Restoring depleted coral‐reef fish populations through recruitment enhancement: a proof of concept

To determine whether enhancing the survival of new recruits is a sensible target for the restorative management of depleted coral‐reef fish populations, settlement‐stage ambon damsel fish Pomacentrus amboinensis were captured, tagged and then either released immediately onto small artificial reefs or held in aquaria for 1 week prior to release. Holding conditions were varied to determine whether they affected survival of fish: half the fish were held in bare tanks (non‐enriched) and the other half in tanks containing coral and sand (enriched). Holding fish for this short period had a significantly positive effect on survivorship relative to the settlement‐stage treatment group that were released immediately. The enrichment of holding conditions made no appreciable difference on the survival of fish once released onto the reef. It did, however, have a positive effect on the survival of fish while in captivity, thus supporting the case for the provision of simple environmental enrichment in fish husbandry. Collecting and holding settlement‐stage fish for at least a week before release appear to increase the short‐term survival of released fish; whether it is an effective method for longer‐term enhancement of locally depleted coral‐reef fish populations will require further study.     

Development of nine microsatellite markers for Pomacentrus amboinensis

The relatively long pelagic larval duration of Pomacentrus amboinensis, a tropical fish, suggests the potential for long-distance dispersal; however, several nongenetic studies have found substantial self-recruitment at one location. To analyse patterns of connectivity of this species, primers for nine independent microsatellite loci were developed for P. amboinensis using a magnetic bead enrichment protocol. Twenty individuals from one location were analysed and observed heterozygosities ranged from 0.7 to 0.95. Eight of nine loci were in Hardy-Weinberg equilibrium and no evidence of linkage or null alleles were found.     

Ultraviolet absorbance of the mucus of a tropical damselfish: effects of ontogeny, captivity and disease

The ultraviolet (UV) absorbance of the mucus of a Great Barrier Reef damselfish Pomacentrus amboinensis was investigated with regard to ontogeny and time spent in captivity. The UV absorbance of P. amboinensis mucus increased with fish size and decreased with time spent in captivity. The wavelength of maximum absorbance of the mucus did not change with fish size, but shifted towards shorter wavelengths with increasing time spent in captivity. The UV absorbance of the mucus of fish with 'fin rot' was compared to that of similar healthy individuals, and a significant decrease in UV absorbance of unhealthy fish mucus was detected; no wavelength shifting occurred. Pomacentrus amboinensis appears to sequester mycosporine-like amino acids from the diet in order to protect epithelial tissues from UV damage, and decreases in UV absorbance in captive fish were probably due to insufficient dietary availability.     

Degraded Environments Alter Prey Risk Assessment

Elevated water temperatures, a decrease in ocean pH, and an increasing prevalence of severe storms have lead to bleaching and death of the hard corals that underpin coral reef ecosystems. As coral cover declines, fish diversity and abundance declines. How degradation of coral reefs affects behavior of reef inhabitants is unknown. Here, we demonstrate that risk assessment behaviors of prey are severely affected by coral degradation. Juvenile damselfish were exposed to visual and olfactory indicators of predation risk in healthy live, thermally bleached, and dead coral in a series of laboratory and field experiments. While fish still responded to visual cues in all habitats, they did not respond to olfactory indicators of risk in dead coral habitats, likely as a result of alteration or degradation of chemical cues. These cues are critical for learning and avoiding predators, and a failure to respond can have dramatic repercussions for survival and recruitment.     

Laboratory experiments on factors affecting oviposition site selection in Toxorhynchites amboinensis (Diptera: Culicidae), with a report on the occurrence of egg cannibalism

Laboratory experiments tested the effects of water quality and the presence of conspecific and heterospecific immatures on oviposition by Toxorhynchites amboinensis (Doleschall). The females showed a highly significant preference for oak leaf infusion water over distilled water. When twenty starved third and fourth instar Tx.amboinensis larvae were present in the water, substantially fewer eggs were counted from pots containing these conspecifics, than from controls in which no larvae were present. Numbers of eggs from pots containing starved second instar larvae did not differ significantly from controls. Observations of larval behaviour while oviposition was occurring suggested that egg numbers were reduced in containers because of egg cannibalism with third and fourth instar larvae, and not because the larvae caused a deterrent effect. Subsequent experiments confirming the occurrence of substantial egg cannibalism by third and especially fourth instar larvae are described. As with larvae, the presence of Tx.amboinensis pupae in the water had little effect on oviposition. If placed in the water 24 h prior to test, pupae very slightly enhanced its attractiveness, but if introduced immediately before test there appeared to be a slight deterrent effect. With heterospecific larvae, twenty fourth instar Ae.aegypti larvae introduced into infusion water 24 h before test rendered the water slightly attractive, while water in which Ae.aegypti larvae had been reared for 48 h proved highly repellent.     

Short report on the effect of a parasitic isopod on the reproductive performance of a shrimp

The present work studied the degree of inhibition caused by the bopyrid isopod Eophryxus lysmatae (Caroli, 1930 [Caroli, E., 1930. Notizia di tre specie nuove ed una poco nota di Bopiridi addominali, parassiti di Caridei del golfo di Napoli. (Contributo alla conoscenza del genere Phrixus Rathke). Boll. Soc. Nat. Napoli 41, 258-269]), an abdominal parasite, on the reproductive performance of its host, the protandric simultaneous hermaphrodite shrimp Lysmata seticaudata (Risso, 1816). Parasitized shrimp (PS) was not able to produce embryos, although they could successfully fertilise the eggs of unparasitized shrimp (US). All US paired with PS were able to fertilise eggs when paired with other US. The average number of larvae (±S.D.) produced by US shrimp paired with US and PS (344±27 and 346±23, respectively) was not significantly different (p=0.73). The average intermolt period duration (±S.D.) for US and PS (10±1.2 and 11±0.8 days, respectively) was not significantly different (p=0.82), with bopyrid parasites molting synchronously with their host. No PS lost its parasite during ecdysis. Although only three parasitized shrimp were used in the present work, parasitic castration induced by E. lysmatae seems to only affect the female sexual system of the simultaneous hermaphrodite L. seticaudata, and therefore parasite-induced “reproductive death” does not occur in this species as in other gonochoric and sequencial hermaphroditic caridean shrimp. Nutritional drain and disruption of endocrine mechanisms possibly caused by the bopyrid parasite are discussed.     

Electroantennogram studies of potential oviposition attractants for Toxorhynchites moctezuma and T. amboinensis mosquitoes

Abstract.Ether extracts of water samples taken from tyre sections in the field were shown to be active in electroantennogram studies with female Toxorhynchites moctezuma (Dyar & Knab) and Toxorhynchites amboinensis (Doleschall). In addition, electroantennograms were recorded from both Toxorhynchites species for seven compounds found commonly in water containing decaying leaves and known to be oviposition attractants for other mosquito species. The compounds were 4‐methylcyclohexanol, phenol, indole, 3‐methylindole, m‐ cresol, o‐ cresol and p‐ cresol. The response thresholds for these compounds ranged between 1 × 10^–4μg and 1 μg for female antennae (100 μg for male antennae). These results provide a basis for behavioural studies of oviposition attractants for the Toxorhynchites species.     

Ability of Monaco shrimp Lysmata seticaudata (Decapoda: Hippolytidae) to control the pest glass anemone Aiptasia pallida (Actiniaria: Aiptasidae)

The present work highlights the ability of wild and cultured Monaco shrimp Lysmata seticaudata to control the glass anemone Aiptasia pallida. Starved shrimp ingested the highest percentages of glass anemones [85.7% and 89.3% for wild (W) and cultured (C) shrimp, respectively]. The absence of symbiotic zooxanthellae in glass anemones did not influence the shrimps feeding rate, with shrimp offered aposymbiotic anemones displaying the same feeding percentages (67.3% and 70.7% for W and C shrimp, respectively) as those offered sea anemones with symbiotic zooxanthellae (70.0% and 74.4% for W and C shrimp, respectively). Shrimp offered larger sea anemones had the lowest feeding percentages (33.0% and 36.3% for W and C shrimp, respectively), along with shrimp offered an alternative food (27.3% and 36.0% for W and C shrimp, respectively). There were no significant differences in the percentage of glass anemones ingested by cultured and wild Monaco shrimp in the same feeding trial.     

Observations on wolbachiae in mosquitoes

A slightly modified Giemsa smear procedure consistently demonstrated Wolbachia pipientis in Culex pipiens and the Wolbachia species of infected members of the Aedes scutellaris group. Aposymbiosis was induced in Aedes polynesiensis by treatment with 0.017 mg/ml tetracycline hydrochloride or by rearing larvae at temperatures of 32–33°C for 5–7 days. Aposymbiotic females were incompatible with infected males but the reciprocal cross was fertile. By light and electron microscopy wolbachiae were found in ovaries of Aedes albopictus, A. cooki, A. Niuafo'ou sp., A. polynesiensis from American Samoa and Tahiti, A. riversi, A. Tafahi sp., and A. upolensis. Wolbachiae were not detected in A. alcasidi, A. oceanicus, A. triseriatus, Culex peus, two laboratory colonies of C. pipiens, Culiseta incidens, Toxorhynchites amboinensis, or T. brevipalpis. Wolbachiae were found also in the ovarian follicular epithelium of A. albopictus. This is the first record of mosquito wolbachiae in nongerminal gonadal tissue.