Crinoniscus politosummus, Hosie, Andrew M., 2008

Hosie, Andrew M., 2008, Four new species and a new record of Cryptoniscoidea (Crustacea: Isopoda: Hemioniscidae and Crinoniscidae) parasitising stalked barnacles from New Zealand, Zootaxa 1795, pp. 1-28 : 9-13

Crinoniscus politosummus sp. nov.

( Figs 1 A, 5–7)

Material examined: Holotype: 1ɗ 1.18 mm ( NIWA 35052) Stn P946, Monowai Seamount, 25°59.10'S, 179°18.10'W, 1 Jun 1980, 660 m, from Glyptelasma gigas , coll R.V. Tangaroa .

Paratypes: 3ɗ on SEM stub ( NIWA 43479), 2Ψ on SEM stub ( NIWA 43480) from type locality. 1ɗ 1.06 mm ( NIWA 35065), 6ɗ ( NIWA 35067), 1Ψ ( NIWA 35068), 2ɗ ( NIWA 35069), 2ɗ 1.23–1.26 mm ( NIWA 35070), 5ɗ ( NIWA 35072) 1Ψ ( NIWA 43388), stn KOK0506/27, 30 Apr 2005, Rumble V Seamount, 36°8.34'S, 178°11.59'E, 433 m, from Poecilasma kaempferi , coll. R.V. Kaimikai-o-Kanaloa. 2ɗ 0.98–1.07 mm ( NIWA 35066), stn KAH0204/15, 15 Apr 2002, Cavalli Seamount, 34°5.98'S, 174°6.83'E, 480 m, from Glyptelasma gracile , coll. R.V. Kaharoa. 1ɗ 1.00 mm ( WAM C40021), stn TAN0616/6, 4 Nov 2006, in the vicinity of a cold seep on a topographic feature known as the “Rock Garden”, Hikurangi margin, 40°2.31’S, 178°8.58’E, 730 m, from Poecilasma kaempferi , coll. R.V. Tangaroa .

Diagnosis: Male: Body dorsoventrally flattened, widest at pereonite 5, cuticular striations indistinct dorsally, prominent near lateral margins of tergites. Anterior margin of cephalon evenly rounded with distinct rim. Eyes distinct. Antennule with few indistinct cuticular striations. Article 1 with convex mesial margin and lateral margin strongly concave, overlapping some of article 2, forming rounded anterolateral angle. Rami of article 3 both with 3 terminal setae. Antenna extends to pereonite 5 or 6 (setae excluded). Coxal plates with a posteriorly produced acute point with comb of fine setae near tips. Pereopods 3–5 with multifurcate robust seta in notch on propodus distal margin, dactylus 0.50–0.65 propodus length. Pereopods 6 and 7 propodus with rounded apex, lacking multifurcate seta, dactylus slightly shorter than propodus. Pleotelson forms narrow bell-curve shaped lobe. Uropod exopod approximately 0.45 length and width of endopod. Uropod exopod with 4 terminal setae, endopod with dense tuft of short fine setae.

Mature female: Crinoniscid females with globular body bearing 3 lobes projecting ventrally, anal lobe longest. Cephalic region lost—no eyes, mouthparts or antennae. Zigzagged ventral seam runs from between bases of anterior lobes to base of anal lobe.

Description: Male (holotype): Body tear-drop shaped. Length 1.18 mm widest at pereonite 5, 0.45 mm, cephalon 0.34 mm width 0.15 mm. Tergites with distinct cuticular striations near lateral margins, becoming smooth dorsally.

Eyes ovate, lateral near junction with pereonite 1, lens tinted with pinkish pigment.

Antennule article 1 with few indistinct striations, posterior margin entire, anterolateral angle rounded, 3 setae near both posterior and anterior margins, lateral margin strongly concave, overlapping some of second article, mesial margin slightly convex. Article 2 lateral margin with 6 setae, cuticular striations more pronounced than article 1. Article 3 with bundle of aesthetascs dorsal to uniarticulate rami with 1 seta near base of rami. Rami both with 3 terminal setae, posterior ramus slightly longer than anterior ramus, with 2 aesthetascs near midpoint.

Antenna reaching pereonite 6, peduncular articles with cuticular striations. Setal formula showing minor variations, 0-1-3-5-2-1-2-1-3 (left), 0-1-3-5-2-0-2-1-2 (right) (holotype). Articles, except basis, cylindrical, flagellar articles of similar width and length, approximately half as wide as terminal peduncular segment.

Pereopods 1 and 2 dactylus short, aquiline, approximately 0.3 length of propodus, terminus slots between two multifid spines on propodus. Propodus egg-shaped, two setae near base of dactylus. Carpus triangular, tuft of setae at distal angle. Merus subtriangular, long subterminal seta originating from groove on inner face, single shorter seta present medially. All articles with cuticular striations, propodus with ctenae.

Pereopods 3–5 ambulatory, dactylus elongate, 0.58–0.65 length of propodus, distally curved into terminal hook. Propodus distally quadrate, flattened, stout multifid seta in notch on distal margin, ventral margin slightly concave with 1 stout medial seta. Carpus and merus as in pereopods 1 and 2. Ischium with broad notch receiving merus and carpus. Cuticular striations as in pereopods 1 and 2 except dactylus without striations.

Pereopods 6 and 7 with more slender articles than preceding pereopods, dactylus 0.75–0.8 and 0.90–0.95 propodus length in pereopod 6 and 7 respectively, terminus not as recurved as in pereopods 3–5. Propodus semicylindrical, narrower and slightly shorter than that of pereopods 3–5, tapering distally with rounded apex lacking multifid seta. Ventral margin with 1 stout seta at the mid point followed by ventral comb of fine setae, bordered distally by single shorter sharp seta. Carpus, merus, ischium and cuticular striations as in pereopods 3–5.

Coxal plates entire, pointed with distinct cuticular striations and a lateral comb of small setae.

Pleopods becoming progressively smaller posteriorly. Pleopods 1–5 basis with 2 flattened, mesially directed trifurcate setae; distal margin forming submedial lobe covering base of exopod. Exopod with 5 sparsely plumose setae; lateral seta approximately one-third length of others, exopod quadrate distally, tapering in basal half. Endopods with 5 (3 in pleopod 5) sparsely plumose setae, quadrate distal margin, ovate basally and internal cuticular ring occupying basal two-thirds. All articles with prominent cuticular striations and ctenae, often overrunning margins.

Ventral abdominal lobe between first pair of pleopods rounded, with medial notch.

Pleotelson longer than wide, posterior margin entire, pronounced into narrow bell-curve shaped lobe. Basis of uropods quadrate with 2 setae at posterolateral angle. Exopod cylindrical, 0.40–0.45 as long and 0.40–0.45 as wide as endopods, with 4 terminal setae. Endopod triangular dorsoventrally flattened with tuft of 6 short setae basally on dorsal surface, mesial margin with profuse comb of fine setae and a tuft of numerous fine terminal setae.

Mature female 1.9 mm long 1.5 mm wide, body globular, dorsally inflated, tri-lobed, 2 anterior lobes of equal size, anal lobe longest slightly annulated. Anterior lobes located either side of zigzagged seam running along ventral surface to the base of anal lobe. Cephalic region indeterminable, no apparent mouthparts or antennae.

Immature female thoracic segments fused and becoming globose medially. Pereopod 2 with dactylus and propodus same as in males, but carpus, merus and ischium fused and extremely elongate forming ‘guy-lines’ up to as long as body. All other limbs absent. Eyes absent, pigment spots in ocular position, first and second antennae uniarticulate. Mandibles multifid.

Hosts: Poecilasma kaempferi ( Darwin, 1851) , Glyptelasma hamatum ( Calman, 1919) , G. gigas ( Annandale, 1916) and G. gracile ( Pilsbry, 1907) , are all from moderately deep waters (> 100 m). P. kaempferi is epibiotic on decapod crustaceans while the members of Glyptelasma attach to various biotic substrates, including Crustacea and corals.

Remarks: Crinoniscus politosummus has a close affinity to C. equitans . The anterior margin of antennule article 1 forms an anteriorly directed tooth ( Bocquet-Vedrine, 1985; Nielsen & Strömberg, 1973a) which is absent in the males of C. politosummus . Also there are some subtle differences in the construction of pereopods 3–7; the medial seta on the propodus is longer than those of C. politosummus and the terminal seta is not multifid. The posterior lobe on the pleotelson in C. equitans is not as pronounced. The females however are a fusiform, four-lobed (one cephalic, two lateral and one anal) “fleur de lis”, from which the genus gets its name, and are easily distinguishable from the globose three-lobed female of C. politosummus . The present species is distinguishable from C. cephalatus by the absence of the projecting posterior ‘wings’ on the cephalon, there is a lesser degree of tapering in the posterior segments and the relative positioning of the seta on pereopod 6 and 7 does not change. The females while both having a pair of anterior lobes, they are not homologous, as the lobes in C. cephalatus are likely to be the antennae.

Females, while less common than males, were not rare. Sometimes two or three mature females could be present in the single host, with accessory immature females present in addition to up to seven males. The males were typically found clustered together near the base of the capitulum on the inside of the mantle membrane, often attached where the host was brooding eggs. Mature females were placed underneath the prosoma of the host with their lobes acting to keep the female in place.

Etymology: From Latin polio meaning polished and summum meaning summit, named in reference to the lack of cuticular sculpting on the top of the tergites. Gender is masculine.

Figures

FIGURE 1. Map of New Zealand showing localities of where the current specimens of A, Crinoniscus cephalatus sp. nov. (Ο), C. politosummus sp. nov. (Π); B, Scalpelloniscus nieli sp. nov. (Ο), S. cf. penicillatus Grygier, 1981 b () and S. vomicus sp. nov. (Π) were collected.