Scalpelloniscus vomicus Hosie, 2008, sp. nov.
Creators: name: Hosie, Andrew M.
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Hemioniscidae
Scalpelloniscus
Scalpelloniscus vomicus

description: Scalpelloniscus vomicus sp. nov.
(Figs 1 B, 10, 11, 12)
Material examined: Holotype: 1ɗ 1.92 mm (NIWA 35063), stn TAN0308/142, 2 Jun 2003, West Norfolk Ridge, 34°16.49'S, 168°24.08'E, 1249 m, from Heteralepas japonica, coll. R.V. Tangaroa.
Paratypes: 1ɗ (NIWA 35062), 2ɗ, 2Ψ (WAM C40022), stn I34, 7 /05/1975, 35°0.00'S, 175°13.00'E, 575 m, from Paralepas minuta, coll. R.V. Tangaroa. 1Ψ (NIWA 35033), 2ɗ 1.66–2.02 mm (NIWA 35054), 1Ψ (NIWA 35055), 1ɗ (NIWA 35057), 1ɗ 1.59 mm (NIWA 35061), stn KAH0204/27, 16 Apr 2002, Cavalli Seamount, East of North Cape, 34°7.21'S, 174°5.64'E, 554 m, from Paralepas minuta, coll. R.V. Kaharoa. 1ɗ 2.02 mm (NIWA 35071), stn KAH0204/27, 16 Apr 2002, Cavalli Seamount, East of North Cape, 34°7.21'S, 174°5.64'E, 554 m, from Megalasma striatum, coll. R.V. Kaharoa. 2ɗ (NIWA 35021), 1ɗ (NIWA 35035), same locality as holotype. 2Ψ (NIWA 35046), 2ɗ on SEM stub (NIWA 43476), 2Ψ on SEM stub (NIWA 43481), 6 epicaridium larvae (NIWA 35053) taken from female on SEM stub (NIWA 43481), stn Z8482, 28 Apr 1996, Bay of Plenty, 35°58.00'S, 176°49.00'E, 750 m, from Smilium zancleanum, coll. F/V Peterson. 1ɗ (NIWA 35036), stn Z8883, 6 Aug 1997, Bay of Plenty, 37°25.40'S, 176°53.00'E, 464 m, from Heteralepas japonica, coll. F/V Margaret Philippa. 1ɗ (NIWA 35058), Z9786, 29 Jun 1999, North of Chatham Islands, 42°43.11'S, 179°52.78'W, 1115 m, from Smilium zancleanum, coll. F/V Amaltal Explorer.
Diagnosis: Male body dorsoventrally flattened, broadest at pereonite 5. Cephalon anterior margin of evenly rounded without rim. Antennule article 1 with 9 posterior teeth, lateral most tooth very narrow, abutting onto second tooth, anterolateral angle acute. Article 2 cuticular striations giving the appearance of toothlike scales on ventral surface. Pereopods 3–5 dactylus 0.65–0.70 propodus length, propodus with stout seta in notch on distal margin. Pereopods 6 and 7 dactylus 0.85–0.90 propodus length, propodus tapered distally. Coxal plate tooth formula 6-5-5-5-5-5-5 or 4. Pleotelson as wide as long, posterior lobe taking up approximately 0.60 of posterior margin. Exopod 0.75–0.80 length and 0.45–0.50 width of endopod, with 3 terminal setae, dense tuft of terminal setae on endopod.
Mature female body, except egg sac, as in males. Egg sac kidney shaped formed ventrally from pereonite 3–7.
Description: Male (holotype) body tear-drop shaped, total length 1.92 mm maximum width 0.60 mm widest at pereonite 6, cephalon length 0.25 mm, width 0.45 mm. Cuticle dark orange, appears banded where tergites overlap.
Antennule article 1 with 9 posterior teeth, lateral most tooth, as wides as second tooth at base, acute, abuts onto second tooth (visible under light microscopy as a notch or shoulder on second tooth); others blunt or rounded and separated from each other. Anterior margin pronounced into laterally directed, acute point. Cuticular striations on article 2 forming tooth-like scales. Lateral margin lined with 6 setae. Third segment with bundle of aesthetascs dorsal to uniarticulate rami. Posterior rami longer than anterior rami, both with 3 terminal setae. Posterior ramus with 2 aesthetascs placed near mid point.
Antenna originating beneath teeth of first antenna, reaching pereonite four. Cuticular striations present on peduncle only. Setal formula not symmetrical 0-1-2-5-3-1-2-1-4 (left) 0-1-2-5-2-1-2-1-5 (right). Flagellar articles approximately half as wide as terminal peduncular article.
Pereopods 1 and 2 dactylus curved, with cuticular striations, not over extending propodal palms, approximately 0.5 length of propodus, terminus slots between two spines on propodus. Propodus globular with cuticular striations and ctenae. Carpus approximately triangular in lateral view with stout distal spine. Merus triangular with one setae distally.
Pereopods 3–5 becoming slender and more elongate posteriorly. Dactylus 0.65–0.70 as long as propodus, terminus recurved. Propodus quadrate, dorsoventrally flattened. Distal margin with one stout seta at base of notched lateral extension. One stout seta also present medially on propodus. Carpus triangular with stout spine on distolateral margin. Merus subtriangular with single seta originating from sub distal groove. Ischium with paired dorsal extensions forming groove where merus articulates.
Pereopods 6 and 7 dactylus 0.85-0.90 as long as propodus, terminus less recurved in pereopod seven. Propodus semicylindrical tapering distally. Ventral margin with setal comb and one stout seta approximately 0.66 from distal margin. Carpus and merus as in pereopods 3–5.
Coxal plates with rounded posteriorly directed teeth, width of teeth as little as 0.1 length. Striations extending only into median tooth. Formula 6-5-5-5-5-5-4 or 5.
Pleopods becoming progressively smaller posteriorly. Pleopods 1–5 basis with 2 long, flattened trifurcate setae, posterior margin extends into bi-lobed lamella covering bases of rami, mesial lobe much smaller than lateral lobe. 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 truncate with fringe of fine setules and medial notch.
Pleotelson as long as wide, posterior margin entire, forming bell-shaped lobe over basis of uropods, occupying approximately 0.60 of posterior margin. Basis with 2 setae at laterodistal angle, one shorter, one longer than exopod. Short spinule present at laterodistal and mediodistal angle. Exopod approximately 0.75–0.80 length and 0.45–0.50 width of endopod, with three terminal setae, 1 longer than and 2 half as long as endopod. Endopod triangular, dorsoventrally flattened, medial margin with comb of fine setules, approximately 6 short setae present on dorsal face near basis, terminally with dense tuft of fine setae.
Mature females divided into 2 distinct parts, dorsum and egg sac. Dorsum as in males. Egg sac derived ventrally pereonites 3–7, forcing pereopods laterally. Dorsum sits in groove which extends anteriorly to the ventral margin, giving the egg sac a kidney-shaped appearance, width approximately 3 mm. Forming externally visible gall in some hosts.
Epicaridium larva body composed of 14 segments, cephalon longest segment. Antennule comprises 3 peduncular articles, flagellum with two uniarticulate rami with two terminal setae. Antenna with 3-articled peduncle and 3-articled flagellum. Flagellar articles approximately half as wide as peduncular articles. Terminal article of peduncle with three setae. Terminal flagellar article with two short simple setae and two bipinnate setae, 1.5 and 0.75 body length.
Pereopods 1–6, becoming longer and more slender posteriorly. Carpus with serrated fan-like seta at apex; propodus with same near mid point.
Pleopods 1–5, comprising basis and uniarticulated exopod with 3 setae and endopod with two setae. Exopod and endopod of first pleopod of similar size and shape. Pleopods 2–5 endopod twice as wide as exopod basally, tapered abruptly distally.
Pleotelson posterior margin evenly rounded not forming lobe. Uropod basis triangular with 1 bipinnate seta as long as body and as wide as exopod, inserting at posterolateral angle. Exopod placed dorsally to and slightly shorter and thinner than endopod. Endopod and exopod with 2 long, oppositely bipinnate setae as long as lateral seta of basis. Anal tube as long as exopod.
Hosts: Heteralepas japonica (Aurivillius, 1892), Paralepas minuta (Philippi, 1836), Megalasma striatum (Hoek, 1883) and Smilium zancleanum (Seguenza, 1876).
Remarks: Male Scalpelloniscus vomicus can be distinguished from those of the holotype of S. penicillatus by the lack of cephalic posterolateral projections, differing coxal plate formula, relatively longer teeth, the shorter length of the dactylus relative to the propodus of pereopods 6 and 7. The allotype of S. penicillatus has a differing coxal plate formula with spatulate teeth, but is otherwise similar. Scalpelloniscus binoculis lacks teeth on the coxal plates, and the cephalon has projecting posterolateral angles reaching to pereonite 2 but is otherwise similar. The coxal plate formula is also different in S. nieli and pereopods 6 and 7 have a relatively short dactylus and the propodus is not as distally tapered as in S. vomicus. The mature females are readily distinguishable in that the egg sac in S. vomicus is derived from the ventral inflation of pereonites 3–7 as opposed to the fusion of the posterior segments.
The larval stage is a rare find, and larvae have not often been linked to the adults (see Bocquet-Vedrine 1987; Peresan & Roccatagliata 2005). The epicaridium stage in Crinoniscus equitans bears similar scaleshaped setae on the pereopods, but, there is a higher degree of elongation in the posterior pairs of pereopods, relatively shorter antennae and in general the setation is not as strong as in S. vomicus. The description of the epicaridium larvae of Liriopsis pygmaea (Rathke, 1843) by Peresan and Roccatagliata (2005) show some interesting differences to those of S. vomicus. In general appearance, the present specimens have much longer and heavier setae on the antenna, pleopods and uropods, the anal lobe is also much longer than in L. pygmaea. Another difference is that the L. pygmaea specimens bear the styliform dactylus on the last pair of pereopods which is characteristic of the adult males in the family.
Initially, the variation of the coxal plate dentition was interpreted as distinguishing two separate species, until an exceptional specimen with four teeth on the left and five on the right was found in the tissue of Paralepas minuta. Previously the specimens with five teeth had been found only in specimens of Smilium zancleanum and those with four only in the heteralepadids.
Unlike the above described species S. vomicus is an internal parasite, embedded in the muscular tissue of the peduncle or capitulum. Females were found only in the peduncle or at the base of the capitulum, near to the ovaries. A gall is formed by the female and is particularly evident in Smilium zancleanum, sometimes reaching 1 cm in diameter and can push the capitular plates out of alignment. In one sample of 17 S. zancleanum (NIWA 43461) 12 specimens had up to 4 visible galls on the peduncle or on the lower capitulum. Typically the host cuticle is perforated, possibly for the release of larvae and pheromones. Often the remains of the male dorsum is partially or wholly embedded in the cuticle, while the egg sac is enveloped in a host response membrane suggesting that the female burrows through the cuticle to gain access to the host. Males do not appear to use the perforation to gain access to the female, as they have been found on the internal side of the female. Presumably the males penetrate the host and then migrate to the nearest female.
Etymology: This species is named for the gall that the mature female forms on the peduncle of some hosts, from Latin vomicus meaning ulcer or boil, gender is masculine.
description: Published as part of Hosie, Andrew M., 2008, Four new species and a new record of Cryptoniscoidea (Crustacea: Isopoda: Hemioniscidae and Crinoniscidae) parasitising stalked barnacles from New Zealand, pp. 1-28 in Zootaxa 1795 on pages 20-24, DOI: 10.5281/zenodo.182627