Jassa laurieae Conlan & Desiderato & Beermann 2021, n. sp.
Creators: name: Conlan, Kathleen E.
name: Desiderato, Andrea
name: Beermann, Jan
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ischyroceridae
Jassa
Jassa laurieae

description: Jassalaurieae n. sp.
(Table 11, Figs 54, 55)
Diagnosis.
Male:
Mandibular palp: article 2, dorsal margin without a fringe of setae.
Maxilla 1: without a seta or setal cluster at the base of the palp article 1.
Gnathopod 1: basis, anterolateral margin with a few minute setae along its length; carpus without a single or cluster of short setae at the anterodistal junction of the propodus.
Gnathopod 2: basis without a row of long setae along the anterolateral margin (setae minute, << basis width); carpus and propodus, setae on the anterior margin minute (setal length << basis width).
Pereopods 5–7: missing.
Uropods: missing.
Telson: missing.
Thumbed male:
Antenna 2: large individuals with plumose setae on the flagellum and peduncular article 5.
Gnathopod 2: propodus, palmar defining spines not produced on a ledge, absent in large thumbed males (state for small thumbed males unknown). Minor males unknown. Major males, thumb distally rounded and on the proximal half of the propodus. Dactyl expanded close to the junction with the propodus but not centrally toothed.
Adult female: Unknown.
Description.
Male, holotype. Length ~ 4.7 mm.
Antenna 1: each article with long filter setae on the posterior margin; accessory flagellum 2 articles, the second minute; flagellum 4 articles, each bearing aesthetascs.
Antenna 2: stouter than antenna 1 and overlapped by antenna 1 to 2/3 the length of article 5; distal part of article 4 and full length of article 5 and flagellum bearing plumose setae on the posterior margin in addition to filter setae which are about the same length; flagellum 4 articles, article 1, 50% of flagellum length, article 4, 40% as long as article 3, flagellum articles 2–4 bearing curved spines posterodistally.
Mandible: palp articles 2 and 3 without dorsal fringe of setae; raker spines 1 right, 4 left.
Maxilla 1: inner plate bearing a few short, fine setae; palp without setae at the base of article 1; article 2 with 1 row of facial setae.
Gnathopod 1: coxa produced forward, coxal margins, anterior 175% of dorsal length, ventral margin straight; basis flanged anteriorly, anterior margin without a fringe of long setae (all setae minute), posterior margin without setae; carpus, posterior lobe 45% of anterior margin length, without an anterodistal setal cluster; propodus, palm convex, defined by 3 spines (medial-lateral-medial), these mid-distant along the palm; dactyl facially striated.
Gnathopod 2: coxa rounded, coxal margins, anterior 26% and posterior 38% of ventral length, ventral margin convex; gill present; carpus, posterior lobe with a cluster of setae; propodus, anterior margin with only a few minute setae proximally (setae << the width of the basis), palm with a few plumose setae at the dactyl hinge, defined by a long, straight thumb that is rounded at the tip, without palmar defining spines, thumb length 35% of propodus length.
Pereopod 3: coxa deepest posteriorly; basis, margins convex; merus, setae 1/2 article width, article width maximally 65% of length; carpus nearly 100% overlapped by the merus; propodus not posteriorly spinose.
Pereopod 4: coxa nearly rectangular, deeper than wide, ventrally convex; other articles as for pereopod 3.
Pereopods 5–6: missing.
Pereopod 7: coxa-ischium missing, distal articles slender, propodus not distally expanded, with small spines only anterodistally at the junction of the dactyl; dactyl, posterior (outer) margin not cusped distally, anterior (inner) margin bearing a seta only at the unguis.
Pleopods: missing.
Uropods: missing.
Telson: missing.
Condition. Mouthparts, right antennae 1 and 2, gnathopod 1, left gnathopod 2, and right pereopods 3 and 4 slide mounted. Whole body with left antenna 2 and gnathopod 1, right gnathopod 2 (coxa to merus) and left pereopod 4 in 70% ethanol. Missing posterior portion of the body from pereon segment 4 onwards, which had been removed for CO1 analysis.
Variation. Maximum body length: male ~ 4.8 mm.
Type material examined. Holotype, male, ~ 4.7 mm, from macroalgae at Praia Norte, Viana do Castelo, Portugal (41.6938, -8.85118), Pedro Gomes, collector, 23 September 2010, Specimen ID SFC 29-003, Process ID FCCOM341- 11. Donated by Filipe Costa, University of Minho, Portugal, to the Canadian Museum of Nature (CMN A2019.0061, catalogue no. CMNC 2019-1385). Paratype, male, ~ 4.8 mm, same location, date and collector, Specimen ID SFC 29- 002, Process ID FCCOM340-11 (catalogue no. CMNC 2019-1386).
Etymology. Named in honour of artist Susan Laurie-Bourque who skillfully illustrated all the plates for this paper, Conlan (1990; in press), and many earlier taxonomic treatments.
Remarks. Jassa laurieae is only known from the holotype and paratype specimens which are both major form adult males. Both specimens had the posterior portions of their body removed for CO1 analysis, with the results published in Lobo et al. (2017). Body length has been estimated based on the expected length of the remaining body using J. kimi as a model, which is similarly sized. The actual body portion available for study was 1.8 mm long for the holotype and 1.2 mm long for the paratype. Lobo et al. (2017) considered J. laurieae to be a Portuguese variant of J. pusilla, but the CO1 analyses revealed that both the holotype and paratype were genetically similar and clearly distinct from North Sea specimens of J. pusilla as well as from Portuguese and North Sea J. falcata, J. herdmani and J. marmorata, and from U.S. J. staudei.
Jassa laurieae is only known from the Atlantic coast of Portugal, where it may be found with J. falcata, J. pusilla and J. herdmani (Fig. 9). Morphologically, the major form males of J. laurieae and J. falcata are similar in appearance at the anterior end, with plumose setae on antenna 2, minute setae on the anterior bases of gnathopods 1 and 2, absence of a seta or cluster of setae on the anterodistal margin of the gnathopod 1 carpus at the junction of the propodus, and relatively long thumb with rounded tip. The two differ in that J. laurieae lacks the dorsal fringe of setae on article 2 of the mandibular palp which both J. falcata and J. herdmani consistently possess in both sexes and all ages. Jassa falcata is also distinctive in having 1–2 spines midway along the inner ramus of uropod 3, but the state for J. laurieae is unknown. Large major form J. falcata have a very long thumb which is more squared at the tip than in J. laurieae but there are too few specimens of the latter to determine variation.
Jassa laurieae is less similar in appearance to congener J. pusilla than to J. falcata in the major form male, although the females and juveniles may prove to be more similar. Major form males of J. pusilla develop an indent at the tip of the thumb and never have plumose setae on the antenna 2. Both species are similar in lacking the dorsal setal cluster on article 2 of the mandibular palp and lack of a seta or setal cluster on the anterodistal junction of the carpus with the propodus on gnathopod 1. They are also similar in their small body length, while J. falcata achieves a greater length. Until more specimens of J. laurieae are found, these two species are currently only distinguishable by the major form male. Additional distinguishing characters may occur on the posterior region of the body, though.
Jassa herdmani bears the distinguishing setal fringe on article 2 of the mandibular palp (any age, both sexes), and this serves to easily separate it from J. laurieae. Major form males of J. herdmani do not bear plumose setae on antenna 2 and achieve greater body size.
description: Published as part of Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1) on pages 94-97, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/4580622