Limnadopsis multilineata, Timms, 2009

Timms, Brian V., 2009, A Revision of the Australian Endemic Clam Shrimp Genus Limnadopsis Spencer & Hall (Crustacea: Branchiopoda: Spinicaudata: Limnadiidae), Records of the Australian Museum 61 (1), pp. 49-72 : 62-63

Limnadopsis multilineata n.sp.

Figs. 2E , 5C , 11

Types. Holotype 3 WAM C39334; allotype ♀ WAM C39335, paratypes WAM C38102. Type locality: Western Australia, Kimberley, Mitchell Falls , rock pools at the top. 14°49'S 125°42'E, 14.i.1973, Smith-Johnstone.

Other material. Western Australia: via Broome, Lake Campion , 17°50'S 122°45'E, 28.iii.1996, C. Brockway, WAM C38103 .

Distribution. Kimberley and adjacent area of northwestern Western Australia.

Etymology. The specific name refers to the large number of growth lines in this species.

Male. Carapace of mature individuals ( Fig. 11A ) about 10–12 mm long and 6–8 mm high, L:D ratio c. 1.5–1.6. Dorsal margin almost smooth and nearly straight, anterior angle distinct, about 100°, and dorsoposterior margin slightly depressed and ending in rounded protrusion. Umbo distinct, triangular in shape, but not protruding above the dorsal margin. Anterior edge of carapace evenly curved, ventral edge almost straight, and posterior edge protruding and rounded so that it is convex posteroventrally and concave dorsoposteriorly. About 20 distinct growth lines with a further 10–12 closely spaced lines on outer 10–15% of carapace. Carapace brown and surface apparently granular, but “grains” actually comprising numerous dendritic pigment cells.

Head ( Fig. 11B ) with pyriform frontal organ placed posteriorly and protruding a little farther than eye mound. Anteriorside of eye mound and rostrum meeting at about 120°, junction angular. Rostrum protruding with almost parallel dorsal and ventral edges and downward curving apex. Naupliar eye triangular with largest surface ventral. First antenna subequal in length to peduncle of second antenna and having about six lobules. Second antenna with peduncle of 12 apparent segments and two flagella of about 20 flagellomeres each. Most second antennal segments, particularly in the region of each flagellum, bearing 3–5 spines anteriorly ( Fig. 11D ).

Trunk segments usually 26, each bearing pair of thoracopods, these decreasing in size posteriorly and with anterior two pairs modified as claspers. Posterodorsally each segment with large, rounded protuberance, this bearing 5–7 large spines on last five segments, many setae on next 5 segments anterior to these, and 1–3 setae on most other segments. Claspers of normal structure for Limnadopsis , with single spine apically on movable finger.

Telson ( Fig. 11C ) with about 15 spines in each dorsal row, largely saw-tooth in appearance, i.e. shaped like isosceles triangles, but first two narrower, first a little longer than second. Two telsonic setae inserted on protuberance situated about one fifth of way along dorsal side of telson. Caudal claws about 9–10 times longer than wide, fairly evenly curved ventrally and bearing about 14–18 setae mediodorsally, followed by about 6 short spines dorsally and numerous denticles on the markedly curved apical quarter of claw. First one or two spines sometimes arising between last few setae.

Female. Largely similar to male, except in carapace shape ( Fig. 11E ), rostrum shape ( Fig. 11F ), and lack of claspers. Dorsal margin of carapace evenly arched, almost smooth. Dorsoanterior angle distinct, about 110°, dorsoposterior angle as in male, but not so marked. Umbo as in male. Anteroventral area of carapace more convex than in male, while posteroventral area also expanded as in male but more posteriorly than ventrally, thus giving an appearance of greater posterior expansion than in male. Growth lines as in male.

Head ( Fig. 11F ) with proportionally smaller eye than in male, and thus with pyriform frontal organ protruding more dorsally than in male. Rostrum short, almost in form of isosceles triangle, with rounded apex. Naupliar eye triangular and occupying about half of rostrum.

Eggs ( Fig. 5C ) most unusually shaped and structured; somewhat bell-shaped, about 240 µm high and about 220 µm in diameter (range 236–242 µm high, 218–223 in diameter, n = 5), with about 7 (6 around the circumference and one ventrally) large grooves separated by unevenly developed sharp ridges, some of latter meeting at top in distinct point. Each groove containing smooth, weakly developed subsidiary ridge.

Variability. Specimens from Broome are a little different from the type lot. The carapace tends to be slightly larger at 11–12 mm by 7–8 mm, but the unusual shape is the same as in males and females from Kimberley. The dorsal margin is more irregular than in the Kimberley specimens, but still basically smooth. There are only 25 growth lines, with nearly 20 of these distinct and well spaced and 4–6 situated marginally and closely spaced; therefore they do at least feature the same unusual arrangement of many well-spaced lines and a few tightly-spaced lines. The first antennae have 7 lobules and the second antenna 18 flagellomeres, both figures being slightly different from the type lot. The telson also armed differently: 16–18 dorsal spines with the first one 1.5 times larger than the rest, and caudal claw with about 15 long setae and 4–5 spines two-thirds of the way along its length.

Comments. This species is distinctive by reason of its carapace shape and its possession of numerous growth lines arranged in two groups about 20 normally spaced lines and 4–10 marginal lines spaced very closely together. It has many (ca 5–6) spines midlength on the cercopods, as do L. parvispinus , L. occidentalis and L. minuta , but is easily distinguished from these species by its unique carapace as mentioned above, and in contrast to L. parvispinus and L. occidentalis , by the well expressed growth lines (as opposed to faint lines), and 1–2 fewer spines on the middle flagellomeres. Features distinguishing it from L. minuta are noted above.

Figures

Fig. 2. Photographs of whole specimens of species of Limnadopsis. (A) L. birchii; (B) L. tatei; (C) L. parvispinus; (D) L. minuta; (E) L. multilineata; (F) L. occidentalis; (G) L. paradoxa; (H) L. pilbarensis. Scale bars 5 mm.

Fig. 5. SEMs of eggs. (A) Limnadopsis birchii, Twin Pans, Currawinya National Park, Qld; (B) L. birchii, Bluebush Bore Swamp, via Carnarvon, WA; (C) L. multilineata, Mitchell River Falls, Kimberley, WA; (D) L. tatei, Bloodwood Station, Paroo; (E) L. tatei, near Laverton, WA; (F) L. pilbarensis, Chichester Range, WA; (G) L. parvispinus, Bloodwood Station, via Bourke, NSW; (H) L. parvispinus, Coolringdon Station, via Cooma, NSW; (J) L. occidentalis, Boolathana Station, via Carnarvon, WA; (K) L. paradoxa, Sieda Farm, Grass Patch, WA; (L) L. paradoxa, East Lake Bryde, via Newdegate, WA; (M) L. minuta, Keep River National Park, NT. Scale bars 50 µm.

Fig. 11. Limnadopsis multilineata n.sp., Mitchell Falls, Kimberley, WA. Male: (A) carapace; (B) head; (C) telson; (D) a middle flagellomere of second antenna. Female: (E) carapace; (F) head. For clarity, some growth lines are incompletely shown anterior to umbo and marginally. Scale bars 1 mm.