Caridina riverstoni, Richard, Jasmine & Clark, Paul F., 2014

Richard, Jasmine & Clark, Paul F., 2014, Caridina simoni Bouvier, 1904 (Crustacea: Decapoda: Caridea: Atyoidea: Atyidae) and the synonymy by Johnson, 1963, Zootaxa 3841 (3), pp. 301-338 : 333-336

Caridina riverstoni sp. nov.

( Figs. 17 , 18 )

Caridina mccullochi J. Roux 1926b: 249 (partim).

Material examined. Types: Australia. Holotype. Freshwater stream at Port Macquarie , New South Wales, coll. & pres. A.R. McCulloch, 1913, det. J. Roux, 1♂, AM reg. P.3935; Paratypes. 1♀, AM reg. P.92469; freshwater stream at Port Macquarie , New South Wales, exch., 1♀, NMB reg. 737b.

Description. From the Holotype and the Paratypes. Adult size 16–23 mm. Carapace length 3.3–3.8 mm.

Rostrum ( Fig. 17 a, b): Slightly longer than the antennular peduncle or shorter, 2.5–3.45 mm long. 0.75–0.9×long as carapace. Tip pointed, 13–17 teeth on the dorsal margin up to the tip (not compact initially and more spaced distally), 2–3 post orbital teeth present. 2–4 teeth on the ventral margin not compactly with a distal unarmed margin. Tip pointed. Formula (2–3) 13–17/2–4.

Antennular peduncle ( Fig. 17 a, b): 0.7–0.8×carapace. Stylocerite 0.5–0.7×length of basal segment. Anterolateral teeth of basal segment 0.15–0.20×second segment. 10–15 segments bearing aesthetascs.

First pereiopod ( Fig. 18 a): Dactylus 1.25–1.3×palm of propodus. Chela 2.1–2.15×long as broad. Carpus 2.5–2.6×long as broad with anterior excavation.

Second pereiopod ( Fig. 18 b): Dactylus 1.4–1.5×long as palm of propodus. Chela 2.2–2.3×long as broad. Carpus 5.35–5.4×long as broad.

Third pereiopod ( Fig. 18 c, d): Dactylus 3.35–4.00×long as broad. 8–10 spines on dactylus including terminal spine. Propodus 4.1–4.5×long as dactylus and 11–12×long as broad with 10–12 spines arranged along inner margin. Carpus 0.55–0.6×long as propodus with 1 large spine and 2–3 minute spines on inner margin. Merus 1.6–1.7×carpus length. Merus with 3 large spines on posterior margin.

Fifth pereiopod ( Fig. 18 e, f): Dactylus 3.75–3.8×long as broad with 27–35 spines in comb-like fashion on inner margin. Propodus 11–12×long as broad and 3.4–3.5×long as dactylus and with 10–14 spines along posterior margin. Carpus 0.45–0.5×propodus length and with 1 large spine and 2 minute spines along inner margin. Merus 1.5–1.6×carpus length, with 2 large spines at posterior margin.

Setobranchs: 2 setae on all pereiopods.

First male pleopod ( Fig. 18 g, h): Endopod 0.3×exopod length. Appendix interna absent. Several long setae present along the entire margin

First female pleopod ( Fig. 18 i): Endopod 0.65×exopod length.

Second male pleopod ( Fig. 18 j, k): Appendix masculine 1.6×appendix interna and 0.35×endopod.

6th abdominal somite: 0.5–0.6×long as carapace.

Telson ( Fig. 18 l, m): Broad, 1–1.1×long as 6th abdominal somite. Dorsal spines 5–7 pairs (including subterminal spine). In one male and one female the posterior margin rounded with 1 pair of laterals and 2 pairs of intermediate spines of which the inner pair shortest. In another female 1 pair of lateral spines 3 intermediate spines present. The median spines are shorter than the rest.

Uropod ( Fig. 18 n): 8–11 diaeresis spinules.

Preanal carina ( Fig. 18 o): Unarmed.

Etymology. riverstonei: named in honour of Allan Riverstone McCulloch, born on 20th June 1885 at Concord, Sydney, New South Wales, Australia and tragically died at the age of forty in his room at the Colonial Hotel, Honolulu, on 1st September 1925. Allan was an ardent field naturalist and carried out work along the whole east coast of Australia which included collecting the material named for him here. The authors of the present study regret having to synonymise Caridina mccullochi named for Allan by Jean Roux.

Distribution. Known only from the type locality.

Type locality. Port Macquarie, New South Wales, Australia.

Remarks. Roux (1926b) described C. mccullochi from three localities in New South Wales, Australia namely Pallal, Horton River, near Bingara, North Yanco, Narrandera and a freshwater stream at Port Macquarie, and was aware of the morphological variation between the samples. The specimens described from Pallal, Horton River, near Bingara are labelled as the types of C. mccullochi and this material in now considered to be a junior synonym of C. peninsularis .

Jean Roux (1926b) states “I include in this species ( C. mccullochi ) three young specimens from Port Macquarie, which are badly preserved. The rostral formula is nearly the same as in the preceding specimens whilst the number of teeth is smaller. There are 12–15 teeth on the upper border of the rostrum, the two proximal of which are situated on the cephalothorax; the intervals between 2 or 3 proximal ones are a little greater than the others. The rostrum reaches in front the ⅓ or the ½ of the last segment of the antennular peduncle.”

The present study examined the male and 2 female specimens (16–23 mm in size) from Port Macquarie. They exhibit the following characters; the endopod of the first pleopod of female is 0.6 long as the exopod, and that of male with a well developed appendix masculina on the second pleopod. These charcaters suggest that the Port Macquarie specimens are mature and not, as considered by J. Roux (1926b) to be ‘young’. They are here regarded as an undescribed species.

Caridina riverstoni sp. nov. has a shorter rostrum that reaches the end of the antennular peduncle or shorter, equal to the second segment of the antennular peduncle, have lesser number of teeth 13–17 (not 12–15 as indicated by J. Roux) on dorsal margin that are not compact proximally and the distal teeth more spaced. 2–4 teeth of the ventral margin leaving the distal ventral margin unarmed. The unique morphology of the rostrum differentiates the specimens of Port Macquarie. Also, as rightly pointed out by J. Roux (1926b), the spines on the dactylus of the fifth pereiopod are fewer in the specimens from Port Macquarie being 30–35. In two specimens, a male and female from Port Macquarie, the posterior margin of the telson is rounded with the median pair of intermediate spines being shortest. However, the other female specimen has three intermediate spines of which the median one is slightly shorter. Examining more specimens might confirm this difference. The spaced placement of teeth initially and more spaced at the distal end of the dorsal margin differentiate this species from other known species where the proximal teeth are compact and distal teeth are spaced namely C. meridionalis Roux (1926a) and C. indistincta Calman (1926) .

Caridina riverstoni sp. nov. differs from C. simoni in having a shorter rostrum with spaciously placed teeth on the dorsal margin (vs. longer rostrum with teeth on the proximal dorsal margin in C. simoni ), having 2–4 teeth on the ventral margin (vs. 5–14 teeth in C. simoni ), the inner pair of intermediate spines on the posterior margin of telson are shortest (vs. intermediate spines of equal length or the median pair fractionally longer in C. simoni ).

Figures

FIGURE 17. Caridina riverstoni sp. nov., AM P. 3935, Holotype ♂: a) Anterior region of cephalothorax; Paratype ♀: b) Anterior region of cephalothorax.

FIGURE 18. Caridina riverstoni sp. nov., AM P. 3935, Holotype ♂: a) First pereiopod; b) Second pereiopod; c) Third pereiopod; d) Dactylus of third pereiopod; e) Fifth pereiopod; f) Dactylus of fifth pereiopod; g) First male pleopod; h) Endopod of male first pleopod; Paratype ♀: i) First female pleopod; Holotype ♂: j) Second male pleopod; k) Appendix masculina; l) Telson; m) Posterior margin of telson; n) Uropod diaeresis spinules; o) Preanal carina.