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

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Pseudobathytanais gibberosus

n. sp.

Pseudobathytanais gibberosus n. sp. ( Figs. 8 View FIGURE 8 & 9 View Figure 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 GoogleMaps . Paratypes: 2 non­ovigerous females. Same locality GoogleMaps . 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 View FIGURE 8 A & 8 B): Sub­cylindrical, approximately 8 times longer than broad.

Cephalothorax ( Fig. 8 View FIGURE 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 View FIGURE 5 D). Pleonites 2­5 length and width subequal, width approximately 4.0 length. Pleotelson longer than last pleonite.

Maxilliped endites.

Antennule ( Fig. 8 View FIGURE 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 View FIGURE 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 View FIGURE 8 E) with strong molar process shorter than incisor, strongly defined lacina mobilis without denticulations, incisor tridentate. Maxillule ( Fig. 8 View FIGURE 8 I) with 6 spiniform terminal setae and row of simple setae, palp shorter than endite. Maxilla ( Fig. 8 View FIGURE 8 I) ovoid. Labium ( Fig. 8 View FIGURE 8 F) with 2 thick setae on anterolateral corners and several spiny scales. Maxilliped ( Figs. 8 View FIGURE 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 View Figure 9 ): 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 View FIGURE 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 View Figure 9 ): 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 View Figure 9 ): 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 View Figure 9 ): Similar to pereopod 2 but: Ischium with 2 ventral­ and 1 dorsal setule. Merus smooth.

Pereopod 4 ( Fig. 9 E View Figure 9 ): 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 View Figure 9 ): 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 View Figure 9 ): 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 View Figure 9 ): 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 View Figure 9 ): 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.