Pacific Science Volume 37, Number 2, 1983

37:2 Table of Contents - Pacific Science

Fri, 01 Apr 1983 00:00:00 GMT

Biology and Life Cycle of Siganus vermiculatus (Siganidae, Pisces)

Gundermann, N; Popper, DM; Lichatowich, T — Fri, 01 Apr 1983 00:00:00 GMT

The herbivorou s fish Siganus vermiculatus (Valenciennes) (Siganidae; Pisces), a mangrove swamp dweller, was studied in the field and in captivity in Fiji. The fish has a lunar spawning cycle, benthic sticky eggs, and pelagic larvae. Metamorphosis occurs between 23 and 27 days after hatching. The fry live in small schools in brackish or fresh water among mangrove roots. The young and adults are found mainly in shallow, murky water of mangrove swamps where they move in and out with the tides . The adults are sometimes seen in clear water near coral reefs or over sandy bottoms. Feeding takes place during the day and at night and consists mainly of grazing on algae and mangrove roots. A tolerance of extreme fluctuations in physicochemical parameters (temperature 19 to 38°C; salinity 2 to 55 ppt; dissolved oxygen 1.2ppm; pH 6.2 to 8.4) permits the species to live in mangrove swamps.

Patterns of Shell Resource Utilization by Terrestrial Hermit Crabs at Enewetak Atoll, Marshall Islands

Willason, SW; Page, HM — Fri, 01 Apr 1983 00:00:00 GMT

Patterns of gastropod shell utilization by Coenobita perlatus and C. rugosus were investigated on three islets of Enewetak Atoll, Marshall Islands. Habitat, hermit crab size, and hermit crab species all influenced the utilization of shells by Coenobita. Small crabs ( < 8mm carapace length) used 63 shell species, while large hermit crabs ( > 19mm) used only two species. Coenobita perlatus occupied long, narrow shells (e.g. , Rhinoclavis) more frequently than C. rugosus. By contrast, C. rugosus used shorter shells (e.g., Nerita) more frequently. Reproduction of C. rugosus, both the percentage of ovigerous females and fecundity, was not influenced by the shell species occupied.

Feeding Activity Patterns and Carrion Removal by Terrestrial Hermit Crabs at Enewetak Atoll, Marshall Islands

Page, HM; Willason, SW — Fri, 01 Apr 1983 00:00:00 GMT

Terrestrial hermit crabs (Coenobita spp.) were observed feeding on a variety of food items corresponding with observations on the genus worldwide . A field experiment was conducted which examined (1) the feeding activity of Coenobita in two habitats and (2) their potential impact on the removal of carrion and on the colonization of carrion by fly maggots. Habitat and time of day influenced the size and species of Coenobita feeding. Large C. perlatus fed only at night and had the greatest impact on the carrion. Although small Coenobita had little effect on the carrion, their feeding activity did reduce the number of fly maggots in the carrion. The scavenging activity of hermit crabs may serve a useful role on inhabited islets. The rapid removal of carrion would reduce potential fly breeding sites.

Preliminary Investigations of Burrow Defense and Intraspecific Aggression in the Sea Urchin, Strongylocentrotus purpuratus

Maier, Douglas; Roe, Pamela — Fri, 01 Apr 1983 00:00:00 GMT

Intraspecific aggressive burrow defense beha vior of the sea urchin Strongylocentrotus purpuratus was observed. An urchin occupying a burrow defends its position against intruders by moving out from the burrow and pushing the intruder away. Only spines are used in this behavior. When the intruder begins to retreat, usually within minutes, the occupant returns to the burrow. The burrow defense behavior of S. purpuratus was compared to that of the tropical urchin Echinometra lucunter.

The Land Nemertine Argonemertes Dendyi (Dakin) in Hawaii (Nemertinea: Hoplonemertinea: Prosorhochmidae)

Howarth, Francis G; Moore, Janet — Fri, 01 Apr 1983 00:00:00 GMT

Land nemertines are here reported in the Hawaiian Islands for the first time. Argonemertes dendyi, a native of Western Australia, has been found in moist forest litter at high elevations on the islands of Maui and Hawaii, and has also invaded lava tubes on the latter island. This is the first report of a land nemertine from caves

Feeding and Distribution Study of the Sunflower Sea Star Pycnopodia helianthoides (Brandt, 1835)

Shivji, M; Parker, D; Hartwick, B; Smith, MJ; Sloan, NA — Fri, 01 Apr 1983 00:00:00 GMT

Observations are reported on the feeding biology of Pycnopodia helianthoides (Brandt) in Barkley Sound, British Columbia, in areas of differing wave exposure . Three hundred asteroids were examined; 220 were feeding on prey representing II taxa , with heaviest predation on gastropods, bivalves, and crustaceans. P. helianthoides found on soft substrates were larger than those inhabiting hard substrates. Juvenile sea stars (< 5 cm diameter) were found primarily at protected sites often on kelp substrate. The observed size distributions of P. helianthoides may be the result of the nature of food resources available in different habitats. Significant positive correlations were obtained between sea star size and prey size except in the case of the gastropod Tegula pulligo. The possible importance of sea star predation on this snail is discussed.

Morphological Variability during Longitudinal Fission of the Intertidal Sea Anemone, Anthopleura elegantissima (Brandt)

Sebens, Kenneth P — Fri, 01 Apr 1983 00:00:00 GMT

The sea anemone Anthopfeura elegantissima forms clonal aggregations on rocky shores along the Pacific Coast of North America by a process of longitudinal fission. Fission can occur by lateral stretching of the column and separation of the two halves followed by internal regeneration of parts of the actinopharynx and of the column. Two new directive mesenteries, one siphonoglyph, and several pairs of mesenteries flanking the directives also form . Alternatively, large individuals appear to form new directive mesenteries and siphonoglyphs well in advance of division

Tree Cover Changes in Mamane (Sophora chrysophylla) Forests Grazed by Sheep and Cattle

Scowcroft, Paul G — Fri, 01 Apr 1983 00:00:00 GMT

Using aerial photographs taken in 1954, 1965, and 1975, percentage of tree cover was determined for three sections of the sheep- and cattlegrazed mdmane (Sophora chrysoph lla) forest of Mauna Kea , Hawaii. In one section , the Ka'ohe Game Management Area, where grazing by sheep was judged light, tree cover increased slightly during the 21-yr period , and tree cover did not change significantly along an elevation gradient. This condition was probably the result of the predominance of naio (Myoporum sandwicense) trees, which are not as palatable as mamane and, therefore, are less sensitive to browsing. In the Mauna Kea Forest Reserve, the most heavily sheep browsed of the three section s, a significant loss of tree cover was observed between 1965and 1975near tree line where feral sheep tended to concentrate their browsing. Of the three sections examined, Parker Ranch, which was grazed mainly by cattle, sustained the greatest loss of tree cover during the 21-yr period, reflecting the more destructive nature of cattle browsing as compared to sheep browsing. Increases of tree cover in areas relatively free of sheep within the Mauna Kea Forest Reserve indicated that habitat for the palila, an endangered bird that depends on the mamane forest , will improve slowly after feral sheep are removed.

Ecology of the Imported Red Seaweed Eucheuma striatum Schmitz on Coconut Island, Oahu, Hawaii

Russell, Dennis J — Fri, 01 Apr 1983 00:00:00 GMT

The introduced alga Eucheuma striatum Schmitz was studied regarding its spread, control, and ecology in Kaneohe Bay, Oahu, Hawaii. Its distribution in Kaneohe Bay during May 1976was nearly the same as when it was originally planted 2 yr earlier. It lacked the ability to disperse over shallow depressions both in the reef and in deep water , and it did not colonize neighboring reefs without the help of man. Depth was the single most important physical factor limiting its dispersal. A total fresh weight standing crop of from 21 to 24 metric ton s of E. striatum was recorded on a 500-m-long section of reef edge from December 1976 to June 1977. When protected from grazing its growth rate was about 5.0 percent/day. Data support the conclusion that the population on the reef edge was maintained only by a steady influx of thallus fragments that escaped from enclosed experimental plantings on the reef flat. When the experimental plantings were removed the population could not maintain itself and soon disappeared. Eucheuma striatum did not compete with native algal macrophytes and appeared to be the basis of a community richer in animal species than adjacent reefs. It provided 10-20 tons/me of food for grazing fish, shelter , and a substratum for numerous invertebrates. Eucheuma striatum did not attach to corals, but it did cause their death by shading.