Periclimenaeus zanzibaricus Bruce, 1969

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 : 15-20

Periclimenaeus zanzibaricus Bruce, 1969

( Fig. 8–9 )

Periclimenaeus zanzibaricus Bruce, 1969: 174 –175. — Bruce, 1976: 474.

Material examined

(1) 1 ov. Ψ allotype, RMNH D.51673; 4, 6 ovig. Ψ, 1 Ψ, 1 juv., Uroa, Unguja, Zanzibar, 21 March 1960, AJB 289A, AJB 289/1­12, unidentified sponge, shore pools at neap tide, paratypes, RMNH D. 51674; 1 spm, paratype, BMNH 2006. 407–408. (2) 1 ɗ, 1 ovig. Ψ, 2 juv, CLs 1.8, 2.5, 1.5, 1.5 mm, stn AJB/59, Myora, North Stradbroke Island, Queensland, 1 July 1969, QM W27989. (3) 1 ɗ, 1 ov. Ψ, CLs 1.9, 3.3 mm, Mombasa Island, Kenya, 11 December 1973, AJB 2086, seaward reef, reef pools, at LWS, USNM 1086753.

Remarks

Bruce (1969) provided only an un­illustrated preliminary description of this species, which has not been further reported since that date. The holotype was deposited in the Rijksmuseun van Natuurlijke Historie collection. Further specimens collected simultaneously with the type and other material has now been studied. Periclimenaeus zanzibaricus was initially considered most closely related to P. rhodope ( Nobili 1904) , which at that time was known with certainty only from Nobili’s description and figures, the species referred to P. rhodope by Holthuis (1952) having been re­named P. holthuisi Bruce, 1969 (see above). Further details of P. rhodope were provided by Bruce (1974) after the re­examination of Nobili’s type material held in the collections of the Muséum National d’Histoire Naturelle. The preliminary description of P. zanzibaricus may be amplified by the following details from dissected specimens QM W27989 (289/7 and 289/ 8). The allotype male of P. zanzibaricus is held in the collection of the Nationaal Natuurhistorisch Museum, Leiden, Crust.D.25615.

Description

Rostrum ( Fig. 8 B) slender, about 5.5.times longer than central depth, about 0. 4 of CL, reaching to distal margin of intermediate antennular segment, tip slightly up­turned, dentition 6­7/1, (one small specimen with 5/1, one with 6/0, but tip appears damaged), dorsal teeth all anterior to orbital margin, broadly acute, with 2–3 interdental setae, ventral margin straight, ventral tooth well developed, small, acute, projecting horizontally. Supraorbital tubercle well developed, strongly acute.

Carapace ( Fig. 8 A) with antennal spine robust, very acute, slightly postmarginal. Inferior orbital angle ( Fig. 8 C) well developed, broadly rounded, reflected below lateral orbital rim, with small rounded distomedial lobe.

First abdominal tergite without anteromedian lobe.

Telson ( Fig. 8 K) about 0.6 of CL, 2.5 times longer than anterior width, lateral margins convex, posteriorly convergent, with large submarginal dorsal spines at 0.13 and 0.22 of length, anterior spines 0.2 of telson length, anterior spines 1.18 times posterior spine length, posterior margin rounded with small acute median point, posterior spines ( Fig. 8 L) well developed, lateral spines subdorsal, about 0.33 of intermediate spine length, intermediate spine robust, about 0.25 of telson length, submedian spines more slender, densely setulose.

Antennular peduncle ( Fig. 8 D) with proximal segment of the peduncle with acute stylocerite reaching to about 0.5 of segment length, with small ventromedial tooth at similar level; anterolateral lobe ( Fig. 8 E) acutely produced as triangular process rather than rounded lobe with lateral tooth.

Antenna ( Fig. 8 F) with subcylindrical carpocerite, about 2.5 times longer than wide, reaching to about 7.2 of scaphocerite length; scaphocerite ( Fig. 8 G) about 4.3 times longer than wide, broadly rounded distally, with very robust distolateral tooth at 0.85 of length, about 0.16 of scaphocerite length and far exceeding lamella.

Eye ( Fig. 8 H) with hemispherical cornea, well pigmented, with diameter about 0.8 of stalk length.

Mouthparts similar to those of P. nielbrucei , but incisor process ( Fig. 8 I) obliquely rounded distally with about 12 long acute teeth, largest laterally and of decreasing size medially.

First pereiopod ( Fig. 9 A) slender, reaching to exceed carpocerite by carpus and chela, chela ( Fig. 9 B) with palm about 3.0 times longer than wide, oval in section, slightly swollen proximally, with fingers ( Fig. 9 C) about 0.45 of palm length, broad, distally rounded, with entire lateral cutting edges, tips with articulated ungues, flanked by small teeth; with numerous strong setae; carpus about 0.85 of merus length,.6.5 times longer than distal width, tapering uniformly proximally; merus 1.1 times carpus length, 8.5 times longer than maximal width; ischium slightly shorter than chela, about 2.6 times longer than width; basis and coxa normal, coxa without distoventral process.

Second pereiopods well developed, rather similar and slightly unequal.

Major second pereiopod with chela ( Fig. 9 D) about 1.10 of CL; with palm of chela subcylindrical, oval in section, twice as long as deep, dorsal and ventral margins subparallel, with strongly marked rounded shoulder dorsally over base of dactylus; fingers ( Fig. 9 E,F) 0.5 of palm length, dactylus about 0.6 of palm length, slender, about 3.0 times longer than maximal depth, compressed, distally up­turned, dorsal margin smoothly convex, with stout acute tip distally, cutting edge broadly convex with inconspicuous low thickening centrally over one third of length, distal third entire, not sharp, non­denticulate, fixed finger about 1.7 times longer than basal width, 0.85 of dactylus length, deeply grooved with small shallow fossa with thickened ventral flange proximally, medial margin with large acute tooth proximally, fingers with numerous long simple setae; carpus, merus, and proximal segments similar to P. rhodope .

Minor second pereiopod chela ( Fig. 9 H) similar, about 0.8 of major chela length; with palm of chela subcylindrical, oval in section, twice as long as deep, dorsal and ventral margins sub­parallel, with strongly marked rounded shoulder dorsally over base of dactylus, dactylus ( Fig. 9 I) about 0.58 of palm length, slender, about 3.0 times longer than maximal depth depth, compressed, distally in­turned, dorsal margin smoothly convex, with stout acute tip distally, cutting edge broadly convex with entire, sharp, nondenticulate, thickening posteriorly, fixed finger about 1.8 times longer than basal width, 0.95 of dactylus length, grooved with small depression with thickened edge proximally, medial margin with low acute tooth proximally, fingers with numerous long simple setae; carpus, merus, and proximal segments similar to P. rhodope .

Ambulatory pereiopods are generally similar to those of P. rhodope : third pereiopod with dactylus ( Fig. 8 J) about 0.3 of propod length, unguis ( Fig. 9 K) well demarcated, 3.0 times longer than basal width, 0.45 of dorsal corpus length, moderately curved, concave ventral margin with 5 small acute teeth, corpus 2.1 times basal width, dorsal margin feebly convex, ventral margin with strong, broad acute distoventral accessory tooth, about 0.33 of unguis length, ventral margin feebly convex with 10 small denticles, central denticles largest, most acute, distally directed; propod ( Fig.9 J) about 0.4 of CL, 5.0 times longer than proximal depth, tapering slightly distally, with 2 strong distoventral spines, 7 equally spaced ventral spines, most proximal ventral spine with 2 smaller adjacent accessory spines; proximal segments as in P. rhodope . Fourth and fifth pereiopods similar; fourth propod with pair of distoventral and 4 ventral spines, 1 accessory spine; fifth propod with numerous setae distally, 1 distoventral spine, 3 ventral spines; dactyls similar to third, slightly more slender, denticulation slightly reduced, fifth dactyl not elongate. Pleopods and uropods without special features, as in P. rhodope , exopod of uropod with small acute distolateral tooth ( Fig. 8 M) with strong articulated spine separated by small gap. Ova numerous, of normal size, length about 0.5 mm. Largest male, CL 2.7 mm, largest female, 3.3 mm.

The adult Myora specimens (QM W. 27989) also have a rostral dentition of 7/1 and exactly resemble the Zanzibar specimens except that the male major second pereiopod dactyl shows an elongated thickening, corresponding to the molar process, extending along almost the whole length of the dactylar cutting edge ( Fig. 9 L). This feature is less marked in the female, which more closely resembles the Indian Ocean material. The inferior orbital angles in the two lots of specimens are identical.

Although not mentioned in the original diagnosis of the genus ( Borradaile, 1915), the most characteristic feature of the genus Periclimenaeus is “The dactylus of the larger second pereiopod with a molar tooth, socket in the fixed finger” ( Holthuis, 1993), although it may be noted that a remarkably similar sound producing mechanism is also present in some species of Coralliocaris Stimpson and is well known in several alpheid genera. In P. zanzibaricus this mechanism is particularly poorly developed. The shapes of the fingers of the major and minor chela are also remarkably similar. This may illustrate the path by which the mechanism has evolved, from a simple thickening of the posterior part of the dactylar cutting edge opposing a longitudinal groove on that of the fixed finger. The molar process may have developed from this thickening, rather than a pre­existing tooth in this situation, as found in many other pontoniine shrimps.

Figures

FIGURE 8. Periclimenaeus zanzibaricus Bruce, 1969, ovigerous female paratype, 289 / 7. A, carapace and rostrum. B, rostrum. C, left inferior orbital angle, dorsal. D, antennule. E, same, proximal segment, distolateral angle. F, antenna. G, same, scaphocerite. H, eye, dorsal. I. mandible, incisor process. J, third pereiopod, dactyl. K, telson. L, same, posterior spines. M, uropod, distolateral exopod.

FIGURE 9. Periclimenaeus zanzibaricus Bruce, 1969, ovigerous female, paratype, 289 / 7. A, first pereiopod. B, same, chela. C, same, fingers. D, antennule. E, same, proximal segment, distolateral angle. F, antenna. G, scaphocerite. H, eye. I, mandible, incisor process. J, third pereiopod, dactyl. K, telson. L, same, posterior spines. M, uropod, exopod, distolateral angle.