Squid recruitment dynamics 
The genus ///ex as a model, 
the commercial ///ex species and 
influences on variability 
FAO 
FISHERIES 
TECHNICAL 
PAPER 
376 
Chapter 2 
Systematic and distributional relationships of lit'ex coindetii 
to the genus Illex (Cephalopoda; Ommastrephidae). 
Clyde F.E. Roper and Katharina M. Mangold 
Edited by 
P.G. Rodhouse 
British Antarctic Survey 
Natural Environment Research Council 
Cambridge, United Kingdom 
E.G. Dawe 
Science Branch 
Department of Fisheries and Oceans 
St John's, Newfoundland, Canada 
R.K. O'Dor 
Department of Biology 
Dalhousie University 
Halifax, Nova Scotia, Canada <l**""*S<* 
FAO Fisheries Technical Paper, No. 376. Rome, FAO. 1998. 273 pp. 
Food 
and 
Agriculture 
Organization 
of 
the 
United 
Nations   - 
Rome, 1998 
The designations employed and the presentation of material in this 
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00100 Rome, Italy. 
? FAO 1998 
1 
2 
13 
Chapter 2 
Systematic and distributional relationships of lllex coindetii 
to the genus lllex (Cephalopoda; Ommastrephidae) 
Clyde F.E. Roper1   and   Katharina M. Mangold2 
Department of Invertebrate Zoology - Mollusca, National Museum of Natural History, Smithsonian 
/wV/W/o/i, WafA/Mgfo/7, DC. 20J60, C/&4 
Observatoire Oceanologiqne de Banyuls, Labaratoire Arago Universite de Pierre et Marie Curie (Paris 
VI). C.N.R.S. Institut National des Sciences de I"Universite, Banyuls-sur-Mer 66650, France 
Abstract: The systematic status of lllex coindetii is analysed based on a study of specimens from across the 
known geographic range of the species. On the basis of several morphological characters, some newly 
recognized, particularly on the heetoeotylized arm, /. coindetii is shown to be a single, variable, widely 
distributed species, morphotypes of which occur throughout the Mediterranean Sea, the eastern Atlantic from 
Great Britain to Namibia and the western Atlantic from the southeastern Caribbean Sea, the Gulf of Mexico and 
the Straits of Florida. /. coindetii is distinct from the other species of lllex that occur in the western Atlantic. 
Species characters are compared and a diagnostic key to the four species of lllex is presented. 
1    Introduction 
lllex coindetii (Verany, 1839) was described originally from the Mediterranean waters off Nice, France. 
It has been recorded subsequently from the entire Mediterranean Sea, the eastern Atlantic from the Bristol 
Channel, British Isles, southward to Namibia, and the western Atlantic from the Caribbean Sea, Gulf of 
Mexico and Straits of Florida (Lu 1973, Roper et al. 1984, Nesis 1987). The exceptionally widespread 
distribution throughout the eastern Atlantic and the Mediterranean, as well as its disjunct occurrence on 
opposite sides of the Atlantic, is an unusual distribution for a neritic cephalopod. This factor, coupled with 
the remarkable morphological variation observed throughout its range, has created considerable doubt as to 
the conspecific taxonomic status of the far-flung morphotypes. Does this pattern represent one widely 
distributed, highly variable species, or is it in fact a complex of closely related, yet distinct, species? The 
answers to these questions have broad significance biologically, e.g. recruitment, and. particularly, in relation 
to management and exploitation of the populations as a fishery resource. 
The systematics of the genus lllex is currently being examined, primarily because of the confusing situation 
of the occurrence of three of the four described species in the waters of the western Atlantic, particularly in 
the Gulf of Mexico and from the Straits of Florida to the mid-Atlantic Bight (Zecchtni et al. 1996, Roper et 
al. 1998). These species are lllex illecebrosus (Lesueur, 1821), /. coindetii (Verany, 1839) and lllex o.xygonins 
Roper, Lu and Mangold. 1969. Because all three species appear to co-occur in the common extremes of their 
ranges and because they also are morphologically similar, they are difficult to distinguish and identify (Roper 
et al. 1969). Furthermore, their biology is so poorly known in this geographical region that currently no 
biological clues exist to aid in discriminating these species. The fourth species, lllex argentinus (Castellanos. 
1960), from the southwestern Atlantic, is sufficiently isolated geographically and morphologically to be quite 
distinct and easily identified. 
The objective of this study is to determine the systematic status of /. coindetii. We attempt to define the 
range of variation in some distinct characters, a few newly discovered, that are especially useful for identifying 
adults of the species. This has been accomplished by examining specimens from a wide, although not 
completely comprehensive, sample of populations throughout the geographical range of the species. We 
14 
discovered these distinctive characters when we simultaneously compared specimens of/, coindetii with the 
other three species of Illex. Comparative information on the other three species is presented in tabular form 
and a key to the identification of all four species is also given. 
2    Material examined 
The specimens used in this analysis (listed below) were selected from as broad a coverage of the 
geographical range as possible, and they represent, as nearly as possible, fully mature animals. A number of 
specimens from the Mediterranean and off Vigo, Spain, were collected specifically for this study. All material 
was available for examination at the workshop conducted on /. coindetii systematics and fishery biology in 
Mazara del Vallo, Sicily, in October 1992. The remaining specimens are from the collections of the National 
Museum of Natural History, Washington, DC. (USNM) or borrowed from the Rosenstiel School of Marine 
and Atmospheric Sciences, University of Miami (UMML), Florida. 
Mediterranean Sea 
Greece   - Sep 1992 
1 male 159 mm ML 1 female'201 mm ML 
Southern Adriatic - off Mola di Ban, Italy, 210 m, sand-mud bottom, 8 Oet 1992 
3 males 119-120 mm ML 6 females 103-135 mm ML 
Sicily      - Strait of Sicily 
5 males 131-141 mm ML 1 female 186 mm ML 
Tunisia   -Gulf of Tunis 
2 males 151-154 mm ML 8 females 150-185 mm ML 
- Gulf of Tunis, Mediterranean Marine Sorting Center, 64-75 m, 30 Mar 1967, USNM 884245 
1 male 130 mm ML 3 females 151-164 mm ML 
- Gulf of Tunis, Mediterranean Marine Sorting Center 
2 males 130-141 mm ML 
Catalonia - Port-Vendres, France, 42?33'30"N  003?39'E, 200-500 m,  03 Nov 1971, USNM 727457 
1 male 125 mm ML 
- Barcelona, Spain 
1 male 130 mm ML 2 females 115-132 mm ML 
Eastern Atlantic Ocean 
Spain      - Vigo 
4 males 105-130 mm ML 4 females 160-176 mm ML 
Africa     - Gulf of Guinea, R/V Pillsbury sta. 45, 05?05'N, 04?04.5'W, 73-98 m, 30 May 1964, UMML 31.1611 
1 male 121 mm ML I female 160 mm ML; off Liberia 
- Gulf of Guinea, R/V Pillsbury sta. 82, 04?57'N, 09?30'W, 144 m, 5 June 1964, UMML 31.1335 
1 male 129 mm ML 1 female 188 mm ML 
- off Namibia, R/V Ocher sta. 127, 18?56'S, 12?05'E, 130 m,   9 May 1988, USNM 884246 
2 males 126-131 mm ML 3 females 97-141 mm ML 
Western Atlantic Ocean 
Caribbean - off Nicaragua, R/V Oregon sta. 3615, 14?16'N, 81?55'W, 400 m, 5 June 1962, UMML 31.648 
1 male 170 mm ML 
- off Nicaragua, R/V Pillsbury sta. 1356, 14?54'N, 81?23'W, 296-375 m, 31 Jan 1971, UMML 31.1899 
2 males 152-163 mm ML 
Gulf of Mexico - off Louisiana, R/V Oregon sta. 4607, 27?39'N, 93?46'W, 366 m, 18 Jan 1964, UMML 31.1889 
1 male 185 mm ML 
- off Mississippi, R/V Oregon sta. 481, 28?57'N, 88?41'W, 420 m, 7 Sep. 1951, UMML 31.353 
1 male 153 mm ML 1 female 185 mm ML 
Straits of Florida, USA - R/V Oregon sta. 10862, 23?25'N, 79?40'W, 450 m, 16 Dec. 1969, USNM 729016 
1 female 319 mm ML 
- R/V Oregon sta. 10863, 23?09'N, 80?08'W, 459 m, 16 Dec. 1969, USNM 729015 
1 male 252 mm ML 
15 
ventral papillae 
dorsal lamellae 
reduced suckers 
constriction 
papillose flaps C& 
normal suckers 
HALt 
Figure 2.1. Diagrammatic illustration of measure- 
-ments of squid (adapted from Roper and Voss 
1983), definitions given in text 
Figure 2.2. Diagrammatic illustration of hectoco- 
-tylized arm of/, coindetii, left arm IV, 125 
mm ML; USNM 727457, definitions given in 
text 
3    Expanded diagnosis 
This diagnosis is detailed enough to permit the identification of /. coindetii using selected key characters, 
especially those associated with mature males. Figures 2.1-2.3 diagram the standard measurements used in 
this study and as defined in Roper and Voss (1983). A fuller description of the species, including the 
designation of a neotype, is presented in Roper et al. (1998). 
16 
Figure 2.3. Illustration of the 
measurements and charac- 
ters of the beaks of squid 
(from Clarke 1986 by per- 
mission Oxford University 
Press); these images can be 
viewed stereoscopically by 
placing a surface mirror 
vertically between the ima- 
-ges, reflecting to the left. 
View the reflection of the 
left image with the left eye 
and the right image directly 
with the right eye. 
3.1  Club suckers 
The largest sucker rings on the manus of the club are notched, forming low. truncate to bluntly rounded 
crenulations, either in the distal half or all around; not smooth. 
3.2  Hectocotvlized arm 
Either left or right ventral arm is hectocotylized by modification into four sections, including the proximal- 
most non-suckered base of the arm (Fig. 2.2). The standard measure of arm length, including the 
hectocotylized arm, in squids is from the proximal-most sucker to the arm tip (Roper and Voss 1983). But 
because there is an area devoid of suckers along the base of the hectocotylized arm of 11 lex species, use of the 
standard method of arm length measurement would give a disproportionately short and misleading 
measurement. Therefore, the total length of the hectocotylized arm is measured from the very distinctive 
V-notch, formed where the bases of the two ventral arms are joined distally. to the distal tip of the arm. In 
Table 2.1 the value of the hectocotylized arm length index (HALtl) is given as total length of the 
hectocotylized arm as a percentage of mantle length. For purposes of comparison with material from previous 
studies, the value for the commonly used standard measure from proximal-most sucker to arm tip is given as 
HALsI, a value 7-10 percent smaller than the HALtl. The total length of the hectocotylized arm (HAD) of 
17 
mature males, measured from the V-notch, is about 67 percent (52-86 percent) of the mantle length (the small 
sample size from each area plus the possibility that some specimens might not be 100 percent mature, may 
account for the broad range). The fully formed hectocotylized arm is longer and more robust than its opposite 
arm IV, a feature that seems to occur on most specimens only in the last stage, as full maturity is attained. 
The base of the hectocotylized arm (HAb) is characterized by an area devoid of suckers from the V-notch 
between arms IVL and IVR to the first proximal sucker. The hectocotylized arm base (HAb) measures about 
13 percent (10-14 percent) of the HALt (index = HAbl). 
The proximal sucker-bearing section (HAD on mature males consists of 10-14 (mostly 10-12) suckers of 
normal configuration that like those on the opposite IV arm gradually increase in size distally, and it ends 
abruptly where the suckers distal to the last large, normal suckers are reduced in diameter by about one half; 
sucker rows are widely separated. This section (HA1) occupies about 27 percent (24-30 percent) of the HALt 
(index = HAtll) and about 31 percent (26-35 percent) of HALs (index = HAslI) measured from the proximal- 
most sucker. 
At the junction of suckered sections one (HA1) and two (HA2), the musculature of the arm is noticeably 
constricted for a distance of about two sucker pairs. This feature can be seen easily from the aboral as well 
as the oral surface of the arm, and it can be felt between the observer's fingers as an indentation, giving a 
reduced diameter to the arm. 
About 25 (22-29) small suckers occur along suckered section two (HA2); they terminate at the major 
modification of the arm tip, section three (HA3). The trabeculae on section two, beginning with the first 
reduced proximal sucker, are modified as round, fringed, papillose flaps that diminish in size distally and 
terminate with the last suckers on the dorsal and ventral rows (the end of section two). The dorsal and ventral 
protective membranes terminate two sucker bases distal to the last suckers. Section two (HA2) occupies about 
36 percent (34-38 percent) of the HALt (index = HAt2I) and 42 percent (38-43 percent) of the HALs (index 
= HAs21) measured from the proximal-most sucker. The junction between suckered section two and the distal 
tip of the hectocotylus generally is not as abrupt as between suckered sections one and two. Instead, it consists 
of a transitional zone that covers the distance of about two sucker pairs. 
The highly modified tip of the hectocotylus (HA3) is characterized by the loss of suckers and the 
development of lamella-like flaps and conical papillae. On the dorsal row are 1-2 conical sucker stalk bases 
without suckers, followed by about 23 (20-29) bases that are modified into flat, truncate lamellae. This row 
extends, with the lamellae decreasing in size, nearly to the arm tip, where the row terminates with up to 10-12 
minute papillae (possibly precursors of additional lamellae, if any more develop just prior to mating). The 
suckerless stalk bases on the ventral row, the papillae, maintain a conical, papillose shape and decrease in size 
to the tip, about 35 in number. These are about 50 percent as tall as the corresponding lamellae on the dorsal 
row. During growth, suckers occur on these bases, then are lost as the animal reaches sexual maturity. The 
sucker loss seems to occur towards the tips, i.e. proximal-most suckers are lost first as maturity progresses. 
The hectocotylized tip (HA3) occupies 26 percent (25-29 percent) of the HALt (index = HAt31) and 30 
percent (28-31 percent) of the length of the HALs from the proximal-most sucker (index = HAs31). The 
length of part three is directly dependent on the degree of maturity of the male, rapidly increasing as maturity 
increases. 
3.3 Mantle width 
The mantle width index (MWI) of mature males is 22 percent (19-27 percent) and of mature females is 
21 percent (14-26 percent). 
18 
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19 
3.4 Head width 
The head width index (HWI) of mature males is 23 percent (19-26 percent) and of mature females is 19 
percent (15-22 percent). 
3.5 Other characters 
Tables 2.2-2.7 present measurements and indices of several characters that can be used to compare the 
four species of Illex (from Roper et al. 1998). 
4    Discussion 
The broad, disjunct distribution of/, coindetii in the Mediterranean and amphi-Atlantic seas (Fig. 2.4) is 
characterized by a number of more or less distinct morphotypes. These sometimes highly variant forms (Fig. 
2.5) seem related not only to geographical distribution but to local or regional environmental factors as well 
(e.g. season, water mass, prey, etc.). The morphotypes are not well defined nor understood at this point. 
Because some of the morphotypes look so different from the "typical" /. coindetii from the Catalonian region, 
both in size and gross morphology, several workers have questioned the validity of using the specific name 
to apply to all forms. They suggest that several distinct species or subspecies exist in an /. coindetii species 
complex. 
Analysis of our data, as well as data available to us from other colleagues (e.g. C. Nigmatullin, 
AtlantiNIRO, Kaliningrad, Russia; A. Gonzales and A. Guerra, Institute de Investigaciones Marinas, Vigo, 
Spain; F. Zecchini, Universita di Pisa, Italy), leads us to conclude that /. coindetii is a single, widely 
distributed, highly plastic and variable species. However, underpinning the local variability appear to be two 
basic, consistent morphological forms. Based on indices of mantle width, head width, and hectocotylized arm 
length (see Table 2.1 and Fig. 2.5) and other aspects of the habitus of the animals, these two identifiable types 
conform to distributions in the Mediterranean Sea and in the Atlantic Ocean. Additional specimens are 
required from the Atlantic adjacent to the Mediterranean to define more precisely the forms, but our data 
suggest that these differences are consistent. Further comparative morphological analysis of additional material 
from the eastern and western Atlantic is required to clarify populational differences that exist across the range. 
We believe that molecular genetic analyses will also be required to help define populations. 
Although /. coindetii has been recorded from the Red Sea (Adam 1942), it seems unlikely that the species 
actually occurs there. The only two specimens recorded were captured in 1850 prior to the opening of the 
Suez Canal, so we concur with Lu (1973) that these specimens must have been mislabelled and that the species 
does not occur in the Red Sea. 
Adam (1952) reported /. illecebrosus specimens from the Bristol Channel off southwestern England. Re- 
-examination of some of Adam's specimens, especially of the hectocotylus and body and fin measurements, 
confirms that these specimens are /. coindetii, not /. illecebrosus (see Roper et al. 1998). 
In spite of the apparently high degree of variation in general habitus across the geographical range of /. 
coindetii, the characters associated with the hectocotylus in particular are surprisingly constant, as are, 
ultimately, the indices of head and mantle widths. For example, the males from Greece look very different 
from males from Namibia in general habitus. The Greek male looks more robust with broad mantle and head 
and very robust arms II and III, while the Namibian form appears thin with narrow mantle and head and 
non-robust arms II and III. Yet, when the details of the four-part hectocotylus are examined, they are 
strikingly similar, certainly well within the range of variability accepted for conspecific squid. Further, 
mature, mated females from Vigo, Spain, look much more robust in head and mantle width than their counter- 
20 
Table 2.2. Head length indices (HLI) and head width indices (HWI) 
for males and females of the four species of Illex 
Male Female 
Mean Range Mean Range 
HLI: 
/. illecebrosus 16.4 (10.6-24.7) 15.7 (11.4-22.6) 
I. coindetii 21.8 (13.7-29.6) 19.0 (10.0-23.6) 
I. argentinus 19.5 (16.0-23.9) 16.8 (14.3-19.7) ?- 
I. oxygoniiis 18.2 (15.0-21.3) 16.3 (12.9-18.6) 
HWI: 
/. illecebrosus 17.0 (10.0-21.8) 16.3 (12.9-20.4) 
I. coindetii 21.1 (13.2-29.1) 18.4 (12.9-25.1) 
I. argentinus 17.8 (11.8-21.1) 16.0 (11.7-18.8) 
I. oxygonius 20.0 (18.2-22.9) 17.5 (14.7-19.7) 
Table 2.3. Mantle width indices (MWI) for males ind females of 
the four species of Illex 
Male Female 
Mean Range Mear Range 
MW1I: 
/. illecebrosus 18.0 (15.2-23.1) 17.5 (13.9-26.0) 
I. coindetii 21.9 (13.7-27.6) 20.3 (16.9-28.0) 
I. argentinus 19.8 (14.3-24.2) 18.5 (15.4-21.7) 
I. oxygonius 18.7 (16.9-19.9) 17.7 (16.0-20.8) 
MW2I: 
/. illecebrosus 19.7 (15.7-29.1) 19.5 (15.2-28.3) 
I. coindetii 21.5 (15.5-30.1) 20.4 (14.7-28.8) 
I. argentinus 22.7 (18.7-27.1) 22.3 (18.5-26.5) 
I. oxygonius 16.4 (13.1-19.8) 17.8 (15.3-20.5) 
MW3I: 
/. illecebrosus 12.0 ( 8i2-19.8) 12.0 (9.2-19.3) 
I. coindetii 13.6 ( 8.7-22.8) 13.0 ( 7.6-19.9) ? 
I. argentinus 13.3 (9.8-17.1) 14.2 (9.6-22.1) 
I. oxygonius 10.9 (8.1-16.4) 10.8 (9.0-14.3) 
MW1 measured at mantle opening 
MW2 measured at mid- point between mantle opening and fin 
insertion 
MW3 measured at anterior point of fin insertion 
21 
Table 2.4. Fin length indices (FLI), fin width indices (FWI) and fin 
base length indices (FbLI) for males and females of the four species 
of III ex 
Male Female 
Mean     Range Mean    Range 
FLI: 
1. illecebrosus        43.8 (31.3-49.3) 44.1   (38.1-53.5) 
/. co;Wff? 39.2 (31.3-46.4) 39.4   (29.4-46.2) 
/. argentinus 41.9 (36.3-47.2) 42.3   (37.3-45.2) 
I. oxygonius 45.0 (42.0-47.9) 45.0   (42.5-48.1) 
FWI: 
/. illecebrosus 55.4 (43.0-64.2) 54.6   (40.9-65.8) 
/. coWff// 56.4 (45.7-66.5) 53.7   (37.0-65.9) 
/. a/-gg/;6'?Mf 58.0 (51.9-66.3) 56.4   (52.2-64.2) 
/. o-rygo/ww 51.5 (43.8-62.4) 50.5   (43.1-56.9) 
FbLI: 
/. ///fceArofMf        39.5 (28.4-44.3) 39.5   (33.8-50.3) 
/. coindetii 33.9 (19.3-40.7) 34.5   (25.0-41.6) 
/. argentinus 37.5 (35.2-43.0) 37.8   (34.4-40.3) 
/. ojygoN/wj 40.2 (35.8-42.4) 40.0   (37.9-43.2) 
Table 2.5. Arm length indices (ALI) (hectocotylus not included) for males and females of the four 
species of I Ilex 
/. illecebrosus /. coindetii /. argentinus /. oxygonius 
Arm Mean Range Mean Range Mean Range Mean Range 
Males: 
I 39.1 (25.5-56.0) 47.4 (27.1-77.4) 55.6 (45.8-65.0) 43.9 (35.2-53.3) 
II 48.2 (32.4-70.0) 62.5 (37.4-96.6) 70.2 (57.9-84.2) 54.8 (45.0-64.2) 
III 48.2 (32.4-70.3) 61.0 (37.6-95.9) 71.2 (52.5-86.4) 54.7 (43.8-63.0) 
IV 43.0 (27.5-62.9) 54.1 (29.3-87.8) 61.6 (42.6-74.4) 47.9 (39.4-60.6) 
Females: 
I 36.5 (29.2-49.3) 37.6 (25.0-56.1) 46.2 (39.3-53.7) 34.3 (27.9-39.3) 
II 44.5 (35.3-56.8) 48.7 (36.4-67.1) 57.4 (48.5-66.5) 42.9 (34.7-50.9) 
III 44.5 (34.7-57.6) 48.3 (36.4-67.7) 58.5 (47.1-70.0) 43.4 (36.5-54.0) 
IV 40.4 (29.4-52.6) 42.4 (25.0-63.5) 52.0 (43.4-59.7) 38.1 (31.9-46.0) 
22 
Table 2.6. Hectocotylized arm length" indices (HALsI) and hecto- 
cotylized tip length"3 indices (HAs3I) for mature specimens of the 
four Illex species 
Mean Range Standard 
deviation 
N 
HALI: 
/. illecebrosus 53.0 (39.7-66.0) 7.9 27 
I. coindetii 63.7 (42.3-87.1) 9.9 65 
I. argentinus 67.6 (49.5-82.0) 7.4 68 
I. oxygonius 51.5 (40.6-59.9) 5.7 10 
HA3LI: 
/. illecebrosus 22.1 (13.0-30.3) 4.6 27 
I. coindetii 25.1 (17.1-30.0) 2.7 65 
I. argentinus0 50.3 (19.8-70.3) 11.0 68 
I. oxygonius 28.8 (23.8-32.0) 2.7 10 
a
 Length of hectocotylized arm measured from most proximal 
sucker to arm tip. 
b
 Length of hectocotylized tip measured from most distal sucker to 
arm tip. 
c
 Includes HA2, which loses suckers at full maturity making it 
difficult to determine the junction point of HA2 and HA3. 
Table 2.7. Comparison of the beaks of the four Illex species3 
Feature illecebrosus coindetii argentinus oxygonius 
Upper Beak: 
Hood long, strong long, strong long, strong short, weak 
very thin 
Shoulder serrated smooth serrated smooth, straight 
or slightly curved 
Jaw angle large notch, 
with tooth 
small notch large, notch 
with tooth 
small notch 
Rostrum long long long short 
Lateral wall short, shallow: 
crest curved 
short, shallow; 
crest curved 
short, shallow; 
crest curved 
long, deep; 
' crest straight 
Wing short short short short 
Lower Beak: 
Jaw edge straight, short    straight, long       curved, long     curved, long 
Wing long, wide, long, wide, 
no lobe; no lobe; slightly 
regular outline irregular outline 
Lateral wall      short, blunt short, blunt 
Rostral width    narrow narrow 
long, wide, short, narrow 
no lobe; lobate; 
regular outline irregular outline 
short, blunt long, pointed 
narrow wide 
Based on Roper et al. (1969) and Lu (1973). 
23 
Figure 2.4. Geographical 
distribution of /. coinderii 
shown by hatched area; 
location of specimens used in 
this studv shown in solid dots 
-parts from the Gulf of Guinea. Certainly some of the variability can be attributed to small sample size and 
the possibility that some specimens are not 100 percent mature. 
Very large specimens, in excess of 250 mm ML. are occasionally captured. For example, large specimens 
are known from the Straits of Florida (male of 252 mm ML. female of 319 mm ML) and off Vigo. Spam 
(males to 270 mm ML. females to 370 mm ML: A. Gonzales. Institute de lnvestigaciones Marinas. Vigo. 
Spain, unpubl. data). These unusually large specimens of the species seem to represent a small proportion of 
the population and co-occur with more numerous, smaller, fully mature specimens Perhaps they are 
kite-hatching members of the previous year class that do not reach full maturity, and consequently do not 
spawn during their first year. They may survive through the winter until the following year, continuing to add 
to somatic growth, then the next season they mature at an unusually large size and spawn. This phenomenon 
was suggested for exceptionally large Loligo pealei in the western Atlantic as early as the last century by 
Verrill (1881). The key question is whether size at maturity is genetically or ecologically based. Would a little 
mature male he rejected, even eaten, by a very large female if he tried to mate with her? Genetic difference 
would be very rapidly reinforced if this were the case. 
The morphological changes observed in the growth of specimens during maturation are not isometric but 
allometric: the last-minute changes associated with maturation and spawning can be very dramatic. These 
changes probably occur in all areas and populations to one degree or another, but the changes that occur are 
not equally dramatic throughout the geographical range of the species. This phenomenon can account for a 
degree of the variation among the broadly dispersed populations. 
24 
Figure 2.5. Size morphotypes of 
fully mature males of /. 
coindedi, arranged geogra- 
phically from east to west; 
left to right in photo: 
Greece, Sicily, Barcelona, 
Namibia, Straits of Florida. 
The conditions discussed above now help us to understand why some workers questioned the single-species 
status of/, coindetii. That is, the different general habitus of animals from different geographical areas is not 
significant in terms of specific differentiation. It was the detailed analysis of a few distinctive morphological 
characters from representatives of populations across the whole range of the species that revealed that all these 
morphotypes, in fact, belong to one species. The question we cannot answer at this moment is: Why do these 
morphotypes exist and what sustains them? 
Particularly for identifications in the field, the easiest character to use to distinguish /. coindetii from the 
sympatric species of Illex in the western Atlantic, /. illecebrosus and /. o.xygonius, is the length of the 
suckerless base of the hectocotylized arm (HAb). In /. coindetii this sucker-free area occupies approximately 
13 percent of the total length of the arm, while in the other two species it amounts to only 6 percent and 4 
percent, respectively. In addition, the reduced diameter of the hectocotylized arm at the junction of the two 
suckered sections (HA1 and HA2) is clearly visible and can be felt with the fingers. No such reduction occurs 
in the other two species. The dentate and notched rings on the largest manal suckers of/, coindetii contrast 
with the smooth rings of the other two species, but a microscope, certainly a good hand lens, generally would 
be required to check this character in the field. 
5    Comparison of species 
While the purpose of this work is to define more precisely the systematics and distribution of /. coindetii, 
it is necessary to include basic information and data on the other three species of Illex, as well. Consequently, 
we include here Tables 2.2-2.7, which give measurements and indices of all four species, so their meristic 
characters can be compared. Figures 2.1-2.3 depict the measurements used. Further, a key (Table 2.8) to the 
25 
Table 2.8. Key to the species of Illex for mature adults 
1. Relative length of all arms long; tentacular club not broadly expanded, medial suckers very enlarged, 
lateral suckers extremely small; distal modified portion of hectocotylized arm greater than 50 percent 
of total arm length (= HA2 plus HA3); distribution restricted to western South Atlantic Ocean, 
23?-55?S        A argentimis 
Relative length of all arms moderate to short; tentacular club expanded, medial suckers enlarged, lateral 
suckers small (not radically disproportionate, as above); distal modified portion of hectocotylized arm 
(HA3) less than 33 percent of total arm length: North Atlantic. Caribbean, Gulf of Mexico, or 
Mediterranean       2 
2. Distal enlarged manal sucker rings notched, 7-8 low, broad, flat plate-like teeth; relative lengths of fins 
and fin bases short; relative length of head long; relative length of arms long; base of hectocotylized 
arm (HAb) devoid of suckers for 13 percent of total arm length; trabeculae on hectocotylus midsection 
(HA2) modified to papillose, fringed flaps; distribution pan-Atlantic, the only lllex species in the 
eastern Atlantic and Mediterranean     /. coindetii 
Distal enlarged manal sucker rings smooth, toothless, rarely with 1-2 notches; relative lengths of fins and 
fin bases long; relative lengths of head and arms short; base of hectocotylized arm (HAb) devoid of 
suckers for 4-6 percent of total arm length; trabeculae on hectocotylus midsection (HA2) not modified; 
distribution restricted to western North Atlantic    3 
3. Relative width of fins broad, 55 percent of mantle length; head length and width indices relatively low. 
16-17 percent; arm lengths relatively short in males, 39-48 percent of ML; arm sucker diameter 
indices relatively small, 1.02-1.75; hectocotylized arm equal to, or slightly shorter than, and the same 
thickness as, opposite arm IV; lower beak jaw edge straight, short; wing long, wide; lateral wall short, 
blunt; rostral width narrow   A illecebrosus 
Relative width of fins narrow, 51 percent of ML; head length and width indices relatively high, 16-20 
percent; arm lengths relatively long in males, 44-55 percent of ML; arm sucker diameter indices 
relatively large, 1.12-2.47, especially in males; hectocotylized arm relatively long, more robust than 
opposite arm IV; lower beak jaw edge curved, long; wing short, narrow; lateral wall long, pointed; 
rostral width wide   A oxygonius 
mature adults of all four species is included. Tables 2.2-2.8 are adapted from Roper et al. (1998), in which 
a detailed discussion of the systematics and distribution of all four species is presented. 
6    Conclusions 
Based on an analysis of some individual systematic characters in mature specimens of all four species of 
Illex, namely those associated with the hectocotylus and with head and mantle robustness, we conclude that 
/. coindetii is a single, variable, widely distributed species. We are unable to find sufficient morphological 
evidence in these character states to sustain the existence of a coindetii complex of closely related, distinct 
species. It is possible that future genetic analyses, in concert with morphological studies, might indicate 
specific status for some morphotypes, but that remains to be done. 
The morphotypes of the species that occur throughout the Mediterranean Sea and along the eastern Atlantic 
neritic zone from Great Britain to Namibia and in the western Atlantic from the southeastern Caribbean Sea 
the Gulf of Mexico and the Straits of Florida, all should be referred to /. coindetii. 
26 
In the western North Atlantic it is morphologically distinct from both /. illecebrosus and /. oxygonius in 
their region of sympatry. Further, it is quite distinct from the species in the western South Atlantic. / 
argentinus. 
Acknowledgements 
We wish to thank D. Levi, Director of the CNR - Istituto di Technologia delta Pesca e del Pescato (ITTP) in Mazara 
del Vallo, Sicily, for providing facilities and funding that enabled us to conduct this study. P. Jercb and S. Ragonese of 
ITPP hosted the working group and provided specimens and helpful discussions. P. Sanchez, Institute Ciencias del Mar, 
Barcelona, Spain, provided skillful leadership of the working group, as well as specimens and discussions. Specimens 
were kindly provided by N.A. Voss, Roscnstiel School of Marine and Atmospheric Sciences, Miami, FL; G. Bello, 
Laboratorio di Biologia Marina, Mola di Bari, Italy; A. Guerra and A. Gonzales, Institute de Investigacioncs Marinas, 
Vigo, Spain; S. Ezzedine-Najai, Institut National des Sciences des Techniques d'Oceanographic et des Peches (INSTOP), 
Salammbo, Tunisie; and E. Lefkathitou, Patras University, Athens, Greece. The manuscript was reviewed and valuable 
comments given by M. Sweeney, M. Vecchione and R. O'Dor. M. Sweeney also provided technical assistance with the 
manuscript. The comparative tables (Tables 2.2-2.7) and the key to the species presented in the manuscript arc taken with 
permission from a manuscript by C.F.E. Roper, C.C. Lu, and M. Vecchione, published in the Smithsonian Contributions 
10 Zoology; we acknowledge with appreciation the authors for granting permission to use these materials. I.H. Roper 
provided much assistance with the word processing and proofing. The first draft of the manuscript was prepared at the 
Smithsonian Marine Station Link Port (SMSLP), Ft. Pierce, FL, M. Rice, Director; this paper constitutes part of a 
long-term program there on systematics and distribution of ccphalopods; it is SMSLP contribution No. 321. We gratefully 
acknowledge all of these people and institutions. 
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