Riseriopsis arabica ( Hartman, 1976 ) Salazar-Vallejo & Zhadan & Rizzo, 2019

Salazar-Vallejo, Sergio I., Zhadan, Anna E. & Rizzo, Alexandra E., 2019, Revision of Fauveliopsidae Hartman, 1971 (Annelida, Sedentaria), Zootaxa 4637 (1), pp. 1-67 : 57-59

Riseriopsis arabica ( Hartman, 1976) n. comb.

Figures 35 , 36

Fauveliopsis arabica Hartman, 1971: 1413 (nomen nudum).

Fauveliopsis arabica Hartman, 1976: 235–236 , Fig. 12a, b (partim).

TL: Arabian Sea, 110 m. D: Indian Ocean ; Arabian Sea to Southwestern Indian Ocean and Moçambique Channel, 110–315 m.

Type material: Indian Ocean, Arabian Sea, Iran. Three syntypes, one complete ( LACM 1330 ), and two other syntypes ( LACM 1331 ), one complete and a posterior region, Gulf of Oman, SE Chabahar, International Indian Ocean Expedition, R / V Anton Bruun, Sta. 248A (25°06’ N, 60°45’ E), 110 m, 28 Nov. 1963 (complete syntype with an oblique cut on chaetiger 1; body 21.5 mm long, 0.8 mm wide, 87 chaetigers; GP or oocytes not seen; posterior fragment 5.6 mm long, 0.8 mm wide, 29 chaetigers) .

Additional material. Northwestern Indian Ocean, Arabian Sea, Iran. 16 specimens ( LACM 7607 ), two complete, four anterior and 10 posterior fragments (some regenerating the anterior region), Gulf of Oman, SE Chabahar, International Indian Ocean Expedition, RV Anton Bruun, Stat. AB 247B (25°06’ N, 60°45’ E), 110 m, 28 Nov. 1963 (complete 7.8–16.5 mm long, 0.4–0.8 mm wide, 60–69 chaetigers; GP or oocytes not seen). Southwestern Indian Ocean . Mozambique Channel. Two specimens ( LACM 7608 ), one median fragment and a lumbrinerid anterior fragment, off ENE Maputo, Mozambique, International Indian Ocean Expedition, RV Anton Bruun, Stat. AB 370H (24°41’ S, 35°38’ E), 315 m, Menzies trawl, 18 Aug. 1964. Eastern South Africa. Three specimens (LACM 7609), E off Dolphin Coast, International Indian Ocean Expedition, RV Anton Bruun Stat. AB 390S (29°45’ S, 31°42’ E), 138 m, 8 Sep. 1964 (medium-sized specimen cross cut in several segments for observing chaetae; oth- ers 7.4–12.7 mm long, 0.4–0.7 mm wide, 49–68 chaetigers; GP or oocytes not seen).

Diagnosis. Riseriopsis with 49–87 chaetigers. Anterior parapodia with one acicular and one capillary per bundle; median chaetigers with one acicular and 1–2 capillaries per bundle, neuropodial aciculars aristate; posterior chaetiger with 1–3 aciculars and 1–3 capillaries; far posterior chaetigers with fewer chaetae. Pygidium with two large dorsal, and several smaller papillae. GP not seen.

Redescription. Complete syntype (LACM 1330) pale, long, stiff, slightly macerated, progressively widened into a bulbous posterior region ( Fig. 35A ); integument finely rugose, segments multi-annulated, especially in posterior region, whitish, transparent; aciculars pale along anterior chaetigers, progressively darker in median and posterior chaetigers; 17.5 mm long, 0.6 mm maximal width (0.25 mm wide chaetiger 1), 86 chaetigers.

Anterior region with anterior end invaginated ( Fig. 35A , left inset, 35B); body opening vertical without larger papillae close to it (1–2 conical papillae in other specimens). Chaetigers 1–4 1.5 times wider than long, posterior chaetigers longer, 1.5–2 times longer than wide, chaetigers 1–4 with one acicular and one capillary chaetae per rami, capillaries wider, following ones thinner.

Chaetigers 5–29 about twice longer than wide. Notopodia with one acicular and one capillary per side, neuropodia with one acicular and one capillary per side.

Median region from chaetiger 30 with segments 1.5 times longer than wide. Notopodia with one acicular and one capillary per side, neuropodia with one acicular and two capillaries per bundle, neuroaciculars often aristate, thinner than notoaciculars.

Posterior region from chaetiger 52, wider than most of body, tapered into a blunt cone; segments slightly wider than long, progressively wider towards posterior end ( Fig. 35C ), notopodia with one acicular and 1–2 capillaries (2–3 in LACM 1331), neuropodia with two aciculars and two capillaries per bundle (3–4 in LACM 1331). From chaetiger 68–69, notopodia with two aciculars and two capillaries, neuropodia with three aciculars and three capillaries per bundle.

Prepygidial chaetigers, from chaetiger 82, with notopodia having two aciculars and two capillaries per bundle, neuropodia with two aciculars and two capillaries per bundle.

Variation. Another long specimen (LACM 7609) was inside a tube made of a proteinaceous material with cemented sediment particles ( Fig. 36A, B ), but it is unknown if it was made by the polychaete itself. There are four chaetae per parapodia, one falcate acicular and one capillary per ramus along anterior chaetigers ( Fig. 36C ). Neu- ropodia has more chaetae in posterior chaetigers with up to three aciculars and 2–3 capillaries per side ( Fig. 36D ), and in the posterior end these neurochaetae decrease their number ( Fig. 36E ) as along the anterior region, and they are not always golden or brownish.

Remarks. Riseriopsis arabica ( Hartman, 1976) n. comb. differs from the two other species in the genus by having brownish chaetae along its posterior chaetigers and by living inside fibrous soft tubes. The other species, R. confusa and R. santosae n. sp. are free living, with hyaline chaetae along posterior chaetigers.

Type specimens of R. arabica do not have oocytes and they might be juveniles, potentially explaining the lack of genital papillae, although some other means to release gametes could be operating in Riseriopsis species.

The original description illustrates the posterior region, instead of the anterior one, and it shows a convoluted gut. The description and distribution imply the inclusion of some specimens from the Mozambique Channel (Hartman 1971:1413). However, they were probably different because Hartman stated: “Setae are of one kind, acicular, slightly falcate; occur 2–5 in a ramus in anterior parapodia, and 1 or 2 in posterior parapodia; companion capillary setae absent.” This, however, might be explained by a confusion about body ends. Hartman added in the remarks that these specimens had fewer segments (21–25 vs 50–86), and differed by the types of chaetae, but she probably confused the specimens since she contradicted what has been stated before. Further, some of the specimens that were examined are not complete, but anterior or posterior fragments, and this could explain the wide variation in chaetiger counts if they were regarded as complete specimens. Nevertheless, the variation in segments is very wide and adult, mature specimens might be even longer and have more segments.

Figures

FIGURE 12. Fauveliopsis levensteinae n. sp., non-type specimens (SIORAS AK 5624). A. Chaetiger 13, right parapodium, frontal view showing genital papilla (GP). B. Another specimen, chaetigers 10–13, right parapodia, frontal view, showing genital papilla (GP), arrow points to an interramal papillae enlarged in C. C. Interramal papilla, oblique frontal view. D. Notochaetal acicular and broken capillary, anterior chaetiger. E. Notochaetal spine and capillary, mid-body segment (inset: enlargement of hirsute capillary). F. Posterior acicular with spinulose posterior margin. G. Posterior region, oblique right lateral view (larger inset: pygidium showing abundant papillae; smaller inset: single papilla indicated by an asterisk, frontal view). Scale bars: A: 170 µm, B: 0.1 mm, C: 15 µm, D: 20 µm, E, F: 30 µm, G: 0.2 mm.

FIGURE 35. Riseriopsis arabica (Hartman, 1976), n. comb., complete syntype (LACM 1330).A. Extended specimen, anterior region above (left inset: anterior end, right inset: posterior end). B. Same, anterior region, dorsal view. C. Same, posterior region, left lateral view. Scale bars: A: 0.7 mm (insets: left: 0.3 mm, right: 0.2 mm), B: 0.1 mm, C: 70 µm.

FIGURE 36. Riseriopsis arabica (Hartman, 1976), n. comb., non-type, complete specimen (LACM 7609), temporaly stained with Methyl green. A. Specimen inside tube fragment, anterior region in oblique ventral view, posterior region twisted, oblique lateral view. B. Same, close-up of tube fragment showing fine sediment particles coating tube lumen. C. Medium-sized speci- men, chaetiger 19, cross section, after methyl green staining. D. Same, chaetiger 50, right parapodium, anterior view. E. Same, posterior end, dorsal view. Scale bars: A: 1.8 mm, B: 0.6 mm, C: 100 µm, D: 70 µm, E: 50 µm.