Rutiderma lomae (Juday 1907)

Rutiderma lomae (Juday, 1907)

Philomedes lomae Juday, 1907:141, figs. 1–6.

Not Philomedes lomae.—Kornicker (1958:233, figs. 46:7A,B; 52A–E; 53A–D; 86A,E,I) [=Rutiderma dinochelatum Kornicker, 1958].

NEOTYPE.—USNM 158258, adult female on slide and in alcohol (BM 35), selected herein.

TYPE-LOCALITY.—OSCD sta B3, 33°34'15″N, 118°00'45″W, 9 Sep 1976.

SYNTYPES (not extant).—Tow net catches 124, 571, 589, 612 collected between San Pedro and San Diego. Because data on latitude and longitude and collecting vessel are not given by Juday (1907), it is given here from Ritter (1912) and Michael and McEwen (1915). Catch 124, 24 Jun 1904, 32°36'12″N, 117°21'30″W; catch 571, 27 Jul 1901, 32°41'00″N, 117°14'00″W; catch 589, no station data, but probably in vicinity of San Pedro based on data available on catches 586 and 590 obtained before and after catch 589; catch 612, 30 Jun 1903, 32°40'36″N, 117°10'30″W. Catch 124 was taken from the yacht Loma belonging to E. W. Scripps; catch 571 was collected from the launch Elsie; catch 612 was probably collected from the small schooner Laura.

MATERIAL STUDIED.—Neotype; USNM 158259 (BM 43), adult female collected off Santa Catalina Island by James R. Chess; USNM 158260 (BM 20–3) and USNM 158261 (BM 20–2), 2 adult males collected off Santa Catalina Island by James R. Chess; USNM 158265 (BM 19), 1 instar III female, Oxnard sta C-4-2, 37 m; USNM 158266, 1 late female instar (length 1.32 mm), Velero IV, sta 5092, 33°31'09″N, 117°48'03″W, 22 May 1957, sediment temperature 9.8°C.

REMARKS CONCERNING NEOTYPE SELECTION.—Because Juday's specimens are not extant, and it seems unlikely that the male of the species is identifiable from the brief description and few illustrations of Juday (1907), we have designated another specimen—USNM 158258, adult female—as the “neotype” of the species.

DESCRIPTION OF ADULT FEMALE (Figures 5–7e).—Carapace oval in lateral view with convex ventral and dorsal margin, moderately well-developed incisur and small caudal process (Figure 5).

Ornamentation (Figure 5): Each valve with 2 well-developed horizontal ribs, 1 above and 1 below central adductor muscle attachments; posterior end of each rib terminating in small process; posterior end of lower rib curving dorsally and posterior end of upper rib curving slightly ventrally forming vertical rib with space near middle; very faint radial riblets extend from anterior part of upper rib to anterodorsal valve margin, and from lower rib to ventral margin; short undulate ridge present just below posterior end of lower rib in front of caudal process; faint vertical rib present just posterior to incisur; low process present near middle of truncate posterodorsal margin of each valve; no processes on dorsal margin of either valve. Surface of valves with abundant small fossae. Numerous long bristles present along anterodorsal, anterior, and ventral valve margins and sparsely distributed on valve surface.

Infold (Figure 6a,b): Rostral infold with 10–12 long bristles forming irregular row paralleling valve edge; 2 small bristles present at inner end of incisur; anteroventral infold with 11 bristles; middle part of ventral infold without bristles; posterior one-third of ventral margin anterior to ventral end of ridge on infold of caudal process with 11 short bristles; 8 or 9 bristles forming row just anterior to ridge on infold of caudal process; 3 small bristles present on infold just dorsal to caudal process; 1 bristle present on infold between edge of caudal process and dorsal end of ridge; infold of caudal processes of both left and right valves similar.

Selvage: Wide lamellar prolongation with fringe present on selvage of anterodorsal, anterior, and ventral margins of valves, becoming narrower and bare in vicinity of caudal process and along posterior margin. Selvage divided at inner end of incisur, and also by small bristle at outer edge of caudal process (see detail on Figure 6b).

Central Adductor Muscle Attachments: Consisting of 14 or more individual ovoid attachments.

Size: USNM 158258, length 1.46 mm, height 1.06 mm; USNM 158259, length 1.42 mm, height 1.13 mm.

First Antenna (Figure 6c): 1st joint bare. 2nd joint with 2 spinous bristles (1 dorsal, 1 lateral), a few dorsal hairs, and lateral hairs forming row near distal margin. 3rd and 4th joints fused; short 3rd joint with 3 spinous bristles (2 dorsal, 1 ventral); long 4th joint with 3 spinous bristles (2 ventral, 1 dorsal). Sensory bristle of long 5th joint with 3 small proximal filaments and minute process at tip. 6th joint minute, fused with 5th, with short spinous medial bristle. 7th joint: a-bristle spinous, slightly stouter than bristle of 6th joint; b-bristle about one and three-quarters length of a-bristle, bare except for spine at tip; c-bristle about same length as sensory bristle of 5th joint, with none or one minute proximal filament and spine at tip. 8th joint: d- and e-bristles bare with blunt tips reaching tip of c-bristle; f-bristle stout, slightly shorter than c-bristle, with spine at tip; g-bristle about same length as c-bristle, with 1 short proximal filament with 2 long hairs at tip; tip of g-bristle with minute spine.

Second Antenna: Protopodite bare. Endopodite single jointed, with 4 short anterior bristles and 1 minute bristle near middle of margin (Figures 6d,e, 7d). Exopodite: long 1st joint with short bent medial bristle on distal margin; bristle of 2nd joint reaching to about 7th joint, bare except for short, blunt, ventral spines near tip; bristles of joints 3–5 with stout ventral spines near middle followed by row of smaller blunt spines, no natatory hairs; bristles of joints 6–8 much longer than others, with natatory hairs, no spines; 9th joint with 6 bristles (3 long and 1 medium with natatory hairs; 2 minute, bare).

Mandible (Figure 6f,g): Coxale endite spinous with bifurcate tip (Figure 6g). Basale: medial side with 4 proximal bristles in ventral corner (2 short pectinate, 2 slender ringed); ventral margin with 1 long midbristle; dorsal margin with 3 bristles just distal to middle. 1st endopodial joint with medial spines and 2 short ventral bristles. 2nd endopodial joint with medial spines, 3 short proximal bristles on dorsal margin, 2 short terminal bristles on ventral margin, and stout terminal claw; small sclerotized process with minute bristle present medial to base of claw; ventral margin of terminal claw with proximal peg and serrate edge (tip of claw not prolonged). 3rd endopodial joint with stout terminal claw with teeth along inner edge (teeth not shown on illustrated limb), stout unringed bristle with teeth along ventral edge, 3 short ringed medial bristles near ventral base of claw, and 2 short hirsute lateral bristles (these being located lateral to terminal claw of 2nd joint).

Maxilla (Figure 6h): Endite I with 5 bristles (3 pectinate, 2 ringed, spinous); endite II with 2 pectinate bristles and 2 spinous bristles; endite III with 3 pectinate bristles, 2 or 3 distal ringed bristles, and 1 proximal ringed bristle. Precoxale and coxale with fringed dorsal margin; coxale with spinous dorsal bristle. Basale with 1 spinous dorsal bristle and 1 medial bristle (the latter could be on 1st endopodial joint). Exopodite with 2 bristles (1 about twice length of other). Endopodite: 1st joint with 1 alpha-bristle with faint marginal spines and 1 dorsal bristle with slightly stouter spines; 2nd joint with 2 stout pectinate clawlike bristles, 1 more slender pectinate bristle on inner edge, 1 pectinate ringed bristle on outer edge, and 2 spinous a-bristles.

Fifth Limb (Figure 7a): Epipodial appendage with 42 or 43 bristles. Endite I with 2 bristles; endites II and III obscure on specimen studied but each with about 6 bristles (not all shown on illustrated limb). Exopodite: 1st joint with main tooth consisting of smooth proximal peg followed by 3 stout teeth with secondary teeth; a bristle probably present just proximal to peg of main tooth but obscure on specimen studied; outer edge of joint with 1 proximal bristle. 2nd joint with large 3-lobed tooth (middle lobe with 1 small secondary tooth); posterior side with 1 small bristle near outer corner and 2 longer bristles near inner edge proximal to proximal lobe of tooth. 3rd joint with 2 bristles on outer lobe and 3 on inner lobe. 4th and 5th joints fused, with total of 5 bristles.

Sixth Limb (Figure 7b): Endite I with 2 bristles; endite II with 1 bristle; endites III and IV each with 2 long bristles; end joint with 3 anterior bristles on protuberance and 4 hirsute posterior bristles (anterior pair of these with short distal spines); 2 short spinous bristles present in place of epipodial appendage.

Seventh Limb: Each limb with 4 proximal bristles, 2 on each side, and 6 terminal bristles (not all shown on illustrated limb), 3 on each side; each bristle with up to 6 bells and distal marginal spines; terminus with opposing combs containing 3-pronged teeth (Figure 6i), one comb with 5 teeth, other with 3 (not all shown on illustrated limb).

Furca (Figure 7c): Each lamella with 4 stout primary claws followed by 2 small secondary claws; claw 1 with anterior distal hairs, both long and short posterior teeth and proximal medial hairs forming row; claws 2 and 3 with anterior distal hairs and posterior teeth much smaller than those of claw 1 (teeth of claws 1 and 2 not shown on illustrated lamella); long hairs on lamellae following claws and medially at bases of claws.

Bellonci Organ (Figures 6j, 7e): Elongate, bulbous near middle, with rounded tip.

Eyes: Medial eye tapering distally, with brown pigment (Figures 6j, 7e). Lateral eye not observed with certainty; if present, small with 3 ommatidia (Figure 6j).

Posterior of Body: Hirsute.

Upper Lip (Figure 7e): Consisting of rounded lobe.

Eggs: USNM 158258 with 4 eggs in marsupium and also several large unextruded eggs.

DESCRIPTION OF JUVENILE FEMALE (INSTAR III) (Figure 7f–i).—Carapace in general similar to that of adult female (Figure 7f); bristles of infold not studied.

Size: USNM 158265, length 0.96 mm, height 0.72 mm.

First Antenna: Not studied in detail, but general morphology similar to that of adult female.

Second Antenna: Endopodite similar to that of adult female but with only 2 anterior bristles and without minute midbristle (Figure 7g). Expodite: no bristles with natatory hairs, all fairly short; 9th joint with only 4 bristles (Figure 7h).

Mandible, Maxilla, 5th Limb: Not studied in detail, but general morphology similar to that of adult female.

Sixth Limb: Not studied in detail but with numerous bristles.

Seventh Limb (Figure 7i): Elongate, bare. (In the illustrated limb, the bristles of the 7th limb of instar IV are shown as dashed lines within the limb of instar III.)

Furca: Similar to that of adult female, with 4 stout claws followed by 2 weak claws.

Bellonci Organ: Elongate with short widening central part separated by sutures from the proximal and distal parts; distal part tapering slightly and then widening to broadly rounded tip.

Eyes: Lateral eyes not observed. Medial eye similar to that of adult female, with brown pigment.

Posterior of Body: Hirsute.

SUPPLEMENTARY DESCRIPTION OF ADULT MALE (Figures 8–10).—Carapace elongate with projecting rostrum and deep incisur forming almost right angle; well-developed caudal process with rounded tip (Figures 8, 10b).

Ornamentation: Each valve with horizontal ribs restricted to posterior half (Figure 8); upper rib more strongly developed than lower rib; posterior ends of each rib connected by sinuous vertical rib; vertical rib tending to be less well developed in middle part; small rib present near inner corner of incisur; faint low rib paralleling ventral margin. Anterior margin of rostrum with small scalloped edge (Figures 8, 9a). Long bristles present along anterior margin; shorter bristles along ventral margin. Shell weakly calcified; small fossae apparent only near ventral margin on specimen examined. Small process present near middle of linear posterodorsal margin; no processes on posterior margin.

Infold: Rostral infold with 8 long bristles forming row; 2 short bristles present near inner corner of incisur (Figure 9b); anteroventral infold with 8 bristles; middle part of ventral infold without bristles; 17 bristles forming row extending along posterior one-third of ventral infold, caudal infold, and posterior infold immediately dorsal to caudal process (one of the bristles on infold of caudal process located slightly posterior to other bristles of caudal infold, Figure 9c); caudal infold without ridge.

Selvage: Wide lamellar prolongation with fringe present on selvage of anterodorsal, anterior, and ventral margins of valves, becoming narrower and bare in vicinity of caudal process and along posterior margin. Selvage divided at inner end of incisur, and also by small bristle at outer edge of caudal process.

Size: USNM 158260, length 1.21 mm, height 0.76 mm; USNM 158261, length 1.24 mm, height 0.77 mm.

First Antenna (Figure 9d): 1st joint bare. 2nd joint spinous and with 2 bristles (1 dorsal, 1 lateral). 3rd joint small, with 3 bristles (2 dorsal, 1 ventral); medial side of joint much shorter than lateral side. 4th joint with few medial and lateral spines and 4 bristles (1 dorsal, 3 ventral). Sensory bristle of minute 5th joint with numerous proximal filaments and stem with minute spine at tip. Medial bristle of long 6th joint located near dorsal margin. 7th joint: a-bristle about same length as bristle of 6th joint, spinous; b-bristle stout, about 3 times length of a-bristle, with 2 marginal filaments near middle and minute spine at tip; c-bristle extremely long, with 11 short marginal filaments and bifurcate tip. 8th joint: d- and e-bristles bare with blunt tips reaching past tip of b-bristle; f-bristle similar to c-bristle; g-bristle longer than b-bristle, with 1 proximal filament having drawn out tip. (Left limb of USNM 158260 aberrant in having 2nd joint without lateral bristle, 3rd joint with 1 instead of 2 dorsal bristles, and 4th joint with 2 instead of 3 ventral bristles; right limb of USNM 158260 (Figure 9d) and both limbs of USNM 158261 with normal number of bristles.)

Second Antennae (Figure 9e): Protopodite bare. Endopodite 3-jointed: 1st joint with 5 short bristles (4 proximal, 1 distal); 2nd joint elongate with 2 spinous ventral bristles just distal to middle; 3rd joint elongate, reflexed, with 1 short proximal bristle, 2 small slender bristles near ridged tip. Exopodite: long 1st joint with spines forming rows along ventral margin, and small medial bristle on terminal margin; bristle of short 2nd joint reaching 6th joint, with pearl-like blunt spines forming about 7 groups along ventral margin; 3rd joint about same length as 1st joint; bristles of joints 3–8 long, with natatory hairs, no spines; 9th joint with 5 bristles (1 minute, bare, 1 medium length, and 3 long, all with natatory hairs); joints 2–8 with lateral spines forming row along distal margin (those on 2nd joint longer than others).

Mandible (Figure 9f): Coxale endite consisting of 2 minute spines. Basale: medial side spinous with 6 bristles near ventral margin; dorsal margin with 3 bristles (1 near middle, 2 distal). Exopodite well developed, hirsute distally. 1st endopodial joint with medial spines and 2 spinous ventral bristles. 2nd endopodial joint: medial side spinous; dorsal margin with 3 proximal bristles; ventral margin (or close to it) with 6 short distal bristles. End joint with 1 stout claw with ventral spines, and 5 slender bristles.

Maxilla (Figure 9g): Limb reduced. Endite I with 5 weakly developed bristles, mostly bare and unringed, and 1 bristle with long hairs; endite II with 5 weakly developed bristles with long marginal hairs; endite III with 1 proximal bristle and about 6 distal bristles. Coxale with dorsal fringe and 1 plumose dorsal bristle. Basale with 3 distal bristles, 2 ventral and 1 medial near dorsal margin. Exopodite with 2 hirsute bristles (1 about one-half length of other). Endopodite: 1st joint hirsute, with 1 short bare alpha-bristle and 1 longer hirsute beta-bristle; end joint with 7 weakly developed bristles (2 are stouter than others and only weakly ringed).

Fifth Limb (Figure 9h): Endite I with 3 small bristles; endite II with 4 small bristles; endite III with about 8 bristles. Exopodite: 1st joint with 2 long, unringed, bare, finger-like bristles, 1 short, unringed, bare bristle, and 2 ringed proximal bristles; 2nd joint with 2 short, unringed, bare bristles and 3 ringed bristles; inner lobe of 3rd joint with 3 relatively short bare bristles of equal length; outer lobe with 2 long, stout, hirsute bristles; 4th and 5th joints fused, with total of 4 bare ringed bristles. Epipodial appendage with 40 hirsute bristles.

Sixth Limb (Figure 9i,j): Endite I with 3 short bristles; endite II with 1 long and 1 short bristle; endite III with 1 long bristle; endite IV with 2 long bristles. End joint with 3 short spinous bristles on prominent projection, followed by 2 stout bristles with long proximal hairs and 2 stout bristles with long hairs from bases to tip of bristles. 2 bare bristles in place of epipodial appendage.

Seventh Limb (Figure 9k,l): 4 proximal bristles, 2 on each side, and 4 longer terminal bristles, 2 on each side; proximal bristles with 3 or 4 bells and distal marginal spines; terminal bristles with 5 or 6 bells and distal marginal spines. Terminus with opposing combs having about 3 spinous teeth (not all shown in Figure 9l).

Furca (Figure 9m): Similar to that of female, except teeth of claw 1 about same size.

Bellonci Organ (Figure 10c): Broadening near middle and then tapering to fairly broad non-attenuated pointed tip (tip not rounded).

Eyes (Figure 10c): Lateral eye pigmented black (number of ommatidia difficult to determine, but about 25, possibly more). Medial eye pigmented brown, about same size as lateral eye, without hairs.

Posterior of Body: Without hairs or spines.

Upper Lip (Figure 10c): Consisting of rounded lobe without hairs.

Genitalia (Figure 10a): Each copulatory appendage elongate with 3 terminal lobes, each with 2 or more small bristles; one of the lobes with sclerotized process.

SEXUAL DIMORPHISM1.—In addition to the usual sexual morphological differences in all species of Rutiderma, the tip of the bellonci organ of the male R. lomae tapers to a broad point, and is not widely rounded as on the female.

COMPARISON OF MALE DESCRIBED HEREIN AND THAT DESCRIBED BY JUDAY.—Juday (1907:141, pl. XIX: figs. 1, 2, 4–6) did not recognize that the specimens he referred to his new species Philomedes lomae were actually male rutidermatids. The relationship was clarified by Poulsen (1965:16). It is probable that Juday (1907) included more than 1 species (at least 2) in P. lomae. He illustrated (pl. XIX: fig. 3) the outline of the carapace of a juvenile much smaller than the carapace of the specimen he correctly identified as an adult male (pl. XIX: fig. 1). Because juvenile Rutidermatidae resemble the adult female rather than the adult male, the small specimen considered to be a juvenile by Juday is probably an adult male rutidermid and, possibly, not conspecific with the larger adult male. Presumably, the appendages Juday illustrated (pl. XIX: figs. 2, 4–6) and the species description (pl. 141) are from the larger specimen. Apparent differences between Juday's male and ours are as follows:

Morphological character Juday's male Our male

Calcification of carapace

strong weak

Length of carapace (mm)

1.3 1.21, 1.24

Vertical rib connecting posterior ends of upper and lower horizontal ribs on each valve

not mentioned present

Fossae or pits on valve surface

abundant sparse

Number of bristles on 9th joint of exopodite of 2nd antenna

2 5

Number of bristles near ventral margin of mandibular basale

4 6

Number of bristles (excluding claw) on end joint of mandible

3 5

Some of the apparent differences tabulated above could be the result of variation within the species, especially the degree of calcification of the carapace, the length of the carapace, and the abundance of surface fossae, which may be more visible on strongly calcified carapaces. Other differences could be the result of inaccurate observations by Juday. It is easy to overlook some of the small bristles on the basale and end joint of the mandible.

A major difference between the two specimens is the number of bristles on the 9th joint of the exopodite of the 2nd antenna (2 for Juday's specimen, 5 for ours). Except for Juday's specimen, males of the Rutidermatidae, for which the number of bristles on the 9th joint are known, have 5 or 6 bristles (3 long, 1 medium, 1 or 2 minute). Only the 1 or 2 minute bristles could be easily overlooked. Therefore, we have assumed that Juday (1907:142) either described an aberrant limb or was mistaken in the number of bristles on the 9th joint.

We did not examine specimens identified as Philomedes lomae by Hartmann (1956:230; 1957: 76) from the Pacific coast of El Salvador or from the coast of Chile (1962:171).

Rutiderma lomae (Juday, 1907)

Philomedes lomae Juday, 1907:141, 142 [syntypes not extant; female neotype: USNM, designated by Kornicker and Myers, 1981:10; neotype-locality: “33°34′15″N, 118°00′45″W”].—Müller, 1912:26, 31.—Skogsberg, 1920:380 [not in Philomedes].—Lucas, 1931:399 [mentions].—Poulsen, 1962:358, 395 [compares to Scleroconcha].—McKenzie, 1965:57 [mentions].—Poulsen, 1965:15–17, 22.

[?]Philomedes lomae.—Hartmann, 1956:230, 231, 247; 1957:60, 61, 76 table opposite p. 83 [identification of specimens from El Salvador needs verification].—Hartmann-Schröder and Hartmann, 1962:33, 34, 48.—Hartmann, 1962:171, 264 [identification of specimens from Chile needs verification].

Rutiderma lomae.—Kornicker and Myers, 1981:1–4, 10–18, 34, figs. 5–10 [designates neotype].

Not Philomedes lomae.—Kornicker, 1958:233, 234, figs. 46:7A,B, 52:A–E, 53:A–D, 86:A,E,I [= R. dinochelatum].

DISTRIBUTION.—Northeast Pacific: California, U.S.A. (locality data for Juday, 1907, in Michael and McEwen, 1915:133, 143): off San Diego, off Santa Catalina Island, and Oxnard; [?]El Salvador. [?]Southeast Pacific: Bay of Caldera, Chile.

HABITAT.—Planktonic, surface (Juday, 1907); benthic, sediment 9.8°C. [?]Benthic; upper sublittoral, shelly sand beach.

LIFE HISTORY AND ONTOGENY.—Male, female, juvenile female, 4 eggs.