Bopyrissa magellanica Nierstrasz & Brender

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 : 93-95

Bopyrissa magellanica Nierstrasz & Brender à Brandis, 1931

(Figs. 4, 5)

Bopyrissa magellanica Nierstrasz & Brender à Brandis, 1931: 175–179, figs. 26, 27 [ Costa Rica; infesting Clibanarius albidigitus Nobili, 1901 ]; Codreanu, 1961: 138; Danforth, 1963: 7 [list]; Danforth, 1970: 44 [list]; Bourdon, 1972: 835 [mention]; Markham, 1978: 103, 107; Markham, 1982: 333; Markham, 1992: 3 [table]; Markham, 2003: 72 [list]; Espinosa- Pérez & Hendrickx, 2006: 222 [table]; Ortiz & Lalana, 2006: 17 [list]; Brusca & Wehrtmann, 2009: 209 [list]; McDermott et al., 2010: 8 [table].

Bopyrella [sic] magellanica — Markham, 2003: 72 [list].

Material examined. Costa Rica: dextral ♀ lectotype (herein designated) (2.0 mm) ( NHMD 85028 ; jar in vial has typed note “ holotype?”) , 6 dextral ♀ paralectotypes (1.5–2.9 mm), 1 ♂ paralectotype (1.1 mm), 2 cryptoniscus larvae paralectotypes ( NHMD 300413 ), all from Clibanarius albidigitus Nobili, 1901 (sexes and sizes unknown), Punta Arenas, 23 August 1890 .

Description. Female (Fig. 4) body length 1.5–2.9 mm, head dextrally deflexed with ~45–60° distortion angle. Body slightly S-shaped, all body regions and segments distinct (Fig. 4A, B). Head suboval, deeply set into pereon; thin frontal lamina covered with scales (Fig. 4A; scales not drawn); eyes absent. Antennules and antennae of 3 articles each; terminal articles with setae at distal tips, scales covering surface (Fig. 4C). Maxilliped with acute spur; short, rounded non-articulated palp with few small setae present (Fig. 4H). Barbula with two projections on each side, one very small medial lobe and one larger digitiform lateral lobe (Fig. 4F). Oostegites completely enclosing brood chamber (Fig. 4B), setae on posterior margin of fifth oostegites; anterior lobe of oostegite 1 ovate, posterior lobe triangular, strongly recurved with few setae on distal tip; inner ridge of oostegite 1 with few low, rounded lobes covered with scales (Fig. 4G). Pereon of 7 distinct pereomeres, broadest across pereomeres 3 and 4, tapering towards pleon posteriorly. Dorsolateral bosses and coxal plates on segments 1–4, tergal projections approximately half length of dorsolateral bosses on segments 1–4; segments 5–7 with dorsolateral bosses continuing entire length of each segment, tergal projections absent (Fig. 4A). Pereopods 1–7 subequal in size, setae on anterior tip of carpus, scales on all pereopodal articles (Figs. 4C, I). Pleon of 5 distinct dorsally visible pleomeres, all pleonal segments with lateral plates, sixth pleomere present but not visible in dorsal view (Fig. 4A). Five pairs of biramous pleopods, first pair largest; first and second pairs flattened, ovate; third to fifth pairs elongate, digitiform; fifth pair smallest; pair of small, digitiform, uniramous uropods present on pleomere 5 (Fig. 4D, E).

Male (Fig. 5A–D) body length 1.1 mm, maximal width at pereomeres 3 and 4. Head suboval, distinct from pereomere 1, all segments distinct (Fig. 5A); eyes absent. Antennules and antennae of 3 articles each; terminal articles with setae at distal tips, scales covering surfaces (Fig. 5B). Anterior pereopods largest, size slightly decreasing posteriorly with pereopods 6 and 7 smallest, carpi with setae, scales on all pereopodal articles (Fig. 5B, C). Mid-ventral tubercle as low, rounded lobe between seventh pereopods (Fig. 5C). Pleon of 5 distinct pleomeres, tapering posteriorly (Fig. 5A); low, triangular mid-ventral tubercles present on all pleomeres (not visible at low power), minute on pleomeres 4 and 5. Pleopods semi-circular with rounded medial extension, extension prominent on pleopods 1–3, reduced on 4 and 5 (Fig. 5C, D). Pleotelson with anal fissure, produced distolaterally, distolateral ends with setae, uropods absent (Fig. 5D).

Cryptoniscus larva (Fig. 5E–H) length 0.6–1.2 mm, maximum width at pereomere 3; body tear-drop shaped (Fig. 5E). Head anterior margin concave, posterior margin sinusoidal, widest at posterolateral junction with pereomere 1 (Fig. 5E); eyes lacking. Antennules of three articles each (Fig. 5F), basal article approximately three times wider than long, distomedial region with tuft of setae, article 2 with rounded base and produced into digitiform extension that overlaps article 1, tufts of setae on base and extension, article 3 with small rounded base and digitiform extension, distal setae present (Fig. 5F). Antennae of eight articles each (four peduncular and four flagellar) (Fig. 5F), articles 1 and 2 triangular, articles 3 and 4 cylindrical, article 3 with long distal setae; flagellar articles subequal in length, much narrower than peduncular articles, second flagellar article with terminal setae (additional articles may have setae but are too closely applied to cuticle to be observable), distalmost article with tuft of terminal setae (Fig. 5F). Oral cone triangular, anteriorly directed (Figs. 5F). Pereomere 3 broadest, tapering posteriorly. Body pigmentation lacking. Pereomeres 1–7 with entire (not toothed) coxal plates. Pereopods 1–7 isomorphic, dactyli long and slightly curved, small notch or seta approximately half distance from base of dactylus, most prominent on posterior pereopods (Fig. 5F, H); each propodus with cuticular ridge corresponding to dactylus, lined with very short setae; each carpus with distal tuft of setae (Fig. 5F, H). Pleon with 5 pleopods. Pleotelson approximately three times wider than long, rounded laterally, with small rounded medial extension, long setae on either side of extension (Fig. 5G). Uropods biramous, composed of wide basal segment, short endopod, exopod approximately twice as long and wide as endopod, long distal setae on endopods and exopods (Fig. 5G).

Type locality and distribution. Punta Arenas , Costa Rica .

Host. Diogenidae : Clibanarius albidigitus Nobili, 1901 (Nierstrasz & Brender à Brandis, 1931). This host identification was also reported in McDermott et al. (2010) but the source of the host identification was not stated therein. Nierstrasz & Brender à Brandis (1931) gave the host identification only as “ Clibanarius sp. ”; however, the types of Stegias angusta Nierstrasz & Brender à Brandis (1931) were also collected in Punta Arenas at the same time as the types of B. magellanica and, in fact, there is a pair of B. magellanica in the jar with the types of S. angusta as well as a hermit crab, which is identifiable as C. albidigitus .

Size range (length). Females to 2.9 mm, males to 1.1 mm.

Remarks. Although Markham (1978) examined the type series and provided some notes, this is the first time the species has been fully redescribed. The original description by Nierstrasz & Brender à Brandis (1931) provided only dorsal views of a male and female and a lateral view of a female pleon, without designation of a holotype. The lateral view of the female pleon (Fig. 4D herein) was incorrectly labeled, presumably by Brender à Brandis, with pleomere 1 inexplicably labeled “VIII” (no isopod has either a pereomere or pleomere “8”) and pereopod 7 labeled as “PerVIII”; the drawing is reproduced herein (Fig. 4D) with corrected labeling. The original text stated that females had five pairs of biramous pleopods and no uropods. Examination of the type series shows that the species has five pairs of biramous pleopods as well as uniramous uropods. In some specimens, the fifth pair of pleopods are so small they are difficult to distinguish and most of the specimens have some damage to the pleopods, making counts difficult; this could have been the source of Nierstrasz & Brender à Brandis’s (1931) error. The female specimen with a typed note “ holotype?” in the vial is designated herein as the lectotype.

Markham (1978) stated that he examined all eight female specimens in the type series of B. magellanica (one female is currently missing from the vial) and compared their characters with those of B. wolffi Markham, 1978 ; he did not, however, provide a redescription of B. magellanica . He stated that the characters of Bopyrissa included: females with an S-shaped body, frontal laminae present but reduced, five pleomeres with four pairs of biramous pleopods and one pair of uniramous uropods. This is not correct because all species in Bopyrissa have six pleomeres, although the sixth pleomere is ventrally displaced and not visible in dorsal view. Specimens of B. diogeni ( Popov, 1929) have been described with four pairs of biramous pleopods and uniramous fifth pleopods ( Bourdon, 1968). However, we have seen specimens of B. wolffi from Belize that have five pairs of biramous pleopods plus uniramous uropods, so it is possible that there is intraspecific variation in pleopod counts. To our knowledge, this is the first description of a cryptoniscus larva for any species in the genus Bopyrissa . The larval morphology for B. magellanica is similar to that documented for other pseudionines (e.g., Bourdon, 1968; Anderson & Dale, 1981); however, whereas many of the previously described species have distinct teeth on the posterior margin of the pleotelson [= pygidium sensu Bourdon (1968)], B. magellanica lacks these teeth. Cryptoniscus larvae may provide many taxonomically informative features (see Boyko & Williams, 2015) but presently we lack descriptions of this stage in many epicaridean genera.