Mastigodiaptomus, Light, 1939

Sua´Rez-Morales, E. & Elías-Gutiérrez, M., 2000, Two new Mastigodiaptomus (Copepoda, Diaptomidae) from southeastern Mexico, with a key for the identi ® cation of the known species of the genus, Journal of Natural History 34 (5), pp. 693-708 : 706-707

Key to species of Mastigodiaptomus

Males

1a Spine on segment 16 strongly developed. Second basipod of right fi fth leg with a proximal subrectangular projection and two small bulb-like processes along inner margin.................... M. reidae

1b Spine on segment 16 absent or reduced, processes on second basipod not as described above.................... 2

2a Large (over 2,2 mm, excluding furcal rami)........... 3

2b Small or medium-sized (less than 2.0 mm length, excluding furcal rami).... 4

3a First exopod of right fi fth leg with a transverse ridge; antepenultimate segment of right antennule with fang-like process.......... M. purpureus

3b First exopod of right fi fth leg with tongue-like projection. antepenultimate segment of right antennule with rounded, knob-like process....... M. maya

4a Second exopod of right fi fth leg with lateral spine long, at least 75% of length of its segment..................... 5

4b Second exopod of right fi fth leg with lateral spine short: less than half the length of segment..................... 7

5a Second basipod of right fi fth leg with posterior butter fl y-like sclerotization on inner margin................. M. albuquerquensis

5b Same structure without such sclerotization............ 6

6a Left fi fth leg exopod with distal process smooth, right endopod not reaching distal margin of fi rst endopodal segment............ M. nesus

6b Left fi fth leg exopod with distalmost process denticulate, right endopod reaching the distal margin of fi rst endopodal segment......... M. texensis

7a Second exopod of right fi fth leg with a semicircular transverse lamella on proximal posterior surface and a fi ne longitudinal`y’ shaped longitudinal ridge. Lateral spine inserted on second third of segment......... M. montezumae

7b Second exopod of right fi fth leg without a lamella or ridges on proximal posterior surface. Lateral spine subterminal.......... M. amatitlanensis

Females

1a Genital double somite asymmetrical, with lateral protuberances outwards, on one or both sides.................... 2

1b Genital double somite symmetrical, with both margins nearly straight.... 6

2a Fifth leg with one-segmented endopodites............ 3

2b Fifth leg with two-segmented endopodites............ 4

3a Second urosomite with posterodistal protrusion...... M. amatitlanensis

3b Second urosomite with straight posterior margins...... M. montezumae

4a Antennules long, reaching beyond furcal setae......... M. nesus

4b Antennules short, reaching at most midlength of caudal rami....... 5

5a Genital double somite elongated, 2.25 times longer than wide, lateral spines weakly developed................... M. reidae

5b Genital double somite almost square, nearly as wide as long, lateral spines strong..................... M. albuquerquensis

6a Large, more than 2.2 mm long excluding furcae.......... 7

6b Small or medium-sized, never reaching 2.0 mm........ M. texensis

7a Sensilla on fi rst basipod of fi fth leg small and short, length/width ratio less than 1.2....................... M. maya

7b Sensilla on fi rst basipod of fi fth leg, large and long, length/width ratio over 2.0........................ M. purpureus