Porcellanopagurus platei Lenz, 1902

Martin, Joel W., Moffitt, Robert B. & Mclaughlin, Patsy A., 2009, Additions to the decapod crustacean fauna of the Hawaiian Islands, II. First record of the unusual hermit crab genera Porcellanopagurus Filhol, 1885, and Solitariopagurus Türkay, 1986 (Decapoda, Anomura, Paguridae), Zootaxa 2057, pp. 53-62 : 54-59

publication ID	https://doi.org/ 10.5281/zenodo.186717
DOI	https://doi.org/10.5281/zenodo.6225671
persistent identifier	https://treatment.plazi.org/id/03AC879A-FFC3-FFD7-5A84-FBEAE8C37986
treatment provided by	Plazi
scientific name	Porcellanopagurus platei Lenz, 1902
status

Treatment

Porcellanopagurus platei Lenz, 1902 View in CoL

( Figs. 1A View FIGURE 1. A , 2 View FIGURE 2 , 3 View FIGURE 3 , 4A View FIGURE 4. A )

Porcellanopagurus platei Lenz, 1902: 740 View in CoL , pl. 23, fig. 2.— Balss, 1913: 66; 1930: 197.— Borradaile, 1916: 118.— Bennett, 1932: 473.— de Saint Laurent & McLaughlin, 2000: 116.

Material examined. Lectotype (herein selected), ♂ (SL = 4.2 mm), Juan Fernandez Island ( ZMB 10978). Paralectotype, ovigerous Ƥ (SL = 3.4 mm), same data as lectotype ( ZMB 10978).

Ovigerous female (SL = 3.6 mm), Hawaii, Penguin Banks (off southwest coast of Moloka'i), Pisces IV, Dive 178, 21º02.112'N, 157º19.163'W, 117 m, 1 Nov 2006 ( LACM CR 2006-013.1), collected on artifact (see Remarks below), inhabiting (wearing) shell of a limpet of the family Fissurellidae , tentatively identified by us as Emarginula hawaiiensis .

Description (based on type material above). Shield ( Fig. 2 View FIGURE 2 A) length distinctly less than maximum shield width. Rostrum broadly triangular, terminally acute or subacute and with weak, rounded median keel. Lateral projections also broadly triangular, terminally subacute to acute. First anterior carapace lobes not particularly well developed, terminally subacute and with weakly serrate lateral margins; second anterior carapace lobes narrowly subtriangular, terminally subacute. Posterior carapace lobes laterally extended beyond level of second anterior lobes, terminally subacute or acute and marginally weakly serrate. Posteromedian plate broad; sulci cardiobranchialis not clearly delineated.

Ocular peduncles approximately 0.4 of shield length; moderately stout; corneal diameter 0.6 of peduncular length. Ocular acicles quite small, not visible dorsally.

Antennular peduncles overreaching distal corneal margins by approximately 0.5 lengths of ultimate segments; ultimate segments each with few setae at dorsodistal margin.

Antennal peduncles very slightly overreaching distal corneal margins; fifth, fourth and third segments unarmed, second segment with dorsodistal angle produced, terminating acutely, dorsomesial distal margin rounded. Antennal acicle overreaching proximal margin of fifth peduncular segment, terminally rounded or blunt. Sternite of third maxillipeds with U-shaped median cleft and spinulose anterior margin.

Right cheliped ( Fig. 2 View FIGURE 2 C, missing in paralectotype) appreciably longer and stouter than left. Dactyl approximately as long as palm, articulating somewhat obliquely and slightly overlapped by fixed finger; dorsomesial margin rounded, with covering of large granules and sparse scattered setae, dorsal surface granular mesially, with few scattered tufts of sparse setae; cutting edge with few large calcareous teeth. Palm approximately as long as carpus; dorsomesial margin tuberculate, dorsal surface granular and with scattered tufts of sparse setae, but becoming nearly smooth centrally, dorsolateral margin with distinct ridge becoming granular on fixed finger, dorsal surface of fixed finger also granular; cutting edge with row of large calcareous teeth and tufts of sparse setae. Carpus with dorsomesial margin delimited by row of short, transverse ridges and scattered, moderately long setae, dorsal surface with numerous short, transverse, sometimes crenulate ridges and sparse setae, dorsolateral margin rounded. Merus with row of acute or subacute spinules on ventrodistal margin, spinule at ventrolateral distal angle and spinulose tubercles on ventrolateral margin; ventromesial margin spinulose, ventral surface with few scattered tubercles and long setae, or sparse tuft of long setae mesially (Hawaiian Ƥ).

Left cheliped ( Fig. 2 View FIGURE 2 D) with dactyl appreciably longer than palm; dorsomesial margin not delimited, dorsal surface with few scattered setae; cutting edge with row of small corneous teeth, terminating in small corneous claw. Palm with dorsal surface almost flat, with scattered short, transverse ridges and sparse setae, dorsomesial margin not delimited, dorsolateral margin with weak ridge, not extending full length of fixed finger. Carpus with short row of few small protuberances on dorsomesial margin, dorsolateral margin with similar row of short, transverse protuberances or ridges and tufts of setae, dorsal surface with numerous short, transverse, sometimes crenulate ridges and setae. Merus with row of small acute or subacute spines on ventromesial margin, row of slightly smaller spines on ventrolateral margin and few scattered tubercles and setae on ventral surface. Ischium with row of small spines on ventromesial margin.

Ambulatory legs ( Figs. 3 View FIGURE 3 A–C) generally similar. Dactyls shorter than propodi; dorsal surfaces unarmed but with few setae; ventral surfaces each with row of 8 or 9 corneous spines. Propodi each with row of spiniform protuberances and tufts of setae on dorsal surface; ventral surfaces each with row of 5–7 corneous spines, occasionally doubled, and few setae. Carpi each with dorsal row of small, often blunt spines and sparse setae; lateral surfaces each with longitudinal ridge in upper half. Meri stout; dorsal surfaces each with row of protuberances, sometimes spinulose, and sparse setae; ventromesial and ventrolateral margins each with row of small spines and few setae. Fourth pereopods ( Fig. 3 View FIGURE 3 D) semichelate, each with single row of corneous scales in propodal rasp. Fifth pereopods ( Fig.3 View FIGURE 3 E) chelate. Coxae of male fifth pereopods ( Fig. 2 View FIGURE 2 B) with gonopores opening mesially.

Sixth pleonal tergite ( Fig. 2 View FIGURE 2 E) divided into approximately equal halves, posterior half divided by prominent median sulcus; uropods symmetrical, protopods lacking posterior directed spines. Telson ( Fig. 2 View FIGURE 2 E) contiguous with sixth pleonal tergite; divided into anterior and posterior portions by prominent lateral incisions, posterior lobe with terminal margin rounded, entire or with tiny and very faint median indentation; anus terminal.

Coloration. We have photographs taken of the specimen after it was collected and still onboard the ship. Unfortunately the specimen was not frozen prior to preservation and photography, and so undoubtedly it had faded somewhat from color in life. Based on these photographs (in the collection of RBM), the overall coloration on the shield and appendages is a very pale ivory or white, with some translucent areas. The central part of the shield has a triangular dark area where darker internal structures (most likely the stomach) are visible through the translucent shield. The eyestalks are slightly darker, approaching beige or light tan. The eggs in the photograph, carried dorsally, are bright yellow. One year after collecting and preservation, the carapace and legs are a pale or translucent white ( Fig. 4A View FIGURE 4. A ). The eggs are still yellow but are faded somewhat from their original condition.

Remarks. The ovigerous female from Penguin Banks ( Fig. 1A View FIGURE 1. A , 4A View FIGURE 4. A ) differs from the lectotype in having more irregularly bilobed first lateral carapace lobes, a sparse tuft of long setae mesially on the ventral surface of the right carpus, and longer, slenderer ambulatory legs. Porcellanopagurus edwardsi Filhol, 1885 , and P. filholi de Saint Laurent & McLaughlin, 2000, also have a characteristic tuft of setae on the ventral surface of the merus of the right cheliped, which has been described by de Saint Laurent & McLaughlin (2000) as dense in P. filholi , but varying from sparse to dense in P. e d w a rd s i. The male lectotype of P. platei has several long setae ventromesially on the right merus, but they do not form a distinct tuft as they do in the Hawaiian female. With the right cheliped missing from the paralectotype, it is not presently possible to know whether this setation is a dimorphic character in this species or represents geographic variation.

As indicated in the material examined, Lenz’s (1902) syntypes consisted of one male and one ovigerous female. Lenz reported that two ovigerous females had been collected, although, his figure (pl. 23, fig. 2), which lacked pleopods, suggested that a male was illustrated. However, Balss (1930), after reexamining Lenz’s syntypes, stated that the pleon of the larger specimen was torn, thus Lenz’s (1902) figure was inaccurate. Despite Balss’ (1930) correction of Lenz’s (1902) claim of a pair of small first pleopods in P. platei, Balss (1930) still reported both of the syntypes as female. Apparently he was still unable to correctly sex specimens of Porcellanopagurus . He previously had described Porcellanopagurus japonicus Balss, 1913 , on the basis of a single specimen that he identified as a male. But as Borradaile (1916) pointed out, Balss’ (1913) illustration was obviously of a female. Males of Porcellanopagurus lack pleopods entirely.

Lenz (1902) also commented that the collector had noted the female’s eggs were covered by a mussel shell. However, Lenz discounted the observation as being erroneous because he didn’t believe a mussel shell could conceal the eggs attached to the pleopods. Several subsequent reports of the use of bivalve shells by species of Porcellanopagurus have shown that it was Lenz who was in error.

As discussed by de Saint Laurent & McLaughlin (2000), Balss (1930) and Bennett (1932) considered P. platei closely related to, if not synonymous with, P. e d w a rd s i. However, de Saint Laurent & McLaughlin (2000) demonstrated that P. e d w a rd s i had been confounded with P. filholi for many years. Based on Lenz’s (1902, pl. 23, fig, 2) figure, de Saint Laurent & McLaughlin (2000) considered the carapace lobes of P. p l a t e i more reminiscent of P. filholi , but the illustrated short, stout pereopods more closely resembled P. e d w a rd s i. As noted above, the female from Penguin Banks does have longer and slenderer second and third pereopods, a character shared with P. filholi . The Hawaiian specimen, however, more closely resembles P. p l a t e i in having a shorter rostrum, somewhat differently shaped first lateral carapace lobes, fewer spines on the ventral margins of the ambulatory dactyls, and a telson that lacks a distinct median cleft. Judging from the ovigerous condition of the paralectotype, females of P. p l a t e i mature at a smaller size than do those of P. filholi .

This is the first report of P. platei since its original description more than a century ago. It is also a major range extension (from the Juan Fernandez Islands off the western coast of southern Chile), and the first record of the genus in the Hawaiian Islands. The Hawaiian specimen was collected during the recovery of some equipment on a submersible dive; the hermit crab was within the empty casing of an old "pinger" that had been deployed some twenty years earlier (the "artifact" noted above). The fact that the specimen was found in a limpet shell (the fissurellid Emarginula hawaiiensis ) is not unusual for the genus; several other species are known to carry limpet shells (McLaughlin 2000).