Cirolanidae, Dana, 1952

Anil, Pathan, Bruce, Niel L. & Jayaraj, Kadeparambil Arjunan, 2024, A new species of Cirolana Leach, 1818 (Isopoda, Cymothoidea, Cirolanidae), from Havelock Island, Andaman Sea, northern Indian Ocean, Zootaxa 5418 (1), pp. 57-71 : 67-68

Key to the marine and estuarine genera of Cirolanidae of the northern Indian Ocean

This key covers the coastal and estuarine waters of Pakistan, India, Sri Lanka, the Maldives, Bangladesh, Myanmar and western Thailand. This entire region is very poorly documented with regard to Cirolanidae , with the exception of Pakistan where there has been some documentation of intertidal taxa (e.g. Bruce & Javed 1987; Javed & Yasmeen 1995; Yasmeen 2005, 2008 inter alia). More recently Cirolanidae have been described from the Andaman Islands ( Anil & Jayaraj 2023 and references therein) and also from the western coasts of Thailand ( Rodcharoen et al. 2016). The limited records of Cirolanidae suggest that any key to the species of the larger genera, which includes Cirolana , would be very premature given that a wealth of species remains to be discovered and described, notably from coral reef habitats and the faunistically rich continental shelf and slope. Premature species keys lead to misidentifications and then to the perpetuation of misapplied names. It is hoped that this key to the genera will expedite the further identification of Cirolanidae in the region.

1. Clypeus ventrally flat; pleon short (<20% of body length, usually 10 – 14%); pleonite 4 may be laterally enclosed by pleonite 3; pleonite 5 always laterally enclosed by pleonite 4............................................................ 2

- Clypeus with ventrally-or antero-ventrally projecting blade; pleon usually long (10 – 35% of body length, usually 15 – 35% of body length); pleonites 4 and 5 with free lateral margins or with free postero-lateral angle (rarely laterally enclosed by pleonite 4) [Eurydicinae]...................................................................................... 3

2. Pereopods 1 – 3 with ischium and merus antero-distal angles strongly produced; pereopods 5 – 7 with abundant slender setae and acute robust setae; antennal peduncle articles 3 and 4 subequalin length and shorter than article 5 [Conilerinae]........... 9

- Pereopods 1–3 with ischium and merus anterodistal angles not or weakly produced, inferior margins usually with blunt ‘molariform’robust setae; pereopods 5 – 7 usually with few slender setae and acute robust setae; antennal peduncle articles 1 – 3 short, 4 and 5 subequal in length and longest [Cirolaninae]................................................... 11

3. Antennula peduncle articles 2 and 3 set at right angles to article 1; uropod peduncle posterior mesial margin not produced; male pleopod 2 endopod with appendix masculina attached at mid-length on mesial margin.............. Eurydice Leach, 1816

- Antennula peduncle articles1to 3 colinear; uropod peduncle posterior mesial margin produced; male pleopod 2 endopod with appendix masculina attached sub-basally................................................................... 4

4. Pleonite 5 laterally enclosed by pleonite 4; pleotelson lateral margins sinuate, posterior margins narrowly rounded; anterior pereopods with connate spines.............................................. Aphantolana Moore & Brusca, 2003

- Pleonite 5 with free lateral margins, or free postero-lateral point; pleotelson lateral margins not sinuate, posterior margin various, truncate or linguiform or with apical point; anterior pereopods without connate spines........................ 5

5. Uropodal exopod cylindrical, exceeds endopod length, exopod 1.3 – 2.2 times as long as endopod; pleotelson posteriorly narrow, lateralmargins concave....................................................... Atarbolana Bruce & Javed, 1987

- Uropodal rami lamellar, sub-equal in length pleotelson not posteriorly narrow, lateral margins convex.................. 6

6. Adult male antennula peduncle dilated; flagellae of both antennula and antenna extending beyond pleotelson posterior margin [pelagic; nektonic]............................................................... Pontogelos Stebbing, 1910

- Not as above......................................................................................... 7

7. Antennula peduncle article 2 longest; frontal lamina posteriorly narrowed, not abutting clypeus; pereopod 1 subchelate, pereopods 2 – 7 slender, with few robust and slender setae.............................. Metacirolana Kussakin, 1979

- Antennula peduncle article 3 longest; head with prominent rostral point; frontal lamina usually not posteriorly narrowed, abutting clypeus; pereopod 1 ambulatory, pereopods 2 – 7 robust, with abundant robust and slender setae................ 8

8. Pleonites 1 and 2 narrower than pleonites 3 – 5. Frontal lamina extended anteriorly, usually visible in dorsal view, not fusing or abutting rostrum;rostrum acute, never anteriorly dilated. Uropodal endopod lateral margin without excision;head and pereonites 1 or 2 may have horn-like processes................................................ Annina Budde-Lund, 1908

- Pleonites 1 and 2 subequal in width to pleonites 3 – 5. Frontal lamina extended anteriorly, usually visible in dorsal view, usually fusing to or abutting rostrum; rostrum truncate or anteriorly dilated. Uropodal endopod lateral margin with excision; head and pereonites 1 and 2 without horn-like processes...................................... Excirolana Richardson, 1912

9. Pleopod 1 operculate, not indurate (thickened); frontal lamina projecting visible in dorsal view..................................................................................................... Conilorpheus Stebbing, 1905

- Pleopod 1 not operculate; frontal lamina not projecting, not visible in dorsal view................................. 10

10. Pleonite 3 postero-lateral margins not expanded, not posteriorly produced; frontal lamina elongate (4.0–8.5x posterior width), posterior third entirely flat........................................................... Natatolana Bruce, 1981

- Pleonite 3 postero-lateral margins expanded, posteriorly produced; frontal lamina broad (2.4–4.0x posterior width), anteriorly flat, posteriorly with ventrally directed process (“horn”)................................... Dolicholana Bruce, 1986

11. Body size “huge”, adults 8–30 cm; pleopods with respiratory branchiae........... Bathynomus A. Milne-Edwards, 1879

- Body size “normal”, adults 3–30 mm; pleopods without respiratory branchiae.................................... 12

12. Mandible incisor narrow, less than 0.5 basal width or less (head therefore appearing proportionally narrow). Uropodal exopod lateral margin with or without prominent excision on lateral margin.......................... Neocirolana Hale, 1925

- Mandible incisor not narrow, more than 0.5 basal width (head not appearing proportionally narrow). Uropodal exopod lateral margin never with prominent excision.................................................... Cirolana Leach, 1818