Richard N. Mariscal

The nature of the symbiosis between Indo-Pacific anemone fishes and sea anemones

Under the general heading of symbiosis, defined originally to mean a “living together” of two dissimilar species, exist the sub-categories of mutualism (where both partners benefit), commensalism (where one partner benefits and the other is neutral) and parasitism (where one partner benefits and the other is harmed). The sea anemone-fish (mainly of the genus Amphiprion) symbiosis has generally been considered to benefit only the fish, and thus has been called commensal in nature. Recent field and laboratory observations, however, suggest that this symbiosis more closely approaches mutualism in which both partners benefit to some degree. The fishes benefit by receiving protection from predators among the nematocyst-laden tentacles of the sea anemone host, perhaps by receiving some form of tactile stimulation, by being less susceptible to various diseases and by feeding on anemone tissue, prey, waste material and perhaps crustacean symbionts. The sea anemones benefit by receiving protection from various predators, removal of necrotic tissue, perhaps some form of tactile stimulation, removal of inorganic and organic material from on and around the anemone, possible removal of anemone “parasites”, and by being provided food by some species of Amphiprion.

Protection of the hermit crab Pagurus pollicaris say from predators by hydroid-colonized shells☆

Abstract Only one study has shown that a hydroid-colonized gastropod shell was a deterrent to predation on hermit crabs. In the present study, the hydroid-colonized shell protected the hermit crab Paguruspollicaris Say from the shell-crushing stone crab Menippe mercenaria (Say) and the non-shell-crushing octopus Octopus joubini Robson. The shell-crushing calico crab Hepatus epheliticus (Johansson) was not deterred, however, by a hydroid-colonized shell.

THE DEVELOPMENT OF A SEA ANEMONE TENTACLE SPECIALIZED FOR AGGRESSION: MORPHOGENESIS AND REGRESSION OF THE CATCH TENTACLE OF HALIPLANELLA LUCIAE (CNIDARIA, ANTHOZOA)

Three intermediate catch tentacle morphs were observed in the sea anemone Haliplanella luciae during catch tentacle development. Stage 1 catch tentacles, characterized by swollen bulb-like regions along their length, were histologically similar to feeding tentacles. Stage 2 catch tentacles, which tapered normally along most of their length and then constricted near the tip, were characterized by the presence of feeding tentacle cnidae in the tentacle coelenteron as they were removed from developing catch tentacles. Numerous cnidoblasts appeared in stage 2 tentacles and then synchro nously matured into small holotrich nematocysts, a cnida characteristic of mature catch tentacles. Stage 3 catch tentacles were characterized by the appearance of many large holotrich nematocysts. Such tentacles appeared similar to mature catch tentacles with wide, opaque, blunt tips. However, stage 3 catch tentacles had fewer large holotrichs per total tentacle cross section than mature catch tentacles. The numbers of large and small holotrich nematocysts decreased in regressing catch tentacles, which tapered to opaque, pointed tips. However, these cnidae did not move to the coelenteron as before but instead migrated to the epithelial surface. This migration suggested that they were externally expelled from the tentacles.

The utilization of cnidarian nematocysts by aeolid nudibranchs: nematocyst maintenance and release in Spurilla

Some nudibranchs that feed on cnidarians are known to store nematocysts within cnidophage cells and use them for their own defense. Most of the nematocysts are in direct contact with the cytoplasm of the cnidophage. Nematocysts are not subjected to lysosomal enzymes because any phagocytic membrane that surrounded the nematocyst after engulfment does not persist. Cnidophage organelles are restricted to regions surrounding the nematocysts and may aid in the maintenance and development of the nematocysts. The release of cnidophages is initiated by a contraction of a dense muscle complex surrounding the cnidosac. Nematocysts do not discharge if the cnidophage membrane does not rupture upon release. A comparison of nematocysts maintenance in Spurilla neapolitana and nematocyst retention in other organisms is presented.

CHARACTERISTICS AND REGULATION OF FISSION ACTIVITY IN CLONAL CULTURES OF THE COSMOPOLITAN SEA ANEMONE, HALIPLANELLA LUCIAE (VERRILL)

1. Permanent cultures of a clone of H. luciae from N. W. Florida were reared under different temperature and feeding regimes in order to identifiy and quantify parameters of asexual reproduction. 2. The principle components of fission activity include fission rate, a delay period following a mechanical disturbance, and periodic pulses of increased fission activity; all components are regulated by temperature and feeding frequency. 3. A distinction is made between fission rate including the delay period (k), and fission rate following the delay period (kadj). 4. Fission rates (kadj) ranged from 0.0162 (doubling time = 42.8 days) at 17° C to 0.0727 (doubling time = 9.5 days) at 26° C. 5. Temperature is the foremost regulator of k; the greatest influence of feeding frequency was upon periodic pulses of fission activity. 6. Culture data indicate that recruitment in natural populations of this clone is restricted by seasonal temperature; below 20° C there is a sharp reduction in k. It is suggested that inhibition of k by temperatures below 20° C favors a transition from asexual to sexual reproduction. 7. The pulsatile, periodic character of fission activity is prominent in laboratory cultures, and suggests that such activity in natural habitats may have a phasic dependence upon tidal and photoperiodic cycles.

THE PTYCHOCYST, A MAJOR NEW CATEGORY OF CNIDA USED IN TUBE CONSTRUCTION BY A CERIANTHID ANEMONE

Light, transmission electron and scanning electron microscopy of a cerianthid anemone reveal that the protective tube with which the animal surrounds itself is composed almost entirely of discharged, interwoven cnidae of a heretofore undescribed type.As opposed to the threads of all nematocysts and spirocysts described to date, the thread of the new cnida, to which has been given the name of ptychocyst, is not helically folded, forming a variable number of pleats in circumference (from 5 to 11 observed in the present study), and no pleats in length. The discharged threads are quite long (over 2 mm in some) and are non-isodiametric, tapering from a diameter of about 5 µm at the base to about 2 µm at the tip for an overall reduction in diameter of 2.5 times.The everted thread has a number of fine ridges running along its length which can be seen using phase contrast microscopy and which represent the folds by which the thread is compressed in diameter. The thread tip is closed and the entire thread is unarm...

Comparative ultrastructure of catch tentacles and feeding tentacles in the sea anemone Haliplanella.

TEM observations of catch tentacles revealed that the tentacle tip epidermis is filled with two size classes of mature holotrich nematocysts and a gland cell filled with electron-dense vesicles. Vesicle production is restricted to upper-middle and tentacle tip regions, whereas holotrich development occurs in the lower-middle and tentacle base regions. Thus, catch tentacles have a maturity gradient along their length, with mature tissues concentrated at the tentacle tip. Occasional feeding tentacle cnidae (microbasic p-mastigophores and basitrichs) and mucus gland cells occur in proximal portions of catch tentacles, but are phagocytized by amoeboid granulocytes and transported to the gastrodermis for further degradation. No feeding tentacle cnidae or mucus cells occur distally in catch tentacles. Unlike catch tentacles, feeding tentacles are homogeneous in structure along their length with enidocytes containing mature spirocysts, microbasic p-mastigophore or basitrich nematocysts distributed along the epithelial surface. Cnidoblasts are recessed beneath cnidocytes, occurring along the nerve plexus. Mucus gland cells and gland cells filled with electron-dense vesicles are present in feeding tentacles, distributed at the epithelial surface. Granular phagocytes are rare in the feeding tentacle tip, but common in the tentacle base.

Immature nematocyst incorporation by the aeolid nudibranch Spurilla neapolitana

Ultrastructural observations and histochemical analyses show the presence of immature nematocysts within the cnidosacs of the aeolid nudibranch Spurilla neapolitana. Quantitative and ultrastructural analyses indicate that the immature nematocysts mature within the cnidosacs. The incorporation of unfired immature nematocysts may be the basic mechanism that permits nematocyst uptake, storage and utilization by nudibranchs.

The Form and Function of Cnidarian Spirocysts

SummaryUnlike most nematocysts, undischarged spirocyst threads bear hollow tubules rather than spines. The undischarged tubules are interconnected in hexagonal arrays and appear to be arranged in bundles along the length of the thread. Although the wall of the thread is folded in length and width, the tubules are not. Upon discharge and contact with sea water, the tubules solubilize and adhere to various substrates and prey. Traction between such objects and the everting thread causes the tubules to spin out into a web or meshwork of fine microfibrillae. Lack of contact of the everting thread with objects results in the tubules forming small droplets of partially solubilized material, some of which appear to be arranged in a helical pattern around the thread. The web or meshwork formed by the solubilized tubules in contact with various substrates probably serves to increase significantly the surface area and adhesive properties of the everted spirocyst thread.

A Comparison of Putative Sensory Receptors Associated with Nematocysts in an Anthozoan and a Scyphozoan

Although the cnidocil apparatus has long been considered to be the receptor for nematocyst discharge in hydrozoans, the corresponding structure in scyphozoans and anthozoans has been little studied (see Mariscal, 1974c for recent review). Westfall (1966a, b) has called this a “cnidocil” in a scyphozoan and Pantin (1942) has used the term “ciliary cones” to describe small structures associated both with cnidocytes and sensory cells in sea anemones. Using scanning electron microscopy, Mariscal (1974a, b) has shown a correlation between nematocyst-bearing regions and ciliary cones on the tentacles of certain sea anemones and corals. More recently, Mariscal, Bigger and McLean (1976) have reported that spirocysts are not associated with ciliary structures on the tentacles of various zoantharians, but rather occur in close association with two different types of microvilli.