Molecular systematics of peppermint and cleaner shrimps: phylogeny and taxonomy of the genera Lysmata and Exhippolysmata (Crustacea: Caridea: Hippolytidae)

Shrimps from the ecologically diverse genera Lysmata and Exhippolysmata are rare among marine invertebrates because they are protandric simultaneous hermaphrodites: shrimps initially mature and reproduce solely as males, and later in life become functional simultaneous hermaphrodites. Considerable progress on the reproductive ecology of members from these two genera has been achieved during the last decade. However, several outstanding issues of systematic nature remain to be addressed. Here, a molecular phylogeny of these two genera was used to examine the overall evolutionary relationship within and between species and genera, and to answer various questions related to the systematic status of several species. The present phylogenetic analysis, including 53 sequences and 26 species of Lysmata and Exhippolysmata, indicates that semiterrestrial shrimps from the genus Merguia represent the sister group to a second natural clade composed by shrimps from the genera Lysmata and Exhippolysmata. Also, the phylogenetic analysis confirmed that the genus Lysmata is paraphyletic, and includes the genus Exhippolysmata, as noted in a preliminary study. The tree partially supports the separation of species with or without a developed accessory branch into two different genera or subgenera (i.e. Lysmata and Hippolysmata having a well‐developed accessory branch, or not, respectively). The genetic distance between the cleaner shrimps Lysmata amboinensis and Lysmata grabhami was smaller than has been observed between other sister species. On the other hand, the topology of the tree indicates that these two entities are reciprocally monophyletic. Thus, this latter result, together with minor but constant differences in the colour pattern reported for these two entities, indicates that there is no reason to stop treating them as different valid species. This study enabled the long overdue resolution of standing taxonomic questions in shrimps from the genera Lysmata and Exhippolysmata. In the future, this phylogeny will help to reveal the conditions favouring the origins of several behavioural and morphological novelties in these unique shrimps. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 254–265.     

Indirect predator effects influence behaviour but not morphology of juvenile coral reef Ambon damselfish Pomacentrus amboinensis

A 6-week laboratory experiment exposed juvenile Ambon damselfish Pomacentrus amboinensis to visual and chemical cues of either a predator, a herbivore or a null control (sea water) and found no effect of predator cues on prey morphology (proportion of ocellus to eye diameter, body depth, standard length and fin area). Nonetheless, behaviour was significantly affected by predator presence, with prey less active and taking half as many feeding strikes when exposed to predators compared to fish from the null control. The presence of a herbivore also affected prey behaviour similar to that of the predator, suggesting that the presence of a non-predator may have important effects on development.     

The relative importance and distribution of Aedes polynesiensis and Ae.aegypti larval habitats in Samoa

Abstract. In preparation for a Filariasis Control programme in Samoa, during 1978 monthly larval surveys of the vector mosquito Aedes polynesiensis were carried out in four study villages in the main island of Upolu. A more extensive survey of larval habitat distribution was then made in twenty-two villages of Upolu and eighteen of Savai'i island, to determine the importance of habitat types according to their abundance, volume of water and whether their productivity was permanent or seasonal. Ae.aegypti larval densities and habitat distribution were also monitored and the occurrence of predatory Toxorhynchites amboinensis larvae in northern Upolu was recorded from forty-one collections. Aedes Breteau and container indices fluctuated with the pattern of rainfall in two coastal villages and an inland bush village, but not in a coconut plantation community. The five main Aedes larval habitat types encountered were: 200 litre water-storage drums, discarded tins and bottles, coconut shells, automobile tyres and treeholes. Aedes immatures occurred perennially in drums and tree holes, but breeding discontinued in tins, bottles and coconut shells during the driest month of July. For Ae.polynesiensis in Upolu the Breteau and container indices of 104.5 ± SD 80.9 and 35.3 ± 12.4 respectively were significantly higher than those in Savai'i: 33.1 ±25.0 and 24.3 ±20.0 respectively. Likewise for Ae.aegypti the Breteau and container indices of 50.8 ± 32.5 and 23.9 ± 15.6, respectively, were also significantly higher than those in Savai'i: 12.7 ± 17.1 and 9.4 ±13.2 respectively. Habitat types greater or lesser importance were determined by plotting the percentage of each type of container utilized for Aedes breeding against the percentage of each type amongst all larva-positive containers. Ae.polynesiensis preferred tree-holes but not water-storage drums. Ae.aegypti preferred drums and tyres; mixed populations of larvae of both species were commonest in these two types of habitat. Ae.polynesiensis occurred in every village. Ae.aegypti was encountered in all twenty-two villages surveyed in Upolu and nine of eighteen villages in Savai'i. Total larval surveys revealed that drums and tree-holes contained the highest numbers of Aedes larvae. The study provided criteria for planning a control programme.     

Hemolymph pH of the larvae of three species of mosquitoes,and the effect of Romanomermis culicivorax parasitism on the blood pH of Culex pipiens

The hemolymph pHs of late fourth-instar Culex pipiens, Aedes taeniorhynchus, and Toxorhynchites amboinensis were measured with pH-sensitive glass microelectrodes and were slightly alkaline; pH 7.51, 7.62, and 7.37, respectively. The hemolymph pH remained relatively constant during the development of C. pipiens larvae through the third and early and late fourth instars. The hemolymph pH in C. pipiens larvae parasitized with the mermithid nematode Romanomermis culicivorax was unaltered. These measurements provide an approximate pH (ca 7.4) which is normal for the hemolymph of larval mosquitoes, and should be useful for further development of a culture medium for R. culicivorax.     

Laboratory tests of the effects of p-cresol and 4-methylcyclohexanol on oviposition by three species of Toxorhynchites mosquitoes

Laboratory experiments tested the effects of p-cresol or 4-methylcyclohexanol at concentrations of 1, 10 and 50 ppm, on oviposition by the mosquitoes Toxorhynchites brevipalpis Theobald, Tx. amboinensis (Doleschall) and Tx. splendens (Wiedemann). A 5 + 5 ppm mixture of the two chemicals was also tested. All three species laid significantly more eggs in cups containing p-cresol, whereas only Tx. brevipalpis and Tx. amboinensis responded similarly to 4-methylcycohexonol and to the mixture of both chemicals. Tx. brevipalpis was, to a relatively limited degree, the most responsive of the three species. Ancillary experiments indicated that the chemicals were acting as attractants, causing more females to fly to treated cups. No stimulant effects were detected either in terms of the proportion of females that initiated oviposition flight (after flying to the cups) or in terms of the number of looping flights executed prior to ejection of an egg.     

Functional morphology of mouthparts and digestive system during larval development of the cleaner shrimp Lysmata amboinensis (de Man, 1888)

Mouthpart and alimentary canal development was examined in Lysmata amboinensis larvae using scanning electron microscopy and histology. The gross morphological features of external mouthparts and internal digestive tract structures of larvae at different developmental stages indicate that ingestive and digestive capabilities are well developed from early on. With increasing age of the larvae the mouthpart appendages increased in size, the hepatopancreas in tubular density and the midgut in length. The density of setae and robustness of teeth and spines of individual structures increased. The most pronounced changes from early to late stage larvae involved formation of pores on the paragnaths and labrum, transformation of the mandibular spine‐like teeth to molar cusps, development of the filter press in the proventriculus and of infoldings in the previously straight hindgut. The results suggest that early stage L. amboinensis larvae may benefit from soft, perhaps gelatinous prey, whereas later stages are better equipped to handle larger, muscular or more fibrous foods. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.