Eremisopus beei, Wilson & Keable, 2002

Wilson, George D. F. & Keable, Stephen J., 2002, New Genera of Phreatoicidea (Crustacea: Isopoda) from Western Australia, Records of the Australian Museum 54 (1), pp. 41-70: 44-52

publication ID 10.3853/j.0067-1975.54.2002.1359

persistent identifier

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scientific name

Eremisopus beei


Eremisopus beei   n.sp.

Figs. 1–7 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7

“New Genus 3”: Wilson & Johnson, 1999: 265, fig. 1.

“New Genus X3”: Wilson & Keable, 2001, table 1.

Type material. HOLOTYPE Ƌ, WAM C 25049 View Materials , bl 29.7 mm (formalin preserved), water temperature 24°C, depth 20 cm, slow flowing, 20 May 1997, C. Bee, D. Wilson & B. Hanson, 17 May, 1997   . PARATYPES: formalin fixed— AM P60527 View Materials , 6   ƋƋ (including 2 with exuvia, male “B” dissected to examine gut), 2 ♀♀ (including female “A” 22.6 mm, with exuvia, dissected for description), 2 mancas (offspring of female “A”)—all collected originally as for holotype then kept in aquaria for various lengths of time; AM P61456 View Materials   , Ƌ “D” bl 32.1 mm (dissected for description and illustration including; mouthparts, pereopods and pleopods), collection details as for AM P60527 View Materials ; AM P60528 View Materials , 47   ƋƋ, 2 ♀♀ (in amplexus with males), collection details as for holotype except— 14°10.55'S 126°41.39'E ( GPS), 26.0°C, pH 6.0, under rocks with gravel in flowing water, W. Ponder & G. Wilson, 18 June 1999, sample number WA576; AM P60529 View Materials GoogleMaps   , 37 ♀♀, 5 indeterminate specimens, collection details as for AM P60528 View Materials ; WAM C 25050 View Materials   , Ƌ bl 26.4 mm, 2 ♀♀ bl 17.3 mm, collection details as for AM P60528 View Materials ; AM P60530 View Materials   , female “D” bl 20.9 mm (dissected for pleopod description and illustrations), collection details as for AM P60528 View Materials ; AM P61453 View Materials   , Ƌ bl 29.2 mm (dissected for SEM of mandibles), collection details as for AM P60528 View Materials ; AM P61454 View Materials   , Ƌ bl 31.3 mm (dissected for SEM), collection details as for AM P60528 View Materials ; AM P61455 View Materials   , ♀ bl 18.6 mm (dissected for SEM) collection details as for AM P60528 View Materials   ; ethanol preserved— AM P60531 View Materials , 28   ƋƋ, 11 ♀♀, 3 indeterminate specimens, collection details as for AM P60528 View Materials   .

Type locality. “South Creek”, stream crossing road between Honeymoon Bay and PAGO Mission ruins, near Kalumburu Township , 15 km northeast of Honeymoon Beach , Western Australia, 14°10.529'S 126°41.408'E ( GPS), fine sand, under rocks GoogleMaps   .

Etymology. We are grateful to Mr Cameron Bee who brought this species to our attention, hence the species name

beei   in his honour.

Diagnosis. See generic diagnosis.

Description based on male. Colouration in 70% ethanol cream-yellow with dense covering of grey chromatophores, chromatophores less dense on pereopods and pleonites than on pereonites. Live colour similar, but whiter under dark chromatophores.

Head ( Figs. 1A,B View Figure 1 , 2A View Figure 2 ) length shorter than width in dorsal view; width 0.82 pereonite 1 width; lateral profile of dorsal surface smoothly curved; surface rough; setae absent. Eyes bulging dorsolaterally; maximum diameter 0.25–0.33 head depth; dorsal margin convex, ventral margin straight; orientation of longest axis between horizontal and vertical; ocelli distinguishable as individual units (etched on surface, pigment not clearly segmented), pigmentation dark. Cervical groove sigmoidal, extending nearly to dorsal margin of head. Mandibular groove smoothly indented. Mandibular notch present. Clypeal notch present. Antennal notch shallow, without posterior extension. Pereon ( Fig. 1A View Figure 1 ) broad, width exceeding head width (1.23 times); dorsal surface with transverse ridges, with scattered roughness, and smooth (roughness tending to be on posterior and lateral surfaces); setae on dorsal surface scattered, fine. Pereonites 2–7 in dorsal view wider than long. Coxal articulation of pereonites 2–4 fused (but with partial lateral suture more strongly developed in female than male), 5–7 free. Sternal processes absent. Typhlosole minimal, ventral invagination forming inverted U- shape in cross section (weak invagination); hindgut caecae absent. Pleonites ( Fig. 1A View Figure 1 ) in dorsal view 2–4 respective lengths more than half the length of pleonite 5, 1–4 relative lengths subequal, 1–4 width 0.87 composite length in dorsal view. Pleonite 5 with dorsal median ridge. Pleotelson ( Figs. 1A,C View Figure 1 , 2E–G View Figure 2 ) lateral length 0.15 body length, 0.73 depth; dorsal length 1.35 width; depth 1.3 pereonite 7 depth. Posterior margin entire, reflexed dorsally, without irregular denticulations; median lobe width 0.5 pleotelson width, produced, greatest length 0.35 pleotelson total length; lateral lobes narrower than median lobe, distinct from median lobe, not extending posteriorly to median lobe, medial length 0.35 pleotelson total length; median lobe with 4 robust sensillate setae (on margin, ventral postanal ridge with a row of 10); lateral lobes with 2 robust sensillate setae. Dorsal uropodal ridge without setae. Ventral margin anterior to uropods with robust setae, setae denticulate and smooth, 17 altogether (approximately), posterior seta larger than anterior adjacent setae. Antennula ( Fig. 2A,B View Figure 2 ) length 0.1 body length, with 15 articles. Tiny aesthetascs on article 7 to terminal article. Terminal article distally oblique, with 2 or more groups of aesthetascs. Penultimate article length approximately subequal to length of other articles. Distal articles oval. Antenna ( Figs. 1A View Figure 1 , 2C,D View Figure 2 ) length 0.42 body length. Flagellum length 0.62 total antenna length, with 27 articles. Propodal article 1 absent. Article 5 longer than article 4, article 6 shorter than articles 4 and 5 combined. Mouthfield clypeus consisting of broad asymmetrical bar, rounded at mandibular fossae and with concave lateral margins, width 0.43 head width. Labrum weakly angular ventrally, appearing shield shaped to semicircular in anterior view. Paragnaths ( Fig. 4A View Figure 4 ) with distolaterally rounded lobes, slightly produced distomedially, having medial and lateral setal rows and thickened medial base covered with dense long, fine setae. Mandible ( Fig. 3 View Figure 3 ) palp length 0.83 mandible length. Left spine row with 12 spines, 6 of which are bifurcate. Right spine row with 11 spines, 5 of which are bifurcate. Molar process length subequal to width; with 1 tooth, fine simple setae forming posterior row (implicit character state: dense along posterolateral margin). Maxillula ( Fig. 4B View Figure 4 ) medial lobe length 0.82 lateral lobe length; width 0.63 lateral lobe width; with 4 pappose setae; with 1 “accessory” seta, on distolateral margin, “accessory” setae simple; with 1 short weakly setulate seta on distal tip (weakly serrate). Lateral lobe distal margin with 8 denticulate robust setae, with 5 smooth robust setae; ventral face with 3 plumose setae (although only 1 of these appears to have setules on both margins). Maxilla ( Fig. 4C View Figure 4 ) medial lobe width 1.52 outer lateral lobe width; proximal portion smoothly continuous with distal portion; proximal and distal setal rows continuous. Outer lateral lobe longer than inner lateral lobe, width subequal to inner lateral lobe. Maxilliped ( Fig. 4D–F View Figure 4 ) epipod distal tip rounded. Endite medial margin with 3 coupling hooks on left side, 4 on right side; dorsal ridge with 24 large distally denticulate plumose setae (approximately, 8 are only distally denticulate, with one row of fine setules). Pereopod I ( Fig. 5A–D View Figure 5 ) dactylus ventrodistal margin smooth, with one distal accessory claw (heavy setae), distal accessory spines absent. Propodus dorsal margin proximal region protruding beyond distodorsal margin of carpus. Propodal palm convex to straight, spine-like projections absent; cuticular fringe weakly developed; stout denticulate setae absent; stout robust simple setae conical; elongate broad based setae absent. Merus dorsal margin projection shelf-like and U-shaped, with 1 or 2 robust simple setae. Basis ventrodistal margin elongate setae absent. Pereopods II–III ( Fig. 6A,B View Figure 6 ) dactylus without spines on ventral margin; with 1 distal accessory claw. Propodus articular plate present. Basis dorsal ridge in cross section angular and produced but not forming distinct plate. Pereopod IV ( Fig. View Figure 6

6C–E) subchelate with major hinges on dactylus-propodus. Dactylus length subequal to propodal palm (shorter in female). Propodus with 8–10 broad based setae on ventral margin, 2 distinctly larger than others; subequal in length to dactylar claw. Basis dorsal ridge in cross section angular and produced but not forming distinct plate. Pereopods V– VII ( Fig. 6F–J View Figure 6 ) dactylus with 1 distal accessory claw; spines

absent. Propodus articular plate on posterior side of limb present. Basis dorsal ridge distinctly separated from basis shaft, in cross section produced and forming distinct plate. Pereopod VII basis dorsal ridge distal margin rounded. Penes ( Fig. 6I View Figure 6 ) curved posteriorly; length 0.18 body width at pereonite 7, extending to midline; smooth, lacking setae, distally tubular; distal tip rounded. Pleopod ( Figs. 5H View Figure 5 , 7 View Figure 7 ) exopods lateral proximal lobes on II–V, medial proximal lobes on II–V. Endopods I–V with setae on margins (sparse, on lateral proximal margin only), setae simple on all (mixed with minutely serrate setae). Protopods II–V with medial epipods; protopod II lateral epipods lobe-like. Pleopod I exopod broadest proximally, distal margin rounded, lateral margin rounded, dorsal surface lacking setae. Pleopod II endopod appendix masculina shaft proximal half ventral shape in cross section concave, not forming tube; basal musculature not pronounced (present but comparatively weak); distal tip broadly rounded; with 99 setae on margin (approximately), occurring laterally and medially; length 0.32 pleopod length, distal tip extending near to distal margin of endopod. Uropod ( Figs. 1A View Figure 1 , 2E–G View Figure 2 ) total length 1.14 pleotelson length. Protopod length 0.42 uropod total length; dorsomedial ridge produced, plate-like, margin smooth, margin setae robust and simple; with 2 robust spinose setae on distoventral margin, without robust simple setae on distoventral margin. Rami cross-sectional shape flattened on dorsal surface only. Endopod longer than protopod, straight-curving dorsally; dorsal margin robust setae placed midlength, 3–6 robust setae (3 laterally, 6 medially). Exopod length 0.84 endopod length; with 4 robust setae.

Sexual dimorphism, differences of female from male. Antennula with 12 articles. Antenna flagellum length 0.68 total antenna length, with 26 articles; proximal articles lacking dense cuticular hairs. Pereopod I dactylus

ventrodistal margin with row of thin scale-like spines, along 0.56 total length; propodus dorsal margin proximal region not protruding beyond distodorsal margin of carpus. Pereopod IV propodus with 5 broad based setae on ventral margin. Uropod total length 0.96 pleotelson length; endopod with 2–7 robust setae (2 laterally, 7 medially); exopod length 0.86 endopod length, 3 robust setae.

Remarks. Some specimens of Eremisopus beei   n.gen., n.sp. were reddish, owing to red pigments (possibly iron oxides) from the substrate adhering to their cuticle. Mr Cameron Bee brought numerous specimens back from a May 1997 field trip to the Kimberley. He kept his specimens in an aquarium for over a year with various native fishes. We also kept several specimens in a small unheated tank in our laboratory from late May 1997 until January 1998. During this time, a brooding female released several young and moulted to a preparatory condition. Despite their limited distribution in the wild, these animals appear to tolerate a broad range of environmental conditions in the laboratory. In the aquaria, these animals were active and, when disturbed, swam using strong strokes of the pleopods and running motions of the anterior pereopods.

General distribution and habitat. “South Creek”, near Kalumburu, Western Australia; fine sand and gravel, under rocks.


Western Australian Museum


Australian Museum