Jassamonodon ( Heller, 1866 )

Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, Zootaxa 4939 (1), pp. 1-191 : 97-102

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 ).

Figures

FIGURE 1. Progressive discovery of Jassa marmorata from 1850 to 1949. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 2. Progressive discovery of Jassa marmorata from 1850 to 2020. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 3. Progressive discovery of Jassa slatteryi from 1850 to 1949. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 4. Progressive discovery of Jassa slatteryi from 1850 to 2020. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 5. Progressive discovery of Jassa morinoi from 1850 to 1949. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 6. Progressive discovery of Jassa morinoi from 1850 to 2020. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 9. Records of Northern Hemisphere species of Jassa that were found in the eastern and/or western North Atlantic and seas, along with J. kimi in the western Pacific. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 56. Jassa monodon (Heller, 1866). Holotype, subadult male, 5 mm, CR 20619. Lesina (Hvar, Croatia), 1865, C. Heller, coll. (NHMW). Left side of body with magnification of the left second gnathopod. Photographs by Peter Dworschak (NHMW) with adjustments by S. Laurie-Bourque.

FIGURE 57. Jassa monodon (Heller, 1866). Holotype, subadult male, 5 mm, CR 20619. Lesina (Hvar, Croatia), 1865, C. Hell- er, coll. (NHMW). Right side of body with magnifications of the right antennae 1 and 2, left pereopod 3 or 4, right or left pereopod 7 and third uropods and telson as viewed from the right side. Photographs of the appendage magnifications by K.E. Conlan (CMN). Photograph of uropod magnification by Peter Dworschak (NHMW). Photograph adjustments by S. Laurie-Bourque.

FIGURE 58. Jassa monodon (Heller, 1866).Adult male, major form, length unknown, CR 20621. Lesina (Hvar, Croatia), 1865, C. Heller, coll. (NHMW). Left side of body with magnification of the left second gnathopod. Photographs by Peter Dworschak (NHMW) with adjustments by S. Laurie-Bourque.

FIGURE 59. Jassa monodon (Heller, 1866). Adult male, major form, length unknown, CR 20621. Lesina (Hvar, Croatia), 1865, C. Heller, coll. (NHMW). Right side of body with magnification of the right second gnathopod. Photographs by Peter Dworschak (NHMW) with adjustments by S. Laurie-Bourque.