Bathytanais culterformis, Larsen & Heard, 2001

Larsen, Kim & Heard, Richard W., 2001, A new tanaidacean subfamily, Bathytanaidinae (Crustacea: Paratanaididae), from the Australian continental shelf and slope, Zootaxa 19, pp. 1-22 : 3-7

Bathytanais culterformis n. sp. ( Figs. 1 & 2 )

Material examined. – Holotype: Non­ovigerous female, P61355, body length 3.2 mm, Sta. SO5­83­B2 , 19º56,7’S. 117º53,6’E. Depth 41 m . Paratypes: 2 non­ovigerous females, P61356, same locality. Collected by staff on board RV “Soela” CSIRO 1983 .

Other material: 12 Non­ovigerous female, P54288, same locality . 5 females, P52195, Sta. No. SO3­83­B2 , Lat. 19º56.4'S, Long. 117º53.9'E. Depth 44 m . 1 female, P52213, Sta. No. SO6­82­B4 , Lat. 18º56.6'S, Long. 118º44.9'E. Depth 88 m . 2 females, 1 manca, P52211, Sta. No. SO6­83­B1, Lat. 19º03.0'S, Long . 119º02.4'E. Depth 80 m . 1 female, P52198 Sta. No. SO3­83­D9, Lat. 19º58.0'S, Long . 117º49.7'E. Depth 43 m . 7 females, P52199, Sta. No. SO4­83­B2, Lat. 19º56.7'S, Long . 117º53.8'E. Depth 42 m . 1 female, P04972. Sta. No. SO3­83­B7 , Lat. 19º30.8'S, Long. 118º49.1'E. Depth 38 m . 1 female, P52191, SO2­83­B12, Lat. 19º56.9', Long . 117º53.7'E. Depth 43m . 1 female, P52378, Sta. No. SO3­83­B8 , Lat. 19º29.2'S, Long. 118º52.5'E. Depth 41 m.

Diagnosis: Antenna with article 2 subquadrate, ventral margin blade­like, not serrated, slightly concave; disto­ventral margin subacute, with several setae. Article 3 of antenna not deeply recessed into article 2, with disto­dorsal and disto­ventral margins each produced into acute process. Labium with distal denticulated scales. Uropodal exopod almost as long as endopod.

Description (adult female)

Body ( Fig. 1 A): Slender, sub­cylindrical, approximately 9 times longer than broad.

Cephalothorax ( Fig. 1 B): Length near length of pereonite 1 and 2 together, width 0.75 length. Eye lobes acute.

Pereonites: Pereonite 1 wider than long. Pereonites 2­4 and 6, length subequal to width. Pereonite 5 longer than wide.

Pleon: Pleonites 1­5 similar in length and width, width approximately 4.0 length, all with 1 heavy articulated circumplumose seta. Pleotelson twice as long as last pleonite.

Antennule ( Fig. 1 C): Longer than cephalothorax. Article 1 longer than rest of antennule, with several setules on outer margin. Article 2 longer than article 3, distal margin with 2 long simple setae and several setules. Article 3 length one quarter of article 4, with 1 simple and long setulated seta. Article 4 longer than article 2, with 1 simple and 5 distal setulated setae twice as long as antennule.

Antenna ( Fig. 1 D): Length three quarters that of antennule. Article 1 lost. Article 2 with smooth ventral margin of the ventral expansion, distal ventral row of simple setae, 1 simple distal dorsal seta. Article 3 less than half as long as article 2, with dorsal spiniform seta and distal anteriorly directed ventral projection. Article 4 longer than article 3, with 1 long serrated distal seta on ventral margin and 3 short sensory setae. Article 5 as long as article 4, with 1 setulated distal seta of more than twice the length of the antennae. Article 6 minute with 3 setulose setae longer than antenna, 2 long and 1 short simple setae.

Mouthparts: Labrum ( Fig. 1 E) flat, setose apex. Mandibles ( Figs. 1 G & F) molar longer than incisor, left mandible with strongly defined lacina mobilis with several denticulations, incisor unidentate, right mandible with broad and bidentate incisor. Maxillule ( Fig. 1 I) with 7 thick terminal setae and dorsal row of setae, palp shorter than endite. Maxilla ( Fig. 1 I) ovoid. Labium ( Fig. 1 H) with setules on anterolateral corners and distal denticulated scales. Maxilliped ( Fig. 1 J) endites with 1 seta on inner corner and 2 medial short flat setae; palp article 1, outer margin longer than inner, smooth; article 2, inner margin longer than outer, with 3 setulated setae on inner distal margin, 1 short simple seta on outer distal margin; article 3, 4 setulated setae on inner margin; article 4 rectangular, inner margin with 5 setulated distal setae and several fine setules, outer margin with 1 setulated seta. Epignath ( Fig. 1 K) with blunt finely setose apex.

Cheliped ( Fig. 1 L): Basis smooth, twice as long as wide. Merus ovoid, with 1 simple seta medially on ventral margin. Carpus oval, longer than basis, with 2 simple setae on ventral margin, 1 distal seta on dorsal margin. Propodus with row of serrated dorsal setae by dactylus insertion. Fixed finger with strong tip, 2 simple setae on ventral margin, 3 on cutting edge and 1 at dactylus insertion. Dactyl narrow, with 1 seta on its dorsal margin.

Oostegites: originating from pereonites 1­4.

Pereopod 1 ( Fig. 2 A): Longer than other pereopods. Coxa with simple seta. Basis as long as combined length of 3 succeeding articles, smooth. Ischium with 2 simple setae on ventral margin. Merus longer than carpus, with 2 simple distal setae on ventral margin. Carpus with 3 simple distal setae. Propodus twice as long as long as carpus, tapering distally, with 3 simple distal seta. Dactyl and terminal spine not fused, together longer than propodus.

Pereopod 2 ( Fig. 2 B): Similar to pereopod 1 except: Basis as long as combined length of 4 succeeding articles. Merus expanding distally, with 2 simple distal setae on ventral margin, shorter than carpus. Carpus with 2 simple setae on ventral margin. Propodus with 3 simple distal seta.

Pereopod 3 ( Fig. 2 C): Similar to pereopod 2 except: Coxa smooth. Merus with 1 simple distal seta. Carpus marginally longer than merus, with 1 distal simple seta. Propodus with 2 simple distal setae.

Pereopod 4 ( Fig. 2 D): Basis stout and smooth. Ischium smooth. Merus shorter than carpus, with 2 short denticulated distal setae and denticulated scales. Carpus shorter than propodus, with denticulated scales, 1 simple and 2 short denticulated distal setae. Propodus with 1 sensory seta on dorsal margin, 1 long serrated and 2 spiniform setulose distal seta. Dactyl and terminal spine fused into a claw with setules.

Pereopod 5 ( Fig. 2 E): As pereopod 4, except: Basis with 1 simple and 1 sensory setae on ventral margin. Ischium with 2 simple setae. Merus with few denticulated scales, 1 simple, 3 stout spiniform distal setae. Carpus as long as propodus with denticulated scales and 3 spiniform setulated distal setae.

Pereopod 6 ( Fig. 2 F): As pereopod 5 except: Basis with 1 simple ventral seta. Merus as long as carpus, with 2 short stout distal setae. Propodus without sensory seta but with 3 stout setulated distal setae as long as dactylus.

Pleopods ( Fig. 2 G): All 5 pairs similar. Protopod trapezoidal. Exopod armed with 19 plumose setae. Endopod, inner margin finely setose, with 15 plumose setae, 2 distal setae shorter and stouter than rest.

Uropods ( Fig. 2 H): Protopod rectangular, with 1 simple seta. Endopod with incomplete fusion of articles, with 2 sensory setae midlength, 5 simple and 2 sensory distal setae. Exopod with 1 article, almost as long as endopod, with 1 simple seta midlength, 2 long simple distal setae.

Male: unknown

Etymology: Named for the cleaver­like ventral edge on article 2 of the antennal peduncle (Latin: Culter­formis = Cleaver­like).

Habitat: Specimens living in sandy bottom at 41m depth on the Northwest Australian shelf off Western Australia. Specimens were found in tubes consisting of sand grains and mucus.

Remarks: Bathytanais culterformis can be immediately distinguished from the other known members of the genus by the subquadrate shape of antennal article 2, which has blade­like, slightly concave, ventral margin produced into a relatively subacute distal process. The proximal ventral margin abruptly turns upward to the articulation with article 1, forming a subacute ventro­proximal process. Bathytanais culterformis , B. bipennifer and B. bathybrotes (as described by Lang, 1972) are the only known species of the genus to have both a dorsal and a ventral distal process on antennal article 3, but those on the two first species are acute and those on the latter are rounded or lobate. The other four species lack a dorsal process. The smooth ventral margin on the antenna article 2 ventral processes separates B. culterformis from B. bipennifer , which has a serrated margin.

Figures

FIGURE 1. Bathytanais culterformis, female. A holotype, B­L dissected paratype. A) Dorsal view. B) Cephalothorax. C) Antennule. D) Antenna. E) Labrum. F) Left mandible. G) Right mandible. H) Labium. I) Maxillule and maxilla. J) Maxilliped. K) Epignath. L) Cheliped.

FIGURE 2. Bathytanais culterformis, female paratype. A) Pereopod 1. B) Pereopod 2. C) Pereopod 3. D) Pereopod 4. E) Pereopod 5. F) Pereopod 6. G) Pleopod. H) Uropod.