Bopyrissa xiphidiostega, Williams & Boyko & Madad, 2019

Williams, Jason D., Boyko, Christopher B. & Madad, Asma Z., 2019, Branchial parasitic isopods (Crustacea: Isopoda: Bopyridae: Pseudioninae) of hermit crabs (Crustacea: Decapoda: Diogenidae) from the western Pacific, with descriptions of a new genus and three new species, Raffles Bulletin of Zoology 67, pp. 83-118 : 104-108

Bopyrissa xiphidiostega , new species

(Figs. 13–15)

Bopyrissa sp. A Madad, 2008: 2 , 4, 5, 28–33, 47, 49, 60, 61, 84, 85, fig. 8, table 1 [ Philippines, infesting Cacinus gaimardii (H. Milne Edwards, 1848) , C. minutus Buitendijk, 1937 , Dardanus lagopodes (Forskål, 1775) ].

Bopyrissa sp. Williams & Boyko, 2016: 35 , 57 [Batangas, Philippines, infesting C. minutus ].

Material examined. Philippines: Mature sinistral holotype ♀ (9.3 mm) ( USNM 1493986), mature allotype ♂ (1.8 mm) ( USNM 1493987) from left branchial chamber of ♀ Dardanus lagopodes (6.8 mm SL), Cebu, Olango Island, coll. JDW, 9 July 1997; Paratypes: 1 sinistral ♀ (6.2 mm), 1 ♂ (1.7 mm; male lost) ( USNM 1493988) from left branchial chamber of ♂ D. lagopodes (4.4 mm SL), Cebu, Danao Beach, coll. P. Cassidy, September 1996; 1 dextral ♀ (6.6 mm), 1 ♂ (2.0 mm) ( USNM 1493989) from right branchial chamber of ♀ D. lagopodes (4.0 mm SL), Cebu, Danao Beach, coll. P. Cassidy, September 1996; 1 sinistral ♀ (5.50 mm) ( USNM 1493990) from left branchial chamber of ♂ D. lagopodes (3.50 mm SL), Cebu, Danao Beach, coll. P. Cassidy, September 1996; 1 sinistral ♀ (4.8 mm) ( USNM 1493991) from left branchial chamber of ♂ D. lagopodes (3.00 mm SL), Cebu, Danao Beach, coll. P. Cassidy, September 1996; 1 sinistral ovigerous ♀ (5.8 mm), 1 ♂ (1.8 mm) ( USNM 1493992) from left branchial chamber of ♂ D. lagopodes (3.8 mm SL) host also infested with Asymmetrione harmoniae , new species ( USNM 1493915), Cebu, Danao Beach, coll. P. Cassidy, 6 December 1996; 1 sinistral ovigerous ♀ (4.6 mm), 1 ♂ (1.2 mm) ( USNM 1493993) from left branchial chamber of ♀ D. lagopodes (3.3 mm SL), Cebu, Olango Island, coll. JDW, 10 July 1997; 1 sinistral ♀ (4. 7 mm), 1 unidentified elongate epicaridean cryptoniscus larva (0.9 mm) ( USNM 1493994) from left branchial chamber of ♂ Calcinus gaimardii (3.3 mm SL), Puerto Galera, Big Lalaguna Beach, coll. JDW, 31 July 1997; 1 sinistral ovigerous ♀ (5.0 mm), 1 ♂ (1.4 mm) ( USNM 1493995) from left branchial chamber of ♀ C. gaimardii (3.2 mm SL), Puerto Galera, Coco Beach, coll. JDW, 12-15 January 1999; 1 sinistral ♀ (3.5 mm), 1 ♂ (1.0 mm) ( USNM 1493996) from left branchial chamber of ♀ Calcinus minutus (3.0 mm SL), Puerto Galera, Coco Beach, coll. JDW, 12-15 January 1999; 1 sinistral ovigerous ♀ (4.1 mm), 1 ♂ (1.0 mm) ( USNM 1493997) from left branchial chamber of intersex C. minutus (3.6 mm SL), host also infested with Parathelges aniculi ( Whitelegge, 1897) ( USNM 1283393; see Williams & Boyko 2016 ), Batangas, Anilao, coll. JDW, 13 February 1999; 1 sinistral ovigerous ♀ (4.7 mm), 1 ♂ (1.1 mm) ( USNM 1493998) from left branchial chamber of ♀ C. gaimardii (2.6 mm SL), Bataan, Mabayo, coll. JDW, 21 February 1999; 1 sinistral ovigerous ♀ (4.9 mm), 1 ♂ (1.6 mm) ( ZRC 2018.0831) from left branchial chamber of ♀ C. gaimardii (3.5 mm SL), Bataan, Mabayo, coll. JDW, 27 March 1999; 1 sinistral ♀ (3.7 mm), 2 cryptoniscus larvae of unidentified Cabirops sp. (1.0 mm, 0.9 mm) (JDW pers. coll.) from left branchial chamber of ♀ C. gaimardii (3.4 mm SL), Batangas, Sombrero Island, coll. JDW, 10 June 2000; 1 sinistral ♀ (3.6 mm), 1 ♂ (0.9 mm; JDW pers. coll.), 1 cryptoniscus larva of unidentified Cabirops sp. (0.9 mm) (JDW pers. coll.) from left branchial chamber of ♂ C. gaimardii (2.6 mm SL), Batangas, Sombrero Island, coll. JDW, 10 June 2000; 1 sinistral ovigerous ♀ (4.0 mm), 1 ♂ (1.1 mm) ( ZRC 2018.0833) from left branchial chamber of ♂ C. gaimardii (damaged, not measured), Batangas, Sombrero Island, coll. JDW, 10 June 2000; 1 sinistral ovigerous ♀ (4.7 mm), 1 ♂ (1.3 mm) ( ZRC 2018.0835) from left branchial chamber of ♀ C. minutus (3.6 mm SL), Batangas, Sombrero Island, coll. JDW, 10 June 2000; 1 sinistral ovigerous ♀ (4.3 mm), 1 ♂ (1.1 mm) ( ZRC 2018.0837) from left branchial chamber of ♀ C. gaimardii (3.2 mm SL), Puerto Galera, Lalaguna Beach, coll. JDW, 18 June 2000.

Description. Female body length 9.38 mm, maximal width 5.31 mm, head length 1.54 mm, head width 2.08 mm, pleon length 3.23 mm. Head sinistrally deflexed with ~68° distortion angle. Body pyriform, all body regions and segments distinct (Fig. 13A, B).

Head small, suboval, deeply set into pereon; frontal lamina broad, flared on lateral margins (Fig. 13A); eyes absent. Antennules of 3 articles each; basal articles appear fused, all articles covered with scales, terminal article distally setose (Fig. 13C). Antennae of 2 articles each, basal article broad, terminal article triangular, distally setose (Fig. 13C). Anterior lobe of maxilliped rounded, palp absent, spur of posterior lobe subacute (Fig. 13F). Barbula with 2 lateral projections, medial projection short (Fig. 13D). Tuberculate oostegites completely enclosing brood chamber, small round tubercles most prominent on lateral edges of oostegites, setae on posterior margin of fifth oostegite (Fig. 13B). Anterior lobe of oostegite 1 oval with lateral extension that overlaps with basis of pereopod 1 (Fig. 13G), posterior lobe triangular, curved, extending to a narrow tip; digitation on inner ridge (Fig. 13H).

Pereon of 7 distinct pereomeres, broadest across pereomere 3, tapering posteriorly; pereomeres 4–6 concave on long side (when viewed laterally) (Fig. 13A). Prominent dorsolateral bosses and reduced tergal projections on pereomeres 1–4 of concave side (Fig. 13A). Tergal projections almost as broad as dorsolateral bosses on convex side of pereomeres 1–4; pereomeres 5–7 with dorsolateral bosses continuing to midline of each segment on concave side, tergal projections absent. Pereomere 7 narrow, V-shaped and more similar to pleomere 1 than pereomere 6 (Fig. 13A). Pereopods 1–5 subequal in size, no large gap between pereopods, pereopods 6 and 7 slightly smaller (Fig. 13E, I).

Pleon V-shaped, of 6 distinct pleomeres, sixth pleomere not visible in dorsal view, pleomeres 1–5 with lateral plates, pleomere 1 deeply set into pereomere 7. Five pairs of biramous, tuberculate pleopods (Fig. 13B); small pair of distally rounded, uniramous uropods present on pleomere 6, uropods barely visible in dorsal view (Fig. 13A).

Male length 2.02 mm, maximal width 0.84 mm at pereomere 4, head length 0.21 mm, head width 0.44 mm, pleon length 0.5 mm. Head suboval, all segments distinct (Fig. 14A, B); eyes absent. Antennules of 2 articles each, setae on distal tip of article 2; antennae of 2 articles each, tuft of setae on distal tip of antennae and along ventral surface, scales on surface (Fig. 14C). Pereon of 7 distinct pereomeres, broadest at pereomere 5, tapering posteriorly (Fig. 14A). Pereopods with all articles distinct, carpus with terminal group of setae (Fig. 14D); pereopods 3 and 4 largest, size decreasing posteriorly and anteriorly with pereopods 6 and 7 smallest (Fig. 14D).

Pleon of 6 distinct pleomeres, tapering posteriorly. Midventral tubercles absent; dorsolateral pleopods present as low swellings on pleomeres 1–5 (Fig. 14B). Pleotelson rounded, no posterolateral projections present; anal fissure prominent medially, distolateral edges with setae; no uropods (Fig. 14E).

Type locality. Olango Island , Cebu, Philippines .

Etymology. The specific epithet xiphidiostega is derived from the Greek words xifidio (στιλέτο; small sword) and stegi (στέγη; cover), referring to the anterior lobe of oostegite 1

which has a dagger-like lateral extension that overlaps with the basis of pereopod 1.

Distribution. Cebu, Bataan, Puerto Galera, Batangas.

Hosts. Diogenidae : Cacinus gaimardii (H. Milne Edwards, 1848) , C. minutus Buitendijk, 1937 , and Dardanus lagopodes (Forskål, 1775) .

Size range (length). Females to 9.3 mm, males to 1.8 mm.

Remarks. Markham (1978) reported that most species of Bopyrissa occur only in dextral or sinistral forms but not both, although noting that both forms have been recorded in Bopyrissa diogeni with the dextral morph predominating. Bopyrissa xiphidiostega , new species is unusual in that females are predominantly sinistral, although a single dextral example was found. Bopyrissa dawydoffi ( Codreanu & Codreanu, 1963) is currently the only described species in the genus that is apparently exclusively sinistral but its generic placement is uncertain.

Females of B. pyriforma as described by Shiino (1958) have inconspicuous dorsolateral bosses present on pereomeres 1–4, relatively large heads deeply set into pereomere 1 that lack a pronounced frontal lamina and the uropods are completely concealed by the fifth lateral plates in dorsal view. Females of Bopyrissa xiphidiostega , new species have more prominent dorsolateral bosses on pereomeres 1–4 and a relatively smaller head with a well-defined frontal lamina, although B. xiphidiostega , new species does have reduced uropods, they are not completely concealed by the fifth pleonal plate as in B. pyriforma . The article counts of the antennules and antennae of females of B. liberorum (five and three, respectively) also differ from those of B. xiphidiostega , new species (three and two, respectively). Additionally, whereas B. xiphidiostega , new species lacks a maxilliped palp, females of B. liberorum have a maxilliped with a small setose palp. Bopyrissa xiphidiostega , new species is similar to B. diogeni in that females of both species possess a pronounced frontal lamina and a lateral projection on the anterior lobe of oostegite 1; however, females of B. diogeni have antennules of three articles each and antennae of one article each, a barbula with one lateral projection (two in B. xiphidiostega , new species), a smooth inner ridge on oostegite 1 (digitate in B. xiphidiostega , new species) and the projection on the anterior lobe of oostegite 1 is considerably broader and less tapered in B. diogeni than in B. xiphidiostega , new species.

Males of B. diogeni have antennules and antennae of three articles each, whereas those of B. xiphidiostega , new species, have two and three articles each, respectively. Males of B. pyriforma have broad, flattened pleopods; however, the pleopods seen in B. xiphidiostega , new species are more medially located and not as broad. The pleotelson of B. pyriforma has slight posterolateral projections, while those of B. diogeni are much larger; there are no such posterolateral projections on the telson in males of B. xiphidiostega , new species.

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Ecology. Prevalence of Bopyrissa xiphidiostega , new species over the eight collections of hermit crabs in which the parasite was found ranged from 0.5–7.7% (mean prevalence=2.06 ± 2.52 %, n=1,077 total hermits examined). Bopyrissa xiphidiostega , new species parasitised three host species: Calcinus gaimardii , C. minutus , and Dardanus lagopodes in the Philippines ( Table 1). One of the D. lagopodes was doubly infested with B. xiphidiostega , new species (in the left brachial chamber) and Asymmetrione harmoniae , new species (in the right brachial chamber). One of the C. minutus was doubly infested with B. xiphidiostega , new species and the abdominal parasitic isopod Parathelges aniculi ( Whitelegge, 1897) (USNM 1283393; see Williams & Boyko, 2016 ). Two of eighteen (11.1%) female B. xiphidiostega , new species were found with cryptoniscus larvae of an unidentified cabiropid species and one female B. xiphidiostega , new species was found with an unidentified, epicaridean cryptoniscus larva. Extensions on the cuticle that we interpret as thalli of an unidentified protistan belonging to Mesomycetozoa were found on some pereomeres of males (Fig. 14A) [similar to those reported in Williams & Madad (2010)].

The mean total body length of female B. xiphidiostega , new species was 5.0 ± 1.4 (n=18); male B. xiphidiostega , new species mean total body length was 1.3 ± 0.4 (n=15). The relationship between female total body length and male total body length was significantly positively correlated (P<0.0004) (Fig. 15A). Bopyrissa xiphidiostega , new species was found to be ovigerous in all months sampled (December through March, June, July, and August) and thus likely breeds throughout the year. Of the 19 mature female B. xiphidiostega , new species collected, 56% were ovigerous; the smallest ovigerous female was 4.0 mm. The total body length of female B. xiphidiostega , new species and host hermit crabs (as estimated by carapace length) was significantly positively correlated (P<0.0001) (Fig. 15B).

Variation. Female specimens conform to the typical Bopyrissa morphology, with the characteristic S-shaped body and five pairs of biramous pleopods and uniramous uropods; all but one individual of Bopyrissa xiphidiostega , new species were sinistrally distorted. Female specimens exhibited varying degrees of digitation of the inner ridge of oostegite 1, with some specimens showing pronounced digitation across the entire inner ridge whereas others showed weak digitation towards the base of oostegite 1 or no digitation at all. All female specimens had a simple, digitiform barbula varying in length, although one had several short medial protuberances. Both the pleopods and oostegites of female specimens showed tuberculation, although the tubercles were reduced in some specimens.