Neanthes biparagnatha, Bonyadi-Naeini, Alieh, Rastegar-Pouyani, Nasrullah, Rastegar-Pouyani, Eskandar, Glasby, Christopher J. & Rahimian, Hassan, 2017

Bonyadi-Naeini, Alieh, Rastegar-Pouyani, Nasrullah, Rastegar-Pouyani, Eskandar, Glasby, Christopher J. & Rahimian, Hassan, 2017, Nereididae (Annelida: Phyllodocida) of the Persian Gulf and Gulf of Oman, including description of two new species and 11 new records, Zootaxa 4244 (1), pp. 91-117 : 98-101

Neanthes biparagnatha sp. nov.

( Figs 2 A–E , 3 A–C , 4 A–J )

Material examined. Holotype, Qeshm, North Beach (N 26° 58' 17.22", E 56° 15' 32.43"), intertidal zone, sandy beach covered with cobble, collector Bonyadi-Naeini A., 26 June 2013, ZUTC 6169.

Paratypes: Bushehr, Daneshju Park Beach (28° 48' 23.84" N, 50° 53' 54.09" E), ZUTC 6156 (three specimens) ; Qeshm, North Beach (26° 58' 17.22" N, 56° 15' 32.43" E), ZUTC 6169 , (six specimens); Hormoz Island , Center of Ecosystem Research (27° 03' 01" N, 56° 29' 58" E), ZUTC 6158 , (two specimens); Djod (25° 26' 33" N, E 59° 31' 00" E), ZUTC 6155 , (four specimens) ; Qeshm Island- Tola village , (26° 59' 36.3" N, 56° 13' 03.2" E), ZUTC 6157 , (one specimen).

Etymology. The species name, biparagnatha , refers to presence of two types of paragnaths in Area IV of the pharynx in this species.

Description. Holotype specimen broken in two pieces: anterior part is about 21 chaetigers, and posterior part about 51 chaetigers. Total length before fixation 43 mm long, 2.5 mm wide. Body flattened, tapering posteriorly. Color in alcohol creamy yellow. Prostomium slightly wider than long with two brownish lines extending from base of antennae to near eyes ( Fig. 2A , Fig. 3A ). Palps longer than wide and longer than antennae. Pharynx everted with translucent yellow to dark brown jaws with eight teeth. Conical paragnaths and short bars also present in Area IV ( Fig. 2B , Fig. 3C ), arranged as follows: Area I = 1; II = 6 (left), 6 (right), triangular shaped, III = 27 in a crescent group; IV = 27 (left), 32 (right), 5 bars on each side of area IV, and close to the jaws ( Fig. 2 B ); V = 2 in a single line; VI, VII, and VIII coalescent and composed of more than three irregular rows, VI = 1 (left), 1 (right) large cone, VII–VIII = 91, in a wide band composed of two irregular group of cones, distal group with larger cones than those of proximal group ( Fig. 2C , Fig. 3B ). Parapodium of chaetiger 10: Notopodium with two ligules. Dorsal cirrus longer than dorsal notopodial ligule. Ratio of DC/ DNL: 1.58. Dorsal and ventral notopodial ligules conical, ventral ligule smaller than dorsal ligule. Small acicular lobe present. Neuropodium with two ligules. Digitiform postchaetal lobe present. Ventral neuropodial ligule conical, rounded distally, approximately equal in length with acicular ligule. Ventral cirri equal in length with neuropodial acicular ligule ( Fig. 2 D ). Notochaetae homogomph spinigers, arranged in single row between dorsal and ventral ligules ( Fig. 4 F ). Neurochaetae in dorsal fascicle include homogomph spinigers ( Fig. 4 G ) and heterogomph falcigers ( Fig. 4 I ); in ventral fascicle are heterogomph falcigers. Falcigers with short and serrated blade ( Fig. 4 H&I ). Parapodium of posterior chaetigers: Dorsal cirrus longer than dorsal notopodial ligule in anterior chaetigers, slightly longer than anterior one. Ratio of DC/ DNL: 1.48. Dorsal cirri becoming longer posteriorly, up to 1.5 times longer in most posterior chaetigers. Dorsal notopodial ligule conical, becoming pointed and smaller in posterior chaetigers. Acicular neuropodial ligule conical and a distinct digitiform postchaetal lobe reduced in middle chaetigers and disappearing in posterior chaetigers. Ventral neuropodial ligule conical, smaller, pointed and reduced in posterior chaetigers ( Fig. 2 E ). Neurochaetae in dorsal fascicle are homogomph spinigers ( Fig. 4 A ) and heterogomph falcigers with short blades ( Fig. 4 B ). Neurochaetae in ventral fascicle are heterogomph falcigers ( Fig. 4 C ). Paired, cirriform long pygidial cirri present.

Variation in 15 paratypes: Size range from 6.98 mm to 44.33 mm (mean 26.64 mm) long, 0.8 mm to 4.56 mm (mean 2.17 mm) wide. Paragnath counts as follows: I = 1; II = 2–8; III = 14–32, in crescent group; IV = 11–34, also 3–6 short bars on either side; V = 1–3; VI = 1 large cone; VII–VIII = 59–97 in wide band of different-sized cones. Paragnaths often conical and dark with large base, including short bars in Area IV. Dorsal cirrus in some specimen smaller than dorsal notopodial ligule. Ratio of DC/ DNL 0.639–1.85 and 0.84 –1.69 in anterior and posterior parapodia, respectively. Anterior neurochaetae in ventral fascicles include homogomph spinigers, heterogomph falcigers, and sesquigomph falcigers. Posterior neurochaetae in dorsal fascicles include homogomph and heterogomph spinigers. Posterior neurochaetae in ventral fascicles are heterogomph falcigers, heterogomph spinigers ( Fig. 4 J ), sesquigomph falcigers ( Fig. 4 D&E ).

Remarks. The new species resembles the description of Neanthes deplanata Mohammad, 1971 , but can be distinguished by having 3–6 bar-shaped paragnaths in each side of Area IV ( Fig. 2 B , 3 C ; table 3). Neanthes deplanata , similar to the present species, also has a triangular cluster of conical paragnaths, but unlike N. biparagnatha sp. nov. has no bars on Area IV. Also, the two species differ in the number of paragnaths in Area III ( Fig. 2 C , 3 B ). Neanthes deplanata has 14, but the present specimens have more cones (14–32 cones). Further, N. deplanata has heterogomph spinigers in the ventral fascicle of posterior neuropodia, but the holotype of the new species has none, although a single heterogomph spiniger was present in this position in a few paratypes ( Fig. 4 J ). The new species is also similar to Neanthes unifasciata ( Willey, 1905) , but can be easily distinguished by the number, size and patterns of the paragnaths and also the body size. The new species differs from Neanthes willeyi ( Day, 1934) in the number and pattern of paragnaths of Area IV (3–6 short bars on either side vs no bars) and Areas VI-VII-VII (paragnaths in Area VI-VII-VIII are coalescent vs Areas VI with a prominent group of 4–8 cones). Other distinguishing characteristics of the new species, and comparisons with its close congeners, are presented in Table 3.

Figures

FIGURE 2. A – E. Neanthes biparagnatha sp. nov., A: Dorsal view of everted proboscis. B & C: Ventral view of everted proboscis. D: Parapodium Chaetiger 10, anterior view. E: Posterior parapodium, anterior view.

FIGURE 3. A – C. Neanthes biparagnatha sp. nov., A: Dorsal view of anterior part of body. B & C: Ventral view of anterior part of body.

FIGURE 4. A – J. Neanthes biparagnatha sp. nov., A: Dorsal fascicle neuropodial homogomph spiniger, posterior chaetiger. B: Dorsal fascicle neuropodial heterogomph falciger, posterior chaetiger. C: Ventral fascicle neuropodial heterogomph falciger, posterior chaetiger. D & E: Ventral fascicle neuropodial sesquigomph falciger, posterior chaetiger. F: Notopodial homogomph spiniger, chaetiger 10. G: Dorsal fascicle neuropodial homogomph spiniger, chaetiger 10. H: Ventral fascicle neuropodial heterogomph falciger, chaetiger 10. I: Dorsal fascicle neuropodial heterogomph falciger, chaetiger 10. J: Ventral fascicle neuropodial heterogomph spiniger in variations, posterior chaetiger.