Fragillianassa joeli, Pachelle & Tavares, 2020

Pachelle, Paulo P. G. & Tavares, Marcos, 2020, Axiidean ghost shrimps (Decapoda: Axiidae, Callianassidae, Callichiridae Micheleidae) of the Trindade and Martin Vaz Archipelago, Vitória-Trindade Seamounts Chain and Abrolhos, off southeastern Brazil, Zootaxa 4758 (1), pp. 103-126 : 106-115

publication ID	https://doi.org/ 10.11646/zootaxa.4758.1.4
publication LSID	lsid:zoobank.org:pub:ACDCF67F-93FA-40DE-AF1C-B6E4E0707E72
DOI	https://doi.org/10.5281/zenodo.3812871
persistent identifier	https://treatment.plazi.org/id/D475EA1F-FF87-FF94-AFC5-F95FFB426677
treatment provided by	Plazi
scientific name	Fragillianassa joeli
status	sp. nov.

Treatment

Fragillianassa joeli View in CoL sp. nov.

( Figures 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Trindade specimens. Male holotype, cl 3.9 mm ( MZUSP 36412), Brazil, off Espírito Santo, Trindade Island, Enseada das Orelhas, 20º29’40.2’’S– 29º20’32.9’’W, 9.7 m depth, coll. J.B. Mendonça Jr, 15.v.2012. Juvenile paratype, cl 2.5 mm ( MZUSP 36413 View Materials ), Ponta Norte, 20º29’18.7’’S– 29º20’18.3’’W, 14.2 m depth, coll. J.B. Mendonça Jr, 02.vii.2015 GoogleMaps .

Comparative material examined. Fragillianassa fragilis ( Biffar, 1970) : 1 male, cl 4.4 mm ( MZUSP 33145),

USA, Florida, Fort Pierce, Little Jim bridge, low tide, burrow, coll. A. Anker et al., 24.vii.2009 . 1 male, cl 5.6 mm ( MZUSP 33146 View Materials ) , Mexico, Yucatán, Mahahual , backreef platform, low tide, burrow among seagrass and rocks, coll. A. Anker et al., 06.vi.2010 . 1 male, cl 3.8 mm ( MZUSP 27910 View Materials ) , Brazil, Pernambuco, Laguna de Suape , coll. S.A. Rodrigues, 25.ix.1965 . 1 male, cl 4.6 mm, 3 females, cl 3.4–4.2 mm ( MZUSP 39505 View Materials ) , Bahia, Boipeba Island, Bainema reef, coll. M. Tavares et al., 17–31.i.2015 .

Distribution. Currently known only from the type locality.

Description of male. Carapace surface smooth, margins fringed with simple setae, dorsal oval and linea thalas-

sinica present. Rostrum broadly triangular, short. Infraorbital angles of carapace unarmed, distally blunt. Ocular peduncles subcylindrical, overreaching distal margin of basal article of antennular peduncle, distomesial angle produced anteriorly. Cornea on distolateral region of peduncle, unpigmented, ocular pigments clustered on median region of peduncle, observed by transparency ( Figure 2 View FIGURE 2 ).

Antennular peduncle longer and wider than antennal peduncle. Basal article obscured by ocular peduncles dorsally. Median article about twice as long as wide, fringed with setae laterally. Distal article longest, about 2.5 times as long as median article, fringed with setae on lateral margins ( Figure 2D View FIGURE 2 ).

Antennal peduncle with semicircular, vestigial scale on dorsal margin and triangular, articulated plate on lateral margin of basal article. Median article slightly longer than distal one ( Figure 2A, D View FIGURE 2 ).

Mandible with incisor process squarish, margin with about 12 minute denticles. Molar process with 2 strong triangular teeth distally, medial margin with few minute denticles. Palp triarticulated, basal and medial articles of about same length, distal article longest, about twice as long as median article, fringed with stiff setae dorsally ( Figure 3A, B View FIGURE 3 ).

Maxillule with basal endite broad, dorsal angle produced into long lobe, fringed with stiff setae. Coxal endite expanded distally, fringed with stiff setae. Palp long, slender, tip curved, hook-shaped ( Figure 3C View FIGURE 3 ).

Maxilla with basal endite bilobated, margins fringed with setae, lower lobe broader than upper lobe, with additional small, setose lobe near intersection with coxal endite. Coxal endite bilobated, margins fringed with setae, upper lobe broader than lower lobe. Palp long, directed towards inner surface of maxilla, wider at base, tip curved, hook-shaped. Scaphognatite broad, fringed with plumose setae ( Figure 3D View FIGURE 3 ).

Maxilliped 1 endite pediform, fringed with setae. Endopod hammer-shaped, expanded distally, fringed with plumose setae, with additional small, setose lobe near intersection with endite. Exopod longer than endopod, tapering distally, margins smooth ( Figure 3E View FIGURE 3 ).

Maxilliped 2 with 4-articulated endopod, margins fringed with long setae. First article longest, about 3 times as long as wide. Second article shortest. Third article about twice as long as wide. Fourth article slightly longer than second one. Exopod overreaching mid-length of first segment of endopod, margins fringed with plumose setae. Coxa with rounded, setose lobe near exopod ( Figure 3F View FIGURE 3 ).

Maxilliped 3 operculiform, ischium and merus much wider than carpus, propodus and dactylus, margins fringed with long setae. Ischium slightly longer than wide, crista dentata low, teeth spaced, diminishing in size towards articulation with basis. Merus about 0.7 times as long as wide, distal margin almost straight, not produced beyond carpo-meral articulation. Carpus, propodus and dactylus about the same length. Carpus and propodus each with curve, transverse row of setae on mesial margin near propodo-carpal articulation. Exopod absent ( Figure 3 View FIGURE 3 G–I).

Pereopods 1 highly asymmetrical. Major pereopod 1 massive. Ischium smooth, slightly shorter than merus. Merus with lower margin rugose, proximal half produced into rectangular, rugose, distally acute tooth. Carpus about as long as wide, about 0.6 times as long as propodus, proximal margin broadly rounded. Palm about as long as dactylus, distolateral margin with rounded tooth near articulation with dactylus, obscured by 2 dense tufts of setae, proximomesial surface with strong tubercle. Fixed finger shorter than dactylus, smooth, with dense tufts of setae on proximal half, near base. Dactylus curved distally, lateral and mesial margins with dense tufts of setae, cutting edge with proximal and distal halves separated by wide hiatus, proximal half with large, squared tooth with U-shaped notch ventrally, distal half with 4 teeth, proximal pair much larger than distal pair. Minor pereopod 1 merus smooth, unarmed, slightly shorter than ischium. Carpus elongated, at least 3 times as long as wide. Palm approximately as long as fingers. Fingers cutting edges smooth, tips corneous ( Figure 4A, B View FIGURE 4 , 5 View FIGURE 5 A–C).

Pereopod 2 ischium shorter than half merus length. Merus about 2 times as long as wide, ventral margin with fringe of long setae. Carpus broadened distally, as long as chela, ventral margin with long setae. Palm short, about 1/3 of fingers length. Fingers with tufts of setae, cutting edges smooth ( Figure 6A View FIGURE 6 ).

Pereopod 3 ischium about half of merus length. Merus slightly longer than carpus, medially wider. Carpus produced distoventrally, distoventral margin fringed with long setae, distodorsal region with transverse row of long setae. Propodus slightly longer than carpus, proximal margin broadly rounded, distoventral margin with cuspidate seta, dorsal and ventral margins fringed with long setae, lateral surface with dense tufts of short setae. Dactylus ovate, as long as broad, tip corneous, surface covered with long setae ( Figure 6B View FIGURE 6 ).

Pereopod 4 ischium almost as long as merus. Merus longer than carpus. Carpus almost 3 times as long as wide. Propodus about twice as long as wide, lateral margin with transverse rows of setae, ventral margin fringed with long setae, more densely spaced on distoventral region. Dactylus long, about 2/3 of propodus length, tip corneous, surface covered with long setae ( Figure 6C View FIGURE 6 ).

Pereopod 5 short, about 1/3 of merus length. Merus slender than carpus, about 4 times as long as wide. Carpus about 2.5 times as long as wide. Propodus broadened distally, about 1.8 times as long as wide, with dense fringe of long setae on lateral margin. Fingers triangular, much shorter than palm, cutting edges obscurely toothed, dactylar finger longer than propodal finger ( Figure 6D, E View FIGURE 6 ).

Pleon smooth. Pleonite 1 as long as pleonite 3. Second somite longest. Fourth somite shortest. Fifth somite slightly shorter than sixth somite. First somite with short row of setae on proximal region of dorsal margin. Second to fourth somites each with 2 rows of setae on distoventral region. Fifth pleonal somite with transverse row of setae on proximoventral region, distoventral margin with fringe of setae. Sixth pleonal somite with fringe of setae along ventral margin, distal margin with tufts of long setae on distal, distodorsal and distoventral angles ( Figure 7A View FIGURE 7 ).

Pleopod 1 uniramous, biarticulate. Pleopod 2 lacking. Pleopods 3–5 biramous, endopod shorter than exopod, margins fringed with plumose setae, appendix interna stubby, projecting, inserted on proximal half of endopod ( Figure 7A, D, E View FIGURE 7 ).

Telson subquadrate, slightly longer than wide, surface with shallow longitudinal depression medially, transverse row of setae on proximal fourth of telson length, distolateral surface each with row of long setae. Posterior margin with shallow median sinus, posterolateral margins each with pair of minute cuspidate setae ( Figure 7B, C View FIGURE 7 ).

Uropod with protopod squarish, angles rounded, lateral margin with few setae. Endopod widening distally, fringed with plumose setae. Exopod wider and slightly longer than endopod, fringed distally with plumose and cuspidate setae, lateral margin with fringe of simple setae; dorsal plate not reaching distal margin of exopod, furnished distally with cuspidate setae; proximomesial region with dagger-like plate, latter with small sharp tooth medially ( Figure 7F View FIGURE 7 ).

Etymology. This species is named after our colleague and friend, marine biologist Joel Braga de Mendonça Jr.

Distribution. Brazil, off Espírito Santo, Trindade Island (currently known only from the type locality).

Remarks. Fragillianassa joeli n. sp. is herein assigned to Fragillianassa , whose diagnostic characters (cf. Poore et al. 2019) are readily recognized in the new species. They are as follow: antennular peduncle length about 2.5–3 times the width of both eyestalks ( Figure 2D View FIGURE 2 ); maxilliped 3 dactylus ovate, with dense brush of long setae over most of upper-distal margin, few setae along lower margin ( Figure 3G View FIGURE 3 ); and male major cheliped merus with prominent truncate hook armed with serrations along lower margin, excavate laterally at base, with deep notch at base of fingers ( Figures 4A View FIGURE 4 , 5A View FIGURE 5 ).

Among the 2 species currently assigned to Fragillianassa (viz., Poore et al. 2019), the closest morphological resemblance of F. joeli sp. nov. is with F. fragilis , which resembles F. joeli sp. nov. in the relative length between the distal antennular and antennal articles, the long carpus (about 4.5 times as long as wide) and unarmed merus of the minor pereopod 1 ( Figure 4B View FIGURE 4 ). However, adults of F. joeli sp. nov. and F. fragilis can be distinguished from each other by the morphology of the major pereopod 1, whose proximomesial surface of the palm is provided with a very strong, anteriorly ridged flange ( Figures 5 View FIGURE 5 A–C) (vs. palmar protuberance very low in F. fragilis , even in specimens larger than the holotype of F. joeli n. sp., Figures 5 View FIGURE 5 D–H; see also Biffar, 1970: fig. 3i). Fragillianassa joeli sp. nov. further differs from F. fragilis in having a weaker and obscurely serrated meral tooth and a distinctly more slender merus, 2.4 times as long as wide (vs 1.9 times as long as wide in F. fragilis ) ( Figures 4A View FIGURE 4 , 5 View FIGURE 5 D–F, I), and in that the antennular peduncle clearly overreaches the antennal peduncle in F. joeli sp. nov. ( Figure 2D View FIGURE 2 ), whereas in F. fragilis it barely overreaches the antennal peduncle ( Biffar 1970: fig. 3k).

The male holotype of F. joeli sp. nov. is much larger than the juvenile paratype, and the differences in the proportions and armature between their major pereopods 1 ( Figure 4A, C, D View FIGURE 4 ) are, therefore, assignable to changes during ontogeny. The very strong, anteriorly ridged flange in the proximomesial surface of the palm, characteristic of the adult ( Figures 5 View FIGURE 5 A–C), is yet undeveloped in the juvenile paratype.

In F. joeli sp. nov. the major pereopods 1 are placed on the left side of the body, whereas in most male specimens of F. fragilis examined it is on the right side ( Figure 5A View FIGURE 5 , D–F, I); see also the right-handed male illustrated in Biffar 1970: fig. 3i). However, it is not clear whether the handedness of the major pereopod 1 is a consistent character to separate F. joeli sp. nov. from F. fragilis .

Fragillianassa fragilis is a western Atlantic species previously known from southern Florida and the Caribbean Sea ( Puerto Rico, Antigua and Caribbean coast of Venezuela). Its record from the Pacific of Costa Rica by Vargas & Cortès (1999) actually refers to F. debilis (viz. Dworschak 2013). Fragillianassa fragilis was recently recorded from northeastern Brazil (Pernambuco) by Botter-Carvalho et al. (2012). The Brazilian specimens received register numbers from the MZUSP, but were not found there for further investigation.

The very strong palmar flange ( Figures 5 View FIGURE 5 A–C) also differentiate F. joeli sp. nov. from F. debilis , which additionally differ from each other in that the antennular distal article reaches slightly beyond the antennal distal article in F. joeli sp. nov. ( Figure 2D View FIGURE 2 ), whereas it is much longer than the antennal distal article in F. debilis (see Hernández- Aguilera 1998: fig. 1e).

Fragillianassa debilis is so far known from the Pacific coasts of Mexico (Revillagigedo Archipelago) and Costa Rica (Golfo de Nicoya) ( Dworschak 2013; Hernández-Aguilera 1998; Vargas-Zamora et al. 2019).