Chondrichthyan egg cases from the south-west Atlantic Ocean

Abstract

Egg cases of 21 oviparous chondrichthyan species from the south-west Atlantic Ocean are described and compared. The catshark Schroederichthys bivius has a cigar-shaped egg case with curled tendrils only at the posterior end. Egg cases of the elephant fish Callorhinchus callorynchus are spindle-shaped with anterior and posterior tubular extensions and lateral flanges. The skate Amblyraja doellojuradoi presents medium-sized egg cases (71 mm in length) with a lateral keel extending to the first portion of the horns. The endemic skate species of the genus Atlantoraja have medium to large egg cases (69-104 mm in length) and present relatively large posterior horns. Egg cases of the genus Bathyraja have a medium size, 75-98 mm in length, and are characterized by a very similar morphology, a relatively smooth to rough surface case and posterior horns strongly curved inwards. Egg cases of the genera Dipturus and Zearaja are very large, 115-230 mm in length, and have a well-developed posterior apron. Despite the problematical identification of skates at species level, the egg capsules of the endemic genus Psammobatis are easily diagnosed; the capsules are small (25-53 mm in length), those of Psammobatis rutrum being the smallest known to date in the world. Egg cases of Rioraja agassizi have a medium size, 61-68 mm in length, relatively straight sides, a smooth surface and silky attachment fibres placed in the lateral keel next to each horn. Those of the genus Sympterygia are small to medium sized, 51-86 mm in length, and display the thickest lateral keel and the longest posterior horns among the skates of the world. Egg cases can be a useful tool for identifying species and egg-laying areas; therefore, a provisional key for the south-west Atlantic Ocean chondrichthyan capsules is presented.

Full text

Journal of Fish Biology (2011) 79, 1261–1290
doi:10.1111/j.1095-8649.2011.03111.x, available online at wileyonlinelibrary.com
Chondrichthyan egg cases from the south-west Atlantic
Ocean
E. Mabraga ˜
na*†‡, D. E. Figueroa*, L. B. Scenna*†,J.M.Díazde
Astarloa*†, J. H. Colonello§and G. Delpiani*†
*Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, Universidad
Nacional de Mar del Plata, Funes 3350, B7602AYL Mar del Plata, Rep´ublica Argentina,
†Consejo Nacional de Investigaciones Científica y T´ecnicas (CONICET), Buenos Aires,
Rep´ublica Argentina and §Pesquerías de Condrictios, Instituto Nacional de Investigaci´on y
Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo N◦1, Escollera Norte, B7602HSA
Mar del Plata, Rep´ublica Argentina
(Received 5 February 2010, Accepted 25 August 2011)
Egg cases of 21 oviparous chondrichthyan species from the south-west Atlantic Ocean are described
and compared. The catshark Schroederichthys bivius has a cigar-shaped egg case with curled tendrils
only at the posterior end. Egg cases of the elephant fish Callorhinchus callorynchus are spindle-
shaped with anterior and posterior tubular extensions and lateral flanges. The skate Amblyraja
doellojuradoi presents medium-sized egg cases (71 mm in length) with a lateral keel extend-
ing to the first portion of the horns. The endemic skate species of the genus Atlantoraja have
medium to large egg cases (69– 104 mm in length) and present relatively large posterior horns.
Egg cases of the genus Bathyraja have a medium size, 75–98 mm in length, and are charac-
terized by a very similar morphology, a relatively smooth to rough surface case and posterior
horns strongly curved inwards. Egg cases of the genera Dipturus and Zearaja are very large,
115– 230 mm in length, and have a well-developed posterior apron. Despite the problematical
identification of skates at species level, the egg capsules of the endemic genus Psammobatis are
easily diagnosed; the capsules are small (25– 53 mm in length), those of Psammobatis rutrum being
the smallest known to date in the world. Egg cases of Rioraja agassizi have a medium size,
61– 68 mm in length, relatively straight sides, a smooth surface and silky attachment fibres placed
in the lateral keel next to each horn. Those of the genus Sympterygia are small to medium sized,
51– 86 mm in length, and display the thickest lateral keel and the longest posterior horns among
the skates of the world. Egg cases can be a useful tool for identifying species and egg-laying
areas; therefore, a provisional key for the south-west Atlantic Ocean chondrichthyan capsules is
presented. ©2011 The Authors
Journal of Fish Biology ©2011 The Fisheries Society of the British Isles
Key words: Argentina; capsules; identification key; skates; sharks.
INTRODUCTION
Chondrichthyans display a great variety of reproductive modes, from oviparity to
different kinds of viviparism (from yolk-sac viviparity, the dominant mode of repro-
duction in Chondrichthyes, to placental viviparity in some sharks) (Hamlett, 2005).
‡Author to whom correspondence should be addressed. Tel.: +54 223 4751107; email: emabraga@
mdp.edu.ar
1261
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1262 E. MABRAGA ˜
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Oviparity is characterized by the production of fertilized eggs, encapsulated in a
structurally complex capsule, that develop and hatch externally. Oviparity is found
in all skate and holocephalan species, and in some sharks (Hamlett, 2005).
Oviparous chondrichthyans in the Argentine continental shelf are represented by 24
species of skates, the elephant fish Callorhinchus callorynchus (L. 1758) and the nar-
rowmouthed catshark Schroederichthys bivius (M¨
uller & Henle 1838) (Menni et al.,
1984; Cousseau et al., 2007; Diaz de Astarloa et al., 2008). Two other oviparous
sharks, the polkadot catshark Scyliorhinus besnardi (Springer & Sadowsky 1970)
and the freckled catshark Scyliorhinus haeckeli (Miranda Ribeiro 1907) occasionally
occur in the area (Menni & Lucifora, 2007).
In spite of the fact that chondrichthyan catches in the south-west Atlantic Ocean
have considerably increased in recent years (Massa et al., 2004; Cousseau et al.,
2007), several aspects of their reproductive biology are yet unknown. Egg cases
have been described for some skates in the south-western Atlantic Ocean (Braccini
& Chiaramonte, 2002; Mabraga˜
na et al., 2002; Oddone & Vooren, 2002, 2005, 2008;
Mabraga˜
na & Cousseau, 2004; Oddone et al., 2004, 2006; Oddone, 2005; San Martín
et al., 2005; Ruocco et al., 2006; Mabraga˜
na, 2007; Concha et al., 2009). Two of
these works include an identification key based on egg-case morphology of species
of Psammobatis G¨
unther 1870 (Mabraga˜
na, 2007), and of species of Atlantoraja
Menni 1872, Sympterygia M¨
uller & Henle 1837 and Rioraja Whitley 1939 (Oddone
& Vooren, 2008); however, a comparative study including capsules morphology and
morphometry of all chondricthyan genera occurring in the area is lacking.
Egg case morphology is species specific (Ishiyama, 1958; Ebert, 2005; Ebert &
Davis, 2007) and is used as a taxonomic and ecological tool. Variations in egg case
morphology between species may also indicate differences in the habitat of where
they are deposited (Ebert et al., 2006). The identification of demersal egg cases
furnish valuable information concerning the distribution and reproductive biology
of species (e.g. breeding season, fecundity and fertility, incubation period and egg
laying and nursery areas). This information is crucial for the conservation of these
species. Given the importance of egg case identification, the aim of this study was to
provide the description and diagnostic characteristics of specific egg cases occurring
in the Argentine continental shelf.
MATERIALS AND METHODS
Oviparous species were collected from bottom-trawl surveys carried out by the Instituto
Nacional de Investigaci´
on y Desarrollo Pesquero, (INIDEP; National Institute of Fishery
Research and Development, Argentina). The survey area included the south-west Atlantic
Ocean between 34◦and 55◦S, from the coastline to 200 m depth (Fig. 1). For egg case
identification associated with the correct species, capsules were removed from females in the
uterus, except those of C. callorynchus, which were obtained from the sea bed. Addition-
ally, egg cases were taken with a dredge close to banks of Patagonian scallop Zygochlamys
patagonica. Egg cases were also collected, after deposition, from specimens in captivity in
the Museo del Mar aquariums. Egg cases were fixed and preserved in 10% formalin, and
deposited in the collection at Laboratorio de Ictiología de la Universidad Nacional de Mar
del Plata, Mar del Plata, Argentina.
Eight morphometric characteristics were recorded following standard methods (Hubbs &
Ishiyama, 1968; Ishiyama & Ishihara, 1977; Ebert & Davis, 2007). In addition, keel thickness
and straight distance from the anterior apron margin to the curvature of the anterior horn
©2011 The Authors
Journal of Fish Biology ©2011 The Fisheries Society of the British Isles, Journal of Fish Biology 2011, 79, 1261 –1290

CHONDRICHTHYAN EGG CASES 1263
70° 68° 66° 64° 62° 60° 58° 56° 54° 52° 50°
54°
52°
50°
48°
46°
44°
42°
40°
38°
36°
34°
Uruguay
Argentina
100 m
50 m
200 m
Fig. 1. Study area showing the sites where females bearing egg cases were found: ,Amblyraja doellojuradoi ;
,Atlantoraja castelnaui ; , Atlantoraja cyclophora; , Atlantoraja platana ; , Bathyraja albomacu-
lata;,Bathyraja brachyurops ; , Bathyraja macloviana; , Bathyraja magellanica ; , Callorhinchus
callorhynchus;,Zearaja chilensis ; , Dipturus trachyderma; , Psammobatis bergi ; , Psammobatis
rutrum;,Psammobatis extenta ; , Psammobatis normani ; , Psammobatis rudis ; , Psammobatis
lentiginosa;,Rioraja agassizi ; , Schroederichthys bivius; , Sympterygia bonapartii.
(aHL2) were recorded (Fig. 2). All measurements were taken with vernier calipers at 0·1mm
precision.
STUDY AREA
The Argentine continental shelf comprises a part of the south-west Atlantic Ocean between
34◦and 55◦S. Water masses in this region consist of several water types: coastal, sub-
Antarctic, subtropical and mixed waters (Bisbal, 1995). In the north, the circulation is influ-
enced by the warm, more saline, south-flowing Brazil Current, which runs along the conti-
nental margin of South America and moves offshore at c. 36–38◦S (Olson et al., 1988). In
the south, a low salinity current of sub-Antarctic origin flows north along the coast, from the
Strait of Magellan (52◦30S) to 40–42◦S, where it veers offshore and flows northwards
over the outer shelf and slope. These water masses are modified substantially by inflow of
©2011 The Authors
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1264 E. MABRAGA ˜
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pA
aA
aHL aHL2
ECL
Fl
WLK
TLK
pHL
MAW
MIW
Fig. 2. Generalized egg case showing the morphometric characters utilized in the study: ECL, egg case length
(without horns); MAW, egg case width (maximum); MIW, egg case width (minimum); LaH, unfurled
anterior horn length; pHL, posterior horn length; LKW, lateral keel width; LKT, lateral keel thickness;
aA, anterior apron; pA, posterior apron; aHL2, straight distance from anterior apron to apex of anterior
horn; Fl, flange.
glacial waters from the Magellan Strait at 52◦30S and freshwater inputs from the Negro and
La Plata Rivers (Guerrero & Piola, 1997). These systems correspond to two biogeographic
provinces: the Argentine Province in the north, extending north to Rio de Janeiro, Brazil,
and the Magellanic Province in the south, which also includes southern Chile (Menni &
L´
opez, 1984).
RESULTS
One hundred and forty-six egg cases of 21 species of Chondrichthyes belonging
to nine genera were examined.
SUBCLASS HOLOCEPHALII, ORDER CHIMAERIFORMES
There is only one species in the south-west Atlantic Ocean, C. callorynchus,
endemic to South America.
©2011 The Authors
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CHONDRICHTHYAN EGG CASES 1265
Fl
(a) (b)
Fig. 3. (a) Dorsal view of the egg case of Callorhinchus callorynchus (Fl, flange). Scale bar =1 cm per unit.
(b) Surface of case (×40).
Callorhinchus callorynchus has relatively large and spindle-shaped egg cases
[Fig. 3(a)], with anterior and posterior tubular extensions and lateral flanges. The
dorsal surface of the case is relatively rough to touch due to the presence of undu-
late longitudinal striations in a zig-zag pattern [Fig. 3(b)]. The ventral surface is
smooth. The lateral flanges show transversal grooves oriented anteriorly on the ante-
rior tubular zone, straight or transversal in the section that houses the egg and in the
posterior two thirds part of case the flanges have two strong grooves oriented pos-
teriorly and followed by less pronounced grooves. The posterior tubular extension
has a mid keel and two lateral keels, whereas the anterior tubular extension only
possesses two pilous lateral keels. The dorsal case surface presents fibrous sheets of
byssus-like material, especially on lateral flanges.
Egg case measurements (n=3): length: 240–248 mm; maximum width: 75–
92 mm; case width without flange: 36–42 mm.
Callorhinchus callorynchus is widely distributed in the south-west Atlantic Ocean
from 23◦to 55◦S(L
´
opez et al., 2000), and in the south-eastern Pacific Ocean to
15◦S, from the coast to 200 m depth (Chirichigno, 1998). Egg cases were collected
from benthic samples at 40◦55S at 135 m depth (Fig. 1).
©2011 The Authors
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1266 E. MABRAGA ˜
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(a) (b)
Fig. 4. (a) Dorsal view of the egg case of Schroederichthys bivius. Scale bar =1 cm per unit. (b) Surface of
case (×40).
SUBCLASS ELASMOBRANCHII, ORDER
CARCHARINIFORMES, FAMILY SCYLHIORHINIDAE
This family in the south-west Atlantic Ocean comprises four species; three of them
have been recorded in the Argentine Continental Shelf (Menni & Lucifora, 2007;
Eschmeyer & Fricke, 2011): S. bivius,S. besnardi and S. haeckeli ; but only the first
is commonly found in Argentine waters and their capsules are described here. The
other two species have been reported from Uruguayan waters and their egg cases
were described from Brazil waters (Gomes & de Carvalho, 1995).
Schroederichthys bivius has a cigar-shaped egg case [Fig 4(a)], with fine and
straight longitudinal striations on the dorsal and ventral surfaces [Fig. 4(b)]. The
lateral flanges are narrow and posses fine transversal striae. The anterior border is
convex and tendrils are absent. The posterior border of the case has curled, filamen-
tous tendrils, longer than the egg case length [Fig. 4(a)].
Egg case measurements (n=13): length: 58–68 mm; width: 22–27 mm; lateral
keel width: 1·7–2·5 mm; keel thickness: 1·5–4 mm.
Schroederichthys bivius occurs in the south-west Atlantic Ocean from southern
Brazil (33◦S) south to the Beagle Channel (55◦S) (Soto, 2001), and in the south-
east Pacific Ocean to Valparaiso (33◦S), from 80 to 200 m depth. Females bearing
egg cases were found in northern Patagonian waters (Fig. 1).
ORDER RAJIFORMES, FAMILY RAJIDAE
Egg cases of skates are generally rectangular in shape with a horny process in
each corner. Measurements are presented in Table I. Diagnostic characteristics for
each genus and species are given below.
©2011 The Authors
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CHONDRICHTHYAN EGG CASES 1267
Table I. Measurements (range and mean ±s.d.; mm) of the egg cases of 19 species of skates from Argentinian waters (Fig. 1)
Species nECL MAW MIW aHL pHL LKW LKT aA pA aHL2
Atlantoraja
cyclophora
3 Range 69·0–75·037·5–44·633·7–39·652·0–54·098·0– 103·02·4–2·51·1–2·05·0–5·611·0–12·023·0–27·0
Mean ±s.d.51·7±3·238·1±3·834·4±3·338·0±1·073·5±2·54·0±0·11·5±0·54·7±0·39·9±0·630
·1±2·0
Atlantoraja
castelnaui
5 Range 96·7 – 103·8 68–78·263·6–70·367·0–77·0 118·0 –155·05·0–8·01·9–3·46·2–10·512·1–22·350·0–61·0
Mean ±s.d.99·8±3·772·4±3·866·3±2·571·0±5·0 133·6±13·46·9±1·12·4±0·67·6±1·815·9±3·855·7±4·5
Atlantoraja
platana
3 Range 71·0–72·044·8–47·2 39–40·243·6–56·3 110 –128 2·3–2·61·6–2·04·8–6·710·8–13·624·7–25·0
Mean ±s.d.71·6±0·546·1±1·239·7±0·650·6±6·5 121·7±10·12·5±0·21·8±0·25·5±1·112·1±1·424·8±0·2
Amblyraja
doellojuradoi
5 Range 67·0–73·047·3–54·238·0–48·043·0–50·050·0–68·04·3–6·00·3–0·66·0–8·312·5–16·021·0–26·0
Mean ±s.d.70·0±2·550·7±3·043·6±3·945·3±3·060·8±8·55·5±0·80·5±0·17·5±0·914·5±1·724·4±2·0
Bathyraja
albomaculata
8 Range 89·7–98·052·5–68·449·0–53·061·0–75·060·0–88·03·9–6·22·3–2·85·8–8·015·0–26·028·7–45·0
Mean ±s.d.95·9±3·660·0±4·951·2±1·570·0±5·070·0±8·65·1±1·02·6±0·27·0±0·820·8±3·733·8±5·5
Bathyraja
brachyurops
11 Range 82·0–93·053·0–65·442·0–58·060·0– 103·070·0 –117·03·2–6·00·5–1·63·4–9·0 11–19·631·0–39·0
Mean ±s.d.89·0±3·557·5±4·048·0±4·984·6±13·687·7±15·44·7±0·90·9±0·36·0±1·715·7±2·335·0±2·5
Bathyraja
macloviana
8 Range 75·0–84·943·5–48·537·8–42·044·0–60·047·0–63·02·5–4·02·5–3·05·0–12·012·4–17·021·5–29·0
Mean ±s.d.80·6±4·045·7±1·940·3±1·350·4±5·754·4±6·03·2±0·52·8±0·27·8±2·414·6±1·525·9±2·8
Bathyraja
magellanica
5 Range 79·8–88·055·5–60·042·4–45·340·0–59·085·0– 150·07·0–8·70·5–1·06·0–9·013·5–17·528·0–30·3
Mean ±s.d.83·6±4·057·6±2·243·9±1·048·0±7·3 119·8±32·17·4±0·70·7±0·37·0±1·215·5±2·029·6±0·9
Zearaja
chilensis
14 Range 115·0 – 158·058·7–70·852·7–67 53·0–73·063·0– 117·03·9–7·90·9–2·57·0–18·033·0–54·021·0–36·0
Mean ±s.d. 131·5±14·465·7±4·259·4±5·162
·2±6·189·6±16·65·0±1·21·7±0·512·4±3·441·4±5·727·6±4·3
Dipturus
trachyderma
2 Range 222·0 – 230·0 163– 154·0 100·0 – 107·078·0–88·074·0–78·043·0–33·00·5–1·065·0–70·056·0–65·015·0
Mean ±s.d·226·0±5·7 158·5±6·4 103·5±4·983·0±7·176·0±2·838·0±7·10·8±0·467·5±3·560·5±6·415·0
Psammobatis
bergi
10 Range 39·6–43·5 34–35·431·9–33·928·0–40·051·0–67·01·9–2·90·5–1·31·78–2·54·1–9·019·0–23·8
Mean ±s.d.41·9±1·434·7±0·432·8±0·635·4±1·05 56·8±2·82·3±0·10·8±0·32·1±0·16·1±1·221·0±1·8
©2011 The Authors
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1268 E. MABRAGA ˜
NA ET AL.
Table I. Continued
Species nECL MAW MIW aHL pHL LKW LKT aA pA aHL2
Psammobatis
extenta
10 Range 25·5–30·917·9–20 14·9–16·617·0–26·027·0–45·01·0–1·30·5–0·91·0–1·93·0–6·011·0–15·0
Mean ±s.d.28·7±2·119·1±0·615·7±0·621·7±2·933·6±4·91·1±0·10·7±0·21·5±0·34·6±1·013·2±1·4
Psammobatis rutrum 1 Value 26·719·616·316·037·01·40·61·72·613·0
Psammobatis
normani
18 Range 41·0–52·028·8–36 25·0–32·525·0–63·055·0–76·02·2–3 0·4–0·8 2–3·84·52–8 21·4–29
Mean ±s.d.45·7±3·531·5±2·327·8±2·245·4±8·663·8±5·82·5±0·20·6±0·12·6±0·56·2±1·024·7±2·5
Psammobatis
rudis
6 Range 45·6–53·526·1–36·923·0–32·824·0–36·050·0–74·02·3–3·70·6–0·62·4–3·6 5–6·611·5–24
Mean ±s.d.49·8±3·232·9±4·829·5±4·428·7±5·063·8±10·83·0±0·60
·6±0·03·0±0·55·8±0·617·6±4·4
Psammobatis
lentiginosa
6 Range 34·6–40·6 24–27·719·2–24·518·0–25·035·0–48·01·8–2·00·6–1·0 2–3·85·6–7·711·0–15·6
Mean ±s.d.37·9±2·525·5±1·721·3±2·520·0±3·239·3±5·21·9±0·10·8±0·22·9±0·76·9±0·713·9±1·9
Rioraja
agassizi
5 Range 61·0–68·037·5–40·535·5–37·047·0–56·062·0–79·02·3–3·00·9–1·74·0–8·09·2–10·532·0–38·2
Mean ±s.d.63·8±2·639·0±1·136·1±0·552·8±4·169·6±6·92·8±0·31·3±0·45·1±1·710·0±0·534·6±2·8
Sympterygia
acuta
Range 51·2–57·532·4–36·026·4–29·0 29–39·7 180– 293 1·0–2·02·8–3·42·5–4·94·0–7·214·0–22·3
10 Mean ±s.d.54·8±2·434·4±1·527·6±0·934·9±3·0 232·1±41·91·3±0·43·1±0·23·7±0·86·1±1·018·4±3·1
Sympterygia
bonapartii
8 Range 68·3–86·541·4–52·237·0–44·840·0–58·0 117·0–158·00·5–1·95·0–6·23·7–6·26·6–12·026·0–32·0
Mean ±s.d.81·2±5·649·6±3·442·5±2·450·6±5·3 135·3±16·61·5±0·45·7±0·45·4±0·710·4±1·828·9±2·3
n, sample size; ECL, egg case length (without horns); MAW, egg case width (maximum); MIW, egg case width (minimum); aHL, anterior horn length; pHL, posterior horn length; LKW, lateral keel width; LKT,
lateral keel thickness; aA, anterior apron; pA, posterior apron; aHL2, straight distance from anterior apron to apex of anterior horn.
©2011 The Authors
Journal of Fish Biology ©2011 The Fisheries Society of the British Isles, Journal of Fish Biology 2011, 79, 1261 –1290

CHONDRICHTHYAN EGG CASES 1269
Amblyraja
This genus comprises at least four species in the south-west Atlantic Ocean: the
southern thorny skate Amblyraja doellojuradoi (Pozzi 1935), the thickbody skate
Amblyraja frerichsi (Krefft 1968), the whiteleg skate Amblyraja taaf (Meisner 1987)
and the Antarctic starry skate Amblyraja georgiana (Norman 1938), but only the
first inhabits the Argentine continental shelf (Menni & Stehmann, 2000; Cousseau
et al., 2007).
The egg cases of A. doellojuradoi are medium size, 67 – 73 mm in length (horns
excluded), with maximum egg case width (MAW) c. 66 – 80% of egg case length
(ECL) and possess a remarkable lateral keel, c. 9–12% of MAW, extending the
length of the case, tapering off along the outer edge of the horns. The anterior horns
finish abruptly, whereas the posterior horns taper progressively [Fig. 5(a)]. The dorsal
surface of the cases, including both the lateral keels and the horns base, are covered
with fine fibroids. The dorsal and ventral surfaces of the cases are finely striated
without ridges but with fine transversal scars along the stries [Fig. 5(b)]; apparently,
no other skate egg cases have these scars. Attachment fibres are absent. The anterior
horns curl ventrally, and are flattened and hook-like towards the tips; the length of
the anterior and posterior horn is c. 62–68% of ECL. The posterior apron is wider
than the anterior one. The posterior horns are flattened to a filamentous tip, relatively
short (70–100% of ECL) but longer (1·1–1·6 times) than the anterior horns.
Amblyraja doellojuradoi is distributed in the south-west Atlantic Ocean between
36◦and 56◦S, and from 51 to 642 m depth; but is relatively more abundant between
36◦and 42◦S. (Menni & Stehmann, 2000; Cousseau et al., 2007). Females bearing
egg cases were found at 40◦59S; 57◦05W at 143 m depth (Fig. 1).
Atlantoraja
This genus comprises three species, the spotback skate Atlantoraja castelnaui
(Miranda Ribeiro 1907), the eyespot skate Atlantoraja cyclophora (Regan 1903)
and la Plata skate Atlantoraja platana (G¨
unther 1880), endemic to the south-west
Atlantic Ocean (Menni & Stehmann, 2000; Cousseau et al., 2007). The egg cases
(Fig. 6) are medium to large, 69– 104 mm in length (horns excluded) and present
relatively large posterior horns.
Atlantoraja castelnaui [Fig. 6(a)] has the largest case within the genus, >95 mm in
length, with MAW c. 66 – 81% of ECL. The base of the horns and lateral margins are
covered by adhesive fibrils. The dorsal surface of case is densely covered with woven-
like fibres [Fig. 7(a)]. Both case surfaces, except the fibrous layer, are relatively
smooth, finely striated and without ridges; these striae are irregular in size [Fig. 7(b)].
The anterior horns are slightly curved ventrally; their length is c. 66–78% of ECL.
The posterior apron edge is relatively flat and wider than the anterior apron. The
lateral keel width (LKW) is narrow, c. 7–10% of MAW. The posterior horns are
long, c. 1·2–1·5 times ECL and c. 1·7–2·0 times the length of the anterior ones.
The aHL2 is relatively large, >50% of ECL.
Egg cases of A. cyclophora [Fig. 6(b)] are medium size (<75 mm on length),
with MAW c. 54 – 59% of ECL. The base of the horns, lateral margins and dorsal
face of the capsule are covered by a layer of sticky fibrils. The surface of the case is
longitudinally striated with marked ridges on the dorsal face [Fig. 7(c)]. The anterior
horns are relatively short, c. 49–53% of ECL. The posterior apron edge is markedly
convex. The LKW is narrow, c. 6–7% of MAW. The posterior horns are long, c.
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1270 E. MABRAGA ˜
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SC
(a)
(b)
Fig. 5. (a) Dorsal view of the egg case of Amblyraja doellojuradoi. Scale bar =1 cm per unit. (b) Surface of
case (×40). SC, scars.
1·3–1·4 times ECL, and c. 1·9 times the length of the anterior horns. The aHL2 is
relatively short, <40% of ECL.
Egg cases of A. platana [Fig. 6(c)] are medium size (<75 mm in length) with
MAW c. 63 – 66% of ECL. The base of the horns, lateral margins and both faces of
the capsule are covered by sticky fibrils. The case surface is longitudinally striated
with marked ridges especially on the dorsal face [Fig. 7(d)]. The posterior apron
edge is relatively flat. The LKW is narrow, c. 5–6% of MAW. The anterior horns
are curved inwards, their length c. 55% of ECL. The posterior horns are long (>1·5
times ECL) and c. 2·3–2·5 times the length of the anterior horns. The aHL2 is
relatively short (<40% of ECL).
Atlantoraja castelnaui and A. cyclophora are distributed in the south-west Atlantic
Ocean between Rio de Janeiro (22◦S) and north Patagonia (42◦S), from the coast
to 100–130 m depth, but are more abundant in shallower waters <60 m (Menni &
Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were found in
northern Argentina at 38–60 m depth (Fig. 1). Atlantoraja platana is distributed in
the south-west Atlantic Ocean from Espirito Santo (Brazil, 20◦S) south to San Matías
Gulf (Argentina, 42◦S), from the coast to 149 m depth (Menni & Stehmann, 2000;
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CHONDRICHTHYAN EGG CASES 1271
(a) (b) (c)
Fig. 6. Dorsal view of the egg cases of (a) Atlantoraja castelnaui,(b)Atlantoraja cyclophora and
(c) Atlantoraja platana. Scale bar = 1 cm per unit.
Cousseau et al., 2007). Females bearing egg cases were found in waters adjacent to
northern Argentina and Uruguay at 120 m depth (Fig. 1).
Bathyraja
The genus comprises 11 species in the south-west Atlantic Ocean, but is rep-
resented by eight species in the Argentine continental shelf, the white-dotted skate
Bathyraja albomaculata (Norman 1937), the broadnose skate Bathyraja brachyurops
(Fowler 1910), the joined-fins skate Bathyraja cousseauae Díaz de Astarloa &
Mabraga˜
na 2004, the greytail skate Bathyraja griseocauda (Norman 1937), the Pata-
gonian skate Bathyraja macloviana (Norman 1937), the Magellan skate Bathyraja
magellanica (Philippi 1902), the multispine skate Bathyraja multispinis (Norman
1937) and the cuphead skate Bathyraja scaphiops (Norman 1937) (Menni &
Stehmann, 2000; Cousseau et al., 2007). The capsules of four of these species are
described below.
The egg cases are medium to large size, 75– 98 mm in length, and have a very
conservative morphology (Fig. 8). The posterior horns are strongly curved inwards
and the aHL2 is relatively short (<50% of case length). The surface of cases is
generally coarse, often with prickles, and rough to the touch.
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1272 E. MABRAGA ˜
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(a) (b)
(c) (d)
Fig. 7. Surface of case of Atlantoraja species showing the different patterns at magnification (×40).
(a) Atlantoraja castelnaui with woven-like fibres, (b) Atlantoraja castelnaui showing structure beneath
fibrous layer, (c) Atlantoraja cyclophora and (d) Atlantoraja platana.
Bathyraja albomaculata [Fig. 8(a)] has large egg cases (89 – 98 mm in length),
with MAW c. 54 – 75% of ECL. The case surface bears longitudinal striations with
long and thin prickles of different sizes, giving a velvety texture to the touch
[Fig. 9(a)]. Attachment fibres are absent. The LKT is relatively thick (>2 mm). The
LKW is narrow (6–11% of MAW). The posterior apron is wider (2·1–3·6 times)
than the anterior apron. The anterior and posterior horns are similar in length and
relatively short (<90% of ECL).
Egg cases of B. brachyurops [Fig. 8(b)] are large (82– 93 mm in length), with
MAW c. 70 – 81% of ECL. The egg case surface is relatively smooth, finely stri-
ated, with rasp-like denticles and without prickles [Fig. 9(b)]. Attachment fibres are
observed at the bases of the posterior horns and posterior apron. The LKT is rela-
tively thin (<2 mm). The LKW is narrow (6–11% of MAW). The posterior apron is
wider (1·9–4·2 times) than the anterior apron. The anterior and posterior horns are
similar in length and relatively short (<1·3 times ECL).
Bathyraja macloviana [Fig. 8(c)] has the smallest egg case within the genus
(75–84 mm in length), with MAW c. 52– 59% of ECL. The surface texture is coarse
and very rough to the touch due to papillose longitudinal ridges. The prickles have
different sizes and shapes [Fig. 9(c)]. Attachment fibres are absent. The LKT is rela-
tively thick (>2 mm) and the LKW is narrow (6–9% of MAW). The posterior apron
is wider (1·2–3 times) than the anterior apron. The anterior and posterior horns are
relatively short and similar in length (<75% of ECL).
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CHONDRICHTHYAN EGG CASES 1273
(a) (b)
(c) (d)
Fig. 8. Dorsal view of the egg cases of (a) Bathyraja albomaculata,(b)Bathyraja brachyurops,(c)Bathyraja
macloviana and (d) Bathyraja magellanica. Scale bar =1 cm per unit.
Egg cases of B. magellanica [Fig. 8(d)] are large (80 – 88 mm in length), with
MAW c. 68 – 70% of ECL. The capsule exhibits a wide lateral keel that is remark-
ably lighter in colour than the rest of the case. The case surface is similar to that
of B. abomaculata, but the prickles are all of uniform size [Fig. 9(d)]. Attachment
fibres are absent. The LKT is relatively thin (<2 mm). The LKW is broad (12–15%
of MAW). The posterior apron is wider (1·4 – 3 times) than the anterior apron. The
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1274 E. MABRAGA ˜
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(a) (b)
(c) (d)
Fig. 9. Surface of case of Bathyraja species showing the different patterns (×40). (a) Bathyraja albomaculata,
(b) Bathyraja brachyurops,(c)Bathyraja macloviana and (d) Bathyraja magellanica.
posterior horns are relatively short (c. 1·0–1·7 times ECL) but longer than the anterior
ones.
Bathyraja albomaculata occurs in the south-west Atlantic Ocean from 37◦to 55◦
S, from 70 to 815 m depth, and in the south-east Pacific Ocean to 45◦S (Menni &
Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were found along
the shelf at 116–154 m depth (Fig. 1). Bathyraja brachyurops is widely distributed
in the south-west Atlantic Ocean from 37◦to 55◦S, from 82 to 500 m depth, and in
the south-eastern Pacific Ocean to 45◦S (Menni & Stehmann, 2000; Cousseau et al.,
2007). Females bearing egg cases were found in Patagonian waters at 104–137 m
depth (Fig. 1). Bathyraja macloviana is widely distributed in the south-west Atlantic
Ocean from 36◦to 55◦S, from 82 to 505 m depth, and in the south-east Pacific
Ocean to 51◦S (Menni & Stehmann, 2000; Cousseau et al., 2007). Females bearing
egg cases were found in Patagonian waters at 106–144 m depth (Fig. 1). Bathyraja
magellanica is distributed in the south-west Atlantic Ocean from 45◦to 55◦S,
from 51 to 137 m depth, and in the south-east Pacific Ocean to 42◦S (Menni &
Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were found in
southern Patagonian waters at 100–113 m depth (Fig. 1).
Dipturus
In the south-west Atlantic Ocean, the genus Dipturus is represented by six species
(Díaz de Astarloa et al., 2008). Three of them inhabit the Argentine continental
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CHONDRICHTHYAN EGG CASES 1275
(a) (b)
Fig. 10. Dorsal view of the egg cases of (a) Zearaja chilensis and (b) Dipturus trachyderma. Scale bar =1cm
per unit.
shelf: the yellownose skate Dipturus chilensis (Guichenot 1848), [Last & Gledhill
(2007) discusses the species recent transfer from Dipturus to Zearaja], the roughskin
skate Dipturus trachyderma (Krefft & Stehmann 1975) and the Argentine skate Dip-
turus argentinensis Díaz de Astarloa, Mabraga ˜
na, Hanner & Figueroa 2008. A fourth
species, the south Brazilian skate Dipturus mennii Gomes & Parag ´
o 2001, has been
recorded at the border of Brazilian and Uruguayan waters (Bernardes et al., 2005)
and could be found in Argentine waters. The capsules of only the first two species
are described here.
The egg cases (Fig. 10) are very large, 115– 230 mm in length (horns excluded),
with a well-developed posterior apron and a very short aHL2 (<40% of case length).
The dorsal and ventral surfaces of the case are covered with dense woven-like fibres.
The surface of the cases beneath the fibrous layer is relatively smooth, finely striated
and without ridges [Fig. 11]. Fibre attachments are absent.
The egg cases of yellownose skate Zearaja chilensis (Guichenot 1848). [Fig. 10(a)]
are large (115–158 mm in length), with MAW c. 39–60% of ECL. The LKW is
narrow (6–11% of MAW), the posterior apron is very broad (37– 36% of ECL)
and wider than anterior apron. The anterior horns are relatively short (37–62% of
ECL), robust at the base, curving ventrally and flattened towards the tips. The poste-
rior horns are longer than the anterior horns (1–1·9 times), but still relatively short
(<90% of ECL), and possess a lighter flange along their inner edge.
The egg cases of D. trachyderma [Fig. 10(b)] are very large (>200 mm in length),
with MAW c. 67 – 73% of ECL. The LKW is very broad (21 –26% of MAW) and
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1276 E. MABRAGA ˜
NA ET AL.
(a)
(b)
Fig. 11. Surface of egg cases of (a) Zearaja chilensis and (b) Dipturus trachyderma showing the different
patterns (×40).
the anterior apron is also very broad (c. 30% of ECL) and wider than the posterior
apron. The anterior and posterior horns are similar in length and very short (<40%
of ECL).
Zearaja chilensis is widely distributed in the south-west Atlantic Ocean between
33◦and 55◦S, from 25 to 435 m depth, being more abundant between 50 and
150 m depth. In the south-east Pacific Ocean, this fish occurs as far south as 35◦S
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CHONDRICHTHYAN EGG CASES 1277
(Menni & Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were
found in northern Patagonian waters at 50 m depth (Fig. 1). Dipturus trachyderma
occurs in the south-west Atlantic Ocean from southern Brazil to 45◦S, from 80
to 200 m depth, and in the south-east Pacific Ocean to southern Chile (Menni &
Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were found in
central Patagonian waters at 83 m depth (Fig. 1).
Psammobatis
This genus, endemic to South America, comprises eight species, six of which are
present in the Argentine continental shelf: the shortfin sand skate Psammobatis nor-
mani McEachran 1983, the smallthorn sand skate Psammobatis rudis G¨
unther 1870,
the freckled sand skate Psammobatis lentiginosa McEachran 1983, the blotched sand
skate Psammobatis bergi Marini 1932, the zipper sand skate Psammobatis extenta
(Garman 1913) and the spade sand skate Psammobatis rutrum Jordan 1891 (Menni
& Stehmann, 2000; Cousseau et al., 2007; Mabraga˜
na, 2007). Another species (the
smalltail sand skate Psammobatis parvacauda McEachran 1983) has been recorded
in the south-west Atlantic Ocean around the Falkland Islands (McEachran, 1983) but
has never been found in the Argentine continental shelf.
The egg cases (Fig. 12) are small. Cases vary from 25 to 53 mm in length (horns
excluded) and are relatively smooth to the touch but finely striated under magnifica-
tion.
Egg cases of P. bergi [Fig. 12(a)] are smaller than 50 mm in length (horn
excluded) and square shaped. The MAW is >80% of ECL and has a relatively
convex anterior apron edge. The surface of the case is finely striated. The dorsal
surface is covered with a layer of longitudinal fibres, whereas the ventral surface
is naked [Fig. 13(a)]. The LKW is narrow (5–8% of MAW); the posterior apron is
wider (1·8–4·5 times) than the anterior one. The posterior horns are relatively short
(1·2–1·6 times ECL) but longer (1·4 – 2 times) than the anterior horns.
The egg cases of P. extenta [Fig. 12(b)] are very small (<31 mm in length), with
MAW c. 59 – 78% of ECL. The case surface bears fine longitudinal striations and
ornamentation only visible under magnification [Fig. 13(b)]. Attachment fibres are
observed along the lateral keel. The LKW is narrow (5–7% of MAW). The posterior
apron is wider than the anterior ones (2–6 times). The posterior horns are relatively
short (0·9–1·45 times ECL) but longer (1·1–2·2 times) than the anterior horns.
The egg cases of P. lentiginosa [Fig. 12(c)] are small (40 mm in length, horn
excluded), with MAW c. 63 – 71% of ECL. The aHL2 is very small (<40% of ECL)
and the posterior apron edge is slightly concave. The case surface and fibres are
arranged similar to those of P. bergi, and fibres on the dorsal face are fine and
scattered [Fig. 13(c)]. The LKW is narrow (7 – 8% of MAW) and the posterior apron
is wider (2–3·3 times) than the anterior ones. The posterior horns are relatively short
(0·9–1·2 times ECL) but longer (1·9–2·0 times) than the anterior horns.
The egg cases of P. normani [Fig. 12(d)] are small (50 mm in length, horn
excluded), with MAW c. 64 – 73% of ECL. The surface of the case is finely stri-
ated. Attached fibres at both lateral keels are close to each horn. The dorsal surface
is covered by a layer of longitudinal fibres, whereas the ventral surface is naked
[Fig. 13(d)]. A large aHL2 (49–60% of ECL) and a relatively flat posterior apron
are also present. The LKW is narrow (7–9% of MAW) and the posterior apron is
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1278 E. MABRAGA ˜
NA ET AL.
(a) (b) (c)
(d)
(e)
(f)
Fig. 12. Dorsal view of the egg cases of (a) Psammobatis bergi,(b)Psammobatis extenta, (c) Psammobatis
lentiginosa, (d) Psammobatis normani, (e) Psammobatis rutrum and (f) Psammobatis rudis. Scale bar =
1 cm per unit.
wider (3·6 times) than the anterior ones. The posterior horns are relatively short
(1·2–1·6 times ECL) but longer (1·1–2·6 times) than anterior horns.
Psammobatis rutrum [Fig. 12(e)] possess a very small egg case (<30 mm in
length), with MAW c. 73% of ECL. The surface of the case presents fine longitudinal
striations [Fig. 13(e)] and attached fibres along the lateral keel. The LKW is narrow
(7% of MAW). The posterior apron is relatively narrow (10% of ECL) but wider
than the anterior one (1·5 times). The posterior horns are relatively short (1·4 times
ECL) but longer (2·3 times) than anterior horns.
The egg cases of P. rudis [Fig. 12(f)] are small (50 mm in length, horn excluded),
with MAW c. 57 – 70% of ECL. The capsules have a flange at their posterior end,
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CHONDRICHTHYAN EGG CASES 1279
(a) (b)
(c) (d)
(e) (f)
Fig. 13. Surface of egg cases of species of Psammobatis showing the different patterns (×40).
(a) Psammobatis bergi,(b)Psammobatis extenta, (c) Psammobatis lentiginosa, (d) Psammobatis nor-
mani, (e) Psammobatis rutrum and (f) Psammobatis rudis.
which is characteristic of this species. The aHL2 is short (22–48% of ECL). The
surface of the case and pattern of attachment fibres are similar to those found in
P. normani, but the lack of a layer of fibres on the dorsal face distinguishes P. rudis
from the latter [Fig. 13(f)]. The LKW is narrow (8 – 10% of MAW) and the posterior
apron is wider (2·4 times) than the anterior ones. The posterior horns are relatively
short (0·98–1·6 times ECL) but longer (1·8–3·1 times) than the anterior ones.
Psammobatis rudis and P. normani are widely distributed in the south-west
Atlantic Ocean between 35◦and 55◦S, ranging from 49 to 350 m depth, but they are
more abundant between 70 and 180 m depth. In the south-east Pacific Ocean, these
species occur south to 30◦S (Menni & Stehmann, 2000; Cousseau et al., 2007;
Mabraga˜
na, 2007). Females of P. rudis bearing egg cases were found in Patag-
onian waters (45–55◦S) between 75 and 116 m depth (Fig. 1), whereas those of
P. normani were found throughout the shelf from 71 to 182 m depth (Fig. 1). Psam-
mobatis lentiginosa is distributed in the south-west Atlantic Ocean from 32◦to 46◦
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1280 E. MABRAGA ˜
NA ET AL.
S, from 49 to 164 m depth, being more abundant from 60 to 120 m depth (Menni
& Stehmann, 2000; Cousseau et al., 2007; Mabraga˜
na, 2007). Females bearing egg
cases were found at 35–45◦S, between 63 and 116 m depth (Fig. 1). Psammobatis
bergi and P. extenta are distributed in the south-west Atlantic Ocean from 23◦to
45◦S, and from the coast to 70 m depth, being more abundant between 25 and
66 m (Menni & Stehmann, 2000; Cousseau et al., 2007; Mabraga ˜
na, 2007). Females
bearing egg cases were found in northern Argentina from 25 to 66 m depth (Fig. 1).
Psammobatis rutrum occurs in the south-west Atlantic Ocean from southern Brazil
to 37◦S, from 51 to 100 m depth, but has been occasionally recorded in the Argen-
tine continental shelf (Menni & Stehmann, 2000; Cousseau et al., 2007; Mabraga˜
na,
2007). A single female bearing an egg case was found in northern Argentina at
100 m depth (Fig. 1).
Rioraja
This is a monospecific endemic genus distributed in temperate coastal waters of
the south-west Atlantic Ocean (Menni & Stehmann, 2000; Cousseau et al., 2007).
The Rio skate Rioraja agassizi (M¨
uller & Henle 1841) has a medium-sized egg
case [Fig. 14(a)], 61–68 mm in length (horns excluded); with MAW c. 60– 62% of
ECL. The surface of the case is finely striated without ridges, being smooth to the
touch [Fig. 14(b)]. The dorsal surface is covered with fine longitudinal fibres. The
aHL2 is large (>50% of case length). Egg cases possess silky attachment fibres
placed in the lateral keel close to each horn. The LKW is narrow (6–8% of ECL).
Both the anterior and posterior horns are relatively straight. The posterior apron is
wider (1·3–2·6 times) than the anterior one. The anterior horns are stout, relatively
long (c. 77–89% of ECL) and curving inwards at their tips. The posterior horns taper
to their tips, are moderately short (c. 0·98–1·2 times ECL), and longer (1·1–1·5
times) than the anterior horns.
Rioraja agassizi is a shallow water species distributed in the south-west Atlantic
Ocean from Espirito Santo (20◦S) south to 42◦S, from the coast to 150 m depth,
but in the Argentine continental shelf is more abundant at depths <60 m (Menni &
Stehmann, 2000; Cousseau et al., 2007). Females bearing egg cases were found off
northern Argentina from 15 to 27 m depth (Fig. 1).
Sympterygia
This genus comprises four species (McEachran & Dunn, 1998; Compagno, 2005)
endemic to South America. Two of them are distributed in coastal waters of the
south-west Atlantic Ocean: the smallnose fanskate Sympterygia bonapartii M¨
uller
& Henle 1841 and the bignose fanskate Sympterygia acuta Garman 1877 (Menni &
Stehmann, 2000; Cousseau et al., 2007).
The egg cases are small to medium size, 51–86 mm in length (horns excluded).
They have long and thread-like posterior horns, a very narrow lateral keel and a
marked lateral keel thickness (>5% of ECL, 1·6–4·8 times LKW) (Fig. 15). The
case surface is smooth and finely striated without ridges (Fig. 16). Attachment fibres
are placed at the end of the posterior horns. The anterior apron border is concave
while the posterior one is nearly straight.
The egg cases of S. bonapartii are medium size (68 – 86 mm in length), with
MAW c. 59 – 63% of ECL. The anterior horns curved inwards, flattening towards
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CHONDRICHTHYAN EGG CASES 1281
(a) (b)
Fig. 14. (a) Dorsal view of the egg case of Rioraja agassizi. Scale bar =1 cm per unit. (b) Surface of the
case (×40).
the tips and are c. 58–67% of ECL in length. The posterior apron is wider than
anterior apron (1·7–2·2 times). The posterior horns are long (>1·4 times ECL, but
<2·5 times) and c. 2·3–3·2 times the length of the anterior horns.
The egg cases of S. acuta are small (<60 mm in length), with MAW c. 57– 70%
of ECL. The surface of the case is glossy. The anterior horns curve ventrally, and
are flattened and thread-like toward their tips, their length c. 57–71% of ECL. The
posterior horns are extremely long (>3 times ECL) and c. 5·3–9·0 times the length
of the anterior ones. The posterior apron is wider (1·3–2·8 times) than the anterior
apron.
Sympterygia acuta is distributed in shallow waters in the south-west Atlantic
Ocean between 22◦S and 41◦S, from the coast to 50 m depth (Menni & Stehmann,
2000; Cousseau et al., 2007). Egg cases were collected from females after the adult
specimens had been deposited at the Museo del Mar aquarium. Sympterygia bona-
partii is widely distributed in shallow waters in the south-west Atlantic Ocean from
Rio Grande do Sul to 50◦S, from 20 to 100 m depth (Menni & Stehmann, 2000;
Cousseau et al., 2007). Females bearing egg cases were found in northern Argentina
from 12 to 49 m depth (Fig. 1).
DISCUSSION
The American endemic catsharks, genus Schroederichthys, are exclusively ovip-
arous and are represented by five species. Egg capsules of the narrowtail catshark
Schroederichthys maculatus Springer 1966, the slender catshark Schroederichthys
tenuis Springer 1966 and the redspotted catshark. Schroederichthys chilensis
(Guichenot 1848) have been previously described (Springer, 1979; Gomes & de Car-
valho, 1995; Hern´
andez et al., 2005). The egg cases of the genus Schroederichthys
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1282 E. MABRAGA ˜
NA ET AL.
(a) (b)
Fig. 15. Dorsal view of the egg cases of (a) Sympterygia acuta and (b) Sympterygia bonapartii. Scale bar =
1 cm per unit.
lack the typically coiled anterior tendrils of the family Scyliorhinidae. In S. tenuis,S.
chilensis and Schroederichthys saurisqualus Soto 2001, a couple of anterior filamen-
tous tendrils have been described (Gomes & de Carvalho, 1995; Hern´
andez et al.,
2005). In contrast, anterior tendrils were not found in S. bivius and S. maculatus
(Springer, 1979). Furthermore, in this study the majority of egg capsules have been
laid by females kept in captivity, therefore it has been possible to confirm that S.
bivius has capsules without anterior tendrils. Two species of Scyliorhinus, have been
reported from Uruguayan waters: Scyliorhinus haeckeli (Miranda Rivero 1907) and
Scyliorhinus besnardi Springer & Sadowski 1970. Their egg-laying area, however,
is probably in southern Brazil. They also have cigar-shaped egg cases but with the
anterior and posterior curled tendrils developed (Gomes & de Carvalho, 1995). The
genus Apristurus, the largest within the family Scyliorhinidae, comprises at least
three distinct species groups, the Apristurus brunneus (Gilbert 1892) group, Apris-
turus longicephalus Nakaya 1975 group and Apristurus spongiceps (Gilbert 1905)
group (Nakaya et al., 1999; Igl´
esias et al., 2005; Flammang et al., 2007). Similarity
of egg case morphology in species of Schroederichthys and the A. brunneus and A.
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CHONDRICHTHYAN EGG CASES 1283
(a)
(b)
Fig. 16. Surface of egg cases of (a) Sympterygia acuta and (b) Sympterygia bonapartii (×40).
longicephalus groups suggest a similar oviposition strategy. In contrast, the lack of
egg-case tendrils of the A. spongiceps group of catsharks suggests an evolutionary
divergence (Flammang et al., 2007). In vivo observations show that egg-case ten-
drils of the A. brunneus and A. longicephalus groups were wrapped around sedentary
organisms.
©2011 The Authors
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1284 E. MABRAGA ˜
NA ET AL.
The egg case morphology of C. callorynchus is similar to those of the other two
described species of the genus, the cape elephantfish Callorhinchus capensis Dum ´
eril
1865 and the ghost shark Callorhinchus milii Bory de Saint-Vincent 1823 (Smith &
Griffiths, 1997; Hamlett, 2005) The zig-zig pattern observed in the capsule surface
of C. callorynchus is unique among chondrichthyans. Unfortunately, the description
of egg case surfaces of other species of Callorhinchus is lacking.
Despite the high diversity and distribution of skates, comparative studies of their
egg cases are scarce and restricted to Japanese waters and the Bering Sea (Ishiyama,
1958; Ebert, 2005; Ebert & Davis, 2007). In the northern hemisphere, egg cases of
Bathyraja have been studied in detail since the middle of the last century (Ishiyama,
1958; Ishiyama & Ishihara, 1977; Ishiyama & Ishihara, 1985; Stehmann & Merrett,
2001; Ebert, 2005; Ebert & Davis, 2007). Egg cases in the south-west Atlantic Ocean
are very similar to those of the northern hemisphere. Although Bathyraja shows a
high species diversity, with wide distribution ranges (McEachran & Miyake, 1990)
the egg cases have a very conservative morphology, with typically strongly curved
posterior horns. Orlov & Biryukov (2005) suggest that this characteristic feature
probably facilitates the egg emergence from the cloaca.
In the worldwide genus Dipturus, two distinct forms of capsules were described.
Dipturus trachyderma possesses the largest egg case (222– 230 mm) and an unusual
case morphology according to the analyses made here. The egg case has well-
developed aprons and lateral keel, matching with those of other species from the
northern hemisphere, such as the giant skate Dipturus gigas (Ishiyama 1958)
(235 mm) and the longnosed skate Dipturus oxyrinchus (L. 1758) (140 –235 mm)
(Ishiyama, 1958; Bor, 2006), and those from Australian waters for instance, the
wedgenose skate Dipturus whitleyi (Iredale 1938) (220 mm) (Treloar et al., 2006).
The other type of capsule morphology in Dipturus (as shown by Z. chilensis) cor-
responds to an egg case typically shaped without a developed lateral keel and an
anterior apron, similar to other conspecific dipturids (Bor, 2006). Treloar et al. (2006)
described the capsules of several species of Dipturus showing a varied morphol-
ogy, these included the thornback skate Dipturus lemprieri (Richardson 1845) and
Dipturus sp. B (=D. canutus) similar to Z. chilensis.
With regard to species identification based on the external morphological features,
the endemic genus Psammobatis is the most problematic; in contrast, species identi-
fication by egg case characters is less problematic. This genus possesses the smallest
egg case among worldwide skates: P. rutrum has capsules that reach c. 30 mm length
(Bor, 2006). The features of the capsules of the raspthorn sandskate Psammobatis
scobina (Philippi 1857) (Concha et al., 2009) are coincident with those (described
here) of P. normani.
The genus Sympterygia has the largest posterior horn compared to other skates.
Oddone & Vooren (2002) found capsules of S. acuta with posterior horns of 440 mm
in length. Egg cases of S. acuta and S. bonapartii are commonly found on sandy
beaches of the Buenos Aires coast, frequently attached to the debris. Long tendrils
may help to secure the egg case with some form of substratum (Flammang et al.,
2007). The coasts of southern Brazil, Uruguay and northern Argentina generally lack
hard bottom substrata and appropriate sea-floor vegetation for the attachment of egg
cases. Flammang et al. (2007) have established that these are the reasons for the
development of extremely long horns with silky fibres in these species. The absence
of hard substrata could be a pressure for the development of long tendrils, which may
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CHONDRICHTHYAN EGG CASES 1285
help to secure anchorage with other capsules and then make them difficult to remove
from the spawning site. This characteristic (an extremely long posterior horn) feature
was also observed in the egg cases of an Australasian skate of the genus Pavoraja
(Treloar et al., 2006). Capsules of Sympterygia, however, also possess a marked
thickening of the lateral keel, which is a feature not observed in species of Pavoraja
or any other species.
Egg cases of A. doellojuradoi possess a remarkable lateral keel extending the
length of the case and tapering off along outer edge of horns. The anterior end of the
horn finishes abruptly, whereas its posterior end tapers progressively. These char-
acteristics were also observed in A.cf. hyperborea from Australian waters (Treloar
et al., 2006) and in an unidentified deep-sea egg case from the eastern North Pacific
Ocean (Ebert & Davis, 2007). The latter specimen was called an ‘unidentified deep-
sea skate egg case B’, because it was collected from benthic samples and not from
a female uterus. Ebert & Davis (2007) explained that a female of the broad skate
Amblyraja badia (Garman 1899) was observed swimming in the vicinity of where
these egg cases were collected. As A. badia is the only species of Amblyraja reported
for the eastern North Pacific Ocean, these egg cases probably correspond to this
species. Morphologically, capsules of the three species are very similar, with that of
A. doellojuradoi being the smallest. This is unsurprising given that A. doellojuradoi
is the smallest species of the genus reaching at least 600 mm total length (LT),
whereas A. badia and A. hyperborea reach c. 1000 mm LT.
The foregoing description of egg cases of Rioraja and Atlantoraja species are
consistent with those made previously for Brazilian waters (Oddone et al., 2006).
As egg cases can be a useful tool for identifying chondrichthyan species, a provi-
sional key to the south-western Atlantic Ocean chondrichthyan egg cases is presented
here.
IDENTIFICATION KEY FOR CHONDRICHTHYAN EGG CASES OF THE
SOUTH-WEST ATLANTIC OCEAN
1a. Spindle-shaped egg case, with anterior and posterior tubular extensions and
lateral flanges, and without horns or tendrils .................. Callorhinchus
callorynchus
1b. Egg case not spindle shaped, horns or tendrils on one or both ends ..........2
2a. Cigar-shaped egg case with tendrils ..................................... 3
2b. Rectangular egg case with anterior and posterior horns .....................4
3a. Egg case with posterior curled tendrils ..................... Schroederichthys
bivius
3b. Egg case with anterior and posterior curled tendrils ......... Scyliorhinus spp.
Remarks: Two species of Scyliorhinus have been reported for Uruguayan waters
(see references in text), but probably their egg-laying area is in southern Brazil.
Capsules characteristics were taken from Gomes & de Carvalho (1995) and Bor
(2006).
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1286 E. MABRAGA ˜
NA ET AL.
4a. Egg case length (ECL) >110 mm; well-developed posterior apron (>30% of
ECL); dorsal and ventral surfaces of case covered with dense woven-like fibers;
surface of the case beneath the fibrous layer relatively smooth, finely striated
and without ridges ...................................Dipturus and Zearaja
4b. The ECL <110 mm; posterior apron narrow or moderately developed (<30% of
ECL); only the dorsal surface of case covered with dense woven-like fibres, or
surface without these woven-like fibres ...................................6
5a. The ECL >200 mm, lateral keel >20 mm .................. D. trachyderma
5b. The ECL <170 mm, lateral keel <20 mm ....................Z. chilensis
Remark: Other species of Dipturus could be found in the Argentine continental
shelf (see references in text), whose egg cases have not been observed.
6a. Posterior horns thread-like, their length >1·4 times case length, lateral keel
thickness >1·6 times lateral keel width ......................Sympterygia 7
6b. Posterior horns progressively thinner, of different lengths, lateral keel thickness
up to one time lateral keel width .........................................8
7a. The ECL >65 mm, posterior horns long, <2·5 times case length............
............................................................. S. bonapartii
7b. The ECL <60 mm, posterior horns very long, >3·5 times case length .......
................................................................ S. acuta
8a. The ECL <60 mm ........................................ Psammobatis 9
8b. The ECL >60 mm ....................................................14
9a. The ECL ≤31 mm .................................................... 10
9b. The ECL >34 mm .................................................... 11
10a. Posterior apron more than twice anterior apron width ......... P. extenta
10b. Posterior apron less than twice anterior apron width ............ P. rutrum
11a. Square-shaped case, case width >80% of ECL, anterior apron straight or
slightly convex ...................................................P. bergi
11b. Rectangular-shaped case, case width <75% of ECL, anterior apron concave
...................................................................... 12
12a. The ECL ≤40 mm, anterior horn straight distance <20 mm . ....P. lentiginosa
12b. The ECL >40 mm, anterior horn straight distance >20 mm ............... 13
13a. Posterior apron with a flange, anterior horn straight distance <50% of case
length ........................................................... P. rudis
13b. Posterior apron without a flange, anterior horn straight distance generally >50%
(49–60%) of ECL ............................................P. normani
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CHONDRICHTHYAN EGG CASES 1287
14a. Posterior horns strongly curved towards the inside, making a semicircle, surface
of case rough or relatively smooth ............................. Bathyraja 15
14b. Posterior horns straight or slightly curved ................................ 18
15a. Lateral keel thickness >2mm...........................................16
15b. Lateral keel thickness <2mm..........................................17
16a. The ECL >90 mm, maximum width >50 mm, surface of case with longitudinal
striation with long and thin prickles of different size, giving a velvety texture
to the touch .............................................. B. albomaculata
16b. The ECL <90 mm, maximum width <50 mm, egg case surface texture coarse
and very rough to the touch, covered by papillose longitudinal ridges; prickles
with different sizes and shapes ..............................B. macloviana
17a. Lateral keel somewhat light, ≥6 mm; surface of case with longitudinal striation
with long and thin prickles of similar size, posterior horns longer than anteriors,
the lateral keel width (LKW) is relatively broad, 12–16% of the maximum egg
case width (MAW) .......................................B. magellanica
17b. Lateral keel somewhat dark, ≤6 mm; egg case surface is relatively smooth,
finely striated, with rasp-like denticles and without prickles; LKW relatively
narrow (6–11% of MAW) .................................B. brachyurops
Remark: Other four species of the genus are present in the Argentine continental
shelf where egg cases have not been observed. Possibly adult females lay its
capsules at depth furthermore the continental slope.
18a. Anterior horn straight distance >50% of ECL, with attachment fibres displayed
in the lateral keel next to each horn .........................Rioraja agassizi
18b. Anterior horn straight distance <50% of ECL, if it is greater, ECL is always
>90 mm, attachment fibres absents or displayed in a different way ..........19
19a. Posterior horns very large, longer than case length, lateral keel tapering progres-
sively to anterior horns .....................................Atlantoraja 20
19b. Posterior horns shorter than ECL, lateral keel tapering abruptly in anterior horns
......................................................... A. doellojuradoi
20a. The ECL >95 mm, dorsal surface with woven-like fibres; surface of case
beneath fibrous layer finely striated without ridges .............. A. castelnaui
20b. The ECL <80 mm, without woven-like fibres; surface of case longitudinally
and uniformly striated with marked ridges especially on dorsal face .. ........21
21a. Posterior horns long, their length <1·5 times ECL; MAW <60% of ECL
........................................................... A. cyclophora
21b. Posterior horns very long, their length >1·5 times ECL; MAW >60% of ECL
..............................................................A. platana
©2011 The Authors
Journal of Fish Biology ©2011 The Fisheries Society of the British Isles, Journal of Fish Biology 2011, 79, 1261 –1290

1288 E. MABRAGA ˜
NA ET AL.
We thank the skippers, crews and scientists of the R.V. O. Balda and R.V. E. L. Holmberg
from the Instituto Nacional de Investigaci´
on y Desarrollo Pesquero for their assistance in the
collection of samples. We also thank C. Bremec for the assistance in obtaining capsules from
benthos campaigns, L. Lucifora for comparative material, Museo del Mar for taking samples
from captive specimens and C. Milloc and M. Farenga for providing technical assistance. We
would like to thank anonymous reviewers and I. Harrison for offering helpful comments that
improved the earlier drafts of the manuscript. This research was partially supported by grants
of FONCYT (PICT 2007 02200), CONICET (PIP 0942) and UNMdP (EXA 490/10). L.B.S.
and G.D. were supported by scholarships from CONICET.
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