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A new species of Hourstonius (Amphipoda: Amphilochidae) from Todos-os-Santos Bay, Bahia State, Brazil, with an overview of the genus across the globe

Published online by Cambridge University Press:  11 March 2024

Jessika Alves*
Affiliation:
Universidade Federal da Bahia (UFBA), Instituto de Biologia, Laboratório de Invertebrados Marinhos: Crustacea, Cnidaria & Fauna Associada (LABIMAR), Rua Barão de Jeremoabo, 147, Ondina, Salvador, BA, CEP 40170-290, Brasil
Elizabeth G. Neves
Affiliation:
Universidade Federal da Bahia (UFBA), Instituto de Biologia, Laboratório de Invertebrados Marinhos: Crustacea, Cnidaria & Fauna Associada (LABIMAR), Rua Barão de Jeremoabo, 147, Ondina, Salvador, BA, CEP 40170-290, Brasil
Rodrigo Johnsson
Affiliation:
Universidade Federal da Bahia (UFBA), Instituto de Biologia, Laboratório de Invertebrados Marinhos: Crustacea, Cnidaria & Fauna Associada (LABIMAR), Rua Barão de Jeremoabo, 147, Ondina, Salvador, BA, CEP 40170-290, Brasil
*
Corresponding author: Jessika Alves; Email: [email protected]
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Abstract

Amphilochidae comprises 92 species of small and colourful amphipods that live associated with sessile marine organisms. Hourstonius is one of the most diverse genera with 17 described species, most of the species are recorded from North Temperate Pacific and Tropical Atlantic and live in shallow waters. Only three species of Amphilochidae are recorded in Brazil, and from the genus Hourstonius, there is a single species, H. wakabarae. In the present work, we describe a new species of Hourstonius from Todos-os-Santos Bay, the second species of the genus to the country and the first record of this genus from Bahia State. A taxonomic key and an overview of the genus across the globe are also provided.

Type
Research Article
Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press on behalf of Marine Biological Association of the United Kingdom

Introduction

Amphilochidae Boeck 1871 is composed of small benthic amphipods that are usually found associated with sessile marine invertebrates and comprise 14 genera (Hoover and Bousfield, Reference Hoover P and Bousfield2001). The family is defined, among other characteristics by showing: (1) rostrum distinct; (2) maxilla 1 inner plate small; (3) Gnathopods not sexually dimorphic; (4) coxae 2–4 deep; (5) Uropods slender, rami lanceolate; (6) Uropod 2 small, rami unequal (Hoover and Bousfield, Reference Hoover P and Bousfield2001).

In comparison with other amphipod families, Amphilochidae shows a relatively low diversity, with 92 described species (Karaman, Reference Karaman1980; Hirayama, Reference Hirayama1983; Hoover and Bousfield, Reference Hoover P and Bousfield2001; Leite and Siqueira, Reference Leite and Siqueira2013; Morales-Núñez and Chigbu, Reference Morales-Núñez and Chigbu2016; Tandberg and Vader, Reference Tandberg and Vader2018). The most diverse genus is Gitanopsis Sars, Reference Sars1892 with 18 species, followed by Hourstonius Hoover and Bousfield, Reference Hoover P and Bousfield2001 with 17 species (Hoover and Bousfield, Reference Hoover P and Bousfield2001; Leite and Siqueira, Reference Leite and Siqueira2013).

Many species of Hourstonius were previously included in Gitanopsis, but after the study of Hoover and Bousfield (Reference Hoover P and Bousfield2001), the genus Gitanopsis grouped species from the Arctic and Northern Atlantic Oceans living on 0–875 m in depth, whereas Hourstonius grouped circumtropical species inhabit only shallow waters (0–50 m) (Hoover and Bousfield, Reference Hoover P and Bousfield2001; Leite and Siqueira, Reference Leite and Siqueira2013). Hourstonius species show elongated telson, distally rounded; coxae 2–4 ventrally smooth, lateral cephalic lobe often broad, whereas Gitanopsis shows telson distally acute and minutely tridentated; coxae 2–4 ventrally serrated; lateral cephalic lobe often acute (Hoover and Bousfield, Reference Hoover P and Bousfield2001).

From Brazilian waters, only three amphilochid species are recorded: Amphilocus schubarti Schellenberg, Reference Schellenberg1938 recorded from Pernambuco State (8°S), Apolochus neapolitanus (Della Valle, Reference Della Valle1893) recorded from Rio de Janeiro (43°S) and São Paulo State (46°) and Hourstonius wakabarae Leite and Siqueira, Reference Leite and Siqueira2013 from São Paulo State (46°). In the present work, we describe a new species of Hourstonius from Todos-os Santos Bay, Bahia State (12°S), Brazil, being the first record of the genus from Bahia State and the second species of the genus with its type locality in Brazilian waters. We also discuss the Hourstonius world diversity and provide a taxonomic key for the genus across the globe.

Material and methods

The biological material was collected in Todos-os-Santos Bay, Bahia State, Brazil. Scuba diving was conducted in December 2019 at the Yacht Club da Bahia (1.0–2.0 m depth), Salvador City, to collect sessile fauna (e.g. corals and sponges) that potentially presented amphilochids amphipods. The substrate consisted of debris, sediments, ascidians, sponges, and corals. Sessile fauna was enclosed in plastic bags, to avoid evasion of associated fauna, and then removed from the substratum with a hammer and chisel.

In the laboratory, samples were sorted and washed with 70% ethanol. Amphilochids were found in Desmapsamma Burton, Reference Burton1934 washes, and retained in 500 μm sieves. Mouthparts and appendages were mounted and dissected on glass slides with glycerol gel. The holotype habitus was illustrated under a stereomicroscope with camera lucida (Zeiss Discovery V.8), while the dissected appendages were photographed under a microscope with a digital camera (Zeiss AXIO Scope.A1 AX10/ Axiocam 305), microphotographs were treated with the software ZEN ZEISS 1.6 PRO. Line drawings were prepared using the software CorelDRAW 2019, following the method proposed by Coleman (2006).

Type material is deposited in the Crustacean Collection of the Museu de Historia Natural da Universidade Federal da Bahia (MHNBA - UFBA). For diagnostic characters, we used the setal classification of Garm and Watling (Reference Garm and Watling2013), whereas the nomenclature for the palms of gnathopods is based on Poore and Lowry (Reference Poore and Lowry1997). The following abbreviations are used in the figures: Hb, habitus; A1–2, antennae 1–2; Mx1–2, maxillae 1–2; Md, mandible; Mp, maxilliped; Gn1–2, gnathopods 1–2; P3–7, pereopods 3–7; Ep1–3, epimeral plates 1–3; U1–2, uropods 1–2; Ur1–3, urosomites 1–3; T, telson; r, right; l, left.

Systematic section

Suborder Amphilochidea Lowry and Myers, Reference Lowry and Myers2017
Infraorder Amphilochida Lowry and Myers, Reference Lowry and Myers2017
Parvorder Amphilochidira Lowry and Myers, Reference Lowry and Myers2017
Superfamily Amphilochoidea Lowry and Myers, Reference Lowry and Myers2017
Family Amphilochidae Boeck, 1871
Hourstonius Hoover and Bousfield, Reference Hoover P and Bousfield2001
Hourstonius karamani sp. nov.
(Figs 1–3)

Examined material

Holotype

1 male 3.5 mm, Yacht Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, associated with Desmapsamma sp., depth 2 m, 10 December 2019. UFBA 4541

Paratype

1 male 3.0 mm. Yacht Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, associated with Desmapsamma sp, depth 2 m, 10 December 2019. UFBA 4542

Etymology

The species name is in honour of Dr Gordan Karaman for his notable contributions to the taxonomy of Amphilochidae, as well as to many other amphipods taxa of the world.

Diagnosis

Antenna 1 and 2 subequal in length. Antenna 1 peduncle stout, accessory flagellum minute. Lateral cephalic lobes broad and truncated. Eyes ovoid and large. Mandibular molar well developed, mandibular palp article 3 setose, longer than article 2. Gnathopod 1 subchelate, carpus not projected towards propodus. Gnathopod 2 larger than gnathopod 2, subchelate, carpal lobe almost reaching palmar angle. Epimeral plate 3 not projected. Telson long, entire, subconical with a distally rounded margin.

Description

White animals with little dorsal light-brown spots. Head. Rostrum acute and projected, cephalic lobes truncated, not projected. Eyes subovate. Antenna 1 subequal in length to antenna 2, article 1 10% longer than rostrum, slightly shorter than article 2, article 3 reaching 50% of article 2; accessory flagellum minute; flagellum reaching 70% of peduncle length, setose, with 10 articles. Antenna 2, article 4 subrectangular, slightly longer than article 3; article 5 small with 2 setae, one of them hirsute and the other plumose; flagellum shorter than 50% of peduncle, setose, with 6 articles (Figure 1).

Figure 1. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 1 mm (Hb), A1 and A2 (0.4 mm), Mx1, Mx2, rMd, Mp (0.3 mm).

Mouthparts. Mandible molar well-developed and triturative; incisor serrate, with 10 accessory spines; lacinia mobilis serrated, laterally excavated; palp short, 3-articulated, article 1 subquadrate, reaching 50% of article 2, article 2 subrectangular, without setae, 20% wider than article 3, article 3 thin, narrowing distally, leaf-shaped, beset with several setules. Maxilla 1 palp biarticulated, article 1 subsquared, reaching 25% of article 2 length, article 2 globose, distal margin with 10 robust simple setae; outer plate as long as palp article 2, distal margin with 8 robust setae; inner plate vestigial, naked and subrounded. Maxilla 2 outer plate with distal margin truncated, beset with several simple setae; inner plate laterally and distally setose. Maxilliped palp, article 1 20% longer than article 2, outer margin with 2 setae, distal corner with small simple seta. Article 2 inner margin setose, facial margin with 3 setae, the distalmost small and stout, article 3 slightly longer than article 2, inner margin setose, outer margin with 2 simple setae; inner plate distally acute, reaching 50% of palp length, distal margin with 2 setae; inner plate subrectangular, 3.5x longer than large, distal margin with 9 small and stout setae. Upper lip and lower lip missing (Figure 1).

Pereon. Gnathopod 1, coxa 1 reduced, with posterior lobe, anteroventral corner truncated, not produced, ventral margin naked; basis subcylindrical, 40% longer than coxa 1, posteroventral margin with small seta, ischium reaching ½ of merus length, posteroventral margin with small seta, merus reaching 50% of basis length, posterior margin with robust long seta, distal margin with 3 robust ones; carpus short, reaching 40% of propodus length, posteroventral lobe not projected; propodus with long facial seta, palm transverse, covered by several setules, with set of seven long setae, dactylus as long as palm, inner margin serrate, with distal acute projection (Figure 2).

Figure 2. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 0.4 mm.

Gnathopod 2 larger than gnathopod 1, coxa 2 subovate, 2.5x longer than coxa 1, ventral margin naked; basis long subcylindrical, 15% longer than coxa 2; ischium reaching 25% of basis length; merus 10% longer than ischium, posterior margin with small stout seta, distal margin with 2 robust and long ones; carpus projected towards propodus, almost reaching propodus palm, posteroventral corner with 3 robust setae; propodus well developed, reaching 90% of basis length, palm transverse, undulated, covered by several setules, with set of 13 setae, palmar corner with 2 long robust ones; dactylus 15% longer than palm, inner margin smooth, with distal acute projection and single seta (Figure 2).

Pereopd 3, coxa 3 subrectangular, long, ventrally naked; basis subcylindrical, as long as coxa 3, posterior and anterior corners with small seta on each one; ischium reaching 15% of basis length; merus subrectangular 3× longer than ischium, anterior and posterior margins with seta on each one, anteroventral corner well projected with 2 setae, posteroventral corner less projected with single seta; carpus similar in length to merus, subrectangular, anteroventral corner with 3 small setae, posteroventral corner with 2 longer ones; propodus 30% longer than carpus, anterior margin with 2 setae, posterior margin with 4 ones; dactylus long, reaching 60% of propodus length (Figure 2). Pereopod 4, coxa 4 robust, posteriorly expanded; basis, ischium, merus, carpus, and propodus similar to that of pereopod 3 (Figure 2).

Pereopod 5 20% shorter than pereopod 6, coxa 5 lobated; basis globose, posterior margin smooth and naked, anterior margin with 3 distal small setae; ischium subsquared, anteroventral corner with setula; merus reaching 70% of basis length, posteroventral corner produced with 3 setae, posterior margin with distal one; anterior margin with 2 anterior setae, anteroventral corner with 2 longer ones; carpus slightly shorter than merus, posteroventral, and anteroventral corners with 1 and 2 setae respectively, anterior margin with 2 setae; propodus 30% longer than carpus, anterior margin with 4 setae, posterior margin with 2 ones; dactylus long reaching 60% of propodus length (Figure 3).

Figure 3. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 0.4 mm (P5-7, Ep1-3), 0.3 mm (U1-3, T).

Pereopod 6, coxa 6 lobated, basis globose, 25% longer than pereopod 5 basis, posterior margin slightly undulated, without seta, anterior margin with 5 setae, anteroventral corner with robust one; ischium small, subquadrate, anteroventral corner with 2 small setae; merus as long as carpus, anterior margin with 3 setae, anteroventral corner setose, posterior margin with 3 setae, posteroventral corner less produced than pereopod 5 merus, with 3 robust setae; carpus subrectangular, anterior margin with 3 setae, anteroventral corner with 2 longer ones, posterior margin with 2 medial small setae, posteroventral corner with 2 longer ones; propodus 35% longer than carpus, anterior margin with 5 setae, anteroventral corner with single seta, posterior margin with 4 ones, posteroventral corner projected; dactylus reaching 60% of propodus length (Figure 3).

Pereopod 7 20% longer than pereopod 6; coxa 7 subrounded; basis globose, 10% longer than pereopod 6 basis, posterior margin smooth and rounded, anterior margin with 6 setae; ischium subsquare; merus reaching 80% of basis length; posteroventral corner well projected with 3 setae, anterior margin with 2 sets of 2 setae, anteroventral corner with 2 setae; carpus similar in length to merus, anterior margin with set of 3 setae and a posterior seta, anteroventral corner with 2 long ones, posterior margin with a medial set of 2 setae, posteroventral corner with 2 ones; propodus 40% longer than carpus, setation similar to pereopod 6 propodus, except by the distal margin with 3 long setae; dactylus long, reaching 65% of propodus length (Figure 3).

Pleossome. Epimeral plates without setae; epimeral plate 1 posterior corner rounded and slightly projected; epimeral plate 2, posterior corner rounded, not projected; epimeral plate 3 posterior corner subsquare, not projected (Figure 3).

Urossome. Uropod 1 peduncle subrectangular 5× longer than wide, with 2 distal setae, 10% longer than rami; rami narrowing distally, inner ramus similar in length and shape to outer ramus, each one with 4 small and stout setae. Uropod 2 35% shorter than uropod 1, peduncle 25% shorter than outer ramus, 2.2x longer than wide, with distal stout seta; rami unequal in length, outer ramus with 5 small stout setae; inner ramus shorter, with 2 small stout setae. Uropod 3 missing. Telson conical, long, about 1.4x longer than wide (Figure 3).

Remarks

Hourstonius karamani sp. nov. is closely related to H. wakabarae from Brazil by the cephalic lobe not projected, the similar shape of gnathopod 2, with carpal lobe long and projected angle, and by the shape of pereopods 3–7 (Leite and Siqueira, Reference Leite and Siqueira2013). Nevertheless, H. karamani sp. nov. is different from H. wakabarae by the ovoid eyes (curved in H. wakabarae); Antenna 1 accessory flagellum minute not reaching the end of article 3 (long and reaching the end of article 3 in H. wakabarae); Mandible palp article 1 subsquared and article 3 beset with setules (article 1 subrectangular and article 3 naked in H. wakabarae); Gnathopod 1 carpus without projected lobe (carpus with a long projected lobe in H. wakabarae); Epimeral plate 3 not projected and subquadrate (acute and projected in H. wakabarae) (Leite and Siqueira, Reference Leite and Siqueira2013).

The absence of a projected gnathopod 1 carpal lobe resembles the congener from Tropical Atlantic Realm H. tortugae, but the new species is different by showing: eyes large and ovoid (small and rounded in H. tortugae); maxilla 2 outer lobe distal margin with several setae (with just 7 distal setae in H. tortugae); mandible palp article 3 beset with setules (naked in H. tortugae); coxa 1 distally rounded with a posterior lobe (coxa 1 tapering distally without posterior lobe in H. tortugae); epimeral pate 3 not projected (projected and upturned in H. tortugae) (Shoemaker, Reference Shoemaker1933; LeCroy, Reference LeCroy2002).

Hourstonius karamani sp. nov. is also different from its congeners in Tropical Atlantic H. laguna by showing antenna 1 peduncle stout and gnathopod 2 carpal lobe long (peduncle thin and carpal lobe short in H. laguna); H. templadoi by the gnathopod 1 carpal lobe not projected and telson distal margin subrounded (carpal lobe long and projected and telson distal margin acute in H. templadoi); H. petulans by the gnathopod 1 dactylus inner margin not serrated with a distal spine (dactylus serrated in H. petulans), and H. magdai by eyes regularly ovoid and epimeral plate 3 not projected (eyes irregularly rounded and epimeral plate 3 projected in a rounded lobe in H. magdai) (Reid, Reference Reid1951; McKinney, Reference McKinney1978; Karaman, Reference Karaman1980; Ortiz and Lalana, Reference Ortíz and Lalana1996; LeCroy, Reference LeCroy2002).

Lecroy (Reference LeCroy2002) described a morphotype called ‘Hourstonius sp. B’ from Florida, Tropical Atlantic. Nevertheless, these described specimens are different from all Hourstonius species of Atlantic by the gnathopod 1 and 2 similar in size, gnathopod 2 propodus margins subparallel, carpal lobe not projected, and propodus palm transverse. This pattern resembles H. pusilloides from California (Shoemaker, Reference Shoemaker1942; Karaman, Reference Karaman1980; Hoover and Bousfield, Reference Hoover P and Bousfield2001).

Hoover and Bousfield (Reference Hoover P and Bousfield2001) suggested the existence of an unnamed group of Gitanopsis including the species G. marionis (Stebbing, 1888), G. tai Myers, Reference Myers1985, and G. squamosa (Thompson, 1880). The authors do not describe the characteristics that support the unnamed group but argue that it is closer to Hourstonius than Gitanopsis. Gitanopsis marionis, one of the species of this group, was synonymized with Amphilochus marionis (Azman, 2009). Species of this unnamed group show a subtriangular telson with an entire tip, antenna 1 without accessory flagellum, and a broad rostrum (Myers, Reference Myers1985).

The new species shows a similar telson of G. tai but is different by having a minute accessory flagellum, wider lateral cephalic lobe, and antennae similar in length. Species of Gitanopsis complex should be analysed by a cladistics study to clarify the existence of another genus including the species G. tai and G. squamosa, the available data are not sufficient to define it as a valid genus. Nevertheless, H. karamani sp. nov. fits Hourstonius by the morphological characteristics, and additionally is found in the same biogeographic region originally proposed for the genus (Hoover and Bousfield, Reference Hoover P and Bousfield2001).

Gitanopsilis Rauschert, Reference Rauschert1994 is a monospecific genus related to Gitanopsis whose type species, G. amissio, shows maxilla 2 inner lobe as wide as outer one, gnathopods 1 and 2 with acute palm and telson subtriangular with a concave tip. The new species is different from G. amissio in the shape of gnathopods, telson, and maxilla 2 lobes shape.

Discussion

The genus Hourstonius was established by Hoover and Bousfield (Reference Hoover P and Bousfield2001), comprising species from Temperate and Warm Temperate Oceans and Tropical Atlantic species. According to the authors, Amphilochidae was classified as a basal group, a Gitanopsis and Hourstonius are closely related genera, forming a group whose centre of origin is thought to be the Arctic and posteriorly dispersed to warmer waters (Hoover and Bousfield, Reference Hoover P and Bousfield2001).

Hourstonius comprises small species living in association with a great diversity of organisms. Of the 18 described species, 25% were recorded living in algae, 30% were captured in sand or muddy bottom, and 10% were found in seagrass beds (Figure 4). Species were also found living associated with sponge, coral, associated with Aplysia eggs, plankton community, and floating objects (Barnard, Reference Barnard1979; Hirayama, Reference Hirayama1983; LeCroy, Reference LeCroy2002; Madrigal, Reference Madrigal2007).

Figure 4. Infographic of habitat and depth of Hourstonius species across the globe.

The genus is typical from shallow waters and most of the species are found in less than 10 m depth (Figure 4). Some descriptions available by the consulted bibliography do not provide a precise measure of collection depth, but according to the methods of collection described, we can conclude that species without depth data were probably found in shallow waters.

Considering the Hourstonius biogeographic distribution, most of the species were recorded from Temperate Northern Pacific, located in Korea, Japan, and the USA (California) (Shoemaker, Reference Shoemaker1933; Barnard, Reference Barnard1962; Hirayama, Reference Hirayama1983; Hirayama and Takeuchi, Reference Hirayama and Takeuchi1993; Kim et al., Reference Kim, Hendrycks and Lee2010). The second most diverse realm is Tropical Atlantic with six species (Figure 5). The species H. pusilla from False Bay, South Africa, was recorded from India, Mozambique, and Tristan da Cunha (Barnard, Reference Barnard1916; Karaman, Reference Karaman1980). Nevertheless, for this review, we consider only the type locality of species because most of these records are out-of-date. Considering the taxonomic changes that the family and the genus have undergone over time, these records can probably represent new species.

Figure 5. Infographic of Hourstonius distribution.

The most recent Hourstonius species was described one decade ago, being the Brazilian species H. wakabarae. During the middle of the ‘90s (1978–1995), nine species of the genus were described. After that, the discovery of the new Hourstonius abruptly paused (McKinney, Reference McKinney1978; Barnard, Reference Barnard1979; Hirayama, Reference Hirayama1983; Hirayama and Takeuchi, Reference Hirayama and Takeuchi1993; Ortiz and Lalana, Reference Ortíz and Lalana1996).

Hourstonius diversity is still underestimated, considering the occurrence of 3 different species from Florida, in comparison with just 2 species in South America and Africa, both continents with a larger geographic extension (Figure 5). The symbiont habit of Hourstonius requires accurate collection and sorting methods. In addition, specimens of this genus used to be smaller in comparison with other amphipods, this may contribute to the underestimated known biodiversity. As noted in other amphipod genera, the knowledge of Hourstonius biodiversity is dependent on the taxonomist's efforts in different geographic areas.

Taxonomic key of Hourstonius of the world

  1. 1. Maxilla 2 inner lobe with 3 setae………Hourstonius magdai (Reid, Reference Reid1951)

    Maxilla 2 inner lobe with more than 3 setae……… 2

  2. 2. Antenna 1 accessory flagellum present……… 3

    Antenna 1 accessory flagellum absent……… 11

  3. 3. Gnathopod 1 dactylus inner margin serrated……… 4

    Gnathopod 1 dactylus inner margin not serrated (smooth or with the distal acute process)……… 6

  4. 4. Gnathopod 1 dactylus inner margin proximally serrated……… Hourstonius geojeensis Kim, Hendrycks and Lee, Reference Kim, Hendrycks and Lee2010

    Gnathopod 1 dactylus inner margin distally serrated……… 5

  5. 5. Telson long and longer than the half of U3 peduncle……… Hourstonius vilordes (Barnard, Reference Barnard1962)

    Telson short and shorter than the half of the U3 peduncle……… Hourstonius pusilla (Barnard, Reference Barnard1916)

  6. 6. Gnathopod 1–2 dactylus shorter than propodus palm……… Hourstonius oozekii (Hirayama and Takeuchi, Reference Hirayama and Takeuchi1993)

    Gnathopod 1–2 dactylus as long as or slightly longer than propodus palm……… 7

  7. 7. Antenna 1 accessory flagellum as long as flagellum article 1 length………Hourstonius wakabarae Leite and Siqueira, Reference Leite and Siqueira2013

    Antenna 1 accessory flagellum shorter than flagellum article 1 length s……… 8

  8. 8. Mandibular palp article 3 setose……… Hourstonius karamani sp. nov.

    Mandibular palp article 3 naked……… 9

  9. 9. Mandible palp article 3 similar in length to article 2……… Hourstonius longus (Hirayama, Reference Hirayama1983)

    Mandible palp article 3 dissimilar in length to article 2……… 10

  10. 10. Mandible palp article 3 longer than article 2……… Hourstonius breviculus (Hirayama, Reference Hirayama1983)

    Mandible palp article 3 shorter than article 2……… Hourstonius robastodentes (Hirayama, Reference Hirayama1983).

  11. 11. Coxa 1 narrowing distally……… 12

    Coxa 1 not narrowing distally……… 14

  12. 12. Gnathopod 2 dactylus distally serrated……… Hourstonius pele (Barnard, Reference Barnard1970)

    Gnathopod 2 dactylus distally smooth or with a single spine……… 13

  13. 13. Coxa 1 distally acute……… Hourstonius japonica (Hirayama, Reference Hirayama1983)

    Coxa 1 distally conical……… Hourstonius laguna (McKinney, Reference McKinney1978)

  14. 14. Mandible palp short, reaching half of the mandible length……… Hourstonius templadoi (Ortiz and Lalana, Reference Ortíz and Lalana1996)

    Mandible palp long, well developed reaching more than half of mandible length……… 15

  15. 15. Coxa 1 subrounded……… Hourstonius tortugae (Shoemaker, Reference Shoemaker1942)

    Coxa 1 subrectangular or subquadrate……… 16

  16. 16. Epimeral plate 3 posteroventral corner rounded……… Hourstonius petulans (Karaman, Reference Karaman1980)

    Epimeral plate 3 posteroventral corner acute……… 17

  17. 17. Maxiliped palp article 3 with 6 distal finger-shaped processes………Hourstonius baciroa (Barnard, Reference Barnard1979)

    Maxiliped palp article 3 with 2 small distal finger-shaped processes……… Hourstonius pusilloides (Shoemaker, Reference Shoemaker1933)

Acknowledgments

The authors would like to thank Msc. Rosa Mácola (UFBA) for the identification of Porifera specimens in which the amphipods were found. This study is part of the project ‘Assessment and research of sun coral in Todos-os-Santos Bay’, a cooperation agreement between UFBA and PETROBRAS (No 5850.0107361.18.9) regulated by R, D &I investment clauses of Brazilian Agency of Petroleum, Natural Gas and Biofuels (ANP Resolution 03/2015). We are grateful to the Chico Mendes Institute for Biodiversity Conservation (ICMbio) for collecting permission (Sisbio No 15161-1).

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Figure 0

Figure 1. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 1 mm (Hb), A1 and A2 (0.4 mm), Mx1, Mx2, rMd, Mp (0.3 mm).

Figure 1

Figure 2. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 0.4 mm.

Figure 2

Figure 3. Hourstonius karamani sp. nov., Yatch Club da Bahia, Salvador City, Todos-os-Santos Bay, Bahia State, 12°59′58.4″S 38°31′50.7″W, holotype male. Scale bars: 0.4 mm (P5-7, Ep1-3), 0.3 mm (U1-3, T).

Figure 3

Figure 4. Infographic of habitat and depth of Hourstonius species across the globe.

Figure 4

Figure 5. Infographic of Hourstonius distribution.