John M. Arnold

MATING BEHAVIOR AND SOCIAL STRUCTURE IN LOLIGO PEALII

1. Observations of Loligo pealii have shown the egg mass can stimulate sexual behavior. This stimulus apparently has a visual basis.2. This stimulus is followed by establishment of a social hierarchy and by mate selection by the males. The males exhibit warning displays, sham battles, and mate protection during this time.3. Normally the females respond passively but occasionally they will take an aggressive role.4. This mating behavior results in copulation and egg-laying; thus a method for obtaining naturally laid eggs has been revealed.

ULTRASTRUCTURE OF A CEPHALOPOD PHOTOPHORE. II. IRIDOPHORES AS REFLECTORS AND TRANSMITTERS

The iridophores of one type of photophore of the deep sea squid, Pterygioteuthis microlampas were examined with the electron microscope and four different types were found. Three of these types have not been previously described. The regular iridophores of the posterior cup appear to be one-fourth wave length reflectors and redirect the light produced by the photogenic tissue outward. The regular iridophores of the anterior cap have a different spacing and platelet thickness so they apparently pass blue light. The irregular iridophores form a cone around the photogenic tissue and probably randomly reflect light back into the photogenic tissue. The iridophores of the lens have many precisely aligned iridosomes with platelet spacing and thickness so that they appear to collimate light passing through them. It appears that these three types of iridophores reflect, transmit and collimate the light produced in the photophore to match the background illumination hence making an efficient countershading mechanism. A fourth type of iridophore, the wide spaced iridophore, is rarely encountered and probably does not have a significant role in light attenuation in the photophore.

DEVELOPMENT OF THE CILIATURE PATTERN ON THE EMBRYO OF THE SQUID LOLIGO PEALEI: A SCANNING ELECTRON MICROSCOPE STUDY

1. Four types of beating ciliated cells, which appear at different times during embryonic development of the squid Loligo pealei, are described.2. The ciliated cells of the external yolk sac first appear during or at onset of organogenesis, as polygonal flattened cells in a pavement-like arrangement. The cilia of these cells are uniform in diameter and end in a blunt or slightly tapered tip. Their beat is asynchronous and uncoordinated, but unidirectional toward the vegetal pole. A large hemal space develops between these cells and the yolk syncytium of the external yolk sac. In later stages of development, when primary respiratory function is assumed by the gills (and probably the skin), the cilia on those cells develop a flattened paddle at or near their tips, which apparently is associated with coiling of the axonemes within them.3. Paddle-type ciliated cells develop on the embryonic body proper and are always isolated from each other except at the anterior edges of the mantle. These cilia beat unidire...

Fine structure of the development of the cephalopod lens

The development of the cephalopod lens involves migration and fusion of lentigenic processes which form a lens primordium which projects into the optic vesicle. The lens material is elaborated in the lens primordium and eventually the cytoplasm of the lentigenic processes is obliterated. Apparently the lens material forms from the content of Golgi vesicles which migrate from the cell body into the lens primordium. The role of the microtubules in this process is discussed.

ULTRASTRUCTURE OF A CEPHALOPOD PHOTOPHORE. I. STRUCTURE OF THE PHOTOGENIC TISSUE

One type of photophore of the deep sea squid Pterygioteuthis microlampas was examined with the electron microscope and its fine structure described. The photogenic tissue is composed of four cell types each with distinctive morphology which suggests their function. The photocytes branch and ramify throughout the central region of the photophore and have an extensive system of microvilli (the photogenic organelle) which are arranged about a central blood filled lumen. The photocytes apparently develop inside a sheath cell and are surrounded by a sheath which is continuous with the basement membrane of the blood vessels. The photocytes and associated sheath cells are surrounded by packing cells whose cytoplasm is replaced with a homogeneous granular material. Finally, cells containing many mitochondria branch and ramify throughout the photogenic area. Apparently the circulatory system is in direct contact with the photocytes, and acellular blood vessels, composed only of basement membrane, are found throughout the photogenic tissue. The similarity between photoproductive organelles and photoreceptive organelles is striking.