƟr intersegment Ɵverall brƟwn đƟrsum brƟwn; nƟ brƟwn anđ segments al lines đistinƇt weak banđs pattern

Palps reaching 2 3*5 1 2*4 3 3 4 2*4 1*3 2

chaetiger

Characteristic D. budaevae D. gallardoi D. hektoeni D. D. mariae D. marocensis D. mellea D. micrura D. D.

sp. nov. sp.nov. madeirensis sp. nov. sp. nov. neapolitana brevicirris ,

inđet.

. of modified 4 4 4*5 4*5 4 4 5*6 4 3*4? parapodia

Distribution. Eastern North Atlantic, Madeira and Porto Santo Island (Madeira Islands archipelago) and La Laja beach, Gran Canaria (Canary Islands), intertidal to 36 m.

Figures

FIGURE 7. Diopatra spp. photomicrographs. A, D. madeirensis (MNCN 16.01 / 17816), anterior end, dorsal view; B, D. madeirensis (AM W. 49213) anterior end, dorsal view; C, same, ventral view; D, tube of same; E, D. mariae sp. nov., paratype (MNCN 16.01 / 17819), anterior end, dorsal view; F, D. mariae sp. nov., holotype (MNCN 16.01 / 17818), anterior end, ventrolateral view; G, D. mariae sp. nov., paratype (MNCN 16.01 / 17819) everted maxillae, ventral view.

FIGURE 8. Diopatra madeirensis (AM W. 49214), scanning electron micrographs. A, Anterior part, ventral view; B, prostomium and peristomium, dorsal view; C, part of antenna, showing rows of sensory buds; D, magnified sensory buds; E, nuchal groove; F, parapodium of chaetiger 20, anterior view; G, magnified pectinate chaeta of previous image. Abbreviations: l = limbate chaeta, ng = nuchal groove; p = pectinate chaeta, psl = postchaetal lobe; SAHs = subacicular hooks.

FIGURE 9. Diopatra madeirensis (AM W. 49214), line drawings. A, Parapodium from chaetiger 1, anterior view; B, parapodium from chaetiger 11, anterior view (chaetae omitted, branchia shortened); C, median robust pseudompound hook; D, upper slender pseudocompound hook; E, lower very slender pseudocompound hook; F, mandibles; G, maxillae.

FIGURE 12. Diopatra marocensis, photomicrographs. A, anterior end, dorsal view; B, tube of worm removed from sediment; C, tube in situ to show protruding tube-cap; D, same.