Pseudopolydora (Annelida: Spionidae) from the Arabian Gulf, Kuwait Author Radashevsky, Vasily I. 7637875A-94A6-4448-84AA-D7088014B501 A. V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevsky Street, Vladivostok 690041, Russia radashevsky@gmail.com Author Al-Kandari, Manal 632F0DFC-4397-41C3-96B2-E4ECA9053E01 Kuwait Institute for Scientific Research, 22107, Salmiya, Kuwait mkandari@kisr.edu.kw Author Malyar, Vasily V. 65B422D0-4894-49A9-8463-1817F922D6E4 A. V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevsky Street, Vladivostok 690041, Russia thebotkininc@gmail.com Author Pankova, Victoria V. 37E172EA-932A-4EF7-B5CB-4E85318CD26B A. V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevsky Street, Vladivostok 690041, Russia pankova.victoria@gmail.com text European Journal of Taxonomy 2021 2021-10-01 773 1 120 168 http://dx.doi.org/10.5852/ejt.2021.773.1519 journal article 267063 10.5852/ejt.2021.773.1519 2a85031f-9b9a-4dd9-b6f3-68a4b766e379 2118-9773 5544465 A018A660-F0D8-4411-AC25-77C089A75A57 Pseudopolydora kuwaiti sp. nov. urn:lsid:zoobank.org:act: 5144B89C-E979-44B7-8085-870ADEBFCC98 Figs 1C , 5E , 12–16 Pseudopolydora sp. C − Al-Kandari et al . 2019: 9 . — Radashevsky et al . 2020: table 1, fig. 1. Diagnosis Prostomium anteriorly notched to weakly incised, with two rounded lobes. Palps with up to 11 yellow bands. Occipital antenna absent. Anterior-row capillaries in notopodia from chaetiger 7 to chaetigers 9−14 with wide subtriangular, pennoned limbation. Chaetiger 5 larger than chaetigers 4 and 6, dorsally overlapping anterior part of chaetiger 6; lower (anterior-row) notopodial spines, with distal part of stem enlarged, cup-shaped, with a concavity on top and long pennoned, pointed tip. Pygidium small and fleshy, disc-like to cup-shaped, with dorsal gap to incision. Etymology The name refers to the type locality of the species in Kuwaiti waters. Material examined Holotype KUWAIT • 1 spec. ; Arabian Gulf , Al-Judailiat ; 29.377° N , 47.759° E ; 4 Feb. 2015 ; Vasily I. Radashevsky leg.; low intertidal; fine sand ; MIMB 40853 . Paratypes KUWAIT • 8 specs ; Arabian Gulf , Khor Al-Subiya ( Al-Shumaima ); 29.658° N , 48.1327° E ; 25 Nov. 2014 ; low intertidal; muddy sand + gravel around oyster aggregations ; MIMB 40708 • 2 specs ; northwest of Failaka Is. ; 29.4722° N , 48.2965° E ; 22 Dec. 2014 ; middle intertidal; on stone ; MIMB 40709 • 2 specs ; south of Boubyan Is. ; 29.6478° N , 48.3156° E ; 23 Dec. 2014 ; low intertidal; on stone ; MIMB 40710 • 45 specs ; Boubyan Is. ; 29.649° N , 48.3136° E ; 24 Jan. 2015 ; low intertidal; on empty shells and stones ; MIMB 40711 • 1 spec. ; Boubyan Is. ; 29.7897° N , 48.3727° E ; 25 Jan. 2015 ; upper intertidal; on stone ; MIMB 40712 • 17 specs ; same collection data as for holotype; MIMB 40713 • 2 specs ; Al-Doha ( Aushairij ); 29.388° N , 47.821° E ; 5 Feb. 2015 ; low intertidal; shells, sand, gravel, stone ; MIMB 40854 • 1 spec. ; Al-Bedaa ; 29.3228° N , 48.092° E ; 2 Mar. 2016 ; low intertidal; sand ; MIMB 40855 • 3 specs ; Auha Is .; 29.3764° N , 48.4391° E ; 29 Jan. 2017 ; low intertidal; from shell limestone encrusted by coralline alga ; MIMB 40856 • 1 spec. ; Ras Ajuza , Kuwait City ; 29.3913° N , 47.9967° E ; 29 Apr. 2017 ; low intertidal; sandy tube attached to the rock ; MIMB 40857 . Other material KUWAIT • 2 specs ; Auha Is. ; 29.3764° N , 48.4391° E ; 29 Jan. 2017 ; low intertidal; from dead coral encrusted by coralline algae and from shell of the gastropod Indothais scalaris (Shubert & J.A. Wagner, 1829) ; used in molecular analysis; VIR 19871 • 1 spec. ; east of Failaka Is. ; 29.3916° N , 48.3989° E ; l 4 Feb. 2017 ; low intertidal; from gastropod shell occupied by hermit crab; examined but not preserved ; VIR 20287 . Description Adults up to 6 mm long, 0.4 mm wide with 35 chaetigers ( Fig. 12A ). Fine black pigment usually scattered on dorsal and ventral sides of head and 10−13 anterior chaetigers ( Fig. 13A–C ). Up to 11 yellow bands (branched chromatophores) present on each palp when alive ( Figs 12A–C, E , 13B , 14A ), not visible after fixation. Prostomium anteriorly usually notched or weakly incised, with two rounded lobes ( Figs 12B , 13D ), occasionally blunt ( Fig. 13A ), posteriorly extending to end of chaetiger 2 as a low caruncle ( Fig. 14C ). Usually two pairs of black eyes present. Occipital antenna absent ( Fig. 12D ). Palps as long as 15−20 chaetigers, with longitudinal frontal groove lined with fine cilia, short motile compound cilia regularly arranged in one row along ciliated groove, and non-motile cilia arising from palp surface and scattered on lateral and abfrontal surfaces. Chaetiger 1 with short capillaries in neuropodia, short notopodial postchaetal lamellae and well-developed neuropodial lamellae; notochaetae absent. Notochaetae of chaetigers 2−4 and 6, and neurochaetae of chaetigers 1−7 slender capillaries with narrow wing. Anterior-row capillaries in notopodia from chaetiger 7 to chaetigers 9−14 (chaetiger 12 in holotype ) with wide subtriangular, pennoned limbation ( Figs 14C , 15A–B ), up to five in a series; superior and posterior-row notochaetae in these chaetigers slender capillaries with narrow wing; superior capillaries longer than posterior-row capillaries, with long narrow wing. Posterior notopodia with a few long alimbate capillary chaetae. Chaetiger 5 larger than chaetigers 4 and 6, dorsally overlapping anterior part of chaetiger 6, with up to four dorsal superior capillaries, two kinds of notopodial spines arranged in a curved diagonal or almost horizontal double row, and ten ventral capillaries; notopodial lamellae lacking but neuropodial postchaetal lamellae present, same as on chaetigers 4 and 6 ( Figs 12B, F , 13A ). Dorsal superior capillaries shorter and fewer than those capillaries on chaetigers 4 and 6. Ventral capillaries same in size, number and arrangement (in three groups) as those on chaetiger 4. Lower (anterior-row) notopodial spines, with distal part of stem enlarged, cup-shaped, with concavity on top and long pennoned, pointed distal tip ( Fig. 15C ), up to ten in a series. Upper (posterior-row) notopodial spines simple falcate ( Fig. 15C ), up to seven in a series. Newly developed spines in posterior part of curved series slightly larger than older spines in anterior part of series ( Fig. 12F ). Hooks in neuropodia from chaetiger 8, up to 11 in a series, not accompanied by capillaries. Hooks bidentate, with upper tooth closely applied to main fang; upper part of shaft with constriction; lower part of shaft bent at right angle in hooks in posterior neuropodia ( Fig. 15D–E ). Branchiae from chaetiger 7 to chaetiger 16 (chaetiger 16 in holotype ), up to ten pairs, fewer in small individuals ( Figs 5E , 14B ), free from notopodial postchaetal lamellae, flattened, with surfaces oriented perpendicular to body axis, with longitudinal ciliation (extension of nototroch) on inner anterior edge. In immature individuals and females, short nototroch present on chaetiger 3 and longer nototrochs with longer cilia from chaetiger 7 onwards, each composed of single row of ciliated cells extending onto branchiae on branchiate chaetigers. In males, nototrochs present from chaetiger 2 onwards, each composed of two rows of ciliated cells (anterior row extending onto branchiae; posterior row running only across chaetiger), and additional intersegmental transverse ciliary rows present from chaetiger 3, situated on anterior edge of chaetigers; cilia of nototrochs longer than those of intersegmental rows. In both sexes, nototrochs on branchiate chaetigers as transverse ciliary bands, on postbranchiate chaetigers gradually becoming U-shaped, with arms directed posteriorly. One or two pairs of short compound motile cilia usually present on dorsal side of each of chaetigers 4 and 5. Pygidium small and fleshy, disc-like to cup-shaped, with dorsal gap to incision ( Fig. 13E–F ), white due to numerous fusiform glandular cells with striated content. Glandular pouches in neuropodia from chaetiger 1, largest in chaetigers 6 and 7, single pouch in each neuropodium ( Fig. 15D ). Digestive tract without ventral buccal bulb and gizzard-like structure. Oesophagus narrow, extending through 7−8 anterior chaetigers. Main dorsal blood vessel transformed into gut sinus in anterior part of midgut. Heart body absent. Blood red, without globules or other elements. Fig. 12. Adult morphology of Pseudopolydora kuwaiti sp. nov. (live individuals, MIMB 40713). A . Left lateral general view, female, in reflected light, showing white chromatophores on palps. B–D . Anterior ends, in transmitted light, dorsal (B) and left lateral (C–D) view. E . Fragment of palp with chromatophore and inner blood vessel. F . Chaetigers 4–6, left lateral view, showing curved diagonal row of heavy spines in notopodium of chaetiger 5. Abbreviations: ho = hooded hooks; no = notopodial postchaetal lamella; pe = pennoned capillary notochaetae; su = dorsal superior capillary chaetae; ve = ventral capillary chaetae. Scale bars: A = 200 µm; B–D = 50 µm; E = 20 µm. Nephridia from chaetiger 4 onwards. In female fertile chaetigers, paired nephridia on each chaetiger opening to exterior via common middorsal nephridiopore anteriorly to nototroch. Habitat Adult P. kuwaiti sp. nov. inhabit silty tubes in muddy sand intertidally and in shallow waters and also bore in live mollusc shells, dead corals and shell limestone encrusted by coralline algae. While the species is comparatively rare, the population density in some local places can reach a maximum of one thousand individuals per 1 m 2 . In hard substrata, worms occasionally form aggregations of 1−3 individuals per 1 cm 2 . Reproduction Pseudopolydora kuwaiti sp. nov. is gonochoristic. Both in females and males, gametes developed from chaetiger 12 to chaetigers 16−29 ( Fig. 14D ). Paired testes or ovaries were attached to segmental blood vessels in fertile chaetigers. Fig. 13. Adult morphology of Pseudopolydora kuwaiti sp. nov. (live individuals, MIMB 40713). A–D . Anterior ends, dorsal (A, D) and ventral (B–C) view. E–F . Posterior ends, left lateral (E) and dorsal (F) view. Scale bars: A = 500 µm; B–C = 200 µm; D = 100 µm; E = 50 µm. Oogenesis was partly intraovarian ( Fig. 15F ). Developed coelomic oocytes were spherical, about 100 µm in diameter. Oocyte envelope was smooth, less than 1 µm thick. Spermatogonia proliferated in testes; spermatogenesis occurred in the coelomic cavity. Spermatids, each 3−4 µm in diameter, were joined in octads. Spermatozoa were introsperm with pointed acrosome about 1.5 µm long, straight elongated nucleus about 1.5 µm in diameter and 6 µm long, midpiece 3.5 µm (head + midpiece about 11 µm long), and a flagellum about 32 µm long (the precision of measurement of spermatids and parts of head of spermatozoa were at maximum to the nearest 0.5 µm and flagellum to the nearest 2 µm). Fig. 14. Adult characteristics of Pseudopolydora kuwaiti sp. nov. A . Relationships between number of yellow bands on palp and total number of chaetigers. B . Relationships between distribution of branchiae (referring to number of the last branchiate chaetiger) and total number of chaetigers. C . Relationships between caruncle length (in chaetiger numbers) and total number of chaetigers, and distribution of pennoned capillaries in notopodia (referring to number of the last chaetiger with pennoned capillaries) and total number of chaetigers. D . Relationships between distribution of gametes (referring to number of the first and the last chaetigers with gametes) and total number of chaetigers. Larval development in the plankton The spermatophores and egg capsules, typically produced by Pseudopolydora , were not observed in Pseudopolydora kuwaiti sp. nov. The 10−14-chaetiger larvae of this species were collected in plankton in March 2016 . The 14-chaetiger larvae were easily identified by the specific heavy spines in the notopodia of chaetiger 5. Small larvae, with heavy spines not yet developed, were identified by the specific pigmentation, revealed in larger larvae. 10-chaetiger larvae Larvae 500−550 µm long. Posterior middle part of prostomium slightly inflated as a caruncle but not extending over chaetiger 1. Nuchal ciliary patches on sides of caruncle at level of prototroch. Palps as long as about half of chaetiger 1. Notopodia with only provisional serrated bristles. Short adult capillaries in neuropodia of chaetigers 2−7. Heavy spines in chaetiger 5 and branchiae not yet developed. Hooks in neuropodia from chaetiger 8. Pygidium semispherical. Gastrotrochs on chaetigers 3, 5 and 7. Glandular pouches absent. One pair of protonephridia in chaetiger 1. Fig. 15. Chaetal and gamete morphology of Pseudopolydora kuwaiti sp. nov. (live individuals, MIMB 40713). A . Notopodia of chaetigers 8 and 9, showing pennoned capillaries in the anterior row of notochaetae. B . Notopodium of chaetiger 10, showing pennoned capillaries in the anterior row of notochaetae. C . Chaetae of chaetiger 5. D . A series of hooded hooks and glandular pouch from neuropodium of chaetiger 10. E . A series of hooded hooks from a posterior neuropodium. F . Female fertile chaetigers, left lateral view, showing vitellogenic oocytes in ovaries. Abbreviations: no = notopodial postchaetal lamella; su = dorsal superior capillary chaetae; ve = ventral capillary chaetae. Scale bars: A–E = 20 µm; F = 50 µm. 11-chaetiger larvae Larvae 550−600 µm long, with palps as long as 1−2 chaetigers. Notopodia with only provisional serrated bristles. Short adult capillaries in neuropodia of chaetigers 1−7; those in chaetiger 1 shorter and fewer than in succeeding chaetigers, 1−2 in a tuft. Notopodia of chaetiger 5 with 1−2 anterior-row spines with pointed distal tip, and one posterior-row heavy falcate spine among provisional serrated bristles. Branchiae not yet developed. Hooks in neuropodia from chaetiger 8. Glandular pouches in neuropodia from chaetiger 3 onwards; pouches in chaetigers 3−5 each composed of one small glandular cell; from chaetiger 6 onwards, each pouch composed of two cells. One pair of protonephridia in chaetiger 1. 12−13-chaetiger larvae Larvae 650−700 µm long, with palps as long as 2−3 chaetigers ( Fig. 16A ). Short adult capillaries in neuropodia of chaetigers 1−7. Chaetiger 5 with two kinds of heavy spines in notopodia, comprising three anterior-row spines and two posterior-row falcate spines. Single capillary chaetae with pennoned limbation in notopodia of chaetigers 7 and 8. Short branchial buds on chaetiger 7. Gastrotrochs on chaetigers 3, 5, 7 and 11. Glandular pouches in neuropodia from chaetigers 2−3. Protonephridia in chaetigers 1 and 2; metanephridia from chaetiger 4 onwards. 14-chaetiger larvae Larvae 700−750 µm long and up to 200 µm wide in middle part ( Fig. 16 B−E). Intense pigmentation comprising small melanophores and fine yellowish pigment scattered all along body, in anterior part of prostomium, in pharynx and in pygidium; distinct chromatophores absent. A small black spot present between median and lateral eyes on each side of prostomium. Small middorsal melanophores in anterior part of chaetiger 1 and on pygidium at level of telotroch; chaetiger 1 melanophore occasionally heavily ramified and hardly discernible. Small paired dorsal melanophores from chaetiger 3 onwards. Small dorso-lateral melanophores from chaetigers 3−4 onwards, usually indistinct, difficult to recognize. Single small lateral melanophores on either side on anterior edge of chaetiger 2; in some larvae, lateral melanophores appearing as indistinct spots of diffused black pigment. Prostomium anteriorly wide and rounded, posteriorly extending to middle of chaetiger 1 as a low narrow caruncle. Nuchal organs large round ciliary patches on sides of caruncle on anterior half of chaetiger 1. Occipital antenna absent. Three pairs of black eyes arranged almost in a transverse line, comprising one pair of small rounded median eyes and two pairs of lateral eyes; lateral eyes on each side situated close to each other and appearing as one comma-shaped eye. One pair of spherical unpigmented ocelli, each about 17 µm in diameter, present in front of pigmented eyes. One pair of compound motile cilia, each about 20 µm long, situated near median eyes, and one pair of compound cells, each about 75 µm long, situated near lateral eyes. One pair of palps arising from posterior dorso-lateral edges of peristomium, posterior to prototroch; each palp as long as about four chaetigers. Shallow frontal longitudinal groove on palps densely ciliated. Prototroch and telotroch well developed. Nototrochs and grasping cilia from chaetiger 3 onwards. Triangular neurotroch extending over ventral peristomial lip from mouth to end of chaetiger 1. Two small ciliated cells present on each side of neurotroch. Ventral ciliated pit absent. Gastrotrochs on chaetigers 5, 7 and 11, each composed of six large cells with numerous long cilia. Provisional serrated bristles in all notopodia including chaetiger 5; those in anterior chaetigers up to 175 µm long, gradually becoming shorted in succeeding chaetiger. Short adult capillaries in notopodia from chaetiger 2, and in neuropodia in chaetigers 1−7. Single capillary chaetae with flag-like limbation in notopodia of chaetigers 7 and 8. Chaetiger 5 with two kinds of heavy spines in notopodia in addition to short adult capillaries and long provisional bristles. Spines comprising 3−4 anterior-row spines with wide cup-shaped distal end of stem bearing long transparent pointed tip, and 2−3 posterior-row simple falcate spines. Hooks in neuropodia from chaetiger 8 onwards, up to five in a series, not accompanied by capillaries. Hooks bidentate, with upper tooth closely applied to main fang, with outer hood; lower part of shaft bent almost at right angle. Branchiae short, on chaetigers 7 and 8. Pygidium semispherical, divided into two rounded lobes by vertical median furrow and bearing four short papillae. Lateral sensory organs, each 4−5 µm in diameter, with thin non-motile cilia up to 20 µm long situated between noto- and neuropodia from chaetiger 1 onwards, including chaetigers 3−5. Numerous oval to spherical glandular cells with striated content present in anterior part of prostomium, on dorsal side of chaetigers, in pygidium and palps ( Fig. 16E ). Glandular pouches in neuropodia from chaetigers 1−2, very small in first chaetigers, large in chaetigers 6 and 7, gradually diminishing in size in succeeding chaetigers. Large lateral lips and small ventral lip of peristomium lined with numerous short cilia and forming voluminous vestibulum. Compound motile cilia up to 65 µm long present on lateral and ventral sides of lateral peristomial lips. Narrow oesophagus extending through three chaetigers. Gizzard-like structure absent in digestive tract. Numerous lipid globules up to 10 µm in diameter present in wall of voluminous midgut. Circulatory system developed and functional; blood transparent, without pigment. Two pairs of protonephridia in chaetigers 1 and 2. Metanephridia from chaetiger 4 onwards. Fig. 16. Larval and juvenile morphology of Pseudopolydora kuwaiti sp. nov. Live larvae in reflected (A–C) and transmitted (D–E) light. A . 13-chaetiger larva, dorsal view. B . 14-chaetiger larva, left lateral view. C . The same, ventral view. D . The same, dorsal view. E . The same, anterior end. F . 21-chaetiger juvenile, left lateral view. Scale bars: A–D = 100 µm; E = 50 µm; F = 500 µm. Settlement and metamorphosis 14-chaetiger larvae Larvae about 700 µm long easily settled and underwent gradual metamorphosis in Petri dishes. They started crawling and in the absence of sediment built transparent mucous tubes. The metamorphosis comprised loss of larval features, such as provisional bristles in notopodia, proto-, telo-, neuro-, gastrotrochs and grasping cilia, nototrochs on chaetigers 3−5, and also the transformation of the head and rapid elongation of the palps. The prostomium became distinctly separated from the peristomium. Nuchal organs transformed from oval ciliary patches to longitudinal narrow ciliary bands on the posterior sides of the prostomium. Lateral peristomial lips became reduced and transformed into dorso-lateral ciliary folds of the foregut. The ventral peristomial lip enlarged and formed the adult peristomium and basement for the palps. Unpigmented ocelli in the prostomium and larval protonephridia in chaetigers 1 and 2 became reduced and disintegrated. 20−21-chaetiger juveniles Juveniles about 2 mm long, with remains of yellowish pigment scattered on head and pygidium ( Fig. 16F ). Prostomium anteriorly narrow and rounded, posteriorly extending over 1−2 chaetigers. Occipital antenna absent. Palps as long as 12−15 chaetigers, without yellowish chromatophores or one chromatophore present on each palp. Capillary chaetae with pennoned limbation in notopodia of chaetigers 7−10. Branchiae on chaetigers 7−10. Glandular pouches in neuropodia from chaetiger 1. Metanephridia from chaetiger 4 onwards. Remarks Adult P. kuwaiti sp. nov. appear similar to the Asian Pacific Pseudopolydora diopatra Hsieh, 1992 . Both have yellow ramified chromatophores on palps, caruncles without occipital antenna extending to the end of chaetiger 2, and small cup-shaped pygidia ( Hsieh 1992 ). They differ from other Pseudopolydora by having greatly enlarged chaetiger 5 (instead of chaetiger 5 being similar in size to chaetigers 4 and 6) with the notopodial heavy spines arranged in a diagonal instead of a vertical double row, and also by the unique morphology of the pennoned spines, which have a stem with a cup-shaped distal end and a long pointed tip which is easily broken at the base. The two species differ from each other genetically but morphologically are very similar and can only be distinguished by small paired melanophores on the ventral side of the anterior chaetigers which are present in P. diopatra from the Asian Pacific and absent in P. kuwaiti sp. nov. from the Arabian Gulf. Larvae of P. kuwaiti sp. nov. appear similar to those of P. arabica (see Radashevsky & Al-Kandari 2020 ). Both occur in the plankton at the same time, have gastrotrochs on chaetigers 3, 5, 7 and 11, and are intensely pigmented with yellow and black pigments. They differ in that the larvae of P. arabica may postpone metamorphosis in the absence of substratum and attain 1250 µm long with 23 chaetigers, whereas the largest larvae of P. kuwaiti sp. nov. caught from the plankton were 750 µm long with 14 chaetigers. The developed 15−17-chaetiger larvae of P. arabica have one to three yellow ramified chromatophores on each palp, paired dorsal melanophores from chaetigers 6−7, dorso-lateral melanophores from chaetiger 4 to chaetigers 6−10, and one pair of small melanophores in lateral peristomial lips. In P. kuwaiti sp. nov. , chromatophores on palps appear in juveniles; the developed larvae have paired dorsal melanophores from chaetiger 3 onwards, and dorso-lateral melanophores from chaetigers 3−4 onwards; melanophores in lateral peristomial lips are absent. Pseudopolydora kuwaiti sp. nov. is the only species of the genus inhabiting soft sediments as well as boring into mollusc shells and dead corrals encrusted by coralline algae. Our genetic analysis confirmed the conspecificity of the tube-dwelling and shell-boring individuals ( Fig. 2 ). Distribution Arabian Gulf: Kuwait ( Fig. 1C ).