Petalidium foliaceum, BATE, 1881

Vereshchaka, Alexander L. & Lunina, Anastasia A., 2015, Phylogeny and taxonomy of the enigmatic genus Petalidium (Decapoda, Sergestidae), with biological remarks, Zoological Journal of the Linnean Society 174 (3), pp. 459-472 : 466-468

PETALIDIUM FOLIACEUM BATE, 1881 ( FIGS 2A , 3A–C )

Petalidium foliaceum Bate, 1881: 194 ; 1888: 349, plate 60. Hansen, 1896: 936; 1903: 54, plate II, figure I. Illig, 1914: 372, figures 31–34. Stebbing, 1914: 284, plate 28. Burkenroad, 1937: 326. Hale & Johnston (1941): 261, figures 1, 2.

Material examined: Dana stations 3630-1 (1 f 11 mm, catalogue number YPM IZ 040426), 3642-2 (2 ff 10.5– 16.5 mm; 1 juv 6 mm, catalogue number YPM IZ 040430), 3642-3 (2 ff 9–10 mm, catalogue number YPM IZ 040427), 3642-4 (1 f 6 mm, catalogue number YPM IZ 040428), 3656-1 (1 f 22 mm, catalogue number YPM IZ 040425), 3656-3 (1 f 15 mm, catalogue number YPM IZ 040429), 3978-7 (1 m 8½mm), 3978-8 (6 juv 5 mm). Challenger Expedition, Station 159, South Australia (syntype, Natural History Museum, catalogue number 1888.22), Station 146, Marion Island (five syntypes, Natural History Museum, catalogue number 1888.22 (four syntypes) and 1903.6.6.16 (1 syntype).

Type material: Six syntypes of Petalidium foliaceum , Natural History Museum (see above).

Type locality: Off Marion Island , 46°46′S, 45°31′E, depth 2516 m . South of Australia, 47°25′S, 130°22′E, depth 3935 m .

Diagnosis: Hepatic spine present; petasma with LAc (3–4 hooks) stronger than LA (1–2 hooks), LT bearing 4–5 and 1–2 hooks on branches; no arthrobranchs on somite XIII.

Remarks: Both males and females of this species may be distinguished from the other species of the genus by the absence of any arthrobranchs above pereopod IV. In addition, in males, the Lac on the petasma is significantly more robust than the LA. According to our data, any specimens found south of 35°S belong to this species. Petalidium foliaceum and P. obesum cooccur in the South Atlantic between 30°S and 35°S; if taken from in this area, P. obesum is easily distinguished by the absence of an hepatic spine and by its much more slenderer Lac.

Ethymology: from the Greek ‘foliaceum’, meaning foliaceous, leaf-like.

Geographical distribution ( Fig. 7 ): Most of the southern seas between 35°S and 66°S: South Atlantic, South of Africa ( Illig, 1914; Kensley, 1971, 1981; Dana material), southern Indian Ocean, ( Bate, 1888; Stebbing, 1914; Hale & Johnston, 1941), south of Australia ( Bate, 1888; Iwasaki & Nemoto, 1987), Antarctic Polar Frontal Zone of the Indian Ocean ( Pakhomov & Froneman, 2000). The species was recorded south of the Polar Front, in Western Antarctica ( Tiefenbacher, 1991), Prydz Bay (69°0′ 0″S, 75°0′ 0″E; Ikeda, 2013), and the Scotia and Weddell Seas ( Lancraft, Torres & Hopkins, 1989; Arntz & Gorny, 1991).

Vertical distribution: Recorded from the Dana stations 1500–5000-m wire corresponding to approximately 500–1700 m of actual depth ( Vereshchaka, 2000). Hale & Johnston (1941) reported the species from similar depths (1000–2000 m).

PETALIDIUM OBESUM ( KRØYER, 1859)

( FIGS 2B , 4A–E )

Sergestes obesus Krøyer, 1859: 257 , 279, plate 4 (figure 10a–f)

Sergestes sanguineus Chun, 1889: 538 (mastigopus stage)

Petalidium obesum Hansen, 1896: 968 ; 1903: 56; 1922: 190, plate 11 (figures 3, 4). Burkenroad, 1937: 324. Wasmer, 1974: 165

Petalidium foliaceum non Bate, Illig, 1927: 282, figures 1–5

Material examined: Dana stations 1142-4 (3 mm 6.5– 7.5 mm; 5 ff 7.5–10 mm); 1156-5 (1 m 6 mm; 6 ff 7.5– 9 mm); 1156-7 (4 m 6.5–7.5 mm; 10 ff 7.5–9 mm); 1156-9 (1 f 7.5 mm); 3978-7 (1 m 8 mm; 3 ff 8–10 mm); 3980-7 (6 mm 6.5–8 mm; 7 ff 8–10 mm); 3980-8 (3 mm 6–9 mm; 3 ff 6 mm); 3978-4 (2 mm 6 mm; 1 f 9 mm)

Type material: holotype of Sergestes obesum ( Krøyer, 1859) , Zoological Museum, Copenhagen University, catalogue number CRU-007582.

Type locality: Central Atlantic , 4.5°N, 21.5°W .

Diagnosis: Hepatic spine absent in adults; petasma with LAc (1–3 hooks) more slender than LA (6–10

hooks), LT bearing 0–3 and 1–3 hooks on branches; arthrobranchs on somite XIII lamellar.

Remarks: Both males and females of this species may be distinguished from the other species of the genus (1) by the absence of an hepatic spine in adults and (2) by the arthrobranchs above pereopod IV being lamellar. In addition, in males, the Lac of the petasma is much more robust than the LA. According to our data, any specimens found in the Atlantic Ocean North of 30°S belong to this species.

Geographical distribution ( Fig. 7 ): Atlantic Ocean between 45°N and 35°S: of Cape Verde, Canary Islands, Azores Islands ( Hansen, 1922; Dana Stations), Northwest Atlantic (Yale Peabody Museum material, Dana material) Central Atlantic ( Krøyer, 1859), and South of Africa ( Kensley, 1981; Dana material).

Vertical distribution: Recorded from the Dana stations 3000–5000-m wire corresponding to approximately 1000–1700 m of actual depth.

PETALIDIUM SUSPIRIOSUM BURKENROAD, 1937

( FIGS 2C , 5A–D )

Petalidium suspiriosum Burkenroad, 1937: 325 , figures 8–12. – Pearcy & Forss, 1966: 1136–1137, 1140. – Wasmer, 1974:160, figures 1–8.

Material examined: Templeton Crocker Expedition , Zaca Station 165, T-3 (syntype, two appendages, YPM IZ 039178 and syntype, 1 f 7 mm, IZ 068756) .

Type material: Two syntypes of Petalidium suspiriosum, Yale Peabody Museum (see above).

Type locality: Gulf of California, 20.60°N, 115.12°W .

Diagnosis: Hepatic spine present; petasma with LAc (5–6 hooks) subequal to LA (9–11 hooks), LT bearing 0 and 2 hooks on branches; arthrobranchs on somite XIII dendritic.

Remarks: Both males and females of this species may be distinguished from the other species of the genus by the arthrobranchs above pereopod IV being dendritic. In addition, in males, the Lac is subequal to the LA (it is much more slender in R. obesum and significantly more robust in P. foliaceum ). Also, the LA of P. suspiriosum bears many more hooks (> 8) than in other species. According to recent knowledge, any specimens found in the Pacific Ocean North of 20°N belong to this species.

Geographical distribution ( Fig. 7 ): Only found in the North Pacific between 20°N and 52°N: off Oregon ( Pearcy & Forss, 1966; Krygier & Pearcy, 1981), off Hawaii ( Walters, 1977), and off Japan ( Kikuchi & Omori, 1985). Specimens in the Oregon State University, Department of Oceanography collections have been taken as far north as 51°40.9′N 138°30.3′W and as far south as 34°23′N 140°46′W ( Wasmer, 1974). The most southerly capture record is that of the type locality, 20°36′N 115°07′W ( Burkenroad, 1937), where specimens were evidently brought from the north by the cold California Current.

Vertical distribution: 750–1500 m (off Hawaii, Walters, 1977), 800–2000 m ( Kikuchi & Omori, 1985).

Figures

Figure 2. Branchial chamber, arthrobranchs on the somites IX–XIII. A, Petalidium foliaceum, male ZMUC-CRU- 20546. B, Petalidium obesum, male ZMUC-CRU-20547. C, Petalidium suspiriosum, female, YPM IZ 068756. d.p., dendritic part of the arthrobranch; l.p., lamellar part of the arthrobranch. Scale bar = 1 mm.

Figure 3. Petalidium foliaceum, male ZMUC-CRU- 20546. A, lateral view of anterior part of carapace. B, petasma, la, lobus armatus; li, lobus inermis; lt, lobus terminalis; pv, processus ventralis; pu, processus uncifer. C, uropod (Hale & Johnston, 1941). Scale bar = 2 mm. LI, lobus inermis; LT, lobus terminalis; PV, processus ventralis; LC, lobus connectens; LAc, lobus accessorius; LA, lobus armatus; PU, processus uncifer.

Figure 4. Petalidium obesum, male ZMUC-CRU-20547. A, lateral view of anterior part of carapace. B, male clasping organ. C, petasma. la, lobus armatus; lc, lobus connectens; li, lobus inermis; lt, lobus terminalis; pv, processus ventralis. D, uropodal exopod. E, scaphocerite. Scale bar = 2 mm. LI, lobus inermis; LT, lobus terminalis; PV, processus ventralis; LC, lobus connectens; Lac, lobus accessorius; LA, lobus armatus; PU, processus uncifer.

Figure 5. Petalidium suspiriosum. A, lateral view of anterior part of carapace (YPM IZ 068756, female, syntype). B, male clasping organ. C, petasma. a, pars externa; e, pars astrigens; la, lobus armatus; lc, lobus connectens; li, lobus inermis; lt, lobus terminalis; m, pars media; pb, processus basalis; pv, processus ventralis. D, uropod. Scale bar: (A) = 2 mm, (B) = 4 mm, (C) = 1 mm. (A–C, Wasmer, 1974; D, Burkenroad, 1937). LI, lobus inermis; LT, lobus terminalis; PV, processus ventralis; LC, lobus connectens; Lac, lobus accessorius; LA, lobus armatus; PU, processus uncifer.

Figure 7. Macroscale geographical distribution: Petalidium foliaceum (pink), Petalidium obesum (green), and Petalidium foliaceum (crimpson). Type localities (black circles) and Dana stations (yellow circles) are indicated; filled areas are supported by literature data.