Contributions to Zoology, 65 (2) 65-77 (1995)
SPB Academic Publishing bv, Amsterdam
Systematic value of the ultrastructure of the sucker surface in the squid
family Mastigoteuthidae (Mollusca: Cephalopoda)
Mario Alejandro Salcedo-Vargas
Institute for Systematics and Population Biology, University of Amsterdam, P.O. Box 94766,
1090 GT Amsterdam, The Netherlands*
Keywords: Cephalopoda, Mastigoteuthidae, systematics, Northwest Pacific, suckers, ultrastructure
Abstract feeding brought Nixon & Dilly (1977) to the conclu-
sion that some of the sucker components defined as
involved in the mechanics ofintimate The ultrastructure of the sucker surface is described and its sys- pegs are con- tematic value for which bear minute mastigoteuthid squids, tact. They also proved that the growth of the sucker suckers, is considered. An introduction to sucker terms is given infundibulumtakes place at the periphery. and a redefinition of these terms is attempted. Using scanning Nixon & Dilly (1977) postulated that the differ- electron microscopic data, two genera and four subgenera of ences in diameter, size, and shape of sucker Mastigoteuthidae from the Northwest Pacific are distinguished. compo-
The presence of “cushions” in the sucker is discussed and con- nents in 10 cephalopod species depend on physiolo- sidered as a character important for understanding adaptations gy and behaviour. Nevertheless, the morphology of of cephalopods to the deep-sea. the surface of the sucker, its components and its
variations, chiefly in regard to minutesuckers, have
been ignored both as a taxonomiecharacterand for Résumé systematic purposes.
Studies of the suckers in Mastigoteuthidae have
L’ultrastructure de la surface des minuscules ventouses des been carried out by Chun (1910), Young (1972), Céphalopodes de la famille des Mastigoteuthidaeest décrite, sa Nixon & Dilly (1977), and Dilly et al. (1977), who valeur pour leur systématique étant discutée. Est proposée une focused their attention the chitinous : introduction on mor à la terminologiedes ventouses et un essai de rédéfi- ring nition de celle-ci est fait. L’utilisation des données obtenues à phology. A study of the ultrastructure of suckers, l’aide du microscope électronique à balayage permet de distin- using 310 mastigoteuthid specimens in the collec- dans guer le Pacifique du N.O. deux genres et quatre sous-genres tion of the Tokyo University of Fisheries, has been de Mastigoteuthidae.La présence de “coussinets” dans les ven- made in order to evaluate the systematic value of touses est discutée, et considérée comme caractère important
the and other sucker useful to pour comprendre les adaptations des Céphalopodes à la vie dans pegs components,
but and les mers profondes. distinguish not only genera also subgenera
even species (Salcedo- Vargas, 1993). During this
study, detailedobservations of the morphology of
Introduction suckers were carried out using the scanning electron
microscope (SEM). This extensive and detailed re-
Suckers are an important taxonomie character at search, which includes additional reference mate- familial, generic, and specific levels. The study and rial from the North Atlantic (loaned specimens,
of suckers use for classification was initiated by foreign collections, and unpublished material), as
Studies the suckers in well total of Naef (1921/23). on use of as a 250 micrographs, provides the
* Present address: Saginomiya Squid Research Laboratory (SSRL), 2F-2-4-11 Kami-Saginomiya, Nakano-ku, Tokyo 165, Japan. 66 M.A. Salcedo-Vargas - Ultrastructure of the sucker surface in Mastigoteuthidae
basis for the synthesis presented in this contribu- brane of a few species). Depending on the taxo- tion. Classification changes in the family Mastigo- nomie group, the sucker may develop relatively teuthidae, based partially on sucker morphology, muscular structures. A chitinous ring which varies are published in a separate paper (Salcedo- Vargas in shape, consistency, thickness, length, width,
is divided in and its This & Okutani, 1994) in which the family depth diameter, occurs at opening. ring two genera, each with two subgenera. consists of horny material, and usually develops
In the present paper, three aspects of suckers are denticles that are highly variable in shape and considered: (1) an attempt at a revision of sucker number. Ontogenetic modificationsof suckers into
the hooks and and terminology; (2) a description of morphological "cushions" (defined here), prob- ultrastructureof the tentacularand arm suckers for ably other structures are present in some groups. the taxa studied; and (3) a re-evaluationof the suck- The soft rings of octopod suckers do not develop er formations, here called "cushions", and of the horny rings or denticles, but develop soft cushioned sucker surface, and their respective systematic rings. value in the family Mastigoteuthidae.
Sucker surface Materials and methods
This is the area in which the main components The 310 specimens examined are all from the Northwest Pacific (acetabulum, infundibular ring, and papillated and are deposited in the collection of the Laboratory of Inver-
ring) are located. This surface varies in diameter ac- tebrates ofthe Tokyo University of Fisheries. The appearance of each of the subgenera defined can be observed in Salcedo- cording to the size of the sucker, its position in the
Vargas & Okutani (1994). arm and tentacular club, the taxa concerned, and
A JEOL JSM-T20 scanning electronic microscope (SEM) was the size of the specimen. used for observations of the ultrastructure. The samples selected were washed with distilled water and placed in the ultrasonic cleaner AUC-201 from 1 to 3 seconds. Dehydration with differ- ent concentrations of alcohol, changing the sample every hour Cushion from 65, 70, 80, 90, 95% and absolute, and later transferring into 3-metylbutyl acetate, made the sample ready for freeze dry- This soft is the single or multiple globular structure ing. The samples were mounted on stubs and gold-coated in the that out from the internal walls of the infun- ion sputter JFC-1100. grows
dibularring, chamber, veil, or the teeth in the arm
and tentacular suckers, particularly in some meso-
Sucker gross terminology bathypelagic squids. It has also been called hump
and lump (Chun, 1910; Sasaki, 1929). In hook-
The terminology of suckers as defined by Naef of of bearing taxa, the presence a horny-type
(1921/1923) and updated by Nixon & Dilly (1977) cushion has been observed. is used. Standardization and redefinition of some terms for the components of the suckers is given here. The updated and newly introduced terms are Terminology of sucker (sub)components illustrated and explained in detail. Line drawings of (Fig. 1) the re-evaluatedterminology are presented in Fig. 1.
Suckers have three main components (Fig. la, c).
These Sucker are: (1) the acetabulum, (2) the infundibular
ring, and (3) the papillated ring. Currently used
This is the cup-like, globular or helmet-shaped terms are discussed and newly introduced terms are
that is located structure mostly on oral surfaces of indicated in Table I. The sucker components con- the and tentacles the buccal follows: arms (and on mem- sist of subcomponents that are defined as - 67 Contributions to Zoology, 65 (2) 1995
blunt. In some taxa, there is a combination of two Table I. Sucker components and their names.
or more kinds of teeth.
Components 1st 2nd 3rd
Acetabulum Infundibular ring Papillated ring
Nomenclature. - The infundibular ring is usually
in two modes: extracted from the infun- Subcomponents analyzed
Polygonal it Stalk Teeth dibulum or embedded in it. In enlarged suckers, Sucker pad Veil process is normally attached just inside the infundibulum, Infundibular Pegs and it can be extracted easily by removing thepapil- chamber Rim lated ring (see third component). On the other
hand, in small suckers this ring is fragile and deeply
embedded in the acetabulum, and not easily ex-
tracted. in its the whole sucker 1st Component: acetabulum; subcomponents: stalk Therefore, analysis and sucker pad surface is examined.
When This meant the ring was given two names.
it is extracted from the acetabulum it calledthe The first component of the suckers in cephalopods was is the acetabulum, which is the primary structure horny ring. The second term used was the inner
others and which contains for when it is analyzed embeddedin the aceta- upon which the depend, ring, the main cavity of the sucker. The acetabulum is a bulum.
Nixon & the soft chamber composed of translucent or transpar- Dilly (1977) originally proposed
term to indicate the sucker opening ent tissue, and is globular, cup- or helmet-shaped. infundibulum
Haas It is attached directly to the oral surface of the arm as well as the ring, and were supported by
Therefore, in order to standardize the ter- which is supported by a stalk that can vary in archi- (1989). tecture, length and thickness. The sucker pad is also minology, another term can be used, viz., infun-
dibular all kinds of toothed smooth observed in some groups (Fig. lc). ring. Thus, or
extracted be called The size and architecture of the opening of the sucker rings, or not, may infun-
dibular acetabulum varies depending on the taxonomie rings.
moderate In arm an accessorial has group. In decapods it is usually to wide; suckers, subcomponent
of infundibu- in octopods it is generally narrow in comparison to developed from the internal side the the squid sucker surface. lar ring into the cavity of the acetabulum. This
structure is here defined as the veil, which varies in
size and shape from proximal to distal margin and
infundibular The veil is gives support to the ring.
overlooked in suckers because it 2nd Component: infundibular ring ( = horny ring, normally enlarged inner ring, chitinous ring); subcomponents: teeth, is narrow and attention is usually given to the teeth.
small veil is wide and veil, and infundibular chamber In groups with suckers, the
deeply embedded in the acetabulum (Fig. lc).
The of the veil and the infundibular The second component is the infundibular ring, morphology
in tentacular suckers of deca- formerly known as the horny ring, inner ring or ring some deep-sea
differs from chitinous ring. It is located on the sucker opening, pods and some sepiolid species slightly
it the standard In the sucker which is called here the infundibulum, and gener- morphology. some cases,
of called teeth neck in which ally bears several types protrusions, opening narrows abruptly, forming a
with the or denticles. the infundibularring is set, an opening at
distal lateral side. In the tissue of the The infundibular ring can be toothless, or others,
of the acetabulumis reduced and the infundibular de- "smooth", or have many teeth. The shape ring
to the com- an even wider veil. The weaker the covering teeth varies from group group,but most velops
the the and vice mon shapes are wedge-like, conical, slightly or tissue, more developed veil, versa.
for small tentacular the tissue clearly sharpened, short-rectangular, rounded, or Thus, suckers, cor- 68 M.A. Salcedo- Vargas - infrastructure of the sucker surface in Mastigoteuthidae
the is reduced The last the which in responding to acetabulum extremely component is rim, is con-
thin and the with the external of the to a very transparent membrane, and tact sub-ring papillated
veil turns into a complete infundibular(chitinous) ring. The rim is morphologically like the polygonal
chamber. processes and is usually overlooked in decapod
In the case of suckers which have modifiedinto suckers. In contrast, in octopod suckers the hooks and those that develop cushions, the infundi- cushioned rim is so large that it constitutes the bular ring is also modified. In these specific sucker main component of the sucker surface, in which types (hooked or cushioned), a chamber of horny case the papillated ring is poorly developed and material has developed inside the acetabulum and is located on the internal wall of the acetabulum from the infundibular ring, for which the term cavity (Fig. If). infundibular chamber is proposed. This term can
be used for the small tentacular suckers and for - Nomenclature. As with the infundibularring, a modified suckers (Fig. Id). variety of terms have been used (Table II). This
component was called the"outer ring" when it was
an unmodified ring, i.e., with flat and small poly-
3rd outer called the Component: papillated ring (= ring; gonal processes. It was "papillated area" papillated area); subcomponents: polygonal when referring to it independently as a structure or
and external when the in the processes (internal, intermediate, pegs were conspicuous or modified ring), pegs (adjacent denticles), and rim distal margin.
The third component, here called the papillated Table II. Names suggested by other authors for the papillated ring, is referred to as the "outer ring" by Nixon & ring and its subcomponents. and Dilly (1977) Haas (1989). It is located on the
Author Nomenclature periphery of the infundibulumand is in close con- tact with the infundibularring. The papillated ring Nixon & Dilly (1977) Cuticular surface consists of a series of three to eight independent Infundibular cuticle the number rings, depending on the group and the Kristensen (1977) (distal) Chitinous papillae Each ontogenetic stage. ring is formed by structural (proximal) Attachment ring which defined units were as thepolygonal processes (rim) Chitinous rib Nixon by & Dilly (1977). Every polygonal process Haas (1989) Polygonal platelets is in close contact with the others. The three sub- Horny coverings of the rings papillated ring can be namedas follows: Cephalopod literature in Outer ring the in one contact with the infundibularring can be general Papillated area called the internal ring ; the one between the sub-
the rings intermediatering-, and the one in contact with the rim the external ring (Figs, la, b).
In the center of each Results polygonal process a peg pro- trudes. Its and size varies in shape every sub-ring, but it can still be useful for identifying taxa and Ultrastructure of arm suckers
The introduced growing stage. term peg was by
Nixon & There The suckers = whole of Dilly (1977). are some enlarged pegs ( structure) Mastigoteuthi- in the distal of the dae in the Mor- margin internal ring of some are aligned two rows along arms.
and those into main taxa, pegs are defined here as adjacent phologically they are clearly divisible two denticles (Fig. 3). The pegs can be globular, drop- types: (1) small, elongate and strongly dentated; or stalactite-like. For detailsabout their formation, (2) large, globular, and with nearly smooth infun- see Nixon & Dilly (1977) and Haas (1989). dibular rings. - Contributions to Zoology, 65 (2) 1995 69
Fig. 1. Sucker components and subcomponents terminology: a, surface of arm sucker; b, surface of tentacular sucker; c, arm sucker, lateral view; d, tentacular sucker, lateral view; e, cushioned sucker, cross section; f, example of octopod sucker, cross section. 70 M.A. Salcedo-Vargas - infrastructure of the sucker surface in Mastigoteuthidae
Arm sucker type 1 (< 50 mm ML), but in larger ones (> 100 mm ML)
the distal suckers. (Figs. 2-3) they are observed mainly in
This type of sucker typically has papillated rings Remarks. - This kind of sucker occurs in the genus with three rings of polygonal processes with pegs Mastigoteuthis. In M. agassizi (Verrill, 1881) the
Their and denticles than in M. projecting from the surface. shapes adjacent are more conspicuous
with their the infundibulum M. forms vary position on famelica Berry, 1913, or glaukopis Chuil, 1910,
(Nixon & Dilly, 1977). The size, shape and number which bear fewer and blunter teeth. of polygonal rings also vary depending on the size of the specimen and the position of the sucker on the arm. Arm sucker type2
(Figs. 4-7)
Acetabulum. - The outline is elongate, helmet- shaped, and its opening is moderate in large speci- The second typeof sucker is larger, globular, some-
The times in the middle of the with mens (mantle length [ML] > 90 mm). stalk, enlarged part arm, which is based on a small and blunt sucker pad, is weakly dentated or smooth rings. The architecture thin and short. of the sucker surface in this type is more uniform
than in the first type of sucker discussed.
Infundibular — The of ring. number teeth ranges from 6 in specimens smaller than 50 mm ML to 18 Acetabulum. - The outline is globular, its opening in mature specimens of 150 mm ML. The teeth are is large in both small and large specimens. The distributed along the distal margin and are coni- suckers are enlarged in arm III. The stalk is moder- cally sharp in its center, gradually becoming wider ately thick and short, projecting from a blunted and blunter toward the proximal margin where the sucker pad. surface is nearly smooth (Fig. 2). The veil is large, especially in suckers from the middle to the prox- Infundibularring. - The teeth in small specimens imal part of the arm. (< 100 mm ML) are visible in all suckers. Their
from to number ranges 4 16. In large specimens
Papillated ring. - The size and width of the pegs (> 150 mm ML), the infundibular ring gradually change from the internal to external ring. In the in- becomes smooth or with swollen areas, especially in ternalring at the distal margin, the pegs are slender proximal suckers (Fig. 4). The teeth are rounded or
in and tall, and the proximal margin they are much blunt (Fig. 5). The veil is moderate to large. stouter, occupying a larger portion of the base of the process (Nixon & Dilly, 1977). The pegs at the Papillated ring. - The sucker surface consists of distal margin of the intermediate and external rings three to seven rings of flat polygonal processes in are in reduced height, but wider thanthe ones of the Idioteuthis magna (Joubin, 1913) (Figs. 4, 5). In internal the the ring. At proximal margin pegs are I. cordiformis (Chun, 1908), the polygonal pro- reduced in size, hence some sucker surfaces are cesses are rounded and slightly globular (Figs. 6, 7). completely flat. Slender, elongated and flat pro- The size and width of the polygonal processes cesses border the sucker surface in the periphery change from the internal to the external ring. The
(Fig. 3). pegs of intermediateand external rings at the distal
The denticles adjacent (modified pegs in the dis- margin are reduced in size, but there is no signifi- tal toward the difference the of margin) point periphery, and their cant among rings polygonal pro-
face is curved and than that of the which proximal taller cesses, are completely flat (Fig. 7). proximal margin, which barely rises above the level
of the The - base (Fig. 3). adjacent denticles are Remarks. This typeof sucker occurs in the genus present in almost all suckers in small specimens Idioteuthis (Figs. 4-6). It is observed that sucker Contributions to Zoology, 65 (2) - 1995 71
2 3
4 5
6 7
Figs. 2—7. Arm suckers: 2, Mastigoteuthisagassizi, proximal sucker, arm IV (80 x ); 3, M. agassizi, detail of the pegs, teeth and adjacent denticles of the distal margin (800 x ); 4, Idioteuthis magna, proximal sucker, arm II (80 x); 5, I. magna, close-up of the teeth and polygonal processes of the distal margin(400 x); 6, I. cordiformis, medial sucker, arm II (60 x ); 7, I. cordiformis, detail of the poly- gonal processes of the proximal margin (800 x ).
morphology may change in the same individual in large specimens. Nevertheless, the general pat- from to from to terns of arm arm, even row row, especially the polygonal processes remain constant. 72 M.A. Salcedo-Vargas - Ultrastructure of the sucker surface in Mastigoteuthidae
of the rim Ultrastructure of tentacular suckers tentacular stalk. The outer surface is en-
larged, especially at the lateral margins (Fig. 9). The
The tentacular suckers show a morphological pat- externalring has truncate and round pegs. The 3 to tern closely related to that of arm suckers. The ten- 4 pegs at the distalmost corner of the notched ring
the tacular clubof the Mastigoteuthidae shows 12 to 30 are modified, allowing the suckers to make or more rows of suckers around the stalk, with the "close-open" movement (the "close-open" move- aboral side remaining free of suckers. The suckers ment is a hypothesis based on observations of are characterized by their minute size. Morphologi- preserved suckers and deduced from the specific
of in distal cally they are also divided into two types: (1) elon- morphology the pegs the margin) (Figs.
sucker infun- gate surface, sharp pegs, dentated 9, 10). dibular rings; (2) round sucker surface, smooth in- The intermediate ring has conical and slightly fundibular ring. wedge-shaped pegs that are larger than those of the
external ring. In its distal margin, 3 to 4 very sharp
of pegs about the same size are present. On both
Tentacular sucker type 1 lateral margins of the internal ring, 2 to 3 irregular
(Figs. 8-10) and enlarged wedge-shaped pegs are present and
they project into the aperture of the sucker. In the
This type of sucker is disto-proximally elongated, proximal margin, 2 to 3 plate-like polygonal pro-
two to of with three types pegs in the genus Masti- cesses can be observed (Fig. 9). goteuthis (Figs. 8, 9).
Remarks. - It was observed in large specimens of
Acetabulum. - The outline is elongate. The open- Mastigoteuthis (> 160 mm ML) that the pegs are ing is moderate. The acetabulum is extremely re- longer and sharper, but the size of the sucker is not duced is attached than in to a transparent membrane, and larger juvenile specimens. This is especially to the tentacle by a very thin and elastic stalk. evident in M. famelica (Berry, 1913).
Infundibularring. - The teeth only appear in the distal and margin are square in shape, their number Tentacular sucker type 2 ranging from 3 to 5. The infundibularchamber is (Figs. 11-13) as big as the papillated ring, but in large specimens the infundibular chamber is elongate and larger The tentacular suckers in Idioteuthis are spherical than the papillated ring (Fig. 9). in shape, and nearly all the pegs are of a similar
circular type. The sucker surface looks in the proxi-
- This consists of three sub- and the the Papillated ring. ring mal-distal plane, arrangement of pegs rings. In juvenile specimens (50 to 70 mm ML) or is nearly radial. in the distal suckers of mature specimens (150 mm
ML), the arrangement of the polygonal rings is Acetabulum. - The outline is spherical, and its
without be- is thin and nearly radial, apparent differentiation opening small. The stalk moderate to
the of the for 300 tween shape pegs in each ring, except long. In large specimens of I. cordiformis (> the size. The internalring has larger, slightly ovate mm ML) the suckers in the proximal part of the ten- pegs, while the intermediatering has smaller, circu- tacles are as big as the distal suckers of arm I. On lar ones, and theexternal ring has still smallerpegs. theother hand, for I. magna itis possible to observe
Distal suckers in the process of formation have the sucker's face in detail only by using TEM or elongate pegs (Figs. 8, 9) in the external ring. SEM.
The in pegs mature specimens are better devel-
oped - and differ clearly depending on the ring, par- Infundibular ring. The ring has no teeth in I.
in the suckers the of ticularly on middle part of the magna (Fig. 12), but in I. cordiformis a type Contributions to Zoology, 65 (2) - 1995 73
8
9
10 11
12 13
Figs. 8-13. Tentacular suckers: 8, Mastigoteuthisglaukopis(400 x); 9, M.famelica(800 x); 10, M.famelica, aspect showing the hypo- thetic “close-open” movement of the papillated ring (80 x); 11, Idioteuthis cordiformis, distal sucker (160 x); 12,I. magna (1200 x);
I. detail of the of the 13, magna, pores pegs (6000 x). 74 M.A. Salcedo-Vargas - Ultrastructure of the sucker surface in Mastigoteuthidae
blunt teeth are present along the margins (Fig. 11). cushion grows out from the infundibulum, giving it
and the chamber is the of A short neck between the ring appearance a boxing glove (Fig. 19). evident. The infundibular chamber is spherical.
Papillated ring. - Three sub-rings are also present. Discussion
of small and The pegs the external ring are very closely attached to the intermediatering, giving the Sucker terminology appearance that there are only two sub-rings (Figs.
11, 12). The internal ring of I. cordiformis has The indiscrimate use of terms in the naming of
and than the intermediate sucker when is larger more ovate pegs components, especially SEM used, ring. The internal ring of I. magna has fewer pegs, leads to misunderstandings or failures in the de- which are nearly circular in shape, while the inter- scriptions of sucker morphology in taxonomie con- mediate ring has larger pegs that are clearly poly- tributions. The purposeof introducing this revised gonal in shape (Figs. 12, 13). terminology is to provide standardizeddescriptions
of the morphology of suckers. First, this is neces-
Remarks. - In large specimens of I. cordiformis sary in the family Mastigoteuthidae and in taxa
(> 300 mm ML), the suckers increase in size, in the which have a closely related sucker morphology, as middle part of the tentacle in particular. well as in paralarval specimens of all groups of
squids, in order to understand their ontogenetic
changes and phylogenetic relationships. Second, it
Ultrastructure of cushions is expected that this terminology may help in the
(Figs. 14-19) description of all cephalopod suckers.
Cushions are cushion-like structures present in arm and tentacular suckers, characterized by their glo- Identification by suckers and its systematic value bular shape and softness. They are formed mainly in of veil infundibular the internal walls the or the The use of sucker morphology for species discrimi- chamber. nation with Morphologically, they are very variable, has occurred in very limited cases re- their size and number varying in every single suck- gard to small suckers, this probably being dueto the er. However, two types of cushions are recogniz- need of re-evaluation of sucker morphology and able: (1) the spongy-type, usually soft, commonly terminology. For example, Young (1972) defined
in tentacular present suckers; and (2) the horny- the species Mastigoteuthis pyrodes by the structure
in suckers. of its tentacular the first who type, usually present arm suckers. Young was
The cushionof tentacularsuckers is formed from evaluated the morphology of mastigoteuthid tenta- the internal walls of the infundibularring. Its size cular suckers, although considering the pegs as
depends on the species and size of the specimen. In teeth. Nesis (1977) believed the use of tentacular
cushions in the size Mastigoteuthis, are present mainly sucker to be the only way to separate mastigo-
of the middle of the tentacle. The teuthid based observa- suckers part species, on Young's (1972) cushion usually is present in the proximal margin. tions. It is stated here that the morphology of the
The appearance of the sucker cushion differs from papillated ring makes the identification of para- sucker to sucker (Figs. 14, 15). larvae as well as adults more reliable.
In Idioteuthis, cushions are only present in I. cor- Additional SEM studies in which tentacular diformis, in which the suckers order to cushion grows first internally were described in definespecies are around the infundibularring (Figs. 17, 18), detach- those by Okutani & Horita (1987) on two species of
the ing papillated ring or the ring being covered by Euprymna, and by Okutani & Takayama (1991) on the cushion, so that just the infundibularchamber two species of Sepiola from Japanese waters. These and cushion remain the (Fig. 16). Occasionally, the examples support the idea proposed here that the - Contributions to Zoology, 65 (2) 1995 75
14 15
16 17
18 19
Figs. 14-19. Spongy-type cushions: 14, Mastigoteuthisagassizi, on tentacular sucker (600 x); 15, M. famelica, on tentacular sucker
(1500 x); 16, Idioteuthis cordiformis, generalview of the cushions in proximal tentacular suckers (16 x); 17, I. cordiformis, sucker
modified by the cushion (120 x); 18, I. cordiformis, variation in the development of the cushion in tentacular suckers (80 x);
19, I. cordiformis, the most enlarged sucker, showing the probable last step in the development of cushions in this species (28 x). 76 M.A. Salcedo- Vargas Ultrastructure of the sucker surface in Mastigoteuthidae
Joubin with systematic value of the sucker surface, specifically was originally reported by (1895) re-
the papillated ring which is the main component in gard to the family Chiroteuthidae. Pfeffer (1900)
small suckers, is important not only for mastigoteu- considered cushions to be an unusual condition.
thid species but also for other cephalopod taxa with Chun (1910) attempted to explain cushion forma-
suckers such and tion the of Chiroteu- small as Sepiola Euprymna. by examining type specimen
In Northwest Pacific material of Mastigoteuthi- this picteti (Joubin, 1894) and described the forma-
dae, the subgenera Mastigoteuthis, Echinoteuthis, tion of hump-shaped thickenings inside the aceta-
Idioteuthis, and Magnoteuthis could be distin- bulum. Similar formations were observed in other
guished by their sucker components (Salcedo- suckers by Chun (1910), who concludedthat it is the
last of series of modi- Vargas, 1993; Salcedo-Vargas & Okutani, 1994). stage a probably pathological
Emphasis has been placed on the papillated ring as fications. The fusion of the swellings and the den-
a new taxonomie character for the taxa studied, be- ticles led Chun to the conclusion that this is a rare,
cause in small-sized suckers the infundibular ring abnormal dentition.
gets secondary taxonomie value and the papillated Chun (1910) also noted closely related structures
ring takes its place as the main component of the in the suckers of M. cordiformis Chun, 1908 (now
sucker surface. This re-evaluation of sucker com- Idioteuthis). Later, in the description of I. latipinna
ponents is likewise important for thereconstruction (= I. cordiformis), Sasaki (1916) defined similar
of phylogenetic relationships, and can be helpful in structures as "lumps of irregular shape". Sasaki
the process of identificationof undescribed sucker (1916, 1929) also thought that cushions were patho-
components in other cephalopod taxa. logical malformations.
Detailed examination and cross section views
(Fig. le) of cushions in suckers of Mastigoteuthidae
Cushion re-evaluation from the Northwest Pacific shows that the spongy
cushion material is differentfrom the horny mate-
Structures like rings, teeth, and other subcompo- rial. Further investigations of their respective chem- nents of suckers are of extremely variablebiochemi- ical compositions are needed. Biologically, the cal The re-evaluationof the cushioned composition. cushions should not be considered as pathological suckers in the present paper suggests that there is a formations, but rather as adaptations, probably to transformationof the horny ring protein structure deep-sea life. into a differentprotein. This demands a revision of The reason why such a formation has not been the taxonomie study of suckers, primarily in the discussed in depth earlier, and why cushions have
Mastigoteuthidae. never been subjected to taxonomic/phylogenetic
Inorder evaluate follow- to the cushions as an important character analysis may be attributedto the
of observe subcomponent sucker morphology, it is neces- ing causes: (1) infrequent opportunity to
of sary to understand that suckers are structures in specimens with cushions, (2) low accessibility constant transformation, such as the well-known complete tentacles of adult specimens, (3) frequent transformation from ordinary suckers into hooks, loss of sucker rings in many specimens, (4) irregular which in cushion and of is currently an accepted phenomenon. Many patterns formation, (5) presence families, genera, or species have been described remnants of teeth in spite of the complete forma- based on the shape, size and number of hooks. tion of cushions.
Engeser & Clarke (1988) summarizedthe morphol- The presence of cushions is not exclusive to this
and evolution of in- ogy fossil and recent hooks, particular family, as they were also observed in
dicating the importance of their chemical composi- Chiroteuthidae (Joubin, 1895), Joubiniteuthidae, tion. has However, nothing been documentedabout and Grimalditeuthidae, and in more distantly- the cushions. related families such as Bathyteuthidae, Lepido-
The cushions are considered here as another kind teuthidae, Pholidoteuthidae and Octopoteuthidae of transformationfrom ordinary suckers, in addi- (personal observations). tion teeth and hooks. This for to particular structure The cushions cannot yet be classified or used Contributions to Zoology, 65 (2) - 1995 77
systematic purposes, since they do not show a con- matics. Abh. naturwiss. Ver. Hamburg., (NF) 28: 165-185. sistent formation. For the time Joubin, L., 1895. Contribution à l'étude des Céphalopodes de pattern of being l'AtlantiqueNord. Résuit. Camp, scient. Prince Albert I, 9: they can be considered simply as a character useful 1-63, pis. I-IV. for identifying lifestyle and age. Kristensen, Th.K., 1977. Scanning electron microscopy of hook
At the moment, the of cushions as a presence development in Gonatus fabricii (Lichtenstein, 1818) (Mol- structure derived from the internal walls of suckers lusca: Cephalopoda). Vidensk. Meddr. dansk naturh. Foren.,
140: 111-116. with well-developed veils or infundibularchambers, Naef, A., 1921-1923. Cephalopoda. Fauna Flora Golfo Napo- suggests that this is a common feature in sexually li., 35(1): 1-863; (2): 1-357 (translated from the German; mature bathypelagic cephalopods. Israel Program for Scientific Translations, Jerusalem, 1972).
Nesis, K.N., 1977. Mastigoteuthispsychrophila sp. n. (Cephalo-
poda, Mastigoteuthidae) from the Southern Oceans. Zool.
Acknowledgements Zh., 56(6): 835-842.
Nixon, M. & P.N. Dilly, 1977. Sucker surfaces and prey capture.
In: M. Nixon & J.B. Messenger (eds.), Biology of cephalo- I am grateful to Dr. Takashi Okutani of the Tokyo University pods. Symp. zool. Soc. London, 38: 447-511 (Academic of Fisheries for his supervision of my doctoral dissertation and Press, London/New York). for his corrections in the present paper, and to Captains and Okutani, T. & E. Horita, 1987. Identity of Euprymna berryi crews of the R/V's "Kaiyo-Maru" and "Kotaka-Maru",aswell Sasaki, 1929 (Cephalopoda, Sepiolidae). Venus, Jap. J. as scientists on board for their great efforts in sampling the bio- Malac., 46(2): 91-107. logical specimens on which this study was based. To Dr. Hiroshi T. & Okutani, K. Takayama, 1991. The Sepiola parva and S. Saito (NationalScience Museum, Tokyo) for his assistance and birostrata problem. Bull. mar. Sci., 49(1-2): 666 (Abstract). helpful advice in the use ofthe Scanning Electron Microscope. Pfeffer, G., 1900. Synopsis der oegopsiden Cephalopoden.
To Prof. Dr. S. van der Spoel of the University of Amsterdam Mitt, naturh. Mus. Hamb., 17: 147-198. for his comments on this paper and for the opportunityto study Salcedo- Vargas, M.A., 1993. Revision of the squid family in his laboratory. Fruitful comments by anonymous reviewers Mastigoteuthidae (Mollusca: Cephalopoda) from the North- are also acknowledged. west Pacific: 1-264 (Doctoraldissertation, Tokyo University
of Fisheries).
Salcedo-Vargas, M. A. & T. Okutani, 1994. New classification
Literature cited of the squid family Mastigoteuthidae(Cephalopoda: Oegop-
sida). Venus, Jap. J. Malac., 53(2): 119-128.
Sasaki, M., 1916. Notes on oegopsid cephalopods found in Chun, C., 1910. Die Cephalopoden. Wiss. Ergebn. dt. Tiefsee- Japan. Annotationes zool. jap., 9(2): 89-120, pi. III. Exped. "Valdivia", 18 (1, Oegopsida): 1-401, pis. I—II, Sasaki, M., 1929. A monograph of the dibranchiate cephalo- I-LXI [English translation, Israel Program for Scientific pods of the Japanese and adjacent waters. J. Coll. Agrie. Translations, vol. 18 (1975): 1-552, atlas of 95 plates]. Hokkaido Imp. Univ., 20 (Suppl.): 1-357, pis. I-XXX.
Dilly, P.N., M. Nixon & J.Z. Young, 1977. Mastigoteuthis - the Young, R.E., 1972. The systematics and areal distribution of whip-lash squid. J. Zool., Lond., 181(4): 527-559. pelagic cephalopods from the seas off southern California. Engeser, T.S. & M.R. Clarke, 1988. Cephalopod hooks, both Smithson. Contrib. Zool., 97: 1-iii, 1-159. recent and fossil. In: M.R. Clarke & E.R. Trueman (eds.),
The Mollusca, vol. 12. Paleontology and neontology of
cephalopods: 133-151 (Academic Press, San Diego).
Haas, W., 1989. Suckers and arm hooks in Coleoidea (Cephalo- First draft received 14 April 1994
poda, Mollusca) and their bearing for phylogenetic syste- Revised: 8 May 1995