Paguritherium alatum Reinhard, 1945

Detorre, Marissa, Williams, Jason D. & Boyko, Christopher B., 2023, A review of the endoparasitic isopods (Epicaridea: Entoniscidae) from hermit crabs, including description of the new subfamily Diogenioninae and a new species of Paguritherium Reinhard, 1945 from the Philippines, Zootaxa 5249 (1), pp. 12-40 : 21-23

Paguritherium alatum Reinhard, 1945

Figure 6

Paguritherium alatum Reinhard, 1945: 198–203 , figs. 1–6 (Woods Hole, Massachusetts, infesting Pagurus longicarpus ); Reinhard & Buckeridge 1950: 131–137 (Woods Hole, Massachusetts, infesting P. longicarpus ; effects on secondary sex characters of host); Reinhard 1956: 89–90 (mention); Noble & Noble 1961: 581 (mention); Williams 1965: 127 (mention); Hartnoll 1966: 45 (list); Danforth 1970: 35, 36 (mention), 52 (list), 133–135 (description after Reinhard 1945), fig. 48a, b (after Reinhard 1945); Kuris 1971: 304, 314 (mention); Noble & Noble 1971: 474 (mention); Pflugfelder 1977: 274 (mention); Adkison & Heard 1978: 409 (Beaufort, North Carolina, infesting Pagurus annulipes and P. longicarpus ); Overstreet 1983: 225 (mention); Williams 1984: 218 (mention); Schuldt & Rodrigues Capítulo, 1985: 142 (mention); Sparks 1985: 401 (mention), fig. 29 (after Reinhard 1945); Ruppert & Fox 1988: 402 (list); Adkison 1990: 10, 39, 40, 53 (mention), 73–81, figs. 9–10 (redescription) (Woods Hole, Massachusetts, infesting P. longicarpus ); Meyers 1990: 375 (mention); Humphrey 1995: 231, 14–1, 14–10 (list); McDermott 1998: 1042–1044 (New Jersey, infesting P. longicarpus ); Torres Jordá 2003: 37, 39 (mention); McLaughlin et al. 2005: 189 (list); McGuire 2007: 54 (mention); Madad 2008: 12 (mention); McDermott et al. 2010: 12 (list), 28, 33 (mention), fig. 13d–g (after Reinhard 1945); Williams & Boyko 2012: fig. 3K, L (after Reinhard 1945); McDermott et al. 2019: 110–111 (mention); McDermott et al. 2022: 7–8 (mention); DeTorre 2022: 4, 8, 9, 19–21, 23, 24, figs. 2B (after Reinhard 1945), 12 (map).

Paguritherium altum [sic] Schultz 1969: 346, fig. 559 (after Reinhard 1945).

Material examined: United States: Ovigerous female (8.5 mm), mature male (0.9 mm) ( USNM 1522335 ), infesting male Pagurus longicarpus (2.7 mm) inhabiting unknown shell, inside Hereford Inlet on the Cape May peninsula of New Jersey, 39°02′ N, 74°48′ W, coll. J.J. McDermott, 10 July 1985 . Ovigerous female (5.6 mm) ( USNM 1522336 ), infesting female P. longicarpus (2.5 mm) inhabiting unknown shell, inside Hereford Inlet on the Cape May peninsula of New Jersey, 39°02′ N, 74°48′ W, coll. J.J. McDermott, 18 June 1986 . Ovigerous female (9.5 mm) with eggs and few epicaridium larvae on SEM stub ( USNM 1522337 ), infesting female P. longicarpus (2.6 mm) inhabiting unknown shell, inside Hereford Inlet on the Cape May peninsula of New Jersey, 39°02′ N, 74°48′ W, coll. J.J. McDermott, 12 August 1987 . Epicaridium larva (304 µm; JDW pers. coll. 9-12-17), infesting Acartia hudsonica Pinhey, 1926 (1.3 mm), taken in plankton tow at town of Hempstead East Marina, Point Lookout , New York. 40°35′37.70″ N, 73°35′6.39″ W, coll. J.D. Williams, 12 September 2017 .

Brief remarks on male morphology (USNM 1522336): The males (fig. 6E–H) have six unsegmented pereopods, reduced to rounded knob-like structures, covered in spinous scales (fig. 6E, G, H). The “spines” reported by Reinhard (1945; fig. 6F herein) are actually scales as are found in a wide range of epicarideans (e.g., Nielsen & Strömberg 1969; Cericola & Williams 2015). Pereopod 7 is very reduced, with only a minute, scale-covered lobe present as shown with SEM (fig. 6G).

Brief remarks on epicaridium larval morphology (USNM 1522337): Adkison (1990) was the first to report on the morphology of the epicaridium larvae of P. alatum (see fig. 6I–N), showing that they have: antennulae of three segments; antennae of six segments; pereopods 1–5 gnathopodal, without specialized fan-like setae; pereopod 6 with a reduced triangular dactylus; pleopod 5 setae absent, exopod reduced; and uropods biramous with the exopod longer than the endopod. Adkison (1990) mislabeled pereopod 6 as pereopod 7 for the epicaridium larvae of this species in his figure 10 (fig. 10h should be labeled as pereopod 6; fig. 10F and G are more anterior pereopods, but it cannot be determined which ones; these are reproduced and labeled as such herein fig. 6K–M). Aside from this error, the morphology of the epicaridium larvae described by Adkison (1990) is confirmed based on the new material herein studied, including the lack of specialized fan-like setae on pereopods 1–5 and pereopod 6 with a reduced triangular dactylus (fig. 6N).

Remarks: The adult specimens of P. alatum examined here were those reported in McDermott (1998) from New Jersey where he found four out of 3,703 (0.11%) P. longicarpus infested. The female specimens match the original description (fig. 6) and the redescription of the species in Adkison′s (1990) unpublished dissertation which was based on the syntypes (USNM 81563) and four additional specimens (USNM 235935). McDermott (1998) found that the pleon of females extended to an opening toward the base of the eyestalks. Adkison (1990) indicated that in at least one specimen the pleon extended to an opening toward the base of the maxilliped.

During sampling of plankton on Long Island, New York, one copepod ( Acartia hudsonica ) was found with an epicaridium larva attached that matched in all aspects the morphology indicated above for P. alatum . This is the first confirmed identification of any entoniscid from a copepod intermediate host in nature (see notes in Discussion on experimental settlement of entoniscid epicaridium larvae on copepods).

Figures

FIGURE 6. Paguritherium alatum Reinhard 1945, female (A–D). A. Cross section of hermit crab Pagurus longicarpus showing position of ovigerous female P. alatum within abdomen; body of parasite shown in black, oostegites with developing larvae shown by black dots; the pleon extends to an opening at the base of the eyestalk (arrow). B. Adult female removed from abdomen of host (enclosing sheath and contents of brood pouch removed). C. Ovigerous female with embryos present in brood pouch. D. Head of female. Male (E–H = USNM 1522336). E. Lateral view of male. F. Head of male, ventral view. G. Ventral view of male. H. Male right pereopods 5–7. Epicaridium larva (I–O; N = USNM 1522337). I. Antennule. J. Antenna. K. Pereopod 4 (could be any of 1–5, see Remarks under P. alatum). L. Pereopod 5 (could be any of 1–5, see Remarks under P. alatum). M. Pereopod 6. N. Pereopods 5 (on right) and 6 (on left). O. Pleopod 5. Abbreviations:A1, antennulae; A2, antennae; Hd, head; He, heart; Md, mandibles; Mx, maxillae, Mxp, maxillipeds; O1–O4, oostegites 1–4; P1, pereopod 1. Scale bars: G = 200 µm; H = 25 µm; N = 10 µm; rest not to scale. A–F modified from Reinhard (1945); J–M, O modified from Adkison (1990).