Colomastix, Grube, 1861

Silvany, Liz & Senna, André R., 2019, Three new species of Colomastix Grube, 1861 (Amphipoda: Colomastigidea) from Todos-os-Santos Bay, northeastern Brazilian coast, with identification keys to Atlantic Ocean species, Zootaxa 4629 (4), pp. 519-554 : 548-549

Key to adult males of Colomastix species from the Atlantic Ocean

(Excludes C. castellata , C. denticornis , C. escobarae , C. sarae and C. simplicauda known only from females or subadult males)

1. Gnathopod 1 elongate; inner plate of maxilliped cleft......................................................... 2

- Gnathopod 1 vestigial (except for C. cornuticauda , C. halichondriae , C. irciniai and Colomastix marielle sp. nov.); inner plate of maxilliped entire................................................................................... 3

2. Gnathopod 2, palm with two processes; pereopods 3–7, propodus flexor margins with well-developed setae (usually 4); uropod 2, inner ramus longer than outer; uropod 3, inner ramus much longer than outer; telson, apical margin with two notches............................................................................................. C. fissilingua

- Gnathopod 2, palm with one process; pereopods 3–7, propodus flexor margins without setae; uropod 2, rami subequal in length; uropod 3, inner ramus slightly longer than outer; telson, apical margin smooth............................ C. bastidai

3. Pleopods, rami 4-articulate; uropod 1 apex of inner ramus with subterminal dorsal notch, rounded and bulbous or bifurcate.. ................................................................................................... 7

- Pleopods, rami not 3-articulate or outer ramus 4-articulate, inner ramus 3-articulate; uropod 1 apex of inner ramus different from above.......................................................................................... 4

4. Eyes protruding laterally; antenna 2, ventrolateral margins of peduncle articles 3–5 lacking small setae; maxilliped, basal shell extending as a ventral keel; uropod 1, rami seubequal, inner ramus lateral margins subeparallel, not expanded proximally and tapering distally; telson linguiform....................................................................... 5

- Eyes not protruding laterally; antenna 2, ventrolateral margins of peduncle articles 3–5 lined with small setae; maxilliped, basal shell not extending as a ventral keel; uropod 1, inner ramus much longer than outer ramus, lateral margins not subeparallel, expanded proximally and tapering distally; telson different from above.......................................... 6

5. Rostrum subacute; interantennal plate, anteroventral and anterodorsal angles standing forward subequally; gnathopod 1, elongate; gnathopod 2, propodus unenlarged, similar to female; pereopods, flexor margins of propodus lacking setae; pleopods, rami 3-articulate; uropods 1–3, rami with subterminal well-developed setae; uropod 1, outer ramus not expanded, inner ramus broadly expanded, with subterminal medial concavity and apex acute, lacking setae; telson strongly concave dorsally, lateral margins upturned proximally, apex sharply recurved, bearing 2 anterodorsally directed, blunt-tipped processes................................................................................................... C. cornuticauda

- Rostrum acute; interantennal plate, anteroventral angle standing slightly beyond anterodorsal; gnathopod 1 vestigial; gnathopod 2, propodus enlarged, palm tridentate; pereopods, flexor margins of propodus with 1–2 setae; pleopods, inner ramus 3-articulate, outer ramus 4-articulate; uropods 1–3, rami with subterminal well-developed setae; uropod 1, outer ramus broadly expanded, inner ramus slightly expanded, without subterminal medial concavity, apex tube-like, with some fine setae; telson subovate, convex, lateral margins not recorved, apex not anterodorsally directed, smooth..... Colomastix tubulosa sp. nov.

6. Head length subequal to first pereonite; interantennal plate, anterior margin not serrate; gnathopod 2, propodus enlarged; uropod 1, apex subacute, not rudder-shaped, with dorsal indentations; uropod 3, rami subequal in length...... C. halichondriae

- Head slightly longer than first pereonite combined with half of second pereonite; interantennal plate, anterior margin slightly serrate; gnathopod 2, propodus unenlarged; uropod 1, apex rounded, rudder-shaped, without dorsal indentations; uropod 3, inner ramus much longer than outer ramus............................................ Colomastix marielle sp. nov.

7. Head length subequal to first two pereonites combined; uropod 1, inner ramus with subterminal dorsal notch, apex rounded, slightly to strongly bulbous............................................................................. 8

- Head length subequal to first or first and a half pereonite (except for C. falcirama , C. janicea , C. tridentata and Colomastix trispinosa ); uropod 1, inner ramus without subterminal dorsal notch, apex strongly or minutely bifurcate, bifurcation branches unequal........................................................................................... 10

- Gnathopod 2, propodus, palm not excavate, tridentate; pereopods 3–7, propodus with 3–6 setae on flexor margin; uropod 1, inner ramus different from above; uropod 3, inner ramus broadly expanded; telson subovate......................... 8

9. Rostrum subacute; uropod 1, inner ramus, ventral margin smoothly concave, apex bulbous, with compound seta inserted in subterminal, dorsal notch...................................................................... C. bousfieldi

- Rostrum acute; uropod 1, ventral margin angled sharply downward distally, apex strongly bulbous, notched dorsally C. heardi

10. Gnathopod 1 elongate; uropod 1 inner ramus, apex with one branch of bifurcation upturned; uropod 2, inner ramus slightly shorter than outer.............................................................................. C. irciniae

- Gnathopod 1 vestigial; uropod 1, inner ramus, apex with branches of bifurcation different from above; uropod 2, rami subequal in length (except for C. tridentata and Colomastix iemanja sp. nov.)........................................... 11

11. Rostrum rounded; telson lateral margins smooth........................................................... 12

- Rostrum acute or subacute; telson lateral margins castellated................................................. 13

12. Head length subequal to first two pereonites combined; pereopods 3–7, propodus with 2–5 setae on flexor margin; pleopods 1–3 with elongate setae on peduncle; uropod 1, inner ramus, apex slender, dorsal branch of bifurcation twice the length of ventral branch; uropod 2, rami subequal in length; telson subtriangular.................................... C. falcirama

- Head length subequal to first and a half pereonite; pereopods 3–7, propodus lacking setae on flexor margin; pleopods 1–3 lacking setae on peduncle; uropod 1 inner ramus, apex surrounded by interlinked elongate setae, resembling a wrinkled membrane, dorsal branch of bifurcation more than twice the length of ventral branch, distally expanded and upturned, lined with distal small, stout setae, ventral branch narrow, lined with small, setae; uropod 2, inner ramus slightly shorter than outer; telson subovate......................................................................... Colomastix iemanja sp. nov.

13. Head length subequal to first and a half pereonite; rostrum subacute; antenna 1, peduncle article 1 lacking setae on dorsomedial margin; antenna 2, peduncle article 3 with distomedial elongate seta adjacent to very strong inwardly curved process; pereopods 3–7, propodus lacking setae on flexor margin; uropod 3, rami subequal in length, inner ramus not expanded...... C. camura

- Head length subequal to or slightly longer than first two pereonites combined; rostrum acute; antenna 1, peduncle article 1 with 3–5 setae on dorsomedial margin; antenna 2, peduncle article 3 distomedial process small or absent; pereopods 3–7, propodus with 2–5 setae on flexor margin; uropod 3, inner ramus longer than outer, expanded; telson distolateral margins lacking setae .................................................................................................. 14

14. Interantennal plate, anteroventral angle projecting subequally to anterodorsal angle; uropod 1, inner ramus, apex with one branch of bifurcation hooked..................................................................... C. janicea

- Interantennal plate, anteroventral angle projecting beyond anterodorsal angle; uropod 1, inner ramus, apex with both branches of bifurcation straight; telson distolateral margins lined with setae............................................. 15

15. Interantennal plate, anteroventral angle projecting slightly beyond anterodorsal angle, anteroventral margin smooth; antenna 1, peduncle article 1, dorsomedial margin with four stout setae; uropod 1, inner ramus, apex with subterminal lateral concavity........................................................................................... C. tridentata

16. Interantennal plate, anteroventral angle projecting much beyond anterodorsal angle, anteroventral margin serrate; antenna 1, peduncle article 1, dorsomedial margin with three stout setae; uropod 1, inner ramus, apex lacking subterminal lateral concavity........................................................................................ C. trispinosa