BIOLOGICAL RESULTS OF THE UNIVERSITY OF MIAMI DEEP-SEA EXPEDITIONS. 54. ON THE PRESENCE OF LIGHT ORGANS IN STEENSTRUP, 1887 (: CEPHALOPODA)l

S. V. BOLETZKY2 University of Miami, Rosenstiel School of Marine and Atmospheric Sciences

ABSTRACT The presence of light organs in the Rossia tenera (Verrill), R. equalis Voss, and R. patagonica Smith (R. tenera subsp. patagonica [Smith)), which together form the subgenus Semirossia Steenstrup, is stated in the present study. The organs are briefly described; their function as light orgall.s is mainly deduced from the anatomical similarity to those of other sepiolids, as observations on living are still lacking.

INTRODUCTION Although the presence of light organs in the mantle cavity of some species of Rossia has been mentioned and discussed in the past, the lack of such or- gans is generally regarded as a character of the monotypic subfamily Ros- siinae, in contrast to the other two subfamilies of the (Sepiolinae and Heteroteuthinae) which comprise numerous species equipped with light organs. During a cruise to the Caribbean aboard the R/V JOHN ELLIOTT PILLS- BURY of the University of Miami, in March 1968, I found light organs connected with the ink sac in specimens of Rossia (Semirossia) tenera (Verrill) trawled off Yucatan. Further investigations in the collections of the University of Miami Ros- enstiel School of Marine and Atmospheric Sciences and of the U. S. National Museum showed that light organs are always present in R. tenera (Verrill) and R. equalis Voss, as well as in R. patagonica Smith, which was referred to by Thore (1959) as patagonica (in the following, how- ever, this species is referred to under its old specific name, because of a dif- ference in the configuration of the suckers of the hectocotylus, ignored by Thore, that first has to be cleared up). The presence of light organs in R. patagonica has already been observed by R. E. Young and E. S. McSweeny, Jr., of the Rosenstiel School of Marine and Atmospheric Sciences. They kindly gave the abundant material to me for further examination.

1 Contribution No. 1190 from the University of Miami, Rosenstiel School of Marine and Atmo- spheric Sciences. This study was supported by National Science Foundation grant G B 5729X. This paper is one of a series resulting from the National Geographic Society-University of Miami Deep- Sea Biology Program. 2 Present address: Laboratoire Arago, 66 Banyuls-sur-Mer, France. 1970] v. Boletzky: Light Organs in Semirossia 375

ACKNOWLEDGMENTS I wish to give my sincere thanks to Dr. Gilbert L. Voss, Chairman of the Division of Biological Sciences of the Rosenstiel School of Marine and At- mospheric Sciences, as well as to Dr. Richard E. Young and Mr. Edward S. McSweeny, Jr., and to Dr. Clyde F. E. Roper of the U. S. National Museum for valuable advice and help in carrying out this study. I particularly ac- knowledge the assistance of my wife who performed all histological prepara- tions. During my work at the Rosenstiel School, I was the recipient of a post- doctoral fellowship of the Swiss National Fund for the Advancement of Sci- entific Research. All laboratory expenses were covered by National Science Foundation grant GB 5729X.

HISTORICAL RESUME Meyer (1906), in a note on the light organ of the Sepiolini, mentioned an inconspicuous swelling on the right side of the anus in Rossia macrosoma which, he supposed, was a reduced light organ. Chun (1915) and Sasaki (1920) described papilliform organs on either side of the rectum in R. mastigophora and R. bipapillata, respectively. Naef (1923: 575-76), in his monograph, mentioned both records and suggested that these organs might be rudimentary light organs, and that the second pair of papillae in the males of R. mastigophora, as described by Chun, might be rudimentary accessory nidamental glands. However, when characterizing the subfamily (Naef, 1912), he stated (1923: 573) that no light organs are present in the mantle cavity, but then (p. 574) he again described the differentiation of the front part of the accessory gland as a luminescent gland. These contradictory statements were evidently due to the uncertainty of whether or not the described organs really were light organs. Nevertheless, Naef appeared to have had a very precise idea about a conceivable pathway of formation or reduction of light organs in Rossia; he evidently supposed the presence of distinct light organs in Semirossia. In a free translation, his hypothesis (pp. 575-76) reads: "1 assume that Rossiinae with well-devel- oped light organs lived in greater depths. '" R. mastigophora then might be an intermediate form. Unfortunately, the entire subfamily is quite insuf- ficiently known. The situation in Semirossia, for instance, would be interest- ing as it is in some regards strikingly close to the Sepiolinae." As to the functioning of the light organs in Sepiolids, Meyer (1906) be- lieved that the organ was a gland producing a luminous secretion. Skowron (1926) was able to show that the luminescence was due to luminous bacteria dwelling in the organ. The function, anatomy, histology, and bac- teriology of these light organs are treated in Harvey's "Bioluminescence" 376 Bulletin of Marine Science [20(2)

(1952), based on numerous original investigations, the references to which are given there. MATERIAL AND METHODS The material examined included 36 specimens of R. tenera (Verrill) (14

ABBREVIATIONS USED IN ANATOMICAL DRAWINGS aa, anal artery la, artery to light organ ang, accessory nidamental gland ld, duct of light organ ct, connective tissue 10, light organ h, systemic heart lp, papilla of light organ la, artery of ink gland lv, vein from light organ id, ink duct rna, mantle artery ig, ink gland r, "reflector" kp, kidney papilla vc, vena cava I, "lens"

GENERAL MORPHOLOGYOF THE LIGHT ORGAN IN Semirossia The light organ of Semirossia is a bilobed body more or less surrounded by the anterior part of the ink sac; its position is transverse to the longitudi- nal axis of the , ventral to the ink duct (Fig. 1). In the four fresh specimens of Rossia (Semirossia) lenera, in which the organ was first observed by the author, its free part could be seen as a very light, whitish, transverse band on the ink sac (Fig. 1) when the mantle 1970] v. Boletzky: Light Organs in Semirossia 377

FIGURE 1. Fresh dissection of mantle cavity of female of Rossia tenera, ML 27.5 mm. Free part of light organ is visible on top of the ink sac. was slightly pulled back. After preservation, this striking aspect of the organ disappears as the transparent integument and "lens" tissue turn opaque; this might be the reason the organ has gone unnoticed in the past. In several small male specimens of R. tenera, the organ strongly protrudes into the mantle cavity on either side of the hindgut, and shows two bulbs 378 Bulletin oj Marine Science [20(2) 1970J v. Boletzky: Light Organs in Semirossia 379 •... 'u; -< ,5 Q) ~ '0.. c...o:! Q) -5..... o:!t: ..co:!•..• 0., Q) Q) •..•Q) 0 ••• Z<+-< o:! E~ E.e V)U •....• ~ '0 ...:IQ) ::E-5 Q)"!XI (;1:: Ei';;; , o:! <::l•.. •..Q) <:u Q) s::.e ~ ~ .d' ~o:! bJ) " •.. iXlO..•... E~ E:.:: v:] 0\ •..• •.••.• <+-< 0 ...:I",

~:9;::l .,)'.0 -Q) Eo:!.e•... <+-< <::l"0 •.. 0., <:u 0 s::•..• ~ I:: <::l 0 ';;; 0'" R:: -<" ..; ~ ~ ;::l ~" 380 Bulletin of Marine Science [20(2)

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FIGURE4. Different dispositions of the light organ on the ink sac, and variations in the type of duct, following the definitions given in the text: A, class 1 disposi- tion of the light organ, and ducts of type a (absence of papillae); B, class 2 dis- position, and ducts of type b (with papillae); C, class 1 disposition and type b; D, class 3 disposition and type b. (A and B are for females; C and D are for males. The symbols beside the drawings are also used in Figures 9 and 11). which can hardly be overlooked (Fig. 3, A). Even when not so evident, the organ often can be easily recognized by its appearance as an opaque struc- ture that hides the anterior part of the ink sac, uncovered by the renal ap- pendages of the kidney (Fig. 2). In large female specimens however, it often cannot be seen when the accessory nidamental glands and the nidamental glands extend far anteriorly and overlap the entire ink sac. The disposition of the light organ in its relation to the ink sac can be characterized arbitrarily by one of the three following classes: Class 1. The organ is so deeply embedded in the anterior part of the ink sac that its free part does not stand out against the sac; the organ, how- ever, does give the ink sac its peculiar heart shape (Fig. 4, A, C). Class 2. The greater part of the organ is surrounded by the ink sac, but two more or less distinct (but connected) lobes are uncovered (Fig. 4, B). Class 3. Only the base of the organ is embedded in the ink sac; the 1970] v. Boletzky: Light Organs in Semirossia 381

FIGURE 5. Rossia tenera, female, ML 21 mm, showing an unusual combination of type a (a duct to the accessory nidamental gland) and type b (a papilla into the mantle cavity). greater part forms two conspicuous bulbs protruding into the mantle cavity (Fig. 4, D). In R. equalis as well as in R. patagonica, only class 1 was found, whereas in R. tenera all three were observed. The question arises whether these different states are transitory or more or less persistent. As no retractor muscles can be recognized on the light organ itself or on the edge of the ink sac, it seems that these are persistent states. This means that the disposition might change once or several times in the lifetime of an animal, but not from moment to moment in the way that an iris contracts or dilates. Another varying character of the light organ, the significance of which is obscure, is the structure of the two ducts by which the light organ communi- cates with the mantle cavity. Two types of duct structure can be distinguished in R. tenera and R. equalis: Type a. The ducts open into the ventral fold of the accessory nidamental glands in female specimens (Fig. 4, A). Type b. The ducts always open directly into the mantle cavity by papil- lae in males and in females (except a) ; in this case no connection to the ac- cessory nidamental glands exists (Fig. 4, B-D). The only available female of R. equalis showed type a disposition. A very peculiar situation was found in two females of R. tenera from the ATLANTIS material (Fig. 11). One of them, with a dorsal ML of 21 mm, showed type 382 Bulletin of Marine Science [20(2)

Iv la

FIGURE 6. Blood supply to the light organ and ink sac in Rossia tenera: A, fe- male individual; B, male individual. a on the right side and type b, with an extraordinarily large papilla, on the left side (Fig. 5). The other female, with a dorsal ML of 23.5 mm, showed type a; but close to the tips of the accessory nidamental glands, there seemed to be rudiments of a papilla on either side. Histological sections showed that the ducts formed a curve at these points and came into close contact with the integument; this cannot be an artefact because of the absence of distor- tions in the surrounding tissue. The significance of this is, of course, quite uncertain, but it cannot be excluded that this specimen represents a transi- tional stage from a to b. In R. patagonica, all investigated specimens were of type b. The blood supply to the light organ is, as shown in Figure 6, derived from an artery that separates from the base of the posterior aorta, bifurcates into two branches (Ja) on either side of the hindgut, and also gives rise to the ink gland artery (ia). The arteries enter the light organ on the ventral side, close to the departing veins; the veins run into the anterior tips of the kidney mass formed by the renal appendages.

THE ANATOMY OF THE LIGHT ORGAN IN Semirossia The entire light organ of Semirossia is composed of principally the same parts as that of Sepiola: a central, voluminous, chambered part is embedded on the side of the ink sac in the so-called reflector; its free part is covered by the so-called lens tissue (Fig. 7). 1970] v. Boletzky: Light Organs in Semirossia 383 /d

FIGURE 7. Horizontal section through the light organ of the male of Rossia tenera shown in Figure 3, A. In this case, the organ is composed of two bulbs separated by the reflector and connective tissues. The latter are shown in detail at the lower right; the connective tissue continues as a thin membrane between the chambers of the organ.

The ducts, unlike the openings of the organ in Sepiola, start deep inside the chambered part (Fig. 8) on either side, and each one ends in an integu- mental papilla or, in most of the females of R. tenera and in one female of R. equalis, they run through the anterior part of the accessory nidamental gland and open into its ventral fold. In sections stained with Masson's Trichrome, the very compact reflector tissue is bright red and heavily stained, whereas in sections stained with hematoxylin-eosine there is no striking difference between the reflector and other tissues.

FIGURE8. Light organ of a male of Semirossia sp. The beginning of one duct is seen in the center of the chambered part of the organ. 384 Bulletin of Marine Science [20(2)

The lens-tissue components are connective-tis sue-like structures sur- rounding large, nonmuscular, fibrillar bundles, which stain light green and greyish, respectively, with Masson's Trichrome; they are not differentiated by stainir:g with hematoxylin-eosine. The cha::1bered part is originally certainly paired during ontogeny, but in almost 211 of :he females of R. tenera and in specimens of both sexes of R. patagonica 11 is unpaired. The :::ai~ chamber consists of more or less flattened smaller pockets; in the case or the unpaired organs, these pockets, by interdigitating, seem to have repl~ced the separating reflector and connective tissues that are still more or less completely present in the organs of the males of R. tenera and of both sexes of R. equalis. The chambers are filled, or at least coated, with a mass of very fine granules that seem to be luminescent bacteria; some are also found in the ducts. Varying in size, and always having a light central part, the granules look similar to secretion granules. However, they are never found inside the cells of the chamber.

DISCUSSION One of the questions remaining at the present time is whether the above- mentioned granules are truly luminescent bacteria. It will be definitely an- swered only after bacteriological investigations on fresh material. The great morphological similarity of the organ to that of Sepiola suggests, however, that a similar function is very likely. As to the differences in the organiza- tion of the light organ and its ducts in R. tenera, Figure 9 shows that neither a sexual dimorphism nor a distinct relation between the body size and the disposition of the light organ can be found. A possible cause of the observed variations could be a racial, subspecific, or even specific character. The material of R. tenera comes from ten dif- ferent locations on the Atlantic coast of Florida, the Gulf of Mexico, and the Caribbean (Fig. 10). Geographically, some grouping may be recog- nized, but its significance is rather doubtful because of the comparatively small number of specimens available. The ATLANTIS material (Atl.) from the north coast of Cuba is very homogeneous in the disposition of the light organs (Fig. 11); however, all specimens are females, with the mantle lengths ranging from 21 to 32 mm; all show the class 1 disposition. The Sombrero material (Som.) shows mainly the class 2 disposition in both sexes, with only one female differing (class 1); however, the sizes of the females (12 through 16.5 mm) are not comparable to those of the males (22 and 22.5 mm). Class 3 is found exclusively in the males (ML !5 through 24.5 mm) caught at one (G951) of the three stations off Yucatan (Cozumel); one male (ML 16 mm), from station P598, shows class 2; and the females (ML 1970] v. Boletzky: Light Organs in Semirossia 385 Rossia lenera Semirossia spec. Q A •\::j ~ • • • Ross/a equal/s • ..~ • S;Z• ,1=1 •..~ t::1 t1 Ross/a pala,gonica ~p 29 W,80 ~• '0 . k? 5 em t::1 dors. ML Q- \::j'\j a b QWIII_ 1 I}) ~fl.l ~ I'JI 1i!jf'4 ~lIifll 2 3 V "I/I'flII.. 5 em dors. ML

FIGURE 9. Relation between body size and disposition of the light organ in in- dividuals of Semirossia. The symbols are based on classes 1 through 3 of organ disposition and on types a and b of duct structure (see legend, lower right of figure; also text).

20.5 and 27.5 mm), from stations P598 and P602, show class 1. These and the other examples given in Figure 11 may show a certain tendency, but racial differences can hardly be established on the basis of the disposition of the light organ. It is conceivable that the described variations are due to different states of sexual activity. From the present material, no conclusions can as yet be drawn. 386 Bulletin of Marine Science [20(2)

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FrGURE 10. Map showing stations at which specimens of Rossia tenera (.) and R. equalis (0) were taken.

A transition in females from a state where the ducts end in the accessory nidamental glands (type a) to a state where a connection to the outside is formed by papillae (type b) can be imagined, as pointed out before. The inverse process is practically inconceivable. In spite of this, we generally find papillae in the smallest females, but not in the large ones. In the large fe- males, the ducts connect with the accessory nidamental glands (Fig. 9). And yet, we must assume that the organ is primarily connected to the accessory nidamental gland from which it is assumed to arise. The somewhat surpris- ing fact that the arterial supply of the entodermal ink gland and that of the ectodermal light organ are based on a common vessel (Fig. 6) should not be overemphasized. A primary connection of these organs is highly unlikely. It is evident that the knowledge of development in the embryonic and post- embryonic periods should give us essential information. As the species of Semirossia are apparently not present in shallow water, it will be difficult to obtain embryonic material. Although we can conclude from the investigated material that light organs are present without exception in Semirossia, future studies on more exten- 1970] v. Boletzky: Light Organs in Semirossia 387

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Or.2633 /90 375• d I=l Or. H6fi /25 ~ 21 24 28 Or 4858 /60 ~ ~ 39• Iro• 41 45 FIGURE 11. Disposition of the light organs in the specimens of Rossia tenera from the stations shown in Figure 10. sive material will be necessary in order to explain the observed morphologi- cal variations. SUMARIO SOBRE LA PRESENCIA DE 6RGANOS LUMINOSOS EN Semirossia Steenstrup, 1887 (~OLLUSCA, CEPHALOPODA) La presencia de 6rganos luminosos en las especies Rossia tenera (Verrill), R. equalis Voss y R. patagonica Smith (R. tenera subsp. patagonica [Smith]), que juntas forman el subgenera Semirossia Steenstrup, es expuesta en el pre- sente estudio. Los 6rganos son descritos brevemente; su funci6n como 6rga- nos luminosos se deduce, principalmente, de su similaridad anat6mica con los de otras sepi61idos, ya que todavia no se han hecho observaciones en ani males vivos. REFERENCES CHUN, CARL 1915. Die Cephalopoden. II. Teil: Myopsida, Octopoda. Wiss. Ergebn. Dt. Tiefsee-Exped. "Valdivia," 18(2): 405-552, pis. 63-95. HARVEY, E. N. 1952. Bioluminescence. Academic Press Inc., New York, xvi + 649 pp. MEYER, W. T. 1906. Ueber das Leuchtorgan der Sepiolini. Zool. ADZ., 30: 388-392. 388 Bulletin of Marine Science [20(2) 1908. Ueber das Leuchtorgan der Sepiolini. II. Das Leuchtorgan von Heteroteuthis. Zoo!. Anz., 32: 505-508. NAEF, A. 1923. Die Cephalopoden. Fauna Flora Golfo Napoli, Monograph No. 35, Teil I, Band 1, Lfg. 2, pp. i-xiv, 149-863. SASAKI, M. 1920. Report on the collected during 1906 by the U. S. Bureau of Fisheries Steamer Albatross in the Northwestern Pacific. Proc. U. S. natn. Mus., 57: 163-203. SKOWRON, S. 1926. On the luminescence of some cephalopods (Sepiola and Heteroteuthis). Riv. Bio!., 8: 236-240. THORE, SVEN 1959. Reports of the Lund University Chile Expedition 1948-49. 33. Cephalopoda. Lunds Universit. Arsskr., N.F., Avd. 2, Bd. 55, No.1, 19 pp.