Ptilohyale corinne, Rossi & Sciberras & Bulnes, 2020

Rossi, Catalina Di, Sciberras, Michel & Bulnes, Veronica N., 2020, Description of Ptilohyale corinne sp. nov. (Amphipoda: Hyalidae) from the Bahía Blanca estuary, Argentina, including a key to all valid Ptilohyale species, Zootaxa 4763 (1), pp. 125-137 : 127-134

Ptilohyale corinne sp. nov.

( Figs 2–6 )

Material examined. Holotype: adult male 7.38 mm (MACN-In 43240), Argentina, Buenos Aires Province; littoral beach at Arroyo Pareja (38°53´S, 62°07´W), coll. C. Di Rossi, 13 December 2016 . Paratypes: four adult males 7.38–11.32 mm (MACN-In 43241); three adult males, 6.67–9.49 mm ( MLP-XX NNNNN); five adult females, 6.52–10.49 mm (MACN-In 43241); three adult females, 6.94–9.87 mm ( MLP-XX NNNNN); data same as for the holotype .

Type locality. Argentina, BuenosAires Province;littoral beach atArroyo Pareja (38°54´44.26’’S, 62°4´25.55’’W); semi-buried stones in saturated substrate, breakwater region ( Fig. 1 a–b) .

Etymology. The specific name is dedicated to the first author´s niece, Corinne. Noun in apposition.

Description of male (holotype). Head ( Fig. 2a ): without rostrum; eyes reniform.

Antenna 1 ( Fig. 2b ): length 0.25 times as long as body; primary flagellum with 11 articles, each one with one or two aesthetascs except for the last one; accessory flagellum lacking.

Antenna 2 ( Fig. 2c ): length 1.25 times as long as antenna 1; flagellum with 13 articles; peduncular article 5 and flagellar articles 1–6 with posterior brush setae.

Mouthparts. Upper lip ( Fig. 2d ) rounded; anterior margin covered with slender setae decreasing in length from lateral margin to centre; ventral surface with two groups of short spines. Left mandible ( Fig 2e ) with 7-dentate incisor; lacinia mobilis 5-dentate; six setae placed between lacinia mobilis and molar, three of them plumose; molar triturative with one plumose seta. Rigth mandible ( Fig 2f ) with 6-dentate incisor; lacinia mobilis bifid with inner margin dentate; four setae placed between lacinia mobilis and molar, two of them plumose; molar triturative with one plumose seta. Lower lip ( Fig 2g )with outer lobes broad, slightly truncate, with short setules on dorsal surface. Maxilla 1 ( Fig 2h ) with inner lobe slender with a row of setules along outer margin and two apical plumose setae; outer lobe broad with a row of setules along inner margin, four dentate and three serrate apical spines; palp slender, uniarticulate, with a constriction in the middle and one apical seta. Maxilla 2 ( Fig. 2i ) with 8-dentate inner lobe bearing ten naked and two plumose setae (innermost the longest); outer lobe with 18 terminal setae. Maxilliped ( Fig. 2j ) with inner plate bearing three nodular and 13 plumose setae; outer plate with ten serrate and ten naked setae along apical and inner margin; palp with four articles: article 1 with three apical inner setae, article 2 with several long setae along inner margin and one seta on outer apical corner, article 3 with several setae along inner margin and several naked and plumose setae on outer corner, and article 4 unguiform with seven inner setae, two apical setae and one strong terminal spine.

Gnathopods ( Fig. 3 a–b) subchelate; gnathopod 1 smaller than gnathopod 2. Gnathopod 1 ( Fig. 3a ): coxa broad with a posterior marginal cusp, armed with marginal (long and slender) and submarginal (short and strong) spines; basis with medioventral lobe developed, distal margin being serrated from the medioventral lobe up to the posterior margin; ischium with medioventral lobe; merus rectangular with seven setae on posterodistal corner; carpus with lobe developed, armed with several plumose setae, three plumose setae on inner surface and three naked setae on anterodistal corner; propodus with six long setae on anterodistal corner, a row of several setae on posterior margin; palm transverse with several simple setae and three setae in tandem, defined by two strong spines in tandem; dactylus fitting palm with four short spines on inner margin and an outer plumose seta. Gnathopod 2 ( Fig. 3b ): coxa broad with two posterior marginal cusps, armed with marginal (long and slender) and submarginal (short and strong) spines; basis with medioventral lobe developed, distal margin being serrated from the medioventral lobe up to the posterior margin; ischium with medioventral lobe and weak hydrodynamic lobe; merus with four setae on posterodistal corner; carpus with a strong spine on anterodistal corner; propodus developed with a lobe on anterodistal corner, armed with four setae on anterodistal corner and a row of seven setae on posterior margin; palm slightly oblique with two strong simple spines, ten spines in tandem and several setae, defined by two strong spines in tandem; dactylus fitting palm with ten short spines on inner margin and a plumose outer seta.

Pereopod 3 ( Fig. 3c ): coxa with two posterior marginal cusps, armed with marginal (long and slender) and submarginal (short and strong) spines. Basis elongate with medioventral lobe and armed with a few setae on anterior margin, four spines and one seta along posterior margin, and four setae on posterodistal corner. Ischium short with medioventral lobe and a process on anterior margin, armed with three setae on posterodistal corner. Merus with three spines in tandem on anterior margin, one plumose spine and two naked setae on anterodistal corner, one seta on posterior margin and seven setae on posterodistal corner. Carpus with two setae on anterodistal corner, six setae on posterodistal corner and five setae along posterior margin. Propodus with two setae on anterodistal corner, four setae and one spine on posterodistal corner, and two groups of elements formed by one spine in tandem and one small simple spine each one on posterior margin. Dactylus with a short inner seta.

Pereopod 4 ( Fig. 3d ): coxa with a single posterior marginal cusp, armed with marginal (long and slender) and submarginal (short and strong) spines. Basis with medioventral lobe, armed with two setae on anterodistal corner, four setae on posterodistal corner and four spines along posterior margin. Ischium short with medioventral lobe and a process on anterior margin, armed with four setae on posterodistal corner. Merus with two spines in tandem on anterior margin, three naked setae and one plumose seta on anterodistal corner, five setae on posterodistal corner and three setae along posterior margin. Carpus with an anteroventral process, armed with two setae on anterodistal corner, eight setae on posterodistal corner and three setae on posterior margin. Propodus with an anteroventral process, armed with one seta on anterodistal corner, seven setae on posterodistal corner and two groups of elements on posterior margin, one with one spine in tandem and one seta; the other with one spine in tandem and two setae. Dactylus with a plumose outer seta, a naked inner seta and a subterminal setule.

Pereopod 5 ( Fig. 3e ): coxa bilobate; anterior lobe more developed with submarginal spines; posterior lobe with marginal (long and slender) and submarginal (short and strong) spines. Basis broad with notch and surge seta, and short spines on posterior margin, a group of spines, some of them simple and others in tandem, on anterodistal corner, and six spines in tandem along anterior margin. Ischium short with a process on posterior margin and three spines in tandem on anterodistal corner. Merus with three spines in tandem on posterior margin, one spine in tandem and five simple spines on posterodistal corner, two spines in tandem and six simple spines on anterodistal corner, and three spines in tandem on anterior margin. Carpus with three spines in tandem and five simple spines on posterodistal corner, one spine in tandem and four simple spines on anterodistal corner, and a group of one spine in tandem, one simple spine and one spine (broken in holotype) on anterior margin. Propodus with five setae on posterodistal corner, two setae and three spines on anterodistal corner, and three groups of elements (two of them formed by one spine in tandem and two simple spines, and the other by one spine in tandem and one simple spine) on anterior margin. Dactylus with a plumose outer seta, an inner seta and a subterminal setule.

Pereopod 6 ( Fig. 3f ): coxa bilobate with both lobes poorly defined; posterior one more developed than anterior. Basis broad with notch and surge seta and short spines on posterior margin, and five pairs of simple spines along anterior margin and one pair in tandem. Ischium short with a process on posterior margin, and one spine in tandem and one simple spine on anterodistal corner. Merus with four spines on posterior margin, two spines in tandem and four simple spines on posterodistal corner, three spines in tandem on anterodistal corner, and two spines in tandem on anterior margin. Carpus with three spines in tandem and 12 simple spines on posterodistal corner, three spines in tandem and four simple spines on anterodistal corner, and three spines in tandem on anterior margin. Propodus with nine setae on posterodistal corner, three spines and five setae on anterodistal corner, and spines in tandem and simple spines along anterior margin. Dactylus with a plumose outer seta, an inner seta and a subterminal seta.

Pereopod 7 ( Fig. 3g ): coxa rounded ventrally with a few submarginal spines. Basis broad with a proximal depression, notch and surge seta and short spines on posterior margin, two spines in tandem and two simple spines on anterodistal corner, and nine spines along anterior margin. Ischium short with a process on posterior margin, armed with one spine in tandem and three simple spines on anterodistal corner. Merus with four spines in tandem on posterior margin, one spine in tandem and five simple spines on posterodistal corner, a similar spine configuration on anterodistal corner, and two groups of spines on anterior margin; one in tandem and two simple. Carpus with four spines in tandem and six simple spines on posterodistal corner, one spine in tandem and six simple spines on anterodistal corner, and one spine in tandem and two simple spines on anterior margin. Propodus with ten setae on posterodistal corner, two spines and five setae on anterodistal corner, and five spines in tandem and three simple spines along anterior margin. Dactylus with a plumose outer seta, an inner seta and a subterminal setule.

Pleopods 1–3 ( Fig. 4 a–c) slender; rami longer than penduncle, covered by plumose setae. Pleopod 3 with inner retinacula ( Fig. 4c ).

Uropods. Uropod 1 ( Fig. 5a ) biramous; peduncle with four outer spines in tandem, three inner spines in tandem and one elongate terminal spine with irregular dorsal margin; outer ramus with three marginal spines, two of them in tandem, and three apical spines, one of them in tandem; inner ramus with one marginal spine in tandem and four apical spines, two of them in tandem. Uropod 2 ( Fig. 5b ) biramous, shorter than uropod 1; peduncle shorter than rami with four spines in tandem; outer ramus with two marginal spines in tandem and three apical spines, one of them in tandem; inner ramus with two marginal spines in tandem and four apical spines, two of them in tandem. Uropod 3 ( Fig. 5c ) uniramous; peduncle shorter than ramus with one elongate spine in tandem on inner corner; ramus with eight apical spines in tandem.

Telson ( Fig. 5d ): bilobate, fully cleft, asymmetrical; each lobe with a simple inner seta and three dorsal plumose setae. The lobes separated during the dissection of the holotype.

Description of female (allotype). Head: without rostrum; eyes reniform eyes. Sexual dimorphism expressed in antenna 2, gnathopod 2, pereonite 2 and coxa of pereonite 3. Antenna 2 ( Fig. 6a ): flagelum with 12 articles; brush setae on peduncular article 5 and flagelar article 1–4, less dense than in male. Gnathopod 2 ( Fig. 6b ): smaller than male; with brood lamellae; coxa with one posterior marginal cusp, with marginal and submarginal spines on posterodistal margin. Pereopod 3 ( Fig. 6c ): coxa with single posterior marginal cusp. Preamplexing notch ( Fig. 6d ) on anterodistal margin of peraeon segment 2.

Colour. Live specimens dark green with black eyes; preserved specimens in 70% ethanol yellow with black eyes.

Variability. Body length varied between 6.67 mm and 11.32 mm (n = 8; mean = 8.47 mm, standard deviation = 1.51) in males and between 6.52 mm and 10.49 mm (n = 8; mean = 8.57 mm, standard deviation = 1.58) in females.

Figures

FIGURE 1 a Map of Argentina with Buenos Aires Province in gray and Bahía Blanca estuary indicated by an arrow; b Map of Bahía Blanca estuary showing Arroyo Pareja (type locality), water in gray.

FIGURE 2 Ptilohyale corinne sp. nov., male holotype: a habitus, lateral; b antenna 1; c antenna 2; d upper lip; e left mandible; f right mandible; g lower lip; h maxilla 1; i maxilla 2; j maxilliped. Scale bars: 1 mm (a), 200 µm (b–c, e–j), 100 µm (d).

FIGURE 3 Ptilohyale corinne sp. nov., male holotype: a gnathopod 1; b gnathopod 2; c pereopod 3; d pereopod 4; e pereopod 5; f pereopod 6; g pereopod 7. Scale bars: 200 µm.

FIGURE 4 Ptilohyale corinne sp. nov., male holotype: a pleopod 1; b pleopod 2; c pleopod 3. Scale bars: 200 µm.

FIGURE5 Ptilohyale corinne sp. nov., male holotype: a uropod 1; b uropod 2; c uropod 3; d telson. Scale bars: 200 µm.

FIGURE6 Ptilohyale corinne sp. nov., female allotype: a antenna 2; b gnathopod 2; c coxa 3; d peraeon segments 1–3, preamplexing notch indicated by an arrow. Scale bars: 200 µm (a–c), 0.5 mm (d).