Jassa alonsoae Conlan 1990

Jassaalonsoae Conlan, 1990

(Table 13, Figs 88–91)

Diagnosis.

Both sexes:

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 row of short setae along its length; carpus with a cluster of moderately long setae at the anterodistal junction of the propodus (setal length about 1/3 the length of the anterior margin).

Gnathopod 2: basis with a row of setae along the anterolateral margin (at least some setal lengths>40% of the basis width); 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 without apical setae (only the usual short setae at each dorsolateral cusp).

Thumbed male:

Antenna 2: without plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palmar defining spines not produced on a ledge, present in small thumbed males but absent in large thumbed males. In major males, the thumb is distally squared, the posterior margin sinuous. The dactyl is expanded close to the junction with the propodus but is not centrally toothed. Minor form males have a short, squared thumb and a dactyl tooth. Subadult males have a small prethumb.

Adult female:

Antenna 2: large animals without plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palmsinuous.

Remarks. Jassa alonsoae, J. justi, J. fenwicki, J. ingens and J. hartmannae have a fringe of setae along the anterior margin of gnathopod 1 which may be robust and spine-like (Figs 88–90, 92, 95, 99 and 104). Jassa alonsoae differs from the others in having long setae on the basis of gnathopod 2 while the others have short setae similar to the basis of gnathopod 1. The row of setae on the gnathopod 1 basis is a distinctive character, which is only known for these Southern Hemisphere species. However, it is difficult to see on small animals and in J. ingens the setae do not run the full length in all animals (Fig. 99). The other Southern Hemisphere species (J. thurstoni, J. kjetilanna and J. gruneri) seem to lack this fringe although there can be minute setae present (Figs 93, 96 and 102). The sinuous shape of the female’s gnathopod 2 palm is a feature of several (but not all) Southern Hemisphere species also (J. alonsoae, J. thurstoni, J. fenwicki, J. kjetilanna, J. ingens and J. gruneri) (Figs 88, 90, 93, 95, 97, 100 and 102). However, it is not unique to the Southern Hemisphere as the other two Southern Hemisphere species, J. justi and J. hartmannae have shallowly concave palms (Figs 92 and 104) and the Northern Hemisphere J. myersi has a sinuous palm (Fig. 85). The other Northern Hemisphere species (and the transhemispheric species) have more clearly concave palms.

Jassa alonsoae has been found more frequently than the other Southern Hemisphere species (Fig. 11). It has a wide longitudinal range but has not been found south of 60°S. Specimens described by Stephensen (1949) as “ Jassa pulchella ” w ere examined (SNM) and are J. alonsoae. Conlan (1990) noted other mis-identifications. Monod (1926) mentioned a collection of “ J. falcata ” from the carapace of the spider crab Eurypodius latreilli in the Strait of Magellan. Although these specimens have not been seen, they may be Jassa alonsoae as this species has been collected in this area and it was found on spider crabs in a Falkland Island collection (AM P.31689). Monod’s illustration of the female gnathopod 2 resembles that of J. alonsoae. Stebbing’s (1888) “ Podocerus falcatus ” from Greenland Harbour, Kerguelen Island (Challenger station 149E) may also be J. alonsoae. Its sinuous gnathopod 2 palm suggests an indigenous Southern Hemisphere species and J. alonsoae is the only species known from Kerguelen Island (Fig. 11). It is figured by Stebbing (1888) on Plate CXIX along with a female collected off the ship’s screw at Challenger station 142, off South Africa. Examination of this female (NHM) found that it is not J. alonsoae but J. marmorata. A description of the Challenger stations at http://www.19thcenturyscience.org/HMSC/HMSC-INDEX/index-linked.htm indicates that there was a second collection of Jassa at Kerguelen Island (Challenger station 149) but this was from the ship’s screw “after leaving the Cape ”. Examination of this collection found it to be also Jassa marmorata, indicating that this species was travelling with the ship.