Comprehensive Description

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Description

Cirolana australis sp. nov.

 

 

Cirolana new species.—Koslow and Gowlett-

 

Holmes, 1998: 41.

 

Cirolana n.sp. 4.—Lowry, 1998: 63, 64.

 

Material examined. Holotype. Main Pedra Seamount, off southern Tasmania (44°15.6´S 147°7.8´E), baited trap, 1,312 m, 21–24 Jan 1997 (CSIRO Cruise SSO1/97, stn 8), AM P59351 (male, 23 mm).

 

Paratypes. All same data as holotype. AM P59352 (977 specimens); BMNH 2000.2408–2409 (male, female); NMV J47153 (male, female); TM G3588 (2 females); USNM 296460 (male, female).

 

Additional material. E of Fortescue Bay, Tasmania (43°08.96´S 145°15.36´E), baited trap, 5.1°C, 1000 m, J. Lowry and P. Freewater, 16–17 Apr 1993 (stn SEAS TAS-365), AM P59353 (2 females, 1 male, 6 mancas); stn SEAS TAS-367, AM P59354 (7 females, 1 male, 5 mancas).

 

 

Diagnosis. Cephalon: rostrum not extending to frontal lamina, not dividing antennules; anterior

 

margin not overriding antennules. Eyes: well developed, round. Frontal lamina: anterior margin

 

angled. Pereonites: 1–7 with 2 transverse carinae; 4–7 with tubercles. Pleonites: 3–5 with tubercles. Pleonite 4: ventral margin free of pleonite 3; posterodorsal margin apex broadly rounded dorsally but meeting convex ventral margin at a point. Pleotelson: dorsal surface with paired tubercles in rows, (3 in each row, forming an indistinct ridge parallel to each lateral margin), conspicuous fine setae absent; anterolateral margins convex; posterolateral margins concave; apex truncate; 2–6 (usually 2 or 4) robust setae across apex. Penes: present. Pereopod 1: propodus without plumose setae. Pereopods 4–6: basis posterodistal angle robust setae absent. Pleopod 2 appendix masculina: arising subbasally; extending beyond tip of endopod, 1.46 length of endopod from insertion point; margins sinuate, tapering along entire length; slender; apex not at angle to margins, bluntly rounded. Uropods: endopod not dimorphic; lateral margin straight for proximal twothirds, convex at distal third; exopod not dimorphic; lateral margin straight, robust and plumose setae continuous along margin.

 

 

Additional descriptive characters based on holotype.

 

Body: length approximately 2.6 greatest width; white in alcohol; chromatophores absent; cuticular surfaces scale-like.

 

Cephalon: tubercles absent. Eyes: visible in ventral view; black in alcohol; partially overlapped by pereonite 1; ommatidia in rows, 7 ommatidia in horizontal diameter, 7 ommatidia in vertical diameter. Interocular furrow: distinct, not extending across cephalon. Frontal lamina: length approximately 1.9 basal width; pentagonal; lateral margins divergent; apex not projecting, not visible in dorsal view, not expanded, in 1 plane (not stepped). Clypeus: triangular, not produced.

 

Pereonites: 4–7 length subequal and longest, 1–3 subequal; tubercles small, fine, subequal, continuous across entire posterior margin.

 

Pleonites: 1–5 equally visible along dorsal margin; tubercles small, subequal, continuous across entire posterior margin.

 

Pleotelson: length 0.85 basal width; anterodorsal uropodal sutures present; 4 robust setae across apex; plumose setae restricted to posterolateral margins, numerous proximal to robust setae.

 

Antennule: just reaching pereonite 1. Peduncular bases touching; articles 1–2 free; article 1 length less than width, subequal to article 2; article 2 longer than wide, with a few scattered slender and penicillate setae; article 3 longer than combined lengths of articles 1–2, length greater than width. Flagellum shorter than peduncle; articles not compressed (lengths of most greater than half width); 8-articulate; aesthetascs not iridescent. Antenna: 0.3 length of body, when extended against body reaching to posterior of pereonite 3. Peduncular article 2 shorter than article 3; article 4 much longer than article 3, posterodistal angle with 4 slender setae, anterodistal angle with 5 slender setae; article 5 subequal in length to article 4, posterodistal angle with 2 penicillate and 2 slender setae, anterodistal angle with 1 penicillate and 7 slender setae. Flagellum 19-articulate; setal brush absent.

 

Mandible: molar medial surface covered with short fine slender setae, cluster of long slender setae proximally present, long slender setae in submarginal row across 0.75 length of anterior margin; marginal robust setae close set. Setal row with 15 robust setae; medial surface covered in fine setae. Maxillule: medial lobe lateral margin protuberance absent; lateral lobe with 10 robust setae on distal surface and 2 slender setae. Maxilla: lateral lobe with 4 plumose and 1 slender setae; medial lobe with 14 plumose setae, medial plumose setae subequal to proximal setae; middle lobe with 4 plumose and 8 slender setae. Maxilliped: right endite with 1 coupling hook, left endite with 2 coupling hooks.

 

Pereopods: 1–3 merus posterior margin robust setae strongly molariform on 1 only; 2–7 coxal furrows complete. Pereopod 1: posterior margin setose fringe absent; propodus robust; dactylus shorter than 0.5 propodus length.

 

Penes: separated by more than width of both penes; forming flattened lobes; length approximately 1.5 basal width.

 

Pleopods: exopod suture complete on 3–5. Pleopod 1: exopod medial margin tapering evenly, proximolateral robust seta present; endopod shorter than exopod, lateral margin slightly concave.

 

Uropods: extending beyond pleotelson. Peduncle ventrolateral angle without robust setae, with 13 plumose setae; lateral margin robust seta absent; distolateral angle rounded. Endopod medial margin convex, with 5 robust setae, plumose setae along entire length; apex subbifid with lateral spine largest, with 1 minute medial robust seta, setal cluster formed by plumose and slender setae; lateral margin with 4 robust setae, plumose setae along entire length. Exopod 0.94 length of endopod; medial margin convex, with 4 robust setae, plumose setae along entire length; apex subequally bifid, without robust setae, setal cluster formed by slender setae; lateral margin with 7 large robust setae, plumose setae along entire length.

 

 

Sexual dimorphism. Females differ from males

 

only in the primary sexual characters.

 

 

Variation. Pleotelson and uropod robust setal counts from margins (N = 20, subsample of 10 males and 10 females from AM P59352): Pleotelson: 1:1 (30%), 2:1 (40%), 2:2 (25%), 3:3 (5%).

 

Endopod: (medial) 5 (10%), 6 (70%), 7 (20%); (lateral) 3 (65%), 4 (35%). Exopod: (medial) 4 (75%), 5 (25%); (lateral) 5 (10%), 6 (40%), 7 (45%), 8 (5%). Subadult males (19 mm, AM P59352) have the vas deferens opening almost flush to the surface of the sternite and the appendix masculina inserted submedially.

 

 

Size range. Mancas approximately 7 mm, adults to approximately 25 mm.

 

 

Etymology. Australis, Latin, southern, referring to the position of the type locality.

 

 

Distribution. Eastern and southern Tasmania; 1000–1312 metres.

 

 

Remarks. Cirolana australis is most readily differentiated by the ornamentation of the somites, coupled with the sinuate lateral margins and truncate apex of the pleotelson, low number of robust setae on the pleotelson apex, straight lateral margins of the uropod rami, and continuous distribution of the robust and plumose setae along the uropod exopod lateral margin. Other species of Cirolana in which robust setae occur on the margins of the pleotelson usually have six or more, but four have also been recorded in C. rugicauda Heller, 1861. Cirolana rugicauda is distinguished from C. australis by (in C. rugicauda): the rounded apex of the frontal lamina; the projecting clypeus (a character which has been used to diagnose genera and groups of genera excluding Cirolana, e.g. Bruce (1986)); and pleonite 3 enclosing pleonite 4 (Vanhöffen, 1914; Barnard, 1940; Kensley, 1978). Cirolana sulcata Hansen, 1890 and Cirolana transcostata Barnard, 1959 may be difficult to distinguish from C. australis but have a frontal lamina with a rounded apex, and uropods with lateral margins that are more convex. Cirolana tuberculata (Richardson, 1910) is also similar but has more prominent tubercles on the pleotelson and uropods with convex lateral margins (Delaney, 1986).”

 

 

(Keable, 2001: 348-352)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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