ArticlePDF Available

Descriptions Of Skate Egg Cases (Chondrichthyes: Rajiformes: Rajoidei) From The Eastern North Pacific

Abstract and Figures

Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were identified and are here described. In addition, egg cases of two unidentified skate species were collected from very deep water off central and southern California, USA. Examples of egg cases for all species, except for two, were removed in utero in order to confirm their species specific identification. The egg cases of seven skate species, including egg cases from the two unidentified species, have not previously been described or illustrated from this region. Previous attempts to identify skate egg cases with their associated species have been inadequate. The ENP skate egg cases can broadly be classified into two main groups: those with broad lateral keels (> 10% maximum egg case width) and those with narrow lateral keels (< 10% maximum egg case width). Egg cases in the former group (with broad lateral keels) generally have a finely striated surface texture that is smooth to the touch. Those in the latter group (with narrow lateral keels), with one exception, tend to have a coarse surface texture, often with prickles, and are rough to the touch. A revised key to the skate egg cases from the ENP is provided.
Content may be subject to copyright.
Accepted by M. de Carvalho: 1 Nov. 2006; published: 18 Jan. 2007 1
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2007 · Magnolia Press
Zootaxa 1393: 118 (2007)
www.mapress.com/zootaxa/
Descriptions of skate egg cases (Chondrichthyes: Rajiformes: Rajoidei) from the
eastern North Pacific
DAVID A. EBERT & CHANTE D. DAVIS
Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA. 95039, U.S.A.; ph.
831-771-4427; fax 831-632-4403. E-mail: debert@mlml.clastate.edu
Abstract
Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were identified and are here
described. In addition, egg cases of two unidentified skate species were collected from very deep water off central and
southern California, USA. Examples of egg cases for all species, except for two, were removed in utero in order to con-
firm their species specific identification. The egg cases of seven skate species, including egg cases from the two uniden-
tified species, have not previously been described or illustrated from this region. Previous attempts to identify skate egg
cases with their associated species have been inadequate. The ENP skate egg cases can broadly be classified into two
main groups: those with broad lateral keels (> 10% maximum egg case width) and those with narrow lateral keels (<
10% maximum egg case width). Egg cases in the former group (with broad lateral keels) generally have a finely striated
surface texture that is smooth to the touch. Those in the latter group (with narrow lateral keels), with one exception, tend
to have a coarse surface texture, often with prickles, and are rough to the touch. A revised key to the skate egg cases from
the ENP is provided.
Key words: Amblyraja, Bathyraja, Raja, skate egg cases, eastern North Pacific
Introduction
Skates are the most diverse elasmobranch group, comprising over 20% of the known species for this group of
fishes (Compagno, 2005). These flatsharks, as they are sometimes called, occur from nearshore to the outer
continental shelf in cool temperate to polar waters and in the deepsea. The number of species within this elas-
mobranch group is likely to increase as taxonomic issues are resolved and new species are identified. One
method by which skate species may be distinguished from each other is by their egg case morphology. The
egg case morphology of each skate species, like the claspers on males, is unique to that species and can be
used in its identification (Ishiyama, 1958a).
The use of skate egg cases as a taxonomic tool for species identification and to study their phylogenetic
relationships is well known (Ishiyama, 1958a, b; Hubbs & Ishiyama, 1968; Ishiyama & Hubbs, 1968). How-
ever, identification of species specific egg cases is often wanting as researchers often assume, incorrectly, that
an egg case came from a certain species since the species in question is known to occur in a particular area.
Often this assumption does not account for the possibility of non-resident species migrating into an area,
depositing their egg cases, and then leaving. Therefore, proper identification of egg cases associated with the
correct species can be erroneous if they are not removed from the adult female in utero.
Since 2002, researchers from the Pacific Shark Research Center (PSRC), Moss Landing Marine Laborato-
ries (MLML), have been studying the life history and systematics of eastern North Pacific (ENP) skates,
including those found in the Bering Sea (Ebert, 2005) and Gulf of Alaska. As part of this research program we
EBERT & DAVIS
2 · Zootaxa 1393 © 2007 Magnolia Press
have been removing egg cases in utero from females that have been necropsied. Cox (1963) described the egg
cases of several elasmobranchs, including those of six skates, from California waters and provided a key to
their identification. However, Cox (1963) did not indicate how he was able to identify the species he associ-
ated with each egg case. Upon examination of the photographs figured by Cox (1963) it appears that some of
these egg cases were collected in situ and were not removed from the female. Thus, creating some uncertainty
as to whether the egg cases he figured actually came from the species he associated them with. In fact, upon
review we have determined that several of the egg cases depicted by Cox (1963) were incorrectly identified
and or inadequately described. Furthermore, since this work was published five additional skate species have
been recorded from ENP waters. Therefore, given the improved state of knowledge on skate distribution and
occurrence in ENP waters (Ebert, 2003), and the usefulness of skate egg cases as a taxonomic identification
tool we present a new and revised description, and key, to the egg cases of ENP skates.
Materials and methods
The study area ranged between Cape Flattery, Washington (47°20’ N, 125°25’ W) and southern California
(32°40’ N 117°33’ W). Skates collected during survey cruises conducted by the NOAA Fisheries Southwest
Fisheries Science Center (SWFSC), Santa Cruz, California laboratory and the Northwest Fisheries Science
Center (NWFSC), Newport, Oregon laboratory were subsequently returned to MLML and necropsied. Egg
cases found in utero during necropsies were removed and fixed in 10% buffered formalin, and subsequently
preserved in 70% ethanol. Egg cases were also collected, after deposition, from specimens maintained in
holding tanks at the Monterey Bay Aquarium (MBA). Additionally, a near-term embryo removed from one
egg case (CAS 25617) and six unidentified egg cases collected in situ from very deepwater by a remote oper-
ated vehicle (ROV) were also examined. Egg cases from each species examined were subsequently deposited
in collections at the California Academy of Sciences (CAS), MLML, or Scripps Institute of Oceanography
(SIO).
Egg cases were described and measured following Ishiyama and Ishihara (1977) with some modifications
and additions. The skate egg case or capsule is usually rectangular in shape with a horny process at each cor-
ner with a more or less loosely closed, concave, anterior margin through which the embryo emerges at hatch-
ing in most cases and a more or less flattened posterior margin that is tightly fused. The dorsal and ventral
surfaces are more or less convex, with the dorsal surface being more domed than the ventral. Lengthwise the
sides are generally keeled, or flanged, from very narrow to very broad. Lateral keels on some species may
extend onto anterior and or posterior horns. The horns vary from very short, less than the case length, to very
long, more than two times case length, with the horns tapering, becoming filamentous, thread-like, or flatten-
ing towards the tips. Some egg cases may have fibrous sheets of byssus-like material present on the surface of
the egg case structure. This fibrous covering may be variably thin and loose to rather thick and tight fitting.
The lateral margins of some cases, depending on the species, may have attachment fibers. The location of
attachment fibers, if present, varies between species. The dorsal and or ventral surfaces of the case can be
smooth and glossy or covered by longitudinal ridges or striations that can be straight or undulated and smooth
or papillose and can give the surface a rough to velvety texture or matte appearance.
Egg case measurements and abbreviations include (Figure 1): Egg case length (ECL), used as an indepen-
dent variable for proportional dimensions of other egg case structures and measured longitudinally between
the anterior and posterior apron borders; anterior border width (ABW) is the distance between the bases of the
anterior horns; anterior horn length (AHL) is the distance from the horn base to the tips; posterior border
width (PBW) is the distance between the bases of the posterior horns; posterior horn length (PHL) is the dis-
tance from the posterior horn base to the tips; maximum case width (MAW), the transverse width of the case
in its lateral plane at its widest part of the case; minimum case width (MIW), the transverse width of the case
Zootaxa 1393 © 2007 Magnolia Press · 3
DESCRIPTIONS OF SKATE EGG CASES
in its lateral plane at its narrowest part of the case; lateral keel width (LKW) is the distance from the capsule
keel junction to the keel edge.
FIGURE 1. Skate egg case terminology and measurements.
Egg case descriptions
Amblyraja badia (Garman, 1899)
Remarks: Originally described from off Panama, this species has subsequently been reported from the ENP,
north to the Bering Sea and westward to Japanese waters (Ebert, 2003). This is the only ENP species for
which we have been unable to positively identify egg cases. Garman (1899) noted two egg cases that were
dredged up during the Albatross expedition of 1891, the same expedition in which the holotype of A. badia
was collected. However, the egg cases were collected at a different, although nearby, location from where the
A. badia was caught. Therefore, it is uncertain whether these egg cases belong to that species. The egg cases
were described by Garman (1899) as “covered with fine villi or pile, in longitudinal series, though harsh to the
touch gives the appearance of a soft rich black velvet”. We attempted to locate these egg cases that were
accessioned at the Museum of Comparative Zoology (MCZ 1009 and 1010), Harvard University for further
examination, but they appear to have been lost (Ann Holmes, curator, MCZ, pers. comm.).
Bathyraja abyssicola (Gilbert, 1896)
Description: The egg cases of Bathyraja abyssicola (Figure 2) are large, 108 to 111 mm in length, with MAW
about 67–69% of ECL. Egg case surface texture coarse and very rough to the touch, striated, the surface is
EBERT & DAVIS
4 · Zootaxa 1393 © 2007 Magnolia Press
irregular and with rasp-like denticles. LKW is very narrow, < 5% of MAW and with a distinct groove between
the lateral keel and case proper. This groove is not present in any other ENP skate egg case. Lateral keels
extend onto horns and are also present on inner horns. Anterior apron border of egg case broad and concave,
anterior horns more robust than posteriors at base, becoming flattened and thread-like at tips. Posterior apron
is nearly straight, broad, and transverse, about 10 mm wider than anterior apron. Posterior horns long, about
two times length of anteriors and about 1.2 times ECL, curved inwards, each tapering to a thread-like tip.
Attachment fibers present, originating on lateral keel near the junction of exterior base of posterior horns and
case. Egg cases removed from a single specimen was a light golden brown in color.
Remarks: Bathyraja abyssicola is a large, deepwater species usually found on the continental slope
between 362 and 2906 m, although most records of its capture have come from > 1,000 m deep (Zorzi &
Anderson, 1988). It is considered to be a rare species, but recent deepwater surveys along the ENP continen-
tal slope have revealed this skate to be more common than previously thought (unpublished data). To the best
of our knowledge this is the first confirmed record and description of the egg case of this species.
Material examined: CAS 224336, 141.0 cm TL, west of Alexander Island, Washington (47.4935 N, -
125.5185 W), 1428 m, 24 August 2004.
FIGURE 2. Egg case of Bathyraja abyssicola. Scale bar 20 mm.
Bathyraja aleutica (Gilbert, 1896)
Description: The egg cases of Bathyraja aleutica (Figure 3) are very large, >120 mm in length, with MAW
about 73–76% of ECL. Egg case surface very coarse, striated, and with long anteriorly directed prickles giv-
ing it a velvety texture. Lateral keels very narrow, about 6–7% of MAW. Attachment fibers present, originat-
ing near base of posterior horns. Anterior apron border broad and concave, similar in width to the posterior.
Zootaxa 1393 © 2007 Magnolia Press · 5
DESCRIPTIONS OF SKATE EGG CASES
Anterior horns relatively short, about 60–80% of ECL, curved inwards, tapering towards tips, becoming thin
and filamentous. Posterior apron straight, broad, transverse, posterior horns longer than anteriors and about
90% or more length of egg case, tapering towards tips with tendrils coiling towards filamentous tips. Color
after preservation a golden brown, lighter along lateral keels.
Remarks: A common species in the Bering Sea and Gulf of Alaska its southern range is now known to
extend into northern California (Hoff, 2002; Ebert, 2003).
Material examined: CAS 224337, 138.0 cm TL, eastern Bering Sea (56.1972 N, 169.7457 W), 242 m, 17
June 2002; MLML uncatalogued, 136.0 cm TL, eastern Bering Sea (60.3806 N, -178.6524 W), 295 m, 29
June 2002; MLML uncatalogued, 134.9.0 cm TL, eastern Bering Sea (60.3806 N, -178.6524 W), 295 m, 29
June 2002.
FIGURE 3. Egg case of Bathyraja aleutica. Scale bar 20 mm.
Bathyraja kincaidii (Garman, 1908)
Description: The egg cases of Bathyraja kincaidii (Figure 4) are very small, 50 to 66 mm in length, with
MAW about 76–91% of ECL. Egg case dorsal surface covered with thin layer of fine fibers, ventral surface
with either a very thin fibrous layer or without. Surface of egg case beneath fibrous layer finely striated with
longitudinal rows and smooth to the touch. LKW very broad, about 14–19% of MAW, and extending length of
case including outer edge of horns; a keel is present along inner edge of the posterior horns, but absent on
anterior horns. Attachment fibers present along entire edge of lateral keels. Anterior apron border broad, con-
cave; anterior horns about 50–80% ECL, and flattening towards tips becoming thread-like. Anterior horns
curve perpendicular to dorsal aspect of egg case and hooking rearward. Posterior apron border broad, nearly
EBERT & DAVIS
6 · Zootaxa 1393 © 2007 Magnolia Press
straight, transverse, about 3–9 mm wider than anterior apron. Posterior horns moderately long, length similar
to ECL, curved inward to median aspect of egg case, flattening toward tips, and becoming thread-like. Egg
cases from preserved specimens range from a light to dark brown except for lateral keels which are usually
lighter brown to gold colored.
Remarks: The egg case described and depicted by Cox (1963) for this species appears to be consistent
with our findings in that it is a small egg case, nearly as wide as long, has attachment fibers present, and prom-
inent lateral keels. Our description differs in that we found the egg cases of B. kincaidii to be smooth to the
touch while Cox (1963) described the surface texture as moderately rough. Since we do not know the location
of where those egg cases were collected or their eventual deposition we are unable to directly compare our
egg cases with those of Cox (1963). It may be that the slight differences we observed in our samples are
within the normal range of variability. Bathyraja kincaidii, however, may represent a species complex of two
or more distinct, sympatrically occurring species ranging between the Gulf of Alaska and California. There-
fore, careful examination of egg cases from throughout this region may help elucidate this question.
Material examined: CAS 224339, 48.2 cm TL, off Davenport, California (ca 36.5368 N, -122.1445 W),
170 m, 3 August 2002; MLML BK0209-6, 50.1 cm TL, off Davenport, California, (ca 36.5368 N, -122.1445
W), 181 m, 21 September 2002; MLML BK0210-7: 50.0 cm TL, off Davenport, California (ca 36.5596 N, -
122.2220 W), 311 m, 24 October 2003; MLML BK121503-4-1, 53.5 cm TL, off central Oregon (45.7385 N,
-124.3820 W), 153 m, 13 September 2003; MLML BK102403-02-3, 56.9 cm TL, off northern California
(40.2276 N, -124.5422 W), 360 m, 5 October 2003.
FIGURE 4. Egg case of Bathyraja kincaidii. Scale bar 20 mm.
Bathyraja microtrachys (Osburn & Nichols, 1916)
Description: The egg cases of Bathyraja microtrachys (Figure 5) are small, 79 to 81 mm in length, with
MAW about 63–64% of ECL. The egg case surface is coarsely striated, with irregular rasp-like denticles,
making its texture very rough to the touch. LKW is very narrow, < 5% of MAW and not extending onto horns.
Anterior apron border of egg case broad, deeply concave, anterior horns robust at base, but flattening towards
Zootaxa 1393 © 2007 Magnolia Press · 7
DESCRIPTIONS OF SKATE EGG CASES
tips and becoming thread-like, tips curving dorsally and back towards egg case. Posterior apron is nearly
straight, broad, and transverse, width similar to anterior. Posterior horns robust at base, very long, about 66%
length of anteriors and about 1.1 times ECL, curved inwards, each tapering to a thread-like tip. Attachment
fibers present, extending length of lateral keel. Egg cases removed from a single preserved specimen were a
dark golden brown.
Remarks: This is the first confirmed record, and description, of the egg case of this species. The egg
cases described here were removed in utero from a 62.8 cm TL specimen (SIO 8780). Cox (1963: Figure 7)
suggested that the egg case he described and illustrated as B. trachura may eventually prove to be this species.
However, the term embryo that was removed from that egg case (CAS 25617), and described below, appear to
be that of B. spinossisima (Ebert, 2005).
Until recently this species had been considered a synonym of B. trachura (Ebert, 2003). However, exami-
nation of the holotypes of B. microtrachys and B. trachura by the senior author, plus additional material con-
firm that these species are distinct. To further separate these two species their egg cases can be used to
distinguish them from each other. The egg case of B. microtrachys differs from that of B. trachura in that the
former has very narrow lateral keels and a coarsely striated surface texture that is rough to the touch, while the
latter has very broad lateral keels and is smooth to the touch.
Bathyraja microtrachys is one of the deepest occurring skate species, known to occur down to at least
3,100 m (unpublished data). The shallowest record of this species is the holotype known from 1,995 m. All
other records of it have come from depths greater than 2,000 m.
Material examined: SIO 8780, 62.8 cm TL, off Waldport, Oregon (44.4130 N, -125.3410 W), 2850 m, 6
February 1987.
FIGURE 5. Egg case of Bathyraja microtrachys. Scale bar 20 mm.
EBERT & DAVIS
8 · Zootaxa 1393 © 2007 Magnolia Press
Bathyraja spinossisima (Beebe & Tee-Van, 1941)
Description: The egg case of Bathyraja spinossisima (Figure 6) is large, about 92 mm in length excluding
horns, with MAW of 73% ECL. The surface is weakly striated, with both dorsal and ventral surfaces being
plush to the touch. LKW is very narrow, about 3% of ECL, and extending onto horns. Attachment fibers are
absent. Anterior apron broadly concaved, curving perpendicular from horizontal plane of egg case, and nar-
rowing at tips. Posterior apron about 7 mm wider than anterior, nearly straight, broad, and transverse. Poste-
rior horns about two-thirds ECL, curved inwards, and narrowing to tips. Egg case color after preservation is a
uniform plum brown.
FIGURE 6. Egg case of Bathyraja spinossisima. Scale bar 20 mm.
Remarks: A single egg case originally identified by Follett (1952: Figure 1) as that of Bathyraja trachura
based on a near term embryo found inside was subsequently described by Cox (1963). This egg case has also
been inaccurately illustrated in the literature as being that of B. trachura (Eschmeyer et al., 1983; Mecklen-
berg et al., 2002; Ebert, 2003). However, Ebert (2005) examined this egg case and embryo (CAS 25617), and
compared it with egg cases removed in utero from B. trachura, and concluded that the embryo fit that of the
holotype of B. spinossisima. Miller and Lea (1972) first reported the occurrence of B. spinossisma from the
ENP based on this specimen, but without explanation, only giving the museum catalogue number where it is
deposited. At the time Follett (1952) and Cox (1963) identified this egg case as B. trachura, B. spinossisima
had not been reported from the ENP.
The holotype of B. spinossisima is an embryo that had been removed from an egg case collected in very
deepwater off Panama. Interestingly, a pair of egg cases also collected off Panama, in very deepwater, by Gar-
man (1899) in some aspects appears to fit the description of this species. Unfortunately, the egg case for the
Zootaxa 1393 © 2007 Magnolia Press · 9
DESCRIPTIONS OF SKATE EGG CASES
holotype of B. spinossisima and Garman’s egg cases have been lost.
Material examined: CAS 25617, egg case with embryo present, Mulberry Seamount, 78 km west of
Point Montara, central California (37.2630 N, -123.2842 W), 1400 to 2000 m, 8 February 1950.
Bathyraja trachura (Gilbert, 1892)
Description: The egg cases of Bathyraja trachura (Figure 7) are small, 62 to 78 mm in length, with MAW
about 77–97% of ECL. Egg case surfaces with prominent longitudinal striations and smooth to the touch.
LKW very broad, striated, about 15–20% of MAW, and extending length of case including outer edge of
horns; an inner keel is present along edge of both anterior and posterior horns. Attachment fibers present
along lateral keels, originating about outer base of posterior horns. Anterior apron border broad and concave,
anterior horns about one-half ECL, horns curved inwards toward median plane of egg case, tips curling
towards ventral aspect of egg case, and flattening towards tips. Posterior apron nearly straight, broad, trans-
verse, and up to 7 mm wider than posterior apron. Posterior horn length variable, 0.8 to 1.4 times ECL, horns
curved inwards to median plane of egg case, and flattening towards tips. A distinct crossbar originating mid-
way along posterior horns was present on six of nine egg case pairs. One pair had evidence of an incompletely
formed crossbar and two had no evidence. This crossbar is unique among ENP skates. Color after preserva-
tion a dark brown becoming a light golden brown on keels.
FIGURE 7. Egg case of Bathyraja trachura. Arrow denotes crossbar (broken). Scale bar 20 mm.
Remarks: Ebert (2005) described the egg case of this species, based on material from the eastern Bering
Sea, and commented that the egg case described and figured by Cox (1963) as B. trachura was not that spe-
cies. The egg case figured by Cox (1963: Figure 5), and captioned as Raja stellulata, is actually that of B. tra-
EBERT & DAVIS
10 · Zootaxa 1393 © 2007 Magnolia Press
chura.
The posterior horns on some B. trachura egg cases, 75% in this study, have a unique crossbar that is not
present on any of the other skate egg cases that we have examined from this region (Figure 7). In some
instances the crossbar was broken or missing. Whether the crossbar remains intact, or for how long, once the
egg case is deposited on the seafloor is unknown as we did not obtain any egg cases of this species in situ.
Material examined: CAS 224340, 79.1 cm TL, off central Oregon (45.3862 N, -125.5707 W) 924 m, 3
September 2004; MLML BT 100804-1-6, 86.5 cm TL, off central Oregon (45.3862 N, -125.5771 W), 929 m,
3 September 2004; MLML BT 110504-2-3, 66.3 cm TL, off northern California (37.0453 N, -120.3272 W),
1101 m, 12 October 2004; MLML BT 031105-04, 789 mm TL, off northern California (38.5142 N, -122.6890
W), 320 m, 17 February 2005; MLML BT 011205-19, 78.7 cm TL, off central California (36.2502 N, -
122.0718 W), 366 m, 6 January 2005.
FIGURE 8. Egg case of Raja binoculata. Scale bar 20 mm.
Raja binoculata Girard, 1854
Description: The egg cases of Raja binoculata (Figure 8) are perhaps the most distinctive skate egg case
found in the ENP. The dorsal surface is convex with two prominent ridges; no other known ENP skate egg
case has these ridges. These are very large egg cases, 210 to 280 mm in length from anterior to posterior apron
borders, with a MAW about 52% of ECL. Egg case surface very smooth, without striations or fibrous cover-
ing. Under magnification the surface appears smooth and without striations. LKW very broad, about 30–33%
of MAW, narrowing to about 4–6% at MIW, and extending length of egg case including outer edge of horns;
keels also along inner edge of horns. Attachment fibers not present. Anterior apron border broad, slightly
concave, fraying along edge, anterior horns about 28–30% of ECL, curving dorsally, with tips flattening and
Zootaxa 1393 © 2007 Magnolia Press · 11
DESCRIPTIONS OF SKATE EGG CASES
curling toward egg case. Posterior apron broad, transverse, and fraying at edge, its width less than that of
anterior. Posterior horns short, stout, about 32–38% ECL, horn base width about 24% of horn length; horns
curved, and flattening towards tips. Lateral keels extend beyond horn length. Color of egg case after preserva-
tion a dark brown to greenish brown.
Remarks: The egg case of R. binoculata is perhaps the largest egg case of any known skate species, with
a maximum known length, excluding horns, exceeding 300 mm (Hitz, 1964). Raja binoculata is the only
skate species, except for R. pulchra Liu, 1932, known to have multiple embryos per egg case. These skates
may have 2–7 embryos, with an average of 3–4 per egg case (Hitz, 1964). The Japanese endemic R. pulchra
is known to have 1–5 embryos per egg case (Ishiyama, 1958b). Although it has not been studied in detail,
increased fecundity, due to multiple oviparity, in these species may have significant conservation implica-
tions. Raja binoculata is known to produce up to 360 egg cases per year in captivity (Kevin Lewand,
Monterey Bay Aquarium, pers. comm.). Assuming an average of 3.5 embryos per egg case the annual fecun-
dity may reach 1,260 neonates, or more, making it one of the most fecund of all elasmobranchs.
Material examined: CAS 224341, northern California (38.033 N, -123.1237 W), 78 m, 24 September
2004; MLML RB 102403-4-06, 146.7 cm TL, central California (36.4076 N, -121.5276 W), 69 m, 22 October
2003; MLML EX 58, southern Oregon (44.311 N,
-124.257 W), 71 m, 4 September 2004.
FIGURE 9. Egg case of Raja inornata. Scale bar 20 mm.
Raja inornata Jordan & Gilbert, 1881
Description: The egg cases of Raja inornata (Figure 9) are very small, 68 to 73 mm in length from anterior to
posterior apron borders, with MAW about 73–77% of ECL. Egg case surfaces finely striated, without fibrous
EBERT & DAVIS
12 · Zootaxa 1393 © 2007 Magnolia Press
covering, and very smooth to the touch. LKW is very broad, about 17–25% of MAW, and extending length of
case including outer edge of horns; keels absent or very minute along inner horn edge. Attachment fibers not
present. Anterior apron border broad, concave, anterior horns about 34–52% of ECL, curling ventrally, and
flattening and hook-like towards tips. Posterior apron nearly straight, broad, transverse, and about 4–6 mm
wider than anterior apron width. Posterior horns relatively short, about one-half ECL, curved, and flattening
towards tips. Preserved egg case color dark brown becoming lighter on keels.
Remarks: The present description of this egg case differs from the original description by Cox (1963) in
that we did not observe attachment fibers to be present in any of the specimens examined. Also, Cox (1963)
did not comment on the broad lateral keels of these egg cases which we found to be a good characteristic for
separating between similar looking egg cases, but from different species.
Material examined: Ten egg cases all deposited between July and August 2005 by R. inornata specimens
held at the Monterey Bay Aquarium. Two of these egg cases accessioned as CAS 224342.
FIGURE 10. Egg case of Raja rhina. Scale bar 20 mm.
Raja rhina Jordan & Gilbert, 1880
Description: The egg cases of Raja rhina (Figure 10) are large, 93 to 102 mm in length, with MAW about 62–
70% of ECL. Egg case dorsal surface covered with dense woven-like fibers, ventral surface with either a thin
fibrous layer or without. Surface of egg case beneath fibrous layer is finely striated and smooth to the touch.
LKW broad, about 13–19% of MAW, and extending length of case including outer edge of horns; an inner
keel is present along edge of both anterior and posterior horns. Attachment fibers present along lateral keels,
originating about midway along egg case. Anterior apron border broad and concave, anterior horns also about
one-half ECL, and flattening towards tips, becoming thread-like. Posterior apron nearly straight, broad, trans-
Zootaxa 1393 © 2007 Magnolia Press · 13
DESCRIPTIONS OF SKATE EGG CASES
verse, and about 1–7 mm wider than anterior apron width. Posterior horns relatively short, about one-half
ECL, curved, flattening towards tips, and becoming thread-like. Color from fresh specimens a uniform golden
brown.
Remarks: DeLacy and Chapman (1935), who first described these egg cases, found that they may range
up to 130 mm in length, making it one of the larger skate egg cases found in the ENP. Although Cox (1963)
stated that these egg cases were very similar to that of R. inornata we found them to be quite distinct. The egg
case of R. inornata is much smaller, lacks a fibrous covering, and has a broader lateral keel, without attach-
ment fibers, relative to the maximum egg case width.
Material examined: CAS 224343, 74.8 cm TL, off central California (36.4701 N, -121.5312 W), 488 m,
10 December 2002; MLML RR121602-3-11, 85.6 cm TL, off central California (36.4574 N, -121.5469 W),
186 m, 16 December 2002; MLML RR121602-1-04, 73.1 cm TL, off central California (36.4536 N, -
121.5382 W), 91 m, 16 December 2002.
Raja stellulata Jordan & Gilbert, 1880
Description: The egg cases of Raja stellulata (Figure 11) are large, 91 to 92 mm in length, with MAW about
66–70 % of ECL. The egg case is covered with dense fibers on the dorsal surface, thinner on the ventral. The
outer fibrous covering appears as an intricately woven sheath with a wool-like texture. Beneath these fibers
the egg case is smooth, with very fine longitudinal striations. The LKW is narrow, < 10% of ECL, and not
extending onto horns. Attachment fibers are present along lateral keels. Anterior apron border broad and con-
cave, anterior horns become flattened towards the tips and hook inwards. Posterior apron nearly straight,
broad, transverse, and about 1–2 mm wider than anterior apron width. The posterior horns are about 5 to 6 mm
longer than anteriors, curved, conical and tapering, becoming flattened, but without filamentous tips. The tips
are hook-shaped at the ends. Color after preservation a uniform brown.
FIGURE 11. Egg case of Raja stellulata. Scale bar 20 mm.
EBERT & DAVIS
14 · Zootaxa 1393 © 2007 Magnolia Press
Remarks: The egg case of R. stellulata has not been previously described. The egg case figured by Cox
(1963: figure 5) as this species is actually that of B. trachura. The egg case of R. rhina and R. stellulata are
somewhat similar, but can be easily distinguished by the narrower lateral keels present on the latter. Also, the
attachment fibers on R. stellulata extend the length of the lateral keels, while the fibers on R. rhina egg cases
originate midway along lateral keel of egg case.
Material examined: CAS 224344, 73.2 cm TL, off Davenport, California (36.9235 N, -122.2275 W), 88
m, 16 April 2004.
FIGURE 12. a. Egg case of unidentified deepsea skate species “A”. Scale bar 20 mm; b. Egg case of unidentified deep-
sea skate species “A” collected in situ by the MBARI ROV Tiburon; c. Egg case of unidentified deepsea skate species
“A” nested among other egg cases in situ.
Unidentified deepsea skate egg case “A”
Description: The egg cases of this unidentified species (Figure 12a) are very large, 188 to 198 mm in length,
with MAW about 58–62% of ECL. The surface is finely striated, smooth to the touch, and without a fibrous
outer layer. Surface under magnification appear as shallow, wavy, concave striations. The LKW is very broad,
about 14% of MAW, and folds over itself. Attachment fibers are absent. Anterior apron border broad and con-
cave, anterior horns more robust than posterior, inner and out keels present, horn length 53–57% ECL, curv-
ing dorsally relative to aspect of egg case, and flattening to tips and curling. Posterior apron border almost
A B
C
Zootaxa 1393 © 2007 Magnolia Press · 15
DESCRIPTIONS OF SKATE EGG CASES
straight, transverse, thinning along edge, and slightly less than width of anterior apron. Posterior horns 58–
67% of ECL, curving medially and ventrally, slightly longer than anterior, flattening to tips, and with outer
and inner keels present along edges. Color in situ a light yellowish, but becoming a bronze to greenish brown
after preservation (Figure 12b).
Remarks: Three examples of these large unidentified skate egg cases were collected by the Monterey Bay
Aquarium Research Institute (MBARI) remote operated vehicle (ROV) Tiburon off San Diego, California at a
depth of 1,820 m (Figure 12b). These three egg cases were nested among some rocks in what appears to be a
nursery area as numerous egg cases were observed on this rough rocky relief substrate (Figure 12c). An adult
male and adult female B. spinossisima were observed to swim past the ROV and it is possible that these egg
cases may be of that species. However, these egg cases are unlike the egg case that we have tentatively identi-
fied as B. spinossisima in that these are not plush to the touch. The only known species that we do not have an
example of its egg case is A. badia. Given the high degree of endemism found in skates and the remote off-
shore location of where these egg cases were observed they may represent an otherwise unknown species.
Additional examples of these egg cases, perhaps some with developing embryos, will shed light on their
proper identification.
Material examined: CAS 224345, three egg cases, collected by MBARI remote operated vehicle Tiburon
in situ, off San Diego, California (32.9635 N, -121.0484 W), 1820 m, 29 April 2004.
FIGURE 13. a. Egg case of unidentified deepsea skate species “B”. Scale bar 20 mm; b. Egg case of unidentified deep-
sea skate species “B” collected in situ by the MBARI ROV Tiburon; c. Egg case of unidentified deepsea skate species
“B” in situ on the Davidson Seamount.
A B
C
EBERT & DAVIS
16 · Zootaxa 1393 © 2007 Magnolia Press
Unidentified deepsea skate egg case “B”
Description: The egg cases of this unidentified species (Figure 13a) are large, 96 to 103 mm in length, with
MAW about 79–82% of ECL. The surface is finely striated, smooth to the touch, and without a fibrous outer
layer. The LKW is very broad, about 12–14% of MAW, and extending length of case, tapering off along outer
edge of horns. Attachment fibers are absent. Anterior apron border broad and concave, anterior horns curling
ventrally, becoming flattened and hook-like towards tips, horn length about 47–54% of ECL. Posterior apron
border nearly straight, broad, transverse, thinning along edge, and about similar in width to anterior apron.
Posterior horns relatively long, 87–96% of ECL, flattening to a filamentous tip. Color in situ is a dark brown
on the egg case proper, but becoming lighter along lateral keel and aprons (Figure 13b).
Remarks: Three examples of these large unidentified skate egg cases were collected by MBARI ROV
Tiburon on the Davidson Seamount, an inactive submarine volcano located approximately 120 km southwest
of Monterey, California at a depth of between 1,310 and 1,319 m (Figure 13b). These three egg cases, col-
lected on two separate dives, were on each occasion found to be nested near deepsea corals and gorgonians in
apparent nursery areas as numerous additional egg cases were observed on each dive where they were col-
lected (Figure 13c). One of the egg cases, upon dissection, was found to contain a small developing embryo of
an unknown species of skate. A female A. badia was observed swimming in the vicinity of where these egg
cases were collected.
Material examined: Three egg cases collected by MBARI remote operated vehicle Tiburon in situ; CAS
224346, Davidson Seamount, California (35.7211360 N, -122.7235850 W), 1312 m, 27 January 2006. CAS
224347, Davidson Seamount, California (35.721340 N, -122.7234670 W), 1310 m, 27 January 2006. CAS
224348, Davidson Seamount, California (350 43.5688 N, 1220 43.6120 W), 1319 m, bottom temperature 2.9
0C, 18 May 2002.
Key to the Eastern North Pacific Skate Egg Cases
The ENP skate egg cases can be broadly classified into two main groups: those with broad lateral keels (> 10% MAW)
and those with narrow lateral keels (< 10% MAW). Egg cases in the former group (with broad lateral keels) generally
have a surface texture that is finely striated and smooth to the touch. Those in the latter group (with narrow lateral keels)
tend to have an egg case surface that is coarse in texture, often with prickles, and is rough to the touch. The only excep-
tion in this group is the egg case of R. stellulata that differs in having a finely striated surface beneath a thick fibrous cov-
ering.
The key below includes all of the known valid skate species, plus two unidentified species, known to occur from the
eastern Gulf of Alaska (ca 590 N, 1380 W) southwards to the California Mexico border (ca 320 N 1170 W). The validity of
two species, B. obtusa (Gill & Townsend, 1897) and B. rosispina (Gill & Townsend, 1897) is questionable and the occur-
rence of the Alaska Skate, B. parmifera (Bean, 1881), in the eastern Gulf of Alaska has not been confirmed from this
region. The egg cases of B. parmifera, if found to occur in this area, are quite distinct. A description and illustration of
the egg case of B. parmifera can be found in Ebert (2005).
1a. Lateral keel width broad, > 10% of maximum egg case width...................................................................2
1b. Lateral keel width narrow, < 10% of maximum egg case width.................................................................8
2a. Egg case very large, > 180 mm....................................................................................................................3
2b. Egg case usually smaller, < 100 mm........................................................................................................... 4
3a. Dorsal surface distinct with two convex ridges; horns < 50% ECL; keel width very broad > 30% of MAW
..............................................................................................................................................Raja binoculata
3b. Dorsal surface without convex ridges; horns > 50% ECL; keel width broad about 15 % of MAW.............
........................................................................................................Unidentified deepsea skate species “A”
4a. Attachment fibers absent.............................................................................................................................5
Zootaxa 1393 © 2007 Magnolia Press · 17
DESCRIPTIONS OF SKATE EGG CASES
4b. Attachment fibers present............................................................................................................................ 6
5a. Lateral keel width very broad, 17–25% of maximum egg case width; posterior horns about one-half egg
case length...............................................................................................................................Raja inornata
5b. Lateral keel width broad, 12–14% of maximum egg case width; posterior horns about equal to egg case
length .............................................................................................. Unidentified deepsea skate species “B”
6a. Fibrous covering absent..................................................................................................Bathyraja trachura
6b. Fibrous covering present..............................................................................................................................7
7a. Fibrous covering thick, woven-like..............................................................................................Raja rhina
7b. Fibrous covering thin......................................................................................................Bathyraja kincaidii
8a. Attachment fibers present............................................................................................................................9
8b. Attachment fibers absent ..........................................................................................Bathyraja spinossisima
9a. Egg case with fibrous covering...............................................................................................Raja stellulata
9b. Egg case without fibrous covering............................................................................................................. 10
10a. Egg case very large, > 100 mm................................................................................................................ 11
10b. Egg case smaller, < 100 mm ..................................................................................Bathyraja mircotrachys
11a. Surface coarse, striated, with long anteriorly directed prickles giving it a velvety texture, and without a
distinct groove demarcating lateral keel and egg case.....................................................Bathyraja aleutica
11b. Surface very coarse, without anteriorly directed prickles, with a distinct groove demarcating lateral keel
and egg case................................................................................................................. Bathyraja abyssicola
Acknowledgements
We thank the following people for assistance on various aspects of this project: Lewis Barnett, Joe Bizzarro,
Greg Cailliet, Brooke Flammang, Diane Haas, Colleena Perez, Heather Robinson, and Wade Smith (Pacific
Shark Research Center, Moss Landing Marine Laboratories), Kelly Clendenning (Menlo High School), Don
Pearson, John Fields, and E.J. Dick (NOAA Fisheries SWFSC, Santa Cruz Lab), Keith Bosley, Erica Fruh,
Dan Kamakawa, Aimee Keller, and Victor Simon (NOAA Fisheries NWFSC), Manny Ezcurra, Scott Green-
wald, and Ed Seidel (Monterey Bay Aquarium), Andrew DeVogelaere (Monterey Bay National Marine Sanc-
tuary) and Lori Chaney, David Clague, and Linda Kuhnz (Monterey Bay Aquarium Research Institute). Haul
station location data provided by Beth Horness (NOAA NWFSC West Coast Groundfish Survey Database).
Funding for this research was provided by NOAA/NMFS to the National Shark Research Consortium and
Pacific Shark Research Center, and in part by the National Sea Grant College Program of the U.S. Department
of Commerce’s National Oceanic and Atmospheric Administration under NOAA Grant no.
NA04OAR4170038, project number R/F-199, through the California Sea Grant College Program and in part
by the California State Resources Agency.
References
Bean, T.H. (1881) Descriptions of new fishes from Alaska and Siberia. Proceedings of the United States National
Museum, 4, 144159.
Beebe, W. & Tee-Van, J. (1941) Eastern Pacific expeditions of the New York Zoological Society. XXVIII. Fishes from
the tropical eastern Pacific. Part 3. Rays, mantas, and chimaeras. Zoologica, 26, 245280.
Compagno, L.J.V. (2005) Checklist of living chondrichthyes. Editor W.C. Hamlett. In: Reproductive Biology and Phy-
logeny of Chondrichthyes: Sharks, Batoids, and Chimaeras, Chapter 16, 503548.
Cox, K.W. (1963) Egg cases of some elasmobranchs and a cyclostome from Californian waters.California Fish &
Game, 49, 271289.
Delacy, A.C. & Chapman, W.M. (1935) Notes on some elasmobranchs of Puget Sound, with descriptions of their egg
EBERT & DAVIS
18 · Zootaxa 1393 © 2007 Magnolia Press
cases. Copeia, 2, 6367.
Ebert, D.A. (2003) The sharks, rays and chimaeras of California. University California Press, 284 pp.
Ebert, D.A. (2005) Reproductive biology of skates, Bathyraja (Ishiyama), along the eastern Bering Sea continental slope.
Journal of Fish Biology, 66, 618649.
Eschmeyer, W.N., Herald, E.S., & Hammond, H. (1983) A field guide to Pacific coast fishes of North America. Houghton
Mifflin Co., Field Guide (28), 336 pp.
Follett, W.I. (1952) Annotated list of fishes obtained by the California Academy of Sciences during six cruises of the
U.S.S. Mulberry conducted by the United States Navy off central California in 1949 and 1950. Proceedings of the
California Academy of Sciences, 27(16), 399432.
Garman, S. (1899) Reports on an exploration off the west coasts of Mexico, Central and South America, and off the Gal-
apagos Islands, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer “Albatross,” during 1891,
Lieut. Commander Z.L. Tanner, U.S.N., Commanding. XXVI. The Fishes. Memoirs of the Museum of Comparative
Zoology, 24, 2044.
Garman, S. (1908) New Plagiostoma and Chismopnea. Bulletin of the Museum of Comparative Zoology, 51(9), 251256.
Gilbert, C.H. (1892) Description of thirty-four new species of fishes collected in 1888 and 1889, principally among the
Santa Barbara Islands and in the Gulf of California. Proceedings of the United States National Museum, 14, 539
566.
Gilbert, C.H. (1896) Report on the fishes collected in Bering Sea and the North Pacific during the summer of 1890. The
ichthyological collections of the steamer Albatross during the years 1890 and 1891. Report of the U.S. Commis-
sioner of Fish and Fisheries for 1893, 393476.
Gill, T. & Townsend, C.H. (1897) Diagnosis of new species of fishes found in Bering Sea. Proceedings of the Biological
Society of Washington, 11, 231234.
Girard, C.F. (1854) Characteristics of some cartilaginous fishes of the Pacific coast of North America. Proceedings of the
Academy of Natural Sciences Philadelphia, 7, 196197.
Hitz, C.R. (1964) Observations on egg cases of the big skate (Raja binoculata Girard) found in Oregon coastal waters.
Journal of the Fisheries Research Board of Canada, 21(4), 851854.
Hoff, G.R. (2002) New records of the Aleutian skate, Bathyraja aleutica from northern California. California Fish &
Game, 88(3), 145148.
Hubbs, C.L. & Ishiyama, R. (1968) Methods for the taxonomic study and description of skates (Rajidae). Copeia, 3,
483491.
Ishiyama, R. (1958a) Observations on the egg-capsules of the skates of the Family Rajidae, found in Japan and its adja-
cent waters. Bulletin of the Museum of Comparative Zoology Harvard College, 118(1), 124.
Ishiyama, R. (1958b) Studies on the Rajid fishes (Rajidae) found in the waters around Japan. Journal of Shimonoseki
College of Fisheries, 7(2, 3), 193394.
Ishiyama, R. & Hubbs, C.L. (1968) Bathyraja, a genus of Pacific skates (Rajidae) regarded as phyletically distinct from
the Atlantic genus Breviraja. Copeia 2, 407410.
Ishiyama, R. & Ishihara, H. (1977) Five new species of skates in the genus Bathyraja from the western North Pacific,
with reference to their interspecific relationships. Japanese Journal of Ichthyology, 24(2), 7190.
Jordan, D.S. & Gilbert, C.H. (1880) Description of a new species of ray (Raia stellulata) from Monterey,
California. Proceedings of the United States National Museum, 3, 133135.
Jordan, D.S. & Gilbert, C.H. (1880) Description of a new species of ray, Raia rhina, from the coast of
California. Proceedings of the United States National Museum, 3, 251253.
Jordan, D.S. & Gilbert, C.H. (1881) Note on Raia inornata. Proceedings of the United States National Museum, 4, 73
74.
Liu, F.H. (1932) The elasmobranchiate fishes of north China. Scientific Report to National Tsing Hua University Peiping
(B), 1(5), 133177.
Mecklenburg, C.W., Mecklenburg, T.A., & Thorsteinson, L.K. (2002) Fishes of Alaska. American Fisheries Society,
1037 pp.
Miller, D.J. & Lea, R.N. (1972) Guide to the coastal marine fishes of California. California Fish & Game, Fish Bulletin,
157, 235 pp.
Osburn, R.C. & Nichols, J.T. (1916) Shore fishes collected by the 'Albatross' expedition in Lower California with
descriptions of new species. Bulletin of the American Museum of Natural History, 35(16), 139181.
Zorzi, G.D. & Anderson, M.E. (1988) Records of the deep-sea skates, Raja (Amblyraja) badia Garman, 1899 and
Bathyraja abyssicola (Gilbert, 1896) in the Eastern North Pacific, with a new key to California skates. California
Fish & Game, 74(2), 87105.
... Egg capsules were described and measured based on previous studies (Ebert and Davis 2007;Concha et al. 2009;Mabragaña et al. 2011;Soto-López et al. 2020). Morphological characteristics such as color, texture, capsule shape, lateral and ventral description of the capsule (i.e., asymmetric, symmetric, convex, flat, striated, smooth, glossy), and thickness and shape of the horns were considered. ...
... Within members of the family Rajidae, R. velezi egg capsule presents more resemblance to the genera Beringraja, Raja, and Rajella than to species belonging to the genus Rostroraja (Ebert and Davis 2007;Ebert et al. 2008;Ishihara et al. 2012). The egg's capsules of Rostroraja alba described in Ebert et al. (2008) and Ishihara et al. (2012) differ from R. velezi capsule description. ...
... The egg's capsules of Rostroraja alba described in Ebert et al. (2008) and Ishihara et al. (2012) differ from R. velezi capsule description. These are larger (15 cm, ECL) usually 1.5 times wider than long and have longer posterior horns (> ECL) and broader lateral keels (11.5% MAW) (Ebert and Davis 2007); also, these capsules are coarsely striated with rough surfaces and tape-like horns. For Rostroraja eglanteria, capsules are slightly more similar to R. velezi capsules, not only in the oblong capsule shape, longitudinal striations, and curved horns (Breder and Nichols 1937;Breder and Rosen 1966), but also in the size (ECL, 5.1-8.9 ...
Article
Nine egg capsules of the Rasptail Skate (Rostroraja velezi) were collected from their southernmost distributional range in northern Peruvian waters for their description. Egg capsules had a glossy black or dark brown color, with a subrectangular shape, slightly wider at posterior end than at anterior end. Egg capsules when observed under a stereoscope revealed a finely striated surface. Egg capsules ranged from 6.8 to 7.7 cm in length, 4.9 to 6.2 cm in maximum width, and 4.2 to 5.9 cm in minimum width. Anterior horn length was shorter than posterior horn length (0.29% vs. 0.58%). Differences in egg capsule surface and size were observed when compared to capsules of R. velezi from Baja California, Mexico, possibly due to differences in environmental conditions since individuals sampled belong to different marine provinces. Our results represent the second study to describe egg capsules for this species and the first in the Tropical Eastern Pacific marine province.
... (Love et al., 2008; Hoff, 2008 Hoff, , 2010 Hunt et al., 2011). Given the greater interest in the identification of elasmobranch spawning and nursery grounds, there has been a concurrent increase in studies describing the eggcases of the various species, including those in the Mediterranean Sea (Mancusi & Serena, 2015), Southwest Atlantic (Oddone & Vooren, 2008; Mabragaña et al., 2011; Concha et al., 2009 Concha et al., , 2010 Concha et al., , 2012 Concha et al., , 2013), Northeast Pacific (Ebert & Davis, 2007), South African waters (Ebert et al., 2006Ebert et al., , 2008) and off Australia (Treloar et al., 2006; Bustamante et al., 2013). Whilst there were earlier descriptions of the eggcases of many of the Northeast Atlantic chondrichthyans (Le Danois, 1913; Clark, 1922; Lacourt, 1979; Bor, 1998), an updated account and key is provided here in order to incorporate recent changes in the taxonomy of European skates (Iglésias et al., 2010), and also to provide more quantitative data on the sizes of eggcases. ...
... Samples of intact and authenticated specimens were measured to provide more detailed quantitative information to augment descriptions. The general structure of the eggcase (Figure 1) is based on previous descriptions by Ishiyama (1950Ishiyama ( , 1958) and Ebert & Davis (2007), albeit with some modifications. The following terminology is used in the descriptions of the eggcases: Eggcase (including horns): The eggcase generally refers to the entire specimen, including both anterior and posterior horns. ...
Article
Updated descriptions and measurements for the eggcases of 10 rajiform and three scyliorhinid species occurring in the shelf seas around the British Isles are given, based on museum material, specimens collected during the 'Great Eggcase Hunt' (a Shark Trust recording project), and specimens obtained from fishery surveys. Quantitative data are given for Amblyraja radiata (n = 94), Dipturus batis (n = 24), D. cf. intermedia (n = 33), Leucoraja naevus (n = 94), Raja brachyura (n = 53), R. clavata (n = 52), R. microocellata (n = 57), R. montagui (n = 52), R. undulata (n = 52), Rostroraja alba (n = 5), Galeus melastomus (n = 7), Scyliorhinus canicula (n = 52) and S. stellaris (n = 58). An updated key for the identification of elasmobranch eggcases is provided, incorporating recent changes in skate taxonomy.
... Specifically, on the northern part of the Argentine Continental Shelf (nACS) from 36°S to 41°S, between 50 and 200 m depth, the presence of 12 species of skates, the elephant fish Callorhinchus callorynchus (Linnaeus, 1758) and the narrowmouthed catshark Schroederichthys bivius (Müller & Henle, 1838) has been recorded so far (Cousseau et al. 2007; Mabragaña 2007; Díaz de Astarloa et al. 2008; Sánchez et al. 2009; Cousseau & Perrotta 2013). Chondrichthyan egg cases have morphological features that make them species-specific (Ishiyama 1958; Ebert & Davis 2007; Mabragaña et al. 2011; Ishihara et al. 2012). Their morphology provides information about phylogenetic interrelationships between both recent and fossil oviparous chondrichthyans (Fischer et al. 2014). ...
Article
The aim of this paper was to explore egg-laying areas of oviparous chondrichthyans occurring in the northern part of the Southwest Atlantic Ocean (36°S–41°S) at between 50 and 200 metres depth and the Mar del Plata Canyon (from 200 to 3447 m). A total of 515 capsules were collected corresponding to 10 species. Four species accounted for 87.6% of the total catch: Psammobatis normani, Bathyraja macloviana, Amblyraja doellojuradoi and Bathyraja brachyurops. The remaining corresponded to Schroederichthys bivius, Psammobatis rudis, Zearaja chilensis, Bathyraja albomaculata, Psammobatis lentiginosa and Bathyraja sp. Most hauls were monospecific and relatively few hauls contained four or five species (southern part of the area, in sites located at 75 and 94–105 m depth). No egg capsules were recorded between 1712 m and 3447 m. Highest densities (>3000 capsules/km²) were mainly found between 39°46.2′ and 40°29.9′S from 85 to 105 m and they were also recorded near the Mar del Plata Canyon at 37°59.7′S and at 852 m. The highest value recorded was 12,326 capsules/km² (located at 40°18.9′S and 85.4 m). The highest densities for each of the most abundant species are discussed. The finding of high densities of egg cases near the Argentine shelf-break front indicates that many skate species use this area as a nursery site. The egg-laying areas explored here are the first reported sites of this kind in the Southwest Atlantic Ocean. Recognizing and protecting egg-laying habitats may be important steps to a long-term conservation of oviparous chondrichthyan populations.
... When present, the number of embryos and the sex (if able to be determined by visual inspection of presence/absence of claspers), presence of internal or external yolk, uterus (left or right), total length (± 0.1 mm) and mass (± 0.1 g) of each embryo were noted. When present, the number of egg cases and uterus (left or right) and mass (± 0.1 g) were noted and egg case length (L EC ) (± 0.1 mm) taken following Ebert and Davis [33]. All egg cases were labelled, frozen and retained. ...
Article
Full-text available
The deepwater chondrichthyan fauna of the Great Barrier Reef is poorly known and life history information is required to enable their effective management as they are inherently vulnerable to exploitation. The chondrichthyan bycatch from the deepwater eastern king prawn fishery at the Swain Reefs in the southern Great Barrier Reef was examined to determine the species present and provide information on their life histories. In all, 1533 individuals were collected from 11 deepwater chondrichthyan species, with the Argus skate Dipturus polyommata, piked spurdog Squalus megalops and pale spotted catshark Asymbolus pallidus the most commonly caught. All but one species is endemic to Australia with five species restricted to waters offshore from Queensland. The extent of life history information available for each species varied but the life history traits across all species were characteristic of deep water chondrichthyans with relatively large length at maturity, small litters and low ovarian fecundity; all indicative of low biological productivity. However, variability among these traits and spatial and bathymetric distributions of the species suggests differing degrees of resilience to fishing pressure. To ensure the sustainability of these bycatch species, monitoring of their catches in the deepwater eastern king prawn fishery is recommended.
... 8(a)] and ranged in length from 41⋅5 to 58⋅8 mm L EC and mass from 3⋅5 to 8⋅3 g. There were no visible embryos within any of the egg cases and it was assumed that there was one embryo per egg case, as is the case for all skates (except two Raja species) (Ebert &amp; Davis, 2007). Length at hatching was deduced as 89–111 mm L T from 12 specimens which were considered newly hatched as they had internal yolk sacs, but no prey items in their stomachs. ...
Article
Two Australian endemic elasmobranchs, the Argus skate Dipturus polyommata and the eastern spotted gummy shark Mustelus walkeri, were collected from the by-catch of a prawn Melicertus plebejus trawl fishery off Queensland. Age and growth parameters were estimated from growth band counts in vertebral sections of 220 D. polyommata and 44 M. walkeri. Dipturus polyommata males and females had an observed maximum age of 10 years and reached maximum sizes of 369 and 371 mm total length (LT), respectively. Mustelus walkeri lived longer, with the oldest female aged 16 years and measuring 1050 mm stretched total length (LST), and oldest male aged 9 years and 805 mm LST. Dipturus polyommata grew relatively fast with a von Bertalanffy growth completion parameter of k = 0·208 year−1 with males reaching maturity at 4·0 years (c. 278 mm LT) and females at 5·1 years (c. 305 mm LT). Mustelus walkeri grew more slowly with k = 0·033 year−1 with males estimated to mature at 7–9 years (670–805 mm LST) and females at 10–14 years (833–1012 mm LST). Length at birth inferred from neonate D. polyommata was 89–111 mm LT while for M. walkeri it was estimated to be 273 LST based on the value of L0 from the von Bertalanffy growth model. Both species appeared to have continuous reproductive cycles and low fecundity with an average ovarian fecundity of eight follicles for D. polyommata and a litter size of five to seven pups for M. walkeri. Based on these life-history traits, D. polyommata is more resilient to fishing pressure than M. walkeri.
... 8(a)] and ranged in length from 41⋅5 to 58⋅8 mm L EC and mass from 3⋅5 to 8⋅3 g. There were no visible embryos within any of the egg cases and it was assumed that there was one embryo per egg case, as is the case for all skates (except two Raja species) (Ebert & Davis, 2007). Length at hatching was deduced as 89–111 mm L T from 12 specimens which were considered newly hatched as they had internal yolk sacs, but no prey items in their stomachs. ...
Article
Full-text available
Deep-water sharks have low biological productivity and are vulnerable to exploitation with species-specific regional life history required to enable effective management. The present study describes the life history of two squalids collected from Australia: (1) the piked spurdog (Squalus megalops) from the tropical Great Barrier Reef; and (2) the Philippine spurdog (S. montalbani) from New South Wales. Maximum observed ages for males and females were 18 and 25 years for S. megalops and 28 and 27 years for S. montalbani. Multiple growth models were all well supported and indicated very slow growth rates for both species. The tropical S. megalops population was smaller and older at maturity than previously reported temperate populations. Males were mature at 352-mm stretched total length (L ST) and 12.6 years, whereas females were mature at 422 mm L ST and 19.1 years. Squalus montalbani males were mature at 700 mm L ST and 21.8 years, whereas females were mature at 800 mm L ST and 26 years. Fecundity was lower for S. megalops than S. montalbani with two to three compared with nine to 16 embryos. Both species have a conservative life history, although in the event of overfishing the longer-lived, later-maturing and deeper-dwelling S. montalbani is likely to take longer to recover than S. megalops.
... Among oviparous species, most rajids show single oviparity (i.e., one embryo per egg capsule), with one egg being deposited at a time from each oviduct, usually in pairs during the spawning season (Musick and Ellis, 2005). The few exceptions include Raja pulchra (Ebert and Davis, 2007) and R. binoculata (Ebert et al., 2008), which deposit multiple embryos in each egg capsule. The gross morphology of the OG varies among species, but in general it consists of two similar dorso-ventral halves surrounded by connective tissue (Knight et al., 1996 ). ...
Article
We studied the morphology and histology of the oviducal gland (OG) in the brown ray (Raja miraletus) and the long-nosed skate (Dipturus oxyrinchus) to understand its functional role in the reproductive strategy of these species. The external morphology of the gland was similar in both species, with lateral extensions like those found in other members of the Rajidae. Microscopic analysis showed a similar internal organization in both species. Immature and developing glands did not react to histochemical techniques. On reaching maturity, the OG had the largest width due to an increase in the production of secretory materials. In both species, the club zone of the gland showed a strong reaction to Periodic acid-Schiff (PAS) and alcian blue (AB) stains, indicating production of neutral and sulfated acid mucins. The secretory material produced by the papillary zone varied greatly between the two species. Both displayed tubular glands similar to those observed in the club zone, but in D. oxyrinchus the region near the lumen was intensely PAS+, whereas the last row of tubules of the brown ray stained intensely for a mixture of neutral and sulfated mucins. The baffle zone was the most conspicuous and extensive segment of all OGs, and it did not react to PAS/AB. The terminal zone, which is responsible for production of hair filaments, differed between the two species in terms of composition and organization of serous and mucous glands. This difference probably is related to the different substrates in which they release the egg capsules. Individual sperm detected in the brown ray baffle lamellae could be the result of a recent mating, whereas their presence in the deep recesses of the baffle and in the terminal zone of the long-nosed skate might indicate sperm storage. J. Morphol., 2015. © 2015 Wiley Periodicals, Inc.
Article
Full-text available
En diciembre de 2005 se recolectaron cápsulas ovígeras de dos hembras de Psammobatis scobina, capturadas en Caleta Montemar, Chile central (32º57’S-71º33’W). La superficie de las cápsulas fue suave y finamente estriada, de color café y translúcida. Además presentaron la típica forma de barril. La longitud central fluctuó entre 35,25 mm y 38,45 mm y su ancho varió entre 25,91 mm y 27,94 mm. La cara dorsal es convexa con respecto a la ventral. Los cuernos anteriores son más cortos que los posteriores, se orientan hacia el interior y se estrechan hasta adquirir forma de zarcillos hacia las puntas. Los zarcillos laterales resultaron ser un carácter diagnóstico entre especies del mismo género en Chile. Esta es la primera descripción de las cápsulas ovígeras de P. scobina, especie endémica para las costas del sur de Sudamérica.
Article
The oviposition rate in captive Sympterygia bonapartii was reported. In a year period one female laid a total of 152 egg cases at a rate of 0.4 egg cases per day and a second one laid a total of 200 egg cases at a rate of 0.5 egg cases per day.
Article
A total of 1357 specimens of Alaska skate Bathyraja parmifera were collected in the eastern Bering Sea by fisheries observers and during scientific groundfish surveys from 2003 to 2005. Male and female gonads were examined for maturity stage and seasonal reproductive timing. Based on seasonal reproductive data, including the occurrence of egg cases, ovum size, ovum number, shell-gland width and gonado-somatic index, this species appears to reproduce continually throughout the year. Potential effects of maternal size upon the size and number of mature oocytes were also investigated, with total length having a significant, although weak, influence on both. Morphology of a single intersexual individual encountered during the collection period is also described. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
Article
Full-text available
Five new species of skates.Bathyraja caeluronigricans, B.notoroensis.B.mactrlata. B.lindbergi, and B.minispinosa were described from the western North Pacific.Bathyraja matsubarai (Ishiyama, 1952) was revised and redescribed.not only because this species is closely related to the above species hut because one of the paratvpes of this species was newly erected as B.notoroensis.Relationships of the six species were discussed morphologically and zoogeographically .
Article
Recent studies show the need for defined methods of systematically studying and describing skates. Disc width is proposed as the basis for proportional measurements of various parts of the disc, tail, fins, and head; of distances between certain spines; and of dimensions of ocellus. Methods are proposed for measurements of the cranium and the egg-capsule, and for counting vertebrae, pelvic radials, tooth rows, numbers of spines, rows of alar and malar hooks, and turns in the valvular intestine. Suggestions are given for description of spines, of prickles in various specific regions, of coloration, of cranium, of clasper, and of egg-capsules.