Studies of mysid diets by gut contents analysis have generally revealed a broadly omnivorous feeding habit, but there are also tendencies towards carnivory, herbivory and/or detritivory (e.g. Nath & Pillai, 1973; Siegfried & Kopache, 1980; Mauchline, 1980; Zagursky & Feller, 1985; Wooldridge & Bailey, 1982; Webb & Wooldridge, 1989). Examination of feeding structures is also necessary to support inferences about feeding ecology (e.g. Webb & Wooldridge, 1989). However, there have been few studies relating to the functional morphology of mysid foreguts (Gelderd, 1909; Haffer, 1965; Nath & Pillai, 1973; Mauchline, 1980; Friesen et al., 1986; Webb & Wooldridge, 1989; Storch, 1989). With the exception of the latter two studies, qualitative descriptions and characterization of the different internal foregut structures have been primarily based on light microscopy. These studies may misinterpret the internal arrangement, topography, and three-dimensional orientation of the internal armature of the foregut, mainly due to problems with depth of field (Grice & Lawson, 1971). Oshel & Steele (1988), from SEM observations, briefly described some foregut features of Gnathophausia ingens. In a comparative study, Storch (1989), using the techniques of transmission and scanning electron microscopy, described in detail the different food chambers and channels, cuticular ridges, and ultrastructure of the epithelial and cuticular linings of the mysid foregut. Webb & Wooldridge (1989) noted the strong relationship between mouthparts, foregut morphology, and the feeding habits of two co-occurring mysids.

A wide variety of fish and invertebrates are associated with marine jellyfishes, and their interactions are diverse. We preliminarily investigated symbionts on two species of rhizostome jellyfishes collected from Leyte and Palawan Islands, the Philippines, in August 2013. The collected jellyfishes were Lobonemoides robustus Stiasny on both islands and Acromitus maculosus Light on Palawan Island. Lobonemoides robustus is commercially harvested on both islands, and seems to have been previously misidentified as Lobonema smithi Mayer. The associated fish juveniles on these hosts were identified as Alepes djedaba (Forsskål) and Carangoides equula (Temminck & Schlegel). Alepes djedaba is closely associated with many species of scyphozoan jellyfish broadly in the southeastern Asian waters. The associations of carangids with jellyfish are also reviewed.

A new species of Acartia (Odontacartia), A. (O.) edentatasp. n., was collected from Leyte Island in the Philippines. Morphologically, the new species resembles A. (O.) pacifica Steuer, 1915. The female of the new species differs from other species of the A. (O.) erythraea Giesbrecht, 1889 species group in the absence of a pair of sharp spines on the posterior border of the genital double-somite and absence of setules on the lateral margins of urosomites 1–3. Unlike other congeners of the species group, males of the new species lack fine setules along the posterior margin of the prosome. Comparison of the new species with A. (O.) pacifica by pairwise distance data for the 16S (282 bp) gene indicates that these species differ by 20–21%, while the COI gene (636 bp) indicates a difference of 16–17%. The new species seems to be a coastal, occurring in warm waters having a salinity of 33.5.

The relationship between Zooplankton community structure and selected environmental conditions was investigated by simultaneous two-day consecutive sampling in the waters overlying Coral and sand sites off Sibu Island and a Seagrass site off Tinggi Island, Johor, Malaysia. A total of 129 taxa were identified, 60 non-copepod taxa and 69 copepod species in all samples. Uni-and multi-variate analyses reveal distinct Coral, sand, Seagrass copepod assemblages with indicator copepod species and attributes of their size fractions. Small fraction (100-335 µm) samples contained greatest number of individuals, few rare species and were densest at onshore depths, and the opposite for large fraction (>335 µm) samples but were densest at nighttime and most species rich in the Coral site at night. Higher species diversity at offshore stations is due likely to ecotonal effects of overlapping oceanic and nearshore communities. This study demonstrates the usefulness of uni-and multi-variate analyses in identifying patterns in Zooplankton community structure in representative shallow tropical habitats, and the need for accurate Zooplankton taxonomy, nighttime and daytime and onshore and offshore sampling, and size fractionation of samples.

Our observations on scyphomedusae from selected Philippine embayments identified specific animals commensal with five species of rhizostome scyphomedusae, Acromitoides purpurus, Mastigias sp., Phyllorhiza punctata, Rhopilema hispidum and Versuriga anadyomene. Acromitoides purpurus medusae harbor the crab Charybdis feriata, the carangid fish Alepes djedaba and the poecilostomatoid copepod Paramacrochiron sp. The carangid A. djedaba was an associate of the blue morph of A. purpurus and Rhopilema hispidum in Panguil Bay. A black-pigmented Alepes sp. was found associated with burgundy A. purpurus medusae in Carigara Bay. Charybdis feriata juveniles are common commensals of all morphs of A. purpurus, R. hispidum and P. punctata medusae. Only the zooxanthelate Mastigias sp. lacked animal symbionts. We invoke the "meeting-point hypothesis" and the general theory of fish aggregation to floating structures to explain fish symbiosis with their medusan hosts. The invertebrate-medusa associations are attributed to feeding behaviors and predator avoidance by resident commensals. This study provides record of the poorly studied scyphozoan species and their association with animals in Philippine waters. Finally, we discuss the potential reasons why the golden spotted jellyfish, Mastigias sp., appears to lack animal commensals.