Typton wasini Bruce, 1977

Bruce, A. J., 2010, Pontoniine Shrimps (Crustacea: Decapoda: Palaemonidae) from the CReefs 2009 Heron Island Expedition, with a review of the Heron Island pontoniine fauna, Zootaxa 2541 (1), pp. 50-68 : 61-63

Typton wasini Bruce, 1977

( Fig. 8 )

Typton wasini Bruce, 1977: 272–285 , figs. 1–6.

Typton nanus Bruce, 1987: 49–56 , figs. 1–5. — Davie, 2002: 339.

Typton sp. — Bruce, 2000: 98, fig. 9.

Material examined. (1) 1 ov. ♀, 1 juv. ♀, 2 juv. ♂, CLs 3.8, 1.6, 1.7, 1.4, QM W31916 ; Heron Island reef, north-eastern side, stn HI09-076E, 23°25.990’S 151°55.601’E, 10m, 22 November 2009, coll. N. Bruce & K. Schnabel ( QM W38196 ). (2) 1 ♀, 1, juv. ♀, 2 juv., CL 1.3 mm, 1.5 mm, 0.8 mm, 0.8 mm, data as above ( QM W31896) .

Diagnosis. The only Indo-West Pacific Typton species , with a dorsally dentate rostrum. Rostrum with 2-4 acute dorsal teeth; carapace with acute paraorbital spine. Sixth abdominal segment without posteromedian tooth. Scaphocerite less than half carpocerite length, acuminate, with or without obsolescent lamina. Mandible without incisor process. First pereiopod chela fingers subspatulate. Second pereiopods unequal, dissimilar, major chela and merus with ventral denticles in juveniles. Ambulatory dactyls biunguiculate, ventral corpus with 5–8 teeth. Exopod of uropod with distoventral tooth and spine.

Host. Dysidea sp. , [ Dysideidae : Demospongiae] (J.N.A. Hooper, pers. com., 2 March 2010).

Parasites. Orophryxux shiinoi Bruce, 1972 , [Hemiarthrinae: Bopyridae ], immature female, attached to host’s oral region. The association with Orophryxus shiinoi represents a new host record.

Distribution. First reported from Kenya, Wasin Channel (type locality) by Bruce (1977) and subsequently from Heron Island, Queensland ( Bruce 1981a). Also known from La Réunion ( Bruce 1983d), from Western Australia at 16°34' S 121°27' E, from 40–46 m, as Typton nanus Bruce, 1987 , and Abbot Point, Queensland, as Typton sp. ( Bruce 2000) .

Remarks. From lot (1), the ovigerous female specimen ( Fig. 8 ), CL 3.8 mm, agrees precisely with the original description and has the rostrum about 0.26 of CL, reaching almost to end of proximal antennular segment, with 3 small acute teeth. The corneal diameter is about 0.14 of CL. The major second pereiopod merus has two minute denticles on the ventral border.

The three smaller specimens agree closely with the description of Typton nanus Bruce, 1987 . This description was based on a single small specimen, CL 1.05 mm, considered to be a female of a small species due to the apparent presence of a single ovigerous seta distomedially on the basipodite of the first pleopod. Characteristic morphological features were the presence of three acute dorsal rostral teeth, a small acute antennal spine, a small acicular scaphocerite with the lamella obsolescent and the minor second pereiopod with a single small acute tooth at about 0.6 of the length of the ventral palmar margin, and with a similar tooth at 0.5 of the meral ventral length. The major second pereiopod was not preserved. The three small Heron Island specimens consist of a female, CL 1.8 mm, rostral dentition 3/0, with major second pereiopod only, merus with two ventral meral teeth, without ventral palmar teeth; juvenile male, CL 1.6 mm, rostral dentition 2/0, with both second pereiopods, major second pereiopod with two ventral meral teeth, without ventral palmar teeth, minor second pereiopod with minute ventral palmar tooth only; juvenile male, CL 1.5 mm, rostral dentition 2/0, with major second pereiopod only, merus and palm without ventral teeth. The male second pleopod appendix masculina is a single long spiniform seta.

These specimens show that the small ventral teeth on the second pereiopods are variable and decrease with growth, becoming virtually indiscernible in well grown adults. Typton nanus is clearly an early juvenile of T. wasini . Typton nanus Bruce, 1987 is now relegated to the status of a junior synonym of T. wasini Bruce, 1977 . From lot (1), the specimens had rostral dentitions of 3/0, 3/0, 2/0, 2/0 respectively. From lot (2), the larger specimens had rostral dentitions of 2/0, 2/0 and the smaller 1/0 and 3/0 respectively. Five specimens had both second pereiopods attached, one had neither, and two only a single second pereiopod attached, with two detached second pereiopods unattributable.

Bruce (2000) has also reported a Typton sp. from Abbot Point, Queensland, 15°53’S 148° 05’E (QM W24743), with a CL of 0.85 mm. The minor second pereiopod (the major limb is missing) has a minute tooth at the middle of the ventral margin of the merus. There is no reason to doubt that this specimen is also referrable to T. wasini . The T. nanus holotype specimen has a CL of 1.05 mm and is presumably an early juvenile stage. The Abbot Point specimen is even smaller, CL 0.85 mm, and may represent the first post-larval stage.

Typton wasini is particularly remarkable as the only Indo-West Pacific species of the genus with a dorsally dentate rostrum and lacking the mandibular incisor process.

Figures

FIGURE 8. Typton wasini Bruce, 1977, ovigerous female, Heron Island, QM W31916. A, carapace and rostrum. B, antennular peduncle. C, scaphocerite. D, major second pereiopod. E, same, fingers. F, minor second pereiopod chela. G, same, fingers. H, third pereiopod. I, same, propod and dactyl. J, same, distal propod and dactyl. K, dactyl.