Diastylis fabrizioi, Alberico & Roccatagliata, 2008

Alberico, Natalia A. & Roccatagliata, Daniel, 2008, Diastylis fabrizioi, a new species and brief redescription of D. planifrons Calman, 1912 (Crustacea: Cumacea: Diastylidae) from South America, Journal of Natural History 42 (13 - 14), pp. 1039-1063 : 1042-1055

Diastylis fabrizioi n. sp.

( Figures 2–9 , 10A–E )

Material examined

R/V ‘‘ Veliger’ ’. Anchieta Island , São Paulo State, approximately 23 ° 329S, 45 ° 049W. Sta. D 4-12(4)VIII, 18 m, 02 March 1963: 1 ovigerous ♀, 1 preparatory ♀. Sta. T17a- 12(3)VIII, 18 m, 02 March 1963: 1 ovigerous ♀, 1 preparatory ♀, 1 juvenile. Sta. N13a-12(4)VIII, 18 m, 02 March 1963: 2 preparatory ♀♀, 1 juvenile. Sta. 187- 14(1)IX, 18 m, 29 January 1964: 1 preparatory ♀, 1 subadult „. Sta. 128-14(3)IX, 18 m, 29 January 1964: 1 subadult „. Sta. 467-16(2)IX, 21 m, 03 February 1964: 1 subadult „. Sta. 617-48(1)IX, 13 m, 11 February 1964: 2 ovigerous ♀♀, 2 subadult „„, 1 juvenile. F/V ‘‘ Lerez’ ’. Sta. 8201/16, 34 ° 019S, 53 ° 159W, 15 m, 06 February 1982: 1 preparatory ♀. Sta. 8204/10, 35 ° 279S, 55 ° 059W, 22 m, 05 March 1982: 1 ovigerous ♀, 1 preparatory ♀. R/V ‘‘Aldebarán’’. Sta. 9906-23, 34 ° 08910S, 53 ° 34940W, 19 m, 11 December 1999: 15 ovigerous ♀♀, 24 preparatory ♀♀ (2 of them infested with nicothoids), 12 adult „„, 11 subadult „„, 12 juveniles (1 of them infested with nicothoids) (Holotype: MACN-In. 37087; Paratypes: MACN-In. 37088, MUNHINA 1962). Sta. 9901–25, 34 ° 48970S, 54 ° 21990W, 25 m, 27 January 1999: 62 ovigerous ♀♀ (5 of them infested with nicothoids), 47 preparatory ♀♀ (11 of them infested with nicothoids), 1 adult „, 15 subadult „„ (2 of them infested with nicothoids), 55 juveniles, 18 mancas. Sta. 2002–05 R2, 34 ° 109S, 53 ° 009W, 33 m, December 2002: 65 ovigerous ♀♀ (9 of them infested with nicothoids), 99 preparatory ♀♀ (5 of them infested with nicothoids), 27 adult „„, 57 subadult „„, 898 juveniles (4 of them infested with nicothoids), 30 mancas. Sta. 2002–05 R1, 35 ° 119S, 54 ° 169W, 30 m, 13 December 2002: 20 ovigerous ♀♀ (3 of them infested with nicothoids), 15 preparatory ♀♀ (4 of them infested with nicothoids), 8 adult „„, 3 subadult „„, 12 juveniles, 1 manca. R/V ‘‘ Eduardo Holmberg’ ’. EH 03/02, Sta. 11, 35 ° 469S, 56 ° 319W, 13 m, 02 August 2002, stomach content of Umbrina canosai Berg, 1895 (Sciaenidae) , coll. Diego Giberto: 3 ovigerous ♀♀, 2 preparatory ♀♀, 1 subadult „, 1 juvenile. R/V ‘‘ Lamatra’ ’. Sta. IP0063, 36 ° 019S, 56 ° 099W, 18 m, 16 December 1979: 4 ovigerous ♀♀, 1 adult „. Las Toninas. 36 ° 299S, 56 ° 409W, 2– 10 m, 09–11 February 2000: 5 ovigerous ♀♀, 2 adult „„. Proyecto de Fomento Pesquero. PFP VIII, off Mar del Plata , 38 ° 029S, 57 ° 309W, night plankton, 23 October 1967: 1 ovigerous ♀, 2 juveniles. PFP XII, off Mar del Plata , 02–03 November 1967: 1 adult „, 1 subadult „. Puerto Quequén. Sta. 2, 38 ° 419270S, 58 ° 429060W, 39.5 m, 15 December 2005: 1 preparatory ♀, 1 subadult „, 3 juveniles. Sta. 3, 38 ° 419220S, 58 ° 429W, 38 m, 15 December 2005: 2 juveniles. Sta. 4, 38 ° 429490S, 58 ° 419530W, 45 m, 15 December 2005: 2 preparatory ♀♀, 3 subadult „„, 6 juveniles, 1 manca. Sta. 9, 38 ° 479130S, 58 ° 419360W, 51.7 m, 15 December 2005: 1 juvenile. Sta. 11, 38 ° 509320S, 58 ° 419010W, 58.7 m, 15 December 2005: 1 preparatory ♀ (infested with nicothoids). Sta. 12, 38 ° 509330S, 58 ° 419050W, 57.7 m, 15 December 2005: 1 ovigerous ♀, 2 juveniles. Sta. 13, 38 ° 509390S, 58 ° 409570W, 60 m, 15 December 2005: 1 juvenile. Sta. 15, 38 ° 419380S, 58 ° 429240W, 40 m, 15 December 2005: 1 preparatory ♀, 1 subadult „. Sta. 18, 38 ° 369440S, 58 ° 419540W, 25.3 m, 15 December 2005: 1 juvenile, 4 mancas. Sta. 20, 38 ° 359350S, 58 ° 429040W, 15.3 m, 15 December 2005: 1 adult „. R/V ‘‘ Shinkai Maru’ ’. Sta. SMVI-15, 40 ° 319180S, 61 ° 329240W, 36 m, 26 September 1978: 1 adult „, 1 subadult „. San Antonio Oeste, Bahía Reparo , 40 ° 479S, 64 ° 549480W, 3 m, 26 November 1997: 10 ovigerous ♀♀, 31 preparatory ♀♀, 1 adult „, 9 subadult „„, 95 juveniles, 14 mancas. San Antonio Oeste. Sta. 2, 40 ° 539050S, 65 ° 049260W, 12 m, 03 January 2005: 1 subadult „, 1 juvenile. Sta. 8, 40 ° 539210S, 65 ° 049W, 20 m, 03 January 2005: 2 subadult „„, 1 juvenile. Sta. 11, 40 ° 539090S, 65 ° 049160W, 12–20 m, 03 January 2005: 1 ovigerous ♀, 1 preparatory ♀. Sta. 12, 40 ° 539040S, 65 ° 049200W, 12–20 m, 03 January 2005: 1 ovigerous ♀, 1 preparatory ♀, 1 adult „, 4 juveniles, 2 mancas. Sta. 14, 40 ° 559430S, 65 ° 049190W, 12–20 m, 05 January 2005: 1 preparatory ♀. Sta. 15, 40 ° 559430S, 65 ° 049190W, 12–20 m, 05 January 2005: 1 juvenile. Sta. 20, 40 ° 559370S, 65 ° 059060W, 16 m, 05 January 2005: 1 preparatory ♀, 1 juvenile, 1 manca. Sta. 21, 40 ° 559120S, 65 ° 039590W, 18 m, 05 January 2005: 1 juvenile.

Description of ovigerous female

Based on the holotype MACN-In. 37087 and the paratype MACN-In. 37088a.

Total length

Approximately 7.4 mm.

Carapace ( Figures 2A, B ; 10A, B )

Approximately 1.3 times as long as wide, with two prominent oblique ridges that enclose a large depressed dorso-anterior area (plateau). Both oblique ridges have a row of denticles anteriorly (more clearly visible in dorsal view). At approximately one-third of the way from the anterior end each oblique ridge joins a curved ridge that runs upwards from the lower edge of the carapace (point of junction not produced into a tooth or angularity). From each curved ridge, a horizontal ridge extends backwards that disappears before reaching the posterior margin of carapace. Dorsally, each oblique ridge meets a longitudinal (or slightly divergent) ridge coming from the hind margin of the carapace. At each of these merging points a third ridge originates, and these converge, from the left and right, into a blunt mid-dorsal ridge that fades away a short distance after reaching the frontal lobe. A pentagonal figure enclosing a depressed area is defined by the posterior margin of the carapace (side ‘‘a’’) together with the two longitudinal ridges (sides ‘‘b’’) and the two convergent ridges. Side ‘‘a’’ of pentagon is 1.23–1.58 times as long as side ‘‘b’’. The frontal lobe has two hardly visible transverse grooves. The pseudorostrum is more than twice the ocular lobe length. The latter with three clear areas (or poorly developed lenses) arranged in a triangle, central area covering two contiguous ommatidia, latero-posterior areas covering one ommatidium each. Antennal notch widely open, antero-lateral angle rounded, inferolateral edge hardly serrate.

Thorax

Postero-lateral angles of pereonite 5 short and rounded in dorsal view.

Pleon

Slightly shorter than carapace and free pereonites combined.

Telson ( Figures 6D , 10E )

Approximately 1.5 times as long as last pleonite, with six cuspidate setae on each side (four to eight in other ovigerous females examined) and two divergent cuspidate setae stouter than the lateral setae distally.

Antenna 1 ( Figure 2C )

Peduncle, article 1 approximately as long as articles 2 and 3 combined, with several large teeth on distal margin, four or five unequal setulate setae on inner corner and one simple seta arched over article on outer corner; article 2 approximately 0.8 as long as article 3. Main flagellum of five articles, articles 1–4 subequal in length and article 5 minute, articles 4 and 5 with one aesthetasc each. Accessory flagellum almost reaching distal end of article 2 of main flagellum; of three articles, article 2 the longest.

Antenna 2 ( Figure 2D )

Has three (four?) articles. Distal article minute, with one seta with tiny setules. Remaining articles with one setulate seta each.

Right mandible ( Figure 3A )

Has one rudimentary lacinia mobilis and 12 setae (five most distal ones bifurcated).

Left mandible

As right but with well-developed lacinia mobilis.

Maxilla 1 ( Figure 3B )

Outer endite with 14 cuspidate distal setae and one small seta on outer margin. Inner endite with five unequal distal setae. Palp with two long distal setae bearing tiny retrorse setules distally.

Maxilla 2 ( Figure 3C )

Protopod, inner margin with two setulate setae and a row of approximately 27 setae that fully agree with the plumose type described by Garm (2004); distal end with simple, setulate and serrate setae. Outer endite with three serrate and three serrulate setae; inner endite with three serrate and one serrulate setae.

Maxilliped 1 ( Figure 4A )

Basis with five setuloserrate setae on inner distal margin. Endite with five setulate setae (some of them also serrate distally), four serrulate setae and two stout setae (one oval with a row of teeth distally, one crescent-shaped, see details). Merus with two or three translucent teeth and two simple setae on outer margin. Carpus, inner margin with sparsely setulate setae and a row of nine setae (each with setules proximally and three or four lamellae distally, see detail), ventral surface with many simple setae (not drawn), outer distal corner with one large setulate seta. Propodus with many simple setae (not drawn) and three large setulate setae. Dactylus narrow, with two lateral simple setae and two distal serrulate setae.

Maxilliped 2 ( Figure 4B )

Basis shorter than the remaining articles together, dorsal surface with two barely setulate setae distally and several small simple setae, ventral surface with four or five setulate setae distally (not drawn, similar to those shown for male in Figure 7D ) and several small simple setae. Merus approximately as long as propodus and 0.75 as long as carpus, with one setulate seta on distal outer corner, two setulate setae on inner margin and several small simple setae on dorsal and ventral surfaces. Carpus with two unequal setulate setae on distal outer corner and 15 setae (14 in other specimens examined) on inner margin (only most dorsal ones drawn). Propodus, outer margin with one strong setulate seta in proximal third of article and one barely setulate seta distally; inner margin with 12 barely setulate setae and five serrulate setae in between (only a few setae drawn, a detail of one of these serrulate seta is presented in Figure 4B ). Dactylus with serrulate and simple setae distally.

Maxilliped 3 ( Figure 4C )

Basis expanded distally (opercular), inner margin with a row of teeth and many setulate setae, distal process with six setulate setae. Ischium broad, with one setulate and two simple setae on inner margin. Merus with three setulate setae on inner margin and one strong setulate seta on outer margin. Inner distal corner of ischium and merus with teeth (those on ischium larger). Carpus with four setulate setae on inner margin and two unequal setulate setae on distal outer corner. Propodus with five to seven setulate setae on inner margin and one setulate seta on outer distal corner. Dactylus with six long setae (five simple and one serrulate) distally and three short serrulate setae on inner margin. Exopod: flagellum of six articles.

Pereopod 1 ( Figure 5A )

Basis approximately 0.86 as long as remaining articles together, with setulate setae on both margins and distally. Merus with both setulate and simple setae distally, remaining articles with simple setae only. Ischium and merus combined approximately as long as carpus. Ischium, merus and carpus combined approximately 0.9 as long as propodus and dactylus combined. Dactylus approximately two-thirds as long as propodus. Exopod: flagellum of seven articles.

Pereopod 2 ( Figure 5B )

Basis approximately as long as remaining articles together, with a row of teeth on outer margin and setulate setae on both margins. Ischium and merus combined approximately 0.64 as long as carpus. Merus with three setulate setae distally (outer seta more profusely setulate than the others). Carpus approximately 1.3 times as long as propodus and dactylus together, with a serration on dorsal surface and with short simple setae on both margins and distally. Exopod: flagellum of seven articles.

Pereopod 3 ( Figure 6A )

Basis approximately as long as remaining articles together, with long setulate setae, short simple (?) setae (dirtiness precludes confirmation whether they are simple, finely setulate or contaminated by fungal hyphae), and broom setae. Ischium with several setae distally: one short simple (?), others long and annulate. Merus with annulate setae (only those on outer surface drawn). Carpus approximately 0.75 as long as merus, with annulate setae, viz. six on outer surface and three (two setae in other three specimens examined, not drawn) on inner surface. Propodus with one annulate seta and one broom seta. Dactylus with one three-toothed cuspidate seta and one simple seta (see detail). Exopod of two articles, distal article with four unequal setae (some of them may be setulate).

Pereopod 4 ( Figure 6B )

As pereopod 3 except for: basis shorter than remaining articles together. Ischium with annulate setae only. Carpus 0.80 as long as merus, with seven or eight annulate setae on outer surface (two most proximal with a few setules; in other specimens examined six or seven annulate setae, all of them bare).

Pereopod 5 ( Figure 6C )

As pereopod 3 except for: basis shorter than remaining articles together. Ischium with annulate setae only. Carpus 0.95 as long as merus, with eight annulate setae (most proximal one with a few setules, all of them bare in other specimens examined). Without exopod.

Uropod ( Figures 6D , 10E )

Peduncle approximately 1.2 times as long as the telson, with 15–16 cuspidate setae on inner margin (15–17 in other two specimens examined). Rami subequal. Endopod: article 1 slightly shorter than other two together, with four or five cuspidate setae on inner margin (four to seven in other specimens examined) and one simple seta on outer distal corner; article 2 slightly shorter than article 3, with two cuspidate setae on inner margin (two or three in other specimens examined) and one simple seta on outer distal corner; article 3 with three cuspidate setae on inner margin (three or four in other specimens examined), and one cuspidate seta and one simple seta distally. Exopod with simple setae on outer margin (only dorsal ones drawn) and four unequal simple setae distally.

Description of adult male

Based on the paratypes MACN-In. 37088c, d.

Total length

Approximately 7.0 mm.

Carapace ( Figures 7A, B ; 10C, D )

As in female except for: approximately 1.4 times as long as wide, anterior part of the oblique ridges bearing a few denticles, middorsal ridge more marked, horizontal ridge reaching posterior margin of carapace, pentagon narrower (side ‘‘a’’ approximately as long as side ‘‘b’’) and enclosed area not so deeply excavated, lenses larger, antero-lateral angle not projecting.

Thorax

As in female except for: postero-lateral angles of pereonite 5 strongly produced and acute.

Pleon

As in female.

Telson ( Figure 9C )

Approximately 1.5 times as long as last pleonite, with seven cuspidate setae on each side (eight in another specimen examined) and two divergent cuspidate setae (tips broken), stouter than lateral ones, distally.

Antenna 1 ( Figure 7C )

Peduncle, article 1 approximately 1.2 times as long as articles 2 and 3 combined, inner distal corner with three unequal setulate setae, outer distal corner with one simple seta arched over article; article 2 approximately 1.2 times as long as article 3. Main flagellum of six articles, article 1 thickest and with many aesthetascs (only two drawn), article 3 the longest, following articles becoming shorter towards distal end, articles 5 and 6 with one aesthetasc each. Accessory flagellum extending slightly beyond article 3 of main flagellum; of four articles, article 3 the longest.

Mouthparts and maxilliped 1

As in female.

Maxilliped 2 ( Figure 7D )

As in female except for: basis with a short ridge on outer margin. Both dorsal and ventral setae of basis were drawn, setae from remaining articles omitted.

Maxilliped 3 ( Figure 8A )

As in female except for: basis less arched and less setose. Exopod larger, flagellum of eight articles.

Pereopod 1 ( Figure 8B )

As in female except for: basis approximately 1.05 times as long as remaining articles together, setae on inner margin less abundant and shorter. Exopod larger, flagellum of nine articles.

Pereopod 2 ( Figure 8C )

As in female except for: basis, distal end much wider than ischium, setae on inner margin less abundant and shorter. Ischium and merus combined approximately 0.5 as long as carpus. Carpus with five serrulate setae distally. Exopod larger, flagellum of nine articles.

Last three pereopods

They differ mainly from those of the female in: bases of pereopods 3–5 stronger and less setose, exopods of pereopods 3 ( Figure 8D ) and 4 with nine-articulated flagella; carpus of pereopod 5 with fewer (six) annulate setae.

Pleopod 1 ( Figure 9A )

Peduncle, inner margin with five or six short setae (having setules basally and minute nodules distally) and four or five long setulate setae, anterior surface with a row of six or seven simple setae. Endopod of one article bearing two broom and six long setulate setae. Exopod of two articles, distal one with four long setulate setae.

Pleopod 2 ( Figure 9B )

As first except for: inner margin with four short setae only (similar to those of pleopod 1), anterior surface with a row of five to seven simple setae.

Uropod ( Figure 9C )

Peduncle approximately 1.3 times as long as telson, with 27–32 cuspidate setae on inner margin (26–28 in another specimen examined). Rami subequal. Endopod: article 1 as long as other two combined, with nine cuspidate setae on inner margin (9–11 in another specimen examined) and one simple seta on outer distal corner; article 2 as long as article 3, with seven cuspidate setae on inner margin and one simple seta on outer distal corner; article 3 with 10–11 cuspidate setae on inner margin (9–10 in another specimen examined), and one cuspidate seta and one simple seta distally. Exopod with simple setae on outer margin (only dorsal ones drawn) and four unequal simple setae distally.

Etymology

This species is named after Fabrizio Scarabino for kindly supplying us most of the specimens on which the description of this species is based.

Distribution

The specimens examined range from São Paulo State ( Brazil) to Río Negro Province ( Argentina) between 2 and 60 m depth.

Figures

Figure 2. Diastylis fabrizioi n. sp., ovigerous female (holotype MACN-In. 37087). A, lateral body view; B, dorsal body view. Ovigerous female (paratype MACN-In. 37088a). C, antenna 1 (accessory flagellum enlarged); D, antenna 2. Scale bars: 1 mm (A, B), 0.1 mm (C, D).

Figure 3. Diastylis fabrizioi n. sp., ovigerous female (paratype MACN-In. 37088a). A, right mandible (rudimentary lacinia mobilis and row of 12 setae enlarged); B, maxilla 1; C, maxilla 2 (endite and protopod marginal setae enlarged). Scale bars: 0.1 mm (A–C).

Figure 4. Diastylis fabrizioi n. sp., ovigerous female (paratype MACN-In. 37088a). A, maxilliped 1 (three carpus marginal setae, the basal endite, and the oval and crescent like endite setae are enlarged); B, maxilliped 2 (a propodal serrulate seta enlarged); C, maxilliped 3 (distal end enlarged). Scale bars: 0.1 mm (A, B), 0.5 mm (C).

Figure 5. Diastylis fabrizioi n. sp., ovigerous female (paratype MACN-In. 37088a). A, pereopod 1; B, pereopod 2. Scale bars: 0.5 mm (A, B).

Figure 6. Diastylis fabrizioi n. sp., ovigerous female (paratype MACN-In. 37088a). A, pereopod 3 (exopod and tip of dactylus enlarged); B, pereopod 4, C; pereopod 5; D, telson and uropod. Scale bars: 0.5 mm (A–D).

Figure 7. Diastylis fabrizioi n. sp., adult male (paratype MACN-In. 37088c). A, lateral body view; B, dorsal body view. Adult male (paratype MACN-In. 37088d). C, antenna 1; D, maxilliped 2 (setae of ischium–dactylus omitted). Scale bars: 1 mm (A, B), 0.1 mm (C, D).

Figure 8. Diastylis fabrizioi n. sp., adult male (paratype MACN-In. 37088d). A, maxilliped 3; B, pereopod 1; C, pereopod 2; D, pereopod 3. Scale bars: 0.5 mm (A–D).

Figure 9. Diastylis fabrizioi n. sp., adult male (paratype MACN-In. 37088d). A, pleopod 1 (most rami setae partially drawn); B, pleopod 2 (most rami setae partially drawn); C, telson (tips of distal setae broken) and uropod. Scale bars: 0.1 mm (A, B), 0.5 mm (C). A and B share the scale.

Figure 10. Diastylis fabrizioi n. sp., SEM photos. A, B, E, ovigerous female (paratype MACN-In. 37088b). A, lateral view of anterior part of the body; B, dorsal view of anterior part of the body (serration of oblique ridge enlarged); E, telson and uropodal peduncles (distal part of telson enlarged). C, D, adult male (paratype MACN-In. 37088e). C, lateral view of anterior part of the body; D, dorsal view of anterior part of the body. Diastylis planifrons Calman, 1912. F, preparatory female (MACN-In. 37089), dorsal view of anterior part of the body. Scale bars: 1 mm (A–D, F), 0.2 mm (E). A, B share the scale; C, D share the scale.