Colomastix iemanja, Silvany & Senna, 2019

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 : 524-532

Colomastix iemanja sp. nov.

Figs (4–8)

Etymology. This species is named after Yemanjá, a divinity considered the queen of all waters in Candomblé religion, of African origins. During the slavery period, the Todos-os-Santos Bay region welcomed black people who came from Africa, bringing their beliefs and syncretism that hold strong until today in local culture.

Type locality. Marina of Itaparica Island (12°53’21.7”S, 38°41’00.9”W), Bahia state, Brazil.

Examined material. Holotype. Adult male (dissected and drawn) 2.6 mm, Marina of Itaparica Island (12°53’21.7”S, 38°41’00.9”W), Bahia state, Brazil, in unidentified sponge, 2 m depth, 29 August 2015, UERJ 91 .

Paratypes. Adult male (dissected and drawn) 2.5 mm, same data as holotype, UERJ 94. Juvenile male (dissected and drawn) 2.6 mm, same data as holotype, UERJ 124. Adult female (dissected and drawn) 2.7 mm, same data as holotype, UERJ 95; 1 adult female (dissected and drawn) 3.0 mm, same data as holotype, UERJ 96; 1 adult male (dissected), same data as holotype, UERJ 92; 1 adult male (dissected), same data as holotype, UERJ 93. 1 adult female (dissected), same data as holotype, UERJ 97. 1 juvenile male, same data as holotype, MOUFPE 18756. 2 adult male, same data as holotype, MOUFPE 18757. 12 adult females, same data as holotype, MOUFPE 18758. 3 adult males, 6 juvenile males, 1 adult female, 4 juvenile females, 7 juveniles, Dentão Rock, (12°50’02.4”S, 038°31’32.0”W), Bahia state, Brazil, in Sponge 4— Desmapsamma anchorata Carter, 1882 , 4– 6 m depth, 20 May 2017, UERJ 98. 1 adult male, 2 juvenile males, Dentão Rock, (12°50’02.4”S, 038°31’32.0”W), Bahia state, Brazil, in Sponge 3— Desmapsamma anchorata + Ircinia sp., 4–6 m depth, 20 May 2017, UERJ 102. 3 adult males, 2 juvenile males, 3 adult females and 7 juveniles, Boa Viagem Beach, (12°55’56.014”S, 38°30’53.597”W), Bahia state, Brazil, in Sponge 6— Desmapsamma anchorata , 1–3 m depth, 11 May 2017, UERJ 99. 1 adult male, 6 juvenile males, 1 adult female, 1 juvenile female and 19 juveniles, Boa Viagem Beach, (12° 55’ 56.014” S, 38° 30’ 53.597” W), Bahia state, Brazil, in Sponge 9— Callyspongia sp., 1–3 m depth, 11 May 2017, UERJ 100. 1 adult male, 3 juvenile males, 5 adult females, 1 juvenile female and 12 juveniles, Boa Viagem Beach, (12°55’56.014”S, 38° 30’53.597”W), Bahia state, Brazil, in Sponge 7— Callyspongia sp., 1–3 m depth, 11 May 2017, UERJ 101. 11 adult males, 12 juvenile males, 3 adult females, 15 juvenile female and 32 juveniles, Boa Viagem, (12°56’06.7”S, 038°30’40.2”W), Bahia state, Brazil, in Sponge 3— Callyspongia sp., 10 m depth, 21 May 2017, UERJ 104. 1 adult male, 2 juvenile males, 3 adult females, 15 juvenile female and 2 juveniles, Alvas Rocks, (12°52’22.0”S, 038°31’46.8”W), Bahia state, Brazil, in Sponge 8— Desmapsamma anchorata , 8 m depth, 21 May 2017, UERJ 103.

Diagnosis. Rostrum rounded (subacute in female and juvenile male); interantennal plate, anteroventral angle projecting subequally to anterodorsal angle (projecting slightly beyond in female and juvenile male), anterior margin straight (slightly concave in female and juvenile male); antenna 1, peduncle article 1 with two setae on dorsomedial margin; antenna 2, peduncle articles 3–5 ventrolateral margin lined with small, equally-spaced setae, peduncle article 3 with single distomedial seta and adjacent process; maxilliped inner plate completely fused, basal shall not expanded to form ventral keel; gnathopod 1 vestigial (elongate, simple in female and juvenile male); gnathopod 2, basis expanded distally, propodus enlarged, palm tridentate; gnathopod 2 of female, insertion of dactylus terminal, dactylus apex pleated; pereopods 3–7, propodus without setae on flexor margin; pleopod 1–3, rami 4-articulate; uropod 1, inner ramus tapering distally, curved dorsally, apex unequally bifurcate, dorsal branch of bifurcation twice as long as ventral, distally expanded and upturned, ventral branch narrow, apex surrounded by interlinked elongate setae, resembling a wrinkled membrane; uropod 3, inner ramus expanded, slightly shorter than outer ramus (subequal to outer ramus in female and juvenile male); telson dorsally convex, subovate (subtriangular in female and juvenile male).

Description. Based on holotype adult male, 3.4 mm, UERJ 91; adult male, 2.5 mm, UERJ 94; adult male, 3.0 mm, UERJ 92 and adult male, UERJ 93.

Head. Head as long as deep, subequal in length to pereonite 1 and half of pereonite 2, approximately 1/8 length of body; rostrum rounded; interantennal plate with anterodorsal and anteroventral angles extending forward subequally, anterodorsal angle rounded in lateral view, anteroventral angle subacute in lateral view, anterior margin straight, without serrations or ventral teeth; eyes somewhat protruding laterally in dorsal view, consisting of 15–22 ommatidia, separation of ommatidia somewhat variable. Antennae 1–2 subequal in length, approximately 1/6 length of body. Antenna 1, ratio of peduncle articles 1–3 1:0.8:0.6; peduncle article 1, dorsomedial margin with 2 small setae, ventromedial margin with 4 robust setae; peduncle article 2, with no setae on dorsomedial margin and ventromedial margin with 2 distal well-developed stout setae; peduncle article 3 with 1 distal well-developed seta on ventromedial margin, and 1 small seta on lateral surface; well-developed setae on peduncle articles 2–3 with apical accessory seta; flagellum short, 1-articulate. Antenna 2, ventrolateral margins of peduncle articles 3–5 lined with small, equally-spaced setae; peduncle article 3 with 1 distomedial well-developed stout seta adjacent to small process, apex of seta usually extending apex of process; peduncle article 4, dorsomedial margin with 3 subequally spaced stout setae; peduncle article 5 medial surface with two pairs of setae, distalmost seta poorly developed, ventromedial margin with 3 poorly developed distal setae; flagellum sort, 3-articulate with few relatively short setae. Mandibles and maxillae greatly reduced. Maxilliped, basal shell rounded distally, not expended to form ventral keel; inner plate completely fused, subovate; outer plates reduced, with a distomedial somewhat wrinkled projection, left outer plate more reduced than right; palp articles, 1–2 distomedial margin with 1 stout seta; palp article 3, medial surface with many fine setae, 2 stout, long setae with a plumose apex, outer margin with 1 long, stout seta at joint with dactylus.

Pereon. Pereon corresponding approximately to 2/3 length of body, pereonites 1–4 slightly increasing in length, pereonites 5–7 slightly decreasing in length. Coxae 1–4 subequal in depth, slightly increasing in size, ventral margins nearly straight to slightly convex, produced anteriorly, with small anteroventral cusp, and posteroventral angle broadly rounded; coxae 5–7 slightly shallower, decreasing in size, ventral margins convex, anteroventral and posteroventral angles rounded. Coxal gills 2–5 gradually increasing in size, ranging from 1/3 length of basis on gnathopod 2 to 3/4 length of basis on peraeopod 5; coxal gill 6 slightly smaller than coxal gill 5. Gnathopod 1 vestigial, approximately 1/2 of gnathopod 2, with a heavily wrinkled surface; basis approximately same length as all the other articles combined; all other articles subequal in length; propodus slightly shorter than carpus, rounded, palm undifferentiated, distally cleft, without setae; dactylus undifferentiated. Gnathopod 2, basis distally expanded; merus with three elongate distoventral setae; carpus approximately 1/3 length of propodus, with stout distoventral setae, distalmost seta elongate and minutely pectinate; propodus enlarged, approximately 1/2 length of gnathopod 2, ventral and dorsomedial margins lined with elongate, stout setae, medial surface covered with much smaller, fine se- tae, palm with three subequal, relatively evenly spaced triangular processes, proximalmost two processes anteriorly directed, distalmost process ventrally directed; dactylus stout, terminal, extending posteriorly approximately 1/3 length of propodus and 2/3 length of palm. Pereopods 3–7, basis somewhat expanded distally; merus anterodistal angle with a small seta; propodus anterior margin without setae.

Pleon. Corresponding approximately to 1/4 length of body. Pleopods 1–3 peduncular articles robust, subequal in width and length, each with pair of coupling setae on distomedial margin, each one with medial margin undu- late; all rami 4-articulate, each article with pair of long, plumose setae, inner ramus subequal to first 3 articles of outer ramus in length, article 1 with 1 short, plumose setae on medial margin. Urosome about 1/10 length of body. Urosomite 1 slightly longer than fused urosomes 2+3; length:depth ratios of urosome 1 and of urosomites 2+3 approximately 1:1. Uropod 1, peduncle slightly shorter than inner ramus in length, with only one stout, long seta on dorsodistal inner margin; inner ramus lanceolate, twice as long as outer, curved dorsally, tapering distally, apex unequally bifurcate, dorsal branch of bifurcation twice as long as ventral, distally expanded and upturned, lined with distal small, stout setae, ventral branch narrow, with line of small setae on medial surface, apex surrounded by interlinlinked elongate setae, resembling a wrinkled membrane; outer ramus lanceolate, dorsal margins lined with small setae. Uropod 2 peduncle subequal to outer ramus in length, distal half of dorsal outer margin lined with small subequal setae; rami lanceolate, outer ramus slightly longer than inner, dorsal inner and outer margins setose, setae on outer margin larger than those on inner; inner ramus, dorsal inner and outer margins setose, setae on inner margin larger than those on outer margin and both margins of outer ramus. Uropod 3, peduncle stout, slightly shorter than rami, with no setae; outer ramus slightly longer than inner ramus, slender, dorsal outer and inner margins lined with very small setae; inner ramus broadly expanded medially, ventral margin and dorsal outer margin lined with very small setae, dorsal inner margin lined with stout setae, first half of setae gradually increasing in size, second half of setae gradually decreasing in size. Telson, convex dorsally, subovate, slightly longer than half uropod 3 in length; distolateral margins lined with small, fine setae; apex somewhat truncate, with pair of small, stout middorsal setae.

Sexual dimorphic characters (based on paratype adult female, 2.7 mm, UERJ 95; adult female, 3.0 mm, UERJ 96 and adult female, UERJ 97).

Head. Head width 1.5 × length, slightly longer than first pereonite in length (much smaller than in male); rostrum subacute; interantennal plate with anteroventral angle extending slightly beyond anterodorsal angle, anterior margin slightly concave, anteroventral angled acute in ventral view, anterodorsal and anteroventral angles acute in lateral view. Antennae 1–2, setae stouter and larger than in male. Antenna 1, articles 2–3 without setae with accessory seta. Antennae 2, peduncle article 3 with larger distomedial seta and adjacent process than in male, apex of seta usually extending beyond apex of process; article 5 with only two medial setae instead of two pairs of setae in male. Mandibules and maxillae not reduced, typical of genus. Maxilliped, wright outer plate more reduced than the left, as opposite to male, and palp articles 3–4 with small, stout, rounded setae, and no plumose setae.

Pereon. Gnathopod 1, elongate, simple; propodus with 6 elongate, apically curved, simple terminal setae; dactylus slender, apex spatulate, laminar. Gnathopod 2, basis slightly expanded distally; carpus with many fine setae on medial surface, additionally to long, stout setae on distoventral margin, also present in male; carpus and propodus somewhat enlarged; propodus slightly longer than carpus, lacking palmar process, with stout long setae along dorsal and ventral margins, and fine smaller setae on medial surface; dactylus slender, approximately 3/4 length of propodus, apex pleated, subtruncate. Oostegites narrowly subovate, with 15–19 marginal setae, apex of setae curled. Oostegite 2, approximately 1/3 longer than basis of gnathopod 2, length:width ratio 3:1.

Pleon corresponds to 1/5 length of body. Urosome corresponds to 1/8 length of body. Uropod 1, peduncle slightly longer than inner ramus, with line of small setae on dorsal inner and outer margins; rami lanceolate, dorsal inner and outer margins lined with setae; inner ramus slightly longer than outer; setae on dorsal inner margin of outer and inner rami stouter than others, first half of setae gradually increasing in size, second half of setae gradually decreasing in size. Uropod 2, peduncle slightly longer than inner ramus, with line of small setae on dorsal inner and outer margins; rami lanceolate, dorsal inner and outer margins lined with setae; inner ramus longer than outer, setae on dorsal inner margin stouter than others, first half of setae gradually increasing in size, second half of setae gradually decreasing in size; outer ramus, ventral margin also lined with small setae. Uropod 3, peduncle smaller than rami, ventral and dorsal inner margin lined with setae; rami subequal in length, dorsal outer and inner margin lined with setae; inner ramus, slightly expanded proximally setae on dorsal inner margin stouter than others, first half of setae gradually increasing in size, second half of setae gradually decreasing in size. Telson subtriangular, narrower than in male.

Differences duo to developmental stage (based on paratype juvenile male, 2.6 mm, UERJ 124)

Head. Head slightly longer than first pereonite in length (much smaller than in adult male), approximately 1/9 length of body; rostrum subacute (rounded in adult male); interantennal plate with anteroventral angle extending slightly beyond anterodorsal, anterodorsal and anteroventral angles subacute in lateral view (acute in adult male), anterior margin slightly concave (straight in adult male), and minutely serrate. Antenna 1, ratio of peduncle articles 1–3 1:1:0.6; marginal setae stouter than in adult male. Antenna 2, setae stouter than in adult male. Mandibles and maxillae unreduced, typical of genus.

Pereon. Gnathopod 1, elongate, simple; propodus with 5 elongate, apically curved, simple terminal setae; dactylus slender, apex spatulate, laminar. Gnathopod 2, all articles less robust than in mature male, especially propodus and dactylus; basis expanded distally, but less than in adult male; merus with 2 well-developed setae on distoventral margin; carpus little more than 1/2 length of propodus, distoventral margin with elongate, well-developed, minutely pectinate setae; propodus enlarged (but much less than in adult male), little more than 1/4 length of gnathopod 2, ventromedial margin lined with elongate, well-developed, minutely pectinate setae, ventromedial surface with much smaller, fine setae, distodorsal surface with well-developed setae, usually set in patches, distalmoust setae longer, palm lacking processes; dactylus terminal, extending posteriorly little less than 1/2 length of propodus, distoventral margin lined with minute setae, apex pleated.

Urosome. Uropod 1, peduncle slightly shorter than inner ramus, all margins lacking setae; outer ramus lanceolate, shorter than inner ramus (much sorter in adult male); inner ramus expanded, apex not highly modified, acutely upturned, dorsal inner and outer margins lined with setae, setae on outer margin much smaller, setae on inner margin larger at apex. Uropods 3, peduncle much shorter than rami (slightly shorter in adult male); rami subequal. Uropod 2, peduncle slightly shorter than inner ramus; inner ramus lanceolate. Telson, subtriangular (narrower than in adult male).

Variation. The number of setae of the antennae can vary, although the pattern of setation is the same. Although the inner ramus of uropods 3 of adult male is shorter than outer ramus, the rami can appear subequal in length, or inner ramus can even appear slightly longer depending on the position it is observed. The number of propodal setae on dorsomedial margin of female gnathopod 2 can vary, but usually follows a pattern of patches of 4, 3, 2 and 1 setae, from anterior to posterior region (this variation is shown in Fig. 8 ).

Adult body length. 2.2 mm– 3.7 mm.

Host. Desmapsamma anchorata Carter, 1882 , Callyspongia sp., D. anchorata + Ircinia sp.

Distribution. This species was found at Marina of Itaparica Island (12°53’21.7”S, 38°41’00.9”W), Dentão Rock (12°50’02.4”S, 038°31’32.0”W), Boa Viagem Beach (12°55’56.014”S, 38°30’53.597”W) and Alvas Rocks (12°52’22.0”S, 038°31’46.8”W), all localities from the TSB, state of Bahia.

Remarks. Colomastix iemanja sp. nov. can be distinguish from all other known species in the genus especially by the morphology of the male apex of inner ramus of uropod 1. Besides, the female of Colomastix iemanja sp. nov., along with Colomastix tubulosa sp. nov. are the only Atlantic species to have a pleated apex on dactylus of gnathopod 2. However, this structure is subtruncate in the former and acute in the latter. This character is shared only with five other species, C. plumosa , from Madagascar, C. semiplumosa , C. azumai , C. littoralis , all from Japan, and C. thomasi from Australia. Colomastix iemanja sp. nov. can be distinguished from the first two of these species by the lack of any densely setose rami on uropods 2 or 3, and from the last three by the presence of small setae on distolateral margins of telson. In addition, the only other species to have simple terminal setae (instead of pectinate setae) on propodus of female gnathopod 2 in the Atlantic is C. halichondriae . However, Colomastix iemanja sp. nov. can be distinguished from this species by different morphologies of the antennae, the lack of ventral keel on maxilliped, and pleopods 1–3 rami 4-articulate, instead of outer ramus 4-articulate and inner ramus 3-articulate.

Colomastix iemanja sp. nov. does not seem to be very similar to any other Atlantic species. However, it has some of the characters most common in the Atlantic, such as antenna 2, lateral margins of articles 3–5 with line of small setae; maxilliped without ventral keel; gnathopod 1 of adult male vestigial; tridentate palm of gnathopod 2; pleopods rami 4-articulate; and telson subovate in adult male and subtriangular in female. Also, in spite being very different, the apex of inner ramus of uropod 1 of Colomastix iemanja sp. nov. appears to be more similar to this character in C. bousfieldi . Both have the apex of inner ramus of uropod 1 setose, and with two asymmetric branches. However, the morphology of the branches are very different between the two spcies. In C. bousfieldi the apex has a subterminal dorsal notch and plumose setae, while in Colomastix iemanja sp. nov. the apex is bifurcate, and the setae are interlinked, resembling a wrinkled membrane.

Additionally to the characters cited above for the Atlantic species, Colomastix iemanja sp. nov. shares with the Gulf of Mexico species, C. bousfieldi , antenna 1 with two setae on dorsomedial margin of peduncle article 1; antenna 2 with one distomedial setae adjacent to small process on peduncle article 3; and coxal gills 1–5 increasing in size, and coxa 6 slightly smaller than coxa 5. Colomastix iemanja sp. nov. can be distinguished from C. bousfieldi by the lack of setae on flexor margin of pereopod propodi; lack of elongate setae on distomedial margin of pleopodi; lack of setose inner ramus of uropod 3 of female; lateral margins of telson lined with small setae (lacking setae in C. bousfieldi ); female gnathopod 1, proprodus with distal setae simple instead of compound; interantennal plate of male with anterior margin straight instead of concave; coxae 2–4 less projected anteriorly and with anteroventral angle less rounded; coxae 5–7 less projected posteriorly.

The differences found between adult and juvenile males of Colomastix iemanja sp. nov. are similar to those found in Colomastix tubulosa sp. nov. This developmental differences have been sited by LeCroy (1995) as common amongst Colomastix . However, all of them occurring at the same time in the same species, have only been fully illustrated and described by Ariyama (2005), for C. azumai and C. litorallis . In both of these species, as well in Colomastix iemanja sp. nov. and Colomastix tubulosa sp. nov. the following developmental changes occur: (1) reduction of gnathopod 1 from simple, elongate in immature male, to vestigial in adult male; (2) enlargement of the propodus, development of palmar processes and disappearance of pleated apex of gnathopod 2, in adult male; (3) fully differentiation of the adult morphology of the apex of inner ramus of uropod 1; (4) and expansion of inner ramus of uropod 3. Only for Colomastix iemanja sp. nov. and Colomastix tubulosa sp. nov. there was also an increase in head length:width ratio (not illustrated or described for the other two previously known species) and the expansion of inner ramus of uropod 2.

Colomastix iemanja sp. nov. can be differenciated from C. azumai and C. litorallis by the tridentate palm of gnathopod 2 (with two processes in C. azumai and C. litorallis ); lack of setae on flexor margin of pereopods 3–7 propodi (with 4–5 setae in C. azumai and C. litorallis ); and by the morphology of the apex of inner ramus of uropod 1. Colomastix iemanja sp. nov. can be differenciated from Colomastix tubulosa sp. nov. by the ommatidia not set in pairs in Colomastix iemanja sp. nov., while set in pairs in Colomastix tubulosa sp. nov.; antenna 1, flagellum article 1 with two setae on dorsomedial margin (3 setae on Colomastix tubulosa sp. nov.); inner ramus of pleopods 1–3 with 3 articles (with 4 articles in Colomastix tubulosa sp. nov.); rami of uropods 1–3 lacking well-developed distomedial seta (setae present in Colomastix tubulosa sp. nov.); and uropod 3, inner ramus slightly shorter than outer ramus (inner ramus longer than outer ramus in Colomastix tubulosa sp. nov.).

Additional comment. The male eyes shown in the illustration of H, A 1–2 ( Fig. 5 ) were dotted, because the eyes of the examined specimen were damaged during the dissection process.

Figures

FIGURE 5. Colomastix iemanja sp. nov. Holotype, adult male, 2.6 mm, Marine Itaparica Island, (12°53’21.7”S, 38°41’00.9”W), Bahia state, Brazil, UERJ 91. Paratypes: juvenile male (dissected and drawn) 2.6 mm, same data as holotype, UERJ 124. Adult female, 2.7 mm, same data as holotype, UERJ 95. Adult female, 3.0 mm, only fMp (ventral), same data as holotype, UERJ 96. Image Hd, A1–2, eyes damaged during dissection Scale bars: 0.5 mm for Hd, A1–2 and jHd, A1–2; 0.2 mm for fHd (dorsal) and Gn1; 0.1 mm for Mp (lateral and ventral), jGn1 and fMp (lateral and ventral); 0.05 mm for fMd, fMx1–2.

FIGURE 8. Colomastix iemanja sp. nov. Adult female, 2.7 mm, Marine Itaparica Island, (12°53’21.7”S, 38°41’00.9”W), Bahia state, Brazil, UERJ 95. Scale bar: 0.2 mm for fHd, A1–2, fGn2 and fGn1; 0.1 mm for fUr1–3; 0.05 mm for f T (dorsal).