Ventojassa frequens
Creators: name: Conlan, Kathleen E.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ischyroceridae
Ventojassa
Ventojassa frequens

description: Ventojassa frequens (Chilton, 1883)
(Figs 8–16)
Podocerus frequens Chilton, 1883, 85, Plate III, Fig. 2; Thomson & Chilton, 1886, 143; Shaw & Poore, 2016, 37–38
Podocerus latipes Chilton, 1884, 258, Plate XIX, Fig. 2; Thomson & Chilton, 1886, 143; Shaw & Poore, 2016, 38
Jassa frequens (Chilton), Stebbing, 1906, 656; Chilton, 1921, 227, Fig. 4; Schellenberg, 1931, 253; 1953, 119–120, Fig. 6; J. L. Barnard, 1958, 85
Jassa pusilla: K. H. Barnard, 1932, 242–243
Jassa barnardi Stephensen, 1949, 50–52, Figs 21, 22; J. L. Barnard, 1958, 84
Ventojassa frequens (Chilton), J. L. Barnard, 1972, 135–137, Figs 74–75; Griffiths, 1975, 138, 140; Gonzalez, 1991, 58
Description of male. Type: based on CMNZ 2015.149.86 (Fig. 8). (Character states for the two males in Figs 10 and 11 added in brackets and italics if the appendage is obscured in the type). Length 4.0 (3.6, 3.3) mm.
Antenna 1: accessory flagellum 2 articles (right), 3 articles (left).
Antenna 2: similar in length and width to antenna 1, with filter setae in the male as long as in the juvenile and female; flagellum 7 articles, the last as long as the second last, article 1 25% of full length, articles 5–7 posterodistally spinose.
Mouthparts obscured (Mandible: articles 2 and 3 with a dorsal fringe of setae; raker spines, 4 right, 2 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 distally).
Gnathopod 1: coxae to propodus obscured (coxa rectangular, coxal margins, anterior 70% of dorsal length, ventral margin gradually rounded; basis, anterior margin without a fringe of setae laterally, with only a few setae at the anterodistal junction with the ischium, with 1 long seta on the posterior margin; carpus, length 90% of propodus length, posterior lobe 60% of anterior margin length, anterodistal setal cluster short, 5% of the anterior margin length; propodus, palm convex, defined by 1 spine); dactyl cusped distally, without facial striations.
Gnathopod 2: (with a gill); coxae to antero-proximal part of propodus obscured (coxa not deeper posteriorly, coxal margins, anterior 100% and posterior 100% of ventral length, ventral margin gradually rounded; basis, anterolateral flange without a row of long, simple filter setae; carpus, anterior margin 50% the length of the propodus anterior margin, posterior lobe with a cluster of short distal setae; propodus, anterior margin with only a few distal clusters of short setae (setae about 20% of basis width)); propodus without hinge teeth, palm sparsely setose throughout, without a palmar defining spine, thumb conical in shape, 20% the length of the propodus and carpus combined; dactyl shorter than propodus, not expanded near the hinge, tip apposing the thumb tip, inner margin cusped.
Pereopod 3: coxa and basis obscured (coxa deepest centrally; basis wider than the gnathopod 1 basis, anterior margin shallowly convex); merus, anterior margin with one seta midway and cluster of setae distally, article width 70% of length; carpus barely 20% overlapped by merus; propodus width 47% of length, not posteriorly spinose.
Pereopods 5–7: proximally obscured (robust, basis, merus, carpus and propodus all bearing spines singly or in clusters; at least one basis posterodistally produced); propodus not strongly expanded anteriorly; dactyl not facially serrated, posterior (outer) margin not cusped distally, anterior (inner) margin setose only at the junction of the unguis.
Pleopods: each with 2 coupling hooks (rami short, ≤ depth of the pleon).
Urosome: segment 1 with pair of dorsally erect setae.
Uropod 1: obscured (posteroventral spinous process underlying 83% of the inner ramus, inner and outer rami with 2 mid-dorsal spines, outer ramus with 3 mid-dorsal spines, inner ramus with 1, in addition to the distal spine group).
Uropod 2: obscured (peduncle, posteroventral spinous process underlying 25% of the inner ramus).
Uropod 3: partially obscured (peduncle not mid-ventrally setose, without mid-dorsal spines, without spines at the insertion of the rami, but with a cluster of setae distolaterally); outer ramus with 2 erect setae mid-dorsally (and tipped by 2 small, straight spines distolaterally and adjacent small cusp; inner ramus not mid-dorsally spinose or setose, with a single apical spine).
Telson: partially obscured, with a pair of strong cusps dorsolaterally (and a single cusp at each dorsal apex, accompanied by a strong, erect seta and pair of small plumose setae).
Condition. Whole body slide mounted; missing one pereopod 7.
Description of adult female. Type: based on CMNZ 2015.149.85 (Fig. 9). Descriptions of characters not visible in the type are in brackets and italics and based on the adult female in Fig. 10. Length 3.8 (4.0) mm. Character states as in the male except as follows.
Brood plates: obscured (relatively slender, setae well separated, abundant, hook-tipped).
Antennae 1 and 2: similar in length, article 5 without plumose setae, simple filter setae as long as those of the male.
Gnathopod 2: propodus without a hinge tooth, palm 40% of the posterior margin, setae not so dense as to obscure the palm’s shape, defined by 3 medial spines.
Condition. Whole body slide mounted. Without right antenna 2 and pereopods 5–7, left pereopods 5 and 7.
Variation. Maximum body length: male 4.5 mm, female 4.5 mm. There is some variation in the number of accessory flagellum articles on antenna 1. There can be 2 or 3 articles and this can also vary between right and left sides of an animal (Fig. 13). The females and small males can have 3 palmar defining spines on the propodus of gnathopod 2 rather than 2. The number of erect setae on the outer ramus of uropod 3 varies from 1 to 5.
Type material examined. Type, conical thumbed ♂, CMNZ 2015.149.86, Lyttelton Harbour, New Zealand, date unknown, Charles Chilton, coll. Type, adult ♀♀, CMNZ 2015.149.85 and 84, Lyttelton Harbour, New Zealand, date unknown, Charles Chilton, coll.
Other material examined. New Zealand: Lyttelton Harbour, date unknown but possibly 1883 or earlier, C. Chilton, coll., 3 conical thumbed ♂♂, 2 cubic thumbed ♂♂, 18 adult ♀♀, 5 juveniles (CMNZ 2015.149.575...604); Lyttelton, 28 Mar. 1928, 1 conical thumbed ♂, 5 adult ♀♀ (SNM); Brighton, Otago, New Zealand, Jan. 1890, C. Chilton, coll., 1 cubic thumbed ♂ (CMNZ 2015.149.2161); Stewart I., date unknown, H. B. Kirk, coll., 1 adult ♀ (CMNZ 2015.149.2116); Huaroa Point, Whangaparaoa Peninsula, Auckland Province, New Zealand (36.595°S, 174.836°E), 16 Feb. 1968, J. L. Barnard, coll., NIWA station E979, JLB NZ-14, low water level, on heavy stand of algae, including Cystophora torulosa and bases of dying Codium sp., 1 cubic thumbed ♂ (NIWA 7825), 1 adult ♀ (NIWA 7835), 1 cubic thumbed ♂ (NIWA 7839); St. Kilda Rocks, Kaikoura (42.42°S, 173.7°E), 8 Nov. 1973, G. D. Fenwick, coll., 3–4 m depth on Caulerpa brownii and green algae, 8 cubic thumbed ♂♂ (AM P.25948) and ~ 50 specimens (MNZTPT CR.007823); Fraser Rocks, Tapeka, Bay of Islands, Northland, 15 Nov. 1995, 0–1 m, collector unknown, 31 conical thumbed ♂♂, 43 adult ♀♀, 23 juveniles (AuM MA 134534).
Tristan da Cunha: type series for Jassa barnardi Stephensen, 1949: Norwegian Scientific Expedition, E. Sivertsen, coll., Nightingale station 113, 8 Feb. 1938, 19 conical thumbed ♂♂, 37 adult ♀♀, 56 juveniles (SNM), Nightingale station 114, 8 Feb. 1938, 0 m, 6 conical thumbed ♂♂, 21 adult ♀♀, 7 juveniles (UiO F3934) and 1 conical thumbed ♂, 1 adult ♀ (CMNC 1994–0444), Inaccessible station 154, 25 Feb. 1938, 40 m, 1 conical thumbed ♂, 1 adult ♀, 10 juveniles (UiO F3898), Inaccessible station 156, 29 Feb. 1938, 5– 8 m, 3 adult ♀♀ (UiO F3897), station unknown, 30 Dec. 1939, 1 juvenile (SNM).
Chile: Caleta Bruna, date unknown, collector unknown., 1 conical thumbed ♂, 1 adult ♀, 1 juvenile (MNHN Am. 2649); Valparaiso, collector and date unknown, 1 conical thumbed ♂, 8 adult ♀♀, 2 juveniles (NRM 3786).
South Africa: False Bay, date unknown, C. Griffiths, coll., station FAL 604G, 1 cubic thumbed ♂, 1 juvenile ♂ (UCT).
Remarks. Ventojassa frequens does not exhibit sexual dimorphism in the antenna 2 but does in the gnathopod 2 and enlargement of pereopods 5 and 6 relative to 7. The pereopod enlargement is particularly pronounced in large females though large males show this enlargement to a lesser extent.
Chilton recognized two male morphs based on the male’s thumb shape and the expansion of the pereopods 5 and 6 (especially pereopod 6): conical thumb with “stout” pereopods 5 and 6 in his then named Podocerus frequens Chilton, 1883 and cubic thumb with “much expanded” pereopods 5 and 6 in his then named Podocerus latipes Chilton, 1884. However, Chilton (1884) had reservations about the two forms being different species, stating that Podocerus latipes “...may prove to be only a variety of P. frequens.” Chilton (1921) added some collecting information for these specimens, stating that they were fairly common in Lyttelton Harbour at the roots of Macrocystis and other seaweeds above low-water level. Chilton (1921) also pointed out that Stebbing (1906) had synonymized the two species as Jassa frequens (Chilton, 1883), regarding the cubic thumbed morph illustrated by Chilton (1884) to be the male and seemingly ignoring the conical thumbed male illustrated earlier by Chilton (1883).
Chilton’s type material listed in Shaw & Poore (2016) were kindly lent by the Canterbury Museum along with material from other locations listed above. The single male specimen that Chilton (1883) illustrated in his type description and Plate III, Fig. 2 was of a very small conical thumb (his Fig. 2b) and this drawing does not correspond with the long conical thumb borne by the male slide mounted and designated type CMNZ 2015.149.86 (Fig. 8). Chilton (1883) did note in his new species description that “The process on the propodos of second gnathopoda of male varies in size in different specimens, and is often longer and more distinct than shown in fig. 2b.” The other two type slides CMNZ 2015.149.84 and 85 are whole body mounts of adult females, but neither corresponds with Chilton’s (1883) Fig. 2, either. Chilton’s label on CMNZ 2015.149.84 states that the specimen is a male but it is actually an adult female with setose brood plates.
Chilton (1921) also illustrated the cubic thumbed type of male gnathopod 2 in Fig. 4A, p. 228 and this drawing matches the slide mounted male gnathopod 2 on Chilton’s slide CMNZ 2015.149.2161 from Brighton, Otago, New Zealand, collected Jan. 1890. Chilton’s (1921) Figs 4B, C correspond to dissected appendages of a female from Stewart Island, collected by H. B. Kirk (CMNZ 2015. 149.2116). Chilton’s (1921) Fig. 4D appears to be a pereopod 5 (not 6 as stated in the figure caption) but does not exactly match the pereopods on either of these slide mounts, showing fewer spines on the anterior margin of the basis.
Jassa barnardi Stephensen, 1949 from Tierra del Fuego (type shown in Figs 10 and 11) is clearly the same as Chilton’s conical thumbed male (type male shown in Fig. 8). It has the same slender antennae, slender propodus of gnathopod 1, conical thumb on the propodus of gnathopod 2, minimal overlap of the merus over the carpus on pereopods 3 and 4 and wide merus and carpus on pereopods 5–7 with strong spination on the posterior margins. The same features of the urosome, not visible on Chilton’s slide mount of the type is evident in his un-mounted specimens preserved in alcohol (CMNZ 2015.149.575...604). This forces its synonymy under Ventojassa frequens.
Additional illustrations of specimens from more recent collections are given here for comparison (Figs 12–15). Fig. 16 shows a graph of thumb length relative to body length in the conical thumbed and cubic thumbed males. The majority of specimens were taken from recent collections in New Zealand but they correspond well with specimens from Chilton’s collection. The contrast between the two morphs is shown in the much longer thumb in the conical thumbed males compared to the cubic thumbed males of the same body length. Within the longer conical thumbed group, there is no marked transition in thumb length, suggesting that thumb production occurs gradually over several molts rather than at the terminal molt as in Jassa (Conlan, 1989). For the cubic thumbed group, the largest specimen showed a longer thumb than the others, but more specimens are needed to determine variation.
Chilton’s two morphs may indeed be separate species, but this requires DNA analysis as no non-sexually dimorphic characters could be found that separated the two morphs. While large males could be distinguished based on thumb morphology (conical vs cubic), and large females found with the cubic thumbed males had grossly enlarged pereopods 5 and 6 while large females found with conical thumbed males had less enlarged pereopods 5 and 6, smaller females and thumbless males could not be assigned to the two morphs. In addition, the two morphs appeared to co-occur, as evidenced by Chilton’s collection from Lyttelton, New Zealand (CMNZ 2015.149.575...604), which contained 3 conical thumbed males and 2 cubic thumbed males, as well as adult females with a range of moderately to grossly enlarged pereopods 5 and 6. There was also a juvenile Jassa gruneri Conlan, 1990 mixed in. One of the two cubic thumbed males in this collection is the one likely used by Chilton (1884) to illustrate the second gnathopod of the male Podocerus latipes in his type description, as this appendage had been torn off from the right side and the left gnathopod 2 corresponded with his Plate XIX, Fig. 2b.
K. H. Barnard (1932) illustrated a conical thumbed male gnathopod 2 of a specimen named “ Jassa pusilla ” captured at Tristan da Cunha 30 Jan. 1926 at 40–46 m on a R. S. S. Discovery expedition. Stephensen (1949) noted that this was the same as his new species Jassa barnardi (herein transferred to V. frequens as stated above). He listed additional specimens to those examined for this study collected at Tristan da Cunha, Nightingale and Inaccessible Islands at 0–40 m depth. The specimens listed by Schellenberg (1931) from Valparaiso and Iquique, Chile (just south of Caleta Bruna) were possibly those examined for this paper and listed above. Schellenberg (1953) illustrated a cubic thumbed male gnathopod 2 and the urosome of a female from L̹deritz bay, Namibia (not seen). In his New Zealand study, J. L. Barnard (1972) collected V. frequens from washes of mixed species of low intertidal algae at stations in Dunedin, Lyttelton, Kaikoura, Wellington, and Leigh in addition to the cubic thumbed morph he illustrated from Huaroa Point and examined for this paper. These have not been seen but are likely to be the same cubic thumbed morph as otherwise, J. L. Barnard would likely have remarked on the difference. Additional unexamined collections of V. frequens from the Bay of Islands, Waitemata Harbour, Leigh, Hahei, and the Chatham Islands, New Zealand (0–12 m depth) are held at the Auckland Museum (AuM). Griffiths (1975) recorded two collections of V. frequens from False Bay, South Africa. No station number was given, so it could not be determined whether either of these corresponded to a single False Bay collection (station FAL 604G) that was lent by Griffiths for this study. This collection held a cubic thumbed morph.
There are eight species of Ventojassa currently known (ordered by date of description and collection location): V. ventosa (J.L. Barnard, 1962) from California, V. crenulata Ledoyer, 1979 from Madagascar, V. dentipalma Kim & Kim, 1991 from Korea, V. helenae Vader & Myers, 1996 and V. zebra Vader & Myers, 1996 from Australia, V. beagle Alonso, 2012 from Argentina and V. palauensis Myers, 2013 from Palau. Of these, V. frequens may be closest to the Australian V. helenae and V. zebra which share the broad merus and carpus on pereopod 5. However, V. frequens has a narrower palm of gnathopod 1, a different ornamentation of the palm of gnathopod 2, pereopod 5 is without stridulating ridges, and pereopod 6 is more spinose and (especially in larger males and females) markedly stouter than pereopod 7. Common to other species of Ventojassa, V. frequens has a strongly produced interramal spinous process underlying the rami of uropods 1 and 2 but this is almost as long as the rami, where in other species it is typically shorter.
description: Published as part of Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1) on pages 18-30, DOI: 10.11646/zootaxa.4921.1.1, http://zenodo.org/record/4496015