The shrimp Hippolyte sapphica has a unique and sharp rostral dimorphism: morphotype A with a well-developed dentate rostrum, and morphotype B with a short, juvenile-like toothless rostrum. Previous research has shown that both morphotypes/forms belong to the same species and co-occur in the same habitat. Both forms occur in both sexes; however, form B individuals have a higher tendency to become males. Moreover, form A females are characterized by prolonged viability. The present comparative morphometric study concentrates on the changes induced by the rostral dimorphism and interprets them in terms of eco-morphological adaptations. Results showed that (i) the rostral length was the most isometric among the studied morphometric variables; (ii) males of A and B forms were not significantly different morphometrically; (iii) unexpectedly, form A non-ovigerous females had more developed carapace, abdominal somites and appendages in comparison with form B and, finally (iv), form B ovigerous females had higher tail and scaphocerite lengths, suggesting that they overcome higher turbulent force during the rapid backward movements and that the long rostrum improves hydrodynamic streamlining and stability. In conclusion, the previous finding that form B individuals tend to become males receives an adaptational explanation. The gene(s) responsible for the short rostrum accumulate in males, where their micro-evolutionary disadvantage is minimal or even absent.

A new species of the hippolytid shrimp genus Lebbeus White, 1847 is described from the Von Damm Vent Field (VDVF) on the Mid-Cayman Spreading Centre, Caribbean Sea, at 2294 m water depth. Lebbeus virentova sp. nov. is defined and illustrated from seven specimens, with brief notes on its distribution and habitat. Molecular phylogenetic data from the COI mDNA region are used to analyse the species’ phylogenetic position, and its morphology is compared with previously described species. This new species represents the second family of caridean shrimp to be reported from the VDVF. Lebbeus virentova sp. nov. is the eighth member of the genus to be described from hydrothermal vents and appears to be the first hippolytid shrimp at a vent field known from outside the Pacific Ocean.

The hippolytid genus Leontocaris includes eight species, all restricted to the deep sea (240–2182 m). Associations with deep sea coralline habitats were reported and are herein confirmed. Three Australian species were recorded at seamounts as were the specimens herein identified as L. smarensis sp. nov. These specimens were sampled at the South Mid-Atlantic Ridge (SMAR) by the Mar Eco project during 12 bottom trawls using a Sigsbee trawl. The SMAR is a seamount chain that rises from 4000 m depth, with mountains of 100–200 km wide and 14,000 km length. Leontocaris smarensis sp. nov. shows closest affinity to L. lar from the north-western Atlantic and L. yarramundi, from Australia and New Zealand. It differs from L. lar mainly in: (1) the scaphocerite distolateral tooth reaching the distal margin of the blade while clearly falling short in the latter species; and (2) the mandibular palp possessing three distal setae while setae are absent in L. lar. The new species differs from L. yarramundi in the number and disposition of dorsal teeth on rostrum and in the absence of an acute posterolateral spine on abdominal somites 4 and 5.

The capture of the species Bythocaris cosmetops in the Alboran Sea (southern Spain, western Mediterranean Sea), previously known from only two specimens from the Atlantic, Sierra Leone (south-west Africa) and the northern Bay of Biscay (north-west Europe), represents the first record of the genus and species in the Mediterranean Sea and Iberian Peninsula (south-west Europe). New data on morphology, biology and habitat are provided and discussed.