Microcerberidea Lang, 1961

Main Page | Isopoda > Microcerberidea

Suggested Common Name: Cerberuses and Pillslaters
Number of subordinate taxa: 50 species in 2 families worldwide, with 17 species in both families present in our area.
Etymology: after Microcerberus Karaman, 1933. Common name refers to the two constituent families, see those for more information.
Taxonomic History: Formerly considered part of Aselloidea (Asellota), split out into its own suborder over the course of the 80s-00s
Description: Body elongate (Microcerberidea) or ovate (Atlantasellidae); sexual dimorphism outside basic features present, mainly involving pleopods 1-2. Antenna 1 reduced, scale absent; peduncle 2-segmented; flagellum 3-segmented. Antenna 2 scale absent. Mandible incisor present, multicuspidate; lacinia present, multicuspidate; spine row short, few-spined; molar present, long and pointed (Microcerberidae) or short and truncate (Atlantasellidae); palp 3- (Atlantasellidae) or 1- (Microcerberidae) segmented. Maxilla 1 biramous; endopod small, conical. Maxilla 2 well-developed or reduced; exopod biramous (Atlantasellidae) or uniramous (Microcerberidae). Maxilliped epipod present (Atlantasellidae) or absent (Microcerberidae); basis body not dominating maxilliped structure, often resembling a palp segment (Microcerberidae); endite fused to basis; palp 5-segmented. Pereopods 2-7 coxae entirely annulate (Afrocerberus and Protocerberus), with 2-4 annulate and 5-7 formed into coxal plates (Atlantasellidae and most Microceberidae) or all coxae formed into coxal plates (Coxicerberus). Penes unknown[?]. Pleon mostly fused with telson, with 2 large free pleonites with free margins. Pleonite 1 subequal in length to pleonite 2. Pleopod 1 highly modified, sexually dimorphic; ♂ pleopod uniramous, consisting of a basal protopod and a distal endite (=exopod), sometimes entirely absent; ♀ pleopod absent. Pleopod 2 highly modified, sexually dimorphic; ♂ pleopod biramous, protopod subquadrate, exopod very small, set distolaterally, endopod simple to highly modified, fused with appendix masculina, linear, set apically on protopod; ♀ pleopod absent. Pleopod 3 uniramous, subtriangular, tip sometimes erose. Telson domed (Atlantasellidae) or subterete (Microcerberidae), apparently not forming a branchial chamber in at least Microcerberidae. Uropods set distally on telson, biramous to uniramous.
Type taxon: Microcerberidae Karaman, 1933
Notes: The two subfamilies of this small suborder appear very different at first glance but are united by multiple unique features, such as the details in the pleopods and the pereopod coxae. One feature that also seems to unite the two families and appears to have escaped detection is the structure of the antenna 2 peduncle: the third segment is short and sharply bends at a 90 degree angle, effectively making the antenna geniculate. While geniculate antennae are not unique at all among Isopods, the specific way the antenna 2 are geniculated may be unique to Microcerberidea and could be an important feature in the future.
Both the subterranean Atlantasellidae and subterranean and intersitial Microceberidae appear to be highly derived from a now-extinct epigean ancestor, but many features highly derived in one family will appear more pleisomorphic in the other family. A prominent example are in the maxillipeds: in Atlantasellidae they're fairly normal and even almost indistinguishable from maxillipeds from other isopod groups, while in Microcerberidae the endite is massively reduced and the epipod is completely absent, resulting in a highly modified, almost pereopod-like maxilliped. The common ancestor most likely resembled an Asellote, the presumed closest relative to Microcerberidea, but with a few noticeable differences, having geniculate antenna 2 peduncles (see above), a straight ♂ pleopod 2 endopod, the lack of a second pleopod in ♀, and perhaps even the unusual annulate coxae/coxal plate pattern predominant across both families (assuming that the ring-like coxae on pereonites 5-7 of Afrocerberus and Protocerberus are a derived state). Perhaps the original Microcerberideans were outcompeted by the Asellotes, who's ♂ pleopod 2 shape may have made them more efficient at reproduction. Alternatively, the Asellotes and Microcerberideans coexisted for a long period of time until Scuticoxiferan groups outcompeted them, with Asellotes escaping extinction by diversifying in the deep sea but Microcerberideans, never fully leaving shallow waters, were reduced to 2 highly aberrant groups. Evidence for the latter over the former may come in the apparent niche partitioning between intersitial Asellotes (such as Angeliera and Leptocharontidae) and marine Microcerberids (Coxicerberus), indicating that Asellotes and Microcerberideans could have potentially coexisted with some moderate niche partitioning in other ecosystems in the past. Either way, any further evidence of either of these theories would lie in finding a very well-preserved fossil epigean Microcerberidean (very very unlikely) or potentially in genetic relationships withing Microcerberideans and between Microcerberidea and Asellota. 

Subordinate Taxa: Atlantasellidae, Microcerberidae

Key to families
1 a. Body ovate, able to conglobulate; antenna 1 peduncle highly differentiated from flagellum; maxilliped "normal", basis large and broad compared to palp segments with a crenate distal margin, epipod well-developed; ♂ pleopod 2 (when known) exopod 2-segmented; currently only known from caves under Bermuda and Hispaniola but may be found elsewhere in the Caribbean --> Atlantasellidae
b. Body elongate and narrow, unable to conglobulate; antenna 1 peduncle poorly differentiated from flagellum; maxilliped reduced with the palp dominant, basis small with a digitate distomedial lobe, resembling a palp segment, epipod absent; ♂ pleopod 2 exopod 1-segmented widespread intersitial organisms along tropical and (in the Pacific basin) temperate coasts as well as inland subterranean freshwaters in the southern Nearctic and the Caribbean --> Microcerberidae


Jaume, D. (2001). A new atlantasellid isopod (Asellota: Aselloidea) from the flooded coastal karst of the Dominican Republic (Hispaniola): evidence for an exopod on a thoracic limb and biogeographical implications. Journal of Zoology, 255(2), 221-233.

Sket, B. (1979). Atlantasellus cavernicolus n. gen., n. sp. (Isopoda Asellota, Atlantasellidae n. fam.) from Bermuda. Bioloski vestnik (Ljubljana), 27(2):175-183.

Wägele, J. W. (1982). On a new Microcerberus from the Red Sea and the relationship of the Microcerberidea to the Anthuridea (Crustacea, Isopoda). Zoologica Scripta, 11(4):281-286.

Wägele, J. W. (1983). On the origin of the Microcerberidae (Crustacea: Isopoda). Journal of Zoological Systematics and Evolutionary Research, 21(4):249-262.

Wägele, J. W., Voelz, N. J., & Vaun McArthur, J. (1995). Older than the Atlantic Ocean: discovery of a fresh-water Microcerberus (Isopoda) in North America and erection of Coxicerberus, new genus. Journal of Crustacean Biology, 15(4):733-745.

Published: Jan 1, 2023
Updated: Nov 1, 2023