Pseudobathytanais gibberosus, 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 : 16-20

Pseudobathytanais gibberosus n. sp. ( Figs. 8 & 9 )

Material examined: Holotype: Non­ovigerous female, body length 2.7 mm, Slope sta. 40 , 38º17,7’S. 149º11,3’E. Depth 400 m. Substrate sand, gravel, mud. 24/07­1986 . Paratypes: 2 non­ovigerous females. Same locality . All material collected by G.C.B. Poore & party on RV Franklin. Sampler: Epibenthic Sled Material held at NMV

Other material: 7 non­ovigerous females, 5 mancas. Same locality .

Diagnosis: First pleonite with prominent dorsal anteriorly directed process.

Description (adult female)

Body ( Figs. 8 A & 8 B): Sub­cylindrical, approximately 8 times longer than broad.

Cephalothorax ( Fig. 8 C): Rostrum prominent. Shorter than pereonites 1 and 2 together, 1.4 times longer width, antero­lateral corners acute.

Pereonites: Pereonite 1 wider than long, extending over cephalothorax at pereopod attachment. Pereonites 2­4 of increasing length; pereonites 4 and 5 longer than wide. Pereonite 6 subequal pereonite 2.

Pleon: Pleonite 1 with dorsal anteriorly directed process ( Fig. 5 D). Pleonites 2­5 length and width subequal, width approximately 4.0 length. Pleotelson longer than last pleonite.

Maxilliped endites.

Antennule ( Fig. 8 G): longer than cephalothorax. Article 1 shorter than rest of antennule, dorsal margin with 1 short simple seta, ventral margin with 1 simple and several sensory setae medially. Article 2 about 0.3 times length of article 1, distal margin with 1 long setulated and several sensory setae. Article 3 wide than long shorter than other articles, with 1 long setulated seta. Article 4 longer than article 2, distally with 1 aesthetascs, 1 simple short­ and 5 setulated setae twice as long as antennule.

Antenna ( Fig. 8 H): Shorter than cephalothorax. Article 1 smooth, wider than long. Article 2 longer than other articles, with 4 simple, 1 spiniform and 1 long setulated distal setae, dorsally with several spiny scales. Article 3 shorter than article 4, with 1 spiniform seta. Article 4 length subequal to article 5, with 1 long serrated distal seta on ventral margin and 4 short sensory distal setae. Article 5 marginally shorter than article 4, with 1 long setulated distal seta of more than twice the length of the antennae. Article 6 minute with 3 long setulated distal setae of more than twice the length of the antennae.

Mouthparts: Labrum not recovered. Left mandible ( Fig. 8 E) with strong molar process shorter than incisor, strongly defined lacina mobilis without denticulations, incisor tridentate. Maxillule ( Fig. 8 I) with 6 spiniform terminal setae and row of simple setae, palp shorter than endite. Maxilla ( Fig. 8 I) ovoid. Labium ( Fig. 8 F) with 2 thick setae on anterolateral corners and several spiny scales. Maxilliped ( Figs. 8 J & 8 K) endites with 2 short flat teeth; palp article 1, square, 1 seta on outer margin; article 2 ovoid, inner margin shorter than outer, 2 simple and 1 setulated setae on inner margin; article 3 with 4 setulated setae; article 4 inner margin with 4 setulated distal setae and several fine setules, outer margin with 1 setulated seta. Epignath smooth, as long as maxillule endite.

Cheliped ( Fig. 9 A ): Articulated to cephalothorax with triangular sclerite. Basis smooth, twice as long as wide. Merus ovoid, with 1 simple seta medially on ventral margin. Carpus oval, as long as basis, with 2 simple setae on ventral margin and 1 on dorsal margin. Propodus ( Fig. 2 K) with row of serrated setae flanking dactyl insertion. Fixed finger with strong spine, 1 simple seta on ventral margin, 3 on cutting edge. Dactylus narrow, with 2 spiniform setae on ventral margin.

Oostegites: no ovigerous specimens found.

Pereopod 1 ( Fig. 9 B ): Coxa but distinct. Basis width increases distally, smooth. Ischium width subequal length, with 1 simple seta on ventral margin, Merus width increases distally, with 1 simple distal seta on ventral margin. Carpus less than half as long as merus, with 3 simple distal setae. Propodus shorter than merus, tapering distally, with 4 simple distal setae and. Dactyl and terminal spine not fused, together as long as propodus.

Pereopod 2 ( Fig. 9 C ): Similar to pereopod 1 except: Basis shorter than on pereopod 1, with 1 dorsal seta. Ischium, with 2 ventral setae. Merus about 70 % shorter than on pereopod 1, with 2 simple ventral setae. Carpus with 1 spiniform distal seta. Propodus less elongated, with 3 simple distal setae.

Pereopod 3 ( Fig. 9 D ): Similar to pereopod 2 but: Ischium with 2 ventral­ and 1 dorsal setule. Merus smooth.

Pereopod 4 ( Fig. 9 E ): lateral coxa absent. Basis stout, as long as rest of pereopod, with 2 simple and 1 sensory ventral­ and 1 dorsal setae. Ischium smooth. Merus shorter than carpus with several denticulated scales. Carpus longer than ischium and merus together, with denticulate cuticular scales and 2 short stout denticulated distal setae. Propodus longer than dactylus, with 1 simple dorsal seta, 1 long distal­ and 2 ventral spiniform setae. Dactyl and terminal spine fused into a claw with denticles.

Pereopod 5 ( Fig. 9 F ): As pereopod 4, except: Basis stouter. Merus triangular, with 1 heavy denticulated spiniform seta and numerous spiny scales. Carpus with 3 heavy denticulated spiniform setae and spiny scale. Propodus without dorsal seta.

Pereopod 6 ( Fig. 9 G ): As pereopod 4 except: Basis longer and with only 1 dorsal seta. Merus with 1 spiniform seta and without denticulated scales. Carpus with 1 simple and 1 spiniform setae and spiny scale. Propodus with 2 spiniform ventral setae and 3 serrated distal setae.

Pleopods ( Fig. 9 H ): All 5 pairs similar. Protopod trapezoidal. Exopod armed with 18 plumose setae with gap between the most proximal and rest. Endopod with 13 plumose setae with gap between the 2 terminal ones and rest.

Uropods ( Fig. 9 I ): Protopod smooth, quadrate. Endopod with 1 article, width decreasing 0.3 midlength, with 1 simple and 2 sensory setae at midlength, 7 simple distal setae. Exopod with 1 article, 1 simple seta at midlength, 2 long simple distal setae.

Male: unknown.

Etymology: Named after the characteristic dorsal projection of pleonite 1. (Latin: Gibberosus = Hunchback).

Remarks: Pseudobathytanais gibberosus differs from the only other species in the genus, P. shtokmani Kudinova­Pasternak, 1990 , by the prominent dorsal projection on the first pleonite. Members of this genus can be distinguished from Bathytanais by the lack of a ventral process on antenna article 2.

Two of the 12 specimens of P. gibberosus examined during our study were parasitized with tantulocarids, a order of crustaceans presently known only from tanaidomorphan hosts. We observed only the expanded trunk­sac stages and these were attached to the pleotelson of the two infected specimens. This constitutes the first record for these parasites on a member of the family Paratanaididae and the first known occurrence for tantulocarids from the Indo­Pacific. Tantulocarids have been previously reported from the genera Typhlotanais and Leptognathia in the North Atlantic ( Boxhall et al. 1989).

The tubes of P. gibberosus are remarkably solid and are built from coarse gravel and sponge spicules.

Figures

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.

FIGURE 5. Bathytanais fragilis, holotype, female scale bar 2.5 mm. A) Dorsal view. B) Lateral view. C) Pleotelson. D) Cephalothorax.

FIGURE 8. Pseudobathytanais gibberosus, female. A + B holotype, C­ paratype. A) Dorsal view. B) Lateral view. C) Cephalothorax. D) Anterior directed spine on pleonite 1. E) Left mandible. F) Bucal cavity. G) Antennule. H) Antenna. I) Maxillule, maxilla and epignath. J) Maxilliped. K)

Figure 9. Pseudobathytanais gibberosus, female paratype. A) Cheliped. B) Pereopod 1. C) Pereopod 2. D) Pereopod 3. E) Pereopod 4. F) Pereopod 5. G) Pereopod 6. H) Pleopod. I) Uropod.