Infraorder AXIIDEA de Saint Laurent, 1979

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Infraorder AXIIDEA de Saint Laurent, 1979

Compiler and date details

May 2012 - Peter Davie, Queensland Museum.

Axiidea Saint Laurent, M. de 1979. Vers une nouvelle classification des Crustacés Décapodes Reptantia. Bulletin de l'Office Nationale de Pêche de Tunisie 3: 15-31 [28].
Secondary source:
Poore, G.C.B., Ahyong, S.T., Bracken-Grissom, H.D., Chan, T.-Y., Chu, K.H., Crandall, K.A., Dworschak, P.C., Felder, D.L., Feldmann, R.M., Hyžný, M., Karasawa, H., Lemaitre, R., Komai, T., Li, X., Mantelatto, F.L., Martin, J.W., Ngoc-Ho, N., Robles, R., Schweitzer, C.E., Tamaki, A., Tsang, L.M. & Tudge, C.C. 2014. On stabilising the names of the infraorders of thalassinidean shrimps, Axiidea de Saint Laurent, 1979 and Gebiidea de Saint Laurent, 1979 (Decapoda). Crustaceana 87: 1258–1272.

Introduction

Axiideans are the sponge shrimps, ghost shrimps and some mud lobsters. They occur in a wide variety of habitats from the intertidal zone to at least 2,500 m depth. Ghost shrimps, callianassids and similar families, tend to have an elongate pleon with weakly connected somites and weak pleura. Axiids and strahlaxiids are more robust and shrimp-like. Most are burrowers in soft sediments, or live under rocks or in crevices or commensally with sponges. For a detailed general review of diversity and biology see Dworschak et al. (2012) and Dworschak (2000). While the name of the infraorder has been disputed de Saint Laurent’s name is now in general use (Poore et al. 2014).

Axiidea comprise a diverse assortment of shrimp-like crustaceans. In axiideans the first two pairs of pereopods are always both chelate, the first being strong chelipeds and the second much smaller and similar in size to the simple pereopods 3 and 4. Pereopod 5 is often minutely chelate or subchelate. Thoracic sternite 8 to which it attaches is well separated from fused thoracic sternites 3–7 which more anterior limbs attach to (as in Gebiidea and Anomura). The families can be distinguished only from a combination of characters.

Axiidea is one of two infraorders until recently considered part of Thalassinidea Latreille, 1831. The other is Gebiidea. The monophyly of Axiidea was proposed on morphological grounds (de Saint Laurent 1979; Sakai 2005) and confirmed by molecular studies (Robles et al. 2009; Tsang et al. 2008). These authors discovered two clades of Axiidea, one comparing only Axiidae and the other the remaining families. The terminal families of the second clade were called “callianassoids” by Robles et al. (2020) and Poore et al. (2019) who introduced many new genera and synonymised many others.

Poore (1994) provided keys to families and genera of what was then Thalassinidea. The most recent revisions of Axiidea (Sakai 2005, 2011) introduced many new family and generic names, and synonymised others. While some of these taxa are still valid the taxonomy has long since moved on. Not all have been accepted. The work of Poore & Griffin (1979) is the foundation of the taxonomy of this group in Australia but has been updated (Poore 2015; Poore & Collins 2015) and the results of molecular and morphological revisions (Poore et al. 2019; Robles et al. 2020).

The infrorder comprises 11 families not all of which live in Australia.

Diagnosis

Carapace more or less cylindrical, longer than wide; epistome short, not fused to basal antennular and antennal articles, with narrow point of contact with lateral margin of carapace. Exoskeleton calcified, or chitinised (rarely). Thoracic sternite 8 free from thoracic sternites 1–7. Pleon elongate, muscular; pleonite 2 pleuron overlapping pleonites 1 and 3, or all pleura overlapping next most posterior pleuron. Antennular penduncle articles aligned linearly, main flagellum long, lash-like, aesthetascs more-or-less evenly distributed. Pereopods 1, 2 chelate, first a large cheliped. Pereopod 5 shorter than others, subchelate. Uropods biramous.