Pinnotheres pectunculi Hesse, 1872

Becker, C. & Türkay, M., 2010, Taxonomy and morphology of European pea crabs (Crustacea: Brachyura: Pinnotheridae), Journal of Natural History 44 (25 - 26), pp. 1555-1575 : 1569-1573

Pinnotheres pectunculi Hesse, 1872

( Figure 1F, G, 6A–D )

Pinnotheres pectunculi Hesse, 1872 , p 36 –38 (no depository of types, type-locality: coast of Brittany, France); d’Udekem d’Acoz, 1988, p 195 –201, figures 24–25, 28, 30, 32–33; Pinnotheres pisum forma pectunculi: Bourdon, 1965, p 32 , 40

Material examined

Northeast Atlantic. France, Brittany: 1♀, host: Glycymeris glycymeris , region of Dinard , east of “des Haches”, 48°38′N, 2°3′W, April 1993, leg. C. d’Udekem d’Acoz ( SMF 33459) . 1♀, host: Glycymeris glycymeris, Pointe de Bilfot, Plouézec , 48°45′N, 2°56′W, 9 April 1993, leg. C. d’Udekem d’Acoz ( SMF 33460) . 3♀, host: Glycymeris glycymeris, Bay of Morlaix, Île Callot , 11 April 1986, leg. C. d’Udekem d’Acoz ( SMF 34002) . 40♀, 38♀ ovigerous, host: Glycymeris glycymeris, Roscoff , ring dredge, May 1990, leg. J. Klein ( SMF 34252–SMF 34294, SMF 34390–SMF 34399, SMF 34460– SMF 34484) . 48♀, 3 juvenile stage III–IV, 2♀ ovigerous, host: Glycymeris glycymeris, Bay of Morlaix , ring dredge, May 1991, leg. J. Klein ( SMF 34332) . 13, 3♀ juvenile, 3♀ juvenile hard stage, 1♀ juvenile stage II, host: Glycymeris glycymeris, Roscoff , ring dredge, April 1991, leg. J. Klein ( SMF 34295- SMF 34303) . 3♀ juvenile, Notes: Scale bars, 1 mm (A), 500 µm (B), 200 µm (C) .

host: Venus verrucosa, Roscoff , ring dredge, April/ May 1990 /1991, leg. J. Klein ( SMF 34304– SMF 34306). 13, 10♀, host: Venus verrucosa, Roscoff , ring dredge, April / May 1990 /1991, leg. J. Klein ( SMF 34307–SMF 34313, SMF 34383) . 13, 1♀, host: Circomphalus casina, Roscoff , ring dredge, April / May 1990 /1991, leg. J. Klein (SMF 34314, SMF 34315) . 1♀, 1♀ juvenile hard stage, host: Clausinella fasciata, Roscoff , ring dredge, April / May 1990 /1991, leg. J. Klein (SMF 34316, SMF 34517) . 33, 1♀ juvenile, 3♀ juvenile hard stage, 1♀ juvenile stage II, 1♀ juvenile stage II–III, host: Glycymeris glycymeris, Roscoff , ring dredge, April / May 1990 /1991, leg. J. Klein ( SMF 34321–SMF 34328, SMF 34384– SMF 34386) . 23, 1♀ juvenile hard stage, host: Clausinella fasciata, Roscoff , ring dredge, April 1991, leg. J. Klein ( SMF 34327– SMF 34329) . 23, host: Circomphalus casina, Roscoff , ring dredge, 1991, leg. J. Klein (SMF 34330, SMF 34331) . 9♀, host: Circomphalus casina, Roscoff , ring dredge, April 1991, leg. J. Klein ( SMF 34335- SMF 34373) . 13, 1♀, host: Circomphalus casina, Roscoff : Stat. 9, beam trawl, April 1991, leg. J. Klein (SMF 34387, SMF 34388) . 1♀, host: Clausinella fasciata, Roscoff : Stat. 9, beam trawl, April 1991, leg. J. Klein ( SMF 34389) . 56♀, host: Glycymeris glycymeris, Roscoff , May 1990, leg. J. Klein ( SMF 34485– SMF 34540) . 20♀, host: Glycymeris glycymeris, Roscoff , October 2005, leg. W. Thomas, Station biologique de Roscoff ( SMF 34333) . 63♀ ovigerous, 1♀ stage IV, host: Glycymeris glycymeris, Roscoff , 21 May 2008, leg. L. Lévèque, Station biologique de Roscoff ( SMF 34334) . 1♀, larvae zoea 1, host: Glycymeris glycymeris, Roscoff , 1 August 2005, leg. T. Wehe ( SMF 34578) .

France, unspecified locations: 1♀ juvenile, 15 April 1987, leg. C. d’Udekem d’Acoz ( SMF 33458). 1♀, host: Glycymeris glycymeris , France, fishmarket close to La Sausaie , February 1982, leg. H. Nesemann ( SMF 34004) .

Male

General description. Very similar to P. pisum (see figure 4A). Males of P. pectunculi infrequently found inside host. Present study based on preserved material, therefore no information on general colour, possible ornamentation and colouration of eyes available. Carapace rounded, dorsally very convex, strongly calcified, not translucent, without defined regions and lateral teeth. Surface of carapace smooth, shiny, without setae. Front very pronounced, slightly acuminated in middle. Eyes clearly visible in dorsal view.

Chelipeds, walking legs and third maxillipeds generally consistent with description for female given later, but chelipeds generally much stronger and stouter than in adult females. Second and third pair of walking legs (P3, P4) with swimming fringes: two rows of setae on distal articles: one runs dorso-posteriorly on carpus and propodus, another ventro-anteriorly. Dorsal and ventral margin of walking legs (P2–P5) lined with shorter setae.

Maximum carapace width of males about 5 mm in the dog cockle Glycymeris glycymeris .

Pleon (abdomen) and sternum ( Figure 6B ). Male abdominal segments clearly separated. Belonging to thoracotremata, male gonopores located on sternum. Pleon tapering from proximal to distal segments, tapering stronger, less gradual than in P. pisum . Shape of pleon less triangular than in P. pisum , rounded, especially telson. Outer margin of pleon lined with setae, remaining surface smooth.

First gonopod ( GP 1) ( Figure 6C, D ). Gonopods flattened dorso-ventrally, tapering by degrees from base to tip. Curvature towards lateral side of body gradual from proximal base of gonopod to distal opening of ejaculatory canal. Whole limb sickle-shaped. Tapering to distal opening gradual, regular along total length. With same plumose setae as in P. pisum , but highest density less distal to tip, more concentrated in flexed region.

Female

General description ( Figure 1F, G). Very similar to P. pisum (see Figure 5A ). General colour light ivory, nearly white. Carapace subglobular or slightly wider than long, especially in large females. Carapace very soft, translucent through decalcification, without defined regions and lateral teeth. Eyes hardly visible in dorsal view, especially in large females. Eyes with light orange colouration in living specimens. Carapace, as well as whole body surface, smooth and shiny owing to lack of setae. Pleon very broad, rounded, covering whole ventral side and coxae, reaching front anteriorly. Pleons’ margin setose, outer surface smooth.

Maximum carapace width around 10 mm in adult females from Glycymeris glycymeris , minimum carapace size in ovigerous females from Circomphalus casina about 5 mm. Juvenile females consistent with description of males (except for pleopods).

Chelipeds and walking legs ( Figure 6A ). Palm of cheliped very slender in adult females, appearing generally slightly more slender than in P. pisum . Chelipeds of juvenile females stouter, number and arrangement of teeth, setae types and their distribution identical to P. pisum (see Figure 5B ). Movable finger (dactylus) with one single pointed tooth. Fixed finger (propodus) with one tooth followed by additional small tooth. Small tooth is only feature to distinguish females of P. pectunculi and P. pisum . Setae types and grouping on claw identical.

Principal part of palm plain and smooth, showing only scattered setae. Simple and pappose setae located on cutting edge of claw and near angle of propodus and dactylus. Bottom side of claw with field of long pappo-serrate setae forming dense comb.

Walking legs (P2–P5) slender with short, pointed and curved dactyli, considerably less than half as long as propodus. Dactyli of almost equal length in all walking legs. Swimming fringes of second and third walking leg (P3, P4) present in juvenile females, reduced in adults.

Third maxilliped. Third maxilliped not different from P. pisum (see Figure 5C ), with large completely fused merus-ischium-article. Dactylus of palp inserted underneath propodus (subterminally). Flagellum two-segmented with tuft of long simple setae originating from its tip. Third maxillipeds’ inner margins densely fringed with long simple setae, but surfaces of merus-ischium-article, carpus and propodus smooth.

Juvenile females very similar to males, except for slight differences in shape of pleon and abdominal appendages.

Comments

The first description of Pinnotheres pecunculi was by Hesse (1872). From the fact that the specimens found in the dog cockle, Glycymeris glycymeris , were much smaller than Pinnotheres pisum from the blue mussel, Mytilus edulis , Hesse already concluded there must have been two separate species. Furthermore, Hesse described that the first antenna had five articles and that the male carapace showed an orange ornamentation.

Bourdon (1965) mentioned specimens from Glycymeris glycymeris and indicated that these might have been a new species, but since he had seen the need for further investigations, he carefully called his specimens Pinnotheres pisum forma pectunculi . Bourdon described the additional tooth on the fixed finger of the claw in the female and mentioned that the walking legs were more pilose than in P. pisum (1965) . In addition to this, he indicated the infection rate for P. pectunculi , but he didn’t give any statement for the incidence of males.

Bourdon also mentioned the presence of N. pinnotheres in Ascidia mentula and in Ostrea edulis , while he was claiming that P. pisum did not inhabit Ostrea edulis , but was also found in ascidians. Our present study suggests that both is incorrect: while we never found N. pinnotheres in Ostrea edulis , P. pisum was not present in ascidians (see examined material).

The origin and relationship of P. pectunculi is not yet clear. Since its distribution and host range seems so far to be very restricted, it might be a relatively new species. Next to its similarities with Pinnotheres pisum , it also resembles Zaops ostreum (Say, 1817) from the Northwest Atlantic. Z. ostreum was redescribed by Stauber (1945) and especially its chela and the males’ first gonopods look very similar to P. pectunculi , but it can still be separated by the relative length of the dactyli of the walking legs and by differences in the existence of dorsal and lateral spines of the larvae. The larvae of Z. ostreum were described by Sandoz and Hopkins (1947).

Figures

Figure 5. Female of Pinnotheres pisum. (A) Dorsal view on female; (B) left cheliped with comb of setae; (C) exterior of left maxilliped.

Figure 6. Pinnotheres pectunculi from the dog cockle Glycymeris glycymeris. (A) Left chliped of female. Arrow points on small triangular tooth on the fixed finger; (B) pleon of male; (C) ventral view on left male first gonopod; (D) dorsal view on left male first gonopod.