Borikenella spinosa, Guerra-García, José M., Chatterjee, Tapas & Schizas, Nikolaos V., 2015

Guerra-García, José M., Chatterjee, Tapas & Schizas, Nikolaos V., 2015, New genus and new species of Caprellidae (Crustacea: Peracarida: Amphipoda) from the mesophotic coral ecosystems of Puerto Rico and St. Croix, Caribbean Sea, Zootaxa 4018 (1) : -

Borikenella spinosa sp. nov.

( Figs. 1–6 )

Type material. Holotype, male 4.2 mm (used for drawings of lateral view, antennae, gnathopods, pereopods 3–4, mouthparts and abdomen) (vial and two slides, mouthparts dissected) (vial: MNCN 20.04/10061, slides: MNCN 20.04/10062, 20.04/10063) Abrir la Sierra, GPS coordinates N 18.76197, W –67.15696, W Puerto Rico, Caribbean Sea, 70 meters depth, 26 April 2012. All specimens, except paratype “a”, were collected during the 2012 Mesophotic Cruise organized by the Caribbean Coral Reef Institute ( CCRI) with the vessel Spree ( Sherman et al. 2013).

Paratype “a”, female 4.1 mm (used for drawings of lateral view, gnathopod 2, pereopods 3–7 and abdomen) (vial and one slide, mouthparts not dissected) (vial: MNCN 20.04/10064, slide: MNCN 20.04/10065), Weinberg, La Parguera, GPS coordinates N 17.890440 W -66.989020, SW Puerto Rico, Caribbean Sea, 45 meters depth, 13 March 2008.

Paratype “b”, male 3.6 mm (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10066, slide: MNCN 20.04/10067), Abrir la Sierra, GPS coordinates N 18.76197, W -67.15696, W Puerto Rico, Caribbean Sea, 70 meters depth, 26 April 2012.

Paratype “c”, female 3.3 mm (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10068, slide: MNCN 20.04/10069), Abrir la Sierra, GPS coordinates N 18.76197, W -67.15696, W Puerto Rico, Caribbean Sea, 70 meters depth, 26 April 2012.

Paratype “d”, female 2.9 mm (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10070, slide: MNCN 20.04/10071), Abrir la Sierra, GPS coordinates N 18.76197, W -67.15696, W Puerto Rico, Caribbean Sea, 70 meters depth, 26 April 2012.

Other paratypes (not dissected): 4 juveniles ( MNCN 20.04/10072, 20.04/10073, 20.04/10074, 20.04/10075), Weinberg La Parguera, GPS coordinates N 17.890440 W -66.989020, SW Puerto Rico, Caribbean Sea, 45 meters depth, 13 March 2008; 2 juveniles ( MNCN 20.04/10076, 20.04/10077), Bajo de Sico, GPS coordinates N 18.23075, W -67.43177, W Puerto Rico, Caribbean Sea, 50 meters depth, 28 April 2012; 2 females ( MNCN 20.04/ 10078, 20.04/10079), Tourmaline, GPS coordinates N 18.17530, W -67.32730, W Puerto Rico, Caribbean Sea, 54 meters depth, 29 April 2012.

Additional material examined. 5 females collected from Weinberg La Parguera, GPS coordinates N 17.890440 W -66.989020, SW Puerto Rico, Caribbean Sea, 45 meters depth, 13 March 2008; 2 males, 1 female, 1 juvenile collected from Salt River Canyon, St. Croix. U.S. Virgin Islands, GPS coordinates N 17.78689, W - 64.75856, Caribbean Sea, 70 meters depth, 4 May 2012; 1 male (immature), 3 females (premature), 1 juvenile collected from Hole-in-the-Wall, La Parguera, GPS coordinates N 17.88476, W -67.02192, SW Puerto Rico, Caribbean Sea, 90 meters depth, 8 June 2010.

Diagnosis. Eyes present. Head, pereonite 1, 6 and 7 smooth. Pereonites 2–5 with abundant projections. Gnathopod 1 with one grasping spine. Basis of gnathopod 2 shorter than pereonite 2. Propodus of gnathopod 2 triangular in males. Pereopod 3 and 4 three-articulate. Pereopod 5 (morphologically different to pereopod 6 and 7) six-articulate, elongate and provided with long setae; distal article reduce to a very small cone. Molar of the mandibles fully developed. Distal article of the mandibular palp provided with setae and small tubercle. Abdomen without appendages

Etymology. The specific name ‘ spinosa ’ indicates the abundant projections along the body in this species.

Description. Holotype male (4.2 mm)

Lateral view ( Fig. 1 ). Head rounded, lacking any projections, eyes present and distinctive. Pereonite 1 fused with head, suture present. Head and peronite 1 smooth. Pereonite 2 with a dorsal projection medially, two distal projections and a lateral projection near the coxa. Coxa of gnathopod 2 with a small acute projection ventrally. Pereonites 3 and 4 similar in size and shape provided with two ventral projections proximally and numerous projections dorsally. Some of these projections start from the same base. Pereonite 5 with two ventral projections proximally and two dorsal projections medially. Pereonite 5 the longest. Pereonite 7 the shortest.

Gills ( Fig. 1 ). Present at middle of pereonites 3–4, small and oval, length about 1.2 times width.

Mouthparts ( Fig. 2 ). Mandibles with trituritive molar, moderately developed and dentate marginally. Threearticulate palp; distal article of palp the longest, with a setal formula 1-x- 0, being x=4, with presence of small tubercules besides the setae, medial article provided with a single setae; left mandible with incisor and lacinia mobilis five-dentate, followed by three accessory blades; incisor of right mandible five-dentate, lacinia mobilis looking like a blade, followed by two more blades; no sign of molar flake. Lower lip without setae; inner lobes with rectangular margin. Maxilla 1 outer lobe carrying seven spines distally serrate, palp two-articulate, distal article with three apical spines and two medial seta. Maxilla 2 inner lobe small, shorter than outer lobe, both with four apical setae. Maxilliped inner plate small and rectangular, about 1/3 of outer plate in length, carrying two setae and a short and blunt spine; outer plate oval, with two apical setae and three medial setae; palp four-articulate, scarcely setose, distal article (dactylus) curved.

Antennae ( Figs. 1 and 3 ). Peduncle of antenna 1 of the same length that head and pereonites 1 and 2 combined; second article the longest; third article shorter than the articles of the flagellum; flagellum broken. Antenna 2 longer than peduncle of antenna 1; proximal peduncular article with a well developed acute gland cone distally; swimming setae absent; flagellum two-articulate.

Gnathopods ( Figs. 1 and 3 ). Gnathopod 1 basis of the same length than the combination of ischium, merus and carpus; grasping margin of propodus with minute setulae; one proximal grasping spine, dactylus bifid distally. Gnathopod 2 inserted on the anterior end of pereonite 2; basis shorter than pereonite 2, with a distal acute projection; ischium small rectangular; merus rounded; carpus short and triangular; propodus of gnathopod 2 unique, with triangle shape, palm slightly setose, with proximal projection provided with one large grasping spine, followed by denticulate margin, projection, U-notch and denticulate margin; dactylus smooth and elongate.

Pereopods ( Figs. 1 and 4 ). Pereopod 3 and 4 very reduced, three-articulate; proximal article the longest, second article rectangular with a seta and third article small and conical with a seta. Pereopod 5–7 described from the female paratype “a”.

Penes ( Fig. 5 ) large, situated laterally, distinctive, oval, length ca 2 times width.

Abdomen ( Fig. 5 ) without appendages, with two lateral globose lobes provided with bunches of setae and a single dorsal lobe provided with two plumose setae.

Paratype female “a” (4.1 mm) ( Figs. 1 , 3 , 4 , 5 )

Similar to the male except for the following characteristics: presence of oostegites on pereonites 3 and 4, both setose. Pereonite 3 and 4 with strong lateral acute projections. Gills more elongate than in males. Gnathopod 2 propodus elongate, without triangular shape, margin not denticulate. Lateral lobes of abdomen not globose, lacking setae.

Description of pereopods 5–7: Pereopod 5, morphologically different to pereopod 6 and 7, attached to the middle of pereonite 5, six-articulate, elongate and provided with long setae; distal article reduce to a very small cone; pereopod 6 and 7 attached to the posterior end of the pereonites, six-articulate, basis without carina, ischium short and rectangular, merus, carpus and propodus palm carrying row of robust setae, propodus with a proximal grasping spine, dactylus elongate. Pereopod 7 longer and more robust than pereopod 6.

Intraspecific variation. The morphological characteristics of the species are rather constant in all the specimens examined. The number or location of the dorsal and lateral acute projections can change depending on the specimens and along the developmental stage. Some specimens are provided with one or two small acute projections on the head ( Fig. 6 F, G). The first stages of development lack projections ( Fig. 6 A, B). Antennae 1 flagellum was broken in most of the specimens, but at least, five articles were maintained in some specimens. Mouthparts were similar in the four specimens dissected, and all of them showed the same formula in the mandibular palp, 1-x- 0, being x= 4 in most of specimens, with x=3 and x= 5 in some individuals. The number of articles of pereopods 3–7 did not change along the development, being always pereopods 3 and 4 three-articulate and pereopod 5–7 six-articulate. The size of females was variable, with some premature females being larger (3–4 mm) (e.g. Fig. 6 D) than some mature females with very reduced size (2–3 mm) (e.g. Fig. 6 F).

Remarks. Borikenella spinosa resembles externally some species of the genus Deutella (such as Deutella caribensis Guerra-García, Krapp-Schickel & Müller, 2006 ) or Aciconula , especially based on the weak pereopod 5, very elongated and provided with long setae. However, Borikenella and Deutella clearly differ in that Deutella furnishes abdominal appendages ( Guerra-García, 2003a), which are lacking in Borikenella . Aciconula is very closely related to Borikenella , but they differ in the number of articles of pereopods 3 and 4 and the shape and length of antennae and pereopods 5–7 (see Guedes-Silva & Souza-Filho, 2013). Although mouthparts are rather similar in both genera, the mandible molar is very small in most Aciconula species ( Guedes-Silva & Souza-Filho, 2013), while it is well developed in Borikenella ; the size and shape of maxilliped plates also differ significantly between these two genera. Borikenella is also similar to Pseudaeginella in the abdomen structure, but these two genera can be clearly distinguished in that Pseudaeginella lacks mandible molar ( Guerra-García et al., 2006). The abdomen (lacking appendages) is also similar in Paradeutella , but Borikenella can be differentiated from Paradeutella in that pereopods 3 and 4 are 3-articulate instead of 1-articulate in Paradeutella (see Laubitz, 1991); furthermore, the setal formula of the mandibular palp also differs, being 1-x- 1 in Paradeutella and 1-x- 0 in Borikenella . In fact, the formula 1-x- 0 is unique in caprellids, since they usually have one long seta followed by one or two rows of shorter setae and another long seta (formulas 1-x- 1 or 1-x-y-1) or there are only one or two apical setae. But the presence of a long seta, followed by a row of setae and lack of another long seta on the mandibular palp is a synapomorphy of the new genus Borikenella .

Figures

FIGURE 1. Borikenella spinosa gen. nov., sp. nov. Lateral view of holotype male, 4.2 mm, and paratype female “ a ”, 4.1 mm.

FIGURE 2. Borikenella spinosa gen. nov., sp. nov. Mouthparts of holotype male, 4.2 mm.

FIGURE 3. Borikenella spinosa gen. nov., sp. nov. Antennae, gnathopod 1 and 2 of holotype male, 4.2 mm. Gnathopod 2 of paratype female “ a ”, 4.1 mm.

FIGURE 4. Borikenella spinosa gen. nov., sp. nov. Pereopods 3 and 4 of holotype male, 4.2 mm. Pereopods 3 – 7 of paratype female “ a ”, 4.1 mm.

FIGURE 5. Borikenella spinosa gen. nov., sp. nov. Abdomen of holotype male, 4.2 mm, and paratype female “ a ”, 4.1 mm.

FIGURE 6. Borikenella spinosa gen. nov., sp. nov. Variation in size and body projections. A, B: juveniles; C: immature male; D, E: premature females; F-H: mature females.