Procaris noelensis, Bruce, A. J. & Davie, P. J. F., 2006

Bruce, A. J. & Davie, P. J. F., 2006, A new anchialine shrimp of the genus Procaris from Christmas Island: the first occurrence of the Procarididae in the Indian Ocean (Crustacea: Decapoda: Caridea), Zootaxa 1238, pp. 23-33 : 24-29

Procaris noelensis sp. nov.

( Figs 1–3 )

Procaris n. sp. — Humphreys & Eberhard, 2001: 64, 66 (not pl. 2 on p. 65, which is presumed to be Antecaridina lauensis (Edmondson) ( Atyidae ))

Undescribed procarid sp. — Jones & Morgan, 2002: 211 (not colour picture on this page which is presumed to be Antecaridina lauensis (Edmondson) ( Atyidae )).

Diagnosis

Rostrum slightly exceeding both lobes of eye, carapace with distinct cervical groove, eye lobes well developed with medial lobe longer than lateral, stylocerite reaching to middle of second segment peduncle, carpocerite exceeding scaphocerite, scaphocerite with small distolateral tooth, first and second pereiopods with ischial spines well developed, third abdominal tergite posterodorsally produced, reaching to about middle of fourth segment, fifth abdominal pleuron posteroventrally angular, sixth abdominal segment with posteroventral angle posteriorly produced, rounded.

Description

Generally in a rather fragile state. All pereiopods detached, six preserved, including both pairs of first and second pereiopods. Thoracic exopods all detached except on the left second maxilliped; the left third maxilliped still attached; distal half of telson missing.

Carapace ( Fig. 1 ) smooth, without spines, with oblique cervical sulcus, without cardiac notch, anterolateral angle obtusely rounded, not produced, not emarginate.

Rostrum ( Fig. 2 A, B) triangular, acute, slender in lateral, narrow in dorsal views, ventrally concave, without dorsal or ventral carina, toothless, exceeding level of distal end of medial eye lobe.

Ophthalmic somite simple, without median process or pigment spot. Eye ( Fig. 2 A, B, C) half covered dorsally by anterior margin of carapace, fully exposed laterally; eyestalks proximo­medially ankylosed, immobile; short, bilobed, medial lobe longer than lateral, conoidal, unpigmented, lateral lobe shorter, hemispherical, well pigmented, cornea not facetted.

Antennule ( Fig. 2 D) with peduncle robust, proximal segment subcylindrical, about 1.6 times longer than central width, without ventromedial tooth, very obliquely articulated with intermediate segment, stylocerite long, acute, slender in dorsal view, broad in lateral view, reaching to near distal margin of intermediate peduncular segment, statocyst small, poorly developed, without statolith; intermediate segment as long as wide, medial length subequal to medial length of proximal segment; distal segment slightly longer than intermediate segment with rounded setose lobe distally between flagella; flagella as in other Procaris species.

Antenna ( Fig. 2 E) with coxal segment exposed, robust, with large rounded antennal gland tubercle medially, basicerite stout, laterally unarmed, ischiocerite and merocerite linear, short, subequal, carpocerite subcylindrical, 5.5 times longer than central width, 1.8 times longer than combined ischio­merocerite length, well exceeding distal end of scaphocerite lamella; scaphocerite ( Fig. 3 A) well developed, 2.5 times longer than maximal width at 0.3 of length, tapering distally, anterior margin broadly rounded, lateral margin straight, with small acute tooth ( Fig. 3 B) at about 0.92 of lamella length; flagella missing.

Epistome ( Fig. 2 A) strongly protuberant, semi­globular, glabrous, laterally exposed.

Mouthparts. Not dissected.

Third maxilliped similar to other Procaris species, reaching distally to end of antennular peduncle; ischium lamelliform ( Fig. 3 C) about 4.0 times longer than proximal width, expanding slightly distally, ventral edge uniformly serrate throughout most length, with small acute teeth ( Fig. 3 D).

Pereiopods generally as in other Procaris species. The three anterior pairs of pereiopods have well developed spines on the ventral ischia, about 0.225 mm long or about 0.18 of the ischial length; bases without acute tooth proximodorsally; dactyls of anterior pereiopods held in strongly flexed position, forming feebly sub­chelate mechanism ( Fig. 3 E).

Abdomen smooth, third segment posterodorsally produced, extending over anterior half of fourth segment with abdomen extended, pleura of first four segments rounded, fifth angular, sixth segment ( Fig. 2 F) about 0.3 of CL, 1.75 times longer than anterior depth, posterolateral angle large, rounded, posteroventral angle small, posteriorly produced, rounded, ventral margin strongly setose.

Telson: anterior portion presents no special features; posterior part broken away.

Pleopods similar to other Procaris species.

Uropods ( Fig. 3 F) similar to other Procaris species, protopod posterolaterally acute, exopod with posterolateral angle dentate and bispinose ( Fig. 3 G), diaeresis obsolete.

Habitat

Only recorded from a single female collected in Runaway Cave (Cave CI­2 of Humphreys & Eberhard 2001). Runaway Cave is a tidally influenced freshwater/ anchialine habitat. It is presumed to be connected to two adjacent anchialine caves, an unnamed cave CI­54, and The 19th Hole (CI­19), and together probably form a single anchialine system. Procaris noelensis will thus presumably be found to be spread more widely through the cave systems. Within Runaway Cave, P. noelenis co­occured with a hippolytid shrimp Parahippolyte (? P. uvea Borradaile, 1899 ), and an atyid shrimp Antecaridina lauensis (Edmondson) .

Within the wider cave system (CI­2, CI­19, CI­54) the identified aquatic fauna includes: Scyllidae indet. (Polychaeta); Nerilla sp. (Archiannelida: Nerillidae ); Microceratina martensi Namiotko et al. (Ostracoda: Cytheruridae ); Danielopolina sp. ( Thaumatocyprididae : Halocyprida ) (Humphreys & Danielopol in press); Nitocrella / Nitokra complex ( Harpacticoida : Ameiridae ); Bryocyclops muscicola (Menzel) ( Cyclopoida : Cyclopinidae ); a new copepod genus ( Calanoida : Arietellidae ); Leucothoe sp. ( Amphipoda : Leucothoidae ); Alpheidae indet. ( Decapoda ); Parahippolyte (? P. u v e a Borradaile) ( Decapoda : Hippolytidae ); Antecaridina lauensis (Edmondson) ( Decapoda : Atyidae ); Macrobrachium lar (Fabricius) ( Decapoda : Palaemonidae ); Gobioidae indet. (Pisces: Perciformes ); unidentified Eleotridae (Pisces: Perciformes ) (see Humphreys & Eberhard, 2001; Namiotko et al., 2004);? Eleotris fusca (Forster, 1801) (Eleotridae) ( Humphreys & Eberhard 2001; Namiotko et al. 2004).

In general, according to Humphreys & Eberhard (2001), the cave waters are all well oxygenated (dissolved oxygen>73% saturated) and the pH (7.65±0.41, N=13), with the marine caves having salinities ranging from 0.39–16.5 g L ­1 TDS (sea water c. 36 g L ­1 TDS). Specific physico­chemical measurements for Runaway Cave, and the adjacent The 19th Hole, are presented in Table 1 . Runaway Cave is brackish with salinities ranging from about 9–18 ppt. No measurements deeper than 2 m were taken so it is not known if deeper waters become suboxic as reported for many other anchialine systems ( Sket 1996; Humphreys 1999; Iliffe 2000).

Figures

FIGURE 1 Procaris noelensis sp. nov., holotype, Christmas Island. Scale bar in millimeters.

FIGURE 2 Procaris noelensis sp. nov., holotype, Christmas Island. Anterior carapace and appendages, lateral. B, same, dorsal. C, eye, upper, dorsal; lower, lateral. D, antennule. E, antenna.

FIGURE 3 Procaris noelensis sp. nov., holotype, Christmas Island. A, scaphocerite. B, same, distlateral angle. C, third maxilliped, ischium, distal edge to left. D, same, cutting edge. E, third pereiopod (?), propod and dactyl. F, uropods. G, same, posterolateral exopod.