Limnoporeia infirmichelata, Andrade & Senna, 2019

Andrade, L. F. & Senna, A. R., 2019, First record of the genus Limnoporeia Fearn-Wannanı 1968 (Crustacea: Amphipoda: Phoxocephalidae) from the Atlantic Oceanı with description of a new species, Journal of Natural History 53 (41), pp. 2517-2531 : 2519-2528

Limnoporeia infirmichelata sp. nov.

( Figures 1 – 7 )

Material examined

Holotype: 1 femaleı 2.4 mmı dissected and drawnı MBT 155ı 22°22 ’ S – 41°32 ʹ Wı 34 m depthı Rio de Janeiro stateı 5 September 1970ı UERJ 404 ; Paratypes: 1 maleı dissected and drawnı MBT 140 ı 23°02 ’ S – 43°00 ʹ Wı 40 m depthı Rio de Janeiro stateı 2 September 1970ı UERJ 405 ; 5 femalesı in 70% ethanolı MBT 81 ı 24°46 ’ S – 45°58 ʹ Wı 72 m depthı São Paulo stateı 16 June 1970ı UERJ 406 ; 1 femaleı in 70% ethanolı MBT 140 ı 23°02 ’ S – 43°00 ʹ Wı 40 m depthı Rio de Janeiro stateı 2 September 1970ı UERJ 407 ; 1 femaleı in 70% ethanolı MBT 155 ı 22°22 ’ S – 41°32 ʹ Wı 34 m depthı Rio de Janeiro stateı 5 September 1970ı UERJ 408 .

Diagnosis

Head with short rostrumı weakly constricted. Antenna 1 shortı flagella reduced. Antenna 2ı peduncle article 4ı stoutı with 4 rows of facial stout setae; flagellum reduced. Mandibleı molar as a small hump with 2 stout setaeı lacinia mobilis flabellate; palpı article 3ı shorter than article 2ı with 1 long seta laterally. Maxilla 1ı inner plate with setules; palpı 1-articulateı with 3 setae. Maxillipedı plates smallı weakly armoured; palpı article 4 shortı with 1 medium apical nail.

(b) Gnathopod 2. Scale bars: 0.2 mm.

Gnathopod 1ı propodus wider than longı stoutı expanded posterodistallyı weakly chelate; palm obtuse. Gnathopod 2ı carpus almost cryptic; propodus stoutı weakly chelate; palm obtuse. Pereopod 5 broad. Pereopod 6 broad; basis subrectangular and elongate. Pereopod 7ı basis strongly expanded posteroventrallyı reaching half of merusı merus elongate. Uropod 1ı rami with 1 row of stout setae. Uropod 2 short and stout. Uropod 3ı outer ramus about twice the length of innerı article 2 shortı with 2 long setae apically. Telson about 70% cleftı with 1 stout and 1 simple seta on each lobeı dorsal margin with 2 plumose setae on each side.

Description

Based on female holotypeı UERJ 404. Antenna 1 ı peduncle article 1 about 1.2× longer than wideı ventral margin with 1 simple and 3 brush setaeı dorsal margin with short setae distally; article 2 – 3ı ventral and dorsal margins with few simple and brush setae; primary and accessory flagella reducedı 3-articulate. Antenna 2 ı peduncle article 4ı facial stout setae formula: 2-3-3-4ı ventral margin with 1 brush and 2 stout setaeı dorsal margin with simple and brush setae; article 5ı ventral margin with 2 stout and 2 brush setaeı dorsal margin with 4 stout and few long brush setae; flagellum reducedı 2-articulate. Upper lip nakedı apically rounded. Lower lip ı outer and inner lobes with setules apically. Left mandible ı molar as a small hump with 2 stout serrate setaeı incisor multidentateı lacinia mobilis flabellateı with 5 teethı accessory setal row with 5 stout serrate setaeı palpar hump small; palp 3-articulateı article 1ı shortı article 2ı with 1 seta mediallyı article 3ı shorter than article 2ı with 1 long seta laterallyı apex obliqueı with 4 medium to long setae. Right mandible ı molar as a small hump with 2 stout serrate setaeı incisor multidentateı lacinia mobilis flabellateı multicuspidate apicallyı accessory setal row with 4 stout serrate setaeı palpar hump small; palp 3-articulateı article 1ı shortı article 2ı with 1 seta mediallyı article 3ı shorter than article 2ı with 1 long seta laterallyı apex obliqueı with 4 medium to long setae. Maxilla 1 ı inner plate roundedı with setules apically; outer plate with 8 stout multicuspidate setae; palp 1-articulateı with 1 long seta medially and 2 long setae apically. Maxilla 2 ı inner plate about 0.8× the length of outerı with 6 setae; outer plate with 6 setae. Maxilliped ı inner plate with 3 setae apically; outer plate with 1 long seta medially and 2 stout setae apically; palpı article 2 medial margin moderately setoseı article 3 apical and medial margins with 4 long setaeı article 4 with 2 setae and medium apical nail.

Gnathopod 1 ı coxa weakly expanded anteriorlyı ventral margin with 2 short setaeı posterior margin concave; basis about 4.8× longer than wideı anterior and posterior margins with 1 setaı posterodistal corner with 1 short seta; ischium small and subrectanguları posterodistal corner with 1 short seta; merusı posterior margin with 1 seta; carpus elongateı about 3.5× longer than wideı posterior margin with 3 setae; propodus wider than longı stoutı expanded posterodistallyı weakly chelateı with 1 stout seta defining palm; palm obtuseı with setulesı palmar hump small; dactylus subequal to palmı outer margin with 1 short seta proximally. Gnathopod 2 ı coxa subtrianguları ventral margin with 3 short setae; basis about 4.5× longer than wideı posterior margin with 2 long setaeı posterodistal corner with 1 long plumose seta; ischium small and subrectanguları posterior margin with 1 short seta; merusı posterior margin with 2 setae; carpus almost crypticı posterior margin with 1 seta; propodus wider than longı stoutı expanded posterodistallyı weakly chelateı with 1 stout seta defining palm; palm obtuseı with setulesı palmar hump large; dactylus reaching palmar cornerı outer margin with 1 short seta proximally. Pereopod 3 ı coxa subtrianguları ventral margin with 2 short setae; basis about 3.1× longer than wideı anterior margin with setules and 1 brush setaı posterior margin with long setaeı posterodistal corner with 1 long plumose seta; ischium small and subquadrateı posterior margin with 2 setae; merus weakly setose; carpusı posterior margin with 4 long and 5 stout setae; propodusı posterior margin with 6 stout setae; dactylus about 50% the length of propodus. Pereopod 4 ı coxa subtrianguları ventral margin with 2 short setae; remaining articles are very similar to pereopod 3ı differing only by some arrangements of setae. Pereopod 5 ı coxa bilobateı posteroventral margin expandedı with 1 short seta; basis about 1.4× longer than wideı anterior margin with short to long setaeı posterior margin with setulesı facial margin with 1 long seta; ischium small and subrectanguları anterior margin with 1 seta; merus slightly wider than longı anterior margin with 1 stout and few long setae; carpusı anterior margin weakly setoseı with 3 sets of stout setae: 3-2-2; propodusı anterior margin with 5 stout setaeı posterior margin with 1 long and 2 stout setae distally; dactylus about 55% the length of propodus. Pereopod 6 ı coxa anteroventral margin with 2 short setaeı posteroventral margin weakly expandedı with 1 short seta; basis about 1.5× longer than wideı anterior margin with long plumose setae medially and distallyı posterior margin with setulesı facial margin with 1 long seta; ischium small and subrectangular; merusı anterior margin with 1 stout and 2 long setaeı posterior margin with 1 plumose seta distally; carpusı anterior margin with 3 sets of stout setae: 2-2-3ı posterior margin with 1 long and 2 stout setae distally; propodusı anterior margin with 5 stout setaeı posterior margin with 1 long and 1 stout seta distally; dactylus about 55% the length of propodus. Pereopod 7 ı coxa small and subtriangular; basis about 1.2× longer than wideı strongly expanded posteroventrallyı reaching the apex of merusı smoothı without serrationı anterior margin with setulesı anterodistal corner with 1 stout seta; ischium small and subrectanguları anterodistal margin crenateı with 4 subacute projectionsı 1 long stout seta and 2 short stout setae; merus elongateı about 2.2× longer than wideı anterior margin setoseı with stout and long plumose setaeı posterior margin with 3 long setae medially and 6 long bipectinate setae distally; carpusı anterior margin with 5 stout setae and 5 bipectinate setae distallyı posterior margin with 4 bipectinate setae distally; propodusı anterior margin with 2 long and 2 stout setaeı posterior margin with 3 stout setae; dactylus about 65% the length of propodus.

Epimeral plate 1 ı margins roundedı posteroventral corner with a small subrounded projectionı posterior margin convex. Epimeral plate 2 ı anterior margin concaveı ventral margin roundedı posteroventral corner with 1 short setaı posterior margin convex. Epimeral plate 3 ı anterior margin concaveı ventral margin with 3 short setaeı posterior margin concave. Urosomite 2 ı with 2 setae dorsally. Uropod 1 ı peduncle 2.3× longer than wideı dorsomedial margin with 5 stout setaeı dorsolateral margin with 1 stout seta distally; rami subequalı both with 5 stout setae dorsallyı bearing apical nail. Uropod 2 short and stout; peduncle 1.3× longer than wideı dorsal margin with 1 long and 2 stout setae; outer ramusı about 65% the length of innerı dorsal margin with 1 stout setaı bearing apical nail; inner ramusı dorsal margin with 2 stout setaeı bearing a truncate apical nail. Uropod 3 ı peduncle 2.1× longer than wideı dorsal margin with 1 short and 1 long seta; outer ramusı article 1ı ventral margin with 2 acclivities with 2 setae on eachı apical margin with 2 long setaeı article 2 shortı with 2 long setae apically; inner ramusı leaf-likeı with 1 seta apically. Telson shortı about 70% cleftı with 1 simple and 1 stout seta on each lobeı dorsal margin with 2 plumose setae on each side.

Sexual dimorphism

Based on male paratypeı UERJ 405. Body smaller in size. Eyes larger and more pigmented. Antenna 1 ı peduncle article 1ı slightly longer than wideı ventral margin 1 seta distallyı dorsal apex with 1 brush seta; article 2ı ventral margin with 2 setae distallyı dorsofacial margin with 3 brush setae distally; article 3ı ventral and dorsal margins with 2 setae each; primary flagellum reducedı 4-articulate; accessory flagellum reducedı 3-articulate. Antenna 2 ı peduncle article 3ı shortı dorsal margin covered with setules; article 4ı facial stout setae formula: 2-4-3-4ı ventral margin with 2 setae distallyı dorsal margin covered with setulesı with 3 brush setae distally; article 5ı ventral margin with 1 stout seta distallyı dorsal margin with a tuft of setulesı 3 setae and 1 calceolous distallyı facial margin with 2 stout setae; flagellum 16-articulateı with 10 calceoli Gnathopod 1 ı in comparison to the female ’ sı carpus and propodus are somewhat shorter. Gnathopod 2 ı basis with long plumose seta on the posterodistal corner; carpus free; propodus longer than wide.

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Uropod 3 ı peduncle 1.7× longer than wideı dorsal margin with 2 stout setae; outer ramusı article 1ı ventral and apical margin with long plumose setaeı article 2 shortı apical margin with 2 long plumose setae; inner ramusı dorsal margin with long plumose setaeı apical margin with 2 long plumose setae.

Etymology

The name in fi rmichelata is formed from the Latin word in fi rmi that means weakı plus chelata in reference to the weakly chelate palm of gnathopods.

Remarks

Limnoporeia in fi rmichelata sp. nov. and L. woorake are morphologically similar and can be easily distinguished from other species of the genus by gnathopods 1 – 2 with weakly chelate palms instead of fully chelate as observed in the remaining species. The latter species was even cited as a variable within the original diagnosis of Limnoporeia by the contrasting characters on the gnathopods ( Barnard and Karaman 1991). The new species and L. woorake share the following characters: antenna 1ı peduncle article 2 elongate; maxilla 1ı inner plate without setae; maxillipedı inner plate with 3 setae; gnathopods 1 – 2ı propodus stoutı palm obtuse and weakly chelate; telsonı with 1 simple and 1 stout seta on each lobe. Howeverı L. in fi rmichelata sp. nov. differs from L. woorake by the following characters ( L. woorake characters in parenthesis): rostrum shortı almost reaching the apex of article 1 of antenna 1 (longı reaching half of article 2 of antenna 1); antenna 2ı article 5 broad and short (narrow and longer); maxillipedı palp apical nail elongate (medium); gnathopod 1ı carpus shorter (longer); gnathopod 2ı coxa subtriangular (subrectangular)ı basisı posterodistal corner with 1 long plumose setae (without)ı carpus short (elongate); pereopod 7ı basis expandedı reaching the apex of carpus (reaching the apex of propodus)ı merus elongate (short); uropod 1ı rami with a row of stout setae (naked); uropod 2ı rami with stout setae (naked).

Habitat

Since Limnoporeia in fi rmichelata sp. nov. was collected from different samplesı the following types of sediment varies according to the station number of the MBT Project: MBT 81ı sandy silt with shell fragments; MBT 140ı coarse sand without silt; MBT 155ı fine sand with many polychaete tubes.

Geographical distribution

The species is known for the coast of the states of Rio de Janeiro (22°22 ’ S – 41°32 ʹ W and 23°02 ’ S – 43°00 ʹ W) and São Paulo (24°46 ’ S – 45°58 ʹ W). ( Figure 8 )

Bathymetric range

34 – 72 m depth.

Figures

Figure 1. Limnoporeia infirmichelata sp. nov. Female holotype, UERJ 404: (a) Habitus. Male paratype, UERJ 405: (b) Male habitus. Scale bars: 1.0 mm.

Figure 2. Limnoporeia infirmichelata sp. nov. Female holotype, UERJ 404: (a) Head in lateral view; (b) Head in dorsal view; (e) Antenna 1; (f) Antenna 2; (i) Maxilliped; (j) Lower lip; (k) Upper lip. Male paratype,UERJ 405: (c) Antenna 1; (d) Antenna 2; (g) Head in lateral view; (h) Head in dorsal view. Scale bars: 0.2 mm for A–B, D, G–H; 0.1 mm for the remaining.

Figure 3. Limnoporeia infirmichelata sp. nov. Female holotype, UERJ 404: (a) Maxilla 1; (b) Maxilla 2; (c) Left mandible; (d) Right mandible. Scale bars: 0.1 mm.

Figure 4. Limnoporeia infirmichelata sp. nov. Female holotype, UERJ 404: (a) Gnathopod 1; (b) Gnathopod 2. Scale bars: 0.2 mm.

Figure 5. Limnoporeia infirmichelata sp. nov. Male paratype, UERJ 405: (a) Gnathopod 1;

Figure 6. Limnoporeia infirmichelata sp. nov. Female holotype,UERJ 404:(a) Pereopod 3; (b) Pereopod 4; (c) Pereopod 5; (d) Pereopod 6; (e) Pereopod 7. Scale bars: 0.2 mm.

Figure 7. Limnoporeia infirmichelata sp. nov. Female holotype, UERJ 404: (a) Epimeral plate 1; (b) Epimeral plate 2; (c) Epimeral plate 3; (d) Uropod 1; (e) Uropod 2; (f) Uropod 3; (g) Telson. Male paratype, UERJ 405: (h) Uropod 3. Scale bars: 0.2 mm for A–C; 0.1 mm for the remaining.

Figure 8. Distribution of Limnoporeia infirmichelata sp. nov.