First records of hydroid epibionts on the introduced macroalga Gracilariaparvispora in the Mexican Pacific

Background

The red macroalga Gracilariaparvispora is an introduced species in the Mexican Pacific. To date, there are no published studies on its sessile epibionts, including the hydrozoans and bryozoans, which are the dominant epibionts on macrophytes and of significant biological and economic interest.

New information

This study provides insight into the faunal diversity of hydroids growing on G.parvispora. A total of 185 thalli from both herbarium specimens and field samples collected from five sites in La Paz Bay were revised. Each thallus size and the presence of hydroid epibionts in each thallus region were registered. Eight different hydrozoan taxa were growing on the red macroalgae, including the first recorded observation of Obeliaoxydentata in the Gulf of California. The sizes of the collected thalli were mostly under 7.0 cm, the maximum number of taxa per thallus was three and the thallus region containing the highest number of epibionts was in the middle. Significant differences were observed amongst the lengths of thalli with and without epibionts. The thalli with epibionts were larger than the thalli without epibionts. Similarly, significant differences were observed amongst the months. The pair-wise test revealed that each month exhibited distinctive epibiont taxa when compared to the others. This study highlights the lack of information on these associations. Further research is needed to understand whether introduced macroalgae can bring non-native epibiont species to an area.

Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands

Forty-two species of hydroids, excluding stylasterids, are reported in the present collection from the Northwestern Hawaiian Islands. Of these, four are anthoathecates and 38 are leptothecates. Among the latter, Sertularella affinicostata and Monotheca gibbosa are described as new species. The binomen Halopteris longibrachia is proposed as a new replacement name for Plumularia polymorpha var. sibogae Billard, 1913, an invalid junior primary homonym of P. sibogae Billard, 1911. Based largely on evidence from earlier molecular phylogenies, the genus Disertasia Neppi, 1917 is resurrected to accommodate species including Dynamena crisioides Lamouroux, 1824, Sertularia disticha Bosc, 1802, and Sia. moluccana Pictet, 1893. Sertularella robusta Coughtrey, 1876 is an invalid junior primary homonym of Sla. gayi var. robusta Allman, 1874a, and has been replaced here by the binomen Sla. quasiplana Trebilcock, 1928, originally described as Sla. robusta var. quasiplana Trebilcock, 1928. Clytia hummelincki (Leloup, 1935) is referred to the synonymy of its senior subjective synonym, C. brevithecata (Thornely, 1900). Following Reversal of Precedence provisions in the International Code of Zoological Nomenclature to preserve prevailing usage of binomena, the familiar names Sia. disticha Bosc, 1802 (also known as Dynamena disticha) and Lytocarpia phyteuma (Stechow, 1919b) are designated nomena protecta and assigned precedence over their virtually unknown senior synonyms Hydra quinternana Bosc, 1797 and Aglaophenia clavicula Whitelegge, 1899, respectively, names now reduced to the status of nomena oblita. Twenty species are reported for the first time from Hawaii [Eudendrium merulum Watson, 1985, Phialellidae (undetermined), Hebella sp., Hebellopsis scandens (Bale, 1888), H. sibogae Billard, 1942, Clytia brevithecata, C. linearis (Thornely, 1900), C. cf. noliformis (McCrady, 1859), Halecium sp., Sla. affinicostata, Sla. angulosa Bale, 1894, Pasya heterodonta (Jarvis, 1922), Tridentata orthogonalis (Gibbons & Ryland, 1989), Pycnotheca producta (Bale, 1881), Monotheca gibbosa, H. longibrachia, A. postdentata Billard, 1913, A. suensonii Jäderholm, 1896, A. whiteleggei Bale, 1888, and L. flexuosa (Lamouroux, 1816)]. Sertularia orthogonalis, reported for only the third time worldwide, is assigned to the genus Tridentata Stechow, 1920. Hydroids of the NOWRAMP 2002 collection consisted largely of presumptive widespread species, with over 75% of them having been reported elsewhere in the tropical Indo-west Pacific region.