Periclimenaeus arthrodactylus Holthuis, 1952

Bruce, A. J., 2006, Periclimenaeus nielbrucei sp. nov. (Crustacea: Decapoda: Pontoniinae), a new sponge associate from the Capricorn Islands, Queensland, with notes on related Periclimenaeus species, Zootaxa 1224, pp. 1-22 : 14-15

Periclimenaeus arthrodactylus Holthuis, 1952

( Fig. 7 G–I)

Periclimenaeus arthrodactylus Holthuis, 1952: 122 –125, figs. 51–53. — Li, 2000: 117, fig. 128.

Material examined

1 ovig. Ψ, holotype, CL 2.1 mm, Siboga stn 37, Pulau Sailus ketjil, Indonesia, dredge to 18 m, 30/ 31 March 1899. ZMA De. 102518.

Remarks

Body and anterior appendages intact, complete, except left eye (missing); without attached pereiopods. One detached first pereiopod, both second pereiopods and two ambulatory pereiopods. First to third maxillipeds in situ. One maxillula (without lower lacinia), one damaged maxilla (upper lacinia missing) only loose mouthparts preserved.

Small inferior orbital angle present; first abdominal segment without anterodorsal lobe; proximal segment of antennule with very long slender projecting ventromedial tooth; first pereiopod fingers ( Fig. 7 G) densely setose, fixed finger bidentate, cutting edges obsolete; fourth pereiopod dactyl ( Fig. 7 H) elongate, unguis clearly demarcated, tip missing, about 0.12 of corpus length, 3.3 times longer than basal width, with 4 small ventral denticles, corpus slightly curved, ventrally concave, about 7.0 times loner than basal width, with two minute ventral denticles on proximal fifth, without setae; propod with well developed medial and lateral distoventral spines, three ventral spines, merus with 7 very small denticles ventrally; fifth pereiopod dactyl similar, unguis ( Fig. 7 I) with 6 small ventral denticles, corpus with small acute distal accessory tooth, with single minute denticle proximally; propod with single distal ventral spine only.

The holotype specimen was fully described by Holthuis (1952), who remarked on the “remarkable nature of the last three pereiopods”. As he noted, only two ambulatory pereiopods were preserved. These were considered to be the third and fourth pereiopods. In my opinion, they are actually the fourth and fifth pereiopods and the details of the third pereiopod, particularly the dactyl, remain unknown. Holthuis does not mention the minute proximal ventral denticles on the ambulatory dactyls, and states that they are unarmed. They may be compared with the same appendages in P. nielbrucei , which show a considerable degree of dactylar variation, from third, relatively “normal” for the genus, short, and strongly denticulate, to fourth, more attenuated, with reduced denticulation, and fifth, very elongate, with loss of all denticulation from the corpus of the holotype. The dactyl of the third pereiopod of P. arthrodactylus may be expected to be shorter, with the corpus deeper and more strongly denticulate. The dactylar ungues are reported to be articulated, but that of the fourth pereiopod (Holthuis’s third) appears to have sustained minor in vivo damage. The fifth appears undamaged and similar to the unguis in many other species of Periclimenaeus , with a small acute distal accessory tooth on the corpus.. The dactylus of the fifth pereiopod of P. nielbrucei exhibits a definite resemblance to those of P. arthrodactylus .

This species is still known only by the holotype specimen collected in 1899. Its host is unknown.

Figures

FIGURE 7. Periclimenaeus holthuisi Bruce, 1969, ovigerous female holotype. A, mandible, distal incisor process. B, first pereiopod, finger tips, dactyl uppermost. C, third pereiopod, propod and dactyl. D, same, distal propod and dactyl. E, fourth pereiopod, distal dactyl. F, same, dactylar accessory tooth. Periclimenaeus arthrodactylus Holthuis, 1952, ovigerous female holotype. G, first pereiopod, fingers of chela. H, fourth pereiopod, distal propod and dactyl. I, fifth pereiopod, distal dactyl.