Hypodontolaimus

Key to the known and the new species of Hypodontolaimus

1 Precloacal supplements present in males...................................................................2

- Precloacal supplements absent in males.................................................................... 9

2 Body longer than 1.5 mm............................................................................... 3

- Body shorter than 1.3 mm............................................................................... 4

3 Cephalic setae much shorter (1/6–1/5 hd long), 21–28 precloacal supplements.......................... H. antarcticus

- Cephalic setae 1hd long, 9 precloacal supplements................................................. H. setosoides

4 Pharynx without distinct terminal bulb.................................................................... 5

- Pharynx with distinct terminal bulb.......................................................................6

5 Cephalic setae 2 hd long......................................................................... H. setosus

- Cephalic setae short than 1 hd long............................................................... H. abyssalis

6 19–24 precloacal supplements................................................................... H. balticus

- Precloacal supplements less than 15.......................................................................7

7 Cuticle with lateral differentiation of 2 longitudinal rows of dots, 8 precloacal supplements................. H. marleenae

- At least female cuticle with lateral differentiation of 4 longitudinal rows of dots.................................... 8

8 Male with 2, female with 4 lateral longitudinal rows of dots, gubernaculum with anterior-lateral apophysis, 7 precloacal sup- plements.................................................................................. H. dimorphus

- Both male and female with 4 lateral longitudinal rows of dots, gubernaculum without anterior-lateral apophysis, 11–15 preclo- acal supplements............................................................................ H. inaequalis

9 Cephalic setae longer than 1 h.d. long.................................................................... 10

- Cephalic setae shorter than 1 h.d......................................................................... 15

10 Labial sensilla setose, pharyngeal bulb present.............................................................11

- Labial sensilla papillose, pharyngeal bulb absent....................................................... H. colesi

11 Gubernaculum with apophysis..........................................................................12

- Gubernaculum without apophysis........................................................................ 13

12 Body length longer than 500µm, apophysis of gubernaculum hooked..................................... H. steineri

- Body length shorter than 500µm, apophysis of gubernaculum not hooked............................ H. galapagensis

13 Gubernaculum well developed, spoon-shaped, halfe the length of the spicula.................. H. schuurmansstekhoveni

- Gubernaculum reduced to a short plate, much shorter than half the length of the spicula............................. 14

14 Spicula nearly equal width throughout, distal blunt, 17 µm long........................................ H. solivagus

- Spicula tapering unevenly, distal pointed, 21µm long............................................... H. interruptus

15 Cephalic setae 2/3 h.d long............................................................................. 16

- Cephalic setae shorter than 0.5 h.d........................................................................ 19

16 Gubernaculum with apophysis.......................................................................... 17

- Gubernaculum without apophysis........................................................................18

17 Body longer than 610 µm, gubernaculum with ventral apophysis........................... H. ventrapophyses sp. nov.

- Body shorter than 470 µm, gubernaculum with dorsal apophysis........................................ H. pumilio

18 Gubernaculum distally with two teeth.............................................................. H. pilosus

- Gubernaculum distally without any tooth.......................................................... H. longiseta

19 Pharyngeal base slightly dilated, no bulb..................................................... H. obtusicaudatus

- Pharyngeal bulb well developed......................................................................... 20

20 Gubernaculum with strong dorsal apophysis................................................... H. mediterraneus

- Gubernaculum without any apophysis.................................................................... 21

21 Body longer than 900 µm, cephalic setae 6 µm, somatic setae 7–8 µm.................................... H. angelae

- Body shorter than 800µm, cephalic setae absent, somatic setae up to 30 µm............................... H. reverus