Polyophthalmus Quatrefages, 1850

Parapar, Julio, Al-Kandari, Manal, Candás, María & Moreira, Juan, 2021, A new species of Polyophthalmus (Annelida, Opheliidae) from the Arabian Gulf with an insight on internal anatomy and diversity of the genus, Zootaxa 5052 (4), pp. 501-528 : 522-523

Key to species of Polyophthalmus Quatrefages, 1850 of Indian and Pacific Oceans

The following tentative key comprises the seven Polyophthalmus species previously described in the Indian and Pacific oceans by Grube (1869), Kükenthal (1887), Michaelsen (1892), Purschke et al. (1995) and Magalhães et al. (2019), as well as the new species described here, P. zhadanae sp. nov. Some of these species had been synonimized with the NE Atlantic P. pictus and therefore the latter is also included in the key for comparisons. Material of previously described species has not been examined here; original descriptions and Magalhães et al. (2019; Table 1 ) were consulted to build the key. Some characters not explicitly mentioned in original descriptions were extracted from original illustrations. Type locality of each species is in brackets.

Characters used in Polyophthalmus keys are traditionally focused on body pigmentation, distribution of segmental eyes and chaetal length. We avoided diagnostic characters such as presence of pygidial cirri and parapodial cirri because they can only be visualized properly with SEM and therefore have been only described in recent works. In the same way, the presence and distribution of interparapodial organs is unknown for most of species. Study of type material and newly collected specimens in the Indo-Pacific will help to better characterize these taxa regarding the aforementioned diagnostic characters.

1. Segmental eyes in almost all body chaetigers.................................... P. pictus ( Dujardin, 1839) ( France)

- Segmental eyes absent in anterior most and posterior most chaetigers............................................ 2

2. Chaetae of last 5–7 chaetigers longer than previous ones and surpassing pygidium................................. 3

- Chaetae of last 5–7 chaetigers same length as previous ones................................................... 4

3. Anal marginal papillae elongate...................................... P. longisetosus Michaelsen, 1892 ( Sri Lanka)

- Anal marginal papillae digitate, short................... P. mauliola Magalhães, Rizzo and Bailey-Brock, 2019 (Hawaii)

4. Prostomium with distinctive pigmentation.................................................................. 5

- Prostomium lacking distinctive pigmentation............................................................... 6

5. Pigmentation present in dorsal region of prostomium and peristomium........... P. collaris Michaelsen, 1892 ( Sri Lanka)

- About 10 dark pigmented structures inside brain including ocelli; peristomium not pigmented......................................................................................... P. qingdaoensis Purschke et al., 1995 ( China)

6. Transverse bands of brown pigmentation similar in almost all segments.......................................... 7

- Transverse bands of brown pigmentation in two different patterns............................................... 8

7. Segmental eyes from CH 7 to CH 17........................................ P. australis Grube, 1869 (NE Australia)

- Segmental eyes from CH 5 to CH 16....................................... P. striatus Kükenthal, 1887 ( Hong Kong)

8. Nine pairs of lateral eyespots ( CH 7–15), all same size. Anterior body region ( CH 1–5) with two light brown bands; following segments with dorsal dark brown patches................................ P. ceylonensis Kükenthal, 1887 ( Sri Lanka)

- Twelve pairs of lateral eyespots ( CH 7–18); anterior and posterior ones smaller. Anterior body region ( CH 1–10) with a dense aggregation of dark brown spots and stripes (see Description), following segments with a combination of one anterior dorsal transverse band and two posterior dark brown spots........................ P. zhadanae sp. nov. ( Kuwait / Saudi Arabia)