Jassa monodon
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 monodon

description: Jassamonodon (Heller, 1866)
(Table 11, Figs 56–59)
Podocerus monodon Heller, 1866, pp. 45–46, plate IV, figs. 4, 5; not J. falcata: Krapp-Schickel (1974), p. 344.
Diagnosis.
Mandibular palp: article 2, dorsal margin without a fringeof setae.
Maxilla 1: state unknown.
Gnathopod 1: basis, anterolateral margin without a setal fringe along its length; carpus without a seta or cluster of setae at the anterodistal junction of the propodus.
Gnathopod 2: basis with 5–7 widely spaced setae along the anterolateral margin (setal length 1/2 to 2/3 the width of the basis); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width).
Pereopods 5–7: propodus not expanded anteriorly.
Uropod 1: ventral peduncular spinous process underlying about 1/3 of the longest ramus.
Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine).
Telson: tip with 1–2 apical setae in addition to the usual short setae at each dorsolateral cusp.
Condition. Without left gnathopod 1, right pereopods 5–7 and left pereopod 5. Right antennae 1 and 2, left pereopods 3, 4 and 7 broken from the animal but present in the vial.
Thumbed male:
Antenna 2: missing (subadult, peduncular article 5 with long filter setae; flagellum with short brush setae (not plumose setae)).
Gnathopod 2: propodus, palmar defining spines absent in the major form, thumb long, more than half the length of the propodus and distally acute. Dactyl expanded close to the junction with the propodus but not centrally toothed. Minor form unknown.
Condition. Without right and left antennae 1 and 2 and pereopods 5–7.
Adult female: unknown.
Remarks. Jassa monodon was first described by Heller (1866) as Podocerus monodon, based on a subadult male specimen collected at Lesina (Hvar, Croatia). No information on depth or substrate was given. This specimen is in the crustacean collection of the Naturhistorisches Museum Wien (NHMW 20619) and was examined by one of us (KC) in November 2018. Krapp-Schickel (1974) had previously examined this specimen and called it a female Jassa falcata. Asecond specimen of Jassa monodon (NHMW 20621) was also found in Heller’s collection from Lesina and named Podocerus pulchellus in Heller (1866) and Krapp-Schickel (1974). This specimen is a major form thumbed male. These are the only two specimens known for this species. Due to their type status and fragility, the specimens could not be measured for body length or dissected for line drawing. Heller (1866) recorded the length of the holotype subadult male as 5 mm. The length of the major form adult male was not recorded.
Jassa monodon has a unique combination of diagnostic characters (Table 11). Other species that currently occur in the vicinity of the type locality for Jassa monodon are J. marmorata, J. slatteryi and J. morinoi (Figs 1–6, 9). The European J. pusilla and J. falcata are not known to occur in the Mediterranean Sea. The European J. herdmani has been found in the western part of the Mediterranean Sea but not as far east as the Adriatic, where J. monodon was collected. Tables 10 and 11 show the key distinguishing characters for these species.
Possibly the “ Podocerus falcatus ” described from Trieste, Italy by Nebeski (1880) was J. monodon mixed with J. marmorata. In interpreting this study, Sexton and Reid (1951) suggested that Nebeski (1880) was dealing with both a “Broad-form” and a ʺNarrow-form”. Conlan (1990) identified Sexton and Reid’s Broad-form as J. marmorata and their Narrow-form as being J. falcata or J. herdmani, but did not know of J. monodon ’s characteristics at the time. Both J. marmorata and J. monodon were known from the vicinity of Trieste in the 19 th century (Table 3, Figs 1 and 9).
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 97-102, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/4580622