Aatolana springthorpei, Keable, 1998

Keable, Stephen J., 1998, A third species of Aatolana Bruce, 1993 (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 50 (1), pp. 19-26 : 22-26

Aatolana springthorpei n.sp.

Figs 1 -2

Type material: HOLOTYPE: 0, 48 mm, AM P47650 . PARATYPES: 0, AM P47651; 0, ZMUC CRU2395 ; 0, USNM 282732; 0, BMNH 1997.1752.

Type locality: offEast Fitzroy Reef , Queensland, Australia, 23°32.16'S 152°17.98'E, baited trap, 17.8°C, 203 m, J.K. Lowry, P. Freewater & R. T . Springthorpe on MV Reefknot, 16-17 June 1993, SEAS QLD-958 .

Additionalmaterial examined: 2 00, 2 C(C((1 damaged), AM P47652, east of Coffs Harbour, New South Wales, Australia, 30014.63'S 153°27.68'E, baited trap, 199 m, P.B. Berents, R. T. Springthorpe & W. Vader 12-l 3 Aug. 1993, SEAS NSW-883 .

Diagnosis: Frontal lamina: with a rounded posteroventral projection. Antenna: 0.4 x as long as body; when extended against the body reaching to posterior of pereonite 4. Pereopod 7: basis anterior margin with long slender setae present along entire length. Uropods: endopod lateral margin slightly convex; exopod lateral margin convex.

Material described: Holotype.

Description: Male. Overall bodyform: large; 48 mm long; narrow, length approximately 3.3 x width. Colour cream in alcohol. Chromatophores absent.

Cephalon: anterior margin recessed with a small ventrally directed rostrum below margin; submarginal cephalic furrow well developed, runs entire length of anterior margin. Eyes: with 20 ommatidia in horizontal diameter; with 9 ommatidia in vertical diameter; rectangular (bisected by anterior margin); black-redlbrown in alcohol. Interocularfurrow: moderately developed, distinct but not extending across the cephalon. Frontal lamina: length approximately 1.3 x basal width; pentagonal in ventral view, with a rounded posteroventral projection. Clypeus: triangular; not sculpted. Labrum: flat; narrower than clypeus. Antennule: peduncular article 1 longer than article 2; article 2 with 1 slender seta on posterior margin, 2 penicillate setae at posterodistal angle and 2 penicillate setae on anterior margin; article 3 long, larger than article 1 or 2 but shorter than their combined lengths. Flagellum 32-articulate; aesthetascs present. Antenna: of medium length, 0.4 x as long as body; when extended against the body reaching to posterior of pereonite 4. Peduncular article 4 with several slender setae on distal margin; article 5 with several slender and penicillate setae along distal margin. Flagellum 49-articulate.

Mandible: molar medial surface smooth, short fine slender setae restricted to posterior margin, long slender setae along anterior margin; incisor tridentate, with strongly developed posterior tooth; palp article 2 approximately 2 x the length of article 3, provided with numerous slender setae distally and minutely biserrate slender setae proximally; lacinia mobilis-like structure present on left mandible only, forming a dark brown highly sclerotized triangular structure, embedded in the body of the mandible separate to the raised setal row; setal row with 19 robust setae. Maxillule: medial lobe with 3 large and 1 smaller robust pappose setae, lateral margin with protuberance well developed; lateral lobe with 13 robust setae on distal surface (2 of which are slender). Maxilla: lateral lobe slender, with 10 slender setae; medial lobe with 22 slender and 11 plumose setae; middle lobe with 18 slender setae. Maxilliped: palp moderately setose; articles

not fused; article 3 length subequal to breadth; article 4 length less than breadth; article 5 length greater than breadth, with serrate setae present; lateral margin with slender setae along most of the length of articles 2-5, plumose setae absent. Endite with 2 coupling hooks, and 8 plumose setae.

Pereon: ornamentation consists of 1 strongly developed furrow on lateral margin of pereonite 1 and 1 short, medial furrow on lateral margins of pleonites 4-7; pereonite 1 longest, 4-6 subequal and longer than 2-3 and 7 which are subequal. Coxae: furrows strongly developed, on all coxae, anteroventral corners of coxae 4-7 sloping

ventromedially. Coxal points variously developed, pereonite 1 and coxae 2-3 with rounded posteroventral corners, coxae 4-7 with increasingly produced, broad, acute posteroventral corners.

Pleonites: 5 present, all equally visible along dorsal margin; ornamentation consists of 2 strongly developed furrows on lateralmargin of pleonite 2 and 3 on lateralmargin of pleonite 3. Pleonite 1: posterolateral margins produced, dorsal margin much more produced than ventral margin. Pleonite 2: dorsal posterolateral margin clearly projecting posterior to ventral posterolateral margin. Pleonite 4: posterolateral margins extending subequal to pleonite 3; posterodorsalmargin strongly concave proximal to meeting posteroventral margin at apex; apex slightly rounded.

Pleotelson: narrow, length 1.1 x basal width; dorsal surface smooth, setae, ornamentation and sculpting absent; anterolateral margins convex; posterolateral margins convex, meeting smoothly to a point; robust setae present, 12 altogether, 6 on each posterolateral margin; marginal plumose setae present, restricted to posterolateral margins, abundant.

Pereopods 1-7: dactylus with a distinct secondary unguis. Pereopod 1: basis with slender setae on anterior margin; posterodistal angle with a group of slender setae. Ischium anterodistal angle without robust setae, 1 row of slender setae along margin; posteriormargin without robust setae, slender setae present, sparse. Merus anterodistal angle without robust setae, but with approximately 4 slender setae; anterior margin without robust setae; posterior margin bisinuate, with 7 robust setae and approximately 3 slender setae. Carpus without robust setae, slender setae present. Propodus with 3 robust setae on palm, with 1 robust seta opposing dactylus; marginal slender setae present; anterodistal angle with sparse slender setae. Dactylus long, subequal in length to propodus. Pereopod 2: ischium anterodistal angle with 1 robust seta; posterior margin with 2 robust setae. Merus anterodistal angle with 5 robust setae; posterior margin with 10 robust setae. Carpus with 2 robust setae. Propodus with 2 robust setae on palm; 1 robust seta opposing dactylus. Pereopod 3: ischium posterior margin with 2 robust setae. Merus anterodistal angle with 8 robust setae; posterior margin with 11 robust setae. Carpus with 2 robust setae. Propodus with 2 robust setae on palm; 1 robust seta opposing dactylus. Pereopods 4-6: becoming progressively longer. Pereopod 4: similar to pereopods 5-7. Pereopods 5-7: relative morphology similar, width and setation of articles not varying markedly. Pereopod 6: basis broader than that of pereopod 7; propodus shorter than that of pereopod 7. Pereopod 7: basis narrow, width 0.4 x length; anterior margin straight, long slender setae present along entire length; medial carina with slender setae present; posterior margin convex, with slender setae present on proximal quarter; posterodistal angle with slender setae present. Ischium length greater than width; anterior margin without setae; anterodistal angle with 7 robust setae, non-robust setae absent; posterior margin with 8 robust setae, nonrobust setae absent; posterodistal angle with 5 robust setae, slender setae present. Merus length greater than width; anterior margin without setae; anterodistal angle with 16 robust setae, 1 slender seta present; posterior margin with 6 robust setae; posterodistal angle with 7 robust setae, nonrobust setae absent. Carpus anterior margin without setae; anterodistal angle with 9 robust setae, slender setae present; posterior margin with 6 robust setae, 1 slender seta present; posterodistal angle with 7 robust setae, non-robust setae absent. Propodus subequal to carpus; anterior margin without setae; anterodistal angle with 1 robust seta, slender setae present; posterior margin with 8 robust setae, nonrobust setae absent; posterodistal angle with 2 robust setae, non-robust setae absent.

Pleopod 2 appendix masculina: 1.3 x length of endopod; margins bent slightly medially, somewhat broader proximally but otherwise approximately parallel along entire length; slender; apex not at angle to margins, bluntly rounded. Pleopods 1-5: exopod suture strongly developed on pleopods 3-5 only.

Uropods: peduncle ventrolateral angle with 2 robust setae, and 10 plumose setae. Endopod lanceolate; medial margin convex, with 6 robust setae, plumose setae present, along entire length; lateral margin slightly convex, with 6 robust setae, plumose setae present, on distal two-thirds. Exopod slightly shorter than endopod, 0.88 x the length of the endopod; lanceolate; medial margin convex, with 4 robust setae, plumose setae present, on distal threequarters; lateral margin convex, with 6 robust setae, plumose setae present, along entire length.

Sexual dimorphism: Female similar to male.

Variation: Pleotelson and uropod robust setal counts from margins (n = 4 but damaged specimens omitted; paratypes): Pleotelson: 7:6 100% (3 specimens damaged); endopod (medial): 7-50%, 6-25%; (lateral): 6-25%, 5- 50%; exopod (medial): 4-50%, 3-25%; (lateral): 9-25%, 8-25%,6-25%, 5-25%. AM P47652 (n = 4-but damaged specimens omitted): Pleotelson: 7:8-25%, 7:7-25%, 6:6- 25%; endopod (medial): 10-25%, 7-50%, 6-25%; (lateral): 6-25%, 5-50%; exopod (medial): 5-25%, 4-75%; (lateral): 9-50%, 8-50%.

Size range: Adults to approximately 50 mm.

Etymology: This species is named after Mr R. Springthorpe who assisted in collecting the type specimens, in recognition of the help he has given me with this and other projects.

Remarks. Aatolana springthorpei is most similar to A. rapax but can be distinguished by the posteroventrally projecting frontal lamina and shorter antennae (extending to the posterior of pereonite 5 in A. rapax ). Aatolana schioedtei is also similar. However, in A. schioedtei the structure of the frontal lamina differs, the posterior margin of coxa 7 is distinctly concave, the lateral margins of the uropod rami are strongly sinuate (especially the exopod), pereopod 7 has a greater number of distinctly plumose setae on the margins of the basis, ischium and merus, and the pleotelson of adults has fine setae covering much of the dorsal surface.

Parker (1995) reported that iridescence may be displayed by light reflected from diffraction gratings occurring on the aesthetascs of the antennule of Aatolana rapax . This was based on observations of the material examined by Keable (1997). Similar iridescence is also encountered in a variety of other cirolanid isopods, such as A. springthorpei , A. schioedtei , Bathynomus spp., Booralana spp., Cirolana spp., Plakolana spp. and an undescribed taxon similar to Dolicholana elongata , but has not been found in any species of Natatolana (personal observation).

Distribution: east coast of Australia-off northern Queensland and New South Wales. In depths of approximately 200 m.

Ecology: Aatolana springthorpei is a scavenger as are other members of the genus ( Bruce, 1993b; Keable, 1997).

ACKNOWLEDGMENTS. I would like to thank Dr J.K. Lowry for making the material described here available for me to study. I am also grateful to Dr G.D.F. Wilson for comments on an initial draft of the manuscript, and to Mr R.T. Springthorpe who composed and inked the plates of my illustrations. This study was undertaken in partial fulfilment of a PhD degree, Macquarie University, while in receipt of a Macquarie University Postgraduate Scholarship. I would particularly like to thank my supervisor Dr J. Lowry and also Dr D. Griffin (Director) of the Australian Museum for providing facilities to carry out the study.

Figures

Fig. 1. Aatolana springthorpei, holotype. CE a, band c are dorsal, anterior and lateral views of cephalon, respectively. Scales = 0.5 mm.