Daylithos iris ( Michaelsen, 1892 ) Salazar-Vallejo, 2012

Salazar-Vallejo, Sergio I., 2012, 3562, Zootaxa 3562, pp. 1-62 : 54-56

Daylithos iris ( Michaelsen, 1892) n. comb.

Figure 22

Stylarioides iris Michaelsen 1892:18–19 , Fig. 6.

Stylarioides parmatus: Willey 1905:289–290 , Pl. 8, Fig. 5; Fauvel 1932:179–180; Fauvel 1953:346–347, Fig. 179b; Menon et al. 1965:263–264, Fig. 1a–h (non Grube, 1877).

Pherusa parmata: Day 1973b:354 (non Grube, 1877).

Type material. Indian Ocean, Arabian Sea. Neotype (USNM-1191188), vicinity of Karachi (24º51' N, 67º02' E), Pakistan, Mohammed Abdullah el-Husseini, coll. (no further data).

Additional material: Northern Indian Ocean, Bay of Bengal. One specimen (USNM-1191189), Rangoon (Yangon, 16º48' N, 96º09' E), Burma, G.E. Gates, coll. (mature female, contracted, 28 mm long, 4 mm wide, cephalic cage 7 mm long; ova 120 µm, 75 chaetigers; dorsal shield without posterior projection). Western Indian Ocean , Yemen. Five specimens ( SMF-15402 ), four complete, an anterior fragment, southern coast of Socotra Island, no further data, A. Moghrabi, coll. (complete 12–32 mm long, 1–3 mm wide, cephalic cage 3.5–8.0 mm long, 68–74 chaetigers; falcate neurohooks from chaetiger 7–9; fragment 2.0 mm wide, cephalic cage 7.5 mm long, falcate neurohooks from chaetiger 8). One specimen ( SMF-15407 ), mature female, Cruise Code N-48, Stat. NH 8 ,

site 31 (12°39.037’N, 54°31.576’E),, 5 Feb. 1999 (23 mm long, 2 mm wide, cephalic cage 4 mm long, 77 chaetigers; falcate neurohooks from chaetiger 8). Tanzania. One specimen (USNM-1132083), Anton Bruun cruise 9, Stat. KA-12 (06°54' S, 39°56' E), limestone and coral, 1–5 m, shore, Latham Island (SE Dar Es Salam), S. A. Earle, coll. (20 mm long, 2.5 mm wide, cephalic cage 6 mm long, 74 chaetigers; first falcate neurohooks in chaetiger 7; hooks per chaetiger: 10, 30, 50, 60: 2, 3, 1, 7) . Madagascar. One mature female ( MNHN-A183 ), damaged, with ovaries mostly exposed, Sarodranco, Tulear (Toliara, 23º21' S, 43º40' E), Mission F. Geay, no further data (36 mm long, 3.5 mm wide, cephalic cage broken, 5 mm long, 101 chaetigers; anterior neurochaetae mostly broken; oocytes about 120 µm) . Mozambique Channel. One specimen ( LACM-AHF-4869 ), complete, International Indian Ocean Expedition, RV Anton Bruun, Mozambique channel, about 100 km NE off Durban, Stat. AB 357B (29º11' S, 32º02' E), 69.5 m, rock dredge on rocky bottom, 30 Jul. 1964 (21 mm long, 2.5 mm wide, cephalic cage 8 mm long, 62 chaetigers; first falcate neurohooks in chaetiger 8). One specimen ( LACM-AHF- 4870 ), complete, International Indian Ocean Expedition, RV Anton Bruun, Moçambique, Inhaca Island (26º01' S, 32º57' E), Stat. pre AB372P, shore by diving for corals, 22 Aug. 1964 (29.5 mm long, 3 mm wide, cephalic cage 8 mm long, 80 chaetigers; dissected for anterior end) .

Description. Neotype (USNM-1191188) complete, partially dehydrated, grayish. Body cylindrical, tapering posteriorly into a flat cauda ( Fig. 22A); 65 mm long, 5 mm wide, cephalic cage 8 mm long, 80 chaetigers. Tunic thin, without sediment particles; body papillae minute, rounded, arranged in two rows per segment, anterior row with more papillae.

Cephalic hood not exposed in neotype (anterior end details observed by dissection of LACM-AHF-4870), cephalic hood short, margin finely papillated. Prostomium flat, without eyes; caruncle whitish, median ridge maculated, projected posteriorly, not reaching the branchial plate margin. Palps pale, palp keels reduced (distorted by contraction). Lateral and dorsal lips fused, projected; ventral lip reduced ( Fig. 22C).

Branchiae cirriform, separated in two lateral groups; each group with filaments arranged in 6 rows, about 45 filaments per group. Largest branchiae in inner rows, twice as wide as thinner filaments, about as long as palps, decreasing in size towards the margins. Nephridial lobes in branchial plate not seen.

Cephalic cage chaetae as long as 1/8 body length, or less than twice body width. Chaetigers 1–2 involved in the cephalic cage; chaetae in chaetiger 3 longer than following ones, not contributing to the cephalic cage; chaetae arranged in short ventrolateral rows, 14 noto- and 12 neurochaetae in chaetiger 1, 9 noto- and 10 neurochaetae in chaetiger 2. Anterior dorsal margin of chaetiger 1 with small papillae.

Anterior chaetigers without especially long papillae. Chaetigers 1–3 progressively longer. Sand cemented anterior shield dorsal, extending to chaetiger 5, rounded anteriorly, posteriorly projected as a low step ( Fig. 22B). Chaetal transition from cephalic cage to body chaetae abrupt; falcate neurohooks from chaetiger 10. Gonopodial lobes not visible because of body-wall folds due to dehydration.

Parapodia poorly-developed, chaetae emerge from the body wall. Parapodia lateral; median neuropodia ventrolateral. Noto- and neuropodia well separated. Median notochaetae in short longitudinal rows; all notochaetae very thin, multiarticulate capillaries, as long as ¼–1/5 body width, 3 per fascicle, articles short basal- and distally, longer medially. Neurochaetae multiarticulate, thin golden capillaries in chaetigers 1–5; chaetigers 7–9 with thicker, darker aristate capillaries ( Fig. 22E). Falcate neurohooks from chaetiger 10, arranged in short transverse rows, 2 in anterior chaetigers ( Fig. 22F), then 3 larger ones in median chaetigers, far posterior chaetigers with 5 ( Fig. 22G) to 8 ( Fig. 22H), curved, smaller neurohooks, arranged in almost longitudinal rows. Larger hooks with long articles, distally widened, tips eroded.

Posterior end depressed, slightly widened subdistally ( Fig. 22D), tapering to blunt cone; pygidium with terminal anus, without anal cirri.

Remarks. The taxonomic status of Daylithos iris ( Michaelsen, 1892) n. comb. originally described from Sri Lanka needs clarification because it has been regarded as very similar to D. parmatus described from the Philippine islands. The proposal of a neotype together with the above description and illustrations will clarify the current situation (ICZN 1999, Art. 75.3.1–75.3.3). Johan Wilhelm Michaelsen was the chief curator of the Hamburg Zoological Museum (Anon. 1937). His research interests concentrated on oligochaetes but he made some contributions on ascididans and polychaetes and he deposited his material in this museum; unfortunately during WWII bombing over Hamburg, many type specimens were lost and this included the type of D. iris , as confirmed by the current museum staff (ICZN 1999, Art. 75.3.4). This species was described with many neurohooks in posterior chaetigers and thus it belongs in Daylithos and the only original illustration shows a neurohook subdistally expanded, which is also present in the neotype (ICZN 1999, Art. 75.3.5). The neotype is not coming from the same locality (ICZN 1999, Art. 75.3.6), but no additional specimens were available from Sri Lanka or Southern India.

On the other hand, D. iris resembles D. parmatus because both species have 5–7 neurohooks in far posterior chaetigers. These two species differ as indicated above mainly because of their neurohooks in median chaetigers; in D. iris they are subdistally expanded without any flange, whereas in D. parmatus they are flanged and tapered.

Further, previous records and illustrations have indicated that these two species differ because in D. iris the dorsal shield is entire, whereas it is longitudinally cleft in D. parmatus . An additional difference lies in the relative thickness of branchial filaments, because in D. iris the larger branchiae are twice as wide as thinner ones, whereas in D. parmatus they are four times as wide as the thinner ones. Another species which is somewhat related to S. iris is S. cinctus because both have subdistally swollen neurohooks; however, in D. iris neurohooks are slightly falcate, whereas they are markedly falcate in D. cinctus .

After the original description, Willey (1905, Fig. 5) made a whole-body illustration, but the most detailed account was by Menon et al. (1966). However, they apparently confused the start of neurohooks and reverted the back and venter of the animal when the relative size of papillae was characterized.

Neotype locality. Karachi , Pakistan.

Distribution. The original type locality was Sri Lanka. It ranges from Pakistan to the Southern tip of India and Madagascar.