The genus Ophelina Örsted, 1843 (Annelida: Opheliidae) in the coast of Kuwait (northern Indian Ocean), with the description of a new species

. Two species of the genus Ophelina Örsted, 1843 (Annelida, Opheliidae) are reported from the coast of Kuwait (Arabian Gulf) after specimens collected in the intertidal and shallow subtidal, namely Ophelina arabica sp. nov. and Ophelina grandis (Pillai, 1961). The new species is mainly characterised by features of the anal tube, which is provided with about 25 annulations at each side; the ventral margins are fully fused while dorsal margins are fused at most of their length but are free at the distal end in the shape of a conspicuous incision; the posterior end is opened with free margins; the anal tube also lacks marginal papillae but bears a pair of basal papillae and an unpaired anal cirrus attached to ventral margin at mid-length. Ophelina grandis is reported for the ﬁ rst time in the Arabian Gulf; specimens are fully described and compared with similar species. A key for species of Ophelina in the Indo-Paci ﬁ c, Southern Asia, Indo-Malay Archipelago and Australia, is also provided.


Diagnosis
[Following Wiklund et al. (2019) and Blake & Maciolek (2020).] Body elongate, with deep ventral groove and two lateral grooves along entire body length. Prostomium conical, sometimes with terminal palpode; eyes present or absent. Branchiae present or absent; if present, beginning on chaetiger 2, continuing to posterior end, sometimes missed from middle or last posterior chaetigers; branchiae single, cirriform. Segmental lateral eyes absent. Noto-and neuropodia with small fascicles of capillary chaetae; short ventral lobe present; small button-like dorsal cirrus sometimes present. Pygidium with anal tube sometimes bearing long unpaired anal cirrus, a pair of basal papillae, and several pairs of marginal papillae.
We added to the diagnosis of the genus the potential presence of "parapodial dorsal cirrus" that has been observed at least in several species, including the new species described below.

Diagnosis
Parapodial prechaetal lobe rounded throughout; short button-like dorsal cirrus; ventral lobe low and lingulate. Anal tube provided with about 25 annulations on each side; ventral margin fully fused; dorsal margin fused at most of their length but free at distal end as conspicuous incision; posterior opening well-defi ned, margins free. Anal tube lacking marginal papillae; one pair of basal papillae and unpaired anal cirrus attached to ventral margin at mid-length.

Etymology
The name of the new species refers to the Arabian Gulf, where the type specimens were found.

Remarks
Among the three species of Ophelina previously reported from the Arabian Gulf (see Introduction) ( Fig. 13), O. longicaudata is the only one described from the Indian Ocean (Indonesia); the shape of the   anal tube (Caullery 1944: fi g. 35b-c) is similar to that of O. arabica sp. nov., but they differ from each other in the following: 1) O. longicaudata lacks the disto-dorsal incision as present in O. arabica; 2) the posterior margins of tube opening are provided with papillae in O. longicaudata; 3) the unpaired anal cirrus is much longer in O. longicaudata (about two times as long as the anal tube) and protrudes from the interior of the tube, while in O. arabica the cirrus is attached to the external surface and about 0.5 times as long as the anal tube. On the other hand, Day (1967) illustrates the anal tube of specimens from South Africa attributed to O. longicaudata (Day 1967: fi g. 25.2.c); the marginal papillae are, however, larger than in the type specimens, and therefore these specimens may well correspond to another species.

Diagnosis
Parapodial prechaetal lobe elongated and triangular throughout; ventral lobe low and lingulate. Anal tube long, delicate, spoon-shaped, annulated; posterior and ventral margins free, tube opening welldefi ned, provided with about 15 pairs of marginal papillae; a pair of basal papillae and unpaired anal cirrus attached basally on ventral margin and projecting inside tube.

Fig. 10. Ophelina grandis
Other two species described from the Indian Ocean are similar to O. grandis: O. kampeni and O. langii (Kükenthal, 1887) (Fig. 12G-H). Ophelina kampeni also has an anal tube that is spoon-shaped and bears short marginal papillae along its free margins; the tube is also provided with a pair of basal papillae and unpaired anal cirrus within (Horst 1919: fi g. 1; Fig. 12G); this species lacks instead parapodial ventral cirri ("prechaetal lobe" in Horst 1919) and bears shorter branchiae not reaching median dorsal (2) branchiae are long and conspicuously pointed and quite crowded in last chaetigers; (3) anal tube is tubular in shape, translucent, opened ventrally and provided with >20 annulations (Kükenthal 1887: pl. xxi fi g. 5; Fig. 12H). However, the anal tube of O. langii has free ventral and posterior margins that lack marginal papillae, a pair of basal papillae and the unpaired anal cirrus (Horst 1919).
Ophelina longicaudata (Andaman Sea) and O. longicirrata Hartmann-Schröder & Parker, 1995 (South Australia) (Fig. 13) also bear an anal tube similar to that of O. grandis. However, O. longicaudata has the ventral margins totally fused, and the unpaired anal cirrus is much longer as explained above (Caullery 1944: fi g. 35). Regarding O. longicirrata, the anal tube is provided only with marginal papillae on the posterior margin (Hartmann-Schröder & Parker 1995: fi g. 11), that is, in turn, larger than in O. grandis, also lacking the pair of basal papillae and unpaired anal cirrus; Hartmann-Schröder & Parker (1995) refer, however, to a "ventral cushion that may be base of a lost unpaired cirrus" and also state that O. fauveli (Caullery 1944: fi g. 35) is close to O. longicirrata but bears a shorter anal tube (see also Remarks for O. arabica sp. nov.). Neave & Glasby, 2013 (North Australia) (Fig. 13) is distinguished from O. grandis because of the shorter branchiae, the shape of the anal tube, and having fewer and smaller paired marginal papillae (Neave & Glasby 2013). We also point to two further differences: (1)  Two European species were reported in the Arabian Gulf (namely O. cylindricaudata and O. acuminata), and their anal tube resembles that of O. grandis. In O. cylindricaudata, the anal tube is tubular in shape and about as long as the last six chaetigers. However, the ventral margin is fused and lacks marginal papillae, as in O. grandis (Kongsrud et al. 2011: fi g. 3c). Ophelina acuminata bears such papillae instead but the anal tube is spoon-shaped, and the pair of basal papillae are thicker than in O. grandis (Stop-Bowitz 1945: fi g. 3). Therefore, it is likely that the previous records of these two species in the Arabian Gulf may correspond to O. grandis or other still not described species.

Key to species of Ophelina described/reported in the Indian Ocean
The key comprises species of Ophelina originally described from the Indo-Pacifi c, Southern Asia, Indo-Malay Archipelago, and Australia, plus those two European species reported from the Arabian Gulf. The main characters used to discriminate among species are the anal tube features, including the unpaired anal cirrus, paired marginal papillae and the pair of basal papill ae.
We follow Rullier (1965), Kongsrud et al. (2011), Parapar & Moreira (2015), Moreira & Parapar (2017), Magalhães et al. (2019), and Parapar et al. (2021aParapar et al. ( , 2021b when using the term "anal tube" instead of many others used before (see Remarks to the diagnosis of genus). Anyhow, we must state that this structure is a pygidial construction instead of being only restricted to the anal part itself and that the shape of the anal tube is not indeed "tubular" in all species. Besides, the anal tube shape is also a relevant diagnostic character, but various terms in the literature refer to its very shape. Therefore, the two main appearances are used in the key: 1) tube longer than wide ("groove-shaped") and 2) tube as long as wide ("spoon/hood-shaped").
Other body characters of high taxonomic relevance in the genus Ophelina were not used in this key, such as the parapodial shape. Because many available descriptions (especially those from the early 20 th century) still need to be completed; this would require a revision of the available type material of a number of species. Such revision might eventually result, in turn, in the erection of new species. Redescriptions and taxonomic comments are available across the literature for several species, but we intended to follow original descriptions and illustrations as much as possible unless indicated otherwise.
The key also includes the European O. acuminata Örsted, 1843 and O. longicaudata (Caullery, 1944) because they have been previously reported in the Indian Ocean. However, these records might actually correspond to other described and/or new species. On the other hand, three species were not included in the key: 1) Ophelina dubia (Caullery, 1944): the original description does not describe the anal tube, apparently lost ("Le tube anal manque sur l'échantillon", Caullery 1944: 45).
2) Ophelina ehlersi (Horst, 1919): the original description confi rms the presence of paired basal papillae but states that "The anal tube is short (?broken off)" (Horst 1919: 23), and therefore the presence of paired marginal papillae and unpaired anal cirrus is not mentioned/confi rmed.
3) Ophelina kükenthali (Horst, 1919): the original description reports the anal tube as "gutter shaped", and the presence of the unpaired anal cirrus and 8-9 "cirri" on the posterior margin (supposedly the paired marginal papillae), but no illustration is provided and sizes/proportions among each other are not mentioned. Later, Neave & Glasby (2013) wrongly state that this species lacks the unpaired anal cirrus, and bears instead the pair of basal papillae.
The type locality of each species is indicated between brackets.
(1) Eibye-Jacobsen (2002) describes specimens identifi ed as Ophelina cf. cordiformis from the Andaman Sea and discusses similarities/differences with the only type specimen of O. cordiformis, which is damaged according to the original description by Caullery (1944).
(2) "Je n'y ai pas aperçu de papilles marginales, ni de branchie anale" (Caullery 1944: 46). The original description and drawings by Caullery (1944) for O. brevibranchiata are much simpler than those provided for other species in the same work; therefore, this species is not well characterised morphologically yet.
(6) Caullery (1944) states in the original description that the unpaired anal cirrus is not present ("Je n'ai pas vu de branchie anale"; Caullery 1944: 47); however, Caullery (1944: fi g. 38c) illustrates a long cirrus coming out from the interior of the anal tube that might likely correspond to a true unpaired anal cirrus.
(7) Ehlers (1918) mentions in the anal tube a "a brownish, short ovate body" (in German in original source: "ein bräunlicher, kurz eiförmiger Körper"; Ehlers 1918: fi gs 2-3 in table xvii). This structure might correspond to the only papilla remaining of the pair of basal papillae as present in other species. Furthermore, Neave & Glasby (2013) describe a "second protrusion" that we recognise as the unpaired anal cirrus. (8) The concept provided by Neave & Glasby (2013) for this species is different to that of the original description (see remarks above). (9) This feature might have been overlooked in the original descriptions of some species. (10) This feature is also present in European specimens of O. acuminata but not in specimens from South Africa illustrated by Day (1967); the latter may, therefore, represent a different species (see Remarks for O. arabica sp. nov.).
(11) The descriptions by Eibye-Jacobsen (2002) for specimens identifi ed as belonging to O. grandis and O. sibogae differ from the original descriptions regarding features of the anal tube; therefore, these specimens might represent undescribed species (see also Remarks for O. arabica sp. nov.).

Discussion
Taxonomy of genus Ophelina is still hindered by a number of issues: (1) Lack of consistent descriptions of species regarding relevant characters and their nomenclature, particularly for studies done before the 21 st century; for instance, terminology for the anal tube papillae is quite variable across the literature.
(2) Discrimination among species often relies only on features of the anal tube.
(3) Differences in knowledge among geographic areas, with some regions still poorly studied.
(4) Species originally described from NE Atlantic are often reported from other latitudes, and these records might actually represent other species.
This overall situation applied to opheliid knowledge in the Arabian Gulf. As stated previously, several species that were reported there, i.e., P. pictus, O. acuminata and O. af. cylindricaudata, were described from European waters by the 19 th century. However, recent work based on examining a large number of intertidal samples from Kuwait revealed the presence of a new species of Polyophthalmus Quatrefages, 1850 (Parapar et al. 2021a). The present study is a follow-up to that work and allowed us to describe a new species of Ophelina and provide the fi rst record of O. grandis for the Arabian Gulf. Therefore, the identity of opheliids previously reported in the Arabian Gulf should be reconsidered and revised. Finally, a full review of the genus Ophelina would be desirable but based on consistent terminology for taxonomic characters and a full redescription of species that need an adequate description.