Booralana nickorum Shipley and Brooks, 2024

Bruce, Niel L., Rawlins, Scott, Gutierrez, Robert, Brendan, Mackellar Violich & Schneider, Eric Vc, 2024, A new species of deep-sea Booralana Bruce, 1986 (Crustacea: Isopoda: Cirolanidae) from The Bahamas, Western North Atlantic, Zootaxa 5399 (3), pp. 254-264 : 256-262

Booralana nickorum Shipley and Brooks sp. nov.

Material examined.

All material from northeast Exuma Sound, The Bahamas, western North Atlantic.

Holotype: 1 ♁ (55 mm), 24°50.96 N, 76°23.85 W; 7 February 2019; Atlantic Ocean, Northeast Exuma Sound, approximately 5.5km west of Cape Eleuthera, Eleuthera, The Bahamas; depth: 540–560m, temperature: 15ºC, non-baited light trap, Carnegie Museum of National History ID: 39,239 .

Paratypes: 3 ♁ (61–76mm), 24°50.96 N, 76°23.85 W; 7 February 2019; Atlantic Ocean, Northeast Exuma Sound , approximately 5.5km west of Cape Eleuthera, Eleuthera, The Bahamas; depth: 540–560m, temperature: 15ºC, non-baited light trap ; 1 ♀ (70mm), 24°48.08 N, 76°21.17 W; 14 April 2014, Atlantic Ocean, Northeast Exuma Sound , approximately 5.5km West of Cape Eleuthera, The Bahamas; depth = 656m, temperature: 11ºC, baited eel trap, Carnegie Museum of National History ID: 39,240 .

Diagnosis: Pleotelson subtriangular, apex narrowly rounded, acute; uropodal exopods with dense setae extending well beyond base of pleotelson. Pleopods 3 and 4 lacking prominent angle at midpoint of ramus.

Description of holotype male: Body 2.6 times as long as greatest width ( Fig. 2A, B , Fig. 3A ). Cephalon slightly less than twice as wide as long, round anteriorly, median part of posterior margin slightly concave in dorsal view, only slightly embedded in pereonite 1. Eyes almost completely obscured by cephalon in dorsal view; each eye approximately 1/3 length of anterior margin of cephalon ( Fig. 3B ). Anterior margin of cephalon with 3 narrow, sinuous carinae, dorsal most carina running along dorsal margin in contact laterally with dorsal margins of eyes; second carina more pronounced and confined to interocular region; third carina in contact laterally with ventral margin of eyes, curving dorsally around antennae, extending posteriorly beyond midpoint of eyes ( Fig. 3B ).

Pereonite 1 anteroventral margin sub-acute, produced anteriorly beyond posterolateral margin of the eye; lateral margin with marginal carina ( Fig. 3C ). Pereonites 2 and 3 coxal plates sub-rectangular with pronounced marginal carina. Pereonites 4–7 coxal plates well developed, produced posteriorly into strong, acute lobes. Pereonite 7 posterior margin with single row of small tubercles or granules ( Fig. 3C ). Pleonite 3 ventrolateral margin strongly produced, with deep posterior notch; posterolateral margin above notch produced posteriorly extending just beyond posterior ventrolateral margin of pleonite 5. Pleonites 2–5 posterior margins each with single row of small tubercles ( Fig. 3D ).

Antenna 1 extending posteriorly slightly beyond lateral margin of cephalon; peduncle not reaching beyond distal half of peduncle segment 4 of antenna 2; segment 3 approximately equal to combined lengths of segments 1 and 2; flagellum with 27 articles ( Fig. 3F ). Antenna 2 peduncular articles 1–3 with combined lengths subequal to that of segments 4 and 5; flagellum with 73–75 articles; flagellum extending posteriorly as far as pereonite 5. Frontal lamina anterior half subpentagonal, widest posteriorly, with median carina and raised lateral margins; posterior half subcircular produced anteriorly, highly punctate with rounded posterior margin ( Fig. 3F, G ).

Pereopod 1 dactylus with dark, corneous unguis; propodus flexor margin with 5 blunt tubercles, distal margin of each tubercle armed with secondary, short, acute spine; carpus short, inserted into merus ( Fig. 4A ); merus deeply notched laterally, with well developed, anteriorly directed pad on the flexor margin extending almost to distal margin of carpus, pad armed with 10 short RS laterally, and 6 blunt tubercles medially, tubercles similar to those on propodus, dorsal extensor margin lacking RS; ischium dorsal extensor margin with 2 – 3 setae, lacking RS ( Fig. 4B ). Pereopods 2–3 similar; dactylus and propodus similar to those of pereopod 1 but more slender; carpus inserted into shallow notch of merus, distal flexor margin armed with 3 RS, with 4 smaller RS set between; merus with pad on flexor margin not extending to distal margin of carpus, pad armed with 9 short RS laterally, 1–3 medial tubercles, dorsal flexor margin armed distolaterally with 3 prominent RS and 3–5 smaller RS; extensor margin of ischium with 2 smaller RS; flexor margin armed with 4–5 small RS ( Fig. 4C ). Pereopods 4–5 similar; propodus with 3 acute RS, often paired, along distal half of flexor margin; carpus well developed, length subequal to merus, distolateral margin with 10–12 stout RS, ventromedial margin with row of 4–6 RS, medial flexor margin armed with 2–3 smaller RS; merus with 12 prominent RS along distal margin, irregular row of 3–5 RS on flexor margin; ischium with 3–5 RS on distal extensor margin and 7–9 RS on distal flexor margin, ventral margin with 3 clusters of short RS at approximately ¼, ½, and ¾ length of margin. Pereopods 6–7 similar to pereopods 4–5, but much longer and with more RS ( Fig. 4D ).

Pleopod 1 exopod with medial margin rounded, tapering to narrow, rounded distal end; lateral margin straight; plumose setae restricted to distal 1/3 of margin becoming more prominent posteriorly ( Fig. 5A ); endopod lateral and medial margins subparallel, distal margin broadly rounded, setae restricted to distal margin. Pleopod 2 endopod and exopod subequal in length, broadly rounded distally ( Fig. 5B ); exopod with plumose setae restricted to distal margin; endopod with fine pubescence running along posterior margin to insertion point of appendix masculina; appendix masculina originating at base of endopod, styliform, unornamented, not extending beyond tip of endopod ( Fig. 5B ). Pleopods 3 and 4 similar exopod broadly rounded distally, with weak indication of suture; plumose setae restricted to distal margin; endopod with lateral margin evenly rounded, medial margin straight proximally, lacking prominent angle at midpoint of ramus; distal margin rounded ( Fig 5C, D ). Pleopod 5 endopod and exopod subequal in length, exopod broadly rounded distally, with weak indication of suture; plumose setae restricted to posterior margin, distal margin rounded ( Fig. 5E ). Penes short, subrectangular ( Fig. 5F ).

Pleotelson 1.3 times as wide as long, anterolateral margin concave at junction with uropod; lateral margins slightly raised, convex, converging toward apical posterior margin; posterior margin pointed ( Fig. 5E ); dorsal surface with one pair of long submedian carinae extending entire length of pleotelson, posteriorly narrow, widening anteriorly and becoming less distinct; one median carina originating just below anterior margin of pleotelson, extending to posterior margin.

Uropod basis posteromedial process extending half-length of endopod, bearing short plumose setae along distal 1/3 of medial margin, with dorsal transverse carina ending laterally at junction with rami ( Fig. 5H, I ). Exopod lanceolate, narrow, approximately 4½ times as long as wide, and approximately 1.4 times length of the endopod extending well below base of pleotelson, tapering to subacute tip. Endopod narrow proximally, broadest distally, posterior margin truncate, very slightly sinuous, almost straight, shorter than pleotelson. Lateral and distal margins of both rami fringed with dense clusters of long plumose setae, distal half of inner margins fringed with plumose setae thinning anteriorly ( Fig. 5H, I ).

Mouthparts: Mandibles as for others of the genus ( Fig. 6A ); palp ( Fig. 6B ) article 2 distolateral half with mass of dense long setae, palp article 3 with c. 40 long setae, palp article 2 mesial margin with 12 slender setae, lateral margin distally with 20 slender setae; article 3 mesial margin with 12 slender setae, lateral margin with 19 slender setae; article 4 mesial margin with 11 slender setae, lateral margin with 8 slender setae; article 5 mesial margin 10 setae, lateral and distal margin with 9 setae; endite 2 coupling setae and 10 plumose slender setae. Maxillula mesial lobe with 3 large circumplumose RS; lateral lobe with 12 RS. Maxilla ( Fig. 6C ) lateral lobe with 6 long setae; middle lobe with c. 20 long setae; mesial lobe with c. 30 distal long and short setae. Maxilliped ( Fig. 6D, E )

Females: In females, setae present on posterior margins of uropodal exopod less dense than that of males.Presence of brood pouches on ventral surface of pereon can be used to distinguish mature from juvenile specimens.

Immature: Setation of uropods in young is much less dense than that of the adults. Maturity of females can be inferred by the presence of pouches on ventral surface of pereon.

Etymology: This epithet nickorum sp. nov. honours two members of the senior author’s family, the late Nicholas Brooks and his grandson who shares both his name, as well as his inquisitive nature and love of wild things and places.

Remarks: Booralana nickorum sp. nov. differs from Booralana tricarinata by the posteriorly narrowed pleotelson apex, which is in strong contrast to the broadly truncate in the latter species. While the Australian species will not co-occur with any Atlantic species, it is again characters of the pleotelson that provide ready identification. Booralana bathynella has a broad subtruncate pleotelson that entirely lacks carinae, while in Booralana wundurra the pleotelson has sinuate lateral margins that converge to a narrowly truncate and upturned apex (in adult males).

Figures

FIGURE 2. Booralana nickorum sp. nov. holotype male captured from the northeast Exuma Sound, The Bahamas, A, dorsal view, B, ventral view.

FIGURE 3. Booralana nickorum sp. nov. holotype male captured from the Exuma Sound Bahamas.A, dorsal view; B, anterior view; C, lateral view; D, pleon and coxal plates; E, antenna and antennules; F, clypeus.

FIGURE 4. Booralana nickorum sp. nov. holotype male captured from the Exuma Sound Bahamas.A, pereopod 1; B, pereopod 1 merus; C, pereopod 2; D, pereopod 7.

FIGURE 5. Booralana nickorum sp. nov. holotype male captured from the Exuma Sound Bahamas. A, pleopod 1; B, pleopod 2; C, pleopod 3; D, pleopod 4; E, pleopod 5; F, penes; G; pleotelson; H, uropod; ventral, I; uropod, dorsal.

FIGURE 6. Booralana nickorum sp. nov. holotype male captured from the Exuma Sound Bahamas. A, mandible; B, palp; C, maxilla; D, maxilliped 1; E, maxilliped 2.