Nebalia villalobosi, Ortiz, Manuel, Winfield, Ignacio & Cházaro-Olvera, Sergio, 2011

Ortiz, Manuel, Winfield, Ignacio & Cházaro-Olvera, Sergio, 2011, A new sponge-inhabiting leptostracan species of the genus Nebalia (Crustacea: Phyllocarida: Leptostraca) from the Veracruz Coral Reef System, Gulf of Mexico, Zootaxa 3027, pp. 52-62 : 53-61

Nebalia villalobosi n. sp.

( Figs. 1–6 )

Material examined. Holotype: adult female, 5 mm ( CNCR #26196); Allotype: adult male, 3 mm ( CNCR #26197). Paratypes ( CNCR #26198): 56 females (3.8–5.1 mm), 3 males (3.3, 3.7, 3.9 mm).

Type locality. Veracruz Coral Reef System, Veracruz State, Mexico, SW Gulf of Mexico; 0 7 May 2007; Blanquilla coral reef, 19°13’32.9" N and 96°05’53.0" W, 12 m depth. Collected from the sponge Ircinia fistularis Verrill (Dictyoceratyda: Irciniidae ) ( CNPGG #0896).

Diagnosis. Carapace extending back to the middle of the third abdominal segment along the sides, but with a narrow dorsal sinus. Eyes large, oval, slightly tapering distally, forming single distal lobe. Marginal ommatidia may be seen, the rest of the eye is black. Rostrum twice as long as wide. Antennular flagellum with up to 13 articles. Antenna with flagellum almost equal in length to half the body length, 60 or fewer articles of which the first 18–20 are very short, not fused. Exopod of second maxilla as long as first article of endopod. Article 3 of mandible palp with inner border covered with robust setae. Postero-lateral border of pereonite 4 with rounded denticles. Peduncle of pleopod 4 smooth. Pleopod 5 with 6 robust setae slightly longer than the distal point. Pleonite 6 with rounded denticles along dorsal posterior border. Caudal furca slightly longer than pleonite 7 and telson combined.

Description. Carapace: oval, not covering pereonite 4 ( Fig. 1 A); dorsal-posterior margin concave with medial notch, bilobate ( Fig. 2 C).

Rostrum: length 2 times eye orbits; depressed distally in lateral view ( Figs. 1 B, 1C). Ventral keel poorly developed; antero-lateral border and anterior depression not clearly seen ( Fig. 1 D). Eyes, reaching 2/3 of rostrum length, directed downward, supraorbital plate vestigial.

Antennule: peduncle 4-segmented; article 2 with short and long setae; article 3 wider at subdistal point, bearing a tuft of long setae on distal border; article 4 shorter than 2, widest distally, 4 short setae on ventral border, a short robust setae on distal dorsal border beside the articulation of the antennal scale; antennal scale elongate, length 2 times width; distal and proximal half of ventral border with a long seta; flagellum longer than peduncle with 14 articles; articles 1–2 not clearly separated; a pair of aesthetascs from articles 7 to 12, almost all with an apical seta ( Fig. 2 A).

Antenna: peduncle 3-segmented; article 1 with a small straight tooth placed subdistally; article 2 with a distal dorsal tooth; article 3 as long as 2, length 1.2 times width, several robust setae and smooth-plumose setae along dorsal margin, 4 long setae on ventral margin, a small anterior lobe with 3 curved setae, 4 long setae on rest of distal border; flagellum well developed, longer than peduncle, with almost 60 articles ( Fig. 2 B).

Mandible: mandible molars well developed, mandible palp 3-segmented; right molar quadrangular, bifid distally; left molar triangular; article 3 shorter than 2, with parallel margins, rounded distally; outer border covered with parallel simple setae, lined with small setae ( Figs. 3 B, 3C).

First maxilla: protopod with 2 endites, endite 1 with a simple seta bearing setulose setae, endite 2 larger than 1, with 6 long spatulate and 7 short simple setae; palp well developed, almost 4 times length of protopod, with 4 spaced setae, 2 on distal tip ( Fig. 3 A).

Second maxilla: protopod with 4 endites armed with long setae, endites 1 and 3 largest; endopod longer than exopod, with 2 articles, distal article 2/3 length of basal article; exopod almost surpassing articulation between articles 1 and 2 of endopod; terminal seta of distal article on endopod, shorter than entire ramus ( Fig. 3 D).

Thoracopods: thoracopod 1 endopod as long as exopod, weakly divided, distal article with 6 setae, one small on lateral margins; exopod with a few short setae along ventral and lateral margins. Epipod short without setae ( Fig. 4 A). Thoracopods 2–4 exopods and epipods gradually enlarging to almost the length of thoracopod 5. Thoracopod 5 endopod slightly longer than exopod, bearing a distal article with a tuft of 6 setae; exopod with a small seta dividing 2 incipient lobes on ventral margin; epipod almost reaching basal half of exopod ( Fig. 4 B). Thoracopods 6 and 7 exopods and epipods gradually enlarging to almost the length of thoracopod 8. Thoracopod 8 endopod as long as exopod, bearing a distal article with 6 setae; exopod covered with setae on outer border; epipod almost reaching 2/3 length of exopod ( Fig. 4 C).

Pleopods: pleopod 1 peduncle with a long subdistal seta that covers exopod halfway; exopod 2 times longer than peduncle, inner border covered with 14 setae, 4 long and 2 short apical robust setae; endopod 2-articles, 3 times longer than peduncle, a short terminal robust setae, inner border covered with 17 long setae; epipod longer than wide, teeth on distal border ( Fig. 5 A). Pleopod 2 peduncle very stout with a subdistal curved robust setae; exopod short, quadrangular, outer border with 4 long and 5 short robust setae, 3 long distal setae; endopod 2-articles, almost 1.1 times length of peduncle, a short distal robust setae, 4 simple setae; outer border covered with 18 setae; epipod not seen ( Fig. 5 B). Pleopod 3 peduncle stout, a distal robust setae covers 1/4 of exopod; exopod longer than peduncle but shorter than endopod, covered with a set of long and short setae on outer border, 2 apical setae and 7 long setae on distal half of inner border; endopod with setae all around; epipod with 2 coupling robust setae ( Fig. 5 C). Pleopod 4 peduncle shorter than rami; endopod smaller than exopod, bearing 3 submarginal robust setae on inner border and 4 on distal half of outer border, 3 distal robust setae ( Fig. 6 A). Pleopod 5 ramus almost 3 times longer than peduncle, 6 long robust setae along distal half of outer border, bearing 4 distal setae, inner border with 13 tip curved robust setae ( Fig. 6 B). Pleopod 6 longer than wide, 4 robust setae on inner border, 1 long and 2 short distal robust setae, 3 robust setae on distal half, and 1 basally on outer border ( Fig. 6 C).

Pleonites: pleonites 2–5 increasing its length backward, rounded denticles along postero-dorsal border; pleonites 6–7 twice length of pleonite 5, denticles of pleonite 6 wider than denticles of pleonite 7 ( Fig. 6 E).

Telson and furca: anal scales not seen; telson is 1.1 times length of pleonite 7, quadrangular; furcal rami tapering distally, as long as telson + pleonite 7 combined, 12 setae along outer lateral margin and 14–17 along medial margin, distally each ramus with a very stout and long robust setae, one on right ramus 1/2 length, on left ramus 1/ 3 length ( Fig. 6 D).

longicornis .

Male paratype. Similar to female but smaller; rostrum less depressed in lateral view; bearing less ommatidea which are placed only distally; antennule with a flagellum comprising 6 articles; flagellum of antenna bearing 4 articles.

Etymology. The new species is named in honour of Dr. José Luis Villalobos Hiriart, researcher and friend at the Instituto de Biología, UNAM.

Distribution. Veracruz Coral Reef System National Park, SW Gulf of Mexico, Mexico.

Remarks. In comparing females of Gulf of Mexico Nebalia species, N. villalobosi n. sp. is most morphologically similar to N. longicornis , and N. lagartensis , but is easily distinguished from these two species by the following characteristics: The rostrum is ovoidal instead of bearing parallel borders backward as in N. lagartensis or tapering distally as in N. longicornis . The new species shows relatively large and distally expanded eyes with a small supraorbital plate, instead of a distally pointed eye and an upward supraorbital plate as in N. lagartensis or distally rounded eye and supraorbital plate surpassing half way the length of the eye as in N. longicornis . The mandible has the inner border of palp article 3 covered with setae, instead of a distal tuff as in N. lagartensis or a distal seta as in N. longicornis . The antennal flagellum of N. villalobosi n. sp. has almost 60 articles of which 40 are very short, instead of normally developed articles in the antennal flagella as seen in N. lagartensis and N. longicornis . In N. villalobosi n. sp. article 2 of the endopod on the second maxilla is shorter than the basal article, also seen in N. longicornis , but an exopod that does not reach the basal part of the endopod article 2, as in N. lagartensis and N. longicornis . In N. villalobosis n. sp. the epipod of thoracopod 1 does not reach the basal part of the exopod, as seen in N. lagartensis and N. longicornis . Pleopod 5 is expanded distally and armed with robust setae at both sides, instead of having tapering apex bearing robust setae only at one side as seen in N. lagartensis and N. longicornis . In N. villalobosi n. sp. pleopod 7 is ovoidal and covered all around with setae, instead of pleopod 7 being pointed distally and with fewer setae as in N. lagartensis and N. longicornis . Finally, N. villalobosi n. sp. is a sponge-inhabiting crustacean while N. lagartensis and N. longicornis are only recorded as free-leaving leptostracans associated with soft bottoms.

Figures

FIGURE 1. Nebalia villalobosi n. sp. A, female holotype (lateral view); B, eye; C, head and carapace of male paratype; D, rostrum. Scale bars: A = 1.0 mm, B = 0.5 mm, C = 0.6 mm, D = 0.8 mm.

FIGURE 2. Nebalia villalobosi n. sp. Female holotype. A, antennule; B, antenna; C, posterior border of carapace (dorsal view). Scale bars: A = 0.6 mm, B = 0.6 mm, C = 0.5 mm.

FIGURE 3. Nebalia villalobosi n. sp. Female holotype. A, first maxilla; B, right mandible; C, left mandible; D, second maxilla. Scale bars: A = 0.3 mm, B – C = 0.6 mm, D = 0.3 mm.

FIGURE 4. Nebalia villalobosi n. sp. Female holotype. A, thoracopod 1; B, thoracopod 5; C, thoracopod 8. Scale bars: A, B and C = 0.6 mm.

FIGURE 5. Nebalia villalobosi n. sp. Female holotype. A, pleopod 1; B, pleopod 2; C, pleopod 3. Scale bars: A = 0.6 mm, B = 0.25 mm, C = 0.6 mm.

FIGURE 6. Nebalia villalobosi n. sp. Female holotype. A, pleopod 4; B, pleopod 5; C, pleopod 6; D, telson and furca; E, denticles of pleonal segments six and seven. Scale bars: A = 0.6 mm, B = 0.4 mm, C = 0.4 mm, D = 0.5 mm, E = 0.01 mm.