Pherusa mikacae, Salazar-Vallejo, 2014

Salazar-Vallejo, Sergio I., 2014, Revision of Pherusa Oken, 1807 (Polychaeta: Flabelligeridae), Zootaxa 3886 (1), pp. 1-61 : 23-25

Pherusa mikacae n. sp.

Figure 7

Stylarioides plumosa .— Fauvel, 1934:48, 1940:6 (non Müller, 1776).

Type material. Mediterranean Sea, Adriatic Sea, Croatia. Holotype ( NHMR 17740 ), and one paratype ( NHMR 17741 ), St. 107 (45°02.8' N, 13°19.0' E), 37 m, silty sand, 18 Oct. 2006, B. Mikac, coll. (paratype anterior fragment 13 mm long, 4 mm wide, cephalic cage (unbroken) 14 mm long, 23 chaetigers; many neurochaetae aristate; anterior end dissected for details). One paratype ( NHMR 17742 ), six fragments, many chaetae broken, one anterior, four medial and one posterior fragment, Sta. 5 (45°18.4' N, 13°18.0' E), 31 m, silty sand, 21 Jun. 2005, B. Mikac, coll. (anterior fragment 19 mm long, 3 mm wide, cephalic cage 7 mm long, 31 chaetigers; medial fragments 4.5–6.5 mm long, 9–18 chaetigers; posterior fragment in regeneration, darker, 8 mm long, 25 chaetigers). One paratype ( NHMR 17743 ), anterior fragment, anterior region eroded, without tunic, many chaetae broken, Sta. 5 (45°18.4' N, 13°18.0' E), 31 m, silty sand, 21 Jun. 2005, B. Mikac, coll. (anterior fragment 24 mm long, 2 mm wide, cephalic cage (broken) 5 mm long, 55 chaetigers). One paratype ( ECOSUR), three fragments, many chaetae broken, one anterior and two medial ones, Sta. 7 (45°17.0' N, 13°16.0' E), 31 m, silty sand, 2 Dec. 2004, B. Mikac, coll. (anterior fragment 30 mm long, 4 mm wide, cephalic cage 9 mm long, 42 chaetigers; medial fragments 20–21 mm long, 36–41 chaetigers).

Additional material. Mediterranean Sea, Adriatic Sea, Croatia. Three specimens ( NHMR 17744 ), medial fragments, St. 107 (45°02.8' N, 13°19.0' E), 37 m, silty sand, 18 Oct. 2006, B. Mikac, coll. (10–27 mm long, 16–49 chaetigers) .

Description. Holotype (NHMR 17740) broken into two pieces, some parapodia previously removed, some chaetae broken; anterior fragment almost complete, posterior region with some chaetigers. Body brownish, posterior third paler; cylindrical, slightly tapered posteriorly; 76 mm long (70+6), 4.5 mm wide, cephalic cage (broken) 10 mm long, 150 chaetigers (125+25). Body papillae mostly without sediment particles, depressed; partly eroded in first chaetigers, 14–16 transverse rows per segment dorsally by chaetiger 10, about the same number ventrally, papillae smaller.

Cephalic hood barely exposed, margin smooth, one branchia and palps exposed. Other features observed in paratype (NHMR 17742). Prostomium low cone: eyes dark brown, anterior pair larger, laterally fused to posterior pair. Caruncle not seen. Palps thick, corrugated, about half as long as branchiae. Dorsal lip reduced, lateral lips expanded, ventral lip reduced.

Branchiae cirriform, arranged as two concentric rows, four filaments in a continuous row, and other four filaments arranged as two lateral pairs, all of about the same length and width. Nephridial lobes not seen.

Cephalic cage chaetae as long as 1/7 body length, more than twice as long as body width (3 x longer in paratype NHMR 17741). Chaetigers 1–3 forming cephalic cage; chaetae arranged in short series. Chaetigers 1–2 with longest chaetae, those in chaetiger 3 about twice as long as following ones, but about half as long as those in previous chaetigers. Chaetigers 1–2 with 10–12 notochaetae, 10 neurochaetae; chaetiger 3 with 8 chaetae per bundle.

Anterior dorsal margin of first chaetiger papillose. Chaetigers 1–3 of similar length. Chaetal transition from cephalic cage to body chaetae abrupt; anchylosed, falcate blunt neurohooks start from chaetiger 4 (aristate neurohooks in some paratypes). Gonopodial lobes not seen (even in specimens without tunic).

Parapodia poorly developed; chaetae emerge from low transverse lobes. Parapodia lateral; medial neuropodia ventrolateral. Notopodia and neuropodia with 3–4 long interramal papillae.

Medial notochaetae arranged in transverse to oblique series; all multiarticulated capillaries, articles short basally, medium-sized medially, long distally, 8–10 per fascicle, as long as 1/3–1/2 body width. Neurochaetae multiarticulated capillaries in chaetigers 1–3; anchylosed, slightly falcate, brownish neurohooks from chaetiger 4, arranged in transverse series, 7 per fascicle, reduced to 4 in pre-pygidial chaetigers.

Posterior end tapered into a cone; pygidium with anus dorsoterminal, without anal cirri.

Etymology. This species is named after Barbara Mikac, dear friend and colleague, in recognition of her publications on polychaete taxonomy, and because of her support towards my research activities. The epithet is a noun in the genitive case.

Remarks. Pherusa mikacae n. sp. groups with P. hobsonae n. sp., P. moorei n. sp., P. papillata ( Johnson, 1901) , and P. rullieri n. sp. because their body papillae are covered in little sediment, and their neurohooks start by chaetiger 4. However, P. mikacae is most similar to P. papillata by having falcate neurohooks, and 10–20 transverse series of papillae per segment. These two species can be separated because of their integument pigmentation, the shape of the papillae, the number of transverse rows of papillae per segment, and number of neurohooks in medial chaetigers. Pherusa mikacae has a brownish integument, its body papillae are depressed, arranged in 16–20 series per segment, and there are 5 neurohooks per bundle, whereas in P. papillata the integument is pale, dorsal papillae are digitate, arranged in fewer transverse rows (10–12) per segment, and there are fewer neurohooks per bundle (3–4). On the other hand, because of the presence of aristate neurohooks and by having about 20 series of papillae per segment, P. mikacae n.sp. resembles P. rullieri n. sp. from Benin (this paper). They differ because of their integument pigmentation, and the extent of anchylosed articles along neurochaetal exposed regions; in P. mikacae n.sp. integument is grayish and anchylosed articles extend about 2/3 of the neurochaetal length, whereas in P. rullieri integument is pale orange, and anchylosed articles are present along less than half of neurochaetal length.

Type locality. Off Istria, Croatia, Adriatic Sea, silty sands, at 37 m depth .

Distribution. The above material come from three localities in shallow water (31–37 m depth) in the northern Adriatic Sea. There are several records for P. plumosa ( Müller, 1776) in the Adriatic Sea, included as part of ecological papers; they indicate that the species lives in soft bottoms ( Katzmann 1972), at 60 m depth ( Katzmann 1973a, 1983), or in 50–215 m depth ( Katzmann 1973b); they may refer to the same species, but specimens must be studied before defining their geographical distribution in the region.

Figures

FIGURE 7. Pherusa mikacae n. sp. A. Holotype (NHMR 17740), anterior end, dorsal view. B. Paratype (NHMR 17741), anterior end exposed, ventral view (palps corrugated, branchiae smooth). C. Paratype (ECOSUR), anterior end, dorsal view. D. Same, ventral view. E. Same, anterior region, ventral view. F. Parapodium 12, notochaetae (inset: basal, medial and distal regions). G. Same, parapodium 12, neurochaetae with eroded tips (inset: paratype NHMR 17742, parapodium 10, tip of neurohook). Scale bars: A: 0.9 mm, B: 0.8 mm, C, E: 0.7 mm, D: 1.3 mm, F: 160 µm, G: 80 µm.