Nereis quadrata, Bonyadi-Naeini & Glasby & Rahimian, 2025

Nereis quadrata View in CoL sp. nov.

http://zoobank.org:act: CAF75B15-CA14-48E1-9524-160177E70C3

( Figures 5 A–C View FIGURE 5 , 6 A–D View FIGURE 6 , 7 A–H View FIGURE 7 )

Material examined. Holotype: Qeshm Island – Tola village , ( 26° 59' 36.30" N, 56° 13' 03.20" E), ZUTC 7062 , intertidal zone, sandy beach covered with cobble, collected by Bonyadi-Naeini A., 4 May 2008. GoogleMaps

Paratypes: Kish Island– Mir Mohana , Arabs district ( 26° 34' 11.20" N, 53° 55' 52.59" E), ZUTC 7057 GoogleMaps ; Jask ( 25° 38' 12.80" N, 57° 46' 25.15" E), ZUTC 7064 GoogleMaps ; Hormoz Island , Research Station ( 27° 03' 01.00" N, 56° 29' 58.00" E), ZUTC 7067 GoogleMaps ; Farur Island ( 26° 17' 15.03" N, 54° 32' 22.96" E), ZUTC 7075 GoogleMaps .

Description. Holotype. Body complete with 92 chaetigers. Colour in alcohol creamy, with no pigmentation from anterior part to end of body ( Fig. 5A View FIGURE 5 ). The total length post-fixation 22 mm, maximum width 2 mm at chaetiger 12 including parapodia. Body flattened and tapered posteriorly. Prostomium slightly wider than long, with palps slightly longer than wide. Palps with barrel-shaped palpophore, transverse groove lacking; palpostyles conical. Palps and all parts of prostomium without pigmentation. One pair of antennae and four pairs of tentacular cirri, with longest reaching chaetiger 9 ( Figs 5B View FIGURE 5 , 6A View FIGURE 6 ). Pharynx has yellow to light brown jaws, with 6–7 teeth (figs 5B & C). Paragnaths on maxillary ring arranged as follows: I = 3 conical paragnaths arranged in triangle, II= 13–14 minute and large horny paragnaths arranged in wedge shape (figs 5B, 6A), III = group of 22 minute conical paragnaths in long patch, IV = 28–34 minute and large horny paragnaths arranged in wedge shape ( Figs 5C View FIGURE 5 , 6B View FIGURE 6 ). Paragnaths on oral ring arranged as follows: V = 4 minute conical paragnaths arranged in triangle shape, with larger one at triangle apex, VI = 9–10 minute conical paragnaths arranged in wedge shape ( Figs 5B View FIGURE 5 , 6A View FIGURE 6 ), VII–VIII = wide band consisting of a large number of fine and coarse conical paragnaths, fine paragnaths in Area VII arranged in hollow squares toward jaws, width of band decreases in Area VIII with coarse paragnaths ( Figs 5C View FIGURE 5 , 6B View FIGURE 6 ). Tentacular belt about 2x the length of first chaetiger.

Parapodium of chaetiger 10 with two ligules. Dorsal notopodial ligule as large as ventral ligule. Dorsal cirrus significantly longer (4–5x) than dorsal ligule. Anterior neuropodia with two ligules, postchaetal lobes present. Neuropodial acicular ligule conical and longer than ventral neuropodial ligule. Ventral cirri shorter than both ( Fig. 6C View FIGURE 6 ). Notochaetae homogomph spinigers ( Fig. 7A View FIGURE 7 ). Neurochaetae in dorsal fascicle include homogomph spinigers ( Fig. 7B View FIGURE 7 ) and in ventral fascicle heterogomph spinigers ( Fig. 7C View FIGURE 7 ) and heterogomph falcigers, with short blade serrated for most of length ( Fig. 7D View FIGURE 7 ).

Parapodium of posterior chaetiger (80 th): Dorsal notopodial ligule larger and longer than ventral notopodial lobe but not markedly expanded or lamellate. Dorsal cirrus long and terminal. Acicular neuropodial ligule reduced. Ventral neuropodial ligule conical and smaller than acicular neuropodial ligule. Ventral cirri shorter than ventral neuropodial ligule ( Fig. 6D View FIGURE 6 ). Notochaetae one homogomph falciger, straight and smooth tip without serrations ( Fig. 7E View FIGURE 7 ). Neurochaetae in dorsal fascicle homogomph spinigers ( Fig. 7F View FIGURE 7 ) and heterogomph falcigers with short blades. Neurochaetae in ventral fascicle heterogomph spinigers ( Fig. 7G View FIGURE 7 ) and heterogomph falcigers with short blades serrated for most of length ( Fig. 7H View FIGURE 7 ).

Pygidium with a pair of long cirriform cirri.

Variation in 20 paratypes: Size ranges from 25–30 mm in length and 1–3 mm in width at widest part of the body. Chaetiger numbers range from 60–118. Paragnath counts as follows: Area I = 2–6; Area II = 9–16; Area III = 20–31; Area IV = 28–39; Area V = 4–9 (specimens with more than 4 paragnaths have larger paragnaths at top of pyramid and paragnaths decreasing in size towards base of pyramid); Area VI = 6–10; Area VII –VIII = numerous conical paragnaths .

Ecology. The holotype and paratypes of Nereis quadrata sp. nov. were collected from four localities along the Persian Gulf , representing distinct intertidal habitats. Material was collected from Qeshm Island ( Tola village , intertidal zone, sandy beach with cobble cover), Kish Island ( Mir Mohana , Arabs district , rocky–sandy substrate), Hormoz Island ( Research Station , rocky–stony–sandy substrate), and Farur Island (rocky habitat with coral assemblages). The occurrence of this species in heterogeneous substrates across multiple islands suggests a relatively broad ecological tolerance within the intertidal environments of the region .

Etymology. The species name is inspired by the distinctive arrangement of paragnaths in Area VII, resembling hollow squares.

Remarks. Five Nereis species occur in the Persian Gulf and Gulf of Oman up to now. The material studied was compared with these five Nereis species based on 12 features ( Table 5). The studied material is the most similar Nereis pelagica Linnaeus, 1758 , Nereis persica Fauvel, 1911 and Nereis neogracilis Mohammad, 1970 . The present material differs from Nereis pelagica Linnaeus, 1758 , in four features: more paragnaths in Area V (4–9 vs 0) and Area VI (6–10 vs 4–5), the shape and arrangement of paragnaths Area VI (minute and large horny paragnaths arranged in a wedge shape vs large cones in a cross) and the arrangement of paragnaths in Area VII–VIII (a wide band consisting of a large number of fine and coarse conical paragnaths, fine paragnaths in Area VII arranged in hollow squares near the jaw, the width of the band decreases in Area VIII with coarse paragnaths vs a broad band with an anterior row of large cones and two or three posterior rows of fine cones). The material studied is also similar to Nereis persica Fauvel, 1911 , but it differs from Nereis persica by having more paragnaths in Area I (2–6 vs 0–1), Areas III (20–31 vs a few) and Area V (4–9 vs 0); the arrangement of paragnaths in Area VII–VIII (a wide band consisting of a large number of fine and coarse conical paragnaths, fine paragnaths in Area VII arranged in hollow squares near the jaw, the width of the band decreases in Area VIII with coarse paragnaths vs a broad band with an anterior row of large cones and two or three posterior rows of fine cones; and shape of posterior notopodial homogomph falcigers (short smooth cones vs with one to two blunt teeth). The present material differs from Nereis neogracilis Mohammad, 1970 in three features: numbers and arrangement of paragnaths Area V (4–9 minute conical paragnaths arranged in triangle shape in material studied vs 5 large cones followed by a curved transverse row of 8 smaller ones and behind each end of the latter there is a single cone in Nereis neogracilis Mohammad, 1970 ); and the shape of the dorsal ligule posteriorly (dorsal notopodial ligule larger and longer than ventral notopodial lobe but not markedly expanded or lamellate in material studied vs not markedly expanded or lamellate in Nereis neogracilis Mohammad, 1970 ). The other three Nereis species recorded in the Persian Gulf and Gulf of Oman show fewer similarities to the new species. Also, eight other species ( Nereis (Nereis) gaikwadi Day, 1973 , Nereis (Nereis) gilchristi Day, 1967 , Nereis (Nereis) ethiopiae Day, 1965 , Nereis filicaudata Fauvel, 1951 , Nereis ghardaqae Hartmann-Schröder, 1960 , Nereis granulata Day, 1957 , Nereis longilingulis Monro, 1937 , Nereis sarsoensis Hartmann-Schröder, 1960 ) occurring in the Indo-Pacific were compared with the new material studied. Among these, none of the species display the same combination of morphological features as in Nereis quadrata sp. nov., as detailed below.

Nereis quadrata sp. nov. differs from Nereis gaikwadi Day, 1973 in several characters, particularly the number and arrangement of paragnaths in Areas III and IV (20–31 and 28–39 in Nereis quadrata sp. nov. vs ~15 and ~ 20 in Nereis gaikwadi ). Furthermore, Nereis quadrata sp. nov. possesses 4–9 paragnaths in Area V and 6–10 in Area VI, whereas Nereis gaikwadi has only 1 and 5–6. Nereis quadrata sp. nov. also displays a distinct paragnath band in Area VII with fine cones arranged in hollow squares—this pattern is absent in Nereis gaikwadi , which shows only a simple band 4–5 deep. Nereis quadrata sp. nov. possesses short, smooth lacks posterior homogomph falcigers, while Nereis gaikwadi possesses one or two homogomph falcigers with short, curved blades bearing a single small tooth.

Compared with Nereis gilchristi Day, 1967 , Nereis quadrata sp. nov. shows a greater number of paragnaths in all regions where data are available. For example, Area III in Nereis gilchristi is characterized by only a few scattered cones, while Nereis quadrata sp. nov. shows a dense group of 20–31 cones. Additionally, Nereis gilchristi has a markedly expanded dorsal ligule, in contrast to the non-expanded yet prominent dorsal ligule of Nereis quadrata sp. nov. Nereis ethiopiae Day, 1965 shares with Nereis quadrata sp. nov. the lack of pigmentation and an unnotched prostomium, but differs by having uniformly small, subequal cones and fewer paragnaths in Area I (1 vs 2–6), Area VI (15 vs 28–39), and Area VI (3–4 vs 6–10). The posterior notopodial falcigers in Nereis ethiopiae are conical and smooth, similar to those of Nereis quadrata sp. nov., but the paragnath arrangement in Area VII–VIII (irregular rows) is simpler than the structured hollow-square pattern seen in Nereis quadrata sp. nov. Compared with Nereis filicaudata Fauvel, 1951 , Nereis quadrata sp. nov. possesses significantly more paragnaths and more complicated paragnath arrangements. Nereis filicaudata lacks paragnaths in Area I and has very reduced groups in other areas, with Area VI showing a formulaic arrangement (2+2, etc.) and Area VII–VIII represented by a single row of cones. Additionally, Nereis filicaudata lacks posterior homogomph falcigers, while Nereis quadrata sp. nov. possesses short, smooth ones.

Nereis ghardaqae Hartmann-Schröder, 1960 View in CoL shares with Nereis quadrata View in CoL sp. nov. a lack of pigmentation and notched prostomium, but it displays a far simpler paragnath pattern with only 1 cone in Area I and up to 6 in Area VII–VIII, compared to the complex bands and large counts found in Nereis quadrata View in CoL sp. nov. with falcigers similar in shape but do not present the same distribution density.

Nereis granulata Day, 1957 View in CoL is similar in having smooth falcigers, but is clearly differentiated by the pigmentation, nature of its paragnaths, which are minute and granular. Paragnath counts are also lower, and Area VII–VIII forms a broad, almost colourless ventral band, lacking the defined hollow-square pattern of Nereis quadrata View in CoL sp. nov.

Nereis longilingulis Monro, 1937 View in CoL is characterized by highly reduced paragnath numbers, with only crescentic patches in some areas and single cones in others, notably lacking in Area V. This minimalism in paragnath development sharply contrasts with the dense fields and complex geometry seen in Nereis quadrata View in CoL sp. nov.

Finally, Nereis sarsoensis Hartmann-Schröder, 1960 , differs in having fewer paragnaths in almost all areas and pigmentation on the prostomium. Area V, for example, shows only 3 cones arranged vertically compared to 4–9 in a triangle in Nereis quadrata sp. nov. Its falcigers have toothed terminal blades, unlike the smooth ones in the new species ( Table 5).