Streptoleberis flexilis (Brady 1898) Eagar 1971

Philomedes flexilis Brady, 1898

HOLOTYPE.—Adult ♀ in collection of Universitets Zoologiske Museum, Copenhagen, Denmark, carapace length 1.87 mm.

TYPE-LOCALITY.—Akaroa Harbor, New Zealand.

ETYMOLOGY.—The species is named after Dr. Torben Wolff.

PARATYPES.—USNM 135044, gravid ♀; USNM 135045, 2 specimens; Universitets Zoologiske Museum, 36 specimens. Paratypes from same sample as holotype.

MATERIAL.—Through Dr. Torben Wolff, I received on loan from the Universitets Zoologiske Museum, Copenhagen, Denmark, a vial with two labels: “Type” and “Philomedes flexilis Brady, orig. spec. Akaroa Harbour, 6 fm., H Suter, 8/97.” This vial contained 6 specimens that I identified as S. flexilis and 40 specimens that I refer to a new species, S. wolffi.

In the collection I received from Dr. McKenzie of the British Museum (Natural History) were two slides marked as follows: “♂ Philomedes flexilis Brady n. sp., type, Akaroa Harbour, N. Z. 6 fathoms water, 8/97” and “ ♀ Philomedes flexilis n. sp. types, Akaroa Harbour, N. Z. 6 fathoms water.” The slides are in poor conditions, but many single hairs are visible on the compressed carapace on the slide bearing the ♂. The absence of divided hairs leads me to believe that this specimen probably is S. wolffi. The carapace is absent on the slide bearing the ♀, and I consider this specimen as Scleroconcha species indeterminate herein.

DISTRIBUTION.—Known only from the type-locality (Figure 190).

Scleroconcha Species Indeterminate

MATERIAL.—USNM 127254, 1 juvenile from IWSOE, Glacier Cruise 2, station 0006, anchor dredge; USNM 126261, 1 juvenile from IWSOE, Glacier Cruise 2, station 0008, anchor dredge; USNM 127262, 1 juvenile, length 1.61 mm, height 0.95 mm, + 1 juvenile, both from IWSOE, Glacier Cruise 2, station 0002, anchor dredge; USNM 127481, 1 juvenile from Hero Cruise 69–1, station 12–B; USNM 137477, 1 N–1 ♂, Eltanin Cruise 47, station 5056 (generic identification questionable because of missing rod-shaped organ); USNM 128282, 1 ♀, length 1.65 mm, height 1.03 mm (specimen infested by nematodes) from Eltanin Cruise 20, station 91.

In addition, the following specimens borrowed from the Brady collection in the British Museum (Natural History) are considered to be Scleroconcha species indeterminate: 1 ♂ and 1 ♀ on slides from Akaroa Harbor, N. Z. (these specimens had been identified by Brady as Philomedes flexilis); 1 adult ♀, length 1.92 mm, height 1.31 mm, from Lyttelton Harbor, N. Z.

Because of the nematodes parasitizing USNM 128282, parts of the specimen have been illustrated (Figure 214).

DISTRIBUTION.—The distribution of Scleroconcha species indeterminate is shown in Figure 190.

Anarthron, new genus

TYPE-SPECIES.—Anarthron dithrix, described herein.

ETYMOLOGY.—The generic name “Anarthron” is derived from the Greek “an” [= not, without] and “arthron” [= joint] in reference to the absence of numerous distinct joints on the rod-shaped organ. Gender: neuter.

This new genus contains five species: A. reticulata (Hartmann, 1965); A. chilensis (Hartmann, 1965); A. pholion, new species; A. dithrix, new species, and A. evexum, new species. The new genus appears to belong between Scleroconcha and Philomedes—the shell resembles the former genus and the rod-shaped organ the latter.

DIAGNOSIS.—Carapace of female with 3 or 4 horizontal ridges; ridges stout on A. chilensis, A. evexum, and A. dithrix but weak on A. reticulata and A. pholion. Infold of rostrum with row of 7 to 11 bristles and several shorter bristles near outer edge; anteroventral infold striate and with about 15 short spinous bristles; infold of caudal process with short ridge bearing 1 bristle, and 2nd bristle near posterior edge of process; list of posteroventral and posterior infold with numerous small bristles forming groups with 1 to 6 bristles. Carapace of male with ridges subdued or absent.

First and second antenna, maxilla, mandible, fifth and sixth limbs: Similar to those of Scleroconcha.

Seventh limb: Limb of female with 4 proximal and 6 distal bristles; tip of limb opposite comb bare on known species; male with 4 or 5 proximal and 6 distal bristles.

Furca: Each lamella with 9 to 13 claws; A. reticulata with 4 stout claws followed by 8 or 9 shorter and weaker claws on female and 6 or 7 on male; remaining species, A. chilensis, A. dithrix, A. pholion, A. evexum, with 3 stout claws followed by 6 to 10 shorter and weaker claws. On A. reticulata, 3rd claw slightly more slender than 4th.

Scleroconcha flexilis (Brady, 1898)

Philomedes flexilis Brady, 1898:435, pl. 44: figs. 1–14; pl. 45: figs. 15, 16 [part].

Philomedes flexilis Brady.—Müller, 1912:29.

Philomedes (Scleroconcha) flexilis Brady.—Skogsberg, 1920:380.

Scleroconcha flexilis (Brady).—Poulsen, 1962:396, fig. 173.

Streptoleberis flexilis (Brady).—Eagar, 1971:61 [listed].

LECTOTYPE.—Gravid ♀ selected herein, Universitets Zoologiske Museum, Copenhagen, Denmark.

TYPE-LOCALITY.—Lyttelton Harbor, New Zealand, collected by dredge.

OTHER LOCALITIES.—Halfmoon Bay, Stewart Island, New Zealand; Akaroa Harbor, New Zealand.

MATERIAL.—Through Dr. K. G. McKenzie, I received some of Brady’s material in the collections of the Hancock Museum, Newcastle-on-Tyne:

1. One thick slide containing two complete undissected specimens and labeled, “Philomedes flexilis Brady (types), Lyttelton Harbor, N.Z.” Cracks in the mounting medium prevent clear view of the specimens and no information was derived from these specimens.

2. Two slides containing a dissected ♂ and ♀ from Akaroa Harbor and labeled “Philomedes flexilis n. sp., type, Akaroa Harbor, N.Z., 6 fathoms, H. Suter, 8/97.” The specimens are in poor condition and could not be clearly seen.

3. One dry specimen is noted as having been from a broken vial labeled, “Philomedes flexilis Brady, Lyttelton Harbour, N.Z.” I softened this specimen and confirmed the identification by the presence of divided hairs on the carapace and returned it to Dr. McKenzie in alcohol.

4. One vial of unsorted material containing a label indicating that it was from Lyttelton Harbor. The descriptions of males and females herein are based on specimens from the unsorted vial. The two adult males in the sample were not dissected; descriptions of appendages are based on appendages projecting from carapace.

Through Dr. Torben Wolff, I received on loan from the Universitets Zoologiske Museum, Copenhagen, Denmark, the following material:

1. Two specimens identified by Dr. Erik M. Poulsen (1965:396) as S. flexilis. The vial with the specimens contains two labels: “Zoologisk Museum, Kobenhavn; Loc. Lyttelton Harbour, New Zealand, 1–5 fv., Datum: 1–9–1897, Legit: H. Suter, Ostracoder, Journal. 18/1–1954” and “Scleroconcha flexilis (Br.) ZM. Lyttelton Harbour, New Zealand, 2–10 m, 1–9–1897, E.M. Poulsen det.” The vial contains one whole and one dissected specimen.

2. One dissected specimen from Halfmoon Bay, Stewart Island, N. Z., which also had been identified by Dr. Poulsen as S. flexilis. The vial contains two labels: “Scleroconcha flexilis (Br.), Halfmoon Bay, Stewart Isl., New Zealand, 19–11–1914, Mortensen Esq. E.M.P. det.” and “Ostracod, Halfmoon Bay, Stewart Isl. 5–7 Fv. Sand, Skrabe, 19.XI. 1914, Dr. Th. Mortensen Esq.”

3. A vial containing two labels: “TYPE,” and “Philomedes flexilis Brady, orig. spec., Lyttelton Harb., 1–5 fm.” In addition to about 229 specimens belonging to the genus Scleroconcha, in the vial were several specimens of Cymbicopia hanseni and C. hispida, which were removed and returned in separate vials to Copenhagen. Seventy-nine specimens of Scleroconcha were randomly selected (some bias for larger specimens) from the original 229. The bristles on the lateral surfaces of the carapaces were examined, and 77 with branched bristles were assigned to Scleroconcha flexilis. Two specimens with unbranched bristles were identified as S. arcuata Poulsen, 1962. At the request of Dr. Wolff, a lectotype of S. flexilis was selected; this and 71 paralectotypes were returned to Copenhagen with the unseparated specimens. Five paralectotypes were retained at the National Museum of Natural History, USNM 135043.

4. A vial with two labels: “Type,” and “Philomedes flexilis Brady, orig. spec., Akaroa Harbour, 6 fm, H. Suter, 8/97.” This vial contained six specimens of S. flexilis and 40 specimens described herein as a new species, Scleroconcha wolffi.

DIAGNOSIS OF FEMALE.—Each valve with 4 longitudinal ribs, 2 near middle, 1 along ventral margin, 1 along anterior half of dorsal margin; middle ribs on some specimens subdivided into 3 elongate nodes; lateral anteriad projection on rostrum extending just to, or barely beyond, anterior margin of rostrum; surface of valves with large pits; surface hairs commonly with 2 to 5 branches emanating from single stem; length of carapace 1.89 mm to 2.21 mm.

Seventh limb: Each limb with 10 bristles, 4 proximal, 6 distal; terminal comb with 11–13 alate teeth; 1 smooth peg present opposite comb.

SUPPLEMENTARY DESCRIPTION OF FEMALE (Figures 194–196).—Carapace oval with broad rostrum and incisur and small caudal process (Figures 194a-f, 196).

Ornamentation: Each valve with 4 longitudinal ridges, 2 near middle, 1 along ventral margin, 1 along anterior half of dorsal margin; ridges generally prominent; middle ridges on some specimens subdivided into 3 elongate nodes. Lateral anteriad projection on rostrum extending just to, or barely beyond, anterior margin of rostrum; tip of projection located ventral to middle of rostrum, some specimens with 2nd projection dorsal to middle of rostrum; latter projection not reaching past anterior margin of rostrum; on many specimens both projections coalescing, partly divided by depression; small anteriad projection also present below incisur. Surface of each valve with ovoid depressions or pits separated by rather broad areas between pits; surface of both pits and area between pits with small pustules, each with small central pore; small pustules also present on surface of ridges (Figure 196).

Carapace hairs: Hairs present on ridges, on anteriad projections and on areas between pits, but not within pits; most common hair consisting of single stem with 2 to 5 branches; hair pore through which hair passes as much as 5 times diameter of pustules on carapace; branching hairs varying in size; single hairs rare, branching hairs abundant on surface (Figures 194d, 196b-d).

Infold (Figure 194f): Infold on rostrum with 14 bristles; small bristle present below inner end of broad incisur followed by space and then 12 spinous bristles on anteroventral infold; anteroventral infold with about 10 striations, ventral infold bare; posteroventral and posterior list with numerous minute bristles in groups of 1 to 5 bristles; ridge with 4 bristles present between posterior list and outer edge of valve, upper bristle longer than others; 1 bristle present between ridge and posterior valve edge; several bristles forming row ventral to ridge.

Selvage: Striate lamella prolongation with short fringe present; lamellar prolongation discontinuous in area of incisur; long hairs with bases proximal to edge of prolongation present on prolongation ventral to incisur.

Size of gravid females (Figure 189): Lyttelton Harbor: specimen X, length 2.21 mm, height 1.56 mm; specimen Y, length 2.18 mm, height 1.46 mm; speciment Z, length 2.09 mm, height 1.52 mm. Lectotype, length 2.18 mm, height 1.61 mm. Akaroa harbor: gravid ♀, length 1.89 mm, height 1.40 mm.

First antenna: Lateral surface of 1st joint with about 10 clusters of short spines near distal dorsal margin; 2nd joint with short spines forming clusters on lateral and medial surfaces, longer spines and hairs forming clusters along ventral and dorsal margins, and usual 3 bristles, 1 lateral, 1 ventral, 1 dorsal; 3rd joint with 3 clusters of spines on lateral surface near distal margin, faint spines along ventral and dorsal margins, 2 dorsal and 1 ventral bristle; 4th joint with 2 dorsal and 4 ventral bristles and spines forming clusters on lateral surface and ventral and dorsal margins; sensory bristle of 5th joint with about 7 proximal and 5 distal filaments; medial bristle of 6th joint with long proximal and short distal spines. Seventh joint: a-bristle about same length as bristle of 6th joint and with long proximal and short distal spines; b-bristle with about 2 proximal and 4 distal filaments; c-bristle with 6 proximal and 4 distal filaments. Eighth joint: d- and e-bristles long, bare; f-bristle with about 4 proximal and 5 distal filaments; g-bristle with about 6 proximal and 5 distal filaments; minute protuberances present along distal ventral margin of f- and g-bristles near distal filaments (Figure 194g).

Second antenna (Figure 194h): Endopodite 2-jointed: 1st joint short with 5 bristles; 2nd joint elongate with 1 long stout spinous proximal bristle and 1 short recurved terminal bristle. Exopodite: bristles of joints 2 and 4 bare, bristles of remaining joints with natatory hairs (some bristles of 9th joint missing on limb examined).

Mandible (Figure 194i-k): Coxale with minute bristle present near base of bifurcate spinous endite. Basale: medial side with 6 bristles, 1 near middle with long proximal and short distal spines, 5 proximal (3 coarsely pectinate, 2 spinous); lateral surface with 5 bristles forming row parallel to ventral margin; ventral margin with 2 distal bristles; dorsal margin with 3 long stout distal bristles; lateral and medial surfaces spinous. Endopodite: 1st joint with spines forming clusters on medial surface and 4 ventral bristles; 2nd joint with spines forming clusters on medial surface and proximal part of dorsal margin; end joint with 4 bristles and 3 claws (all claws pectinate proximally; dorsal claw half length of longest claw). In other characters mandible same as described by Poulsen (1962:396). (The three specimens examined all have only 2 bristles in the proximal group of the ventral margin of the 2nd endopodite joint.)

Maxilla (Figure 194l-p): 1st endite with 10 spinous and pectinate bristles; 2nd endite with about 7 spinous and pectinate bristles; 3rd endite with about 10 spinous and pectinate bristles; 1st endite broader than 2nd and 3rd endites; 3rd endite much longer than 1st and 2nd endites. Endopodite: 1st joint with 5 β-bristles; 1 b-bristle, and 2 d-bristles of end joint with small marginal teeth. Limb otherwise similar to that described by Poulsen (1962:396).

Fifth limb (Figure 195a-d): Epipodial appendage with 52 bristles. Exopodite: inner margin of large tooth of 2nd joint with small tooth (Figure 195b); posterior side of outer distal corner of large tooth of 2nd joint with minute bristle; bristles in group of 3 on posterior side of 2nd joint bare. Main tooth and bristles on joints 2 to 5 similar to those on limb described and figured by Poulsen (1962).

Sixth limb: Endite I with 1 terminal and 2 unequal medial bristles; endite II with 3 terminal and 1 medial bristles; endites III and IV with 7 or 8 terminal and 1 medial bristles; end joint with 28–30 bristles; 3 or 4 bristles present in place of epipodial appendage; medial and lateral surfaces of end joint with abundant long hairs. Shape of limb similar to that figured by Poulsen (1962:387, fig. 173g).

Seventh limb (Figure 195e): Each limb with 10 bristles, 4 in proximal group (2 + 2) and 6 in terminal group (3 + 3); each bristle with 3 to 7 bells and marginal spines; terminal comb with 11 to 13 alate teeth; 1 smooth peg present opposite comb.

Furca (Figure 195f,g): Each lamella with 10 to 12 claws; claw 3 more slender and slightly longer than claw 4; claws 5 to 10 or 12 decreasing in length posteriorly along lamella. The number of claws on the furcae of 3 specimens is as follows:

Rod-shaped organ (Figure 195i): Elongate with about 18 segments at middle, tip pointed (examined only under low magnification).

Eyes (Figure 195i): Lateral eye elongate with 2 undivided ommatidia, about same length but only about three-fourths diameter of medial eye. (Sleeve of lateral eye transparent and easily overlooked; ommatidia orange and quite visible although small.)

Epizoa: Specimen X with numerous branching ball-tipped organisms attached to appendages (Figure 195h).

Parasites: Numerous coiled encysted nematodes were observed within body of four specimens. A few uncoiled nematodes were also observed between the carapace and body of one specimen which also contained encysted nematodes.

Eggs: Specimen X, 30; specimen Y, 6 (some eggs probably escaped from carapace into vial); specimen Z, 16.

SUPPLEMENTARY DESCRIPTION OF ADULT MALE (Figures 195k-o).—Carapace slightly shorter than female and not as high; incisur more open than that of female; ornamentation similar to that of female but horizontal ribs subdued; divided hairs present on surface of carapace but less abundant than on female. Carapace size (Figure 189): 3 specimens, length 2.04 mm, height 1.16 mm; length 2.00 mm, height 1.14 mm; length 2.06 mm, height 0.94 mm.

Second antenna: Endopodite normal for genus (Figure 195m).

Furca: 3rd claw more slender and slightly shorter or about same length as 4th claw; 11 claws observed on right lamella of specimen examined (Figure 195n); distribution of claws similar to those on furca of female.

Lateral eye: Well developed (Figure 195o).

Copulatory organ: Normal (Figure 195n).

SUPPLEMENTARY DESCRIPTION OF CARAPACES OF SPECIMENS IDENTIFIED AS S. flexilis BY POULSEN (1962:396) (2 specimens from Lyttelton Harbor, 1 specimen from Halfmoon Bay).—Lateral surfaces of each valve with numerous branched bristles.

DISTRIBUTION.—This species has been collected only from the vicinity of New Zealand at depths of 6 to 26 m (Figure 190).

REMARKS CONCERNING A SECOND SPECIES OF Scleroconcha IN LYTTELTON HARBOR.—All specimens of Scleroconcha in the sample I examined, with one exception, have numerous divided hairs on the carapace. The exception has only single hairs; for this reason, I believe that it is probably not conspecific with S. flexilis. The horizontal ridges on its carapace are quite subdued, but not more so than on some specimens of S. flexilis. Both lamellae of the caudal furca on the odd specimen have 12 claws. The remaining appendages, including the lateral eyes, are similar to those of S. flexilis. Carapace length of the specimen, an adult ♀ without eggs is 1.92 mm, height 1.31 mm. The lateral process on each side of the rostrum does not project beyond the lamellar prolongation as on S. arcuata Poulsen. It is possible that the specimen belongs to S. sculpta of which the ♀ is unknown, or is merely an aberrant S. flexilis. The specimen has been labeled “Scleroconcha type B from broken bottle B505” and returned to the British Museum (Natural History). In the present paper I consider the specimen as Scleroconcha species indeterminate.