Callichirus Stimpson, 1866

Hernáez, Patricio, Miranda, Marcel S., Rio, Juliana P. P. & Pinheiro, Marcelo A. A., 2022, A new Callichirus ghost shrimp species from the southwestern Atlantic, long confounded with C. major (Say, 1818) (Decapoda: Axiidea: Callichiridae), Journal of Natural History 56 (9 - 12), pp. 533-563 : 557

Key to the species of the genus Callichirus Stimpson, 1866 ( Figures 8 , 9 , 10 )

1. Ocular peduncle with obtuse tip, not exceeding or slightly exceeding junction between first and second articles of the antennular peduncle ( Figure 8a, d, e ) ................................ 2

- Ocular peduncle with prominent distomesial projection distinctly exceeding junction between first and second articles of antennular peduncle ( Figure 8b, c, f ) ..................... 5

2. Ocular peduncle reaching to about 2/3 of the length of the first article of the antennular peduncle ( Figure 8a ). Male pleopod 2 with endopod and exopod well developed ( Figure 9b ) ........................................................................................................................ 3

- Ocular peduncle reaching the limit between the first and second articles of antennular peduncle, or a little beyond ( Figure 8d, e ). Male pleopod 2 with endopod or exopod reduced ( Figure 9d, e ) ........................................................................................................ 4

3. Male major cheliped dactylus with bifid tip ( Figure 10b ). Female major cheliped merus armed with ventral hook ( Figure 10c ) .................................... C. corruptus sp. nov.

- Male major cheliped dactylus simple ( Figure 10a ). Female major cheliped merus unarmed .............................................................................. Callichirus sp. (Caribbean Colombia)

4. Male pleopod 2 with endopod underdeveloped ( Figure 9e ) ............ C. santarosaensis

- Male pleopod 2 with exopod reduced ( Figure 9d ) ...................................... C. major s. str.

5. Antennular peduncle article 2 reaching as far as antennal peduncle article 4 ( Figure 8f ). Maxilliped 3 with tiny notch at the flexor distal angle of propodus ( Figure 9h ) ..... .................................................................................................................................................. C. seilacheri

- Antennular peduncle article 2 exceeding antennal peduncle article 4 ( Figure 8b, c ). Maxilliped 3 without notch on flexor distal margin of propodus ( Figure 9f, g ) ......... 6

6. Male major cheliped ischium unarmed ventrally ( Figure 10d ). Telson with small convexity within median emargination ( Figure 10e ) .............................................. C. garthi

- Male major cheliped ischium armed with a ventral hook ( Figure 10f ). Telson without convexity within median emargination ( Figure 10h ) ............................................................ 7

7. Male pleopod 2 with exopod reduced ( Figure 9a ). Male major cheliped merus unarmed ventrally ( Figure 10g ) .................................................................................... C. adamas

- Male pleopod 2 with exopod well developed ( Figure 9c ). Male major cheliped merus armed with ventral hook ( Figure 10f ) .................................................................. C. islagrande

Figures

Figure 8. Carapace and cephalic appendages, dorsal view. a, Callichirus corruptus sp. nov., MZUSP 41251; b, Callichirus garthi, MUAP-CD 0426/2011; c, Callichirus islagrande (courtesy of Nuno Simões); d, Callichirus major, USNM 228086; e, Callichirus santarosaensis (modified from Sakai and Türkay 2012); f, Callichirus seilacheri, MZUCR 3335–01. Scale bars: 10 mm.

Figure 9. Male pleopod 2 and third maxilliped, external surface. a, Callichirus adamas (modified from Kensley 1974); b, Callichirus corruptus sp. nov., MZUSP 41251; c, Callichirus islagrande, USNM 69362; d, Callichirus major, USNM 228086; e, Callichirus santarosaensis (modified from Sakai and Türkay 2012); f, Callichirus adamas (modified from Kensley 1974); g, Callichirus garthi, MZUC-UCCC 7311; h, Callichirus seilacheri, MZUCR 3335–01. Scale bars: a–d = 1 mm; e–h = 5 mm.

Figure 10. a, Callichirus aff. major Colombia, male major cheliped dactylus and fixed finger, lateral view, USNM 266225; b, Callichirus corruptus sp. nov., male major cheliped dactylus and fixed finger, lateral view, MZUSP 41251; c, Callichirus corruptus sp. nov., female major cheliped merus, lateral view, MZUSP 41252; d, Callichirus garthi, male major cheliped ischium, lateral view, MUAP-CD 0432–2011; e, Callichirus garthi, sixth pleomere, uropods and telson, dorsal view, MUAP-CD 0432–2011; f, Callichirus islagrande, male major cheliped merus and ischium (courtesy of Nuno Simões), lateral view; g, Callichirus adamas, male major cheliped merus and ischium (modified from Kensley 1974), lateral view; h, Callichirus islagrande, sixth pleomere, uropods and telson, dorsal view, USNM 69362. Scale bars: 10 mm.