Colomastix marielle, 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 : 532-540

Colomastix marielle sp. nov.

Figs (9–12)

Etymology. This species is named in honor of Marielle Francisco da Silva, known as Marielle Franco, sociologist, human rights activist, feminist and LGBT advocate, councilwoman of Rio de Janeiro city, elected to the 2017–2020 Legislature. A black woman, mother, born and raised in the favela complex of Maré, she was a fervent critic of police brutality in the slums and peripheries of the city. Marielle Franco was murdered, shot to death on March 14, 2018.

Type locality. Porto da Barra Beach (13°’14.77”S 38°32’1.115”W), Bahia state, Brazil.

Examined material. Holotype. Adult female (dissected and drawn) 3.6 mm, Porto da Barra Beach (13°0’14.778”S, 38°32’1.115”W), Bahia state, Brazil, unidentified sponge, 2 m depth, 04 August 2011, UERJ 112 .

Paratypes. Adult female (dissected and drawn) 3.4 mm, same data as holotype, UERJ 113 . Adult female (drawn) 2.8 mm, same data as holotype, UERJ 114 . 3 adult females and 6 juvenile females, same data as holotype, MOUFPE 18762 . Adult female (dissected) 3.0 mm, Boa Viagem, (12°56’06.7”S, 038°30’40.2”W), Bahia state, Brazil, in sponge 1— Callyspongia sp., 10 m depth, 21 May 2017, UERJ 115 . 3 adult female, 6 juvenile females, Boa Viagem, (12°56’06.7”S, 038°30’40.2”W), Bahia state, Brazil, in sponge 1— Callyspongia sp., 10 m depth, 21 May 2017, UERJ 116 . Adult male (dissected and drawn), 1.8 mm, Dentão Rock, (12°50’02.4”S, 038°31’32.0”W), Bahia state, Brazil, in sponge 3— Callyspongia sp., 4–6 m depth, 21 May 2017, UERJ 117 . Adult male (dissected and drawn), 1.8 mm, Dentão Rock, (12°50’02.4”S, 038°31’ 32.0”W), Bahia state, Brazil, in sponge 3— Callyspongia sp., 4–6 m depth, 21 May 2017, UERJ 118 . 1 juvenile female, Dentão Rock, (12°50’02.4”S, 038°31’32.0”W), Bahia state, Brazil, in sponge 3 – Callyspongia sp., 4–6 m depth, 21 May 2017, UERJ 119 . 3 adult females, 7 juvenile females, Boa Viagem, (12°56’06.7”S, 038°30’40.2”W), Bahia state, Brazil, in sponge 2— Callyspongia sp., 10 m depth, 21 May 2017, UERJ 120 . 1 adult female, 3 juvenile females, 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 121 . 1 adult female, 1 juvenile female, Boa Viagem, (12°56’06.7”S, 038°30’40.2”W), Bahia state, Brazil, in sponge 5— Callyspongia sp., 10 m depth, 21 May 2017, UERJ 122 . 2 adult females, 3 juvenile females, Boa Viagem beach, (12°55’56.014”S, 38°30’53.597”W), Bahia state, Brazil, in sponge 8— Callyspongia sp., 2 m depth, 11 May 2017, UERJ 123 . 2 adult females and 1 juvenile female, Porto da Barra Beach (13°0’14.778”S, 38°32’1.115”W), Bahia state, Brazil, in Callyspongia sp., 2 m depth, 11 March 2016, MOUFPE 18763 . 2 adult females and 3 juvenile females, Porto da Barra Beach (13°0’14.778”S, 38°32’1.115”W), Bahia state, Brazil, in Callyspongia sp., 2 m depth, 24 April 2015, MOUFPE 18764 .

Diagnosis. Rostrum acute, slightly upturned (straight in male); interantennal plate, anteroventral angle projecting far beyond anterodorsal angle, anterior margin strongly serrate (weakly serrate in male), with single ventral tooth (male lacking tooth); antenna 1, peduncle article 1, dorsomedial margin with 4 acute spines and 1 seta adjacent to spine (male with four setae); antenna 2, peduncle articles 3–5 lacking line of small setae on ventrolateral margins; maxilliped, inner plate completely fused, subtriangular, basal shell projecting to form ventral keel, rounded distally; gnathopod 1 elongate, simple; gnathopod 2 of female, insertion of datylus subterminal; gnathopod 2 of male, basis not expanded distally, propodus not greatly enlarged, palm with three weak, acute processes; pereopods 3–7, articles elongate, propodus with 0–1 proximal seta on flexor margin, dactylus nail present; pereopod 5, carpus elongate (not elongate in male); pleopods 1–3, outer ramus 4-articulate, inner ramus 3-articulate; urosomite 1 elongate (not elongate in male); uropods 1 and 3 extending far beyond uropod 2 (extending subequally in male); uropod 1 of male, inner ramus slightly longer than outer, not expanded proximally, margins subparallel, apex rudder-shaped, with some membrane lint at the base of the apex; uropod 3, inner ramus much longer than outer (slightly longer in male); telson linguiform, flat dorsally.

Description. Based on holotype female, 3.6 mm, UERJ 112, and paratypes: female, 3.4 mm, UERJ 113, female, 2.8 mm, UERJ 114 and female, 3.0 mm, UERJ 115.

Head. Head about 1.8 × wider than long, subequal in length to the first pereonite; rostrum, slightly upturned, acute, distolateral margins minutely serrate; interantennal plate, anteroventral angle acute in ventral and lateral view, projecting far beyond anterodorsal angle, anterior margin strongly serrate, with one acute ventral tooth; eyes protruding laterally in dorsal view, consisting in 12–17 ommatidia, separation of ommatidia somewhat variable. Antennae 1–2 subequal in length, little more than 1/4 length of body. Antenna 1, ratio of peduncle articles 1–3 1:1:0.6; peduncle article 1, dorsomedial margin with 4 acute spines, distalmost spine adjacent to apical acute spine, and 1 seta adjacent to second proximalmost spine, ventromedial margin with 4 acute spines, 4 setae and apical acute process, ventrolateral and dorsolateral margins with apical acute small process; peduncle article 2, ventromedial margin somewhat irregular, with 4 stout setae, 2 acute distal processes, and one distal seta on medial surface; peduncle article 3, ventromedial margin with 5 stout setae, and 1 acute, downwardly projected, apical process; flagellum short, 2-articulate, article 1 with distodorsal acute spine. Antenna 2, peduncle article 3, dorsolateral margin with one acute, strong process in the medial region, and 4 distal, acute precesses, medioventral margin with 2 well-developed, stout setae next to a broad distal process, apex of setae extending far beyond apex of process, distalmost seta smaller than the other; peduncle article 4, dorsolateral margin with 5 very weak, acute spines, and 1 apical, acute process, dorsomedial mergin with 5 well-developed stout setae and 2 acute, apical processes; peduncle article 5, ventromedial margin with 6 stout setae, and 1 acute, projected downwards, apical process; flagellum short, 3-articulate. Mandibles and maxillae unreduced, typical of genus. Maxilliped, basal shell rounded distally, projected to form ventral keel, with a anteroventral reentrance; inner plate completely fused, subtriangular; outer plates unreduced, with distal stout seta; palp article 3, medial surface with many fine setae, 2 stout, long setae, outer margin with 1 stout, long seta at joint with dactylus.

Pereon. About 2/3 length of body; pereonites 1–5 slightly increasing in length; pereonites 6–7 subequal in length. Coxae 1–4 subequal in depth, slightly increasing in size, ventral margins nearly straight continuously, produced anteriorly with acute anteroventral angle, slightly produced posteriorly, with rounded posteroventral angle, posterior margin with medial reentrance; coxa 1, anterior margin deeply concave; coxa 4, anteroventral angle strongly acute; coxa 5, much longer than others, anterior margin straight, anteroventral angle acute, produced and rounded posteriorly, without posterior reentrance; coxae 6–7 shallower, decreasing in size, ventral margins convex, anteroventral and posteroventral angles rounded. Coxal gills 2–6 subequal in length, ranging from 1/3 length of basis on gnathopod 2 a little more than 1/3 length of basis on peraeopod 5. Gnathopod 1, elongate, simple; propodus with 4 elongate, apically curved, plumose terminal setae; dactylus slender, apex spatulate, laminar. Gnathopod 2, basis not expanded distally; merus with 1 elongate distoventral seta; carpus and propodus somewhat enlarged; carpus slightly longer than propodus,ventral margin irregular, with many elongate, stout, pectinate setae, usually set in patches of three; propodus not greatly enlarged, palm irregular, with many elongate, stout, pectinate setae, usually set in patches of three, medial surface with proximal, fine setae, dorsal margin with 4 elongate stout setae, anterodorsal margin overhanging insertion of dactylus (insertion subterminal), bearing 6 long setae; dactylus very slender, spine-like, slightly curved, less than half length of propodus. Pereopods 3–7, basis not expanded distally; merus anterodistal angle with a very small seta; propodus flexor margin with 1–0 seta; dactylus, nail present; pereopod 5, carpus very elongate, propodus somewhat elongate. Oostegites narrowly subovate, with 14–26 elongate marginal setae, apically curled; oostegite 2 approximately 1.5 × longer than basis of gnathopod 2 more than 7 × longer than wide.

Pleon. A little more than 1/3 length of body. Pleopods 1–3, peduncle robust, elongate, subequal in width, each with pair of coupling setae on distomedial margin and without simple setae on anteromedial surface; pleopods 1–2 subequal in length, approximately 1/4 longer than pleopod 3; outer ramus 4-articulate, articles 1–2 with 0–1 (usually 0) plumose setae, each of articles 3–4 with pair of elongate, plumose setae; inner ramus shorter than outer, 3-articulate, each article with pair of elongate, plumose setae, article 1 lacking short, plumose setae on medial margin. Urosome elongate, about little more than 1/6 length of body, usually downwardly directed. Urosomite 1 much longer than urosomes 2+3 combined; length:depth ratio of urosome 1 and of urosomes 2+3 approximately 1.5:1. Uropod 1, peduncle slightly longer than outer ramus, dorsal outer and inner margins lined with setae; rami lanceolate, dorsal outer and inner margins lined with setae, setae on dorsal inner margin of inner ramus larger than others, outer ramus longer than inner ramus. Uropod 2, peduncle much longer than rami, ventral and dorsal inner margins lined with setae; rami lanceolate, subequal in length dorsal outer and inner margins lined with setae, apical setae on inner ramus larger than others. Uropod 3, peduncle little more than 1/2 length of inner ramus, without setae; inner ramus curved dorsally, expanded proximally, tapering to slender subacute apex, dorsal inner margin lined with setae; outer ramus little more than 1/2 inner ramus in length, lanceolate, dorsal outer and inner margins lined with setae. Uropods 2–3, setae on inner margin of inner ramus larger than those on outer margin and on both margins of outer ramus. Rami of uropod l and uropod 3 extending well beyond those of uropod 2, especially inner ramus of uropod 3; uropod 2 approximately 3/4 length of uropod 1. Telson flat dorsally, linguiform, extending little less than 1/2 length of uropod 3; lateral margins subparallel, distal margins lined with setae; pair of small setae located dorsolaterally on each side approximately 2/3 distance between base and apex; apex rounded and somewhat truncate, with pair of middorsal, stout setae.

Sexual dimorphic characters (based on paratypes: male, 1.8 mm, UERJ 117 and male, 1.8 mm, UERJ 118)

Head. Head about 1.3 × longer than wider, subequal in length to first pereonite and half of second peronite combined; rostrum, not slightly upturned, distolateral margins not minutely serrate; interantennal plate, anteroventral angle projecting beyond anterodorsal angle, but much less than in female, anterior margin minutely serrate, without acute ventral tooth; eyes, separation of ommatidia usually more closely set together than in female.

Pereon. Coxae 1–7 length:width ratio smaller than in female; coxae 2–5 anteroventral angle not acute; coxae 1 and 4, posterior margin without medial reentrance, coxae 2–3 medial reentrance much weaker. Gnathopod 2, basis somewhat expanded distally; merus, distoventral margin with 3 elongate, well-developed setae, and a few fine setae; carpus almost as large as propodus, distoventral surface with some fine setae, ventral and distoventral margins with elongate, well-developed, minutely pectinate setae, proximalmost setae set in three pairs; propodus not greatly enlarged, but latger than in female, approximately 1/4 length of gnathopod 2, ventral and distal margins lined with elongate, well-developed setae, sometimes set in pairs, ventromedial surface with proximal small, fine setae, dorsomedial surface with distal small fine setae, and two proximal elongate, well-developed setae, palm processes very weak, in lateral view only three acute processes visible, two distalmost closer to each other, proximalmost process next to small, rectangular medial process, and on dorsomedial margin one broad distal process projected forward towards dactylus; dactylus stout, terminal, extending posteriorly little more than half the length of propodus and all length of palm. Pereopod 5, carpus not elongate.

Pleon. Urosome about 1/4 length of body, urosomite 1 not elongate. Uropod 1 asymetric; right uropod 1, inner ramus slightly longer than outer, not expanded proximally, margins subparallel, apex modified, somewhat expanded, rudder-shaped, with a shallow depression at the base and membrane lints similar to elongate setae emerging from distal portion of depression, medial region of the apex thin, somewhat membranous, borders of the apex thick; left uropod 1 similar to right uropod 1, but in the apex of the inner ramus, the rudder-shaped structure appears somewhat atrophied, with lateral margins narrower, and ending more acutely. Uropod 2, similar to female, but peduncle is smaller than rami (peduncle much longer than rami in female). Uropod 3, similar to female, but inner ramus not so much longer than outer ramus, and less expanded at the base. Telson, apex less truncate than in female.

Variation. The anterior margin of the ocular lobe can be rounded to subacute (variation shown in Fig. 10 , illustrations fHd, A1–2 medial and fHd, A1–2 lateral). Serrations on the anterior margin of the interantennal plate can be less projected forward, forming a straighter line of serrations than occur in the holotype. The three spines on dorsomedial margin of antenna 1, article 1, can have a seta adjacent to one, two or all of them. Antenna 2, peduncle article 3 can have one additional proximal, stout setae on ventromedial margin, and serrations on dorsolateral margins of peduncle 1–3 can vary, as shown in Fig. 10 , illustrations fHd, A1–2 medial and fHd, A1–2 lateral. In some specimens, the nail of dactylus may not be completely developed, giving the impression they lack nail. In small juvenile individuals, the elongation of carpus of pereopod 5 can be less perceptible, but its format is more slender than carpus of other pereopods. Also in juveniles, serrations of the antennae and the interantennal plate are weaker.

Adult body length. 1.8 mm– 3.6 mm.

Host. Callyspongia sp.

Distribution. This species was found at Porto da Barra Beach (13° 0’ 14.778” S, 38° 32’ 1.115” W), Boa Viagem (12° 56’ 06.7” S, 038° 30’ 40.2” W) and Dentão Rock (12° 50’ 02.4” S, 038° 31’ 32.0” W), all localities from the TSB, state of Bahia.

Remarks. Females of Colomastix marielle sp. nov. are very similar to females of two other known species, C. denticornis and C. halichondriae , both from North Atlantic. Together, these three species seems to form a very distinctive group in the genus, so much so that LeCroy (1995) suggested that the two previously known species, could actually form a subgeneric group from the Gulf of Mexico, called by her the “ halichondriae group”. This group would also include a single male called by the author only of Colomastix sp., and suggested as the possible male of C. denticornis ; however, it was too damaged to know for sure. No tests were made to validate the existence of this group, and a more extencive study on the world Colomastix fauna is still needed. However, Colomastix marielle sp. nov. and species from the “ halichondriae ” group shares a number of characters, including features that contribute to the overall aspects of the body, such as: generally elongate articles, especially of pereopods and urosomes; elongate antennae in relation to body length; eyes protruding laterally and ventral margins of coxal plates forming nearly a straight horizontal line. Other features shared by them are a small rostrum; interantennal plate with anteroventral angle standing far beyond anterodorsal angle; base of maxilliped extending as a ventral keel; subterminal dactylus on gnathopod 2 of females; pleopods with an inner ramus of only 3 articles and an outer ramus of 4 articles; uropod 2 not extending as far posteriorly as uropod 1 and 3; and a linguiform telson.

Colomastix marielle sp. nov. is particularly similar to C. denticornis , known only from females. Besides the characters sited above, they have similar uropod 3, a serrate anterior margin of the interantennal plate, and are the only species in the genus to have a rostrum with small serrations on lateral margins. However, uropods 1 and 2 are very different between these species, and whereas C. denticornis has strongly serrate medial margins of antennae 1–2, which gives it its name, and a broadly rounded telson apex, Colomastix marielle sp. nov. has weak serrations on medial margins of antennae 1 and 2 and a subtruncate apex of telson. Colomastix marielle sp. nov. can be distinguished from C. halichondriae by the presence of strongly serrate interantennal plate and by the morphology of uropods 2 and 3. In addition, Colomastix marielle sp. nov. can be distinguished from any other species in the genus by the elongate carpus on pereopod 5 of female, and the morphology of the apex of inner ramus of uropod 1. Also, a nail in the dactylus apex of pereopods 3–7 occurs only in C. escobarae and in Colomastix marielle sp. nov.

LeCroy (1995) also indicated that some of the characters shared by this species from Gulf of Mexico were more common to species from other regions. It seems accurate that some of the patterns found in the “ halichondriae group” are more common in species from the Indian and Pacific Oceans, and are uncommon or absent in Atlantic species. Although a more complete evaluation is still needed, these characters seems to include: (1) an interantennal plate with anteroventral angle extending far beyond anterodorsal angle, and usually serrate; (2) female gnathopod 2 with a subterminal insertion of dactylus; (3) basal shell of maxilliped projecting as a ventral keel; (4) uropod 2 not extending as far posteriorly as uropods 1 and 3; (5) unevenly articulated rami of pleopods 1–3, outer ramus 4- articulate and inner 3-articulate; (6) linguiform telson.

Although the state of characters (1) and (5) can not be known from the descriptions of the subantarctic species C. fissilingua and C. subcastellata , and from the Argentinean species C. bastidai , as well as the state of the character (3) to the first two species, it seems likely that none of these characters occur in the Atlantic, with few exceptions. An interantennal plate with anteroventral angle extending beyond anterodorsal angle (1) occur only in C. escobarae , although its specific morphology differs from the “ halichondriae group”. A subterminal dactylus (2) occurs only in C. bastidai . Pleopods with inner ramus 3-articulate and outer ramus 4-articulate (5) occur in Colomastix tubulosa sp. nov. and C. sarae Winfield & Ortiz, 2010 from the Gulf of Mexico. In species from Indian and Pacific Oceans, another asymmetric state of the character (5) occurs, with pleopods with inner ramus 4-articulate and outer ramus 5-articulate. The basal shell of maxilliped projecting as a ventral keel (3), uropod 2 not extending as far posteriorly as uropods 1 and 3 (4), and a linguiform telson, in the Atlantic appears to occur only in the “ halichondriae group”. In fact, this later character appears to be shared only by these species worldwide, although it is not for sure, since in some older publications the specific telson morphology is not clear (i. e. Haswell 1879).

Although in Colomastix taxonomy traditionally the holotype was always a male, unless one was not known when the species was first described, in this species we have chosen a female holotype, due to some important reasons. The type material of Colomastix marielle sp. nov. consisted of 54 specimens from samples of nine different poriferans, collected in the years of 2011, 2015, 2016 and 2017. Out of this material, only two males were found, and they were extremely hard to identify, since they were very small, and their gnathopod two is not greatly enlarged as it usually happens in Colomastix adult males. Besides, species of the “ halichondriae ” group are easily differentiated from others in the genus, as cited above. Although males are very distinctive, this statement seems to be more applicable to females of Colomastix marielle sp. nov., because they have some of the “ halichondriae ” characters more evident than males. Examples of these are characters (1) and (3) cited above, which are more pronounced in females, and there is an absence in males of an elongate uromosite 1 and a subetermianl dactylus of gnathopod 2. Therefore, since females of Colomastix marielle sp. nov. are so much easier to find and to distinguish from other Colomastix species, we decided a female should be the holotype.

Males of Colomastix marielle sp. nov., C. halichondirae and the possible male of C. denticornis , Colomastix sp., also share: an elongate gnathopod 1 (vestigial in most Atlantic species); propodus of gnathopod 2 much less enlarged than in other Atlantic species; uropod 1 with rami almost subequal in length (inner ramus much smaller in other Atlantic species), and inner ramus lateral margins subparallel (as opposite to expanded proximally and tapering distally of other Atlantic species). In C. halichondriae , the propodus is slightly larger than the carpus and in Colomastix marielle sp. nov. it is subeuqual to the carpus, but in both species the shape is typical of a male. In Colomastix sp. however, it resembles more a female gnathopod 2, and has a subterminal dactylus. The apex of the inner ramus of uropod 1 is very distinct between the three species.

In the Atlantic, only males of C. cornuticauda have an unenlarged propodus of gnathopod 2, and they also have an elongate gnathopod 1. However, in this species, the shape of the propodus is very similar to the female but the dactylus is terminal, and it do not have any other of the characters shared by the “ halichondriae ” group.

Figures

FIGURE 10. Colomastix marielle sp. nov. Holotype, adult female (oostegites omitted), 3.6 mm, Porto da Barra Beach, (13° 0’ 14.778” S, 38° 32’ 1.115” W), Salvador city, Bahia state, Brazil, UERJ 112. Adult female, 3.4 mm, only fMd and fMx1, same data as holotype, UERJ 113.Adult female, 2.8 mm, only fHd, A1–2 (lateral), same data as holotype, UERJ 114.Adult male, 1.8 mm, Dentão Rock, (12° 50’ 02.4” S, 038° 31’ 32.0” W), Bahia state, Brazil, in sponge 3—Callyspongia sp., 4–6 m depth, 21 May 2017, UERJ 117. Scale Bar: 0.05 mm for fMd, fMx1, fMx2, Md, Mx1 and Mx2; 0.1 mm for Hd (lateral) and fA2 article 3; 0.2 mm for the remain.